Sulfate solid disposal

The calcium sulfite or sulfate solids are allowed to settle from the solution. The regenerated solution is returned to the absorber. The solids are concentrated to around 70%. Because these solids are not a mixture of the sulfite and sulfate, their properties are far superior to lime or limestone process sludge (unless oxidation is used) and disposal should be easier. 

At the Shawnee Test Facility, major emphasis has been placed on the use of adipic acid in conjunction with forced oxidation of calcium sulfite to calcium sulfate, since this system results in better sludge dewatering properties and reduced waste solids disposal costs. Furthermore, the more tightly closed liquor loop,... 

The processes require excess limestone, and can reduce H2S to only several hundred ppmv, or reduce sulfur only 80-95%, depending on the feed coal sulfur. They produce calcium sulfide, which must be calcined to calcium sulfate for disposal. This waste solid is also generated as a mixture with fine fly ash from the original coal and excess lime from the limestone. It is much like fluidized-bed combustion waste. The large volume and high reactivity of these wastes create a number of disposal problems (30,31). 

A basic step in hydrofluoric acid manufacture is the reaction of sulfuric acid with fluorspar (calcium fluoride) to produce hydrogen fluoride and calcium sulfate. Spent alumina is also generated by the defluorination of some hydrofluoric acid alkylation products over alumina. It is disposed of or sent to the alumina supplier for recovery. Other solid residuals from hydrofluoric acid alkylation include any porous materials that may have come in contact with the hydrofluoric acid. 

The tendency in the past decades has been to replace them with solid acids (Figure 13.1). These solid acids could present important advantages, decreasing reactor and plant corrosion problems (with simpler and safer maintenance), and favoring catalyst regeneration and environmentally safe disposal. This is the case of the use of zeolites, amorphous sihco-aluminas, or more recently, the so-called superacid solids, that is, sulfated metal oxides, heteropolyoxometalates, or nation (Figure 13.1). It is clear that the well-known carbocation chemistry that occurs in liquid-acid processes also occurs on the sohd-acid catalysts (similar mechanisms have been proposed in both catalyst types) and the same process variables that control liquid-acid reactions also affect the solid catalyst processes. 

Radioactive metal wastes from the nuclear industry are of increasing concern as the amount of waste to be disposed of increases. Current treatment of nuclear wastewater involves the addition of lime, which is effective in precipitating most metals out of solution with the exception of radium (Tsezos Keller, 1983). Barium chloride (BaCl2) is used to precipitate radium from sulfur-rich effluents as barium-radium sulfate. Other treatment methods include incineration for some solid wastes, and filtration, adsorption and crystallization for liquid wastes (Godbee Kibbey, 1981). 

Fig. 1. Schematic flowsheet of uranium processing (acid leach and ion exchange) operation. Numbers refer to the numbers that appear in the boxes on the flowsheet. Operations (3), (6), (9), and (11) may be done by thickening or filtration. Most often, thickeners are used, followed by filters. The pH of the leach slurry <4) is elevated to reduce its corrosive effect and to improve the ion-exchange operation on the uranium liquor subsequently separated, In tile ion exchange operation (7), resin contained in closed columns is alternately loaded with uranium and then eluted. The resin adsorbs the complex anions, such as UC fSO 4-. in which the uranium is present in the leach solution. Ammonium nitrate is nsed for elution, obtained by recycling the uranium filtrate liquor after pH adjustment. Iron adsoibed with the uranium is eluted with it. Iron separation operation (8) is needed inasmuch as the iron hydroxide slurry is heavily contaminated with calcium sulfate and coprecipitated uranium salts. Therefore, the slurry is recycled to the watering stage (3). Washed solids from 1,6). the waste barren liquor from (7), and the uranium filtrate from (11) are combined. The pH is elevated to 7.5 by adding lime slurry before the mixture is pumped to the tailings disposal area. (Rio Algom Mines Limited, Toronto)...

Small Quantities (White Phosphorus). Wear nitrile rubber gloves, laboratory coat, and eye protection. Work in the fume hood. Five g (0.16 mol) of white phosphorus are cut under water into 5mm pellets. The pellets are added to 800 mL (0.8 mol) of 1 M cupric sulfate (127.7 g or 199.7 g of CuS04 or CuS04-5H20, respectively, dissolved in 800 mL of water) solution in a 2-L beaker. The mixture is allowed to stand for about a week with occasional stirring. The phosphorus grad-ually disappears, and a fine black precipitate of copper and copper phosphide is formed. The reaction is complete when no waxy white phosphorus is observed when one of the pellets is cut under water. The precipitate is separated, and while still wet, transferred to 500 mL of laundry bleach (5% sodium hypochlorite), and then stirred for about 1 hour to ensure complete decomposition of copper phosphide. The solids are separated and packaged for disposal. The aqueous solution is washed into the drain.33... 

There is no current commercial biologic process for the production of succinic acid. In past laboratory systems, when succinic acid has been produced by fermentation, lime is added to the fermentation medium to neutralize the acid, yielding calcium succinate (2). The calcium succinate salt then precipitates out of the solution. Subsequently, sulfuric acid is added to the salt to produce the free soluble succinic acid and solid calcium sulfate (gypsum). The acid is then purified with several washings over a sorbent to remove impurities. The disposal of the solid waste is both a directly economic and an environmental concern, as is the cost of the raw materials. Some key process-related problems have been identified as follows (1) the separation of dilute product streams and the related costs of recovery, (2) the elimination of the salt waste from the current purification process, and (3) the reduction of inhibition to the product succinic acid on the fermentation itself. Acetic acid is also a byproduct of the fermentation of glucose by Anaerobiospirillium succiniciproducens almost 1 mol of acetate will be produced for every 2 mol of succinate (3). Under certain cultivation conditions by a mutant Escherichia coli, lesser amounts of acetate can be produced (4,5). This byproduct will also need to be separated. 

At present, S02 is removed from stack gases by a chemical reaction with CaO to form CaS04. However, the disposal of the solid sulfate presents a logistic and economic problem.22 Should it be transferred over long distances to take the place of the mined coal ... 

The ratio of reactants had to be controlled very closely to suppress these impurities. Recovery of the acrylamide product from the acid process was the most expensive and difficult part of the process. Large scale production depended on two different methods. If solid crystalline monomer was desired, the acrylamide sulfate was neutralized with ammonia to yield ammonium sulfate. The acrylamide crystallized on cooling, leaving ammonium sulfate, which had to be disposed of in some way. The second method of purification involved ion exclusion (68), which utilized a sulfonic acid ion-exchange resin and produced a dilute solution of acrylamide in water. A dilute sulfuric acid waste stream was again produced, and, in either case, the waste stream represented a... 

Disposing of solids wet with organic solvents alumina and anhydrous sodium sulfate... 

One type of hazardous waste is unique a harmless solid that is damp with an organic solvent. Alumina from a chromatography column or sodium sulfate used to dry an ether solution are examples. Being solids they obviously can t go in the organic solvents container, and being flammable they can t go in the nonhazardous waste container. A solution to this problem is to spread the solid out in the hood to let the solvent evaporate. You can then place the solid in the nonhazardous waste container. The saving in waste disposal costs by this operation is enormous. 

Assumptions about the basic method of disposal of the coal-cleaning waste must be made. For this paper, we assumed that the valley-fill method would be used. In this method, a narrow downward-sloping valley near the cleaning plant is filled, in benches, from the upper end. As the upper benches reach contour level, the pile is covered with sufficient soil to retard water percolation to one-third that of an uncovered pile. The drainage from such a waste pile has the characteristics of acid mine drainage, with most of the dissolved solids being iron sulfates. 

By using this technique, operations free of calcium sulfate scaling have been demonstrated in laboratory and field installations. This seeding technique is the key to closed loop operation in which liquid leaves the system only by evaporation or in combination with the solid by-product of the scrubbing system. Disposal of this solid is discussed later. 

The Air Quality Control Systems (AQCS) using lime/limestone wet scrubbing have three basic types of chemical process equipment (1) scrubbers, (2) reaction tanks, and (3) solid-liquid separators, in addition to several auxiliary pieces of equipment such as pumps, demisters, and reheaters. The SO2 in the flue gas is transferred into the liquid in the scrubber, the sulfur in the liquid is converted to solid calcium sulfite, and calcium sulfate in the reaction tanks and solid calcium sulfite and sulfate are separated from the liquid and disposed from the solid-liquid separators such as clarifiers, vacuum filters, and ponds. 

The starting materials of the active components of catalysts are often in the form of soluble metal salts that are precipitated to form a solid precursor to a catalyst. Among the very limited soluble salts, metal nitrate is the preferred salt over fluoride, chloride, phosphate, or sulfate because of less corrosiveness and low residual anion on finished catalyst. Sometimes more expensive metal carboxylates such as formate, acetate, glycolate, or oxalate are used in the situation where disposal of nitrate is prohibited by environmental regulations or residual nitrogen is detrimental to the reaction. 

While talking about clean technologies, one may also cite the case of replacement of the hydroxy (-OH) group by a methoxy (-OCH3) group by using dimethyl sulfate as in the case of pctra-cresyl methyl ether from p-cresol. Use of methanol and a suitable catalyst, say zeolites, should be established. This would reduce much of environment-related problems, by eliminating disposal of solid effluent such as sodium sulfate. 

---