EPA-4 50/3-74-009
May 1973
         NATIONAL EMISSIONS
                    INVENTORY
                    OF  SOURCES
                AND EMISSIONS
                               OF
                  MOLYBDENUM
   U.S. ENVIRONMENTAL PROTECTION AGENCY
       Office of Air and Water Programs
   Office of Air Quality Planning and Standards
   Research Triangle Park, North Carolina 27711

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                                         EPA-450/3-74-009
NATIONAL  EMISSIONS  INVENTORY
                        OF

       SOURCES  AND EMISSIONS
                        OF

               MOLYBDENUM
                         by

                    GCA Corporation
                 GCA Technology Division
               Bedford, Massachusetts  01730
                  Contract No. 68-02-0601
             EPA Project Officer:  David Anderson
                      Prepared for

            ENVIRONMENTAL PROTECTION AGENCY
               Office of Air and Water Programs
           Office of Air Quality Planning and Standards
             Research Triangle Park, N. C.  27711

                       May 1973

                       U.S. Environmental Pr^'' ^' R'
                       Region 5, Library ^
                       77 West Jackson i'-'     ,-'.•• •~':;or
                       Chicago, IL 606C-V-. .j

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This report is issued by the Environmental Protection Agency to report technical
data of interest to a limited number of readers.  Copies are available free of
charge to Federal employees, current contractors and grantees, and nonprofit
organizations - as supplies permit - from the Air Pollution Technical Information
Center, Environmental Protection Agency, Research Triangle Park, North
Carolina 27711, or from the National Technical Information Service, 5285 Port
Royal Road, Springfield, Virginia  22151.
This report was furnished to the Environmental Protection Agency by GCA Corp-
oration, Bedford, Massachusetts, in fulfillment of Contract No. 68-02-0601.  The
contents of this report are reproduced herein as received from GCA Corporation.
The opinions, findings, and conclusions expressed are those of the author
and not necessarily those of the Environmental Protection Agency. Mention  of
company or product names is not to be considered  as an endorsement by the
Environmental Protection Agency.
                    Publication No. EPA-450/3T?4-009

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                           TABLE OF CONTENTS


SECTION        	TITLE	.        PAGE

               ACKNOWLEDGEMENT                                      V

               ABSTRACT                                            vi

   I           INTRODUCTION                                         1
               A.   PURPOSE AND SCOPE                               1
               B.   CONCLUSIONS                                     2

  II           OVERALL U.S. MATERIAL FLOW CHART FOR MOLYBDENUM -
               1970                                                 4
               A.   U.S. PRODUCTION AND ORE PROCESSING              4
               B.   IMPORTS AND EXPORTS OF MOLYBDENUM CONCENTRATE   4
               C.   GOVERNMENT AND INDUSTRIAL STOCKPILE CHANGES     4
               D.   METALLURGICAL USES                              4
               E.   CHEMICAL USES                                   6

  III          SOURCES AND ESTIMATES OF MOLYBDENUM-CONTAINING
               EMISSIONS                                            7
               A.   DATA PRESENTATION AND ACCURACY                  7
               B.   DEVELOPMENT OF EMISSIONS ESTIMATES - 1970       12
               C.   SUMMARY OF PRINCIPAL EMISSIONS                  17

  IV           REGIONAL DISTRIBUTION OF PRINCIPAL SOURCES AND
               EMISSIONS                                            18

   V           NATURE OF EMISSIONS                                  21

  VI           UPDATING OF EMISSIONS ESTIMATES                      25
               A.   VERIFICATION OF CURRENT ESTIMATES               25
               B.   PERIODIC REVIEW OF ESTIMATES                    25

               REFERENCES                                           27
                                     111

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                        LIST OF TABLES AND FIGURES


 TABLE No.           	TITLE	             PAGE

      1               SOURCES AND ESTIMATES OF MOLYBDENUM-
                     CONTAINING EMISSIONS                              8

      2               SUMMARY OF PRINCIPAL SOURCES AND
                     EMISSIONS OF MOLYBDENUM                          17

      3               REGIONAL DISTRIBUTION OF PRINCIPAL
                     SOURCES AND EMISSIONS                            20

      4               PHYSICAL PROPERTIES OF MOLYBDENUM
                     AND COMPOUNDS                                    21
Figure No.

     1               MOLYBDENUM MATERIALS FLOW - 1970
                                        IV

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                           ACKNOWLEDGEMENT

       The continued cooperation and dedication of Mr. Carl Spangler
of EPA, who served as Program Monitor until his death, is deeply
appreciated.
       GCA would like to extend thanks to Mr. David Anderson and
Mr. James Southerland of EPA for their cooperation in the preparation
of this study.
       In addition, special thanks are also due to Mr. Andrew Kulis,
Commodity Specialist, Bureau of Mines, who provided significant
technical inputs to this program.

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                                ABSTRACT
       A national inventory of the sources and emissions of the
element molybdenum was conducted.  The study  included the preparation
of an overall material flow chart depicting the quantities of moly-
bdenum moving from sources of mining and importation through all
processing and reprocessing steps to ultimate use and final disposition.
All major sources of molybdenum-containing emissions were identified
and their molybdenum emissions into the atmosphere estimated.  A
regional breakdown of these sources and their emissions was also
provided.  The physical and chemical nature of the molybdenum-containing
emissions was delineated to the extent that information was available,
and a methodology was recommended for updating the results of the study
every two years.

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I.     INTRODUCTION

       A.  PURPOSE AND SCOPE

           The Monitoring and Data Analysis Division,  Office of Air

Quality Planning and Standards of the U.S. Environmental Protection

Agency (EPA) has contracted with GCA Technology Division to conduct a

national inventory of the sources and emissions of the element molyb-
denum.  The purpose of the study was to define as accurately as pos-
sible, based on existing and available published and unpublished infor-

mation, the levels, nature and sources of molybdenum containing emis-
sions for defined geographic regions throughout the United States.

           The scope of this program is outlined below:

           .  Develop an overall material flow chart
              depicting the quantities of molybdenum
              moving from sources of mining and impor-
              tation, through all processing and
              reprocessing steps to ultimate use and
              final disposition as far as the move-
              ments can be treated.
              Identify all major potential molybdenum
              containing emission sources, and esti-
              mate the total quantity of molybdenum
              emitted to the atmosphere from each
              source.  Emission factors,  level, and
              types of air pollution control will
              also be provided for each of these
              sources to the extent that  available
              information permits.
            .  Define those sources which  contribute
              at  least 80 percent of the  total emis-
              sions of molybdenum.
              Provide a regional breakdown of these
              major sources  and their emissions.
            .  Present the nature of the molybdenum con-
              taining emissions for each  of these major
              sources including a delineation of their
              physical and chemical form  and particle
              size distribution to the extent that
              information is available.
              Provide recommendations as  to a methodol-
              ogy for updating the results of this
              study every two years.

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         B.   CONCLUSIONS
             1.  Material Flow
                Based on all available data,  34,821 tons of
 molybdenum  were  consumed  in the  U.S.  in  1970.   The sources of
 molybdenum  were  imports, releases from government stockpiles, and
 domestic mining.

                A major portion of the molybdenum ore concentrate was
 converted to the oxide.  Most of the oxide was consumed in making steel
 and other alloys, with only a small portion being used for pigments,
 catalysts,  lubricants, and other miscellaneous products.
            2-  Principal Emission Sources
                Two thirds  of the estimated atmospheric emissions of
 molybdenum are not associated  with the molybdenum industry,  but result
 from the combustion of coal.   Coal is far the largest  source  of
 emissions.   Despite a relatively small concentration of molybdenum in
 coal,  there was sufficient quantity of coal burned to produce about 610
 tons of emitted molybdenum in  1970.

                Within the molybdenum industry,  several  sources  were
 identified  as being of  approximately similar  consequence:   the  mining of
 ore; the production of  ferromolybdenum; the production  of  steel con-
 taining molybdenum as an alloying ingredient; and  the  roasting  of  ore
 concentrate.  Together  these are  estimated to produce about 29% of all
 U.  S.  emissions.
           3.   Regional Emissions
                The  region of the  U.  S. in  which most of the molybdenum
 is  estimated  to be  emitted  is Region 5* (Ohio and vicinity).   This  is
 partly  due to the  large emission  from coal combustion.   In the  absence
 of  this, the molybdenum industry alone would produce the largest
 total emission  in Region 9, princpally Arizona, based on certain
 assumptions  set forth in Chapter IV.
*See page 18 for a  list of regions.

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           4.   Nature of Emissions
               Based on the physical properties of molybdenum
and its compounds, most of its emissions are estimated to be in
particulate form ranging from submicrometer to micrometer sized
particles.  The chemical forms are believed to be largely simple oxides
and sulphides, with little elemental molybdenum being emitted.
           5.   Degree of Control
               The overall level of control of molybdenum emission is
estimated to have been about 86 percent in 1970.  The degree of control
would have been greater, but for the relatively poor control of coal
flyash  (82 percent estimated), which sharply lowered the overall
average.

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  11'     OVERALL  U.  S. MATERIAL FLOW  CHART FOR MOLYBDENUM -  1970
         The molybdenum  industry uses mining, co-product,  and  import
  sources of molybdenum  disulphide concentrate.  This material, for the
  most part, is roasted  to molybdenum oxide, most of which is  consumed in
  steelmaking and other metallurgical processes.  The industry is
  described in more detail below and in Section III.  Figure 1* presents
  a flow diagram depicting the total quantities of molybdenum products
 moving from sources through the processing and reprocessing steps to
 ultimate use and final disposition.
        A.   U. S. PRODUCTION AND ORE PROCESSING
            Molybdenum is produced in the U. S.  both as a primary yield
 and as a co-product yield from copper,  tungsten,  and uranium operations.
 Of the 55,676 tons of molybdenum produced  from these sources in 1970,
 68 percent was as  a primary yield.   The primary ore contains typically
 only 0.3 percent molybdenum disulphide,  and thus  requires extensive
 beneficiating  operations including  flotation.   Similar beneficiating
 processes  are  used in producing  co-product  concentrates.(1)
        B.   IMPORTS AND EXPORTS OF MOLYBDENUM CONCENTRATE
           Due to  high  import tariffs for molybdenum products and  a
 self-sufficiency in  production, only 12  tons were  imported  into  the
 United  States  in 1970.   Total exports of ore and concentrates totaled
 27,800  tons of contained molybdenum.^
        C.  GOVERNMENT AND INDUSTRIAL STOCKPILES CHANGES
           The Bureau of Mines    reports that inventories  of industrial
 stocks  increased  by 658 tons in  1970.   GCA, however,  in their prepara-
 tion of Figure 1, estimates a decrease of 4,533 tons in  industrial
 stockpiles in order to supply the necessary raw material  for  reported
 consumption levels.  The National Government Stockpile was  reduced by
 2,400 tons in 1970.^
*Note.  Data in Figure 1 and in this section are left unrounded, for
        purposes of information control.  On the average, the typical
        statistic is accurate to within 10%, in the opinion of the
        investigators.

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       D.  METALLURGICAL USES
           Almost all the concentrate is roasted to the oxide except
for a very minimal amount which remains as the sulfide and is purified
for use as a lubricant.  The principal primary products from the
roasted concentrate used by the metallurgical industries are
molybdenum oxide and ferromolybdenum.  A small amount of metal power,
about 3% of total, was used predominantly in mill products.  '
Almost 90 percent of exports of primary products (8,365 tons) were
roasted concentrate or molybdenum oxide.     The domestic use by the
metallurgical industry totals 20,806, tons or 91.7 percent of domestic
molybdenum/ '  Of this, steel production is by far the major
consumer (71 percent).
       E.  CHEMICAL USES
           Although the principal primary product  used in the chemical
industries is molybdic oxide, ammonium and sodium molybdates are used
in the production of pigments, catalysts and other miscellaneous
chemicals.   In 1970,  1,342 tons of molybdic oxide, 805 tons of
ammonium molybdate and 343 tons of sodium molybdate were used to
produce 529 tons of pigments,  906 tons of catalysts,  and 426 tons of
other products (mainly ceramics).   '  All weights expressed are in terms
of contained molybdenum content.

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HI.  SOURCES AND ESTIMATES OF MOLYBDENUM - CONTAINING EMISSIONS
      A.   DATA PRESENTATION AND ACCURACY
           Table 1 presents a summary of the data from which emissions
were estimated for all major potential sources.  Each of the
columns comprising this table will be discussed below.
           1.   Emission Factors
                Except where indicated, this gives the pounds of total
particulates emitted per ton of production.  Such considerations as:
                      variations in process conditions among
                      individual plants comprising a source
                      category
                      inaccuracies in existing data
                      a limited quantity of existing data,
may, however, result in an average emission factor for a source
category varying by more than an order of magnitude from the value
presented.   In recognizing the need to indicate the level of accuracy
of  these emission factors, a reliability code  is presented along with
each emission factor value appearing  in the Table.  This reliability
code system  is described below and is based on the system utilized  in
EPA Document No. AP-42, "Compilation  of Air Pollutant Emission  Factors":
                   A: Excellent
                      This value  is based  on field measurements
                      of a large number of sources.
                   B: Above Average
                      This value  is based  on a limited number of
                      field measurements.
                   C: Average
                      This value is based on limited data and/or
                      published emission factors' where the
                      accuracy is not stated.
                   D: Below Average
                      This emission factor is  based on
                      engineering estimates made by know-
                      ledgeable personnel.

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                                                                     TABLE  I
                                             SOURCES AND ESTIMATES OF MOLYBDENUM-CONTAINING  EMISSIONS
Source
MINING
Open Pit
Underground
Copper Open Pit
BENEFICIATION

ROASTING

METALLURGICAL
Ferromolybdenum-
Electric Arc
Molybdenum Metal
CHEMICAL PRODUCTION

STEEL & ALLOY PRODUC-
TION
Steel
Cast Iron
Super Alloys
Alloys
Mill Products
Particulate
Emission
Factor ,
(Ib/ton)

10
0.5
10

52

100

200
2000

Nil


25
15
200
25
0.5
(kg/kgxlO )

15
0.25
5

26

50

100
1000

Nil


12.5
7.5
100
12.5
0.25
Reliability
Code

D
D
D

D

C

D
B




C
C
C
C
C
Production
Level
(tons/yr)

13,000
25,986
16,690

34,821

34,821

6,221
803

1,148


14,712
1,958
1,254
395
858
% Mo in
Emissions

*
*
*

*

*

*
*

*


*
*
*
*
*
Mo
Emissions
Before
Controls
(tons/yr)

65
6
83

906

1,740

622
803

Nil


184
15
126
5
0
Estimatec
Level of
Emissions
Control

0
0
0

98. 8Z

98%

90%
99.9%

Nil


787.
997.
787.
78%
-
j Mo
Emissions
Following
Controls
(tons/yr)

65
6
83

11

35

62
1.0

Nil


41
0.1
28
1
0
00

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                                               TABLE  I  (cont.)
Source
NON-METALLURGICAL USES
INADVERTENT SOURCES
Coal burning
Oil combustion
Mineral Processing
TOTALS
Uncontrolled
Particulate
Emission
Factor ,

2
NA
HA
NA

1
NA
NA
NA
Reliability
Code
D
Production
Level
(tons/Yr)
1,861
33,800,000
(uncontrolled
emissions)
287,000
(uncontrolled
emissions)
6.9 x 106
(controlled
emissions)
	
% Mo in
Emiss ions
*
.01 (B)
.01 (C)
.00023 (D)
Mo
Emissions
Before
Controls
(tons/yr)
2
3,380
29
16
7,179
Estimated
Level of
Emissions
Control
0
82%
0
NA
86%
Mo
Jmissions
Following
Controls
(tons/yr)
2
610
29
16
990
NOTE:   NA = Not Applicable




        Emission factor multiplier equal to tons  of  Mo processed annually

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           2.   Level of Production Activity
                This column depicts the quantity of material produced
 (unless otherwise stated) annually.  When multiplied by the emission
 factor an estimate of the total particulate emissions for that source in
 Ibs  per year is obtained.
                The values in this column are based on the material
 flow calculations presented in Section II.  Consequently, they have the
 same accuracy as those material flow values which is estimated at + 10%.
           3.   Percent Metal in Emissions
                The method of analyzing or assaying a dust sample for
 the amount of metal it contains determines to a large extent the
 reliability of the data.  For example, analytical chemistry techniques
 for dust containing substantial fractions of metal can be accurate to
within a small percentage.  On the other hand, optical spectroscopy
methods for determining concentrations on the order of parts per
million can be inaccurate by a factor of 2.  Because of this variability,
 the reliability codes discussed above for the emission factors are
 also utilized to estimate the relative accuracy of the percentage
 values listed in Column III.
           4.   Level of Emissions Before Control
                The values in this column are derived by multiplying
the values in columns 1-3.  The result is converted to tons/year of
emissions before control.
           5.   Estimated level of Emission Control
                The overall effectiveness of control for a source
category is based on two factors:
                      the portion of the  processes which
                      are under control
                      the typical degree  of control
 For example if 60% of vertical roasters have some type of particulate
 emission control, and these include both  scrubbers and precipitators
                                10

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such that the apparent weighted average efficiency of control is 85%,
the overall control effectiveness is estimated to be 60 x 85 = 51%.
               The accuracy of control efficiency data varies with the
degree of control.  For a wet scrubber operating at 80% efficiency,  i.e.
passing 20% material, the actual emission may safely be assumed to be
between 15 and 25% because of the relative ease of making determinations
at this level.  Thus the emissions after control may be assumed to be
accurate within + 5/20 or 25%.  On the other hand, for a baghouse
reported as being 99% efficient, or passing only 1% of the material, the
actual emission may vary from 0.5 to perhaps 2% because it is
frequently difficult to make low-level measurements with accuracy.  In
such case, the resulting emission data could be in error by a factor
of 2.
               Unless otherwise specified, it is assumed that the
reported overall  level of particulate control applies equally to all
molybdenum-containing particles, independent of size, resistance and
other important collection parameters.  This assumption results in a
correct estimate of molybdenum emissions after control when the parti-
culate is chemically homogenious, i.e. molybdenum  is contained  in the
same concentration  in all particles.  If however, molybdenum  is con-
centrated in  certain particles and  in addition the efficiency of the
control equipment  is not uniform for all particles,  then the
utilization of an average control level is less valid  for  calculating
molybdenum emissions after control.  Data on  the preferential control
of molybdenum-containing particles  is  seldom  available, but  is  included
in this report when possible.
               The  accuracy  of estimating the  level  of  control  for  a
specific source category is  dependent  on  the  quality of available data.
The  investigators  feel that,  in  general,  the  level of  control data
will contribute  an accuracy  to the  resulting emission estimates within
+ 25 percent.
           6.  Level of Metal Emissions After Control
               The  values in this column  are  derived by multiplying
                                11

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 the values in Column 4 by the value  (100 minus estimated Level of
 Control).

        B.  DEVELOPMENT OF EMISSIONS ESTIMATES - 1970
            Estimates of particulate emissions containing molybdenum
 in the U. S.  atmosphere are developed in the following paragraphs and in
 Table 1.  The Table indicates that a substantial portion of the
 emissions is  due to inadvertent sources, i.e. those not directly a
 part of the molybdenum industry.
                Molybdenum ore is presently recovered from mines as a
 major ore and as a byproduct or co-product from copper,  tungsten and
 uranium mining.   The only significant sources of ore are the
 molybdenum and copper mines/ >3^   The ore is presently recovered by
 both open-pit and underground methods.   The portion  of production from
 each method  shifts significantly from year to year and present  trends
 indicate an  increase in  open-pit excavation in the future.
                In 1970,  of the 55,676 tons of molybdenum contained in
 concentrate  mined,  24  percent (13,000 tons)  is estimated to have come
 from non-copper  open pit  mines,  46 percent (25,986 tons) from underground
 molybdenum mines,  and 30 percent  (16,690  tons)  from open pit copper
 mining.   The emission  factors used in Table  1  are based  on  emission
 factors  for  other similar operations^  The  resulting estimate  is that
 154  tons  of  molybdenum were  released  by mining of all  types  in  1970.
           2.  Beneficiation  Operation
               Due  to the  low concentrations of MoS   in  the  ore
 (0.37o average),   beneficiation to a concentrate is necessary before
 comsumption.  The operations  involved include  crushing,  grinding,  classi-
 fication, flotation, filtration and drying.  Recovery from copper  ore
 is generally of the same nature; however, different  flotation agents are
used due to  the necessity of  also maximizing the recovery of the copper.
Recovery from ore generally runs between 70 and 90 percent although
recovery from copper ore has been reported as  low as  50 percent.  The
                                12

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concentrate itself is about 98 percent MoS^  Although no data were
found on emissions from beneficiation, the general procedures are wet,
except for material handling, crushing, and drying.  Emissions from
handling and crushing are frequently estimated for other industries at
2 Ibs/ton of feed and, in the case of molybdenum, are estimated to be
controlled at 95 percent.(4)  The same identical emission factor can be
reasoned to yield Ibs. of molybdenum emitted per ton of molybdenum
produced, assuming the emitted particles contain the same concentration
as the feed.  Emissions from drying processes in other industries are
generally on the order of 50 Ibs. per  ton   of feed and are typically
well  controlled at about 99 percent.(4)  The resulting emissions  for
handling and crushing are 50 tons and  for  drying 1240 tons.   After con-
trol, emissions are  estimated at 15 tons/yr.
           3.  Roasting Concentrate
               Virtually all MoS  concentrate is roasted  to  the  oxide
before consumption.  A minor amount is purified  and  used  as  a lubricant,
but  neither  the quantity of material  not  the estimated emissions  are
 significant.   All  roasting  in  1970 was accomplished  by multiple  hearth
Nichols-Herschoff  furnaces,  although  more  recently these  are being
 replaced by  fluid  bed  roasters  in  the copper  industry.   The  latter
method will  be expected  to  generate more  emissions until  the point of
 control.
               An emission factor  of  168  Ibs.  of particulate per ton of
 metal is  reported  for multiple hearth furnaces  in the copper
 industry(4)  which is equivalent to 100 Ibs. of molybdenum per ton of
 molybdenum,  assuming the particulate  is  MoS2-   Since approximately
 34,821 tons  of molybdenum in concentrate form was roasted, this gives
 an emission of 1,740 tons before control.  Reference (4) indicates a
 control effectiveness of 85 percent for copper roasting.  However,
 discussion with the molybdenum industry suggests that a better
 estimate of molybdenum roasting control is 98 percent, producing a net
 emission of 35 tons.
                                 13

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            4.  Ferromolybdenum Production
                Production of ferromolybdenum amounted to approximately
 6,221 tons in 1970, or about 18 percent of the molybdenum consumption.
 Molybdenum oxide is the raw material for making ferromolybdenum.   Two
 processes are in use, electric arc furnaces,  and a silico-thermite pro-
 cess.  For the former, emissions factors and  controls applicable  to a
 variety of ferroalloy production processes indicate typical values of
 200 Ibs/ton  and 80 percent control efficiency.(4^   In the four years
 since these control estimates were made, however,  we believe that the
 level of control for ferromolybdenum production has improved to at least
 90 percent.   For the silico-thermite process,  no information was  found.
 It is suspected  that the process generates substantially more emission
 initially but is enclosed to a greater  extent  and  under better emission
 control.  It  is assumed that 200 Ibs/ton  and 90  percent control apply
 effectively  to the  entire ferromolybdenum production,  giving an
estimated emission  of 70 tons after control.
               Slag from some ferromolybdenum  furnaces is  crushed,  a
 process  which produces some emissions.   In one instance,  the material
 is  crushed to 320 mesh (about 50 microns)  with a substantial portion  of
 the material  finer  than this.   The  material is dry,  and  is  used for
 landfill.  The molybdenum content of slag,  and emissions  factors, were
not available. This  source  is assumed to  be of negligible  consequence
relative  to  the major  sources listed in Table  1.
           5.  Molybdenum Metal  Production
               About 2.3  percent of  the roasted concentrate  was used  to
produce metallic molybdenum.  Two processes were used, the more common
being the reduction of MoS2  in a hydrogen atmosphere.  The molybdenum
sublimes and  is carefully collected  as a  fine power.   It is  subsequently
sintered in various forms for ultimate use.  The second process pro-
duced a higher purity metal,  by reducing ammonium molybdate  in an
electric furnace.  An emission estimate was made by assuming that 100
percent of the material is emitted initially,  and that control is an
                                14

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excellent 99.9 percent.  This results in an estimated 1.0 ton  of
molybdenum emitted to the atmosphere.
           6.  Chemical Molybdates Production
               About 3 percent of the roasted concentrate was used to
produce compounds of molybdenum.  The production of sodium molybdate and
ammonium molybdate is  accomplished by dissolving molybdic oxide in
either sodium hydroxide or ammonium hydroxide, precipitation, recrystal-
lization and drying.  Calcium molybdate is produced by mixing pulverized
limestone with molybdic oxide to produce a product analyzing 46.3 to
46.6 percent molybdenum.  Mo emissions primarily would be from handling,
and are assumed to be negligible.
           7.  Steel and Alloy Production
               About 57 percent of the U. S. molybdenum was consumed
in the production of steel, cast iron, and various alloys (Figure 1).
The emissions from these processes have apparently not been analyzed in
in any detail for molybdenum content, however.  One approach to making
estimates is to assume that the emissions will contain the same per-
centage of molybdenum as the feed.  This is partly justified by the
fact that the vaporization temperature of molybdenum is at least 3700 C,
far above the operating  temperature  of  all  types  of  furnaces with the
possible exception of an electric arc furnace.  This means that
molybdenum should not be concentrated in the emission particulate.
There is no apparent reason for the particulate to be low in molybdenum
content, either.  Therefore, it is assumed that the emission factor of
pounds of molybdenum per tons of molybdenum feed, is the same as the
emission factor of pounds of particulate per ton of steel, alloy, etc.,
produced.   These are given in Table 1 along with control  effectiveness
factors for the various processes.  The total emission estimate after
control is 70 tons, of which steels and super alloys are estimated to
be responsible for the greatest proportion as shown in Table 1.
           8.  Non-Metallurgical Uses
               About 8 percent of all molybdendum is used for pigments ,
                                 15

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 catalysts, and other chemical and ceramic purposes.  Emisssions from
 these sources are believed to be almost entirely from material
 handling.  Using a typical emission factor of 2 Ibs/ton, the emissions
 are shown in Table 1 to be negligible.
            9.  Inadvertent Sources
                a.  Coal Combustion
                    Coal consumption in 1970 amounted to about
                  (12)
 517,000,000 tons.      The particulate generated has been estimated at
 33,800,000 tons of which 82% was controlled.^  The concentration of
 molybdenum in coal ash has been reported as 0.011 percent (73 samples of
 Appalachian coal ash, spectrographic  analyses),^  as 0.003 percent
 (13 samples of coal ash,  semi quant a tive determinations)^  and as  about
 .002 percent (17 samples  of flyash).(8'  The weighted average is about
 0.01 percent,  resulting in a  net molybdenum emission after  control of
 610 tons.
                b.   Oil  Combustion
                    The  concentration  of molybdenum  in residual oil ash
 has  been  reported  as  0.00093  (at least  3 samples  of ash)^  and as
 0.025  (two  samples  of ash),       giving an  average  of about  0.01 percent,
 the  same  as  for  coal.   (See also Reference  11  for variations.)   An
 estimated 287,000  tons  of  oil ash particulate  is generated^  which is
 practically not  controlled.  This results is an estimate  of  about  29
 tons of molybdenum  released to  the atmosphere.
               c.   Non-Ferrous Minerals
                   A  large quantity of  rock, cement,  fertilizer, clay,
 and  lime dust  is released  into the atmosphere  in the  U. S.,  estimated
 to be 6,900,000  tons  after control.  No  data on the concentration  of
molybdenum in  these dusts has been found, however.  The earth's  crust
 is estimated to contain about 2.3 ppm of molybdenum/11^  If this  con-
centration applies to the mineral emission above, 16  tons of molybdenum
would be the estimated emission. This first approximation is included
 in Table 1.
                                16

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      C.   SUMMARY OF PRINCIPAL EMISSIONS
           Table 2 summarizes the major sources and estimated emissions
of molybdenum,  as developed in Table 1 and accompanying discussion.
The sources are grouped in two categories; those directly originating
with the molybdenum industry or industries using molybdenum, and those
having no relationship to the molybdenum industry, called inadvertent
sources.  Due to the content of molybdenum in coal, the latter
category is larger.
           These prinicpal estimates are examined further in later
sections of this report.

                                TABLE 2
      SUMMARY OF PRINCIPAL SOURCES AND EMISSIONS OF MOLYBDENUM
Inadvertant Sources
Coal combustion
Molybdenum Industry Sources
Mining, copper open pit
Mining, Molybdenum open pit
Ferromolybdenum production
Steel production using Molybdenum
Roasting concentrate

U.S. Tons /year of Mo.
610

83
65
62
41
35

% of U.S.
61.6

8.4
6.6
6.3
4.1
3.5
90.5
                                  17

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  IV.   REGIONAL DISTRIBUTION OF PRINCIPAL SOURCES AND  EMISSIONS
       For purpose of showing geographical distribution,  the U.S. was
  divided into ten regions  identical  to  the Regional Branches of EPA:

       Region                     State
        I             Conn.,  Me.,  Mass.,  N.H., R.I., Vt.
        II            N.J., N.Y.,  P.R., V.I.
        HI           Del., Md., Pa., Va., W.Va., B.C.
        IV            Ala., Fla.,  Ga., Ky.,  Miss., N.C.,  S.C., Tenn.
        V             111., Ind.,  Mich.,  Minn., Ohio, Wis.
        VI            Ark., La., N.M., Okla., Texas
        VII            Iowa, Kans., Mo., Nebr.
        VHI           Colo., Mont., N. Dak., S. Dak., Utah, Wyo.
        IX           Ariz., Calif., Nev., Hawaii and the So.  Pacific
        X            Alaska, Idaho, Oreg., Wash.

      Emissions from  the principal emission sources listed in Table 2 are
 distributed among these ten regions, as shown in Table 3. Also,  the
 number of plants producing the emissions  is  shown in the table when  such
 information was available.

       The accuracy of the  distribution   by region varies with the
 category.  The number of plants per  category varied  from 1 to several
 thousand in this  study.  When the number of plants was less  than
 100,  an attempt was  made to  identify each plant and plant location,  and
 include it  in one of the ten regions.  When production or capacity
 figures for  these plants were  available,  total production or capacity
 for each region was  computed,  and the U.S.  emission estimate for that
 category was  distributed by region accordingly.  When  production or
 capacity  figures were not available,  the emissions were  distributed by
 the number of plants  in  each region.   If  the number of  plants was very
 small or there was reason to believe  that certain plants were larger  or
produced more emission, distributions were weighted accordingly.
                                18

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     When the estimated number of plants was  greater  than 100,  and  the
distribution of plants was not known,  the regional breakdown was  made
on a different basis, such as population, geographical area, or
shipments reported as most appropriate for that category.
Whether the distribution was by plant size, number of plants,  or  another
statistic, the distribution is believed to be accurate to within  10
percent in most cases.
     The emission estimates listed in Table 2 are distributed  in Table 3
on the following basis:
          Coal combustion:  proportional to coal shipped
            by state  of destination
          Mining, copper  pit:   14 mines, assumed to have
            equal emissions
          Mining, molybdenum  open pit:   two mines, assumed
            to have  equal emissions
          Ferromolybdenum:   five companies at  five locations,
            assumed  to have  equal emissions
          Steel  production:   41 companies  producing
            molybdenum alloys,  and  stainless and  tool
             steels  containing molybdenum;  assumed to
            have equal emissions
          Roasting  concentrate:  nine companies at nine
             locations, assumed  to  have equal  emissions.
      The overall distribution of emissions by  region is shown in Table
 3, along with the distribution of plant sources.   Region 5  is estimated
 to have the largest total emission  of molybdenum, followed  by Region 3
 (approximately that area bound by Pennsylvania, Virginia, and Illinois).
 However, this appearance is partly  due to the large  amount  of molybdenum
 emitted with coal flyash.  In the absence of this large source,  Region
 9 (mostly in Arizona) would be estimated to produce  the largest  emission,
 with Region 3 next.
      Considering the geographical areas of these regions, Region 3
 has the most concentrated emissions, with .0019 tons of molybdenum
 emitted to the atmosphere per  square mile-yr.
                                  19

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S3
o
                                                        TABLE 3

                               REGIONAL DISTRIBUTION OF PRINCIPAL SOURCES AND EMISSIONS
             r
              Principal Sources
              Inadvertent
              Sources
                Coal Burning

             Molybdenum
             Industry Sources
Mining,  Copper


Mining, Molyb.


Ferromolyb.


Steel Prod'n


Roasting



     TOTAL

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V.    NATURE OF EMISSIONS
      Very little data describing the physical or chemical properties of
the molybdenum-containing participate were obtained.  Some deductions
regarding the probable character of the emissions may be drawn from the
physical properties of molybdenum and its compounds which are presented in
Table 4 and Figure 2.
                                TABLE 4
          PHYSICAL PROPERTIES OF MOLYBDENUM AND COMPOUNDS
                                                         (*)
1
Melting Point
Boiling Point
Density
Atomic Weight
Heat of Vaporization
Hardness (Std.
Miner o logy Scale)
Mo lybdenum
2610 °C
5560 °C
3
10. 2 grams /cm
95.94 a.w.u.
128 kg-cal/g-atom

--
Mo^0?
(sublimes)
1155 °C
--
240 a.w.u.
--

™ ™
MoS0
(sublimes)
450 °C
	
160 a.w.u.
— —

. 2
* Perry's Chemical Engineers Handbook, 4th Edn, Table 3-169 (Ref. 17)
       For  example,  flyash is  the  result  of  combustion temperatures  in
 the  vicinity of 1700°C.   The  metal  molybdenum begins  to  oxidize  above
 20°C in air, and at 600°C oxidizes  rapidly  to Mo03  especially in the
 presence of  SO-.  Thus  it is  doubtful  that  any molybdenum in elemental
 form is released in the  combustion  of  coal.   The oxide and the
 sulphide forms sublime well below the  combustion temperature of  coal,
 and  consequently may be  expected  to be released either as extremely
 small particles or molecules  of oxide  or sulphide;  or as condensed  thin
 layers on  the surface of other larger  flyash particles.
       Molybdenum in sulphide form is mined   in extremely small concen-
 trations.   Dust emitted  in mining is expected to consist of the
                                  21

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                                                                   FIGURE  2

                                                                VAPOR  PRESSURE  OF
                                                              MOLYBDENUM IN VACUUM
                                                                     versus
                                                                  TEMPERATURE
                  i:8  3.0 2.2  2.4  2.6  2.8  3.0
                      . V'  I     I    't' "   I  ' «•  Temperature
                     * *- 2.«  2.25  2.5  2.75     T .  .3
                                                   CxlO
APPLICATIONS OF MOLYBDENUM
POWDER

   (1) Spray metallizing
   (2) Glass to ceramic seals
   (3) Alloy additions
   (4) Specialized melting techniques

PRESSED AND SINTERED INGOTS

   (1) Machined parts
   (2) Forged parts
   (3) Consumable vacuum arc-cast
      electrodes
   (4) Contact disks
   (5) Alloy additions
   (6) Special forms such as rings,
      boats, etc.

SHEET

  (1) Heat radiation shields
  (2) Arch supports for high-tempera-
      ture furnaces
  (3) Boats for heat treating and
      process  equipment
  (4) Stamped,  deep drawn and spun
      parts, anodes and other
      elements  for electronic tubes
  (5) Stampings  for semi-conductor
      application
  (6) Aircraft  and missile structural
      and  surface  parts
  (7) Electronic tube cathode sleeves
 ROD
   (1) Electronic  tube  leads  - where glass
      to metal vacuum  seal required
   (2) Internal supports  for  vacuum tubes
   (3) Contact disks for  "make or break
      circuits"
   (4) Machined parts
   (5) Welding electrodes
   (6) Electrodes and stirring rods in
      glass manufacture
WIRE
  (1) Grid and internal supports for
      electronic tubes
  (2) Support parts in lamps (hook and
      anchor wire)
  (3) Mandrel for winding tungsten coils
  (4) Wire cloth
  (5) Furnace heating elements
  (6) Thermocouples
  (7) Spray bonding bearing and heat
      resistant surfaces
  (8) Electrode wire for glass to metal
      seals
                                     22

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common rock with included or attached  MoS2>   Since  the  sulphide  is  soft,
it is not expected to fracture to fine particles.   Possibly  for  this
reason most of the dust emitted in mining will consist  of  rock,  with
most of the MoS2 remaining behind in larger particles.
     In the production of ferromolybdenum, and in the production of
steel alloys containing molybdenum, the comments made above  in discussing
the combustion of coal are partly applicable.  However, oxygen and sul-
phurous gases are relatively deficient in these metallurgical operations,
and molybdenum is less apt to oxidize and then sublime as  a  fume.  It
is more probable that particulate emitted from these processes will
contain entrapped molybdenum in metallic form.  The molybdenum will
partially oxidize following emission, and remain relatively stable as
an oxide.
     Roasting operations,  at temperatures up to about  700 C, must
produce some MoS2 fume since the concentrate material  begins to  sublime
at about 450°C.  Probably  a portion of these fumes will oxidize
following emission.  Thus, particulate emissions from  roasting
operations  are expected to consist of submicrometer particles in both
the sulphide and oxide forms.
      One other  source  of emissions, developed in Table 1 but excluded  in
the  list of principal  sources,  is  oil burning, which produces submicro-
meter and micrometer sized particulate.   A substantial portion  of  the
nation's sub-micrometer  particulate containing molybdenum may be expected
to  originate  in the  combustion of  residual oils.
      Submicrometer particulate  and particles up to  a  few micrometers
in  diameter  may be  expected to travel considerable  distances  from the
source before being  deposited or washed out of  the air by natural  pro-
cesses.  Particles of  one  or two micrometers in diameter will behave
almost as  gas molecules  in their mixing and traveling. Thus,  one  would
expect to  find  molybdenum widespread  as a background constituent of  air.
                                                                     (19)
      The air in three  cities has been tested for molybdenum content.
                                                 q
The average concentration was 0.013 micrograms/m .  The particulate
 containing the  molybdenum had an average diameter  of 1.16 micrometers,
                                  23

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and  the distribution of sizes followed a normal aerosol distribution.
About 70 percent of the particulate was contained in particles less than
2 micrometers.
       Molybdenum may be a moderately toxic material, although, at present,
the  evidence is not well developed.  It is reported that cattle in the
vicinity of a western molybdenum plant were recently found to be
suffering from an unusual ailment, and a cause-and-effect relationship
was  implied.    Flyash which explicitly contained molybdenum was found
to be a useful soil additive in growing alafalfa, although the benefit
was more likely the change of pH in the soil than due to the molybdenum^
                              24

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VI.   UPDATING OF EMISSIONS ESTIMATES
      The following recommendations are made for periodically updating
the estimates made in this study:
      A.   VERIFICATION OF CURRENT ESTIMATES
           1.   Verify that the principal molybdenum processes, the
roasting of concentrate and ferromolybdenum production, are adequately
represented by these estimates.  If possible, emissions data should be
obtained from the molybdenum industry rather than by extrapolation
from other processes believed to be similar  because of the individual
nature of molybdenum and its compounds.
           2.   The production of steel alloys containing molybdenum
as an alloying ingredient  should be investigated  to ascertain that
the emissions of molybdenum are in fact proportional to the feed of
molybdenum.  Steel production is a potentially large source of
molybdenum emission, if the emission factor should  in  fact be  larger
than assumed.
           3.   Crushed rock, lime, clay,  fertilizer,  and cement dusts
are of sufficient quantity that even slight molybdenum content could  be
 significant.   Typical  analyses  of  these dusts  should be made  for  moly-
 bdenum content to  verify  that  the  content  is  in  fact as low as assumed.
      B.   PERIODIC REVIEW OF ESTIMATES
           1.   The Bureau of Mines estimates  for material flow,
industry practices, and trends  provide the best  estimates of  the  size
of the  industry.
           2.   EPA activities  are currently  generating the best
emissions data and should  be reviewed  using:
                a.  Overall  industry studies,  e.g.  Reference  (4).
                b.  The Source  Test Program,  in  which  specific
individual plant emissions are  measured.   This  information  provides
                                  25

-------
  emission factors  for  specific  examples  of  typical, industrial  operations
  and also provides  some  analyses  of  the  particulate,usually  including
  trace metal  content and particle size.

                 c.  NEDS  (National  Emissions Data System) is  steadily
  being enlarged and improved.  This  system  can provide emission factors
  for  specific plants and  plant operations,  the type of particulate con-
  trol equipment in use,  and the actual, or  estimated, control efficiency.
  The  system may eventually be expanded to include description of the
  emissions.

            3.   The molybdenum industry  should be consulted for its
 opinion and suggestions  on the most  recently published estimates.   This
 may be best accomplished by interviewing the Molybdenum Commodity
 Specialist, Division of  Non-ferrous  Metals, Bureau of Mines  in
 Washington; or  by  interviewing one or more  of the principal  companies
 in the  industry.

            4.   The literature  should be reviewed,  using (a)  industrial
 views as  published  from  time  to time in  Chemical  Engineering  for
 example,  and  (b) evironmental views  as summarized in  Pollution Abstracts.
 for  example.                                                      '~~

            5.   Individual companies  or  plants may be approached for
 opinions,  data, or cooperative tests  of  their  own operations.  This  is  a
 difficult  approach to the problem of  obtaining fresh information due to
 the natural reluctance of the plants  to discuss environmental problems.
 However, data thus obtained have a relatively high degree of reliability.

           6.   State agencies in which specific plants are located may
be able to provide  useful information, and should be contacted.
                                 26

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                                REFERENCES

1.   Preprint from Minerals Yearbook, Molybdenum, U. S. Bureau of Mines,
     Washington, D. C.  (1971).

2.   Mclnnis, Wilbur, Molybdenum:  A Material Survey. U. S. Bureau of
     Mines  Information  Circular IC7784, Washington, D. C.  (1957).

3.   Economic Analysis  of  the Molybdenum Industry,  Charles River
     Associates, Inc.,  Cambridge, Mass.  (1967).

4.   Vandegrift, A. D.,  et. aL, Particulate Pollutant  Systems  Study.
     Vol  I,  II,  III,  Report by Midwest Research  Institute, St. Louis,
     Mo.,  to EPA, Contract No. CPA 22-69-104, May 1971.

5.   Personal Communication with members of the  Molybdenum Industry.

6.   Zubovic, P., et.  al., Distribution  of Minor Elements  in Coate of  the
     Appalachian Region. Geological  Survey Bulletin No.  1117-C, U.  S.
     Bureau of  Mines,  Washington, D.  C., 1966.

7.   Kessler, et. a.,  Analysis of Trace  Elements in Coal by  Spark-
     Source Mass Spectroscopy. Bulletin  No. 7714, U.  S.  Bureau of Mines,
     Washington, D.  C., 1971  Approx.

8.   Doran, J.  W.,  and Martens,  D. C.  "Molybdenum Availability as
     Influenced by  Application of Fly Ash  to  Soil,"  J.  of
     Environmental  Air Quality. 1 (2)  186 April-June  1972.

9.   Levy, A.,  et.  al., A  Field  Investigation of Emissions from  Fuel  Oil
     Combustion for Space  Heating, Report  by  Battelle Inst.,  Columbus,
     Ohio to American Petroleum  Institute,  API Proj.  SS-5, 1 Nov. 1971.

10.    Smith, W.  S.,  Atmospheric Emissions from Fuel  Oil Combustion,
      999  AP-2,  U.  S.  Dept. of H.  E.  W.,  1967.

11.   Fairbridge, R. W., ed.,  The Encyclopedia of Geochemistry and
     Environmental  Sciences  Series,  Vol. IVA. Van Nostrand Reinhold Co.,
     N. W., 1972.

12,   Minerals Yearbook. U. S. Bureau of Mines, Washington, D.  C., 1967
      1968, 1969, and 1970.

13.    Charles River Assosciates,  Inc., Cambridge, Mass., Economic Analysis,
      of the Silver Industry.  Report  to the General Services Administration
     Wash., D.  C.  Contract No.  GS-OO-DS (P)-85005,  WA 68-22, Sept. 1969.

14.    Gousseland, Pierre, Molybdenum, Engineering and Mining Journal,
      p.  153-156 (March 1972).
                                27

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15.  Personal Communication, Molybdenum Commodity  Specialist,  Division  of
     Non-ferrous Metals, U. S. Bureau of Mines, Washington, D. C.,  1973.

16.  Alloys Digest, a series of descriptions of individual products and
     manufacturers, pub. since 1952, by Engineering Alloys Digest  Inc
     Upper Monclair, N.  J.                                             ''


17.  Perry. R. H., ejL. al,, Perry's Chemical Engineers Handbook. 4th
     Edition, McGraw Hill, Inc., New York, 1963.

18.  Philips Elmet Corp., Lewiston, Maine, a brochure or report
     containing descriptions of Molybdenum and Tungsten properties and
     uses.
19.   Lee, R. E., et. al., "Molybdenum Particle Sizes" in Environmental
     Science and Technology 6. (12) 1025 Nov. 1972.       	
                               28

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                                   TECHNICAL REPORT DATA
                            (Please read Instructions on the reverse before completing)
 REPORT NO.
    EPA-450/3-74-009
                             2.
                                                            3. RECIPIENT'S ACCESSION-NO.
 TITLE AND SUBTITLE
    National  Emissions Inventory of Sources  and
    Emissions  of Molybdenum
              REPORT DATE
               May 1973
            6. PERFORMING ORGANIZATION CODE
 AUTHOR(S)
                                                            8. PERFORMING ORGANIZATION REPORT NO.
 PERFORMING ORGANIZATION NAME AND ADDRESS
    GCA Corporation
    GCA Technology Division
    Bedford,  Massachusetts 01730
                                                            10. 1
               ?AF132
             11. CONTRACT/GRANT NO.


               68-02-0601
 2. SPONSORING AGENCY NAME AND ADDRESS
    Environmental Protection Agency
    Research Triangle  Park, N. C.  27711
             13. TYPE OF REPORT AND PERIOD
                Final
             14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
          A national  inventory of  the sources  and emissions  of the element molybdenum
    was  conducted.   All  major sources of molybdenum-containing emissions  were iden-
    tified and their molybdenum emissions into  the atmosphere estimated.   Also, a
    method for updating the  results of the  study every two  years was  recommended.
17.
                                 KEY WORDS AND DOCUMENT ANALYSIS
                   DESCRIPTORS
                                                IDENTIFIERS/OPEN ENDED TERMS
                                                                              COS AT I Field/Group
     Molybdenum
     Air Pollution
     Emission
     Inventories
     Sources
13. DISTRIBUTION STATEMENT
     Release Unlimited
19. SECURITY CLASS (This Report)
      Unclassified
                                                                                 27
20. SECURITY CLASS (Thispage)
      Unclassified
                                                                            22. PRICE
EPA Form 2220-1 (9-73)
                                               29

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        Insert the total  number of page^ including this one and unnumbered pages, but exclude distribution list, if any.

    22.  PRICE
        Insert the price set by the National Technical Information Service or the Government Printing Office, if known.
EPA Form 2220-1 (9-73) (Reverse)


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