ATMOSPHERIC EMISSIONS
FROM  HYDROCHLORIC ACID
MANUFACTURING PROCESSES
                        r*
                       •F'l
 U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
           Public Health Service
Consumer Protection and Environmental Health Service

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        ATMOSPHERIC EMISSIONS
      FROM  HYDROCHLORIC  ACID
      MANUFACTURING  PROCESSES
             Cooperative Study  Project
      Manufacturing  Chemists'  Association,  Inc.
                        and
                Public Health Service
U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
                 Public Health Service
    Consumer Protection and Environmental Health Service
        National Air Pollution Control Administration
               Durham, North Carolina
                    September 1969
      For sale by the Superintendent of Documents, U.S. Government Printing Office
                Washington, D.C. 20402 - Price 35 cents

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The AP series of reports is issued by the National Air Pollution Control Admin-
istration to report the results of scientific and engineering studies, and infor-
mation of general interest in the field of air pollution. Information reported in
this series includes coverage of NAPC A intramural activities and of cooperative
studies conducted in  conjunction with state and local agencies, research insti-
tutes, and industrial organizations. Copies of AP reports may be obtained upon
request, as supplies permit, from the Office of Technical Information and Publi-
cations, National Air Pollution Control Administration, U.S. Department of Health,
Education, and Welfare, 1033 Wade Avenue, Raleigh, North Carolina 27605.
     National Air Pollution Control Administration Publication No. AP-54
                                      ii

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                            FIGURES
  1.  Yearly production of 100 percent hydrochloric acid  ....    2
  2.  Typical by-product hydrochloric acid process (chlorobenzene)  10
  3.  Synthesis chlorine-hydrogen process   	14
  4.  Synthesis process hydrogen chloride burner   	15
  5.  Cross-sectional view of Mannheim furnace  	17
  6.  Mannheim hydrochloric acid manufacturing
     process flow diagram	18
  7.  Cross-sectional view of Laury furnace   	21
  8.  Hydrogen chloride distillation system for reagent-quality acids  23
  9.  Falling film absorber with external piping and tails tower  .  .  27
 10.  Falling film absorber with integral gas piping and tails tower  .  28
 11.  Typical adiabatic hydrochloric acid absorption
     unit flow diagram	29
A-l  Impinger gas sampling train	36
A-2  Grab sample bottle   	37
A-3  Burette for adding absorbing reagent	38
A-4  Mist sampling train   	42
C-l  Vapor pressure of hydrochloric acid at various concentrations   53
C-2  Specific gravity and density versus percent hydrogen chloride   53
C-3  Relationship of viscosities of hydrogen chloride and water  .  .  54
C-4  Heats of solution of hydrogen chloride in water   	54
C-5  Vapor-liquid equilibra for hydrochloric acid   	55
C-6  Boiling point of hydrochloric acid solution	56
C-7  Freezing point of aqueous hydrogen chloride	57
                               111

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                           TABLES
 1. Production of hydrochloric acid by process type  	1
 2. Hydrochloric acid production in United States	6
 3. Emissions from by-product hydrochloric acid
    manufacturing plants   	12
 4. Hydrogen chloride emissions from synthesis plants	16
 5. Emissions from Mannheim plants	20
C-l Specific gravities of aqueous hydrochloric acid solutions ,,.  .  .52
                               iv

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                             PREFACE
    To provide reliable information on  the nature and quantity of
 emissions to  the atmosphere  from chemical manufacturing, the
 Public  Health  Service,  United  States  Department  of  Health,
 Education,   and  Welfare,   and  the  Manufacturing  Chemists'
 Association, Inc., entered into  an agreement October 29, 1962, to
 study emissions  from selected  chemical  manufacturing processes
 and to  publish information that would be helpful to air pollution
 control  and  planning   agencies  and   to  chemical  industry
 management.* Direction of thes^ studies  is vested in an MCA-PHS
 Steering Committee, presently constituted as follows:

        Representing PHS               Representing MCA
           Stanley T. Cuffef               Willard F. Bixbyt
           Robert L. Harris, Jr.             Louis W. Roznoy
           Dario R. Monti                  Clifton R. Walbridge
           Raymond Smith                 Elmer P. Wheeler

    Information included in these reports  describes the range  of
 emissions during normal operating conditions and the performance
 of established  methods and devices employed to limit and control
 such  emissions.  Interpretation of  emission values  in- terms  of
 ground-level  concentrations  and  assessment  of potential effects
 produced by  the emissions are  both outside the scope  of this
 program.
*Reports in this series to date are Atmospheric Emissions from Sulfuric Acid Manufacturing
Processes, Public Health Service Publication No. 999-AP-13; Atmospheric Emissions from
Nitric Acid Manufacturing Processes, Public Health Service Publication No. 999-AP-27;
and Atmospheric Emissions from Thermal-Process Phosphoric Acid Manufacture, National
Air Pollution Control Administration Publication No. 48. These publications are available
from the Manufacturing Chemists' Association, Washington, D.C., and the Superintendent
of Documents, U.S. Government Printing Office, Washington, D.C. 20402.
f Principal representatives.

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                 ACKNOWLEDGMENTS
   Sincere gratitude is  extended by the project sponsors to the
many individuals and  companies who have contributed to  this
study.
   Special  thanks are  due  the  following  companies,  which
participated in the stack sampling program.
     Detrex Chemical Industries.
     Diamond Shamrock Chemical Company.
     Olin Mathieson Chemical Corporation.
     PPG Industries, Inc.
     Tennessee Corporation.
   The following companies provided technical information  and
other assistance in the preparation of this report.
     Carbon Products Division, Union Carbide Corporation.
     Falls Industries Process Equipment Division of Carborundum.
     Haveg Industries, Inc.
   Samuel  L.  Bean of Allied  Chemical  Corporation, Industrial
Chemicals Division, and Howard Wall, Jr., National Air Pollution
Control Administration, were the investigators in the study and are
the  authors  of  this  report.  The  sponsors  acknowledge  the
contribution of the Allied Chemical Corporation in providing the
services of Mr. Bean.
                             VI

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    USE AND LIMITATIONS OF THIS  REPORT
   This report is one of a series on atmospheric emissions from
chemical manufacturing processes. It provides such information on
the manufacture of hydrochloric acid.  Basic characteristics of the
industry, including growth rate, manufacturing processes, product
uses, and the number of producing plants in the United States are
discussed.  Process  descriptions are given  for  the  chlorinated
by-product process and the synthesis process, which employs the
direct combustion of hydrogen in chlorine. Mannheim, Hargreaves,
and several other processes are included for their historical interest,
even though the number of plants that  use them is decreasing
rapidly. Process information includes the range  of emissions of
hydrogen chloride from hydrochloric acid manufacturing plants and
the methods of limiting  or  controlling these emissions to the
atmosphere.  Although  other  contaminants  such as  chlorine,
chlorinated  organics, and  other hydrocarbons  emitted  to the
atmosphere  from these plants  are  mentioned and in some cases
discussed, they are not the primary concern of this report. Detailed
descriptions of  the  sampling  and analytical methods  used in
measuring such emissions are also included.
   The production of hydrochloric acid has been a basic industry in
the United States for many years; manufacturing procedures have
become well established. Plant design, throughput rates, and the use
of special systems to reduce emissions  are factors that influence
atmospheric emissions.
   Emission data contained in this  report were obtained from 18
percent of the present hydrochloric acid manufacturing locations.
Most of the data are from the records of acid producers. The data
include results of  stack  sampling programs conducted  by the
National Air Pollution Control Administration as part  of the joint
study.
   Although this report is a technical review prepared primarily for
public  officials  concerned with the control of air pollution, it is
expected that it will also be helpful to chemical plant management
and its technical staff. This report should be reviewed at intervals to
determine when  revision  is  necessary to  reflect prevailing
conditions.
                              Vll

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                      CONTENTS
SUMMARY  	1
    Manufacturing Processes  	1
    Hydrochloric Acid Production  .	2
    Typical Emissions	3
    Control of Emissions	3
    Emission Guidelines   	3
GROWTH OF HYDROCHLORIC ACID
     MANUFACTURING INDUSTRY	5
    Historical Background  	5
    Current Uses  	5
HYDROCHLORIC ACID MANUFACTURING
     PROCESSES   	9
    By-Product Hydrogen Chloride	9
    Typical Process Description—Chlorobenzene	10
    Emissions	11
    Control of Hydrogen Chloride Emissions	11
    Synthesis Process	13
      Introduction	13
      Emissions   	16
      Control of Emissions	16
    Mannheim Process  . ,-,	16
      Introduction	16
      Emissions   	19
      Control of Emissions	19
    Hargreaves Process  	,	19
      Introduction	19
      Emissions   	19
    Laury Process	21
      Introduction	21
      Emissions   	21
ANHYDROUS HYDROGEN CHLORIDE	23
    Introduction  	23
    Emissions	24
                            IX

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REAGENT-GRADE HYDROCHLORIC ACID
     MANUFACTURE	25
    Emissions	25
    Air Blowing	25
    Hydrogen Chloride Absorption Systems  	26
      Falling Film Absorber	26
      Adiabatic Absorber  	26
      Emissions From Absorber Systems	26
      Control of Emissions	29
DEFINITIONS	31
APPENDIX A: SAMPLING AND
     ANALYTICAL TECHNIQUES  	34
    Determination of Hydrogen Chloride and
      Chlorine in Stack Gas	34
    Acid Mist Sampling	41
    Determination of Sulfates and Sulfuric Acid	43
APPENDIX B: HYDROCHLORIC ACID
     MANUFACTURING ESTABLISHMENTS
     LOCATED IN UNITED STATES	45
APPENDIX C: PHYSICAL DATA-
     HYDROCHLORIC ACID	51
REFERENCES	5§

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           ATMOSPHERIC  EMISSIONS
        FROM HYDROCHLORIC ACID
       MANUFACTURING PROCESSES
                        SUMMARY

MANUFACTURING PROCESSES
  Approximately 80 percent of the hydrochloric acid in the United States is
manufactured as a by-product of the chlorination of organic compounds.
By-product hydrogen chloride is produced in the manufacture of chlorinated
benzene, vinyl chloride, chlorinated methane, chlorinated ethylene, toluene
diisocyanate, and other such compounds.
  The  second most important source of hydrochloric acid is the synthesis
process in which hydrogen is reacted with chlorine. This process produces a
relatively pure hydrogen chloride, which may  be converted to hydrochloric
acid or recovered as anhydrous hydrogen chloride.
  Less than 10 percent of the hydrogen chloride manufactured in the United
States is produced by a reaction of sulfuric  acid on metal chlorides, the
principal one of which is sodium chloride. Table 1 illustrates the decline in
importance of the salt process and the increased importance of by-product
hydrogen chloride sources.
          Table 1. PRODUCTION OF HYDROCHLORIC ACID
                       BY PROCESS TYPE
                        (percent of total)1
Year
1935
1947
1958
1961
1962
1966
1967
Salt
reaction
86
53
13
10
9
9
8.5
Synthesis
14
4
18
13
14
7
7
By-product
	
43
69
77
77
84
84.5
  Hydrogen chloride is often processed into hydrochloric acid in package
plants that consist of a falling film absorber and a packed tower. If the unit is

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used to make acid from a by-product process, the organic materials are usually
removed from the hydrogen chloride by condensation or absorption before the
hydrogen chloride is absorbed in water.
   If the organic content of the acid is objectionable, another kind of package
plant, which consists of an adiabatic unit in which the acid is formed at its
boiling point in a packed column, may be used. In this case, organic materials
with low boiling points are not allowed to condense. The acid is then cooled
and passed through a carbon bed to remove the final traces of organic material
   Regardless  of  the type of hydrogen chloride absorber  used to form
hydrochloric acid, the most efficient system,  from an atmospheric emission
viewpoint,  is characterized by a final scrubber that removes any remaining
trace of hydrogen chloride from the system.

HYDROCHLORIC ACID PRODUCTION
   In  1965 a total of 1,318,122 tons of hydrochloric acid was produced in the
United States.1  Based on the increase in production between 1945 and 1965,
the growth rate is 40,000 tons per year,  as shown in Figure 1.
         1,300
         1,200 —
                1930   1935   1940   1949   19»   1955   I960  1965   1970
   Figure 1.  Yearly production of 100 percent hydrochloric acid.
                                    HYDROCHLORIC ACID EMISSIONS

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TYPICAL EMISSIONS
   The  atmospheric  contaminants  emitted  from  the  manufacture  of
hydrochloric  acid  are  hydrogen  chloride,  chlorine,  chlorinated  organic
compounds, and  other  organic materials. The exact type and  quantity of
contaminants vary with  the process and the type of tail gas control system
used.
   The  concentration of hydrogen chloride  emitted to the  atmosphere is
usually less than 0.5 percent of the tail gas volume emitted to the  atmosphere.
The  average tail  gas  volume  emitted  to the atmosphere from the plants
reviewed for this report is 40 cubic feet per minute, with the rates ranging from
2 to 550 cubic feet per minute.
   On  a combined basis,  the tables herein show  that 6 of  the 26 plants
reporting were emitting hydrogen chloride above the 0.5 percent level. One of
the six  plants was permanently shut  down  after  testing. Another was in the
process  of installing a new scrubber to reduce emissions to the  0.5  percent
level.  Another dispersed its gases by diluting them with stack gases from a
boiler.

CONTROL OF  EMISSIONS
   Emissions from hydrochloric acid plants are adversely affected by (1) high
temperatures in the absorption system, (2) improper balance of absorption area
and contact time, (3) faulty equipment, and (4) inadequate tail gas scrubbing
systems. Emissions of hydrogen chloride or  hydrochloric  acid  can  also be
caused by  operational upsets.
   The most common method used to remove hydrogen chloride  from tail gas
is  to  scrub the gas with water. This method is inexpensive  and effective.
Alkaline scrubbing is sometimes used when other compounds that  are not
readily absorbed in water, such as chlorine or phosgene, are present.
   Emissions of organic and chlorinated organic compounds, which come from
sources  other  than  the   direct  manufacture   of hydrogen  chloride  or
hydrochloric acid, vary  considerably and present  a different problem in each
case. Reduction of emissions of these compounds may requke a more efficient
organic  absorption system, a phosgene breaker, a benzol absorption system, or
some  other  system especially  suited  to  remove a  particular  emission.
Efficiencies of these control systems often exceed 99 percent.
   In  some cases,  emissions to the atmosphere are prevented by utilizing a
closed system for the entire organic and hydrogen chloride plant.

EMISSION GUIDELINES
   Hydrogen chloride emissions to  the atmosphere! usually total less than 0.5
percent of the tail gas volume. This is a relatively  small quantity  of hydrogen
chloride because gas volumes  for plants reporting range from 2 to 550 cubic
feet per minute with an average of 40 cubic feet per minute.
   Adequate control equipment is available to prevent emissions of more than
0.5 percent hydrogen chloride, or about 0.5 pound per ton of acid produced.
   In  the  event of an emergency shutdown of a hydrochloric acid plant, the
hydrogen  chloride gas  source should  be shut  down first. Liquid flow to
absorption equipment should  be maintained at a level sufficient to keep all
Summary

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tubes and/or packing wetted and thus prevent hydrogen chloride emissions to
the atmosphere. Some weak acid will be made during this shutdown period,
but it can usually  be adjusted by producing somewhat highei-than-normal-
strength material later. This technique of maintaining at all times more liquid
flow than the amount required for surface wetting should also be used to
prevent hydrogen chloride emissions during routine shutdowns and startups.
                                  HYDROCHLORIC ACID EMISSIONS

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        GROWTH OF  HYDROCHLORIC  ACID
             MANUFACTURING  INDUSTRY

HISTORICAL BACKGROUND
   Hydrochloric acid, which is also called muriatic acid, was first described by
Valentius in the Fifteenth Century and was studied by such eminent chemists
as Thenard, Cavendish, Priestly, and  Gay-Lussac.2 The  first large-scale
production of hydrogen chloride began as a by-product in the LeBlanc soda
ash process wherein salt and sulfuric  acid are reacted to produce salt cake.
Originally this hydrogen chloride gas was vented to the atmosphere; however,
since  this  indiscriminate  discharge   killed  vegetation,  over  a  large  area
surrounding the manufacturing  plants,  legislation was soon introduced  in
England to prohibit it This restriction initiated the expedient of dissolving the
hydrogen  chloride  in  water,  which  forms hydrochloric acid.  Soon  uses
were  discovered for the acid,  and subsequently plants were built  for its
manufacture as the primary  product with salt cake as a by-product. Demand
for salt cake was reduced as the Solvay process  replaced the LeBlanc process
for making soda ash.
   In the United States, the reaction of sulfuric acid and salt,  an initial step in
the LeBlanc process, was used to manufacture hydrochloric acid  rather than
soda ash as the prime product. The heating of salt and sulfuric acid to form
hydrogen  chloride  gas  is also  the principal operation of the Laury and the
Mannheim  processes. The Hargreaves process, which involves reaction of salt
and sulfur dioxide, is used in only two plants in the United States; and like the
Mannheim process, it is costly and its use probably will be discontinued soon.
   As can be seen in Table 1, originally, most hydrochloric acid was produced
from the reaction of salt and sulfuric acid. As the  chemical industry grew, more
acid  was produced through by-product methods  and more acid was produced
by burning hydrogen in chlorine than was produced from the reaction of salt
and sulfuric acid. At the present time, the by-product process is the largest
source of acid; burning of hydrogen in chloririe (synthesis process), the second
largest source;  and salt   sulfuric acid and other processes, the third largest
source of acid.  Table 2 and Figure 1 show the growth  trends of this industry.
CURRENT USES                             i
   Because a large portion of the total hydrochloric acid produced is derived
from by-product  operations,  the  locations of  production  do not  always
coincide with the areas of use. Shipping costs for acid are high because about
70 percent by weight of the usual commercial-strength acid is water. Unusual
regional supply-and-demand  situations result. In some localities a Mannheim
furnace, which is usually costly to operate, can be run at a profit to produce
acid for local needs. At other locations (along the east coast of the  United
States in particular) by-product acid is often in oversupply and is dumped into
the ocean. Some manufacturers ship hydrogen chloride in its anhydrous liquid

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form to reduce transportation costs and to enable them to compete in markets
far from the source of production.


  Table 2. HYDROCHLORIC ACID PRODUCTION IN UNITED STATES1
Year
1933
1935
1937
1939
1941
1943
1945
1947
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966 (preliminary)
1967 (preliminary)
Tons HCI produced
100% basis
63,000-
87,000
122,000
140,000
228,000
342,000
408,000
442,558
484,000
618,784
693,541
683,742
771,241
740,604
838,249
911,430
917,081
848,487
955,914
970,167
910,967
1,052,116
1,079,443
1,228,068
1,368,122
1,505,000
1,597,000
   Hydrochloric acid is used for pickling steel, for producing glucose from corn
and other  starches,  making  and  purifying  bone  char, bleaching sugar,
chlorinating chemical compounds, chlorinating rubber, activating petroleum
wells, and processing food and drugs.
   Less well known uses include the manufacture of alkyl chloride used in
making tetraethyl lead; preparation of chlorides from alcohols; preparation of
pharmaceutical-grade  chemicals  such  as  adipic  acid,  citric acid,  amine
hydrochlorides, and aconitic acid; dehairing of skins in tanning; and production
of silica gel Hydrochloric acid is also used as a catalyst in organic reactions. I
   Several recently built vinyl chloride plants both make and use hydrochloric
                                    HYDROCHLORIC ACID EMISSIONS

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acid.3-4 Part of such a plant manufactures vinyl chloride with chlorine, wmcn
yields  the  by-product hydrochloric  acid. The  other  part  of  this  plant
manufactures vinyl chloride utilizing the by-product hydrogen chloride. Such a
plant can be designed and operated so that no excess acid is produced.
Growth of Industry

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     HYDROCHLORIC ACID  MANUFACTURING
                           PROCESSES
BY-PRODUCT HYDROGEN CHLORIDE
  By-product hydrogen  chloride, which results  from the chlorination  of
organic  compounds,  constitutes the  largest  source  of hydrochloric acid.
Numerous reactions will form hydrogen chloride. Most of these reactions take
place  when  chlorine  is  added  to  an organic compound.  If a chlorinated
hydrocarbon is  hydrolized with water, hydrogen chloride is  produced. An
example of a process that generates hydrochloric acid as a by-product is the
direct chlorination of benzene. The equation for the chlorination of benzene
is:

                  eerie *• ci2. - »• c6risci  + HCI

  This reaction takes place in the presence of a chlorine carrier, such as ferric
chloride.2  The yield is about 70 percent. In  addition to the conversion of
benzene to  benzene  monochloride, some benzene dichlorides are  formed
according to the reaction:

                C6H5C1 +  C12 - > CetttClj + HCI

Benzene  dichloride  concentration   can  be   increased  by  allowing  the
monochloride to remain in  the reactor for  a longer period of time than
required for its  production.  The ratio of paradichlorobenzene  formed to
orthodichlorobenzene is generally fixed, but trace additives can be used in the
chlorine to vary this ratio.
  Chlorobenzenes are  used as intermediates for synthesizing various organic
compounds,  solvents  and preservatives  for paints, moth balls,  fumigants,
germicides, and deodorants.2
  Hydrogen chloride is  formed also by regeneration  in some chlorination
processes. For example, the chlorination of benzene and subsequent hydrolysis
to phenol occur according to the following reactions:

                     2HC1 +  03   - > 2C6HsCl + 2H20

                          H2O - > C6H5OH +  HCI
In such reactions, the chlorination and hydrolysis take place in separate steps
and the acid is separated, purified, and sent back to the chlorination process.
   Other processes that produce hydrogen chloride include the chlorination of
methane, the chlorination of paraffin, and the formation of intermediates for
urethane foams.

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TYPICAL PROCESS DESCRIPTION - CiSLOROBENZENE
   The raw materials required for making chloroben/.cne are ben/.cne, chlorine,
hydrogen, air, and some (race catalysts for special reactions.
   Benzene used is cither  moisture  free or is dried with sodium hydroxide
before being introduced  into the reaction. The chlorine  is also moisture free.
Before chlorine is introduced to the ben/.enc, 1 to 3 percent hydrogen is added
along with sufficient air  to reduce the chlorine concentration to between 80
and 85 percent. As shown in Figure 2, the benzene and chlorine streams are fed
into tanks  containing iron rods. These rods act as a chlorine carrier by forming
ferric chloride. Because the reaction is exothermic, a portion of the chlorinated
benzene mixture  is cooled  in a heat  exchanger  and returned to  the reactor.
Cooling controls the rale of reaction.
           FRESH WATER IN
HYDROGEN CHLORIDE GAS IN
                                                              EXHAUST
                                                                GASES
                     CHILLED MONOCHLOROBENZENE
                          HYDROGEN CHLORIDE GAS
                                     NTOWER.  [ssnrl
                                           1——I  IN i  —I  '  h
                                     NZENE—•»       •—     •—I
                              IOCHLOROBENZENE
                                                        t
                                                              FALLING FILM
                                                              ABSORBER
                                                        COOLING WATER OUT
                                                        PRODUCT ACID
 BENZENE
  »TER-H  I
  IATER -t4_  \	" BEN.
                                                     iZENE TO STORAGE
                                                       MONOCHLOROBCNZENE
                                                       PARADICHLOROBENZENE
                                                       ORTHODICHLOROBENZENE
                          STORAGE
 Figure  2.  Typical by-product hydrochloric acid process (chloro-
            benzene).
   The liquid components of the reaction are clJorobenzenes and benzene. The
gases from the reactor consist of hydrogen chloride, ben/enc, chlorobenzenes,
and air.
   Product liquid is neutrali/cd with sodium hydroxide and separated into
constituents by  fractionation. Any separated benzene is  returned as process
feed.   Gases   leaving  the  reactor  are   processed   to  recover   ben/.cne,
chlorobenzenes, and hydrogen chloride gas. These gases arc first scrubbed in a
10
HYDROCHLORIC ACID EMISSIONS

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packed  tower  with  a  chilled  mixture   of  monochlorobenzcne  and
dichlorobenzene to condense and recover any benzene or chlorobenzene. The
hydrogen  chloride is then absorbed in a falling film absorption  plant as
described  in the section on absorption systems. The chlorobenzene scrubbing
liquid is recycled to the main reaction vessel.

EMISSIONS
   Hydrogen  chloride  emission  data, in addition to data on  other trace
emissions  from by-product plants, are presented in Table 3. Most of the plants
contacted  by questionnaire  (^Plants Number  1 through 17) indicated no
emissions  of hydrogen chloride. However, further investigation indicated that a
value of 0.5 percent hydrogen chloride by volume in the exit gas is considered
by most plants to be negligible and is therefore reported as zero. Two of the
four plants tested by the PHS sampling team (Plants Number 18 through 21),
however, showed results somewhat higher than the reporting plants. To ensure
more accurate results, greater effort was expended by the sampling team in
making these tests than would normally be used in making routine analyses.
   Concentration of hydrogen chloride in the emissions  to the atmosphere
range from 0  to 50.6 percent by volume. Because of the diverse methods of
production, no  correlation  exists between  exit gas volumes  and  plant
productiori~Yates. However, smaller volumes of exit gas usually show greater
hydrogen  chloride concentrations. This variation in concentration in exit gas is
partly due to the varying amounts of inert materials in this gas stream. For this
reason the amount of hydrogen  chloride emitted in pounds per ton of acid
produced  gives a more accurate picture of the  contaminant emissions. On this
basis  emissions range from 0 to  8.5 pounds of hydrogen chloride per ton of
actual acid produced.
   In plant BP-19, where the 8.5 value was recorded, the hydrogen chloride
was emitted during a period of about 30 minutes of a 4-hour test period. This
particular plant  was arranged so that two separate  chlorination units were
connected to  one acid plant. In this test one unit was turned on too rapidly
and hydrogen chloride was blown  out of the absorption plant until the unit
could be stabilized. This represents  an example of improper operation because
this unit  could  have been turned  on gradually and the  hydrogen chloride
emitted to the atmosphere would have remained in the range of 0.16 to 0.24
pound per ton as it was in the two 1 -hour tests that followed.
   Plant BP-21 emitted about 2.6 pounds of hydrogen chloride per ton of acid
produced.  This plant was not equipped with a final scrubber, a fact which
partially accounts for the higher hydrogen chloride emission rate. However,
mixing  this gas with the exhaust gases from a 1,0,00,000-Btu-per-hour boiler
dilutes the emissions to the atmosphere.
   A  hydrogen chloride emission concentration of 0.5 percent at an exit gas
flow rate  of 40 cubic feet per minute will result in an emission rate  of about
1.2 pounds of hydrogen chloride per hour.

CONTROL OF HYDROGEN CHLORIDE EMISSIONS
   Tail gas concentrations of contaminants emitted from a typical by-product
plant are  often reduced by scrubbing in a packed tower located behind the
Acid Manufacturing Processes                                       11

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                  Table 3.  EMISSIONS FROM BY-PRODUCT HYDROCHLORIC ACID MANUFACTURING PLANTS
Plant
number
BP-1

BP-2
BP-3
BP-4
BP-5

BP-e
BP-7
BP-8

BP-9

BP-10
BP-11
BP-12

BP-13
BP-14

BP-1S
BP-16
BP-17
BP-18b

BP-19b


BP-200


BP-21b


Plant
capacity,
tons per day
115

40
30
15
220

70
16
7

76

12
26
30

30
105

141.5
17.8
8.3
90

60


140


226


Add
concentration.
'Be"
20

20
20
20
20
22
20
22
22

20

20
20
20

20
22

22
22
20
20

20


20


20


Exit gai eondltloni
Volume,
cfm
200

0
0
NA
2

180
NA
0

270

NA
0.01
Leakage
only
10
315°

138°
NA
0.1-3.5
520

187


187


8.3


Temperature,
°F
180

60
NA
NA
100

50
NA
85

104

NA
60
85

100
70

70
70
108
75

57


40


50


Percent
HCI«
0

NA
NA
NA
0

0
0
0

NA

NA
0.01
NA

3
0

0
0
0
<0.001

0.024
0.160
1.95
0.0023
0.0019
0.0745
50.6
47.2
53.9
Control
equipment
Water jets on
storage tanks
Water scrubber
None
Caustic scrubber
None

None
None
Water scrubber
backup
Phosgene decom-
position towers
None
None
Fume jet

None
Closed system

Closed system
None
Na3CO3 scrubber
Caustic scrubber

Water scrubber


Water scrubber


None for HCI,
CCU scrubber
for chlorine
Substances other
than HCI entering
atmosphere
Air, hydrogen, carbon
monoxide and dioxide
Trace inerts
NA
NA
Air, carbon dioxide

Air, benzol
None
None

Nitrogen and Phosgene

NA
Water vapor
Chlorine

Air, organic*
Methane, nitrogen,
RCI
Chlorine, R Cl
Inerts
Chlorine
Nitrogen, traces of
eromatics
NA


Organics


Chlorine,
carbon dioxide

Pounds HCI emitted
per ton of 20° Be'
«cid produced11
None

Nora
None
None
None

None
None
None

None

None
None
None

1
None

None
None
None
<0.008

0.10
0.70
8.5
0.0044
0.0037
0.14
2.6

2.5
NA not available.
•Represents 0.6 percent HCI or leu.
"Temd by PHS sempKn»t»eni.
eRecycled-c1osed system.

-------
final process tower. Venturi scrubbers are also used occasionally. If hydrogen
chloride is the only component to be removed, water is universally used as the
scrubbing agent. As shown in  Table 3, water scrubbers can reduce hydrogen
chloride concentration to less than 0.1 pound of HC1 emitted per ton of acid
produced. Alkaline scrubbing is sometimes employed when the gases contain
substances like chlorine or phosgene, which are not readily absorbed in water.
   Removal  of organic materials from exhaust gases poses a separate design
problem for each specific compound. If phosgene is present, a decomposition
system is needed. If benzene or phenol is present, scrubbing with a solvent is
necessary. In some cases use of the proper scrubbing solution will  efficiently
remove all of the organic compounds present.
   Some  plants  use a completely closed system  from  which there  is  no
continuous emission of exhaust gases to the atmosphere.
   By-product hydrogen chloride plants, by their nature, are adjuncts to other
processes; therefore, they may be affected by upsets that occur in the process
in which  the  hydrogen  chloride is evolved. Good controls  and  secondary
scrubbing systems can reduce  the possibility of increasing emissions resulting
from such upsets.

SYNTHESIS PROCESS

Introduction
   High-purity concentrated hydrogen chloride may be synthesized by burning
hydrogen in chlorine, as shown in Figures 3 and 4. High purity is desirable for
organic compound or drug synthesis and in the manufacture of reagent-grade
acid.
   Hydrogen chloride is made in accordance with the equation:

                        H2  + C12 	> 2 HC1

   The source of chlorine is usually chlorine cell gas, although waste chlorine
(blow gas) can be used. Hydrogen can come from any source of relatively pure
hydrogen, but usually it is from the electrolysis of brine or steam reforming of
a relatively pure organic compound.
   The.purity of the raw  materials  determines the purity of the product.
Chlorine  usually contains some organic materials and oxygen in addition to
water that can result in water vapor within the combustion chamber. Hydrogen
may also contain water vapor and organic compounds. The net result of water
vapor in the feed gases is that  it can condense in the'combustion chamber and
form hydrochloric acid. This  may cause corrosion unless impervious graphite
materials are used in the combustion chamber.
   A typical product will  contain 0.5 percent  hydrogen, 0.1 percent water
vapor,  0.1  to  1.5  percent inerts, and  the balance hydrogen chloride.  In
addition, some carbon dioxide may be present.
   A slight  excess of hydrogen  is used in this process, and this assures a
chlorine-free product. Combustion takes  place in a closed chamber under a
slight  positive or slight  negative pressure, depending  on chamber  type. A
burner, shown in Figure  4, injects the chlorine into a surrounding hydrogen
Acid Manufacturing Processes                                       13

-------
                     WASHER AND
                     MIST ELIMINATOR
a

§
o
o
93
hH
O

>
O

8
K)
I
                                                         BURNER CHAMBER


                                                                  PRODUCT GASES (HCI, Hj, AND WATER VAPOR)
             HYDROGEN-*-
CHLORINE
                                                                                                  PRODUCT ACID
                              Figure 3.  Synthesis chlorine-hydrogen process.

-------
 stream. The original ignition is initiated by using a retractable air-hydrogen
 torch or an electrical ignition device.
       COOLING WATER IN
                                EXPLOSION DOOR
                               COMBUSTION
                                                 HYDROGEN CHLORIDE
        COOLING WATER OUT -<
«*• CHAMBER '
I
BURNER-*-
P



ISIGHT GLASS

^-••HYDROGEN
4
CHLORINE
       Figure 4.  Synthesis process hydrogen-chloride burner.

   Synthesis plants differ in detail because of differences in raw material sources
and qualities, and plant  capacity. However, all plants  consist  of a  chlorine
burner, including control  and safety devices, and acid purifying and absorption
facilities. Burners may be  steel with a silica or brick lining, water-jacketed steel,
or water-cooled graphite. Brick burners are commonly used, especially  for large
units, but they have the disadvantage of a high product temperature, i.e., about
2,200° F. Water-jacketed steel is good if  the temperature  of the jacket is
maintained above the dew point of the materials within the burner. The outlet
temperature from a water-cooled burner is within a range of 700° to 1,000° F.
   A burner consists of one or more nozzles, which inject the gases  into the
combustion chamber, and can have a  range  of capacity of 8 to 16 tons of
hydrogen chloride per day. Control of  the  gas burner may  be manual or
automatic. The trend presently is toward automatic operation.
   Controls include safety devices and purge systems. Burner chambers have an
explosion rupture disc to protect the vessel and surrounding area. The  inlet gas
lines are provided with automatic shutoff valves and seals to prevent back flow
of reactants due to reports.  An ignition  device is  sometimes included in the
outlet duct to prevent the delivery of an explosive  mixture of gases instead of
hydrogen chloride. Other control  and safety devices include  flame  sensors;
temperature-regulated controls for various purposes; and a purge system, which
usually  injects carbon dioxide, that  operates  automatically  in case  of an
interruption in any of the  services.
   The hydrogen chloride formed in the  combustion chamber is cooled  and
absorbed in a hydrochloric acid absorption plant as described  in the section on
absorption systems.
Acid Manufacturing Processes
15

-------
 Emissions
   As shown in Table 4, almost no hydrogen chloride is emitted from synthesis
 plants.  Chlorine is eliminated by combusting it with excess hydrogen. In the
 plants surveyed, no additional air pollution control equipment is used after the
 tails  tower.  The data in Table 4 were  obtained from  operating plants in
 response to questionnaires.

    Table 4. HYDROGEN CHLORIDE EMISSIONS FROfiiSYNTHESIS PLANTS


Plant
number
S-1
S-2
S-3

Plant
capacity,8
tons per day
33
100
32.5

Acid
concentration.
"Be
20
22
20

Exitc
Volume,
ufm
85
NA
130
las conditions
Temperature,
°F
NA
70
80


Percent
HCI
<0.01
0
Trace
Pounds HCI
emitted per
ton of 20° Be
acid produced
<0.035
None
Trace
  a20" 6^(31.5 percent) HCI.

  NA = not available.
   During  startup and shutdown the possibility exists that chlorine and
 hydrogen chloride may be released into the air. Normally, an inert purge system
 is a part of the control system  and any chlorine,  hydrogen, or hydrogen
 chloride present in the system is purged through the absorber-cooler and tails
 tower before a shutdown.
   In the event  of an emergency  shutdown of a hydrochloric acid plant, the
 hydrogen chloride gas source  should be  shut  down  first. Liquid  flow  to
 absorption equipment should be maintained at a level  sufficient  to keep  all
 tubes and/or packing wetted and thus prevent hydrogen chloride emissions to
 the atmosphere. Some weak acid  wfll be made during  this shutdown  period,
 but  this can  usually be  adjusted by  producing  material  of somewhat
 higher-than-normal strength later.  This technique of maintaining  at all times
 the flow of more liquid than is required for surface wetting should also be used
 to prevent hydrogen chloride emissions during routine shutdowns and startups.

 Control of Emissions
   The  design,  operation, and maintenance of synthesis plants result in no
 significant emissions of hydrogen chloride, as shown in Table 4.

 MANNHEIM PROCESS

 Introduction
   The Mannheim process is the principal process used to  produce hydrochloric
 acid from salt and sulfuric acid. It also produces salt cake, Na2SO4, which is
 used in glass and paper manufacturing. The chemical reactions for the salt and
 sulfuric acid process are:
                 NaCl + H2SO4
   NaHSO4 + HC1
16
HYDROCHLORIC ACID EMISSIONS

-------
                 NaCl + NaHS04
 Na2SO4 +  HC1
                 2NaCl + H2S04
Na2S04  + 2HC1
 Salt and an excess of sulfuric acid are fed into the top center of a Mannheim
 furnace, as shown in Figure 5, where the mixture is heated to about 1,000° F.
 This feed is constantly mixed and moved toward the outside of the furnace by
 plows until it is discharged through an opening into a pan or conveyor.
                               SALT.  /SULFURIC ACID
       OIL
ROTATING ARMS
WITH PLOWS
         1300° F.
      COMBUSTION
     GASES TO STACK
                                                -SILICON CARBIDE ARCH
                                                          1000° F. GASES TO
                                                            ABSORPTION
                                                             SYSTEM
                                                         1000° F.
                                                         SALT CAKE
                    PAN WITH HEARTH

       Figure 5.  Cross-sectional view of Mannheim furnace.

   Hot gases containing 30 to  60 percent hydrogen chloride in air go to the
 falling film absorber where the hydrogen chloride is cooled and absorbed.
   Gases from the furnace contain sulfuric acid vapor that condenses to a mist
 when the gases  are cooled. This mist is partially absorbed together with the
 hydrogen chloride and becomes an impurity in.the hydrochloric acid.
   Although the several types of Mannheim furnaces in use differ somewhat in
 detail, they all consist essentially of stationary circular muffles made up of a
 pan and a domed cover (Figure 6). Size of the pans ranges from 11 to 18 feet
 in diameter, and construction is of cast iron or refractory. The dome is cast
 iron or silicon carbide. Agitation of the reaction  mass is accomplished by
 rotating  arms that have plows mounted on a centrally located under-driven
 shaft. A firebrick enclosure provides  insulation and directs combustion gases
 over the cover. Mannheim furnaces generally have salt cake capacities ranging
 from 6 to 24 tons per day.                         ,
   A gas duct, a cyclone, and a gas cooler are usually considered a part of the
 furnace installation. The gas ducting allows the gases to cool somewhat before
 entering the cyclone. The cyclone removes the salt cake that is carried out with
 the gases, and the cooler cools the gases before absorption. A careful choice of
 construction materials is required. Heat resistance is of primary concern ahead
 of the cooler, and corrosion resistance is of importance downstream of the
 cooler where sulfuric and hydrochloric acids have condensed.
Acid Manufacturing Processes
                            17

-------
oo
a
•<
O
ffi
r
i
o
>
o
3
ts
                      SULFURIC ACID

          CHLORIDE SALT (KCI OR NaCI)
COMBUSTION
 GASES TO
  STACK
                                                          CYCLONE

                                   ROTATING ARMS  pRQDUCT GAS   /
                                                          COOLER.
                                                          ABSORBER
     TAILS TOWER
                                                                                                  TAIL GAS
                                                                                                  TO ATMOSPHERE
                              MANNHEIM
                               FURNACE
                                  SALT CAKE
                                    TO
                                  COOLING
                                  STORAGE
                                  AND GRINDING
                                                           COOLING
                                                            WATER-
                                                 COOLING
                                                  WATER*
2=0-
LEAN
                                                                                               PROCESS WATER
 GAS
                                                                                              STORAGE
                                                                          PRODUCT ACID
                           Figure 6.  Mannheim hydrochloric acid manufacturing process flow
                                     diagram.

-------
Emissions
   In addition to hydrogen chloride gas, both sulfuric and hydrochloric acid
mists are emitted from Mannheim process plants. Data in Table 5 show that in
general, emissions from such plants are higher than those from by-product or
synthesis process plants. Data reported by manufacturers and  collected by
actual test showed hydrogen chloride emissions of 1.3 to 3.8 pounds per ton of
acid produced. These emissions are probably higher because of poor operation
and maintenance and in some cases poor design of absorption systems.
   Particulate emissions also occur from the salt cake as it is discharged,
pulverized, and handled.
   During startup and shutdown, emissions will not occur when the exhaust fan
is on, and the hydrogen chloride gas and fumes are  sucked through the furnace
to the absorber. Liquid flow in the absorber must be maintained.

Control of Emissions
   Three basic methods of controlling atmospheric emissions exist. They are
proper  operation, an  efficient  emissions collecting  system, and effective
maintenance. Proper operation assumes good design, and results  in maximum
product recovery, thus reducing the possibility of hydrogen chloride emissions.
An adiabatic wet-scrubbing tower that utilizes hydrochloric acid has been used
with good results both to scrub and to cool the furnace gas.
   To reduce atmospheric emissions, a scrubber system can be installed on the
tails tower exhaust. Scrubbers presently in use for this purpose include venturi
scrubbers and packed water scrubbing towers.
   The  few  remaining Mannheim plants  in this country are gradually being
retired from service because of their high cost of operation and maintenance.

HARGREAVES PROCESS

Introduction
   The Hargreaves process was developed in England, and after about 1850 it
appeared as if it might become an important source of hydrochloric acid and
salt cake. However, new processes were introduced and its use declined. Only
one plant of this type is in operation in the United States.
   In this process, hydrochloric  acid is formed  by the reaction of sulfur
dioxide, steam (water), air (oxygen), and salt at temperatures of about 800  to
1,000° F. The formulas for the reaction are:

                          S + O2	> SO2

        2S02  +  4NaCl + 2H20 + O2	* 2Na2S04 + 4HC1

The  reaction is  exothermic  and will  maintain itself once the  reactants are
heated to the proper starting temperature.

Emissions
   The potential emissions from the  Hargreaves process are unreacted sulfur
dioxide, hydrogen chloride,  and salt dust.  Dusts are  removed initially by
Acid Manufacturing Processes                                       19

-------
                                          Table 5. EMISSIONS FROM MANNHEIM PLANTS

Plant
number
M-1
M-2b


Plant
capacity,8
tons per day
79
* 10


Acid
concentration,
°Be
20
20


Exit gas conditions
Volume,
cfm
440
168


Temperature,
°F
150
95



Percent
HCI
0.46
0.16; 0.18
0.06; 0.14


Control
equipment
None
Water scrubber


Substances other
Than HCI present
in exit gas
H2SO4, 30ppm
H2S04 and S02 0-160 ppm


Pounds HCI emitted
per ton of 20° Be
acid produced
3.0
Gas 3.5, 3.9
1.3,3.1
Mist 0.04-0.065
8

£


8
Q



§

H
I
CO
         a20° Be" (31.5%) HCI.




         bTested by MCA-PHS.

-------
 cleaning the product gas with a cyclone. During periods of operational upsets
 or additions of new salt, hydrogen chloride or sulfur dioxide can be emitted to
 the air. Since the reaction occurs at 1,000° F, it  is desirable to interrupt the
 process as little  as possible, thereby preventing  loss of heat and  excessive
 emissions.

 LAURY PROCESS

 Introduction
   In the Laury process, hydrochloric acid is produced in a rotary furnace from
 the reaction of sodium chloride and sulfuric acid.
   The equations are:
                  NaCl + H,S04
                 Nad  + NaHSO4
NaHSO4
          HC1
Na2SO4  + HC1
   A Laury furnace consists of an oil-fired combustion chamber that discharges
 into a horizontal revolving drum containing a roasting section and a grinding
 section (See Figure  7). Materials are charged at the end opposite the heating
 source. As they move counter-current to the flow of hot gases, they are mixed,
 ground, and roasted. The  flue gases and hydrogen chloride from the roasting
 processes are exhausted at the same end of the drum in which  the sodium
 chloride and sulfuric acid are charged. The hydrogen chloride gas and flue gas
 from the furnace are exhausted first through either a settling chamber or a
 cyclone to collect the dust, and then are sent to the hydrochloric acid absorber
 section of the plant.
                                        TO STACK

                                           t
     SALT AND                  FH   HOT SECTION
     NITRE CAKE   GRINDING CHAMBER    [ 11        —
                            SALT CAKE TO COHVI
          Figure 7.  Cross-sectional view of Laury furnace.

   This process  was used before the introduction of the falling film absorber
and probably all units were installed with two packed columns to absorb the
hydrogen chloride.
   No plants of this type currently operate in the United States.

Emissions
   Emissions of hydrogen chloride from this process are low in concentration
but high in  volume. Other emissions from this process include salt cake dust
Acid Manufacturing Processes
                            21

-------
and sulfuric acid mist. Salt cake dust is eliminated by a dust removal system or
is removed in the acid absorption system.
22                               HYDROCHLORIC ACID EMISSIONS

-------
        ANHYDROUS  HYDROGEN  CHLORIDE

INTRODUCTION
   Anhydrous hydrogen chloride  is  sometimes recovered without  further
processing from the synthesis process. It is also produced from aqueous acid in
three basic steps:
   1. Thermal stripping of a strong hydrochloric acid feed to the 21  percent
      azeotropic mixture.
   2. Cooling, condensing, and recycling part of the  hydrogen chloride as
      reflux.
   3. Cooling and removing the moisture from the gas.
   Strong hydrochloric acid from storage is stripped in an impervious carbon or
graphite shell-and-tube stripper or a similarly packed stripping column (Figure
8). A reboiler is  required at the base of the stripper to provide thermal energy
for the liquid-gas separation. Spent acid leaves the bottom of the stripper. This
acid  is either cooled and stored or sent to the concentration unit for cooling
and concentration in a falling film absorber.
              CONDENSER COOLING BRINE    PURE WATER
         CONDENSER TRAP
                                                     FILTER TO
                                                    REMOVE WATER
                                             .ING BRINE  I	1~
                                    ju
                                             I PRODUCTSOLU
                                      1   '        nr Mri
                                                          DRY
                                                          HO
                                                          GAS
                                    l-4-TREATED ACID FEED
                                        31.5 PERCENT
              PACKED SECTION'
                                   = | » SPENT ACID OUT
                                         II PERCENT
Figure 8.  Hydrogen chloride  distillation system for reagent-quality
           acids.
                                  23

-------
   The hydrogen chloride gas and other vapors from the top of the stripper are
passed through a heat exchanger where the condensate is removed and fed back
as a reflux to the stripper.  The remaining gas, which is  substantially pure
hydrogen chloride, is then dried in a shell-and-tube condenser with a 0° to 5° F
cooling brine and then passed through a particulate entrainment separator for
water removal
   A complete unit that will produce anhydrous acid is available from several
hydrochloric acid equipment manufacturing companies. These units operate in
a similar fashion to the process described here.

EMISSIONS
   This  process yields   no  emissions to  the  atmosphere  because  the
manufacturing system  is closed and the product vapors are piped directly to
the process area.
24                                 HYDROCHLORIC ACID EMISSIONS

-------
      REAGENT-GRADE   HYDROCHLORIC ACID

                        MANUFACTURE

   Commercial-grade 31.5 percent hydrochloric acid is distilled in a rectifying
column to  form reagent-grade  37 to 38 percent hydrochloric acid. Packaged
commercial systems for making reagent acid, as illustrated in  Figure 8, are
available.
   A system for making the reagent-grade acid may also make  dry hydrogen
chloride gas and hydrochloric acid solutions. These systems are  made up of a
boiler at the base of a split column,  a feed to the column (at the split section)
that serves as reflux for the acid being vaporized, a condenser that forms
product hydrogen chloride  and refluxes the hydrogen chloride gas section of
the column, and a cooler-absorber for forming 31.5 percent hydrochloric acid
product if desired. The system is valved so that any one of the three desired
products can be made with only a change of valving. A flow diagram of a plant
of the type described is illustrated in  Figure 8.
   Other types of plants making reagent-grade acid are not of the "package"
type. These  plants are constructed largely of glass and  have tantalum or
titanium heat exchangers for condensing the acid.
   Any acid must be treated before it is distilled.  Minerals and gases, which
may carry over with the acid vapors, must be stabilized  to stay in the 21
percent azeotropic acid remaining after boiling. Processes  for stabilizing the
minerals and gases are proprietary and differ with the acid  manufacturer. The
azeotropic  mixture of  acid remaining after distillation can be used to absorb
more hydrogen  chloride  and then be redistilled, or it can be  used in other
processes.
   Reagent-grade acid may also be  made directly from a relatively pure gas
such as is  produced in the synthesis process without the  need for chemical
treatment or distillation.

EMISSIONS
   This process  yields  no  emissions  to  the  atmosphere  because   the
manufacturing system is closed.

AIR BLOWING
   Air  blowing, used to remove organic substances from hydrochloric acid, can
cause hydrogen chloride and organic emissions that can be a potential source of
odors.  Fortunately, this  obsolete practice is  seldom used and is of  little
industrial importance.
   In the process, air is  blown through a sparger installed  in a tank of
hydrochloric acid to  remove dissolved organic gases and to evaporate organic
materials in the acid. This blowing may take place for a 30-  to 60-minute
period.
   Emissions from air blowing  can be eliminated by water scrubbing the gases
                                   25

-------
vented from the tank. A water ejector can be used to remove the fumes from
the tank as well as to scrub them.
   No reports of air blowing practices were obtained during the preparation of
this report

HYDROGEN CHLORIDE ABSORPTION SYSTEMS

Falling Film Absorber
   The most widely used absorption unit is the falling film system. It consists
of a falling film cooler-absorber and a small packed tails tower.5'6 As shown in
Figures 9 and 10, the gases and the absorbent, which is usually weak acid, enter
at the top of the absorber and the hydrogen chloride is absorbed in the liquid
wetting the inside  of the tube. The absorption is limited by the number of
tubes, which determines the amount of wetted area available for absorption
and cooling.
   After passing through the falling film absorber, the gases pass through a tails
tower where the remaining portion of the hydrogen chloride is reduced to less
than 0.5 percent of the exit gas. Fresh water, which is used as the absorbant, is
fed to this tower, and a weak acid results from the absorption of the hydrogen
chloride in the water.

Adiabatic Absorber
    Another system that is relatively new is the adiabatic absorption unit,6 '7
shown in Figure 11. Used to make an organic-free  acid, this unit consists of a
packed  column into which water is fed near the top, and hydrogen chloride
near the bottom.  Hydrogen chloride and water-contact one another to form
hydrochloric  acid that is at its boiling point.  Excess heat is removed  by the
formation  of  steam.  Inert substances, steam,  and  lower-boiling  organic
materials that cannot condense in the acid because it is at its boiling point are
vented from the column. A water ejector-type scrubber is usually used to scrub
the gases coming from the column.
   Further removal of organic materials may be accomplished by cooling the
acid and running it through a carbon bed where the organics are absorbed.
   A variation of this plant is the modified adiabatic absorption unit. It is not a
true adiabatic system in the usual sense; it is designed to remove more organic
substances and chlorine. In this process, hydrogen chloride gas is injected near
the middle of the column to maintain an adiabatic section in the upper portion
of the column. Heat then can be  added to the  bottom of the column to strip
the acid in the  bottom section of the column. These plants are usually sold
complete with instruments.

Emissions from Absorber Systems
   Hydrogen chloride emissions from a falling film absorber may be influenced
by  several factors.8 These include a lack of cooling and a lack of sufficient
weak acid to  absorb the hydrogen chloride gas. During startups andi shutdowns
when hydrogen  chloride gas flow is less than normal, it is possible that'not all
of the tubes in the absorber will be wetted if the feed water rate is reduced to
maintain product strength. In this situation gas passes through the falling film
26                                 HYDROCHLORIC ACID EMISSIONS

-------
                                               FRESH WATER IN
                                                 INERTS OUT
                                                 TO ATMOSPHERE
                                                     GAS FLOW
                                                      WEAK HYDROGEN
                                                      CHLORIDE GAS
                                                      FROM FALLING
                                                      FILM ABSORBER
                                                      TO TAILS TOWER
          PRODUCT OUT.


Figure 9.  Falling film absorber with external piping and tails tower.
 Reagent-Grade
                                                                      27

-------
                            VENT
               _L
               TAILS
        TOWER SECTION
   COOLING WATER
                                   	•**— FEED WATER
                                            COOLING WATER
                         STRONG ACID

Figure 10. Falling film absorber with integral gas piping and tails
          tower.
                              HYDROCHLORIC ACID EMISSIONS

-------
                                       ORGANIC CONTAMINANTS - STEAM
                  CONDENSED STEAM*.
                ORGANICS - CHLORINE
      AND ORGANIC
        1. ADIABATIC ABSORPTION TOWER RECEIVES BY-PRODUCT HCI GAS STREAM CONTAMINATED
         WITH ORGANICS. ABSORPTION OF HCI IN WATER GENERATES HEAT.
        2. TOWER OVERHEAD CONDENSES BY DIRECT CONTACT FUME SCRUBBER.
        3. HOT HCI SOLUTION COOLED BY SHELL AND TUBE COOLER.
        4. COOLED HCI SOLUTION PUMPED TO EITHER OF TWO ACTIVATED CARBON ADSORBERS ACTING
         ON ADSORB-REGENERATE CYCLE. ORGANIC CONTAMINANTS ADSORBED IN CARBON
         RESULTING IN FINISHED ACID.  32% CONCENTRATION CONTAINING LESS THAN 1 ppm
         ORGANICS AT 100-F. ACID NOW TRANSFERRED TO STORAGE AREA.

Figure 11.  Typical adiabatic hydrochloric acid absorption unit flow
             diagram.

 unit and overloads the tails tower, which also is receiving less than a normal
 amount of feed water.
    The solution to this  problem is  to maintain a minimum flow sufficient to
 wet the tubes. Weak acid produced during these periods can either be discarded
 or concentrated by making higher-strength acid when normal conditions are
 restored.
    The adiabatic absorption unit is not nearly as sensitive to cooling problems
 as the falling film unit because heat is removed by the^ormation of steam. It is,
 however, just as likely to produce  hydrogen chloride emissions if all  of the
 packing is not wetted The technique of maintaining minimum liquid flow as
 described above is also  effective  with  the adiabatic unit. The adiabatic unit,
 with  its. counter  flow   liquid and gas, is more  easily flooded than the
 parallel-flow falling film unit.

 Control of Emissions
    Hydrogen chloride emissions may be effectively controlled by installing any
 of several types  of scrubbers after the tails tower in the case of the falling film
 unit and after the adiabatic tower in the case of the adiabatic unit. Regardless
Reagent-Grade
29

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of the type of absorption unit used for making hydrochloric acid, the best
design is characterized by a final scrubber to remove residual hydrogen chloride
passing through the system
   An adiabatic absorption system normally has a scrubber designed to reduce
the hydrogen chloride content  of the gases emitted to 0.5 percent or less by
volume.
 30                                HYDROCHLORIC ACID EMISSIONS

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                           DEFINITIONS
Absorber
Absorption system


Acid mist


BaimuS (Be)
Contaminant

Emission

Establishment



Muriatic acid

Rant



Reforming



Tail gas
Chemical  equipment that serves to contact a gas or
vapor with a liquid so that gas or vapor is absorbed into
the liquid. In this report, it refers to equipment used to
contact  hydrogen  chloride with  water  to  form
hydrochloric acid.

An  absorber  or several  absorbers  used  to absorb
hydrogen chloride.

Extremely small particles  of  liquid acid that are
suspended in a gas or vapor.

Acid strength  is determined  by  use of a  floating
instrument (hydrometer)  calibrated  to  read  degrees
Baume and by a conversion chart. The Baume can also
be  calculated if the  specific gravity of the acid is
known:                      .*?
             ' Be =145-  (||)

Any substance not normally found in the atmosphere.

Any gas or vapor stream emitted to the atmosphere.

A works having one or more hydrochloric acid plants
or  units,  each of  which is a  complete production
entity.

20° Be hydrochloric acid.

A chemical  works at  whidh  hydrogen chloride  is
manufactured and converted with an absorption unit
into hydrochloric acid.

Burning an  organic fuel in  the presence of water or
water vapor in such a manner that hydrogen-rich gas is
formed.

Gases  and   vapors  that  leave  hydrochloric  acid
absorption units.
                                  31

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                APPENDICES
A. SAMPLING AND ANALYTICAL TECHNIQUES

B. HYDROCHLORIC ACID MANUFACTURING
  ESTABLISHMENTS LOCATED IN UNITED STATES

C PHYSICAL DATA-HYDROCHLORIC ACID
                   33

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    APPENDIX  A.   SAMPLING AND ANALYTICAL
                         TECHNIQUES


 DETERMINATION  OF  HYDROGEN CHLORIDE AND
 CHLORINE IN STACK GAS.
   The method discussed herein is used to determine the presence of hydrogen
chloride in the stack  gases from hydrochloric acid manufacturing processes.
Samples are collected from the  gas stream in either midget impingers or a
grab-sampling bottle containing sodium hydroxide, and hydrogen chloride is
determined by the Volhard titration.9 If chlorine is suspected to be present in
the stack emission, another sample is collected in a similar manner, except that
a  known quantity  of alkaline arsenite absorbing reagent is substituted  for
sodium hydroxide. Chlorine is reduced to chloride by arsenite, and is measured
by titration of the  unconsumed arsenite with standard iodine solution. Total
chloride content of  the  sample is determined by  the Volhard titration.
Hydrogen chloride concentration is calculated by subtraction of the chlorine
concentration from total chloride concentration. This method is applicable in
determining hydrogen chloride and chlorine concentrations ranging from  10
ppm to percentage quantities.
Reagents
   All chemicals must  be ACS analytical reagent-grade.

Water
   Deionized or distilled water.

Absorbing Reagents:
   1. Sodium hydroxide (IN)- Dissolve 40 g of sodium hydroxide in water
     and  dilute  to  1  liter. This reagent is  used when the stack  gas
     concentration of hydrogen chloride is suspected to be less than 1,000
     ppm.
   2. Sodium hydroxide ( 2.5 N) - Dissolve 100  g of sodium hydroxide in
     water and  dilute  to  1  liter.  This reagent  is used when the stack gas
     concentration of hydrogen chloride is suspected to be greater than 1,000
     ppm.
   3. Alkaline arsenite (IN  NaOH and 0.1  N NaAsO2 )   Dissolve 40 g of
     NaOH and 6.5 g of sodium arsenite ( NaAs02 )  in water and dilute to 1
     liter in a volumetric flask. This reagent is used when the stack gas
     concentration of hydrogen chloride and C12 is suspected to be less than
      1,000 ppm.
   4. Alkaline arsenite ( 2.5 N NaOH and 0.5 N NaAsO2 )  Dissolve 100 g of
     NaOH and 32.5  g  of  NaAsO2  in water and  dilute  to ] liter in a
     volumetric  flask. This reagent is used when the  stack gas concentration
     of hydrogen chloride and C12 is suspected to be greater than 1,000 ppm.
34                                HYDROCHLORIC ACID EMISSIONS

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Ferric Alum Indicator
   Dissolve 28.0 g of ferric ammonium sulfate FeNH4 ( SO4 )2 •  12 H2O in 70
ml of hot water.  Cool, filter, add 10 ml of concentrated nitric acid( HNO3 ),
and dilute to 100 ml in a volumetric flask.

Nitric Acid (8N)
   Prepare NOx-free nitric acid by adding 100 ml of HN03 to 100 ml of water
and boiling in  a  flask  until the solution is  colorless. Store  in a glass reagent
bottle.

Nitrobenzene
   Reagent grade.

Sodium Chloride (Primary Standards)
   1.  NaCl (0.1  N) - Dissolve 5.846 g  of dried sodium chloride (NaCl) in
      water and dilute to 1 liter in a volumetric flask.
   2.  NaCl ( 0.01  N ) -  Dissolve 0.5846 g of dried NaCl in water and dilute to
      1  liter in a volumetric flask, or  dilute 100 ml of 0.1 N NaCl to 1 liter.

Ammonium Thiocyanate
   1.  NH4CNS (  0.1 N ) - Dissolve  8 g of NH4CNS in water and dilute to 1
      liter in a volumetric flask.
   2.  N^CNS (  0.01  N ) - Dilute  100 ml of 0.1 N NH,CNS to 1 liter in a
      volumetric  flask, or dissolve 0.8 g NUjCNS in 1 liter of distilled water.

Silver Nitrate
   1.  AgNC-3 ( O.I N) - Dissolve 17.0 g  of silver nitrate ( AgN03 ) in water
      and dilute to 1 liter in a volumetric flask. Transfer to  an amber reagent
      bottle. Standardize this solution against 0.1 N NaCl solution, according
      to the Volhard titration.9
   2.  AgN03 'C0.01 N) - Dissolve  1.7 g of AgN03 in water and dilute to 1
      liter  in a  volumetric flask.  Transfer  to an  amber reagent  bottle.
      Standardize this   solution against  standard  0.01  N NaCl solution,
      according to the Volhard titration.

Starch Solution (Iodine Indicator),  1.0%
   Make a thin paste of 1 g of soluble starch in cold water and pour into 100
ml of  boiling water  while  stirring.  Boil  for a few minutes. Store in a
glass-stoppered  bottle.

Standard Iodine Solution ( 0.1 N )                   '
   Dissolve  12.69  g of resublimed iodine (I2 )  in 25 ml of a solution
containing 15 g  of iodate-free  potassium iodine (KI); dilute to 1 liter in a
volumetric flask.  Standardize this  solution  against a standard tliiosulfate
solution using  starch as an  indicator. This solution should be stored in an
amber reagent bottle and refrigerated when not in use.

Apparatus
(See Figures A-l and A-2)
Appendix A                                                          35

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Sampling Probe
   10-mm Pyrex® glass tubing of any convenient length.

Filter
   A small fiberglass filter may  be  fitted to the probe inlet when particulate
matter is present in the gas stream being sampled.

Heating Tape
   Used to heat probe.

Variable Voltage Regulator
   Used to regulate probe heating.

Dry Gas Meter
   Readable to the nearest 0.01 cubic foot.

Vacuum Pump
   A diaphragm-type pump rated at 15 liters per minute.

Absorbers
   1.  Midget impinger — An all-glass  midget impinger sampling train capable of
      removing hydrogen chloride and chlorine from a gas sample may be used
      when sampling stack gas suspected of containing less than 0.1 percent
      hydrogen chloride or chlorine.
      The sampling train should  consist of a probe, four midget impingers, a
      gas drying tube, a vacuum pump, and a flow meter, as illustrated in
      Figure A-l.
       PROBE
       WITH HEATING
       ELEMENT
                                    ICE BATH           I
                                      METER
               Figure A-l. Impinger gas sampling train.
      A Pyrex® glass tube serves as the probe. It should have a ball joint on the
      outlet to which other glassware can be easily  connected. The probe
      should be wrapped with nickel-chromium heating wire, insulated with
      glass wool and installed into a protective 1-inch-diameter stainless steel
36
HYDROCHLORIC ACID EMISSIONS

-------
      tube. During  sampling, the heating wire is connected to a calibrated,
      variable transformer to maintain a temperature of up to 250° F on the
      probe wall. A heating tape may also be used to heat the probe.
      Four midget glass impingcrs are connected in series to the probe outlet
      with  glass ball joints. The first three impingers each contain  15 ml of
      absorbing reagent. The fourth impinger is left dry  to catch any material
      that  is  carried over from the other impingers.  All four impingcrs are
      cooled in an iccwatcr bath.
      Gases leaving the impingers are dried as they pass through a tube of silica
      gel. They then are pumped to  the airtight vacuum  pump and gas meter.
      Sampling rales are regulated by using a valve to adjust the flow through
      the pump.
  2.  Grab-sampling bottle    An  accurately  calibrated 2-liter glass bottle
      equipped with Teflon® stopcocks (Figure A-2) should be  used when
      sampling percentage quantities  of hydrogen  chloride  or  chlorine.
      Absorbing reagent is added to the grab-sample bottle after the sample has
      been collected.
 ATTACH        ^                                        ^         TO
 PROBE                                                           VACUUM
                   Figure A-2.  Grab  sample bottle.


Dispenser (Absorbing Reagent)
   A 100-milliliter round-bottom flask, modified with a Teflon® stopcock and
ball joint extension (see Figure A-3) is used as a dispenser for absorbing
reagent. It is used to add reagent to the grab-sampling bottle after the sample
has been collected.

Analytical  Procedure
Collection of Samples
   1. Midget impinger train:
     Pipet 15 ml of absorbing reagent into each of the three midget impingers.
     Heat probe to prevent moisture condensation. Start pump and sample at
     a rate of 1 to 3 liters per minute for at least 60 minutes.
   2. Grab sampling:
     Flush probe and draw about 20 liters of gas through the sample bottle.
     Pipct  25 ml  of absorbing reagent into the dispenser and add to the
     grab-sample bottle following collection  of the  sample. Shake bottle
     thoroughly for about 2 minutes to insure complete absorption.
   3. Transfer  the  contents  of  the  impingers  or grab-sampling bottle  to  a
     sample container, such as a polyethylene bottle, containing deionixed or
     distilled water.
Appendix A                                                          37

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                                       100-ml CAPACITY
                      NO. 12/5
                                     'TEFLON STOPCOCK
         Figure A-3.  Burette for adding absorbing reagent.


Sample Preparation
   Measure the actual volume of the liquid sample or adjust to a known volume
using a graduated cylinder or volumetric flask.

Procedure A

Analysis of Hydrogen Chloride
   Pipet an aliquot of the sample into a 250-ml Erlenmeycr flask. Add 25 ml of
water, 5 ml of nitric acid and swirl to mix. Depending on chloride content, add
O.I N or 0.01 N silver nitrate from a buret until the  silver chloride  formed
begins to coagulate. When coagulation occurs, add an additional S ml of silver
nitrate.  Add  3 ml of nitrobenzene and 2  ml of  ferric indicator,  then
back-titrate with 0.1  N or 0.01 N ammonium thiocyanate until the  First
appearance of the reddish-brown Fe(CNS)6~3 complex. A blank determination
for chloride  in the absorbing reagent  should be run  simultaneously  and
subtracted from the sample results. From the  titcr of NH4CNS solution, as
determined previously  by  titration against standard AgNO3 solution using
ferric alum as an indicator, calculate the net volume of AgNO3 required for
precipitation of the chloride.

Calculations
   Compute  the number of milligrams of hydrogen chloride present in the
sample by the following equation:
38
HYDROCHLORIC ACID EMISSIONS

-------
                C = Hd, mg = net ml AgN03 X  T X  F

   T = hy drogen chloride equivalent of standard AgNO3

                ( T =  3.65 mg HCl/ml for 0.1 N AgN03 )
               ( T = 0.365 mg HCl/ml for 0.01 N AgNO3 )
                         „   sample volume, ml
                         r —	
                             aliquot volume, ml
   Convert the volume of gas sampled to the volume at standard conditions of
70° F and 29.92 in. Hg.

                                         530°R
                             29.92    ( t + 460  R)


   V = volume of gas sampled, as measured on dry gas meter or equal to
       volume of grab sample bottle-liters
   P = barometric pressure (in. Hg) or absolute pressure at gas meter
   t =  average temperature of gas sampled, ° R

   Determine the concentration of hydrogen chloride in the gas sample by the
following formula:
                                       Vs
   662 =  jul/mg of HC1 at 70° F and 29.92 in. Hg
   C   =  concentration of HC1, mg
   V s =  volume of gas sampled in liters at 70° F and 29.92 in. Hg

Procedure R

Analysis  of Hydrogen Chloride  in the Presence of Chlorine
   Pipet an aliquot of the sample into a 250-ml Erlenmeyqr flask and proceed
with the Volhard titration  for total chlorides as described under Procedure A.
A blank determination for chloride  in the absorbing reagent (alkaline-arscnite
reagent) should be run simultaneously and subtracted from the sample results.
   Pipet another aliquot of the sample into a 250-ml Erlenmeyer flask. Add a
few drops of phenolphthalein indicator, neutralize carefully with concentrated
hydrochloric  acid,  and cool. Add sufficient solid sodium bicarbonate
( NaHCO3 )  to neutralize any excess hydrochloric acid, then add 2 to 3 g more.
Add 2 ml  of starch indicator and titrate with 0.1 N iodine solution to the blue
endpoint.  For the reagent blank, determine the number of ml of 0.1 N 12
required to  titrate 25 ml of alkaline-arsenite  absorbing reagent, as described
above.
Appendix A                                                        39

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Calculations
   Determine the number of milliliters of 0.1 N I2 required to titrate the entire
sample by the following formula:

        Sample ( ml 0.1 N I2 ) = ( ml of 0.1 N 12 for aliquot)  X  F
                            volume of sample, ml
                        P _ 	
                            volume of aliquot, ml

     Cl2,mg = Blank ( ml 0.1 NI2)   Sample(ml0.1 NI2) X  3.546

               3.546 = chlorine equivalent of 0.1 N I2, mg


   Convert the volume of gas sampled at standard conditions of 70° F, 29.92
in. Hg, using the formula in Procedure A. Calculate the concentration of C12 in
the sample using the following formula:
                                         (340) (C)
                    ppm C12 by volume  =	—	
                                            "s

               340 = 1/mg of C12  at 70°  F and 29.92 in. Hg

   C   = concentration of C12, mg
   V s  =  volume of gas sampled at standard conditions, liters

   Determine the number of milligrams of hydrogen chloride present  in the
sample  by  subtracting the number of milligrams of chlorine  present, as
determined  by  the iodine titration,  from  the total number of milligrams of
chloride  present as determined by the  Volhard  titration.  Calculate  the
concentration of hydrogen chloride  in parts per million using the  formula in
Procedure A.
   Total  stack gas volume must also be measured in order to determine the
emissions on a  weight basis. This may be done by measuring the gas velocity
with a pitot tube.
   The following equations are used  to determine gas velocity and gas volume:
             = 172(F)(VAPavg) |\/TS.X
                                  L
X  —
   MS
   Vg  =  velocity in feet per minute at stack conditions
   F    =  pitot tube—correction factor (0.85 for type S)
   Mo  =  molecular weight of stack gas
   To  =  average stack gas temperature ° R
   Po   =  average stack gas pressure, in. Hg
   AP  =  pitot tube manometer reading, in. water
40                                  HYDROCHLORIC ACID EMISSIONS

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   The total stack gas volume-is then:
                                     TPc"
                                           (17.4)
        A    = stack area, sq ft
        Qs   = gas volume, ft3/minat 70° F and 29.92 in. Hg

   The  emissions on a weight per hour basis may  then be determined by the
following equation:
                       W =  ppm X  10-6 X  Q   X 60  X
                                             s           387

     W       = emissions, Ib/hr
     ppm    = parts per million by volume of contaminant
     Qs      = stack gas flow rate, scfm
     mol wt  = molecular weight of contaminant
     C12     = 70.92         HC1 = .36.46
     387     = volume (ft3)  occupied by 1 Ib mol at 70° F and 29.92 in. Hg
 Discussion of Procedure:
   The estimated error for the combined sampling and analytical procedure is
 ±10 percent. The precision of the analytical methods is ±2 percent on standard
 samples containing NaCl and NaAsO2.
   The  usual volumetric errors  are encountered with the Volhard titration.
 Premature endpoints may occur if the NH4 CNS is not  added by drops near the
 equivalence  point  and  the  solution shaken  before  the  next  addition.
 Nitrobenzene is used to effectively remove AgCl by forming an oily coating on
 the  precipitate  and preventing reaction  with the thiocyanate.10  Bivalent
 mercury,  which  forms  a  stable complexion  with  the  thiocyanate, and
 substances that form insoluble silver salts  interfere in the analysis and must be
 absent from the sample. Titration should be made  at temperatures below
 25° C, as is customary in other titrations with thiocyanate.11
   The chief source of error in the iodine titration of arsenite is the failure to
 use  sufficient bicarbonate to neutralize  all the  excess acid. If insufficient
 bicarbonate is  added,  serious errors may be incurred because of a fading
 endpoint. A reducing agent such as sulfur dioxide and oxidizing agents such as
 iodine, nitrogen dioxide, and ozone interfere with the iodine titration and yield
 high results when present in the stack gas sample.


 ACID MIST SAMPLING.
   The sampling apparatus is made up of a probe, a cyclone, a filter, four
 impingers, a dry gas meter,  a vacuum pump, and a flow meter, as shown in
 Figure A-4.12'13
Appendix A                                                         41

-------
                   Figure A-4.  Mist sampling train.

   A stainless steel, buttonhook-type probe tip (1) is connected to the probe
by a stainless steel coupling (2) and Viton® "0" ring bushings.
   The probe (3) is a 5/8-inch-outside-diameter medium-wall Pyrex® glass tube
with an §-ball joint on one end. The glass probe is wound from the entrance
end with 25 feet of 26 guage nickel-chromium wire.  During sampling the wire
is connected to a calibrated variable transformer to maintain a gas temperature
of 250° F in the probe. The wire-wound glass tube is wrapped with fiberglass
tape and  encased in a  1-inch-outside-diameter  stainless  steel tube  for
protection.
   A glass cyclone (4) is connected to the  outlet end of the probe to catch
larger size mists.
   A very coarse-fritted glass filter holder (5), which holds a 2-H-inch tared
glass fiber filter of MSA type 1106 BH filter paper, follows the cyclone.
   The cyclone and filter are contained in an electrically heated, enclosed box
(6), the temperature of which is thermostatically maintained at a minimum of
250° F to prevent condensation of water.
   Four impingers  in  series, placed in an ice bath, are connected to the filter
holder outlet. The first impinger is  a Greenburg-Smith design modified by
replacing the tip with a H-inch diameter glass tube extending to 0.5 inch from
the bottom of the  flask. This impinger contains 100  ml of sodium hydroxide.
The second impinger is a Greenburg-Smith impinger with tip that also contains
100 ml of sodium  hydroxide. The third impinger is modified the same as the
first  and  is  left  dry.  The fourth  impinger (11)  is  also  a modified
Greenburg-Smith type. It contains about 175 g of dry silica gel.
   From the fourth impinger (11) the effluent stream flows through a check
valve (13),  a needle valve, a leakless  vacuum pump, and a dry gas meter. A
calibrated orifice and a dual manometer complete the train  and  are j used to
measure instantaneous flow rates.
42
HYDROCHLORIC ACID EMISSIONS

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 DETERMINATION OF SULFATES AND SULFURIC ACID.
   This method is used to determine concentrations of sulfuric acid or sulfur
dioxide14 in stack gases from the manufacture of hydrochloric acid by the
Mannheim process.
   Sulfur dioxide  in the stack effluent is absorbed and oxidized to the sulfate
form in midget impingcrs containing 3 percent hydrogen peroxide.
   Sulfuric acid mist is collected on a glass fiber filter paper by an acid mist
sampling train. Sulfates are determined  turbidimetrically by the formation of
barium sulfate as barium  chloride is added. The absorbance of the barium
sulfate suspension is measured spectrophotometrically at 500 m/* with a 1-inch
cell path. This method is applicable  for the  determination of sulfate ion
concentrations of  from 0 to 50 Mg/ml in aqueous media.

Reagents
   All chemicals must be ACS analytical reagent grade.

Water
   Deionized or distilled water.

Absorbing Reagent
   Hydrogen peroxide (3  percent) — Dilute 10 ml of 30 percent hydrogen
peroxide to 100 ml.

Sulfa Ver Powder
   For sulfates in water manufactured by the Hack Chemical Company, Ames,
Iowa.*

Standard Sodium Sulfate
   Dissolve 1.469  grams of sodium sulfate in 1 liter of water. Dilute 100.0 ml of
this solution to 1 liter with water in a volumetric flask. This solution contains
100Mg(S04')/mL


Sample  Preparation
   Transfer  the contents of the midget  impingers or the glass fiber filter to a
sample container.  Dilute the impinger solution to a known volume and/or add
a known volume of water to the filter for solubalization of the sulfate.

Procedure
   Pipet 20 ml or a  suitable aliquot made up to 20 ml into a 1-inch cuvette or
test  tube.   Read  the  absorbance  against  a distilled water  blank (blank
correction). This value will be subtracted from the final absorbance reading to
correct for unmatched cuvettes. Add one level spoonful (0.3 g) of Sulfa Ver
powder and shake to mix.
   Between 5 minutes and 20 minutes after the Sulfa Ver powder is added, the
absorbance should be read on'a spectrophotometer at 500  rh/Lt. Use a blank of

*Mcntion  of company or product name does not constitute endorsement by the U.S.
Department of Health, Education, and Welfare.
Appendix A                                                         43

-------
water and Sulfa Ver powder to set the spectrophotometer to zero absorbance.
Determine the  amount  of  sulfate present from a  previously  prepared
calibration curve.

Preparation of Calibration Curve
   Prepare a series of standards ranging from 0 to 50 Mg/ml from the working
standards solution. Measure the absorbance of these standard solutions in the
manner described in the procedure. Construct a calibration curve by plotting
/ug (S04 )/ml versus absorbance.

Calculations
   Compute the number of mg of SO2  present in the sample by the following
formula:
                                64 = molecular weight of SO2
                                96 = molecular weight of (S04)
   Compute mg of H2 SO4 present in the sample by the following formula:
                                   no
         H2S04,mg = (SOi),mgX
                                96 = molecular weight of (SO4)
                                98 = molecular weight of sulfuric acid.

                              (377)(mgofS02)
                  SO2,ppm = - T;
                                    V
                                      s
    377 = jd/mg of S02 at 70° F and 29.92 inches of Hg
    V s = volume of gas sampled in liters at 70° F and 29.92 inches of Hg
                              ,   H2SO4,/ug
                  H2S04,|Ug/m3 =  '
                                     v s
    V s = volume of gas sampled in cubic meters at 70° F and 29.92 inches of
         Hg
44                                HYDROCHLORIC ACID EMISSIONS

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         APPENDIX 6.  HYDROCHLORIC ACID
  MANUFACTURING  ESTABLISHMENTS LOCATED
                   IN UNITED STATES
                          January 1968

                      Type of Process Utilized

          B = By-Product
          S = Chlorine-Hydrogen Synthesis
          M = Mannheim
          H = Hargreaves
State
Company name
Alabama
     Giegy Chemical Corp.
     Monsanto Co.
     Olin Matheison Chemical Corp.
     Olin Matheison Chemical Corp.
     Stauffer Chemical

Arkansas
     Arkla Chemical Corp.

California
     American Chemical Corp.
     J.H. Baxter & Company
     Chevron Chemical Company
     Dow Chemical Co.
     E.I. duPont dcNemours & Co.
     Neville Chemical Co.
     Stauffer Chemical Co.
     Montrose Chemical Corp. of Calif.
     Witficld Chemical Corp.

Connecticut
     The Upjohn Co.
     Uniroyal Co.

Delaware
     Allied Chemical Corp.
     Standard Chlorine of Delaware
Location              Type
                     Mclntosh              B
                     Anniston              B
                     Mclntosh              B
                     Huntsville             B
                     LeMoyne              B
                     Pine Bluff
                     Long Beach            B
                     Long Beach            B
                     Richmond             B
                     Pittsburgh             B
                     Antioch               B
                     Santa Fe Springs        B
                     Domingue/. (LA.)       B
                     Torrance              B
                     Watson               B
                     North Haven           B
                     Naugatuck             B
                     North Claymont        B
                     Delaware City          B
Appendix B •
                                              45

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Georgia
      Chemical Products Corp.            Cartersville
      Hercules, Inc.                      Brunswick
      Merck & Company                  Albany

Illinois
      Allied Chemical Corp.               Danville
      Baird Chemical Industries, Inc.       Peoria
      Cabot Corp.                       Tuscola
      Monsanto Co.                      Sauget
      The Richardson Co.                 Chicago
      The Richardson Co.                 Lemont

Indiana
      E.I. duPont deNemours & Co.        East Chicago
      Keil Chemical                      Hammond
                           B
                           B
                           B
                           B
                           B
                           B
                           B
                           B
                           B
                           B
                           B
 Kansas
      Racon, Inc.
      Vulcan Materials Co.
    Clearwater
    Wichita
 B
 B,S
Kentucky
      E.I. duPont deNemours & Co.        Louisville
      Hooker Chemical Corp.             South Shore
      Pennsalt Chemical Corp.             Calvert City
      Stauffer Chemical Co.               Louisville
                           B
                           B
                           B
                           B
 Louisiana
      Allied Chemical Corp.               Geismar
      Allied Chemical Corp.               Baton Rouge
      Conoco                           Lake Charles
      Dow Chemical Co.                  Plaquemine
      Ethyl Corp.                        Baton Rouge
      Hooker Chemical Co.               Taft
      Kaiser Aluminum & Chemical Co.     Gramercy
      Morton Chemical Co.               Weeks Island
      Morton Chemical Co.               Giesmar
      Pittsburgh Hate Glass Co.            Lake Charles
      Rubicon Chemicals, Inc.             Lake Charles
      Shell Chemical Co.                  Norco
      Vulcan Materials Co.                Geismar
      Wyandotte Chemical Corp.           Geismar
                           B
                           B
                           B
                           B,S
                           B,S
                           B
                           B
                           H
                           B
                           B
                           B
                           B
                           B
                           B
Maryland
     Chemetron Corp.
     Continental Oil Co.
     FMC
    Elkton
    Baltimore
    Baltimore
B
B
B
46
HYDROCHLORIC ACID EMISSIONS

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Massachusetts
     Monsanto Co.                      Everett
     Solvent Chemical Co.                Maiden

Michigan
     Dow Chemical Co.                  Midland
     Dow Corning Co.                   Midland
     E.I. duPont deNemours & Co.        Montague
     Hooker Chemical Corp.              Montague
     Ott Chemical Corp.                 Muskegon
     Pennsalt Chemical Corp.             Wyandotte

Missouri
     Monsanto                         St. Louis

Nevada
     Montrose Chemical Corp. of Calif.    Henderson
     Stauffer Chemical Co.               Henderson
                       B
                       B
                       B
                       B
                       B
                       S
                       B
                       B,S
                       B
                       B
New Jersey
     Allied Chemical Corp.               Elizabeth
     Baldwin-Montrose Calif. Co.          Newark
     Benzol Products Div.                Newark
     W.A. Cleary Corp.                  New Brunswick
     Diamond Alkali Co.                 Newark
     E.I. duPont deNemours & Co.        Carney's Point
     E.I. duPont deNemours & Co.        Deepwater
     E.I. duPont deNemours & Co.        Linden
     Enjay Chemical Co.                 Bayway
     General Aniline & Film Corp.        Linden
     Hercules, Inc.                      Parlin
     ICI                               Bayonne
     Merck & Co.                       Rahway
     Mobil Oil Corp.                    Metuchen
     Pearsall Chemical Corp.              Phillipsburg
     Tenneco Chemical Inc.              Fords
     Toms River Chemical Corp.          Toms River
     Vulcan Materials Co.                Newark
     Weston Chemicals Corp.             Newark
     White Chemicals Co.                Bayonne
                       B
                       B
                       B
                       B
                       B
                       B
                       B
                       M
                       B
                       S
                       B
                       B
                       B
                       B
                       B
                       B
                       B
                       B
                       B
                       B
New Mexico
      Climax Chemical Co.
Hobbs
M
New York
     Allied Chemical Corp.               Buffalo
     Allied Chemical Corp.               Syracuse
     E.I. duPont deNemours & Co.        Niagra Falls
                       B
                       B
                       B,S
Appendix B
                        47

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     Eastman Kodak Co.
     Hooker Chemical Corp.
     Hooker Chemical Corp.
     Stauffcr Chemical Corp.
    Rochester              B
    Niagra Falls             B,S
    North Tonawanda        B,S
    Niagra Falls             B
Ohio
     Detrex Chemical Ind.               Ashtabula
     Diamond Alkali Co.                 Painesville
     Dover Chemical Corp.               Dover
     E.I. duPont deNemours & Co.        Cleveland
     Olin Matheison Chemical Corp.       Ashtabula
     Pittsburgh Plate Glass Co.           Barberton
     Tennessee Corp.                    Evendale
                           B
                           B,S
                           B
                           M
                           B
                           B
                           M
Oregon
     Pennsalt Chemical Corp.
    Portland
Pennsylvania
     Allegheny Electronic Chemical Co.    Bradford
     Koppers Co., Inc.                   Bridgeville
     Lebanon Chemical Co.              Lebanon
     Rohm & Haas Co.                  Philadelphia
     U.S. Steel Corp.                    Clairton
                           B
                           B
                           B
                           B
                           B
Tennessee
     Stauffer Chemical Co.
     Velsicol Chemical Corp.
    Mt. Pleasant
    Chattanooga
 B
 B
Texas
     Atlantic Richfield Co.
     Diamond Alkali Co.
     Diamond Alkali Co.
     Dow Chemical Co.
     Dow Chemical Co.
     E.I. duPont deNemours & Co.
     Ethyl Corp.
     Monsanto Co.
     Monsanto Co.
     Phillips Petroleum Co.
     Phillips Petroleum Co.
     Potash Co. of America
     Shell Chemical Co.
     Stauffer Chemical Co.
     Union Carbide Corp.
     The Upjohn Co.
     Vulcan Materials Co.
    Port Arthur
    Deer Park
    Greens Bayou
    Freeport
    Oyster Creek
    La Porte
    Houston
    Texas City
    Alvin
    Pasadena
    Deer Park
    Dumus
    Houston
    Fort Worth
    Texas City
    La Porte
    Denver City
 B
 B,S
 B
 B
 B
 S
 B,S
 B
 B
 B
 B
 B
 B
 M
 B
;B  i
 S
48
HYDROCHLORIC ACID EMISSIONS

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Utah
     National Lead Co.                   Lakepoint       (experimental)

Virginia
     Hercules, Inc.                       Hopewell               M
     Olin Matheison Chemical Corp.       Saltville                S

Washington
     Hooker Chemical Corp.              Tacoma                S,B
     Pennsalt Chemical Corp.             Tacoma                S
     Reichhold Chemicals, Inc.            Tacoma                B

West Virginia
     Allied Chemical Corp.               Moundsville             B
     Diamond Alkali Co.                 Belle                   B
     FMC Corp.                         South Charleston        B
     FMC Corp.                         Nitro                   B
     Mobay Chemical Co.                New Martinsville         B
     Monsanto Co.                      Nitro                   B
     Pittsburgh Plate Glass Co.            Natrium                B,S
     Stauffer Chemical Co.               Gallipolis Ferry          B
     Union Carbide Corp.                Institute                B
     Union Carbide Corp.                South Charleston        B
Appendix B                                                        49

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           APPENDIX C.
PHYSICAL DATA-HYDROCHLORIC ACID
                51

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Table C-1. SPECIFIC GRAVITIES OF AQUEOUS HYDROCHLORIC ACID SOLUTIONS8

                                Standard Adopted 1903
                              Authority - W. C. Ferguson
Density,
°Be
1.00
2.00
3.00
4.00
5.00
5.25
5.50
5.75
6.00
6.25
6.50
6.75
7.00
7.25
7.50
7.75
8.00
8.25
8.50
8.75
9.00
9.25
9.50
9.75
10.00
10.25
10.50
10.75
11.00
11.25
11.50
11.75
12.00
12.25
12.50
12.75
13.00
13.25
13.50
13.75
14.00
14.25
14.50
14.75
15.00
15.25
15.50
15.75
Specific
gravity
1.0069
1.0140
1.0211
1.0284
1.0357
1.0375
1.0394
1.0413
1.0432
1.0450
1.0469
1.0488
1.0507
1.0526
1.0545
1.0564
1.0584
1.0603
1.0623
1.0642
1.0662
1.0681
1.0701
1.0721
1.0741
.0761
.0781
.0801
.0821
.0841
.0861
1.0881
1.0902
1.0922
1.0943
1.0964
.0985
.1006
.1027
.1048
.1069
.1090
.1111
.1132
.1154
.1176
.1197
.1219
Percent
HCI
1.40
2.82
4.25
5.69
7.15
7.52
7.89
8.26
8.64
9.02
9.40
9.78
10.17
10.55
10.94
11.32
11.71
12.09
12.48
12.87
13.26
13.65
14.04
14.43
14.83
15.22
15.62
16.01
16.41
16.81
17.21
17.61
18.01
18.41
18.82
19.22
19.63
20.04
20.45
20.86
21.27
21.68
22.09
22.50
22.92
23.33
23.75
24.16
Density,
"Be1
16.0
16.1
16.2
16.3
16.4
16.5
16.6
16.7
16.8
16.9
17.0
17.1
17.2
17.3
17.4
17.5
17.6
17.7
17.8
17.9
18.0
18.1
18.2
18.3
18.4
18.5
18.6
18.7
18.8
18.9
19.0
19.1
19.2
19.3
19.4
19.5
19.6
19.7
19.8
19.9
20.0
20.1
20.2
20.3
20.4
20.5
20.6
20.7
Specific
gravity
.1240
.1248
.1256
,1265
.1274
.1283
.1292
.1301
.1310
.1319
.1328
.1336
.1345
.1354
.1363
.1372
.1381
.1390
.1399
.1408
.1417
.1426
.1435
.1444
.1453
.1462
.1471
.1480
.1489
.1498
,1508
.1517
.1526
.1535
.1544
.1554
.1563
.1572
.1581
.1590
.1600
.1609
.1619
.1628
.1637
.1647
1:1656
1.1666
Percent
HCI
24.57
24.73
24.90
25.06
25.23
25.39
25.56
25.72
25.89
26.05
26.22
26.39
26.56
26.73
26.90
27.07
27.24
27.41
27.58
27.75
27.92
28.09
28.26
28.44
28.61
28.78
28.95
29.13
29.30
29.48
29.65
29.83
30.00
30.18
30.35
30.53
30.71
30.90
31.08
31.27
31.45
31.64
31.82
32.01
32.19
32.38
32.56
32.75
Density,
"Be1
20.8
20.9
21.0
21.1
21.2
21.3
21.4
21.5
21.6
21.7
21.8
21.9
22.0
22.1
22.2
22.3
22.4
22.5
22.6
22.7
22.8
22.9
23.0
23.1
23.2
23.3
23.4
23.5
23.6
23.7
23.8
23.9
24.0
24.1
24.2
24.3
24.4
24.5
24.6
24.7
24.8
24.9
25.0
25.1
25.2
25.3
25.4
25.5
Specific
gravity
1.1675
1.1684
.1694
.1703
.1713
.1722
.1732
.1741
.1751
.1760
.1770
.1779
.1789
.1798
.1808
.1817
.1827
.1836
.1846
.1856
.1866
.1875
.1885
.1895
.1904
.1914
.1924
.1934
.1944
.1953
.1963
.1973
.1983
1.1993
1.2003
15013
15023
1.2033
1.2043
1.2053
1.2063
1.2073
1.2083
1.2093
1.2103
15114
1.2124
1.2134
Percent
HCI
32.93
33.12
33.31
33.50
33.69
33.88
34.07
34.26
34.45
34.64
34.83
35.02
3551
35.40
35.59
35.78
35.97
36.16
36.35
36.54
36.73
36.93
37.14
37.36
37.58
37.80
38.03
38.26
38.49
38.72
38.95
39.18
39.41
39.64
39.86
40.09
40.32
40.55
40.78
41.01
41.24
41.48
41.72
41.99
42.30
42.64
43.01
43.40
                            Allowance for temperature:

10-15° Be.-1/40° Be or 0.0002 Sp. Gr. for 1° F.
10-22° Be.-1/30° Be or 0.0003 Sp. Gr. for 1° F.
22-25° Be.-1/28° Be1 or 0.00035 Sp. Gr. for 1° F.

Originally published as Manufacturing Chemists' Association, Inc. Manual Sheet
 SD-39. Copies of a similar table giving ° Be1, Sp. Gr. and Tw ° corresponding with
 percent HCI, are available through the MCA as Manual Sheet T-3.
52
HYDROCHLORIC ACID EMISSIONS

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                 VAPOH PRESSURES OF AQUEOUS
                 Miunom OF HYDBOCHLOSIC ACID
      0.01       .05   0.1        0.5  1         5   10        SO  100
                           PARTIAL PRESSURE-HCI, mm Hg
                                                                  500  1000
Figure C-l.  Vapor pressure of hydrochloric acid  at  various concen-
              trations.
   -.  20
   3 10
                     I
                                    r
                                         ^SPECIFIC GRAVITY
                                    20              30
                             HCI BY WEIGHT, p.rc.nt
 Figure C-2.  Specific gravity and  density versus percent hydrogen
               chloride.
Appendix C
53

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                            ACID BY WEIGHT, p.r«nt
figure C-3.  Relationship of viscosities of hydrogen chloride and
              water.
          a 650
          a
                                          OF SOLUTION AT 50* C    __




                                      INTEGRAL HEAT OF SOLUTION AT IS* C





                                          V
                                          "*«%   BOILING POINT-***^
                              PARTIAL HEAT OF SOLUTION AT !»• C
                                                      \
                        J	I     I
                         10     II     20
                                               j	I
                             ACID CONCENTRATION,
   Figure C-4.  Heats of solution of hydrogen chloride in water.
54
HYDROCHLORIC ACID EMISSIONS

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                                                            so
                    HCI CONCENTRATION, weight p.rc.nl
     Figure C-5. Vapor-liquid equilibra for hydrochloric acid.
Appendix C
55

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                10     IS     20     25    30    35
                      ACID CONCENTRATION, w.ijt.1 p»rc«nl
                                                         45
        Figure C-6. Boiling point of hydrochloric acid solution.
56
HYDROCHLORIC ACID EMISSIONS

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    •20
    -30
    •40
    •60
    -70
    -80
    •90
             10       20       30       40      50       60
                          CONCENTRATION, w.ight p.rc.m
                                                              70
                                                                     80
     Figure C-7.  Freezing point of aqueous hydrogen chloride.
Appendix C
57

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                               REFERENCES
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 2. Furnas, G.C., Rodgers' Industrial Chemistry, 6th Edition, Volumes I and II, D. Van
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 3. Buckley, Joseph A., "Vinyl Chlorides via Direct Chlorination and Osychlorination,"
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 4. Albright, Lyle F., "Vinyl Chloride Processes," Chemical Engineering, March 27, 1967,
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 5. "Karbate Brand  Impervious  Graphite  Falling Film Type  Absorber, Series 31 A,"
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 6. "Process Design, Haveg Chemical Equipment," Haveg Catalog, Section 7-0, Chemical
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 7. Kolbe, Von, Dr. E. and Dr. F. Brandmair, "Entwicklugen bei der  Adiabatischen
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 8. Gaylord, W.M. and M.A. Miranda, "The Falling-Film Hydrochloric Acid Absorber,"
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 9. Standard Methods of Chemical  Analysis, 6th  Edition, Volume 1, D.  Van Nostrand
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10. Caldwefl, I.E. and H.V. Mayer, fnd. Eng. Chen, Anal. Ed., 7, 38, 1935.

11. Jacobs, M.B., The Chemical Analysis of Air Pollutants, Interscience Publishers, Inc., p.
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12. Patton, W.E. and J.A. Brink, "New Equipment and Techniques for Sampling Chemical
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                                                           •
13. Smith, W., et  al., "Stack  Gas  Sampling Improved and Simplified  with  New
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14. ASTM Standards, Part 23 Industrial Water; Atmospheric Analysis, 1965, pp. 26-28.

15. Perry, J.H., Chemical Engineering Handbook, Volume IV,  McGraw-Hill Book Co.,
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                                        59

                                        * U.S. GOVERNMENT PRINTING OFFICE: 1969 O—3S5-116

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