UNDERGRO PROCESS
F LAWRENCE
K. CECIL
lnfilco Incorporated, Tulsa,
Okla.
N A recent article on T h e petroleum industry has solved the problem of dissuch modern practices as posal of oil field brines by injection into underground forapplying sufficient hydraumethods of disposal of lic pressure a t the surface waste waters from chemimations. Chemical industries with wastes that cannot cal plants Hess ( 1 ) does be treated for disposal in nearby diluting waters may find to Overcome the weight Of the earth above the botnot mention injection wells. this method applicable. The general discussion of factom of the well, resulting The petroleum industry is tors involved in finding a formation suitable for injection in general fracture of the successful in disposing daily wells and the limitations of waste quality for such disposal formation surrounding the of many millions of gallons of highly lvater may be of assistance in deciding if this method should be well, make possible the investigated by individual chemical plants. A report of disposal of much larger i n b thousands of disposal wells throughout the coun18 months’ operation of a waste-treating plant and disposal quantities of water than well points up some of the problems to be expected in could be put into a n orditry. This method should be investigated by any preparing a new type of waste for injection-well disposal. nary well drilled into the chemical industry having formation. Disposal wells t o dispose of a waste have in some cases been water that cannot be treated and received on the adjacent water tried and abandoned when all that was needed to turn failure into success was proper well completion or waste water treatment. shed. Zn some areas no suitable disposal formations exist, but wherFORMATION SELECTION ever there is a n appreciable depth of sedimentary deposits, the Care must be used to select a formation t h a t will not allow dischances for existence of such a formation are good enough to justify study by a geologist or petroleum engineer. A large posed water to pollute a fresh water stratum at some future date. amount of information on reservoir mechanics has been accumuIf the disposal formation contains salt water it is reasonable to lated by the petroleum industry and suitable core drilling and expect no future trouble from pollution of other formations. There is great variation in the quantity of water that can be study of the cores in the laboratory will provide a definite answer as to the ability of the formation to accept the waste in question received by different formations. I n some, such as the cavernous and the approximate quantity of the waste that can be received. limestones, a single disposal well will handle several thousand gallons per minute without pressure a t the surface. This grades T h e technology of well completion is adequately established and
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INDUSTRIAL AND ENGINEERING CHEMISTRY I
all the way down to dense sandstones where one well may take only 100 gallons per minute in spite of the application of as much as 2000 pounds per square inch a t the surface. In general a n industry having to dispose of several million gallons of waste water per day would not find injection wells a suitable outlet unless i t was fortunate enough to have a cavernous limestone formation not connected with a fresh water stratum. A relatively small quantity of a very concentrated or difficult waste might be disposed of by underground injection even in dense formations, and removal of this concentrated waste from the main disposal system might improve the quality of the remaining waste water so t h a t it could be received by the surface diluting water after suitable treatment. I n several oil-producing states regulatory groups have authority to issue permits for the use of selected formations for disposal purposes; i t would be well to investigate this phase of the problem before starting a disposal well. TREATMENT METHODS
Waste water must be treated so t h a t i t will not decrease the ability of the formation to receive the water, either by plugging the face of the formation or by reacting with the reservoir water to plug the formation back of the receiving face. This requires removal of suspended matter by coagulation and filtration; stabilization to prevent scaling, as by supersaturated calcium carbonate; corrosion control to prevent production of insoluble metal hydroxides; sterilization to prevent growth of baherial gel on the formation face; and freedom from dissolved substances t h a t would react with the reservoir water to produce a precipitate in the formation. The chemical composition of reservoir waters is usually some multiple, perhaps fractional, of the chemical composition of sea water. There are exceptions to this, and no formation should be used for disposal wells without a n analysis of the reservoir water to study reaction possibilities with the input water. Some reservoir waters contain considerable quantities of barium and strontium salts t h a t will produce precipitates with sulfates or chromates. Calcium and magnesium chlorides in the reservoir waters will produce precipitates of calcium carbonate and magnesium hydroxide with soluble carbonates and hydroxides. Such alkalies should be converted to a form which will not be precipitated. Generally, treatment with carbon dioxide to convert them t o bicarbonates will be better than conversion t o mineral acid salts; carbon dioxide has the advantage of being a cheap means of p H adjustment. With varying quantities of alkali in the waste water i t is practical to use a n oversize carbonation system t h a t will handle the maximum anticipated amount of alkali, with the excess carbon dioxide wasted to atmosphere a t times of lower alkali concentration. The minimum p H obtainable by carbonation will not be corrosive to a properly constructed disposal system. This is not true with mineral acid neutralization, which must be controlled carefully. Some waste waters contain organic compounds t h a t may form a solid or semisolid on contact with the tremendous surface area of the disposal formation. Some formations contain clays that swell when wetted with low-solids water, closing the formation. In adtlitioh to a theoretical study based on analyses of input and reservoir waters i t is well to simulate the disposal well by pumping the disposal water through a core sample from the formation. OPERATINGEXPERIE~CE
Chemical manufacturing plants associated 'with the petroleum industry would logically be the first to adopt for their waste waters the methods of disposal t h a t are standard for the production division. One Oklahoma chemical plant has been disposing of its waste water into a n injection well for about 8 years. The disposal formation is the Arbucltle lime, which contains salt water. The well was acidized heavily when first completed,
and ;6 reacidized twice a year to keep the disposal channels open. The waste waters contain suspended matter consisting of carbon particles and some metallic hydroxides produced from corrosion of equipment. The waste water i s sprayed onto a gravity sand filter with a shallow sand layer about 1-foot thick. Top sand is scraped each day, and new sand is added as needed. A similar chemical plant in southeast Texas mixes its waste water with oil well brines from a nearby fleld; the mixed water is given simple filtration before injection into a disposal well. The Magnolia Petroleum Company operates the joint-ownership Seeligson natural gasoline plant, processing natural gas from the surrounding oil field, near Premont in southwest Texas. The arid climate, absence of streams to furnish dilution water, high concentration of soluble salts, and presence of chromate necessitates disposal of waste water at theplant property. Evaporation would leave a soluble salts residue of 3,500,000 pounds per year; hence disposal of the treated waste water is by injection into a n underground formation. Source of Waste Water. Chemical composition of the well water is shown in Table I. I t s principal use is make-up to the cooling tower and boilers. Sulfuric acid is added t o the tower water to reduce the alkalinity t o 200 p.p.m. t o prevent degradation of the redwood cooling tower and discourage growth of algae. A proprietary compound containing sodium chromate and some sodium phosphate is added t o minimize corrosion and prevent scaling of heat exchange services. Boiler feed make-up is treated in a hydrogen ion exchanger, and some phosphate is fed internally.
Table
1.
Cooling Tower Water Analyses 1 0
P.P.M., Sample Nosa 2 3 4 0 0 ...
5 Turbiditv 225 7 ... Color (fiitered through paper) >260 17 iii 119 '95 Calcium carbonate 147 0 0 0 22 Magnesium carbonate 0 164 355 2485 85 99 Sodium carbonate 6526 1820 6780 473 3311 Sodium sulfate 5943 5943 Sodium chloride 1906 6750 849 3 21 0 0 Alkalinity (phenolphthalein) 0 2464 3 52 200 272 240 Alkalinity (methyl. orange) 12026 1718 12673 4007 13932 Total dissolved solids 168 Silica 24 168 64 113 2.1 Iron 2.1 138 0.3 30 15 Free carbon dioxide 90 0 0 ... Sample 1 = well water April 26, 1948: 2 = No. 1 concentrated seven times (calculated). 3 = No. 2 neutralized t o 200 p.p.m. alkalinity with sulfuric acid: 4 2 cooling tower circulating water January 22, 1948: 5 = coolizlg tower ciroulating water April 26, 1948.
Normal operation of the cooling tower is based on a maximum of seven concentrations. The cooling tower is designed for a circulation rate of 30,000 gallons per minute with a windage loss of approximately 0.1% and a n evaporation rate of 2.4%. In order to have an adequate safety factor, five instead of seven concentrations were used as the basis for calculating the amount of water to be blown down from the cooling tower. Based on the following formula: c =
e+w+b w f b
where c = number of concentrations - 5; e = evaporation loss, 30,000 X 0.024 = 720 gallons per minute; w = windage loss, 30,000 X 0.001 = 30 gallons per minute; b = blowdown loss, 5 = 720 30 b/30 6; and b = 150, the amount of water to the disposal system is 150 gallons per minute. The additional waste water is boiler blowdown, hydrogen ion exchanger regeneration loss, and condensed water from cooling the compressed natural gas. These are all small quantities and can be absorbed in fluctuations in the cooling water concentrations, so the disposal system is designed for 150 gallons per minute. Figure 1 shows in simplified form the sources of waste water.
+ +
+
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INDUSTRIAL AND ENGINEERING CHEMISTRY
596
Treating Plant Design. Tlic calculated composition of the tower water puts it in the brine class. A 125-gallon-per-minute treatingplant (capable for overload to 150 gallons per minute), used for several years for treating brine for disposal in the east Texas oil field and abandoned when the productive field moved on, was moved to Premont. The only changes made in the plant were omission of the primary forced draft aerator (not needed because
CONDEUSATE FEED
TOWER F R O M GAS BLOYOOWN
Figure
,,
Bwnr
,REOEyERA411
I
B
BOILER L O T
I. Source of Waste Waters
most of the wwte water is from a cooling tower), installation of additional sludge concentrators, and addition of facilities for feeding activated silica and recarbonation of the filter effluent. It was expected that the same equipment could be used, with proper changes, for the treatment of M aste water from chemic:& production. Plan and elevation of the treating y s t e m s are shown in Figure 2. Figures 3 and 4 show the general appeaiance of the treating system and details of the filters. The mixed waste waters are received in one end of an interconnected three-compartment concrete basin. The first compartment provides for oil skimming and equalization. Water is pumped fiom the middle compartment through a float-operated constant rate controller to an 11foot diameter by 15-foot high Accelator clarifier-stabilizer. Ferrous sulfate for the reduction of chromate and coagulation of suspended matter, and lime for p H control and the precipitation of metallic hydroxides are fed from dry feeders through solution tanks to the circulating slurry under the Accelator hood. The throughput water is added to the chemically impregnated slurry through a n inlet ring a t the top of the hood. The resultant slurry-mater mixture is circulated upward through an inner draft tube where activated silica is added and secondary mixing takes place. The slurry overflows downward through an outer draft tube and returns under the hood for retreatment with the throughput water flowing upward from the slurry-water interface t o the outlet launder. Chlorine is added to the water a t the launder outlet to ensure precipitation of any excess iron and sterilization of the water throughout the rest of the system. Sludge is separated from the circulating slurry and concentrated to about 90% by volume (after 5 minutcs’ settling) in two concentrators in the outer zone of the Accelator. Each concentrator is equipped with a timer-actuated diaphragm sludge discharge valve, manually adjustable; this automatically removes solids a t the rate a t which they are produced. The solids are discharged into an adjacent earthen pit with provision for pumping the supcrnatant water from the pit to the receiving reservoir. The water from the Accelator is pumped through a battery of three 7-fOot diameter pressure filters with anthracite beds t o a 10-foot dianieter by 15-foot high deai-water storage tank sei on the same level a b the Accelator tank. Each filter is mashed separately from a n elevated tank with the wash water discharging into the receiving basin. Each filter is equipped with a rate-offlow manometer for balancing the filtration rate between the filters and adjusting the wash rate. As a safeguard against failure to maintain low p H in the cooling tower or proper lime feed in the Accelator, recarbonation is provided in the clear-water tank. The gas distribution grid is set 4 feet above the bottom to avoid entrainment of gas bubbles by the vr.ell injection pump. The tank is covered with a gas outlet stack cariied high enough t o prevent operators from breathing the gas. A triplex pump takes suction from the bottom of the recarbonation tank and discharges to the disposal well through a 4inch concrete-lined pipe system designed for a maximum pressure of 1500 pounds per square inch. The 3000-foot deep disposal
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well is equipped with a plaatic.-liiied 2.5-inch tubing terminating a t about the top of the io-foot thick injection sand. Operation of the first seclions oi the gasoline plant mas st:^ tctl late in 1947, but the treating plant wag not ready until hI:~r(ali 1948. The one analysis of the cooling tolver circulating natei made on January 22, 1948, wan worthless for calculation of chcmical dosage because temporary carthen pits were the only nicaiii of disposal of waste water, anti to minimize blowdown thc tower water was being concentrated about fifteen times, The u atcr was black in color becausr oi 1c:whing of tannin rompountlh f r o i n the tower wood. Jar Tests. An extensi ric.; of jar trsts dernonstratcd that good coagulation and cla tion could not be obtained by a n y combination or reasonable quantity of aluminum sulfate, fvrrouk sulfate, and ferric sulfate, with or without activated silica, aL pH below 8 0 . This pH TVBA necessary to prevent carbonates o r hydiates reaching the reservoir water. The lowest treatment that produced an excellent, quic.k settling floc with a clear super1iat:int M A S 133 p p.m. of itliinii~iunisuliate arid 120 p.p.in. 01’ 1iydr:ttetl lime. After fi1tr:it ion through paper the supernatant gave n phenolphthalein alkdinitx of 104 p.p.m., methyl orange a l l d i n i t > of 360 p.p.m., rind :L p1-I of 9.5. Keutralization n i t h suliuric acid to 20 p.p.m. b c l i w tlic phenolphthalein rnd point , produccd, on standing a feir hours, :L small quantity of I i g l i ~flocculeiit g r a ~-white picc4pit:ttcx Thi, w:is charac-tc,riaticof :ill t11(. jar tcats a,t high plI. Plant Operation. This wcontlaiv prccipitatioii, after ~ w l u c ~ tion of pH, prevcntrd use of thc l i w ~ t i i i gplant a> intended The sccond and third cornpartmenth 01 t Iic iecciving basin were arranged for batch treatment , u i l ti i c i ~ tl o the Arcdator changcd to lhc fiist (*ompartmcrit I’liirit opci ation was started usiiig 150 p p in of aluminum siilt:ilc* :irrtl 170 p p m. of hydratctl lime, icsultirig in e\;c~~llrnt cl:iiifit*sttit)Iiliit11 a very small amount of floc over floiting thc L\cc.rl:i t o r L t u n d ~ ~toi the filtc.rs. Thtl filtratc tlischargcd to the batch b:L\iIis, nhrre it 11as neutralixrtl below t h e phenolphthalein end point and :tllon ed LO settle. Thc. wpcrii:itnnt mas repumped through thc filters to the clear well \yithout rcvxrbonation and then nits pumped to the disposal well. Xo primary treatment could be given during the time of filtration of the batch-treated water, but thc nvcinge quantity of waste water during this period was only 35 gallons per minute, bo opcr:Liion :rt a rate of 100 gallons per m i n u l r for each system worked satisE:ictorily. The secondarj precipitatc burned completely in a crucible :nid vias presumed to be wood degradation products. Heavy c~liloI irmtion for a1g:te control n :ti h i r i g uied in the cooling ton vr.
* WELL WASH TANK
Figure 9 .
Treating System Layout
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April 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
Figure 3.
Disposal Plant Layout, Receiving Basin in Foreground
This method of operation was complicated, but it did produce a water suitable for disposal in the injection well, in spite of the nineteen concentrations of the tower water a t this time. Unfortunately, no complete analysis of this tower water was made, but t h e total solids were about 33,000 p.p.m. By the end of April 1948 the black color of the tower water had faded to a rich tan and the concentrations were down to about 7 , as shown in Table I. New jar-test studies demonstrated fair clarification, with a clear filtrate of p H 7.8, using 135 p.p.m. of ferrous sulfate and a chlorine excess of 2 p.p.m. but no lime. No precipitate formed on standing, but did form if the p H was reduced further. This prevented use of recarbonation, b u t the disposal system operated satisfactorily on this basis until August 1948 a t an average rate of 60 gallons per minute.
Table
Turbidity Color (filtered through papei) Calcium carbonate Calciuni sulfate Magnesium carbonate Magnesium sulfate Magnesium hydroxide Sodium carbonate Sodium sulfate Sodium chloride Sodium hydroxide Total dissolved solids Alkalinity (phenolphthalein) Alkalinity (methyl orange) Silica Pree carbon dioxide Ovygen consumed Chromium Phosphate Iron (unfiltered) DH
II.
Cooling tower blowdown 600 900 48 207 0 135 0 0 6809 6004 0 13423 0 48 145 67 27.2 2-4 2.5 75 6.4
597
A new series of jar tests demonstrated t h a t 135 p.p.m. of ferrous sulfate and 7 p.p.m. of activated silica, but no lime or chlorine, produced good clarification at p H below 8.0 and with no precipitate on further p H reduction and standing. Treatment was revised as indicated and was now on the basis originally planned, including chromium removal, as the filtrate no longer had the typical yellow color of chromium. ADDITIONAL CAPACITY
Although the treating plant was operating satisfactorily, only four bays of an eventual fourteen-bay cooling tower had been in service, and the balance of the tower would soon be in use. The cooling load would also increase, and i t would no longer be practical t o operate the plant on the two-stage system used a t the beginning. New studies were started to learn how to clarify the “black” water at pH below Analyses of System Waters 8.0 without after-precipitaParts per Million tion on further p H reduction. Receiving basin Chlorine was not expected to Recarafter Filter Boiler Receiving hypoAccelator bonator be helpful because i t had been outlet hlowdown basin chlorite outlet outlet used heavily in the tower for 3 900 60 30 4 3 60 700 110 45 24 30 algae control at the time of 82 2 152 132 132 132 the earlier Llblack” water. 0 0 0 0 0 0 0 32 24 25 25 25 Study of paper pulp manu0 0 0 0 0 0 1 0 0 0 0 0 facturing processes disclosed 85 191 221 189 189 159 that with the tannin-type com284 4578 3987 4282 4135 3987 291 3613 3848 3547 3564 3695 pounds, chlorine, as such, will 118 0 0 0 0 0 79 1 8370 8887 7943 7950 8204 form substitution compounds 19 1 150 192 100 44 102 300 388 340 340 232 312 which have rather low water 10 60 58 52 52 55 solubility but are quite soluble 0 0 0 0 0 0 6.6 31.2 19 17.2 14.8 12.2 in alkali. Hypochlorite, how0 0.5-1.5 0.5-1.5 0-0.3 0-0.3 0-0.3 18 16 12 6 6 6 ever, forms addition com0.2 110 5.5 11 0.9 2.6 pounds which decolorize the 11 .o 8.8 8.8 8.6 8.5 8.2 dyes producing the black
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Figure 4.
Vol. 42, No. 4
Disposal Plant Filters, Accelator Tank in Background
color Tyithout setting up the solubility characteristics of the cshlorine substitution compounds ( 2 ) . Jar-test studies confirmed this, and mhen the new tower sections were placed in operation early in August 1949 and the black color appeared, the only change in operation was the addition, four times a day, of calcium hypochlorite to the receiving end o f the concrete basin in an amount sufficient to decolorize the water in the basin. This required about 120 p.p.m. of calcium h!.pochlorite (707, available chlorine) which undoubtedly is an ovurtreatment because of the intermittent addition. I t n-as not oonsidered \vort,h while to provide continuous feed for this chemical for the few months until the black color is leached from thc nmocl. Table I1 shows the chemical composition and Figure 5 the pliysic:d appearance of a series of samples collected August 25, 1949. Shortly before this the total alkalinity in the tower w:Ltcr had heen reduced from 200 to 50 p.p.m. The high total solids of the toner water as compared t o the receiving basin was c:tusetl by the relative proportions of about 15,000 gallons per day of lowsolids water from gas cooling. Particularly significant is the rcduction of color from 900 p.p.ni. in the tower to 110 p.p.m. in the receiving basin after hypochlorite. The low chromium content of the tower water may explain its high iron content. The oxygen consumed figures are interesting, although it is difficult to see how they could be used for control purposes. Turbidity and iron quantities of filter and recarbonator outlet fiamples are higher than they should be; the increase in iron content of the recarbonated sample suggests inadequate protection of the recitrbonator tank against corrosion. The most surprising item is the pI-1 of 8.2 in the final watcr. This value had been accepted as the point above which carbonate-which might cause scale in the formation by reaction with calcium chloride in the reservoir water-would appear. Yet, based on phenolphthalein alkalinity figures, there is a concentration of 88 p.p.m. ciarbonate alkalinity in the water. This indicates the fallacy of controlling operation by pH meaL?-
uremciits without a proper cv:tluaiioii 01 how the iisiial pI-1:~llialinitJ- relations may be changed by unusual substlances in solution. Control has becii cahanged to maintain no phcnolphthxlciii itllidinity in the final n x t w
Figure 5.
Water Samples
Water samples /eft t o right cooling tower blowdown. boiler blowdown. receiving basin before hbpochlorito tieatment; receiving b a s k after hvpochloritk treatment; circulating slurry in Accelator; Accelator overflow; filter effluent; recarbonated water to disposal well
Analytical work on such sarnplcs is very difficult becuusc coilditions vary so much from those on which the standard or usual analytical procedures are based. In miit: cases determination of a single constituent becomes a rcse:trcb project before the analyst is willing to sign his name t o a figurc. In these samples the chromium determinations were particularly troublesome, anti the final results are within a range rather tli:~n a specific f i g u r ~ DISPOSAL WELL
IVhen the system was first started, the ~ w lmould l titkc 31 gallons per minute at 500 pounds per square inch and 41 g:illons per minute at 1200 pounds per squarc inch. This was not ciicouraging for the event,ual capacity required. Core stutiics indicated 15% of the core material could be removed with acid, so the n-ell was acidized. Opcrations settled doKn to a c~:ip:~cit,y
April 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
of about 90 gallons per minute a t 1050 to 1300 pounds per square inch and ran this way until sometime around the middle of September 1948 when during a period of about 4 hours the pressure dropped from about 1300 t o 750 pounds per square inch. Why is not known, but it was presumed t h a t the water must have broken through to a more porous portion of the formation. Operation has continued since then on the basis of 60 to 90 gallons per minute disposal a t pressures of something on the order of 800 pounds per square inch. A second disposal well was drilled and was found t o have substantially the same capacity as the first. Thus, with both wells in service the entire disposal system has been shown to be adequate for the expected requirement of 150 gallons per minute. A complete analysis of the reservoir water was not made because such analyses from other wells in this area were available, but a special determination for barium disclosed the presence of 10 p.p.m. which was not considered high enough to interfere with the use of the well for disposal. Operation has justified this belief, FUTURE OPERATION
After the black dyes have been leached from all the tower a new jar-test study will be made to determine the best and cheapest chemical dosage. As the blowdown from the tower increases, some of the other wastes can be reduced in quantity. Probably the water from gas cooling can be treated for make-up t o the cooling tower. Now fresh water, amounting to about 25,000 gallons per day, is used for operation of the dry chemical feeders and chlorinator. Probably treated waste water can be used for all of this except the water for the activated silica feeder and reduce
599
the load on the disposal well. Elimination of these lowsolids waters will bring the concentration of the treated water more in line with the calculated results shown in Table I. CONCLUSION
After 18 months’ operation i t has been demonstrated that a treating system in general use in t h e oil fields for disposal of salt water can be used directly for treatment of waste water from a chemical plant. The presence of soluble wood compounds, after proper treatment, appears t o have no deleterious effect on the disposal well, and it is believed that a permanent solution of the waste disposal problem a t this plant has been reached. ACKNOWLEDGMENT
The author wishes to express his appreciation for help rendered by C. V. Edwards, Jr., and E. L. Stovall, Magnolia Petroleum Company, Dallas, Tex.; J. A. Upton and Jerry F. Gleason, Jr., Magnolia Petroleum Company, Premont, Tex.; Cover C. Porter, Southland Paper Mills, Lufkin, Tex.; Joe M. Young, Infilco Inc., Houston, Tex.; and H. B. Gustafson and A. S. Repa, Infilco Inc., Chicago, Ill. LITERATURE CITED
(1) Hess, R. W., Sewage Works J., 21, No. 4, 674 (1949). (2) Pulp and Paper Industry, United States and Canada, Joint
Executive Committee on Vocational Education, “Manufacture of Pulp and Paper,” Vol. 3, seo. 7, p. 12, par. 19, 1937 I~BCEIVED January 23, 1980.
NEUTRALIZATION OF ACID WASTES B. W. DICKERSON
AND
R. M. BROOKS
Hercules Powder Company, Wilmington, Del.
N THE manufacture of T h e solution to a difficult waste acid neutralization occurred when the percentproblem is outlined. The acids handled were nitric and nitrocellulose a t the age of sulfuric acid rose Parlin, N. J., plant of sulfuric, and they varied widely in volume, concentration, above 1.3%. This seriously and ratio. Neutralization was accomplished effectively the Hercules Powder Cominhibited t h e r e a c t i o n . pany, large quantities of in a multiple unit reaction chamber provided with twoSince there was no chance point pH controlled addition of dolomite lime slurry. water are used which beof providing additional come contaminated with Use of a multicompartment chamber eliminated effect of waste water for dilution, nitric and sulfuric acids. rate of flow. pH controllers employed immersion electhe use of slaked lime was The concentrations of these trodes placed directly in reaction chambers. Design and a necessity. Studies of are low, ranging from 0 to operating data are given. available material in the about 1.50/, as sulfuric acid. North Jersey area revealed The percentage of each acid that a burned dolomite varies widely. The total quantity of acid waste water discharge stone containing about 47.5% calcium oxide, 34.3% magnesium varies with process operations and wide fluctuations are exoxide, and 1.8% calcium carbonate was the most satisfactory and perienced during very short periods of time, from as low as 2000 economical, While the authors did not know it at the time, gallons per minute up to 10,000gallons per minute maximum. this stone provided the additional advantage of holding residual Originally, provision was made for collection of process waste sulfation to a very minimum, an impossibility with any of the waters into one main trunk line sewer, which conveyed them high calcium limes where such concentrations of sulfuric and across the plant property and into the South River, As time nitric acids are t o be neutralized (1). passed other acid wastes from plant operations were connected The original plant was designed for manual control of all into this sewer so t h a t today practically all wastes are carried operations and neutralization was to be accomplished in a in this one line. They are still preponderantly sulfuric and several hundred-foot section of the acid sewer itself. nitric acids. The plant comprised a Dracco vacuum system for unloading During 1941, it became necessary to provide for neutralizathe lime from box cars and delivering it into an elevated storage tion of these acid waters. I n the studies which were made of the bin holding about 50 tons. The matcrial then flowed by gravity problem, it was found that the normal practice’of using crushed from the storage bin into a Hardinge Feedometer having a limestone was not applicable since sulfation of stone particles maximum capacity of 58 tons per day. The measured materia
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