-------
TABLE 3-5
SAMPLE CALCULATION OF SCRUBBER EFFICIENCY
Data
Computation
I.
II.
III.
IV.
V.
VI.
VII.
[Cl~] = 25%
feed rate - 2000 Ib/hr
See Table 3-3
A = 3.12 ml
N - .01
Vj = 40 ml
Vs - 10 ml
"6
Cl = 9.74 x 10 D Ib
Sample Volume 33.17 dscf
See Table 3-3
Q * 86,960 scf/min
[from Step IV in Table 3-1]
Ccl - 2.94 x 10"7 Ib/scf
Clin - 8.33 Ib/min
[Step I]
Clout = 0.0255 Ib/min
[Step VI]
Clin = (.25) (2000 Ibs/hr)
= 500 Ibs/hr
- 8.33 Ib/min
33.17 dscf
mg C
- 35.45(3.12)(.01)(40)
10
- 4.43
= 9.74 x 10~6 Ib
9.74 x 10"6 Ib
33.17 dscf
- 2.94 x 10~7 Ib/scf
86,980 scf/min
Clout - (86,980 scf/min) x
(2.94 x 10~7 Ib/scf)
- 0.0255 Ib/min
SE = 8.33 Ib/min - 0.0255 Ib/min x 100
8.33 Ib/min
99.69%
3-15
-------
presented in Table 3-5, if the scrubber efficiency was 98.81
percent, the value of Cl would be four times greater. The
value of 98.81 percent may not be rounded off to 99 percent and is
not in compliance with the regulatory performance standard.
If the scrubber efficiency is less than 99 percent when
hydrogen chloride emissions are greater than 4 Ib HCl/hr, the permit
writer must notify the applicant that the hydrogen chloride
emissions exceed the regulatory performance standard. The applicant
may provide additional performance data demonstrating compliance
with the standard.
3.5 Particulate Emissions
Incinerators destroying hazardous wastes must not emit
particulate matter at concentrations greater than 180 milligrams of
participates per dry standard cubic meter of stack gas (0.08 grains
per dry standard cubic foot) when the stack gas is corrected to a
7 percent oxygen concentration, using the following formula for the
correction factor specified in 40 GTB. 264.343(c):
14
Correction Factor «
Where: 7 - measured oxygen concentration in the stack gas on a
dry basis.
The measured particulate concentration is multiplied by the
correction factor to obtain the corrected particulate emissions. A
sample calculation of particulate matter concentration in the stack
gas using the method referenced in the Sampling and Analysis
3-16
-------
(3")
Manual is presented in Table 3-6. The calculation involves the
following steps:
Determination of the stack gas sample volume
Determination of weight of collected particulate matter
Calculation of particulate concentration in the stack gas
Determination of the oxygen concentration in the stack gas
Correction of the measured particulate concentration
Particulate emission calculations are sensitive to the values
of oxygen concentrations, and the permit writer may check that these
values are obtained properly. If the oxygen concentration was found
to be 10.0 percent instead of 8.0 percent in the sample calculation
presented in Table 3-7, the particulate emissions would increase to
0.096 grains per dry standard cubic foot. Thus, the particulate
emissions at 8.0 percent oxygen concentration are in compliance with
the performance standard and the emissions at 10.0 percent oxygen
concentration are not. Orsat analysis for the oxygen content of the
flue gas is satisfactory and should be reported on a dry basis.
Rather than follow the procedure presented in Table 3-6, an
applicant may submit particulate emission monitoring data from an
in-stack instrument in order to demonstrate compliance with the
performance requirements. The permit writer should determine that
such instruments are properly calibrated and are functioning
properly. Instrument calibration data should be submitted by the
applicant for this purpose. The permit writer should be aware that
continuous particle emission monitoring equipment must operate near
3-17
-------
CO
O
CO
CO
X
w
w
H
^3 (^<4
en 3
S M
3 £
C^
2?
w
i
M
Ei
^5
5*
co
e
c
«
3
a.
s
o
u
eg
4-1
eg
4)
i-i
3
a.
41
4J
/}
41
44
CO
4)
41
CO
latlon
a
y
eg
y
Q
co
eg
CO
O
41
iH
O.
§
«*
CO
(0
eg
u
>-
y
eg
CO
4)
44
3
o.
a
a
>»
fH
eg
y
hi
U
a
H
eg
hi
00
*o
4)
e
^
g
4)
4)
O
JS
00
U 4J
H S
4-1 3
hi ^^
CO O
a. >
^3 CQ
4) CQ
44 00
y
4) .*
i-i y
O 44
y to
*4 N"'
O 4-
44 x-s
J= hi
00 41
«4 XJ
4)
03
hi
^
e
y
O
y
-------
TABLE 3-7
SAMPLE CALCULATION OF PARTICULATE EMISSIONS
Date
Computation
l> Vm(std) = 33-17 dscf
II. Particulate weight *
137 milligrams
(2.113 grains)
III. Particulate weight »
2.113 grains
Stack gas volume »
33.17 dscf
IV. [02] » 8.0%, dry basis
V. P » 0.0637 gr/dscf
See Table 3-3
Gravimetric determination
P - 2.113 grains
33.17 dscf
= 0.0637 gr/dscf
14
21-8
1.077
(0.0637)(1.077)
0.0686 gr/dscf
3-19
-------
its sensitivity limit in order to detect 180 mg/dson. Equipment
response is dependent upon particle size distribution and particle
color and requires calibration for each different waste fed to an
incinerator.
If the corrected particulate emissions are greater than 180
mg/dscm (0.08 gr/dscf), the permit writer must notify the applicant
that particulate emissions exceed the regulatory performance
standard. The applicant may provide additional performance data
demonstrating compliance with the standard.
3-20
-------
4.0 SPECIFICATION OF PERMIT CONDITIONS
The permit writer must designate a set of operating require-
ments specific to each waste feed which the applicant indicates
will be burned. These requirements must reflect the set of con-
ditions which have been shown to achieve the performance standards
of 40 CFR 264.343, either during a trial burn conducted in the unit
for which the permit is sought, or by data submitted in lieu of
conducting a trial burn. At a minimum., .the permit must specify
requirements for the carbon monoxide level in the stack gas, thermal
input rate,, combustion temperature, combustion gas flow rate, and
acceptable variations in the waste feed composition. In addition,
the permit writer may Include other operating requirements, as
necessary to ensure compliance with the performance standards.
These may include, for example, conditions which may derive from
trial burn results for specific combinations of wastes or alternate
operating conditions to be used under specifically defined circum-
stances. Guidance for specifying each of these requirements is
provided in Sections 4.1 and 4.2.
The permit must also include a schedule for conducting periodic
facility inspections. 'Two types of inspections are required. The
first, a visual inspection of the incinerator, must be conducted
daily. The second type of inspection, testing of the emergency
waste feed cut off system, should occur at either weekly or monthly
intervals. Guidance for determining the best means of testing the
4-1
-------
system and the frequency at which testing should occur is presented
in Section 4.3.
Initially, the operating requirements for new incinerators
will be established on the basis of the incinerator's anticipated
performance capabilities. The requirements will be designated
primarily on the basis of the design specifications provided with
the permit application and experience or information gained from
trial burns at other facilities. These requirements will then be
modified when data from the trial burn is complete and evaluation
of actual incinerator performance can occur. Further guidance
regarding the specification of operating requirements from design
data is presented in Section 4.4.
4.1 Specification of Operating Requirements From Performance Data
An incinerator permit must specify a set of operating require-
ments for the following parameters:
Carbon monoxide level in the stack exhaust gas
Waste feed rate
Combustion temperature
Combustion gas flow rate.
The degree of flexibility inherent to each of these requirements
will be governed by the performance data reported by the applicant.
The trial burn (or alternative) data should include values for
these operating parameters which correspond to the performance
level achieved in the trial burn. Therefore, at a minimum, a set
4-2
-------
of values for carbon monoxide in the stack gas, waste feed rate or
thermal input rate, combustion temperature and combustion gas flow
rate should be reported for a corresponding destruction and removal
efficiency, mass emissions of HC1 and/or scrubber removal efficiency,
and emissions of particulata material.
The applicant should report values for each operating parameter
which include information regarding normal fluctuations. The permit
requirements can be written to incorporate the range identified.
This may be accomplished in several ways- For example, the operating
parameter values may be reported as a range (e.g., 1800 +_ 50°F),
or the applicant may provide the actual readout from the monitoring
instrument which shows fluctuations over time. Submission of readouts
from continuously monitoring instrumentation is recommended.
The maximum amount of information can be generated by testing
each of the operating parameters at several levels during the trial
burn. If each level is reported along with a description of the
fluctuation that occurred, the applicant will have established a
wide range of conditions over which adequate performance is achieved.
Permit conditions for each parameter may be expressed as the ranges
tested successfully during the trial burn. This approach provides
the operator with a high degree of flexibility during routine operation.
4.1.1 Carbon Monoxide Level In The Stack Gas
The amount of CO present in combustion exhaust gas is a function
of many factors, including combustion temperatures, residence time
4-3
-------
of the combustion gases at Che combustion temperature, degree of
mixing of fuel(s) and air, and the amount of air used in excess of
stoichiometric requirements. Thesie factors are interdependent to
some extent; however, residence time and the degree of adzing of
air and fuel(s) are primarily determined by by combustion chamber
and burner design. Therefore, changes of CO concentration will
reflect changes in excess air usage and in combustion temperatures.
The continuous measurement of carbon monoxide (CO) in the
stack gas is useful for several reasons. CO concentration is a
reliable indicator of combustion upset and remains a good indicator
as excess air is lowered toward stoichiometric conditions and as
combustion temperature is lowered. Additionally, carbon monoxide
and carbon dioxide concentrations can be used to determine combustion
efficiency.
Monitoring CO in the exhaust gas is most conveniently done in
the exhaust stack, where temperatures are low. However, measure-
ment of CO at other points in the system is acceptable. For example,
CO may be measured in the take-off ducting immediately after the
combustion chamber or after-burner.
The permit writer should specify, as the maximum allowable CO
concentration, the maximum CO -concentration reported from the trial
burn demonstrating compliance with the performance standards.
However, some allowance for normal variation may be specified in
the permit in order to protect against unnecessary activation of
4-4
-------
the waste feed cutoff system. Following the trial burn, the appli-
cant should submit the actual readout from the CO monitoring device.
This chart will provide data describing the average CO concentration
and the frequency, magnitude and duration of any downward or upward
spikes. Permit conditions that accomodate some degree of fluctua-
tion in the stack gas CO concentration can then be selected on the
basis of this information.
4.1.2 Waste Feed Rate
The waste feed rate may be effectively controlled by stipulating
the maximum total thermal input rate to the incinerator. The permit
writer is encouraged to specify the maximum total thermal input rate
(e.g., Btu per hour) including the heating values contributed by
hazardous waste, non-hazardous waste and auxiliary fuel, in all
permits. In conjunction with specifying the minimum heating value
of the waste feed, control of the thermal input rate will ensure
that the incinerator is not overloaded with difficult to incinerate
hazardous constituents and that compliance with the performance
standards is maintained. Because the total thermal input is derived
from trial burn data, the applicant gains greater flexibility in a
permit by operating at the maximum thermal input than at a lesser
thermal input during a trial burn. Turndown, or reduced thermal in-
put to an incinerator, from the maximum permitted value is allowable
if compliance with the other permitted operating conditions is main-
tained.
4-5
-------
Additional restrictions on the waste feed rate may be imposed by.
specifying a mass or volume feed rate of the waste (e.g., pounds per
hour, gallons per hour) and the total thermal residence times are
maintained in incinerator equipped with multiple feed location and
to limit the amount of waste containing very toxic constituents that
may be fed to an incinerator.
The following example illustrates specification of both the
total thermal input and a mass feed rate.
Tetrachloroethylene is the most difficult POHC to incinerate
present in Waste A. Waste A is successfully incinerated during a
trial burn at a feed rate of 100 Ib/hr, using 100 Ib/hr of auxiliary
fuel. If the heating value of Waste A is 5000 Btu/lb and that of
the auxiliary fuel is 18,000 Btu/lb, the total thermal input is 2.3
million Btu/hr. The permit may be written specifying the maximum
feed rate and minimum heating value of Waste A, and the maximum
allowable total thermal input, 2.3 million Btu/hr for more easily
incinerated wastes. Thus, Waste 3, having heating value of 10,000
Btu/lb and all hazardous constituents easier to incinerate than
tetrachloroethylene, may be fed to the incinerator at rates up to
230 Ib/hr if no auxilliary fuel is burned. Alternatively, the incin-
erator can be operated co-burning 100 Ib/hr of Waste A and 180 Ib/hr
of Waste B to achieve the maximum thermal input of 2.3 million Btu/hr.
The net effect of specifying the total thermal input is to permit
the substitution of easily incinerated waste for auxilliary fuel if
4-6
-------
specified operating conditions, such as combustion zone temperature
and air feed rate, are maintained. Additional examples of specifying
the total thermal input are provided in Chapter 5.
Specification of waste feed as mass feed rate of the POHCs will
generally not be necessary. Such a permit condition would require
frequent analysis of incoming wastes and feed tank blends in order to
ensure permit compliance. The permit limitations on other operating
parameters fix the temperature, residence time and heating value of
the waste, reducing the need for feed rate stipulations based on
mass input of the POHCs.
Waste compositions are specified in a permit for each waste
or waste mix having a different physical state. The permit writer
has the option of developing permit conditions for wastes with the
same physical state, entering the incinerator at the same location,
as separate wastes or as a single waste mix. The physical states of
wastes in the form they enter the incinerator are classified as
pumpable liquids, non-pumpable or solid materials, and containerized
wastes. Pumpable liquids include pumpable slurries and highly aqueous
wastes. Non-pumpable wastes include sludges, tars, and solid materials
having high ash contents. The definition of wastes having different
physical states as separate wastes in a permit is necessary to ensure
adequate volatilization of the hazardous constituents from a waste
prior to flame oxidation. For example, the volatilization of hexa-
chlorobenzene from a liquid solvent atomized in a burner is much
4-7
-------
faster than the volatilization of hexachlorobenzene from a still
bottom tar. Accordingly, the maximum mass loading rate that may
be incinerated in compliance with the performance standards of
the liquid waste is likely to be much greater than that of the
sludge and the permit must take these factors into account.
Waste feed locations are specified in a permit in order to
ensure adequate retention time in the combustion chamber. Waste
feed locations upstream of those used during a satisfactory per-
formance test provide additional residence time in the combustion
chamber and are permitted. Downstream feed locations decrease
residence time and should not be permitted because the DRE may be
lowered out of compliance.
Wastes having the same physical state fed to the incinerator
at the same location may be regarded as one waste in a permit. The
permit writer has the option to consider such wastes a waste mix
and specify the mixed waste composition in a permit. Alternatively,
the composition of each waste stream may be specified in the permit.
The applicant may prefer one of the options and the permit writer
should prepare the draft permit accordingly.
The specification of wastes of different physical form and mul-
tiple feed locations is illustrated using the example in Figure 4-1.
Assuming that all the performance test results are in compliance,
wastes C and D must be defined in the permit separately because the
physical states are not the same. The incinerator charging rate may
4-8
-------
C U
o Ca
00-^
C 3
H U
U S3
C8 *~f
CU
o
0
o
*
o
H
-------
be specified on the basis of total thermal input, or the combination
of thermal input and mass input rates. If mass loading rate is used,
the permit would specify that 600 Ib/hr of waste C having a minimum
heating value of 7000 Btu/lb and a maximum organically bound chlorine
content of 6 percent may be fed to the kiln. 600 Ib/hr of waste D
having a minimum heating valued of 8000 Btu/lb and a maximum organically
bound chlorine content of 10 percent may be fed to the kiln. Speci-
fying the total thermal input, no more than 4.2 million Btu/hr of
waste C and no more than 4.3 million Btu/hr or waste D may be fed to
the incinerator. Wastes C and D must be fed to the kiln and may not
be fed to the afterburner in order to ensure sufficient residence
time.
Wastes A. and B have the same physical state and both are fed to
the kiln. Only Waste A is fed to the afterburner. The waste compo-
sition may be specified in a number of ways. Wastes A and B may
be considered a waste mix entering the kiln (see the example above)
and the total allowable waste fed to the kiln includes the amount of
waste A fed to the afterburner. Waste B may not be fed to the after-
burner. The permit would specify that 1500 Ib/hr of liquid waste
having a minimum heating value of 7400 Btu/lb, and for no more than
11.1 million Btu/hr of liquid waste, having a maximum organically
bound chloride content of 11 percent may be fed to the kiln. Another
option is that Wastes A and B may be considered a waste mix to the
kiln and may include Waste A to the afterburner, if operating conditions
4-10
-------
for the afterburner are stipulated separately. Weighted averages
may be used to establish the heating value and chloride content.
The permit would also specify that 400 Ib/hr of waste A may be fed
to the afterburner with a minimum heating value of 10,000 Btu/lb and
a maximum organically bound chloride content of 15 percent.
The other method to develop the permit is to define wastes A
and B separately at each feed location, using mass feed rate or total
thermal input. Using the mass feed rate for example, 400 Ib/hr or
waste A can be fed to the afterburner, 600 Ib/hr or waste A can be
fed to the kiln, and 500 Ib/hr of waste B can be fed only to the
kiln. Waste A must have a minimum heating value of 10,000 Btu/lb
and a maximum organically bound chloride content of 15 percent.
Waste B must have a minimum heating value of 2000 Btu/lb and a maximum
organically bound chloride content of 3 percent.
^1*3 Combustion Temperature
The permit needs to specify a minimum allowable combustion
temperature. This value should be the minimum temperature shown,
during the trial burn or by alternative data, to correspond with
achievement of the required performance standards. Specification of
a maximum allowable combustion temperature is not necessary because
increased temperatures presumably increase destruction efficiency.
Furthermore,, the maximum temperature at which the incinerator will
be operated is limited by refractory capabilities and other design
4-11
-------
considerations.
In setcing the requirement for minimum allowable combustion
temperature, the permit writer should consider temperature fluctua-
tions encountered during the performance test. The heated refractory
will act to maintain thermal stability and temperature fluctuations
should not be great However, some allowance for normal variations
is needed in order to protect against unnecessary activation of the
waste feed cutoff system as a result of temperature "spiking" (see
Section 4.1.5). Examples of the specification of minimum permitted
operating temperature are provided in Chapter 5.
Consideration must also be given to the location of the tem-
perature sensing device. In many instances, temperature sensors
will be located at several points in the system. The reported
temperature should be measured at the point where the data will be
most representative of the gas temperature as it exits the hottest
part of the combustion chamber. Although the exact location of the
temperature sensor will vary in each case, a location should be
specified in the permit in order to ensure that temperature is always
monitored at the same point in the system during routine operation.
4.1.4. Combustion Gas Flow Rate
Combustion gas velocity is an indicator of the flue gas volume
flow rate, which is a function of thermal input to the incinerator,
gas temperature, and excess air usage. Measurement of combustion
4-12
-------
gas flow rate provides a good indication of residence time in the
combustion zone.
The maximum combustion gas velocity (or exit gas velocity)
shown during the trial burn (or by alternative data) as corresponding
to achievement of the required level of performance should be desig-
nated as the maximum allowable velocity. Specification of a minimum
velocity is not necessary since the required performance should be
maintained at turndown provided that all other operating parameters
are maintained. The permit writer should recognize that incinerators
burning containerized wastes may exhibit sharp momentary increases
in combustion gas velocity ("puffing") upon charging. Such varia-
tions should be incorporated into the permit conditions if sufficient
performance data are supplied.
Combustion gas flow rate may be measured by many different
means. Combustion gas velocities may be measured using orifice
plates or veturis, pitot tubes, or by indirect means. Orifice
plates and Venturis are impractical for combustion gas velocity
measurements because of the large pressure drops caused by these
devices. Pitot tubes may be used to measure combustion gas velocity
in the hot zone of an incinerator immediately downstream of the
combustion chamber or in cooler areas, such as the stack. Pitot
tube measurements can be converted to combustion gas velocity and
volume flow rate using the procedure in EPA Method 2 presented in
the Appendix of 40 CFR 60. Changes in the molecular weight and
4-13
-------
the water content of the combustion gas will affect the correlation
of pitot tube measurements and combustion gas velocity.
Indirect measurements of combustion gas velocity may include
blower rotational speed and current draw. Many blowers operate in
the region of the blower curve where static pressure and current
draw (horsepower) do not change radically with a change in capacity.
Therefore, blower static pressure and current measurements are
generally not suitable indicators of combustion gas velocity unless
the applicant can demonstrate a noticeable correlation. Blower
rpm is indicative of combustion gas velocity and volume flow rate
only if static pressure in the blower remains constant. Measure-
ment of combustion gas velocities using blower characteristics on
incinerators equipped with more than one blower may become very com-
plex, and the problems may be alleviated by use of a pitot tube.
Measurement of pressure differentials across incinerator
components, such as combustion chambers and air pollution control
devices, is not a suitable indicator of combustion gas velocities.
Pressure differentials may be affected by leakage, changes in
liquid flow rates, and clogging phenomena as well as gas flow rates.
It is not possible to distinguish the factors affecting changes in
pressure measurements using conventional equipment. Therefore,
pressure differential measurements should not be used as gas velocity
indicators; however, they are useful monitors for upset conditions.
Continuous monitoring of the oxygen concentration in the stack
4-14
-------
gas is an acceptable substitute for combustion gas velocity measure-
ment. The oxygen concentration is indicative of excess air usage
and, if waste feed composition and feed rate remain constant, it
is an indirect measurement of the combustion gas volume flow rate.
The most common method of continous oxygen measurement is an electro-
catalytic device, and paramagnetic and polarographic instruments
are used. The monitors are either in-situ or extractive. Addi-
tional information about instrument capabilities is presented in
the Engineering Handbook.
4.1.5 The Emergency Waste Feed Cutoff System
The purpose of the automatic waste feed cutoff system is to
shut off waste feed to the incinerator whenever the operating
parameters deviate from the limits set in the permit. For this
reason, the cutoff valve should be interlocked to all of the re-
quired continuous monitoring devices. These devices include moni-
tors of temperature, combustion gas velocity, and carbon monoxide
level in the stack gas. For each of these parameters, the permit
should include a provision that establishes both a range for opera-
tion and a level, somewhat beyond that range, at which the emergency
waste feed cutoff system must be activated. The following discussion
provides an example for proper integration of the waste feed cutoff
system with the combustion temperature monitor. Similar approaches
may be taken for integration with other operating parameters as well.
4-15
-------
Following the trial burn, the applicant should submit the
actual readout from the temperature recording device. This chart
will provide the permit writer with data describing the average
operating temperature and the frequency, magnitude and duration of
any downward or upward spikes* Effective permit conditions can be
selected on the basis of these data. Generally, the permit will
specLry that the incinerator be operated at or above the average
temperature tested during the trial burn. Additionally, the permit
should sperify that the automatic waste feed cutoff be activated
at a lower temperature than the range of normal fluctuation indicated
by the results of the trial burn.
This cutoff temperature may be selected in several ways, each
of which requires some degree of judgment. The automatic cutoff
temperature may be selected by calculating a time-weight'ed average
of the temperatures recorded below the target operating temperature.
Alternatively, the permit writer may select the temperature of the
lowest spike as the automatic cutoff temperature. In this case,
however, a rarely occurring, very large downward spike should be
considered unrepresentative of normal temperature fluctuation and
should be disregarded. The permit condition, might also be written
to establish an automatic cutoff which allows for momentary excur-
sions by specification of allowable excursion magnitude, frequency
and duration. Conceptually, this type of control could best be
accomplished using a system which would limit the total number
4-16
-------
of degree-minutes below a prescribed level before activation of
the waste feed cutoff mechanism. Such a system, however, will not
always be available for use by the operator. The necessary limits
for such a system would vary from case to case. The permit writer
should require that detailed information regarding temperature
fluctuations be provided. When selecting the actual limit on
degree-minutes of deviation, the permit writer should generally
allow deviations to occur for only a small fraction of the total
operating time. This approach is advantageous because it allows
for the possibility of a very large, but rare, downward spike
without activation of the automatic waste feed cutoff.
4.2 Limitations On Waste Feed Composition
Permit limitations on waste feed composition should address
two aspects of the waste: allowable waste constituents and chemical
and physical waste characteristics. The actual limitations selected
for these parameters depends on the results of the trial burn. Per-
mit conditions regarding allowable waste constituents are restricted
to limitations on those substances listed as hazardous constituents
in Appendix VIII of 40 CFR Part 261.
Limitations on the physical and chemical characteristics of the
waste feed may be used, rather than stipulations on allowable POHC
concentrations. Theoretically, incinerator DRE performance is inde-
pendent of POHC concentration, provided that limitations are placed
4-17
-------
on the other physical and chemical characteristics of the waste and
on the incinerator operating parameters. However, in practice, this
approach will be most reliable if the trial burn is conducted using
the largest POHC concent rat ions anticipated during normal operation.
Guidance for selecting limitations on chemical and physical charac-
teristics is presented in this section.
The method described for restricting waste feed composition
has been designed to minimize the burden of time consuming and
complex chemical analysis. This is accomplished by using operating
requirements and restrictions on physical and chemical character-
istics of the waste to ensure adequate performance.
4.2.1 Allowable Waste Feed Constituents
The number and identity of allowable hazardous waste con-
stituents specLfed in the permit will depend primarily on the waste
constituents burned during the trial burn and on their placement
on the hierarchy of incinerability (presented in Chapter 2). The
principle which should govern writing the permit is that allowable
hazardous constituents are those which exhibit higher heat of
combustion values (i.e., those which are easier to burn) than the
POHCs for which the required performance was shown either in a
trial burn or by alternative data. In this way, the determination
of allowable hazardous constituents is derived directly from the
hierarchy of incinerability.
4-18
-------
In practice, this approach allows the applicant to control
the number of hazardous constituents which Che permit will allow
him to burn (and hence, the range of wastes which can be accepted
for treatment at the facility) through careful design of the trial
burn. If a wide range of flexibility is needed, the trial burn
should be conducted using a waste containing significant levels of
POHCs having very low heat of combustion values. The permit would
allow burning of wastes containing constituents which are easier
to incinerate if complianced with the performance standards is
demonstrated.
After successful completion of a trial burn, it is not necessary
that the permit writer automatically allow burning of all constitu-
ents, without regard to their concentration in the waste, which
fall below the trial POHCs on the hierarchy. The permit writer may
deem certain exclusions or restrictions on concentration necessary.
Such restrictions should be considered in cases where a substance
known or suspect ed t o be a hi g'hly pot ent human t oxL cant (e.g.,
2,3,7,8-TCDD) falls below the trial POHC on the hierarchy.
In order to maximize flexibility of the permit conditions re-
garding allowable waste feeds, the applicant may burn a contrived
waste during the trial burn which has been spiked with one or
several POHCs known to be difficult to destroy. In such a case,
the applicant will gain flexibility in terms of allowable hazard-
ous constituents (and, therefore, waste feeds). However, since
4-19
-------
compliance is established at conditions sufficient to destroy the
most difficult POHC to incinerate, the permit will require that
all wastes be treated under these same conditions.^
In cases where a contrived waste is used during the trial
burn, the permit writer should also consider concentration of the
POHCs in the trial waste. The contrived waste should contain
POHCs in concentrations which are representative of concentrations
expected to be found in the actual wastes managed at the facility.
Spiking the trial waste with POHCs in concentrations which are
somewhat higher or in the upper range of concentrations expected
to be encountered during routine operation will provide greater
assurance that the operating requirements will be sufficient to
achieve compliance with the performance standards. In all such
cases, very large differences between the trial POHC concentra-
tions and the expected waste concentrations should be avoided, and
the concentration of POHCs in the trial burn waste should always
be greater than or equal to the POHC concentrations expected during
routine operation.
As described in Chapter 2, this situation may be avoided if
the applicant groups the wastes according to inrinerability
and establishes a. set of operating conditions for each group
of wastes. In such a case, a trial burn would be necessary
to show the required performance for the most difficult to
destroy POHC(s) from each waste group.
4-20
-------
4.2.2 Limitations On Chemical And Physical Waste Feed Characteristics
In addition to specification of allowable waste constituents,
the permit should set appropriate limits on the chemical and physical
properties of the permitted waste(s). The parameters for which
limits should be set include, at a minimum:
Heating value
Ash content
Organically bound chloride content
Physical characteristics (e.g., physical state).
These limitations, together with the operating requirements dis-
cussed in previous sections (in particular, stipulations on waste
feed rate), limit operations to such an extent that the performance
level demonstrated during the trial burn should be achieved and
maintained during routine operation.
4.2.2.1 Heating Value
Knowledge of the waste feed heating value is necessary to main-
tain a relatively constant thermal load to the incinerator thereby
resulting in stable combustion zone conditions. Gross decreases in
heating value may indicate changes such as increased water content
or major changes in the concentration of hazardous constituents,
which would make the waste more difficult to incinerate. Addi-
tionally, the permit condition for waste heating value may be used
to convert the waste feed rate from units of mass per unit time
4-21
-------
co Btus per unit time. Stipulation of waste feed rate in this
manner will be advantageous in cases where the operator normally
controls heat content of the waste feed in order to maintain
stable combustion conditions.
The lowest heating value shown to correspond with the required
performance level, either during a trial burn or by alternative
data, should be designated in the permit as the lowest allowable
heating value. An upper limit on heating value is not necessary
because wastes with higher heating values are presumably more
easily burned.
4.2.2.2 Ash Content
Specification of the maximum allowable ash content will, to
some extent, ensure that the paniculate removal capability of the
air pollution control system is not exceeded during normal opera-
tion. Only a maximum allowable level need be specified. Because
ash content and exhaust gas particulate load do not correlate
directly, this permit condition is not intended as a direct means
of controlling particulate emissions. Rather, it is intended to
provide an indication that, with respect to ash content, the waste
feed to the incinerator remains similar to that tested during the
trial burn.
Specification of an effective permit condition for ash content
will be particularly difficult when the trial burn waste is contrived
4-22
-------
by blending wastes or chemicals. In such cases, the contrived blend
should contain a material (such as available fly ash) suitable for
simulating a particulate load that is equal to or greater than that
expected during routine operation. Several factors should be considered
when selecting an appropriate material for this purpose. They include
particle size distribution, mean particle diameter, the resistivity
of the material, the degree to which it may react with the stack gas
(and influence the ORE), and the design of the particulate collection
device. The waste feed selected for use in the trial burn should
contain ash at levels similar to or higher than those expected
during normal operation.
4.2.2.3 Organically Bound Chloride Content
The organically bound chloride content of a waste may be corre-
lated with scrubber performance. In order to avoid overloading
the scrubber and possibly exceeding the hydrogen chloride emission
standard, the maximum allowable organically bound chloride concen-
tration should be that for which compliance with the performance
standard has been demonstrated. Lower organically bound chloride
concentrations in the waste are allowable variations.
4.2.2.4 Physical Characteristics
Changes in the physical state of the waste feed can result in
changes in incinerator performance. The permit should therefore
limit the physical state of the waste to that of the trial burn
4-23
-------
waste. Precise guidance for establishing limits on physical charac-
teristics is not provided because determinations will be highly
case-specific and will require application of engineering judgement.
The following discussion provides a specific example which might
be used for comparative purposes.
An incinerator having both liquid injection and rotary kiln
capabilities may effectively treat liquid, solid and sludge wastes.
Furthermore, any of these wastes might be fed to the incinerator in
containers. The trial burn should be conducted such that the POHCs
are introduced in the physical form in which they are likely to be
received during routine operation. The permit should then restrict
the allowable physical form to that used during the trial burn.
If containerized hazardous wastes are to be burned, the permit
writer should consider the need to limit the condition or construc-
tion of the drums as they enter the combustion zone. For example,
when closed steel drums are fed to a rotary kiln incinerator,
explosion of the drums inside the kiln may result in "puffing",
or release of highly concentrated emissions from the kiln. The
permit, therefore, might specify that drums be opened or punctured
immediately prior to charging in order to minimize puffing. However,
if the trial burn demonstrates that introduction of closed drums
does not result in puffing, the requirement that drums be opened
may not be necessary.
4-24
-------
4.3 Specification Of Inspection Requirements For The Emergency
Waste Feed Cutoff System
The incinerator regulations require weekly testing of the
automatic waste feed cutoff system. Monthly testing may be allowed
in cases where the applicant has shown that weekly testing will be
highly disruptive and that monthly inspection is sufficient. This
test is intended only to verify operability of the emergency waste
feed cutoff system and should not require dismantling of equipment
or unscheduled calibration of sensors.
Complete shutdown of the incinerator is not necessary for
testing the feed cutoff valves and the associated safety system.
The valves may be checked while waste is input to the incinerator
and the potential for creating upset conditions are at a minimum.
The valve needs to be activated only once during an inspection;
a check of every input to the safety system does not have to
activate the valve. Additionally, if the valve is "fail safe"
(i.e., it fails in the closed position), only the control panel
circuits and associated alarms need weekly testing; the valve need
not be activated. Since cut off valves are designed to operate
for over one million cycles, testing should not be considered
to contribute significantly to wear. Detectors and sensors are
generally connected to the cut off valve through relays, which
are often equipped with an integrated test circuit.
The permit writer should specify the inspection requirements
on a case-by-case basis. Although safety system design is fairly
4-25
-------
standard due to insurance requirements, the following factors
should be taken into account before specifications of a schedule
for testing:
Extent of integration of the incinerator with other
on-site processes. If the incinerator is closely
integrated, testing is likely to be complex and
time consuming.
Installation of multiple burners. Incinerators with
more than one liquid waste burner will be better able
to maintain thermal input to an incinerator as the
cutoff valves to each burner are tested.
Presence of a solid waste loading system. Momentary
cut off during inspection of a conveyor belt, screw
feeder, or hydraulic ram should not upset incinerator
conditions because such feed systems are not likely
to be the only source of thermal input.
Availability of test circuits. Checks and inspections
of safety systems equipped with test circuits, test
jacks-, and signal simulators are easily performed and
may not require the presence of an instrument mechanic.
Safety system design. The more complex a safety system
is, the longer it will take to check. Also, if accessa-
bility to system components is a problem, a system check
is further complicated.
When evaluation of these factors indicates that weekly inspec-
tion may be impractical, alternatives may be considered. For
example, weekly inspection might be limited to testing the feed
cutoff valve and more comprehensive testing of the system (e.g.,
verifying operability of alarms, sensors and associated control
circuitry) could be conducted at longer intervals. Such a minimum
weekly inspection could involve triggering of the valve by a simu-
lated low firebox temperature. This test should be conducted by
4-26
-------
properly trained personnel, e.g., an instrument mechanic. Should
the test reveal that the system is not functioning properly, the
permit should require that the waste feed be cutoff immediately
and the necessary repairs made.
A second approach to inspection of the waste feed cutoff
system might involve weekly testing of the valve and rotational
testing of the control circuitry which interlocks the valve with
the various control parameter monitors. For example, during
Week 1, the valve might be activated by inducing a low temperature
condition. During Week 2, a high carbon monoxide level might be
used to activate the valve. This would be followed, in Weeks 3
and 4, by activation of the circuitry interlocked to the gas flow
velocity monitor and any other continuous monitoring devices.
This inspection method incorporates weekly testing of the cutoff
valve(s) with rotational (monthly, or bimonthly) testing of the
system components.
Daily incinerator inspection may be limited to visual examina-
tion for leakage, spills, corrosion, hot spots and malfunctions.
The inspection should reveal whether gauges, recorders, and moni-
tors are functioning and if there are any signs of tampering with
incinerator equipment. Visual inspection should also identify
needs for repair.
4-27
-------
5.0 EXAMPLES OF SPECIFICATION OF PERMIT CONDITIONS
The examples of the specification of permit conditions provided
in this chapter are intended to illustrate some of the approaches to
permitting discussed in this manual.
Example 1; The first example demonstrates the development of
permit conditions for an onsite incinerator dedicated to
burning one hazardous waste under one set of operating
conditions. This permitting situation is straightforward and
is used to illustrate the development of permit conditions from
performance results and the interpretation of engineering data.
Example 2; The second example illustrates the permitting of a
hearth incinerator burning a solid waste mixture and a liquid
waste mixture at one set of operating conditions. The purpose
of this example is to demonstrate how a permit is written to
allow the incineration of more than one hazardous waste and how
the maximum thermal input is used to limit waste feed rates.
Example 3; In the third example, two hazardous liquid waste
mixtures are co-incinerated with a solid waste mixture and the
incinerator operating conditions depend on which liquid waste
blends are being co-incinerated. The third example illustrates
the permitting of incineration of specific hazardous wastes at
specific operating conditions and the use of the waste grouping
concept.
The examples in this chapter address the specification of waste
composition and incinerator operating conditions from selected data
appearing in a Part B application and do not include the
specification of other provisions that must be included in a permit,
such as monitoring, safety, and inspection requirements. Each
example in this chapter is summarized in two tables; one table
contains the trial burn data that comprise part of the permit
application and the other table lists the permit conditions
developed from these data. The combustion zone temperature is used
5-1
-------
as a surrogate for all continuously monitored operating parameters
such as combustion gas velocity and carbon monoxide concentration in
the stack gas. It is assumed that all numerical values have been
checked and found acceptable.
5.1 Discussion of Example 1
5.1.1 Case Description
Sample permit application data are listed in Table 5-1. The
incinerator is a single chamber liquid injection unit integrated
with a production process. The waste stream to be incinerated is
fairly consistent in terms of waste quantity and composition. The
heating value ranges from 8QOO to 10,000 Btu/lb, and the applicant
used a waste sample with 8000 Btu/lb for the trial burn. Of roughly
a dozen Appendix VIII constituents that were present based on waste
analysis data submitted with the penult application, three POHCs
s
were selected for the trial burn: dioxane (heat of combustion 6.41
kcal/gm); ethylene oxide (heat of combustion 6.86 kcal/gm); and
phenol (heat of combustion 7.78 kcal/gm). The concentrations of
these POHCs in the waste were the following: dioxane 32; ethylene
oxide 52; phenol 202. The applicant indicated that concentrations
of each constituent varied not more than +252 from these values.
The waste analysis showed chloride content and ash content of 0.52
and 0.82 respectively. For the trial burns the applicant proposed
Q
two operating conditions, one targeted at 2100 F, the other at
2300°F.
5-2
-------
- TABLE 5-1
SAMPLE PERMIT APPLICATION DATA - EXAMPLE 1
Incinerator: Single Chamber Liquid Injection
Waste Characterization Data
Waste 1
Physical State Liquid
Heating Value 8,000-10,000 Btu/lb
Organically-Bound Chloride >0.5%
Content
Ash Content >0.8%
POHCs Dioxane
Ethylene oxide
Phenol
Two trial burns were conducted generating the following data:
Incinerator Operating Conditions
Test1 Test 2
Waste Feed Rate - Waste 1 600 Ib/hr 600 Ib/hr
Combustion Chamber Temperature
Primary See Figure 5-1
Secondary
Waste Feed Location Primary Primary
Trial Burn Results
ORE - Dioxane 99.97% 99.99%
Ethylene oxide 99.984% 99.992%
Phenol 99.991% 99.995%
Particulate Emissions 0.075 gr/dscf 0.068 gr/dscf
HC1 Emissions <4 Ib/hr <4 Ib/hr
5-3
-------
The applicant could have built additional flexibility into his
permit by continuing his trial burn waste to have lower heating
value, higher ash or chlorine content, or additional POHC's more
difficult to incinerate than dioxane.
5.1.2 Development of Permit Conditions
The results of the trial burn are shown in Table 5-1. The
trial burn at 2100°F achieved 99.99Z DRE only for phenol. The
trial burn at 2300°F achieved 99.992 DRE for all three POHCs. The
particulate and HC1 emissions were in compliance in both trial
burns. The resulting permit conditions are shown in Table 5-2.
(Note: Limits on air feed rate and CO in the stack gas are not
shown in this example, but they would be derived similarly from
trial burn conditions.)
The derivation of the permitting operating temperatures from
the continuously recorded combustion zone temperature is very
important in this example. Samples of the recorded temperatures
from each performance test are presented in Figure 5-1. The mean
temperature during Test 1 was 2160 F based on temperatures
measured at 15-minute intervals. Because there were three
temperature spikes which lasted over 45 minutes of this 7-hour
performance test, a mean value obtained at less frequent intervals
might be skewed. Ideally, the mean temperature should be obtained
from measurements at more frequent intervals. Although the
-------
TABLE 5-2
SAMPLE PERMIT CONDITIONS - EXAMPLE 1
The permittee is allowed to burn liquid hazardous wastes with the
following composition:
- Minimum heating value is 8,000 Btu/lb
- Maximum organically bound chloride content is 0.5%
- Maximum ash content is 0.8%
- No hazardous constituents more difficult to incinerate than
dioxane using the heat of combustion hierarchy may be
incinerated at Condition 1 defined below
- No hazardous constituents more difficult to incinerate than
phenol using the heat of combustion heirarchy may be
incinerated at Condition 2 defined below
The following incinerator operating conditions must be maintained
subject to the previous stipulations:
Condition 1; - The waste feed rate must be no more than 600 Ib/hr
- The minimum allowable combustion zone temperature
is 2150°F measured at (specify location of
temperature sensing device used during the
performance test); at lower temperatures, the
waste feed cut off system must be activated
Condition 2: - The waste feed rate must be no more than 600 Ib/hr
- The minimum allowable combustion zone temperature
is 1950°F measured at (specify location); at
lower temperatures, the waste feed cut off system
must be activated
5-5
-------
Test 1
Temperature
Time
Test 2
? -\~\.-\
Temperature
°F
Time
30 minutes
F1GUBZ 5-1
SAMPLES OF CONTINUOUSLY RECORDED TZ^PERAITOES
5-6
-------
the amount represents an increase of less than 10 percent. The
temperature spikes account for approximately 10 percent of the time
of the performance test. Considering both of these values, the
incinerator is probably operating at steady state conditions. If
the values were considerably less than 10 percent deviations, steady
state conditions would definitely exist. If the deviations were
greater than 15 percent, the incinerator would probably not be
operating at steady state.
Specification of the allowable temperature range for Test 1 is
difficult. The standard deviation of the Test 1 temperatures at 15
o
minute intervals is 121 F. The standard deviation might be used
to establish the allowable temperature range; however, the deviation
increases as the incinerator approaches non-steady state conditions,
which should not be permitted. If the incinerator operates at ideal
steady state conditions, the use of the standard deviation might be
overly restrictive. The purpose of allowing variations in operating
conditions is to allow adjustments to maintain steady state
conditions without activating the waste feed cut-off system. The
potential problems of permitting unsteady state operation and
confining operation too strictly may be avoided by allowing
variations that are a fixed percentage of the mean or median
temperature. In this example, a 10 percent variation from the mean
temperature was allowed, permitting a minimum operating temperature
of 1950 F. The permit writer should not specify the minimum
5-7
-------
operating temperature attained during a performance test as the
minimum permitted temperature. The minimum temperature in this
example was 1550°F and it is highly improbable that the same
performance would be obtained at a mean temperature of 1550 F as
at a mean temperature of 2160 F.
Steady state conditions were definitely achieved during Test 2;
the temperature chart does not continually increase or decrease and
there are no temperature spikes. The mean temperature measured at
15-minute intervals is 2350°F. The standard deviation is 45 F
and if this value was used to specify the permit condition, it would
be overly restrictive. As in the previous example, a deviation of
approximately 10 percent is allowed, giving a minimum operating
o
temperature of 2150 F. The records of other continuously
monitored parameters may be evaluated similarly.
5.2 Discussion of Example 2
5.2.1 Case Description
Sample permit application data for the second example are
presented in Table 5-3. The purpose of this example is to
illustrate the permitting of mixed wastes and spiked wastes, and
permitting on the basis of total thermal input. The incinerator in
this example is a multiple chamber hearth burning a mixture of solid
hazardous wastes and a mixture of liquid hazardous wastes.
The waste characterization data in this example are the results
from the analysis of waste mixes comprised of several different
5-8
-------
TABLE 5-3
SAMPLE PERMIT APPLICATION DATA - EXAMPLE 2
Incinerator: Multiple Chamber Hearth
Waste Characterization Data
Waste Blend 1 Waste Blend 2
Physical State Solid Liquid
Heating Value 5000 Btu/lb 80,000 Btu/gal
Organically-Bound Chloride 4-6% <0.7%
Content
Ash Content 10-25% 0.5%
POECs Phthalic anhydride Pyridine
Paraldehyde Toluene diamine
Phenol Aniline
One trial burn was conducted generating the following data:
Incinerator Operating Conditions
Test 1
Waste Feed Rate - Waste 1 200 Ib/hr
Waste 2 15 gal/hr
Combustion Chamber Temp.
Primary 1400-1600°F
Secondary 1750-1900°F
Waste Feed Location - Waste 1 Primary
Waste 2 Primary
Performance Results
DRE - all POHCs 99.99%
Particulate Emissions 0.072 gr/dscf
HC1 Emissions >4 Ib/hr
99.2% removal efficiency
5-9
-------
hazardous wastes. Analytical data are provided on the two mixed
wastes in the form each enters the incinerator. The data indicate
that all solid wastes received at the facility are blended so that
the heating value is greater than 5000 Btu/lb, the organically bound
chloride content ranges from 4 to 6 percent, and the ash content is
between 10 and 25 percent. Similarly, all non-halogenated liquid
wastes are blended to achieve the stated values.
The FOHCs present in the wastes are not considered very
difficult to incinerate if the heat of combustion heirarchy is
used. The applicant may spike these wastes with hazardous
constituents more difficult to incinerate than phthalic anhydride
and pyridene, particularly if the incinerator feeds are blended and
such constituents may be present in future shipments of wastes. If
the wastes are spiked using less incinerable compounds such as
maleic anhydride or nitroaniline, and satisfactory performance is
achieved, the permit could be written to allow the incineration of
wastes containing a greater number of hazardous constituents.
Spiking wastes reduces the number of trial burns that might be
necessary if wastes are received containing hazardous constituents
that are more difficult to incinerate than those specified in the
permit.
One trial burn was conducted with both hazardous waste mixes
being fed to the incinerator simultaneously. The range of
combustion chamber temperatures was determined using the method
5-10
-------
presented in Example 1. The trial burn performance results were in
compliance with the regulatory requirements.
5.2.2 Development of Permit Conditions
The permit conditions developed from the trial burn data are
presented in Table 5-4. Because the physical states of the waste
mixtures are different, the permit must specify the compositions of
two separate incinerator feeds. The permit conditions can be
written directly from the waste characterization data and the
incinerator operating information because the results of all the
incinerator performance tests comply with the regulatory
requirements. The permitted composition limits of waste blends are
specified in the same manner as wastes from one specific source.
The waste feed" rates and other permit conditions may be specified in
the units most conveniently monitored by the applicant.
Waste feed is restricted to the primary chamber. If the wastes
were fed to the secondary chamber, the residence time would be
decreased and satisfactory performance might not be achieved. The
permit is written so that up to 200 Ib/hr of Waste Blend 1 or
15 gal/hr of Waste Blend 2 may be fed to the primary chamber
individually, or these amounts of the wastes may be incinerated
simultaneously. Hazardous wastes containing more readily
incinerated hazardous constituents than phthalic anhydride and
pyridene may be fed in greater amounts, providing that the total
thermal input is less than 2.2 million Btu/hr and the other permit
restrictions on waste composition are satisfied.
5-11
-------
TABLE 5-4
SAMPLE PERMIT CONDITIONS - EXAMPLE 2
The permittee is allowed to incinerate the following hazardous
wastes:
Waste Blend 1: - The physical state of the hazardous waste must
be solid
- Minimum heating value is 5000 Btu/lb
- Mmr-tmum organically hound chloride content is 6Z
- Maximum ash content is 25Z
- No hazardous constituent more difficult to
incinerate than phthalic anhydride may be
present in the waste
Waste Blend 2: - The physical state of .the waste must be a liquid
- Minimum heating value is 80,000 Btu/gal
- Maximum organically bound chloride content is 0.7%
- Maximum ash content is 0.5Z
- No hazardous constituent more difficult to incin-
erate than pyridine may be present in the waste
Waste Blends 1 and 2 may be incinerated only if the following
conditions are maintained:
- The maximum feed rate of Waste Blend 1 is 200 Ib/hr to the
primary chamber at (specify location)
- The maximum feed rate of Waste Blend 2 is 15 gal/hr to the
primary chamber at (specify location)
- The maximum thermal input to the incinerator is
2.2 million Btu/hr
- The minimum combustion zone temperature in the primary chamber
is 1400°? measured at (specify location)
- The nin-tninm combustion zone temperature in the secondary
chamber is 1750°? measured at (specify location)
5-12
-------
5.3 Discussion of Example 3
5.3.1 Case Description
The third example of developing permit conditions is a more
complex variation of the second example, illustrating the
correlation of incinerator operating conditions with waste
composition in a permit. The sample application information is
summarized in Table 5-5. The incinerator is a multiple chamber
hearth unit burning solid waste and non-halogenated liquid waste
mixtures as in the second example. A mixture of halogenated liquid
wastes is also incinerated at different operating conditions and
non-halogenated waste is fed to the afterburner to" maintain high
temperatures.
Two trial burns were conducted. The first trial burn was the
same as the trial burn conducted in Example 2, where only the solid
waste and the non-halogenated waste blends were incinerated. During
the second trial burn, all three waste blends were fed to the
primary chamber of the incinerator and the non-halogenated waste
mixture was fed to the secondary chamber. Higher combustion zone
temperatures were maintained during the second trial burn than
during the first trial burn in order to ensure adequate destruction
of the chlorinated materials. The results of both trial burns were
in compliance with the regulatory performance standards.
5.3.2 Development of Permit Conditions
The permit conditions developed from the trial burn data are
summarized in Table 5-6. The permit is similar to the one developed
5-13
-------
TABLE 5-5
SAMPLE PERMIT APPLICATION DATA - EXAMPLE 3
Incinerator: Multiple Chamber Hearth Equipped with Liquid Injection
Waste Characterization Data
Waste Blend 1 Waste Blend 2 Waste Blend 3
Physical State
Heating Value
Organically-Bound
Chloride Content
Ash Content
POHCs
Solid
5000 Btu/lb
4-6Z
10-25Z
Phthalic
anhydride
Paraldehyde
Liquid . Liquid
80,000 Btu/gal 40,000 Btu/gal
<0.7Z 15-2 5%
<0.5Z
Pyridene
Toluene
diamine
Aniline
Phenol
Two trial burns were conducted generating the following data:
Incinerator Operating Conditions
<0.5%
Tetrachloroethane
Hexachlo robenz ene
Hexachlorobutadiene
Waste Feed Rate
- Waste Blend 1
Waste Blend 2
Waste Blend 3
Test 1
200 Ib/hr
15 gal/hr
0
Test 2
150 Ib/hr
15 gal/hr
10 gal/hr
Combustion Chamber Temperature
Primary
Secondary
Waste Feed Location - Waste Blend 1
Waste Blend 2
Waste Blend 3
1400-1600°F
1750-1900°F
Primary
Primary
1400-1600°F
1850-2000°F
Primary
Primary & Secondary
Primary
5-14
-------
TABLE 5-5 (Concluded)
Performance Results
Test 1 Test 2
DRE - all POHCs 99.99% 99.99%
Particulate Emissions 0.069 gr/dscf 0.076 gr/dscf
HC1 Emissions 4 Ib/hr 4 Ib/hr
>99.4% removal >99.8% removal
efficiency efficiency
5-15
-------
TABLE 5-6
SAMPLE PERMIT CONDITIONS - EXAMPLE 3
The permittee is allowed to incinerate the following hazardous
wastes:
Waste Blend 1: - The physical state of the hazardous waste must
be solid
- Minimum heating value is 5000 Btu/lb
- Maximum organically bound chloride content is 6Z
- Maximum ash content is 25Z
- No hazardous constituent more difficult to
incinerate than phthalic anhydride may be
present in the waste
Waste Blend 2: - The physical state of the waste must be a liquid
- Minimum heating value is 80,000 Btu/gal
- Maximum organically bound chloride content
is 0.7Z
- Maximum ash content is 0.5Z
- No hazardous constituent more difficult to
incinerate than pyridine, may be present in the
waste
Waste Blend 3: - The physical state of the waste must be a liquid
- Minimum heating value is 40,000 Btu/gal
- Maximum organically bound chloride content
is 25Z
- Maximum ash content is 0.5Z
- No hazardous constituent more difficult to
incinerate than tetrachlorethane may be present
in the waste
5-16
-------
TABLE 5-6 (Concluded)
Waste Blends 1 and 2 may be incinerated only if the following
conditions are maintained:
- The maximum feed rate of Waste Blend 1 is 200 Ib/hr to the
primary chamber at (specify location used during performance
test). Up to 750,000 Btu/hr of wastes containing more easily
incinerated hazardous constituents, and satisfying the other
permit conditions, may be fed at this location.
- The maximum feed rate of Waste Blend 2 is 15 gal/hr to the
primary chamber at (specify location used during performance
test). Up to 1.2 x 10^ Btu/hr of wastes containing more
easily incinerated hazardous constituents, and satisfying the
other permit conditions, may be fed at this location.
- The minimum combustion zone temperature in the primary
chamber is 1400°F measured at (specify location).
- The minimum combustion zone temperature in the secondary
chamber is 1750°F measured at (specify location).
Waste Blend 3 may be incinerated only if the following conditions
are maintained:
- The maximum feed rate of Waste Blend 1 is 150 Ib/hr to the
primary chamber at (specify location used during performance
test). Up to 750,000 Btu/hr of wastes containing more easily
incinerated hazardous constituents, and satisfying the other
permit conditions, may be fed at this location.
- The maximum feed rate of Waste Blend 2 is 15 gal/hr, no more
than 5 gal/hr of which may be fed to the secondary chamber at
(specify location used during performance test). Up to
1.2 x 10° Btu/hr of wastes containing more easily
incinerated hazardous constituents, and satisfying the other
permit conditions, may be fed at this location.
- The maximum feed rate of Waste Blend 3 is 10 gal/hr to the
primary chamber at (specify location used during performance
test). Up to 400,000 Btu/hr of wastes containing more easily
incinerated hazardous constituents, and satisfying the other
permit conditions, may be fed at this location.
- The minimum combustion zone temperature in the primary
chamber is 1400°F measured at (specify location)
- The minimum combustion zone temperature in the secondary
chamber is 1850°F measured at (specify location)
5-17
-------
in Example 2 but includes additional operating requirements for the
incineration of the halogenated waste blend.
One of the operating requirements is the restriction on waste
feed location. Wastes may only be fed to the incinerator at the
locations used during a satisfactory performance test. During
Test 2 of this example, 10 gal/hr of Waste Blend 2 were fed to the
primary chamber and 5 gal/hr were fed to the secondary chamber, or
afterburner. Therefore, the permit conditions stipulate that no
more than 5 gal/hr of Waste Blend 2 can be fed to the afterburner at
the same location used during the performance test and Waste Blend 3
cannot be fed to the afterburner. If Waste Blend 3 was fed to the
afterburner, the residence time in the incinerator would be less
than if it was fed to the primary chamber, and a 99.99 percent DRE.
might not be attained. In the absence of performance data, it must
be assumed that a 99.99 percent DRE will not be achieved and the
permit is developed accordingly. Up to 15 gal/hr of Waste Blend 2
may be fed to the primary chamber because the residence time is
increased if the waste is fed to the primary chamber instead of the
afterburner. The increase in residence time will increase the DRE,
and such operation is permitted.
Because of the restrictions on waste feed locations, the permit
cannot be written on the basis of total thermal input to the
incinerator. Maximum thermal inputs may be specified at each feed
5-18
-------
location, but unless significant amounts of auxiliary fuel were used
during the performance test, the allowable feed rates of easily
incinerated wastes will not be much greater than the feed rates used
for the performance test. Table 5-6 demonstrates how the thermal
input at each feed location may be specified in a permit.
5-19
-------
6.0 REFERENCES
1. U.S. Environmental Protection Agency. Engineering Handbook for
Hazardous Waste Incineration, SW-889 IERL, Cincinnati, Ohio,
September 1981.
2. American Society for Testing Materials. Standards for Analysis,
American Society for Testing Materials, Philadelphia, PA, 1980.
3. U.S. Environmental Protection Agency. Sampling and Analysis
Methods for Hazardous Waste Incineration, OWWM, Washington, DC,
February 1982.
4. Kiang, Yen-Hsiung. Total Hazardous Waste Disposal Through
Combustion, Industrial Heating, December 1977.
5. North American Combustion Handbook, North American Manufacturing
Company, Cleveland, OH, 2nd Edition (1978).
6-1
-------
APPENDIX A - EVALUATION OF INCINERATOR DESIGN INFORMATION
The permit writer should evaluate incinerator design
information in order to ensure that the unit is capable of attaining
the operating conditions stated in the permit application and that
the waste chaxacteristics, incinerator design specifications, and
incinerator operating conditions are in agreement. The evaluation
is particularly important for new incinerators because draft permit
conditions are established on the expectation that the operating
conditions will be sufficient to comply with the performance
standards. The methods for evaluation presented in this chapter are
engineering estimates developed from simplifying assumptions. More
precise methods of analysis are presented in the Engineering
Handbook . Typical operating conditions for hazardous waste
incinerators axe summarized in Table A-l for reference and general
guidance.
The permit application must contain a detailed engineering
description of the incinerator unit. Although an applicant may
submit engineering blueprints, they are too detailed to be used
effectively by the permit writer. Evaluations of structural
integrity are not necessary in order to approve an application.
Schematic drawings or process and instrumentation diagrams may
assist the permit writer in evaluating incinerator design.
The design characteristics evaluated in this chapter include
the combustion zone temperature, the gas volume flow rate and
A-l
-------
1
^g
sa
^3
fl3
3
H
W
Z
M
H
a
z
o
u
u
z
M
H
25
Ed
b
O
Qtf
O
H
u
z
u
z
M
^
^^
CM
3
a. u
c .c ^
M -H. C
M 9
*4 3 *
9 OQ «o
b*O Z
0 O ^
H
U
b
b **
P* 0
«§
OB *
a .s
0 u
u -*
M O
fiU LJ
CO
M
0
a
p*
H »
0 e
u o
e u
v 0
V CO
^4
0
fftt
0 b*
e o
o
N 0*
. S b
0 9
H M
U 9
9 b
J0
0.
a a
50
H
0
O.
H*
b
O
9
b
0
e
^^
y
M
0 ^
m O en
fH ^N in
i eo i o
^ <-* 1 -H
C3 ^
O O
CM CM
1 1
O O
CM «n
^^
^^
9
«^j
H
O -4
O
m o
en N"'
b
O ^
CM
0 0
§0
\O
7 i
§ §
eo CM
e
u
0 e
4-) «H
e 2
*^ x
<-! b
9 «
1 1
'
O
O
CM
O
CM
^
O
f^
o
^^
1
CM
1
§
O
CM
b
0
e
b
b
0
.u
^4
<
O
CM /».
1 %O
rn *~*
o
o o
o o
CM ^
1 1
o o
^ o
CM
o
1
CM
§§
>O CO
1 1
§i
M9 CM
^4
b
0
b A
0 a
§.§
.0
W X
b
X CO
S|
^ ^4 u
b b 0
9 Q- W
0
O s^
r- O
O «-'
O
ir>
H
i
o
tH
m
CM
1
in
p»
O
o
0
CM
1
I
r4
U
gg
"O
N
«H
^
-------
residence time at the combustion temperature, combustion chamber
mixing, air pollution control equipment, and instrumentation and
safety system design. These characteristics are capable of
significantly affecting incinerator performance.
English units of measure are used throughout this guidance
manual because of their widespread use in incineration technology
and practice in the United States. Conversion factors to metric
units are provided in Appendix B.
A.I Combustion Zone Temperature
Combustion zone temperatures may be estimated using the
relationship between the gross thermal input to the incinerator
(higher heating value), excess air usage, and adiabatic temperature
of the combustion gases shown in Figure A-l. The figure is
applicable to liquid and solid wastes. The curves are derived from
theoretical computations of the combustion gas temperatures attained
under adiabatic (no heat loss) conditions. Thus, the temperatures
are the maximum that would be encountered in actual practice. The
use of these figures is demonstrated by the following example:
The heating value of the incinerator feed is 11,750 Btu/lb and
the excess air is 30 percent. Locating these values on
Figure A-l, the corresponding adiabatic temperature is about
2900°F.
If total thermal input to the incinerator is specified on a
moisture free basis (the energy required to heat and vaporize the
free water present in the waste is not subtracted from the total
thermal input), the adiabatic combustion zone temperature (T) may be
A-3
-------
PARAMETERS: X EXCESS AIR
2000 6000 10000 14000 13000
HIGHER HEATING VALUE, BTU/LB.
FIGURE A-l
ADIABATIC TEMPERATURE OF COMBUSTION GASES
FROM WASTE INCINERATION <4'
A-4
-------
estimated using the following formula derived from a simplified
energy balance:
HV + 0.0525 (EA)(HV) - 845 W
2.3 x ICT4 (EA)(HV) + 0.612 W
Equation A-l
Where: HV = Heating value of moisture free waste (Btu/lb)
EA = Excess air usage (1 + % Excess Air/100)
W = Amount of water entering the incinerator (Ib/hr)
T - Combustion zone temperature (°F)
If the combustion zone temperature specified in a permit
application is different from the theoretical adiabatic temperature,
the excess air value should be checked using the method in A.2.1.
A.2 Combustion Gas Velocity
The combustion gas velocity measurement required by the
regulations is affected by excess air use and auxiliary fuel use,
and is indicative of residence time and turbulence. Methods of
estimating values of each of these parameters to ensure that they
correlate with the measured combustion gas velocity are presented in
the following subsections.
A.2.1 Excess Air Usage
Excess air is defined as that air supplied in addition to the
quantity required for stoichiometric (perfect) combustion and may be
expressed as:
% Excess Air = Actual air feed rate - stoich. air feed rate
Stoich. air feed rate
Equation A-2
Excess air acts as a diluent in the combustion process and reduces
the temperature in the incinerator (i.e., maximum theoretical
A-5
-------
temperatures are achieved at zero percent excess air) . This
temperature reduction is desirable to limit refractory degradation
when readily combustible, high heating value wastes are burned.
When aqueous or other low heating value wastes are burned, excess
air is usually minimized to keep the system temperature as high as
possible.
The percentage of excess air used during incineration can be
computed from stack monitoring data by EPA Method 2, Appendix A,
40 CFB. 60. The permit writer can check the computed excess air
value using the following equation:
1 ****** *** ' o.26«o& * 10°
Equation A-3
where: 02 " Percent oxygen in the stack gas by volume,
dry basis
N2 * Percent nitrogen by volume, dry basis
CO * Percent carbon monoxide by volume, dry basis
If stack monitoring data are not available, the permit writer
can check whether the thermal input, combustion gas velocity, and
excess air usage correlate using the following engineering
approximations. The combustion gas volume may be estimated from the
engineering approximation that 1 standard cubic foot (scf) of
combustion gas is generated for each 100 Btu/lb of incinerator feed
material. This estimate is true only for stoichiometric combustion
(zero excess air). This relation may be expressed as:
A-6
-------
scf of gas = Higher heating value of feed (Btu/lb)
Ib of feed TTTD
Equation A -4
If auxiliary fuel is co-fired with the waste, the heating value
(HV) of the feed may be expressed as:
HV(feed) - HV(waste) x (fraction of waste in feed) + HV(fuel)
x (fraction of fuel in feed)
Equation A-5
Because the volumes of combustion gas and air feed required for
combustion are nearly equal under standard conditions, this same
approximation is also valid to estimate the volume of air required
for combustion.
The volume of combustion gas under standard conditions,
expressed as standard cubic feet (scf), may be converted to the
volume under operating conditions expressed as actual cubic feet
(acf), by use of the ideal gas law. A standard temperature of
32 F is used in this manual, although a standard temperature of
60°F or of 70°F is used by the fan and blower industry. Because
most incinerators operate at atmospheric pressure, this law
simplifies to:
acf = Stack gas temperature (460 + °F)
scf
Equation A-6
Another useful and approximate relationship converts the volume of
combustion gas obtained with stoichiometric air to the total volume
A-7
-------
of gas generated with a known percentage of excess air. The
calculation, is as. follows:
(Stoi. gas vol.) x (1 + % excess air/100) « total gas volume
Equation A-7
This approximation is adequate for most fuels or vaste/fuel mixtures
and for excess air values to 200 percent.
If the incinerator is equipped with a quench or a wet air
pollution control device, the approximate total gas volume must
include the water vapor contributed by the equipment. The gas
streams are usually saturated with water and the water content of
the saturated gas is a function of the gas temperature, as
illustrated in Figure A-2. The saturated total gas volume may be
estimated using the following formula:
Saturated total total gas volume
gas volume * 1-concentration of water in flue gas (2/100)
Equation A-8
The total gas volume flow rate or saturated total gas volume
flow rate can be converted to the combustion gas velocity if the
cross sectional area of the gas duct at the point of the velocity
measurement is known. The volume flow rate divided by the cross
sectional area is the gas velocity. Typical stack gas velocities
range from 50 to 60 feet per second. The utility of these
approximations is presented in the following sample calculation:
An applicant states that the stack gas velocity is 3000
ft/min downstream of a wet scrubber when using 22 percent
excess air. The permit writer uses the following data to
check these values:
A-8
-------
m
§
0)
W
eg
O -8
0)
41 M
E 03
3 It
^ a
o w
> «
ca
u
c *>
0) I-
u o
h CU
OJ OJ
80
70
60
50
40
30
20
10
I I
60 80 100 120 140 160 180 200 220
Gas Temperature, °F
Basis: Volume of water vapor In saturated air at 1 atm.
FIGDBE A-2
WATER VAPOR CONTENT OF SATURATED FLUE GAS
A-9
-------
Waste feed rate: 17 Ib/min
Heating value of waste: 5000 Btu/lb
Auxiliary fuel feed rate (#6 Residual Oil): 17 Ib/min
Heating value of fuel: 18,000 Btu/lb
Note: Gross heating Values of Several Fuels
Btu/lb Btu/scf Btu/gal
Natural Gas 21,800 1020
#2 Distillate Oil 19,000 137,000
#6 Residual Oil 18,100 153,000
Stack gas temperature: 160°F
Stack diameter: 2 feet
Substituting into Equations A-4 and A-5, the calculation of
combustion gas volume flow rate for stoichiometric air is:
17 Ib/min. (5000 Btu/lb) + 17 Ib/min (18100 Btu/lb) - 3930 scf/min
100 Btu/scf
Substituting into Equation A-7, the calculation of combustion
volume gas flow rate including excess air is:
(3930 srcf/min)(l + 22/100) - 4790 scf/min
Calculation of combustion gas volume flow rate at 160°F using
Equation A-6 is:
4790 scf/min (460 + 160)°R - 6040 scf/min
492 RO
Using Equation A-8 and Figure A-2, the calculation of saturated
flue gas volume flow rate at 160°F is:
6040 acf/min - 8880 acf/min
(1 - 32/100)
Calculation of saturated combustion gas velocity:
8880 acf/min
Tr(2ft)2/4
- 2830 ft/min - 47 ft/sec
The estimated gas velocity agrees within six percent of the
velocity stated in the permit application. If the difference
were greater than ten percent, the application could be
referred to the Permit Assistance Team for a more detailed
evaluation.
A-10
-------
A.2.2 Auxiliary Fuel Use
The correlation of the combustion zone temperature, total
thermal input, and excess air use may be checked using an elementary
heat balance. The sum of the heat lost to combustion gas and the
associated water vapor and the heat lost to radiation should equal
the heat input from the waste and auxiliary fuel. Combustion gas
enthalpy (or heat content) and water vapor enthalpy are a function
of combustion zone temperature as illustrated in Figures A-3
and A-4. Radiation losses may be estimated at five percent of the
total heat input as a rule of thumb. If the heat loss is greater
than the heat input from the waste, auxiliary fuel must be added to
make up the difference. If the heat input is greater than the heat
loss, the excess air usage is generally increased to maintain the
desired combustion zone temperature. The utility of these
approximations is presented in the following example:
The permit writer may wish to estimate the auxiliary fuel use
and compare the value with actual fuel consumption for an
incinerator operating under the following conditions:
Waste feed rate: 5000 Ib/hr
Heat content of waste: 6000 Btu/lb
Water content of waste: 20%
Combustion zone temperature: 2200°F
Excess air usage: 150% (2.5 times stoichiometric)
Heat Input = (6000 Btu/lb)(5000 Ib/hr)
= 30 x 106 Btu/hr
In order to calculate the heat output the flue gas volume must
be estimated and multiplied by the enthalpy obtained from
Figure A-3 (44 Btu/scf).
A-H
-------
Enthalpy
Btu/scf
80
70
60
50
40
30
20
10
3000 2000 1000
Combustion Zone Temperature, *?
FIGTJBE A-3
FLDZ GAS ENTHALPY AS A FUNCTION
OF COMBUSTION ZONE TEMPE3ATUBZ
A-12
-------
C3
U
TS
-------
Calculation of flue gas enthalpy:
30 x 106 Btu/hr (2.5)(44 Btu/scf) = 33.0 x 106 Btu/hr
100 Btu/scf
Calculation of water vapor enthalpy using the enthalpy at
2200°F obtained from Figure A-4 (2200 Btu/lb):
(20 Ib water/lb waste)(500 Ib waste/hr)(2200 Btu/lb) - 0.2 x 106 Btu/lb
Heat Output » 33.0 x 106 Btu/hr flue gas enthalpy
+0.2 x 10^ Btu/hr water vapor enthalpy
+1.5 x 106 Btu/hr radiation loss
(0.05 x 30 x 106 Btu/hr)
- 34.7 x 106 Btu/hr
The heat output is approximately 4.7 x 10^ Btu/hr greater
than the heat input, so auxiliary fuel must be used to maintain
the combustion conditions.
The entire heat content of auxiliary fuel is not available to
compensate for thermal input deficiencies because of associated flue
gas losses. As the combustion zone temperature is increased, the
available heat from fuels decreases. The fraction of heat avail-
-4
able, F, may be estimated using the formula F » 1 - (2.6 x 10 T),
where T is the combustion zone temperature in Fahrenheit degrees.
This formula is derived from the available heat values.of several
fuels presented in the North American Combustion Handbook .
Continuing the previous examples using #2 fuel oil as the auxiliary
fuel, F - 1 - (2.6 x 10~4T)
F - 1 - [2.6 x 10"4 (2200°*)]
- 0.43
Equation A-9
4.72 * 106 Btu/hr - 580 gal/hr
(0.43)(19,000 Btu/gal)
A-14
-------
Therefore, the auxiliary fuel consumption in the example would be
approximately 580 gallons per hour of #2 fuel oil.
A.2.3 Residence Time
The gas residence time in the combustion ^one may be estimated
if the volume of the combustion gas is known. The residence time
can be approximated by dividing the volume of the combustion chamber
by the combustion gas volume flow rate under actual conditions. A
sample calculation is provided below.
The combustion zone is cylindrical with a diameter of 5 feet
and a length of 26 feet.
Volume of combustion zone = u^_^
4
Equation A-10
" 3.14 (52)(26)
4
- 5iO ft3
The combustion gas flow rate is 4800 scf/min.
This volume flow rate must be corrected to combustion zone
conditions using the ideal gas law, Vj/Tj_ » ^2^2- If
the combustion zone is 2200°F:
acf flue gas m 4800 scf
(460 + 2200)°R (460 + 32)°R
Volume flow rate of flue gas - 25,900 acf/min.
Residence Time - (510 ft3)(60 sec/min)
25,900 acf/min
- 1.18 sec
In rotary kiln/afterburner incinerators, residence time of the
solids in the kiln is dependent on the physical state of the waste.
A-15
-------
Finely divided solids may incinerate within a fraction of a second;
dense, bulky materials may require up to an hour. Waste liquids
with high heating value may be co-incinerated with solids, slurries,
or tarry materials. Residence times for liquids are generally much
shorter than for the other materials. Generally, gas and solid
residence times in rotary kilns are not included in residence time
computations because lover temperatures are maintained in the kiln
than in the afterburner.
The overall residence time (t) for movement of solids through a
kiln may be estimated by:
t * 0.19L
(rpm) DS
Equation A-ll
where: t * the mean residence time
L » the length of the kiln
rpm * the kiln rotational velocity
D * the kiln inside diameter
S » the kiln slope
In kiln operation, solids or sludges are fed to the higher end of
the kiln and then pass down through the kiln where they are
progressively heated and ignited. Just prior to discharge near the
lower end, the ash may enter a cooling zone. As gases rise from the
ignited solids, they may be further oxidized, but conversion to the
ultimate oxidation products will usually occur in the afterburner.
The permit writer should not attempt to specify residence time
requirements in a permit because of the difficulties encountered
when trying to measure or estimate values. The permit writer may
check the residence time stated by the applicant if such information
is included.
A-16
-------
A.2.4 Combustion Zone Turbulence
The permit writer may use combustion gas velocity neasurements
to evaluate turbulence in the combustion chamber. Temperature,
oxygen, and residence time requirements for waste destruction all
depend to some extent on the degree of mixing achieved in the
combustion chamber. However, this parameter is not measureable and
the permit writer must rely on sufficient combustion gas velocity to
ensure turbulence. Many of the problems involved in interpreting
incineration data relate to the difficulty involved in quantifying
the degree of mixing achieved in incinerators of different design,
which is one reason for recommending trial burns.
In liquid waste incinerators, the degree of mixing is
determined by the specific burner design (i.e., how the primary air
and waste fuels are mixed), combustion product gas and secondary air
flow patterns in the combustion chamber, and turbulence.
In conventional liquid injection incinerators or afterburners,
adequate turbulence is usually achieved at superficial gas
velocities of 10 to 15 ft/sec. Superficial gas velocities (v) may
be estimated using the following formula:
v - 3.
A
Equation A-12
where: q gas flow rate at operating temperature, acf/sec
A « cross-sectional area of the incinerator chamber,
ft2
A-17
-------
When primary combustion air is introduced tangentially to the
burner (e.g., vortex burners), or secondary air is introduced
tangentially, or burner alignment is such that cyclonic flow
prevails in the incinerator, actual gas velocities exceed the
superficial velocity. Thus, adequate turbulence may be achieved at
superficial velocities less than 10 ft/sec in cyclonic flow
systems. Turbulence is increased by installing baffles in the
secondary combustion zone of the incinerator, which abruptly change
the direction of gas flow. However, baffles also increase pressure
drop across the system and are not a common practice in liquid
injection incinerator design. Steam jets can also be used to
promote turbulence. '
Turbulence may also be characterized by the Reynolds Number
(Re) achieved in the combustion zone. The Reynolds Number is
defined as:
Re -5ZP
H
Equation A-13
where: D » diameter of circular cross section or equivalent
diameter of other cross sections (ft)
7 * average linear velocity of gas through a
combustion chamber (ft/sec)
p - density of gas (lb/ft3)
HL - viscosity of gas (Ib/ft-sec)
The density and viscosity of the gases in the combustion zone
may be approximated by those of nitrogen at the combustion zone
A-13
-------
temperature (T in F). The density of nitrogen is a linear
function of temperature, specifically:
P- 38.4
460 + T
Equation A-14
The viscosity of nitrogen is temperature dependent, although
non-linearly, and may be estimated from Figure A-5. For a
combustion chamber with a circular cross section, Equation A-13
becomes:
Re =» 72,000 Q
fiD (460 + T)
Equation A-15
where: Q * volume flow rate at T (acf/sec)
|JL « viscosity of gas at T (from Figure A-5)
D = diameter of combustion chamber (ft)
T » temperature of combustion zone gas (°F)
Reynolds Numbers greater than 3000 indicate turbulent flow
conditions: the higher the number, the greater the turbulence. If
the permit writer obtains Reynolds Numbers less than 3000, adequate
mixing in the combustion zone cannot be ensured and incinerator
performance may be unacceptable unless methods to promote turbulence
are included in the combustion chamber design.
A sample calculation of the Reynolds Number is presented below:
Re , 72.700 Q
(j.D(460 + T)
V - 432 acf/sec <§ 2200°F
M. » 0.057 cp (from Figure A-5)
T = 2200°F
D - 5 ft
Re (72,700) (432)
(0.057) (5) (460 + 2200)
Re - 41,400
A-19
-------
0.064
0.062
a. 0.060
o
0.058
0.056
o
£ 0.054
tn
o
.3 0.052
0.050
0.043
1600 1800 2000 2200
Temperature *7
2400
2600
FIGURE A-5
VISCOSITY OF NITROGEN AT ELEVATED TEMPERATURES
A-20
-------
Turbulent flow is ensured because the Reynolds Number is well
over 3000.
A.3 Air Pollution Control Equipment
Air .pollutants from hazardous waste incinerators may be
classified in two groups, particulate matter and gaseous emissions,
and the air pollution control (APC) equipment is similarly
classified. However, several items of AFC equipment are capable of
removing both types of pollutants. Particulate matter is defined as
any material that exists as a solid or liquid at ambient temperature
and pressure, for example, smoke, dust, fumes, mists, and sprays.
APC devices are either wet or dry, and each type has-its
relative advantages and limitations. Dry devices have the advantage
of direct dust collection without sludge generation or the need for
subsequent wastewater treatment, but these devices cannot remove
gaseous pollutants (although injection of gas-sorbent materials in
baghouses has been suggested). Caution must be exercised during
disposal of dry dust because of explosion hazards; such dust is
often wetted to prevent secondary emission problems.
The efficiencies of APC devices are affected by factors such as:
Particulate and/or gaseous concentrations in the combustion
chamber exit stream
Particle size distribution
* Adequacy of gas prime movers
Table A-2 is a list of the six commonly used types of APC
devices used to control emissions from hazardous waste
A-21
-------
ALLED
as
vi o
Cd E-*
U 3
M as
> Cd
w z
Q M
a
« I5
! H Cd
< Z H
O C/3
Cd O i
^ za
< O W
H MS
-! es
O M
a* <
.. M^
< O
Cfa
o
M
ex.
« a
2<5S
-S^
32
S -
73.3
S «»3 ^*
"S3 a a
s^ii
-r?4
W * (J
11L
a-*
«<
u M i
-
«il
aw
-
J
X
Jl
u -*
* a
1
o
w
iv « * ^w
23 41 S
S
a o A X
a «-»
* « ^<« b
"""Si it
aw v
^>i ««
!«
to
a b »* a
a**.-a
--3 !
is.-
w «« b
s . .s
?"S
. «
^ o
« * « w
-i a i «
o - « K >
A u a>
« M a
s a u
«*w9 a
^ c« *o«
S >»«« a
« a a u c«
a.<« w 2-4
« 3
1 »-
a a
i
W w 3
b 0--« 3
« 3 «« a a
3 O.
U
s
-!- *l
« 5 b w J? 2
wo a a 5
w b w a a.
w w &
u a »
> a a
w *» a «< «4
a 3 -M a a .* M
. * OFW a « u «
a «
3 u S ^J 2
g. ^^5 ?
M « « ^: b
O
o
a
« 3
« I »*
Is
js
fl
\\
i
4 \
m
a
J
II
b
b U
w MI
wo.
a
o »
-------
incinerators. This table also lists operating pressures and
relative particulate and gaseous collection efficiencies. All six
types of APC devices remove particulate matter to some level of
efficiency. However, only three devices control gaseous pollutants
to any degree. The packed, spray, or plate scrubber is the most
efficient device for removal of pollutant gases. Mechanical ash
collectors or cyclones are sometimes used for primary dust
collection with solid waste fired combustion units. Secondary dust
collection equipment could be an electrostatic precipitator, venturi
scrubber, or baghouse.
The ash content of wastes burned in liquid injection
incinerators may be used to estimate the maximum concentration of
particulate emissions. The maximum particulate emissions are
estimated from values of the waste feed rate, the stack gas volume
flow rate, oxygen content of the stack gas and the waste ash
content. An example of this calculation is provided below:
Waste feed rate: 1000 Ibs per hour, no auxiliary fuel is used.
Stack gas volume flow rate: 120,000 scf per hour @ 7 percent
oxygen (this value may be verified or corrected to dry
conditions, if necessary, by the method presented in
Section 3.2).
Ash content of waste: 0.5 percent
The effective ash feed rate may be calculated:
(1000 Ib of waste/hr) (5 x 10~3 Ib ash/lb feed) =«
5.0 Ib of ash/hr
The maximum particulate emissions from the liquid injection
incinerator may be estimated at a stack gas oxygen
concentration of 7 percent:
A-23
-------
(5.0 Ib of a3h/hr)(7000 gralns/lb) . 0.29 gr of ash
(120,000 scf/hr) dscf
Because the particulate emission in this example is greater than the
allowable limit of 0.08 gr/dscf, this liquid injection incinerator
unit will probably be equipped with a. particulate removal device.
Maximum uncontrolled hydrogen chloride emissions may be
estimated in a similar manner. Hydrogen chloride emissions greater
than 1.8 kilograms per hour (4 pounds per hour) must be removed from
the combustion gas at an efficiency greater than 99 percent or be
reduced to less than 1.3 kilograms per hour, whichever Is greater.
The following example illustrates estimation of maximum hydrogen
chloride emissions.
Waste feed rate: 1000 Ibs/hr
Organically bound chloride content: 12%
Estimation of uncontrolled hydrogen chloride emissions:
0.12 Ib Cl 1000 Ib waste 36.5 Ib HO. ,
Ib waste * to * 35.5 Ib Cl 123 lb HC1/hr
Because uncontrolled Hd emissions are greater than 4 Ib/hr, a
scrubber will probably be installed. Allowable controlled emissions
at 99 percent removal efficiency may be estimated;
123 lb HdL/hr x (0.01) - 1.23 lb HCl/hr
Because the Hd emissions controlled to 99 percent removal are less
than 4 Ib/hr, the scrubber may operate at less than 99 percent
efficiency (as long as Hd emissions remain lower than 4 Ib/hr).
A-24
-------
A.4 Monitoring Instrumentation and Waste Feed Cut Off System
The minimum required process monitoring includes the combustion
zone temperature, waste and fuel feed rates, combustion gas
velocity, and carbon monoxide concentration of the stack gas. It is
recommended that thermocouples be used in conjection with automated
recorders to continuously record temperatures. Maximum operating
temperaures of some of the more common thermocouples are presented
below:
Copper/constantan 700°F (371°C)
Chromel/constantan 1800°F (982°C)
Iron/constantan 2000°F (1093°C)
Chromel/alumel 2200°F (1204°C)
W/W2& and W5/W26 3000°F (1649°C)
Platinum (Pt/Pt, Pt 6/Pt 30) 3000°F (1649°C)
Optical pyrometers are not acceptable combustion zone temperature
monitoring devices because of potential interferences present in the
combustion area. The pyrometers could respond to sources of light
in the combustion chamber other than the flame and give erroneous
readings.
The combustion zone operating temperature may be monitored at
more than one location in the chamber in order to minimize the
effects of local disturbances on temperature measurements.
Temperatures in the combustion chamber are not uniform; the hottest
temperatures are in the vicinity of the flame and the coolest
temperatures are at the refractory wall and air inlets. Ideally, a
shielded thermocouple should be used to measure the gas temperature
at the combustion chamber exit. Specification of the location of
A-25
-------
temperature measurement is as important as the specification of
allowable temperature ranges in a permit.
Liquid waste and fuel feed rates may be measured using
conventional instruments such as flow tubes, magnetic or acoustic
meters, paddle wheel meters, and orifice meters. These instruments
are installed downstream of liquid pumps and regulators and upstream
of the burners. Gaseous fuel flow rates are measured by orifice or
venturi devices. Solid waste loading systems may include scales to
weigh wastes as they are charged to the incinerator, or the loading
rate may be measured from the charging rate and capacity of waste
containers, such as carts, ram loaders, or 55 gallon drums. Solid
waste feed rates to manually loaded incinerators may be determined
in the same manner as with automated loading systems.
Combustion gas velocities may be measured using orifice plates
or Venturis, pitot tubes, or by indirect means. Orifice plates and
Venturis are impractical for combustion gas velocity measurements
because of the large pressure drops caused by these devices. Fitot
tubes may be used to measure combustion gas velocity in the hot zone
of an incinerator immediately downstream of the combustion chamber
or in cooler areas, such as the stack. Fltot tube measurements can
be converted to combustion gas velocity and volumetric flow rate
using the procedure in EPA Method 2 presented in the Appendix of
40 C?R 60. Changes in the molecular weight and the water content of
the combustion gas will affect the correlation of pitot tube
measurements and combustion gas velocity.
A-26
-------
Indirect measurements of combustion gas velocity may include
blower rotational speed and current use. Many blowers operate in
the region of the blower curve where static pressure and current use
(horsepower) do not change radically with a change in capacity.
Therefore, blower static pressure and current measurements are often
not suitable indicators of combustion gas velocity unless the
applicant can demonstrate a noticeable correlation. Blower rpm is
indicative of combustion gas velocity and volumetric flow rate only
if static pressure in the blower remains constant. Measurement of
combustion gas velocities using blower characteristics on
incinerators equipped with more than one blower may become very
complex, particularly if ambient air is being fed to the combustion
chamber while hot combustion gas is drawn from the chamber.
Correlation of the volumetric flow rate and blower characteristics
depends on the densities of the gases. Density measurements of the
two gases may be avoided by use of a pitot tube installed downstream
of the combustion chamber.
Measurement of pressure differentials across incinerator
components, such as combustion chambers and air pollution control
devices, is not a suitable indicator of combustion gas velocities.
Pressure differentials may be affected by leakage, changes in liquid
flow rates, and clogging phenomena as well as gas flow rates. It is
not possible to distinguish the factors affecting changes in
pressure measurements using conventional equipment such as velocity
A-27
-------
head meters. Therefore, pressure differential measurements should
not be used as gas velocity indicators; however, they are useful
monitors for upset conditions. Rapid changes in pressure
differentials may indicate stoppage of water flows to air pollution
control devices, failure of blowers, or incorrect positioning of a
damper.
Continuous monitoring of the oxygen concentration in the stack
gas is an acceptable substitute for combustion gas velocity
measurement. The oxygen concentration is indicative of excess air
usage and, if waste feed composition and feed rate remain constant,
it is-an indirect measurement of the combustion gas volumetric flow
rate. The most common method of continuous oxygen measurement is an
electrocatalytic device using zirconium oxide to promote an
electrolytic reaction, and paramagnetic and polarographic
instruments are also used. The monitors are relatively durable and
accurate instruments. Additional information about instrument
capabilities is presented in the Engineering Handbook^ .
Continuous carbon monoxide monitors are typically infrared
devices, although ultra-violet or polarographic devices may be
used. The devices may be in-situ or extractive. Additional
information about carbon monoxide monitoring instruments is
presented in the Engineering Handbook^ . Carbon monoxide
monitoring by Orsat analysis is not acceptable because it is not
continuous and it is not sensitive enough to detect ppm
concentrations in the stack gas.
A-28
-------
An applicant may monitor parameters in addition to those
required by the regulations. Supplementary process monitoring may
include such parameters as pressure differentials, current use of
blower motors and additional stack gas monitoring. Pressure drops
across major incinerator components are frequently monitored to
detect changes in the gas or liquid flow rates, and clogging in the
system. Monitoring the pressure differential provides a continuous
check on the normal operation of many air pollution control
devices. A change in the pressure drop or gage pressure is an
indication that other measured parameters in the system need to be
observed immediately to find the cause of any malfunction in order
to take corrective action.
Many kinds of pressure measurement devices are commercially
available; however, a differential pressure gage calibrated in
inches of water is usually used. In selecting a pressure measuring
device, the following items are considered:
Pressure range
Temperature sensitivity
Corrosivity of the fluid
Durability and ease of maintenance
A guide to pressure sensing device selection is summarized in the
Engineering Handbook .
Another parameter that may be monitored is the current use of
blower motors. Rapid fluctuations in the current use indicate upset
A-29
-------
operating conditions of the incinerator unit. Pressure drop and
current monitoring instruments may be integrated with the waste feed
cut off system.
Stack gases may be continuously monitored for a variety of
parameters including sulfur dioxide, nitrogen oxides, nitrogen
dioxide, unburned hydrocarbons, carbon dioxide, and oxygen.
Capabilities of instruments available for monitoring of these
parameters are discussed in the Engineering Handbook^ '.
The objective of a waste feed cut-off system is to stop waste
feed when incinerator operating conditions are not in compliance
with permit conditions. If an incinerator is not equipped with a
cut-off system, hazardous waste could be emitted to the environment
and the combustion chamber could become filled with an explosive
mixture. Every hazardous waste incinerator must be equipped with a
waste feed shut-off system under 40 CFS 264.345(e).
A pilot flame does not offer sufficient protection and may not
be considered a substitute for a waste cut-off system because it may
be extinguished or may be unable to relight the main flame.
Automatic waste feed shut-off valves are necessary and may close
upon signals from:
Combustion or atomizing air blower
Elements of input control systems, such as fuel feed rate
indicators and scrubber water flow rate indicators
The flame detector
A-30
-------
Safety devices such as pressure relief valves and emergency
venting systems
Failure of electrical power to the facility
Failure of maintenance of permitted operating conditions
(e.g., temperature, gas velocity)
Often, two shut-off valves are placed in series as a precaution
against the leak, or failure of only one valve. Shut-off valves are
often connected to flame detectors, several types of which are
available. Only ultraviolet flame detectors are suitable for use in
hazardous waste incinerators. Unacceptable types include:
Thermopiles and bimetal warping devices which are used in
low input heating applications
Photocells (cadmium sulfide and lead sulfide) which respond
to light sources in addition to the flame
Flame electrodes which are suitable only for clean natural
gas flames
Several other monitoring devices may be integrated with the
waste feed cut off system. The system should be evaluated on a case
by case basis to ensure that any malfunction that might cause
non-compliance with the performance standards activates the waste
cut-off valve.
A-31
-------
APPENDIX 3
METRIC EQUIVALENTS OF BRITISH ENGINEERING UNITS
Quantity
Length
Area
Volume
British Engineering
1 ft.
1 in.
1 ft2
1 in2
1 ft3
1 in3
Metric
3.0480 x 10"1 m
2.5400 x 10~2 m
9.2903 x 10" 2 m2
6.4516 x 10~4 m2
2.8317 x lO-2 m3
1.6387 x 10-5 m3
Mass
Density
Pressure
Heat Content
Energy, Work
Velocity
Viscosity
Flow
1 grain/scf
1 lbf/in2
1 in. of water
1 in. of mercury
(32°?)
1 Btu
(Internt'l Table)
1 Btu
(Internt'l Table)
1 ft /sec
1 centipoise
1 ft2/sec
1 ft3 /sec
1 U.S. gal/min
4.5359 x 10'1 kg
1.6018 x 101 kg/m3
2.2884 gram/scsi
6.8948 x 103 pascal (Pa)
2.4884 x 102 Pa
3.3864 x 103 Pa
2,3244 Joules/gram
1.0551 x 103 joule (J)
2.9307 x 10"4 kWh
3,0480 x 10"1 m/sec
1.0000 x 10"3 Pa sec
9.2903 x ID"2 m2/sec
2.8317 x 10-2 m3/sec
6.3090 x 10~5 m3/sec
B-l
-------
APPEHDIX B (Couciudad)
Quantity
British Engineering
Metric
Heat
Conductivity
Temperature
1 BtuClntnt'l Table) in
" sec - ft 2 - "F
degree Fahrenheit (tp)
degree Fahrenheit (t?)
degree Rankine (t-g.)
5.192 2 x 102 W/m-ak
- (ty -f- 459. 67) /1. 8
tcalsius- (t? - 32) /I. 8
t^/1.8
B-2
-------
-------