US3724173A

US3724173A - Pollution control process

Info

Publication number: US3724173A
Application number: US00127500A
Authority: US
Inventors: L Fry
Original assignee: FRY L ROOFING CO
Current assignee: FRY L ROOFING CO; FRY L ROOFING CO US; Owens Corning
Priority date: 1971-03-24
Filing date: 1971-03-24
Publication date: 1973-04-03
Anticipated expiration: 1990-04-03

Abstract

Process for substantially reducing the particulate emission, opacity and odor of an asphalt saturator effluent to form a substantially odor-free gas stream using an exhaust stack stream that has previously been substantially purified for recycle to the process.

Description

United States Patent 1191 Fry, Sr.

1541 POLLUTION CONTROL PROCESS [75] Inventor: Lloyd A. Fry, Sr., Hinsdale, I11.

[73] Assignee: Lloyd A. Fry Roofing Company,

Summit (Argo P. 0.), I11.

[22] Filed: Mar. 24, 1971 [21] App1.NO.: 127,500

521 U.S.Cl. ..55/s9,55/94,55/95, 55/228, 55/233, 55/250, 55/260, 261/17,

51 1111.01. ..B0ld47/06 5s FieldofSearch ..55/s4,71,73,s5,s9,90,

[56] References Cited UNITED STATES PATENTS 1,182,543 5/1916 Ferguson ..55/95 1 51 Apr. 3, 1973 2,668,754 2/1954 Lichtenfels ..55/85 3,520,113 7/1970 Stokes ....55/233 3,522,000 7/1970 Kinney ..55/73 3,662,695 5/1972 Johnson ..l10/18 R FOREIGN PATENTS OR APPLICATIONS 221,637 12/1957 Australia ..55/220 630,625 11/1961 Canada ..208/4 645,383 7/1962 Canada ..208/39 1,034,147 7/1958 Germany ..55/89 Primary Examiner-Bernard Nozick Att0rney--Nathan N. Kraus and Joseph R. Marcus [57] ABSTRACT Process for substantially reducing the particulate emission, opacity and Odor of an asphalt saturator effluent to form a substantially odor-free gas stream using an exhaust stack stream that has previously been substantially purified for recycle to the process.

8 Claims, 3 Drawing Figures PATENTEDAPR 3 191a SHEET 1 or 5 INVENTOE llozzj.fiy, Sr 12M POLLUTION CONTROL PROCESS BACKGROUND OF INVENTION environmental quality, and especially with the very air we breathe and the water we drink, this invention aids in the elimination of various pollutants from our environment from a potential source of pollution, namely, the asphalt saturator effluents from felt saturators at an industrial roofing preparation complex.

It is well known in the prior art how to remove pollutants in general. However, it has been found that most methods are ineffective and/or prohibitively expensive. This invention discloses a pollution control process that has met the standards of the State of Minnesota utilizing a process which is highly effective and, compared to prior art methods, relatively inexpensive. While it is true that there are no national standards as such, the Minnesota Air Pollution Control Agency Rules are fairly representative of the standards imposed by Minnesotas sister states.

The present invention thus is an improved process and method for performing the steps of reducing particulate emission, opacity and odor from a pollutantbear ing waste gas stream.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a process for substantially reducing the particulate emission, opacity and odor of an asphalt saturator effluent.

It is another object of this invention to provide a process that will allow an exhaust gas stream to be exhausted to the atmosphere without substantially endangering our environmental quality.

It is a specific object of this invention to provide a at separation conditions to produce a hydrocarbonaceous particle-suspended particulate-free gaseous stream; (c) withdrawing from said first separation zone said hydrocarbonaceous particle-suspended particulate-free gaseous stream and introducing said stream into a second separation zone maintained at separation conditions so as to produce a substantially odor-free gaseous stream; ((1) removing from said second separation zone said substantially odor-free gaseous stream and introducing said stream into exhaust stack means; (e) recycling from said exhaust stack means at least a portion of said substantially odor-free gaseous stream to a second contacting zone wherein said stream is contacted with contacting fluid at contacting conditions and then passed to said first contacting zone for admixture with said effluent of Step (a); and (f) removing via said exhaust stack means the remaining portion of said substantially odor-free gaseous stream from said process.

The invention can be most clearly described and illustrated with reference to the attached drawings which are schematic representations of specific embodiments of my invention.

DESCRIPTION OF THE DRAWINGS Referring now to FIG. 1, asphalt saturator 101 represents the portion of the roofing preparation process utilizing felt saturators wherein an asphalt saturator effluent containing particulates, and having a high opacity and an objectionable odor are generated. The effluent from asphalt saturator 101 passes via line 102 into a first contacting zone 103, labeled contacting zone I wherein the effluent is contacted, at contacting conditions, with a contacting fluid passing into contacting zone Ivia line 104.

A fluid stream comprising hydrocarbonaceous particles and finely divided suspended particulates is withdrawn from contacting zone I via line 105 and introduced into a first separation zone, labeled separation zone I wherein the hydrocarbonaceous particles and suspended particulates are separated from the fluid stream at separation conditions so as to produce a hydrocarbonaceous particle-suspended particulate stream exiting from the process via line 106 for further treatment, not shown, and a hydrocarbonaceous partiole-suspended particulate-free gaseous stream which is pollution control process for substantially reducing the particulate emission, opacity and odor of an asphalt saturator effluent utilizing a particulate-free odor-free gas stream from exhaust stack means for recycle to the process to further insure an effective clean-up of undesirable materials in an asphalt saturator effluent from a normal processing operation.

Therefore, the present'invention provides a pollution control process for substantially reducing the particu-' late emission, opacity and odor of an asphalt saturator effluenLwhich comprisesthe steps of: (a) passing said effluent into a first contacting zone wherein said effluent is contacted with a contacting fluid at contacting conditions; (b) withdrawing from said first contacting zone a fluid stream comprising hydrocarbonaceous particles and finely divided suspended particulates and introducing said stream into a first separation zone wherein saidhydrocarbonaceous particles and said suspended particulates are separated from said stream withdrawn from separation zone I viz line 107 and passed to separation zone II. Separation zone II is maintained at separation conditions so as to produce a substantially odor-free gaseous stream. The substantially odor-free gaseous stream is removed from second separation zone II via line 109 and introduced into exhaust stack means 110 which may be an exhaust stack. At least a portion of the substantially odor-free gaseous stream is now recycled via-line 1 l l to a second contacting zone 112, labeled contacting zone II. The substantially odor-free gaseous stream is again contacted with contacting fluid via

lines

104 and 113 at contacting conditions and the stream is then passed via line 114 to contacting zone 103, labeled contacting zone I for admixture with the untreated asphalt saturator effluent from asphalt saturator 101. The remaining portion of the substantially odor-free, low opacity and'unobjectionable gaseous stream is removed from the exhaust stack 1 10 via line 115 for passage to the atmosphere.

In a preferred embodiment, both contacting zones I and II may comprise duct means containing a plurality of nozzle spray means and the contacting conditions would include contacting the effluent from the asphalt saturator and the odor-free gaseous stream, respectively, with a contacting fluid comprising water. The spray means cause the water exiting from the spray means to exit at superatmospheric pressure so as to produce a curtain of contacting fluid reaching the cross-sectional area of the duct means. In a particularly preferred embodiment, the contacting fluid is maintained at a pH of from about 8.0 to about 9.0.

With reference now to FIG. 2, which a still more particularly preferred embodiment of my invention, fumes are generated from 480 F asphalt used to saturate felt for making composition asphalt roofing in a completely enclosed saturator and saturated felt looper l. The asphalt saturator effluent contains hydrocarbonaceous particles, finely divided particulates, has a high opacity and an objectionable odor. The asphalt saturator effluent, in this preferred embodiment, is simultaneously passed via lines 2 by means of fans 3 and passed into a plurality of first contacting zones 4 wherein the effluent is contacted with contacting fluid entering first contacting zones 4 via lines 5 and

lines

5a, 5b, 5c, and 54, as hereinafter described.

In a preferred embodiment, contacting zones 4 are duct means containing a plurality of nozzle spray means 5a, 5b, 5c and 5d. The contacting fluid comprises treated water which is filtered and recycled'as hereinafter described and the contacting fluid exits from the nozzle spray means at super atmospheric pressure of about 70 psi so as to produce a curtain of contacting fluid reaching the cross sectional area of the duct means which are approximately 4 feet in diameter. Now, more specifically, the nozzle spray means are arranged so as to provide a 4.5 gallon per minute spray which creates a curtain reaching the cross sectional area of the ducts to condense the hydrocarbonaceous particles and other suspended particulates which then pass from contacting zones 4 through filters 6, if desired, through lines 7 into first separation zones 8 wherein the hydrocarbonaceous particles and suspended particulates are separated from the gaseous streams at separation conditions to produce hydrocarbonaceous particle suspended particulate free gaseous streams.

Typically, first separation zones 8 are vessels having a diameter of approximately 12 feet and are approximately 12 feet high. Both separation zones 8 have a baffle plate 9 that is approximately 8 feet long and screening 10 wherein the hydrocarbonaceous particles and suspended particulates are separated from the gaseous streams and removed from the process as hereinafter described.

A hydrocarbonaceous particle-suspended particulate-free gaseous stream is then withdrawn via lines 11 from first separation zones 8 and then introduced into second separation zones 12 which are maintained at separation conditions so as to produce substantially odor-free gaseous streams. Typically, second separation zones 12 are approximately 12 feet in diameter and 12 feet tall and contain an expanded metal screening support 13 which holds a paclced bed filter 14. As hereinafter described, the hydrocarbonaceous particlesuspended particulate-free gaseous stream pass countercurrently to typically, a spray of potassium permanganate solution entering the system, as hereinafter described via spray nozzles 31a and 32a.

The substantially odor-free gaseous streams from separation zones 12 are removed from the second separation zones via

lines

47 and 48, respectively, and introduced into exhaust stack means 49 so as to form a single substantially odor-free exhaust stream. At least a portion of the substantially odor-free exhaust stream is recycled via lines 51, and fan 52 into second contacting zone 53 wherein the stream is contacted with contacting fluid at contacting conditions via

lines

5, 54, and 54a, 54b, 54c and 54d. The stream is then passed to the first contacting zones 4 via

lines

53 and 55 for admixture with the effluent passing into the pollution control process via lines '2. The remaining portion of the substantially odor-free exhaust stream is removed from the process and passed into the atmosphere as a substantially particulate-free low opacity, non-objectionable exhaust stream.

The contacting fluid enters the pollution control system, at start up, via line 15 which passes into filter system 16 which, after filtering the contacting fluid, furnishes the contacting fluid via

lines

17 and 19 and pump 18 to heater 20. The contacting fluid then exits the heater 20 by

lines

21 and 22 and pass, respectively, to separation zones 8 and 12 via

lines

22 and 23 and 21 and 26. Contacting fluid levels 24, 25, 27 and 28 are so maintained as to remove the hydrocarbonaceous particle-suspended particulate matter from the separation zones so that these compounds may be removed by

lines

39, 40, 41 and 42 and via

lines

43, 44, 45 and 46 for recycle to filter system 16. The filter system 16 does not emit any contacting fluid into the sewer due to the filter means which, typically, are discarded after each run. Further, separation zones 8 are so arranged that contacting fluid levels 24 and 27 via lines 34 and 33, respectively, and common header 35 and line 36 furnish-contacting fluid via pump 37 and line 38 to line 5 for the first contacting zones 4 and via

lines

5 and 54 to the second contacting zone 53. Also, contacting fluid levels 25 and 28, respectively, via

lines

30 and 29 provide suction for pump 31 to pass contacting fluid via

lines

31 and 32 to separation zones 12 via spray nozzle means 31a and 32a. Thus, it can be seen that the filtered water is recycled over and over again into the system. Further, in a preferred embodiment, the contacting fluid comprises water which is maintained at a pH of 8.0 to about 9.0 by means of sodium hydroxide. The contacting fluid entering the system via spray nozzles 31a and 32a perferably is a 1 percent solution of potassium permanganate spray water which is maintained by the use of sodium carbonate as abuffer to hold the pH to approximately 8.0 to about 9.0. The system does not emit any sulphur dioxide and any manganese dioxide that may be precipitated in the process is periodically removed from the potassium permanganate' solution by washing the same, by means not shown, with sodium bisulfite. I

EXAMPLE 7 Particulate emission, opacity and odor tests were conducted on the asphaltic effluents from the felt saturators in a composition asphalt roofing plant located in Minnesota. By necessity, all standards referred to herein reflect the Minnesota Air Pollution Control Agency Rules (sometimes hereinafter referred to as APC) which are believed to be fairly representative of other state standards. Actual operation of the pollution control system utilizing this invention, as shown in FIG. 2, and illustratively for purposes of this example, in FIG. 3, proceeded as follows.

The tests described in this example were conducted to determine whether the saturator effluent emissions on the asphalt saturator was in compliance with the applicable regulations of the Minnesota Air Pollution Control Agency Rules. The methods of testing employed were in accordance with the American Society of Mechanical Engineers Power Test Code 27l957, Determining Dust Concentration in a Gas Stream." The testing was accomplished by sampling simultaneously through two probes placed perpendicular to each other on a horizontal plane, about 60 feet up the stack. The cross sectional area of the circular stack was divided into concentric equal area zones and velocity pressure head readings (Pitot traverse) taken at the center of each zone. Sampling of the effluents was distributed in all of these points isokinetically, as far as possible. On account of the peculiar properties of the particulates, no extraction thimble was used for sampling; instead, the effluents were bubbled through an impinger train containing 1, 2, 3-trichloroethane as the solvent and the asphaltic substance collected by impaction in the impinger. The amount of particulates were determined by evaporating off the solvent from the contents of the impingers as well as the washings collected by rinsing off all of the sampling equipment between the probe and the meter. The evaporation'was carried out by means of a steady air stream at a controlled temperature of 70 90 F and continued until the material was free of all solvent as indicated by constant weight.

Of the two test runs on the stack of 90 minutes each, there is only a percent variation in the loadings. The result indicate good repeatability and provide a reliable representation for the specificoperating conditions. The gas flow at the sampling location-was uniform as shown by steady and even velocity profiles.

The applicable regulations on particulate emission control by the Minnesota Air Pollution Control Agency Rules are APC 5.B( 1 58(2) and 5.B(3). APC 5.B(l) specifies the emission limit based on process weight rate as E 4.10 P- for process weights up to 30 tons per hour where E is the allowable emissions, in pounds per hour and P equals the process weight rate in tons per hour.

Considering only the asphalt saturant as the process material and utilizing the above equation, when P equals 4.7 tons per-hour (asphalt consumption), E equals 1 1.5 pounds per hour. APC 5.B(2) specifies the emission limit based on Source Gas Volume rate as given in Table 2 of APC 5.4. Interpolation of data from the Table gives allowable emission of 0.08 grains per standard cubic feet for the gas volume flow of 14,800 standard cubic feet per minute for the operation considered. APC 5.B(3) sets a ceiling of 0.3 grains per standard cubic feet as the maximum allowable emission for any industrial process. The following Table summarizes the Pitot Tube and Dust Sampler Data:

TABLEI PITOT TUBE AND DUST SAMPLER DATA Both Run 1 and Run 2 were of minutes duration and Run 1 had a gas flow rate of 14,850 standard cubic feet per minute. Run 2 had a gas flow rate of 14,700 standard cubic feet per minute. The average velocity of gas at the sampling station during Run 1 was 771 feet per minute. The average velocity of gas at the sampling station in Run 2 was 764 feet per minute. Run 1 had a 75 average temperature of the gas at the sampling station. Run 2 had a 78 average temperature at the sampling station.

The results of the test are summarized below in Table II:

TABLE II Particulate Emission: Run 1 Run 2 Grains/sci" 0.0044 0.0037 Pounds/hour 0.56 0.47 Pounds/1000 lbs of gas flow 0.0084 0.0071

As stated hereinabove, the Minnesota Air Pollution Control Agency Rules APC 5.B(3) specifies the maximum allowable particulate concentration as 0.3 grains per standard cubic feet of exhaust gases. Based on a process weight rate of 4.7 tons per hour for the operation considered above, the maximum allowable emissions were 11.5 pounds per hour, in accordance with APC 5.B( l Based on Source Gas Volume, as per APC 5.B(2), the maximum allowable emissions are 0.08 grains per standard cubic feet for the 14,800 standard cubic feet per minute operation considered. Hence, the actual emission of 0.04 grains per standard cubic feet is in compliance with the maximum allowable limits as required by Minnesota Air Pollution Control Agency Rules. With respect to the opacity of the exhaust gas, tests were run in accordance with Minnesota Air Pollution Control Agency Rule APC 1 1.1A(1) pertaining to the Emission of Visible Air Contaminants. The opacity tests were confined to visual approximation of the plume density by comparing with a Ringleman chart. The plume was essentially of a white vapor type (water vapor from scrubber) with occasional, slight pale brownish tinge. Owing to the forced draft in the stack, the plume was dissipating quickly. The plume did carry, on occasions, about to 200 feet, dependent, of course, on the ambient wind velocity.

Except on three occasions, each lasting less than 2 minutes, the opacity ranged from non-existant to less than No. l on the Ringleman chart. At no time did the opacity exceed No. 2 on the Ringleman chart. The observation was made over about a 10-hour period. The conclusion was that the emissions were in compliance with APCll.lA(1).

The odor emission rate was determined in ac- .cordance with ASTM Dl39l-57, Measurement of Odor and Atmospheres (Dilution Method), and were in compliance with Minnesota Air Pollution Control Agency Rule 9.B. The effluent gas samples of approximately 10 ccs each were collected in 50 cc sterile syringes and sealed. The samples were then taken to an isolated location which was deemed odor-free and a panel of six persons were subjected to various odor tests. The tests were conducted within two hours of collecting the samples in order to decrease the chances of deterioration. The panel was subjected to the odor test, one member at a time. The 10 ccs effluent samples were diluted with 40 ccs of odor-free air and. allowed to diffuse for ten minutes, before rendering the tests. Of the six persons tested, all except one could perceive an odor, but none deemed the odor objectionable. All of the six persons in the panel were deemed to possess normal olefactory senses. The State of Minnesota APC 9.A(3) and APC 9.8 specify that, for industrial zones, the odorous material is to be diluted with four volumes of odor-free air and tested with a panel of not less than five persons, the odor being deemed objectionable if 30 percent or more of the persons in the panel exposed to the odor believe it to be objectionable. The tests indicated that the effluents from the saturator stack were in compliance with the APC rules pertaining to the Control of Odors in the Ambient Air.

Thus, the various Minnesota regulations pertaining to particulate emission, opacity and odor were satisfied utilizing the process of this invention.

PREFERRED EMBODIMENT Therefore, from the example presented hereinabove, a preferred embodiment of my invention provides a pollution control process for substantially reducing the particulate emission, opacity and odor of an asphalt saturator effluent which comprises the steps of: (a) simultaneously passingsaid effluent into a plurality of first contacting zones wherein said effluent is contacted with contacting fluid at contacting conditions; (b)

- withdrawing from said first contacting zones fluid streams comprising hydrocarbonaceous particles and finely divided suspended particulates and introducing said streams intoa plurality of first separation zones wherein said hydrocarbonaceous particles and said suspended particulates are separated from said gaseous streams at separation conditions to produce hydrocarbonaceous particle-suspended particulate-free gaseous streams; (c) withdrawing from said first separation zones said hydrocarbonaceous particle-suspended particulate-free gaseous streams and introducing said streams into a plurality, of second separation zones maintained at separation conditions so as to produce substantially odor-free gaseous streams; (d) removing from said second separation zones said substantially odor-free gaseous streams and introducing said streams into exhaust stack means so as to form a single substantially odor-free exhaust stream; (e) recycling from said exhaust stack means at least a portion of said substantially odor-free exhaust stream to a second contacting zone wherein said stream is contacted with contacting fluid at contacting conditions and then passed to said first contacting zones for admixture with the effluent of Step (a); and, (f) removing via said exhaust stack means the remaining portion of said substantially odorfreeexhaust stream.

lclaim:

I 1. A pollution control process for substantially reducing the particulate emission, opacity and odor of asphalt saturator effluent fumes which comprises the steps of:

a. passing said fumes into a first contacting zone comprising duct means containing a plurality of nozzle spray means wherein said fumes are contacted with contacting liquid maintained at a pH of from about 8.0 to about 9.0 at contacting conditions;

. withdrawing from said first contacting zone a gaseous stream comprising hydrocarbonaceous particles and finely divided suspended particulates and introducing said stream into a first separation zone wherein said hydrocarbonaceous particles and said suspended particulates are separated from said stream at separation conditions to produce a hydrocarbonaceous particle-suspended particulate-free gaseous stream;

. withdrawing from said first separation zone said hydrocarbonaceous particle-suspended particulate-free gaseous stream and introducing said stream into a second separation zone maintained at separation conditions and removing odor from said gaseous streams so as to produce a substantially odor-free gaseous stream;

d. removing from said second separation zone said substantially odorfree gaseous stream and introducing said stream into exhaust stack means;

. recycling from said exhaust stack means at least a portion of said substantially odor-free gaseous stream to a second contacting zone comprising duct means containing a plurality of nozzle spray means wherein said stream is contacted with contacting liquid maintained at a pH of fromabout 8 .0 to about 9.0 at contacting conditions and then passed to said first contacting zone for admixture with'said effluent of Step (a); and

f. removing via said exhaust stack means the effluent of the first contacting zone of step (e).

2. The process of claim 1 wherein said first contacting zone contacting conditions include contacting said fumes with a contacting liquid comprising water maintained at a pH of from about 8.0 to about 9.0 and exiting from said spray means at superatmospheric pressure'so as to produce a curtain of contacting liquid reaching the cross-sectional area of said duct means.

3. The process of claim 1 wherein said second contacting zone contacting conditions include contacting said odor-free gaseous stream with acontacting liquid comprising water maintained at a pH of from about 8.0 to about 9.0 and exiting from said spray means at superatmospheric pressure so as to produce a curtain of contacting liquid reaching the cross-sectional area of said duct means.

4. A pollution control process for substantially reducing the particulate emission, opacity and odor of asphalt saturator effluent fumes which comprises the steps of:

a. simultaneously passing said fumes into a plurality of first contacting zones comprising duct means containing a plurality of nozzle spray means wherein said effluent is contacted with contacting liquid maintained at a pH of from about 8.0 to about 9.0 at contacting conditions;

b. withdrawing from said first contacting zones gaseous streams comprising hydrocarbonaceous particles and finely divided suspended particulates and introducing said streams into-a plurality of first separation zones wherein said hydrocarbonaceous particles and said suspended particulates are separated from said gaseous streams at separation conditions to produce hydrocarbonaceous particle-suspended particulate-free gaseous streams;'

c. withdrawing from said first separation zones said hydrocarbonaceous particle-suspended particulate-free gaseous streams and introducing said streams into a plurality of second separation zones maintained at separation conditions and removing odors from said gaseous streams so as to produce substantially odor-free gaseous streams;

d. removing from said second separation zones said substantially odor-free gaseous streams and introducing said streams into exhaust stack means so as to form a single substantially odor-free exhaust stream;

e. recycling from said exhaust stack means at least a portion of said substantially odor-free exhaust stream to a second contacting zone comprising duct means containing a plurality of nozzle spray means wherein said stream is contacted with contacting liquid maintained at a pH of from about 8.0 to about 9.0 at contacting conditions and then passed to said first contacting zones for admixture with the effluent of Step (a); and,

f. removing via said exhaust stack means the effluent of the first contacting zones of step (e).

5. The process of claim 4 wherein said first contacting zones contacting conditions include contacting said fumes with a contacting liquid comprising water maintained at a pH of from about 8.0 to about 9.0 which is filtered and recycled to said contacting zones, said contacting liquid exiting from said spray means at superatmospheric pressure so as to produce a curtain of contacting liquid reaching the cross-sectional area of said duct means.

6. The process of claim 5 wherein said superatmospheric pressure is psi.

7. The process of claim 4 wherein said second contacting zone contacting conditions include contacting said odor-free exhaust stream with a contacting liquid comprising water maintained at a pH of from about 8.0 to about-9.0 and which is filtered and recycled to said second contacting zone, said contacting liquid exiting from said spray means at superatmospheric pressure so as to produce a curtain of contacting liquid reaching the cross-sectional area of said duct means.

8. The process of claim 7 wherein said superatmospheric pressure is 70 psi.

Claims

2. The process of claim 1 wherein said first contacting zone contacting conditions include contacting said fumes with a contacting liquid comprising water maintained at a pH of from about 8.0 to about 9.0 and exiting from said spray means at superatmospheric pressure so as to produce a curtain of contacting liquid reaching the cross-sectional area of said duct means.
3. The process of claim 1 wherein said second contacting zone contacting conditions include contacting said odor-free gaseous stream with a contacting liquid comprising water maintained at a pH of from about 8.0 to about 9.0 and exiting from said spray means at superatmospheric pressure so as to produce a curtaIn of contacting liquid reaching the cross-sectional area of said duct means.
4. A pollution control process for substantially reducing the particulate emission, opacity and odor of asphalt saturator effluent fumes which comprises the steps of: a. simultaneously passing said fumes into a plurality of first contacting zones comprising duct means containing a plurality of nozzle spray means wherein said effluent is contacted with contacting liquid maintained at a pH of from about 8.0 to about 9.0 at contacting conditions; b. withdrawing from said first contacting zones gaseous streams comprising hydrocarbonaceous particles and finely divided suspended particulates and introducing said streams into a plurality of first separation zones wherein said hydrocarbonaceous particles and said suspended particulates are separated from said gaseous streams at separation conditions to produce hydrocarbonaceous particle-suspended particulate-free gaseous streams; c. withdrawing from said first separation zones said hydrocarbonaceous particle-suspended particulate-free gaseous streams and introducing said streams into a plurality of second separation zones maintained at separation conditions and removing odors from said gaseous streams so as to produce substantially odor-free gaseous streams; d. removing from said second separation zones said substantially odor-free gaseous streams and introducing said streams into exhaust stack means so as to form a single substantially odor-free exhaust stream; e. recycling from said exhaust stack means at least a portion of said substantially odor-free exhaust stream to a second contacting zone comprising duct means containing a plurality of nozzle spray means wherein said stream is contacted with contacting liquid maintained at a pH of from about 8.0 to about 9.0 at contacting conditions and then passed to said first contacting zones for admixture with the effluent of Step (a); and, f. removing via said exhaust stack means the effluent of the first contacting zones of step (e).
5. The process of claim 4 wherein said first contacting zones contacting conditions include contacting said fumes with a contacting liquid comprising water maintained at a pH of from about 8.0 to about 9.0 which is filtered and recycled to said contacting zones, said contacting liquid exiting from said spray means at superatmospheric pressure so as to produce a curtain of contacting liquid reaching the cross-sectional area of said duct means.
6. The process of claim 5 wherein said superatmospheric pressure is 70 psi.
7. The process of claim 4 wherein said second contacting zone contacting conditions include contacting said odor-free exhaust stream with a contacting liquid comprising water maintained at a pH of from about 8.0 to about 9.0 and which is filtered and recycled to said second contacting zone, said contacting liquid exiting from said spray means at superatmospheric pressure so as to produce a curtain of contacting liquid reaching the cross-sectional area of said duct means.
8. The process of claim 7 wherein said superatmospheric pressure is 70 psi.