LiquZd Industrial Wastes Table 11.
I
Tests on East Chicago Refinery Effluent
000-Barrel-per-Day Crude Capacity 34,000 1.0
J
410 26
TO /ND/AMA H A R B O R
Figure 6.
S U / P CANAL
General Flow of Refinery Wastes
After reducing the over-all efluent to the present 5000 gallons per minute and eliminating sulfides as a problem, the remaining pollution problems at the East Chicago refinery are concerned primarily with phenol and oil. A completely satisfactory method for removing phenols is not known a t this time, but the problem is being studied extensively by Sinclair as well as many other companies, and a satisfactory solution to the problem undoubtedly will be found. The oil problem exists a t East Chicago primarily because of suspended solids and emulsions which interfere with oil separation in the API separator. Susceptibility to separation tests indicates that the separator is removing all the oil which it is capable of removing from the effluent as it exists a t the present time. The problem, therefore, is to find a means of eliminating suspended solids and emulsions from the refinery sewers. This problem is
2.5 150 20 0
1200 80 4300
10,600 Oils, p.p.m. Oils, lb./day
Barrel-per-Day Crude Capacity 5000
23
8,440
being studied from many angles a t East Chicago, and on the basis of experimental results obtained on a pilot unit, it appears that a precoat vacuum iilter will go a long way toward solving the emulsion and suspended solids problem. The oil problem is also affected by flow in the separator, and when the flow is further reduced to 30y gallons per minute, as previously discussed, an increase in the efficiency of the separator will undoubtedly occur. As stated before, Sinclair realizes that the reduction-of-volume approach to pollution abatement has created some problems, but from the over-all standpoint, the company is convinced t h a t such an approach was the best possible for the East Chicago refinery, and that the problems which still exist and the problems which may come up in the future will be solved more easily by virtue of the fact that the effluent has been reduced in volume.
Literature Cited (1) American Petroleum Institute, “ M a n u a l o n Disposal of Refinery Wastes,” New York, 1949.
RECEIVED for review September 6, 1951.
ACCEPTED January 15, 1952.
Pulp and Paper Industry HAROLD R. MURDOCE, ConeultZng Chemical EngZneer, 2025 Peachtree Rd., N.E., Atlanta, Ga. AI1 previous production records of the pulp, paper, and paperboard industries were surmounted in 1950. Production has almost doubled in the past ten years. To cope with the resultant increase in stream pollution, national and regional organizations have been established by the industry to study the problems. These scientists with outstanding experience have fulfilled their objective well.
In another decade, modern methods and well-designed equipment will have reduced stream pollution from the pulp and paper industry to a matter of little importance. New mills bave already demonstrated this trend. A s supply and demand for pulp and paper products become more balanced, competition will force older mills to modernize their operations or close down.
R
discharged into the municipal system. Similar specific orders for correction were given the other mills. The dumping of waste sulfite liquor and the discharge of wood pulp fibers into the river underline all the orders. The mills have now submitted their plan of correction (97). The bookpaper mill (19) accepted reduction in production rather than spend over a million dollars for installatien of equipment not fully proved for correcting sulfite liquor pollution. The kraft mill has complied with t h e state order and the other sulfite mills have announced plans (21) for building a recovery plant t o cost well over a million dollars for evaporating and burning the spent calcium-base sulfite liquor. In some cases the mills are changing details in pulping technique. Complete descriptions and full specifications with flow chart and drawings have been filed. Other Wisconsin mills not cited in t h e February 21, 1950, orders (21)have also told the commission of various changes in their equipment and process to be made t o
ECEXTLY three state pollution control commissions dealt staggering economic blows t o the pulp and paper industry. The talking stage as t o how t o correct pollution nuisances appears t o have ended. Now action is demanded. I n Wisconsin, following public hearings, six pulp and paper mills were told on February 21, 1950, what, when, and how they must meet the requirements of the state commission (17, 18). A bookpaper and sulfite pulp mill built some 35 years ago was ordered t o reduce discharge of wood fiber t o a practical minimum; reduce the average daily waste sulfite liquor pollution of Fox River by not less than 40% of the average pollution during July 1 t o Xovember 30, 1948; and install storage tanks in order t o equalize release of remaining waste sulfite liquor into the river. A kraft pulp and paper mill was ordered t o complete t h e present program of modernization and install fiber save-all equipment, and t o alter existing sanitary sewer system so all sewage would be
March 1952
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Liquid Industrial Wastes correct stream pollution. The mills of Wisconsin are cleaning up their pollution situation. The mandatory order of the Washington State Pollution Commission (17 ) , compelling substantially complete waste control facilities in the four leading sulfite pulp mills, is also specific and drastic. The commission rejected a Weyerhaeuser Timber Co. request for extension of the September I, 1951, deadline. T h e mill pleaded that they were still working out the “bugs” in their magnesium-base recovery plant a t Longview, Wash. Weyerhaeuser has spent over three million dollars on this new recovery plant, which was obviously in this company’s opinion the most promising means for disposal. Deinking waste disposal is the objective of the Michigan Water Resources Commission (24) in their final order issued May 1951 t o ten paper companies who own fourteen paper mills in the Kalamasoo Valley. These mills produce a substantial portion of their pulp requirements by deinking waste paper. Plans for reduction of pollution of the Kalamasoo River by such deinking waste must be submitted t o the commission by April 1953 and compliance with the order completed by June 1954. Ten pounds of solids per ton of product was set as the minimum waste objective for all mills. T h e wood pulp industry has not been negligent in attempts t o find a practical answer for its stream pollution problem. Tangible evidence t o prove their diligence can easily be found. For instance, in 1939 the Sulfite Pulp Manufacturers’ Research League, Inc., was organized by the sulfite pulp mills of Wisconsin and Michigan (11) t o make a n extensive study of the waste sulfite liquor disposal problem. I n cooperation with the Institute of Paper Chemistry a t Appleton, Ws., they published in 1940 a comprehensive annotated bibliography on waste sulfite liquor, which in its 617 pages contained 2485 references t o the literature. The research league next made a thorough survey of the most promising existing methods and ideas. Today, these studies have resolved t o either an evaporation and burning process or an animal feed yeast process as the most hopeful means for a practical answer. Pilot plants for these and other schemes for correction have been built in Wisconsin, but t o date no sure economical process has been found. However, the program has been pursued persistently and logically since the conception of the research league. The sulfite mills in the State of Washington in 1944 showed appreciation of the need for correcting the method for disposal of sulfite liquors (11). An agreement was made with the University of Washington to pursue the project actively in cooperation with the industry. Similar organizations have studied the problem in both Canada and Sweden. These foreign laboratories and their pilot plants have been visited by many Americans during the past few years. I n 1943, the forward-looking executives of the industry organized the Xational Council for Stream Improvement of the Pulp, Paper, and Paperboard Industries, Inc., for the explicit purpose of solving pollution problems. This national council (15) today represents 90% of the pulp, paper, and paperboard production of t h e United States. It is an aggressive industrywide organization, searching constantly for technical answers to stream pollution correction. I t employs a large staff of research engineers, who function essentially through the medium of research fellowships in nine educational institutions. Cooperation with both federal and state agencies is also apparent. Many of the best technical specialists in the country are on the staff of the national council. The situation appears paradoxical. If the industry was pursuing the problem of pollution through both regional and national agencies why have these three state authorities precipitated formal legal action? Can it be that the public has pushed the government for action so hard that the commissions were forced to aggressive action, or can i t be t h a t the industry has been unduly delaying action on known technical knowledge and the 508
commissions have decided to force the issue? The technical status of the stream correction programs should be examined. The principal sources of pulp and paper process wastes which account for the pollution burden can be classified as follows: 1. Paper mill wastes, consisting of spent white water and spent coating solutions. 2. Bleach plant wastes, which are composed of spent chlorination liquors; spent alkali-wash liquors; and spent hypochloiite liquors. 3. Pulp mill wastes, containing spent bark; spent sulfite liquors; spent kraft liquors; spent semichemical liquors; spent deinking liquors; spent strawboard liquors; and spent rope and rag liquors. The three Btate commissions have pointed up the four most troublesome sources of waste in this industry-spent white waters, spent deinking liquors, spent kraft liquors, and spent sulfite liquors. Other wastes are relatively insignificant problems and are not discussed in this paper.
Removal of Suspended Solids Probably the most fundamental to all pulp and paper wastes is the need for removal of suspended fibers, A substantial re-use of spent white water a t the paper machine or in the pulp mill is existing practice in modern mills. Slime-destroying chemicals have been very helpful in reducing the frequent need for purging white water from a paper machine operation. If a paper mill is nonintegrated, spent white water can be processed in save-all equipment of modern design. There is little excuse today for not installing fiber recovery save-all equipment when wood pulp is so scarce. Bleach plant and pulp mill wastes can often be processed t o coagulate some of the soluble solids so that these residues can be removed by sedimentation and produce a clear supernatant waste with a considerably lower biochemical oxygen demand value than possessed by the untreated waste. With excellent equipment available for removing fiber and suspended substances from waste waters, a mill has no forceful excuse for discharging wastes with high suspended matter rontent into the stream. Retention basins to store raw waste until the time of high river flow are not means for correcting waste disposal in the true sense of the word. The stream is called upon somewhere downstream t o digest solids which could have been removed by the mill that creates the waste.
Treating Deinking Waste Deinking waste is the residual alkaline solution resulting from the digestion of waste papers with chemicals. Because it contains printing inks and short fibers together with starch and other chemicals used in making printing paper, deinking waste has a high biochemical oxygen demand and the bulky suspended solids do not settle readily. At Kalamazoo, Mich., the national council has installed a full-scale demonstration biological aeration plant for processing deinking waste (15). The plant consists of primary settling, aeration, secondary settling, and sludge concentration units. Wide variations in flow and detention time are possible in this entirely automatic plant. Only one operator is required for control and maintenance. The process steps include the initial removal of waste material that settles, aeration of supernatant waste with an active biological sludge, removal of t h e active sludge from the secondary settling tank, and returning part of the sludge t o the aeration tank and placing t h e remainder on disposal sludge beds or t o other dewatering means. The foremost technical problems still t o be solved are concerned with the aeration stage and particularly with sludge dewatering and disposal. A unique method for handling deinking waste is being investigatedat FitchburgPaper Go., Fitchburg, Mass., in a 22,000-gallonper-day pilot plant (15). This clarifier is simple in construction. Magnesium salts are added as a coagulant. Microscopic bubbles
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Liquid Industrial Wastesof air are introduced into the coagulated suspension, which floats t h e sludge-magnesium coagulant t o the surface, because of adsorption on the air bubbles. The sludge is removed mechanically. Results t o date indicate t h a t a removal of 80 t o 95% suspended solids and 35 t o 40% of the biochemical oxygen demand may be expected. This compares with corresponding removals by plain sedimentation of 60% suspended solids and 25% biochemical oxygen demand. T h e sludge is about 10% in consistency and easily filtered.
Treating Spent Kraft Liqnors The waste discharged from a modern 500-ton kraft mill is equivalent in both oxygen demand and volume t o a city of 100,000 people (6). Yet 95y0 of t h e residual black liquor resulting from the pulping of wood is not wasted. It is recovered by evaporation and burning the concentrated liquor in modern boilers t o recover steam and chemicals. According t o the national council (6) about one half of the 45 major kraft mills in the United States are located on large rivers or tidal waters, which a t all times supply adequate dilution for the kraft wastes. At least another quarter of the mills discharge into stream8 capable of diluting the waste t o a degree which at normal water flow is adequate. However, these streams are sources of gross pollution unless mill operations are kept at a high level of efficient performance. Process improvements , continues national council , have reduced the pollutional load of unbleached kraft pulp and paper mills in terms of oxygen-demand from 300 to a n average of 50 pounds of biochemical oxygen demand per ton of production. Seasonal lagooning of strong wastes during low water periods have indicated the possibility of reducing the figure t o below 25 pounds per ton without too costly or extensive holding basins. When measures such as these are insufficient, treatment methods become essential. By means of clarification-oxidation lagoons in some southern mills, suspended solids have been reduced t o a low concentration and the oxygen demand has been reduced from 30 t o 70% during warm weather. The possibility of toxic substances reaching the stream is eliminated. The major limitations are the large lagoon areas, disposing of voluminous residues resulting from clarification, and the need for high temperatures to obtain a high rate of biological oxidation. Laboratory experiments, according t o the national council, indicate that a very high degree of biochemical oxygen demand reduction occurs when 5 p.p.m. of nitrogen and 1 p.p.m. of inorganic phosphorus is added to the combined mill wastes, followed by adding 100 p.p.m. of seed sludge and aerating for a relatively short period. Pilot plant trials are now in process. The cost of nutrient chemicals is a serious economic problem. At a southern mill, t h e combined kraft and bleach plant waste has been treated by a lime recarbonation method (6). I n this system the residues would be burned in the lime kiln. The practically complete removal of color and suspended solids as well as 30 t o 7070 of the biochemical oxygen demand has been experienced. Difficulties in dewatering the sludge are reported. Exhaustive studies made a t the Institute of Paper Chemistry (33) show t h a t the toxic substances found in kraft waste waters are more lethal t o fish life than is biochemical oxygen demand. The minimum lethal concentration t o minnows for the more important chemicals found in spent kraft liquors is reported in p.p.m. as follows: Sodium chloride Sodium carbonate Sodium sulfate Sodium hydroxide Sodium thiosulfate Sodium sulfide Sodium sulfhydrate Hvdrocen eulfide
2500.0
250.0
100.0 100.0 5.0 3.0 0 5 1 0 0.5
1000.0 acids in soap acids in soap
March 1952
50.0 5.0 5.0
1.0
These investigators analyzed the mill waste of a typical northern kraft mill for lethal components. Summation of 35 samples showed t h a t t h e mill waste exceeded the above minimum lethal concentration t o minnows only moderately. When such wastes become diluted with river water t h e resultant is well below these minimum lethal values. While many kraft mills are located so that their dilution ratio in the stream is quite adequate, expansion of the kraft industry t o inland locations where the receiving stream a t minimum flow is more moderate will require careful consideration in the disposal of these specific toxic chemicals. When the Weyerheuser Timber Co. decided t o build a kraft board mill a t Springfield, Ore. (dS), the pollution problem was weighed carefully. Instead of conventional three-st age pulp washing they installed four stages which reduced chemical losses from this source t o 3 pounds per ton of pulp. Because t h e McKenzie River was a clean f i s h i n g s t r e a m , they decided t o take n o chances on pollution from the toxic chemicals in their kraft mill wastes. I n cooperation with . the Institute of Paper Chemistry, Figure 1. Bergstrom Tower, they constructed a Springfield, Ore. Bergstromtower ($3) t o remove a large portion of the toxic sulfides and mercaptans from the composite mixture of evaporator condensate, blow steam condensate, and digester relief condensate after separation of the turpentine fraction. This tower, shown in Figure 1, is a wood stave tank, 10 feet in diameter filled with 4 X 4 inch cross-partition tile rings t o a tower height of 28 feet. The composite waste water is sprayed over the rings from the top and scrubbed b y rising hot recovery furnace gases introduced a t the bottom of the tower. The waste which enters with an average sulfide and mercaptan content of 35 t o 40 p.p.m., respectively, discharges t o the stream with negligible quantities. T h e reaction products from the toxic chemicals are discharged with the exit gases. B y processing t h e board mill white water t o an average of 0.11 pound of fiber per 1000 gallons of discharged water and collecting floor drainings and liquor dregs in a solar pond t o avoid surge discharge into t h e stream, Weyerhaeuser has demonstrated how t o avoid stream pollution. With a low water flow when t h e river volume is 235 to 265 times the sewer flow of t h e mill, t h e dissolved oxygen content of t h e McKenzie River 250 feet below the mill sewer is over 9 p.p.m. and the biochemical oxygen demand isunder 3 p.p.m.
Spent Sulfite Liqnor The most perplexing disposal problem facing t h e pulp and paper industry has been finding a practical means for processing waste sulfite liquor. Even today no method exists which can be considered a proved economical answer applicable t o all mills. Because of t h e huge volume of this waste, the low concentration of organic matter, the corrosive properties of the liquor, and t h e scale-forming characteristics experienced during evaporation, this waste sulfite liquor problem (6) is indeed formidable. I n 1950 the industry produced 2,856,000 short tons of sulfite pulp of all grades (30). Based upon a 340-day year operation t h e
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.
Liquid #ndustriaC Wastesdaily production averaged 8400 tons of sulfite pulp. To obtain this tonnage the sulfite mills consumed 17,640 tons of pulpwood each day and produced a daily waste water volume of 420 million gallons. In this waste was dissolved 9240 tons of wood substance. Under existing conditions of operation it is possible t o isolate only 25 million gallons from the total daily waste of 420 million gallons. This 25 million gallons is the liquor obtained undiluted from the digestion operation. It contains substantially 90% of the total dissolved wood substance-8300 tons-at about 9 t o 10% concentration. Most of the efforts t o solve this perplexing proldem have been concerned with this undiluted liquor portion recovered directly from the digestion step.
Uisposal Methods for Spent Sulfite Liquor
a
Methods for disposal without economic return have failed with the exception of a few mills located near deep water. One of the earliest experiments was t,o hold the liquor in large retention basins in ant,icipation of filtration through the soil into underground strata, or the uniform release of the waste t o nearby streams. I n 1942, Tyler (31, 35) proposed bubbling air into the river water for oxygen refurnishmelit t o correct sulfite liquor contamination. The riational council conducted such elaborat,e tests on the Flambeau River in Wisconsin, downstream from a sulfite mill which discharged raw sulfite liquor into the river. The studies ( l a , 56) were conduct.ed during the summer months for several years before the experiments were abandoned as impractical. Fortification of river waters by addition of sodium nitrate t o deep water pools in the iZndroscoggiri river some 32 miles downstream from the nearest of three sulfite mills has been tried (10, 13). The chemical abates the evolution of hydrogen sulfide, formed by anaerobic decomposition of lignin sulfonates in the relatively stagnant pool. Such methods, however alleviate rather than correct the pollution condition. Two new but not generally applicable methods for disposal have been approved recently by the Washington State Pollution Commission (62). The Crown Zellerbach mill a t Camas, Wash., has constructed an elaborate system for dispersing dilute sulfite liquor wastes into the Columbia River at, midstream where water flow is consistently large and rapid. A stainless steel vertical pump (7600 gallons per minute) conveys the waste sulfite waters through 1800 feet of 30-inch rubber-lined pipe across Camas Slough t o Lady Island where the pipe discharges into a 3500-foot long, open ditch which carries the waste across the island t o another 30-inch rubber-lined pipe which extends another 760 feet into the river channel. Dilution ratio is 1 t o 20,000 a t low river flow. The commission has specified a sulfite liquor concentration below 50 p.p.m. in order t o control fungus growth in the river and protect fish life. At Everett, Wash., the Soundview and Weyerhaeuser sulfite mills with a combined daily production of 850 tons are jointly constructing a 30-inch wood stave pipeline with stainless steel fittings, joints, and bands to carry their combined waste sulfite liquor 3000 feet offshore into the deep water of Puget Sound. The final outlet will be 330 feet below the mean low tide level. There will be outlet's along the last 1000 feet t o avoid concentrated discharge. Authorities predict (2.2) that this disposal will not deplete the oxygen demand of waters a t the mouth of the Snohomish River where fish go upstream t o spawn. Because more than 80% of t h e 5-day biochemical oxygen demand value of waste sulfite liquor comes from the wood sugars (20y0of the soluble wood substance), a great deal of research has been directed toward biological means for disposal (8, 9). Activated sludge treatment indicates a 95% removal of 5-day biochemical oxygen demand. Nevertheless, this method is not promising because the maximum loading value of 1.7 pounds per d a y is too low for practical consideration and intense foaming due to the surface active lignosulfonic acids preclude any commercial pcssibilities. The trickling filter procedure (8)'indicates a, 65% removal of 5-day biochemical oxygen demand but favor-
510
able conditions in operation are uncertain because efficient aeration is hindered by heavy growth on the filter; the process is unusually sensitive t o seasonal changes; acidity of the effluent produces flora high in undesirable molds and yeasts; approximately 8 acres of filter area 6 feet deep would be required t o handle liquor from 100 tons of pulp production per day; filter media, filters, tanks, and piping must be acidproof; nitzogen and phosphorus nutrients will be necessary and expensive; and dosing rateP must be high and consequently pumping costs for recirculation will be abnormal. The national council has discontinued trickling filter studies (6, 14). Contact aeration treatment was also abandoned after several years of study. I t was found difficult to introduce air efficiently-pipe grids corroded and plugged, and diffuser stones became coated with inorganic precipit,ates. However, the highest loading of any biological disposal method was obtained-9.5 pounds of biochemical oxygen 86% of the &day biodemand per cubic yard per day-and chemical oxygen deniand was removed. The difficulties were primarily mechanical and possibly solvable, but the over-all results were not sufficiently promising for continued study. A heat hydrolysis method proposed by Oregon State C!ollege holds promise for a practical disposal meiins (6, 16), particularly for small sulfite mills. The process also appears adaptable to mills troubled with semichemical, stlawboard, rope and rag, as well as deinking wastes. The process involves heating the spent liquor t o 460" F. and retaining it under pressure a t this temperature for possibly 1 hour. Admission of air is desirable. By such treatment, sugars are hydrolyzed to cHbon dioxide and water. The lignin and other troublesome organic materials precipitate readily to an easily filt,erable form. A pilot plant, which is capable of sustained operations on sulfite liquor, is being built in Oregon.
Salable Products from Spent Sulfite Liquor There is a tremendous wealth of natural resources dissolved in waste sulfite liquors. Sugars constitute 20% and lignin sulfonate over 50% of the total solids content (16). Dissolved in the 1950 production of waste sulfite liquor were 628,320 tons of sugars and 1,570,800 tons of lignin sulfonate awaiting commercial utilization. I n spite of millions of dollars spent on such research, less than 5% of sulfite waste has found profitable use as by-products (6). In most cases these items are troublesome t o produce and have low sales value. The vast amount of fundamental technical data available on the chemistry of lignin surely contains information adequate to unlock the secrets of economic utilization. The challenge is for the organic chemist to find the key which will unravel practical utilization processes. The chemical st,ructure of lignin gives ample evidence to support optimism that useful chemicals will someday be synthesized. They can become even more lucrative than wood pulp. So far the more promising chemical utilization met,hods have been conversion to vanillin, ethyl alcohol, and fodder yeast. The production of vanillin and derivat,ives from sulfite liquor has been fulfilled, but a t a cost so high that vanillin is not available in tonnage quantities. As a flavoring agent and bact,cricide, vanillin has found only modest tonnage application. Lower production costs for vanillin could readily open mitrkets such as the synthesis of new resins and t'extile fibers. Three sulfite pulp mills in North America have built plants t o convert their waste sulfite liquor into ethyl alcohol by biological methods ( 3 , 5, 15). Ethyl alcohol yields of 30 gallons per ton of pulp and a 50% reduction in &day biochemical oxygen demand are assuring signs of progress. Further decrease in biochemical oxygen demand will be necessary if secondary treatment such as evaporation and incineration is t o be avoided. Ethyl alcohol manufactured from other raw material sources is difficult competition to overcome. Sulfite liquor alcohol hap had the advantage of wartime prices and scarcity. I n 1945 war demands created a price of over 50 cents per gallon while in the periods of 1939 and
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L t q u Z d IndustrZal Wastes1949, which represent free competitive conditions, ethyl alcohol sold for around 20 cents per gallon. When sugar mills find it necessary t o dump molasses on t h e market a t 4 t o 5 cents per gallon, producers of ethyl alcohol who use molasses have a production cost of 14 cents per gallon for 190-proof ethyl alcohol. Further competition comes from a synthetic process using ethylene, which today produces over one half of the ethyl alcohol production in the United States. This synthetic product can be produced between 12 and 15 cents per gallon. I n contrast, alcohol from waste sulfite liquor costs not less than 20 cents per gallon. Ethyl alcohol from sulfite liquor appears t o be a t least a marginal operation in a competitive market situation. Considerable optimism has been evident during the past few years over possibilities for producing fodder yeast from sulfite waste liquor. The process involves removing sulfur dioxide from the waste liquor, adjusting pH, adding inorganic nitrogen and phosphorus for nutrient, and fermenting with t h e organism Torulopsis utilis. The yeast is filtered from the broth and dried, Approximately 95% of the sugars are consumed. I n 1948 the cooperative Wisconsin sulfite mills organized the Lake State Yeast Corp. and erected a Torula yeast plant of 5 tons per day capacity at Rhinelander, Wis., in order t o determine engineering data and economics. Substantially all of the equipment had t o be corrosion resistant. Nutrients were essential and steam and power costs were found excessive (18). Recently the Rhinelander plant has experienced difficulty in selling the yeast production ($1,SO). Possibly more disturbing is that the lignin and other nonsugar wastes in the effluent leaving the yeast operation require secondary treatment before a waste water low enough in biochemical oxygen demand is obtainable for many receiving streams. Nevertheless, Hoberg Paper Mills, which was under correction orders from the state commission, considered this yeast process at t h a t time t o be the most promising of all the plans proposed for utilization. They designed a yeast plant twice as large as the Rhinelander operation (50). Based upon this experience, Hoberg concluded that a yeast plant today is economically undesirable. They have advised the state commission that they plan t o build a $1,250,000 plant for evaporating and incinerating calcium-base waste sulfite liquor (30). This is a wise decision. One or more utilization processes can be interposed between the weak liquor tanks and the evaporator and steam recovery plant. It is unlikely that a utilization process, other than steam production, will produce a n effluent which will not require some biochemical oxygen demand correction. By adopting this plan Hoberg can approach the yeast and other utilization projects cautiously with considered thinking.
Heat and Chemical Recovery from Spent Sulfite Liquor Data presented so far indicate t h a t no practical, fully proved process for either disposal or utilization of waste sulfite liquor is available. Only a few localities have surroundings favorable to disposal without treatment. The volume of the waste is so large, the concentration of solids so low, and the constituents so corrosive that the cost of disposal seems far beyond the realms of reasonable economics. Evaporation and incineration of the waste appears to be the residual method left to meet demands from government agencies. This process was the earliest of all proposals made years ago for disposition of sulfite liquor. During the past decade, technology has made remarkable progress. Venturesome research, aided by new corrosion-resistant materials, has created mahy novel processes for the pulp and paper industry. Schemes once considered impractical have now blossomed into economic realities. An example is t h e evaporation of waste sulfite liquor. For many years, attempts t o use standard design multiple effect evaporators have failed because of persistent scale formation on the tubes and body surfaces, Recently several practical methods ($6,$9) have overcome this problem. Of outstanding interest is the channel-switching sys-
March 1952
tem, invented by the Swedish engineer Rosenblad (%?), for evaporating calcium-base sulfite liquor. T h e Rosenblad principle is t o reverse or switch periodically the boiling sulfite liquor with t h e vapor and acid condensate. By means of valve control switching, this exchange of heating chambers cleans the scale from the heating surfaces thoroughly, while the evaporation keeps on continuously. The original paper (26) should be studied for further details. The channel-switching system is applicable t o any type of an evaporator. If a mill has cheap hydroelectric power or surplus power from back pressure turbines, the recompression evaporator which uses power rather than steam as the source of energy is preferable in concentrating waste sulfite liquor (4,26). Compression evaporation is a most favorable operation at high pressures and a t a temperature around 300' F. On the other hand, when power is relatively expensive, steam-operated, multiple effect vacuum evaporators are more economical. Today, the industry recognizes that by using such modern equipment designed for evaporating sulfite liquor, a calcium-base sulfite waste can be concentrated t o 52 t o 55% total solids in a practical, commercially feasible operation (14). Some years before the Rosenblad channel-switching system for evaporating calcium sulfite liquor was tried, there were numerous attempts made to substitute calcium with sodium and ammonia in order t o overcome the evaporator scaling problem. Today, the use of these other bases can no longer be justified, because of the evaporator problem. Quality of pulp, higher pulp yields, and shorter pulping cycles are the justifications needed for using sodium- or ammonia-base liquors. At present two mills are reported as producing pulp by the sodium-base process. These operations are intermittent. Three mills are now using the ammonia base continuously in full plant scale operation ($8, 94). These substitute liquors have not shown convincingly a n y advantages over the calcium-base liquor processed by evaporation and burning. Until recently, the industry has been apprehensive over burning concentrated calcium-base sulfite liquor in a recovery boiler without the use of additional fuel. Early trials had been disappointing. The Consolidated Water Power and Paper Co., however, believed it could be done (60, 26). This company solicited the cooperation of Babcock-Wilcox Co., which had previously extensive experience in burning calcium-base liquor. Both companies agreed t o conduct studies a t the Interlake Mill of Consolidated, using a Stirling boiler in the power plant. Many new features were developed during these studies, such as steam atomizing burners, gas air heaters, elevated liquor temperatures, and a specific spraying pattern. Culmination of these studies was a 20hour run without aid of supplementary fuel. The data provided sufficient evidence t o justify four Wisconsin sulfite mills t o adopt the evaporation and burning method and proceed with full scale installations. About 15 years ago, Tomlinson of the Howard Smith Paper Mills, Cornwall, Canada, experimented on substituting magnesium for calcium in sulfite pulping. H e pointed out that magnesium sublimed with the combustion gases during burning of the magnesia sulfite liquors in recovery boilers. He also noted t h a t the magnesium oxide and sulfur dioxide could be recovered from the waste gases for re-use in the process. Tomlinson is credited for introducing a new conception of recovering chemicals, as well as heat value, from waste sulfite liquor. A semicommercia1 plant was built at Cornwall in 1937. Simultaneously, Weyerhaeuser Timber Co. was studying this magnesia method at its Longview, Wash., pulp mill. In 1942 both companies consolidated their efforts and joined with Babcock-Wilcox Co., because of their broad experience in burning kraft as well as sulfite waste liquors, in t h e completion of data necessary for the construction of a full-scale magnesia-base sulfite mill at Longview. This was a bold move of Weyerhaeuser toward solving its stream polli~tion situation.
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Liquid Ilodustruial WastesCorrection of stream pollution must start within the mill process itself. The prime need for economical operation of an evaporation-burning disposal plant is to obtain the smallest volume of waste per ton of pulp with the highest possible total solid content. This requirement is common to both the calcium- and magnesium-base waste sulfite liquors. Modern equipment and technique permit intelligent control of factors such as moisture in the chips, concentration of cooking chemicals, high ratio ol chips to cooking liquor, use of indirect heating of the digester, minimum cooking temperature, and partial re-use of wadeliquor back in the digestei
Figure 2.
Magnesium Oxide- Sulfite Liquor Recovery Plant, Weyerhaeuaer Cn.
I n the magnesia process (1, %), when the digester is ready for emptying, the contents are not blown to an open blow pit, under digester pressure, but are pumped from the digester into horizontal brick-lined steel tanks, which serve as storage between the digesters and washers. By back filling with waste liquor, the contents of the digester can be removed readily. The stock density in the storage tank is maintained around 3 ' / 2 % and loss of sulfur from pressure blowing is practically eliminated. Jonsson knotters precede the pulp mshers for removal of incompletely pulped wood. Stainless steel rotary washers set in concrete vats with acid-resistant tile linings have been found satisfactory for washing the liquor from the pulp. Four such units in series with the wash mater countercurrent t o the flow of pulp, similar to conventional kraft. mill operation, is used a t Weyerhaeuser. No vacuum pump is required and the temperature of ithe pulp a t the first washer is approximately 180" F. The strong filtrate from the first washer is passed through the Cascade evaporator units, countercurrent to the hot waste gases (600' F.) leaving the recovery furnace. Then after neutralization with recovered magnesium oxide, the multiple effect, evaporators concentrate the waste liquor to 60'% total solids. This thick liquor is the feed for the recovery boiler. Concentration of the .waste liquor is followed by recovery of magnesium oxide and sulfur dioxide from the hot stack gases. Weyerhaeuser reports ( 7 ) that 88% of the magnesia and 70% .of the sulfur is recovered from the process and 7000 pounds of Steam per ton of pulp is produced a t 621 pounds per square inch and 715" F. (2, 7 ) , a,nd 350 kw.-hr. of electricty per ton of pulp (14). The magnesia process still has "bugs" to be worked out .of the operation but there is ample evidence (14) that a practical process which recovers chemicals as well as heat values is now ,available to overcome gross pollution of streams by waste sulfite jiquor. I n Figure 2 is shown R'eyerhaeuser's magnesium oxidesulfite liquor recovery plant.
512
Summary and Conclusions The year 1950 has surmounted all previous production records of the pulp, paper, and paperboard industries. In the short span of ten years, production has practically doubled. In this accomplishment, technology played a major role. Schemes which once had been considered impractical have now blossomed into economic realities. Brilliant engineering, assisted b ~ many i ne\v materials of construction, has improved processes and equipment. Numerous new pulp and paper mills have been built and many existing mills have modernized and expanded their operations in order to take full advantage of new technology and to better meet the insatiable demand of their customers for more production. Small mills have been less venturesome. Conscious of the need for correcting stream pollution, the iridustry established in 1943 the Kational Council for Stream Improvement, Inc., for the sole purpose of studying waste disposal problems within the industry. Several regional groups were also organized by local mills to focus on specific grievous problems existing within the limited area. All of these organizations are held responsible t o the industry for finding practical means for treating the mill wastes. Endowed Tvith adequate funds, they have employed scientists of outstanding experience in industrial waste problems. They have fulfilled their objective v-ell, As tangible evidence of sineerily and purpose, the industry has encouraged the pollution cont'rol comniissions t o review their research and offer helpful suggestions. The viewpoint of the state pollution control commissions is quite different from that of mana.gement. These government aut>horitieshave to function under the pressure of a public determined to have clean streams. The commissions believe that present business activity is favorable for capital investment in waste treatment facilities. They consider the time ripe for action. They are informed on technical possibilities for processing pulp and paper wastes. These men know that commercial equipment is available which can remove suspended papermaking fibers from waste waters effectively, before those waters are released to the streams. They also know that commercially proved equipment and processes exist for precipitat'ing specific substances from waste waters and that the coagulated product can be removed from the waste substantially by clarification. There is no justification for discharging suspended solids into the stream. They have probably surmised that the evaporating and burning of waste calcium-base sulfite liquor is a recent technically proved process. They are also advised of the possibilities of magnesium as a base in sulfite pulping and that this Weyerhaeuser process offers economical advantages by recovering the chemicals from the process, coincident with steam by evaporating and burning the liquor in modern design boilers. They have also learned of the successful operat,ion of the new Weyerhaeuser kraft mill in Oregon in which stream pollution is practically negligible. The pollution control comniissions must be careful in interpreting the application of promising treat,ment methods. Both the R'eyerhaeuser kraft mill and the Weyerhaeuser magnesia-base sulfite mill are brand new operations. They were built with the prime determination t'o eliminate stream pollution. Abatement of stream pollution was not considered when the older mills in the United States were constructed. The process was designed then without regard t o the judicial disposal of wastes. To apply the Weyerhaeuser disposal processes to older mills would necessitate modernizing existing processing from the digester operation through to the final pulp washing step. This would result in a t,errific financial burden on older mills, particularly those smaller units which produce from 50 to 150 tons of pulp per day. Control commissions should avoid blanket correction orders addressed to the industry. They will accomplish more by cooperating with each mill and understanding the local problem. The problem is more complex with small mills which have not been oriented on the fundamental reasons for stream sanitat'ion. If the commission keeps informed on the various proved as well as
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 3
LiquidIndustrid Waste-
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potential schemes for handling pulp and paper waste as developed in the research organizations within the industry, and discusses the situation understandingly with the mill executives, its purpose will be accomplished most effectively. Industry, on the other hand, must appreciate that the tide of public opinion is rising against industrial pollution. The good neighbor policy will pay off in many ways. It is a mistake to postpone installing save-all equipment for reducing fiber losses t o a minimum. There is also little excuse for not removing gross suspended matter, such as pigments, bark, and even raw sewage, from plant wastes. T h e commissions know t h a t necessary equipment for correcting these nuisances exists and is practical. Deinking waste treatment has not reached technical or practical status sufficient t o adequately correct stream pollution in most localities. Kraft and sulfite mills that find it difficult t o install modern devices which have been proved feasible in the newer, larger modern mills should explain their economical situation to the pollution commission in a manner which creates confidence t h a t they really intend t o solve the problem. Competent engineers on industrial waste disposal will be helpful in projecting the best means for solving these local problems. I n another decade, modern methods and well-designed equipment will have reduced stream pollution from the pulp and paper industry to a matter of little importance. Ne+ mills have already demonstrated this trend. When supply and demand for pulp and paper products becomes more in balance, competition will force older mills t o modernize their operations or close down. It is this potentially obsolete equipment in these older mills which contributes most t o the waste disposal situation of today. Spent sulfite liquors will eventually become a profitable by-product. Utilization processes for converting the soluble lignin and sugars into chemicals and other products will offer a number of opportunities. The unused spent sulfite liquor together with the residual liquors from one or more utilization operations will then be evaporated and burned in a manner already proved feasible commercially. Confidence in the future of theindustryis well justified,
Literrrture C i t e d (1) Baker, R. E., and Hutton, F., P u l p & Paper M a g . C a n . , 51, 82
(May 1950). Baker, R. E., and Wilooxson, L. S., T A P P I , 33, 187 (April 1950). (3) Ekholm, E., P u l p & Papel I n d . , 25, 54 (July 1951). (4) Elgee, H., Craig, D., and Russell, J. K., P u l p & Paper Mag. Can., 51, Convention Issue, 178 (1950). ( 5 ) Gehm, H. W., Sewage and I n d . Wastes, 23,765 (June 1951). (6) Gehm, H. W., TAPPI, 34,120A (May 1951). (7) Hazelquist, S., and Rogers, C. E., I b i d . , 33, 77A (August 1950). (8) Holderby, J. M., and Wiley, A. J., Sewage and I n d . Wastes, 22, 61 (January 1950). (9) Joseph, H. G., Sewage Works J., 19,60 (January 1947). (10) Lawrence, W. A., Sewage and I n d . Wastes, 22,820 (June 1950). (11) Murdock, H. R., IND. ENG.CHEM.,42,71A (June 1950). (12) Ibid., p. 73A (October 1950). (13) Ibid., 43, 79A (January 1951). (14) Murdock, H. R., private correspondence. (15) National Council for Stream Improvement, Int., Ann. Rept., 1950. (16) PLarl,A. I., Chem. E n g . News, 26,2950 (Oct. 4, 1948). (17) P u l p & Paper Ind., 24, 28 (February 1950). (18) Ibid., p. 23 (April 1950). (19) Ibid., p. 31 (August 1950). (20) Ibid., 25, 66 (January 1951). (21) Ibid., p. 29 (February 1951). (22) Ibid., p. 55. (2)
(23) Ibid..
D. 56.
(24j Ibid.; i. 64 (June 1951). (25) Rogers, C. E., and Jolley, R. S., Paper Trade J . (Nov. 16, 1950). (26) Rosenblad, Curt, P u l p & Paper M a g . Can., 51, 85 (May 1950). (27) T A P P I , 34, 52A (February 1951). (28) Ibid., p. 99A (March 1951). (29) Ibid., p. 100A. (30) Ibid., p. 22A (June 1951). (31) Tyler, R. G., Sewage W o r k s J., 14, 734 (April 1942). (32) Tyler, R. G., et al., Ibid., 18, 1155 (November 1946). (33) Van Horn, W. M., Anderson, J. B., and Katz, M., T A P P I , 33. 209 (May 1950). (34) Waddell, R. D., P u l p & Paper Ind., 25, 56 (July 1951). (35) Wiley, A. J., etal., Paper TTadeJ., 124, No. 12, 123 (1947). RECEIVIOD for review September 6, 1951.
ACCEPTED January 21, 1952.
STEEL INDUSTRY RICHARD D. HOAH, Mellon Institute, Pittsburgh 13,Pa. During the past 75 years steelmaking has grown from a relatively minor enterprise into an industrial giant that has been a major factor in the development of modern civilization. In common with all basic industries, steel cannot be manufactured without producing a variety of wastes. Some of these can be reworked directly, while
others must be processed for re-use. But some wastes cannot be converted to useful products economicaIly, and these pose difficult disposal problems. This paper reviews current waste treatment practice in the industry. Special emphasis has been placed on spent pickle liquor because it is a particularly vexatious problem.
HEN t h e AMERICAN CHEMICAL SOCIETY was founded in
The manufacture of steel in the United States may be mid to date from 1744, because about '/2 ton was made t h a t year. I n 1750 there were five steel furnaces in commercial production, but by 1876 the annual output of steel was only 541,900 gross tons (18). The total production of steel ingots in 1950 was 96,836,075 net tons, with equipment operating a t a n average rate of 96.9% of capacity. The production of alloy and stainless steel ingots i n t h a t year was 8,436,872 net tons (1). No early statistics on coke production are available. Some coke had been used in blast furnaces before 1850, but it had not been generally accepted as a substitute for charcoal. Four establishments, employing 14 men, made coke worth $15,250 in 1850. I n 1876, somewhat more than a million tons of coke were manufactured (18). Although, by 1860, considerable progress had been made abroad i n operating closed retort ovens t o permit
1876, no one could have predicted the tremendous size and importance the iron and steel industry would attain in the next 75 years. No other manufactured product contributed more t o the development of our civilization than steel, and this versatile metal continues to play a significant role in practically every human undertaking. Indeed, without steel, the nations of the world could never have evolved beyond agricultural societies. The first commercial pig iron in this country came from a furnace near Lynn, Mass., in 1645. By 1876 there were 714 furnaces, and the 236 t h a t were on blast t h a t year produced iron a t a n average annual rate of 7919 gross tons (18). Many of today's furnaces yield t h a t amount in less than a week. In 1950, 229 furnaces made 64,586,907 net tons of pXg iron (19)for a n average annual production of 282,039 tons per furnace.
March 1952
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