Calcium sulfate Caustic

Naphthalenesulfonic Acid. The sulfonation of naphthalene with excess 96 wt % sulfuric acid at < 80°C gives > 85 wt % 1-naphthalenesulfonic acid (a-acid) the balance is mainly the 2-isomer (P-acid). An older German commercial process is based on the reaction of naphthalene with 96 wt % sulfuric acid at 20—50°C (13). The product can be used unpurifted to make dyestuff intermediates by nitration or can be sulfonated further. The sodium salt of 1-naphthalenesulfonic acid is required, for example, for the conversion of 1-naphthalenol (1-naphthol) by caustic fusion. In this case, the excess sulfuric acid first is separated by the addition of lime and is filtered to remove the insoluble calcium sulfate the filtrate is treated with sodium carbonate to precipitate calcium carbonate and leave the sodium l-naphthalenesulfonate/7J(9-/4-J7 in solution. The dry salt then is recovered, typically, by spray-drying the solution. 

More recendy, the molten caustic leaching (MCL) process developed by TRW, Inc. has received attention (28,31,32). This process is illustrated in Eigure 6. A coal is fed to a rotary kiln to convert both the mineral matter and the sulfur into water- or acid-soluble compounds. The coal cake discharged from the kiln is washed first with water and then with dilute sulfuric acid solution countercurrendy. The efduent is treated with lime to precipitate out calcium sulfate, iron hydroxide, and sodium—iron hydroxy sulfate. The MCL process can typically produce ultraclean coal having 0.4 to 0.7% sulfur, 0.1 to 0.65% ash, and 25.5 to 14.8 MJ/kg (6100—3500 kcal/kg) from a high sulfur, ie, 4 wt % sulfur and ca 11 wt % ash, coal. The moisture content of the product coal varies from 10 to 50%. 

About 250 ml of a reaction mixture obtained by the electrolytic reduction of nitrobenzene in sulfuric acid solution and containing about 23 grams of p-aminophenol by assay is neutralized while at a temperature of 60° to 65°C, to a pH of 4.5 with calcium carbonate. The calcium sulfate precipitate which forms is filtered off, the precipitate washed with hot water at about 65°C and the filtrate and wash water then combined. The solution is then extracted twice with 25 ml portions of benzene and the aqueous phase is treated with 0.5 part by weight, for each part of p-aminophenol present, of activated carbon and the latter filtered off. The activated carbon is regenerated by treatment with hot dilute caustic followed by a hot dilute acid wash, and reused a minimum of three times. 

Limestone is the cheapest basic product (0.20/lb in 1968 0.40/kg). However, it can become coated with calcium sulfate, which can almost stop neutralization from occurring. Some kind of scouring may be necessary to prevent this. Lime may be used, but it also can become coated and rendered ineffective. Soda ash and caustic soda are other alternatives, but they cost 8 to 10 times as much as limestone.35 Sometimes limestone or lime is used to raise the pH to between 4.0 and 5.0, and the more expensive but more easily controllable soda ash or caustic soda is used to obtain the desired final pH. The only equipment needed is storage tanks for the acids and bases and mixing tanks, equipped with the proper controls. 

In most commercial processes, the compound is either derived from the sea water or from the natural brines, both of which are rich sources of magnesium chloride. In the sea water process, the water is treated with lime or calcined dolomite (dolime), CaO MgO or caustic soda to precipitate magnesium hydroxide. The latter is then neutralized with hydrochloric acid. Excess calcium is separated by treatment with sulfuric acid to yield insoluble calcium sulfate. When produced from underground brine, brine is first filtered to remove insoluble materials. The filtrate is then partially evaporated by solar radiation to enhance the concentration of MgCb. Sodium chloride and other salts in the brine concentrate are removed by fractional crystallization. 

Procedure. The above reactants are mixed thoroughly and heated in a retort or in an apparatus as described by Steinkopf Die Chemie des Thiophens, page 9). The distillate from this reaction is washed with caustic to remove 5-methyl-2-hydroxythiophene, and the organic layer is steam distilled. The crude 2-methylthiophene is dried over sodium sulfate or calcium sulfate, and then dLstilled from sodium, b.p. 113°. 

In a phenol/cresols or xylenols plant, using the conventional sulfonation and caustic fusion technologies, inorganic chemicals which are recovered are sodium sulflte, sodium sulfate and hydrated calcium sulfate also known as gypsum. These are all sellable by-products and depending on the method of treatment and recovery will fetch reasonable prices, and more importantly, will ensure a better eco-system. 

Bromic acid Bromine, anhydrous Butadiene Butane Butyl acetate Butyl chloride Butyl ether Butyl lactate Butyl mercaptan Butyl chloride Cadmium chloride Cadmium nitrate Cadmium sulfate Cadmium sulfide Calcium acetate Calcium arsenate Calcium bicarbonate Calcium bisulfide Calcium hydrosulfide Calcium carbide Calcium carbonate Calcium chlorate Calcium chloride Calcium chromate Calcium fluoride Calcium hydroxide Calcium h) pochlorite Calcium nitrate Calcium oxide Calcium peroxide Calcium phosphate Calcium stearate Calcium sulfate Calcium sulfide Calcium sulfite Cane sugar liquors Capric acid Carbamate Carbon bisulfide Carbon dioxide Carbon disulfide Carbon fluorides Carbon monoxide Caustic lime... 

Magnesia white. See Calcium sulfate dihydrate Magnesite, caustic-calcined. See Magnesium oxide... 

The major anionic impurity in most brine systems is sulfate. Control of its concentration is an issue mostly in membrane cells. In the diaphragm-cell process, sulfate passes with the rest of the anolyte into the cathode side of the cells. It can be separated from caustic soda in the evaporators and purged from the system as Glauber s salt This is covered in Section 9.4.2.1. Mercury cells are least sensitive to sulfate. Its concentration is frequently allowed to build to the point where dissolution of calcium sulfate from the salt is inhibited. The greatest problem then caused by the sulfate is a reduction in the solubility of NaCl or KCl. 

Place a sample of the scale in a beaker and add enough caustic soda solution (25% by weight) to cover the scale sample. If the sample disintegrates and forms a slurry in the bottom of the breaker, the scale is calcium sulfate (CaS04). 

Rotary kilns and, to a lesser extent, Fluo-SoHds kilns are used to calcine a wet precipitated calcium carbonate filter cake in the kraft or sulfate paper-pulp process (15). Lime is regenerated for use as a causticization reagent in recovering caustic soda for pulp digestion. Losses in lime recovery are replaced by purchased lime (see Paper Pulp). 

Where the supply water is of low hardness but high alkalinity (the major contributor to alkalinity is sodium rather than calcium), neutralization by a small addition of RW before the degasser adds back a small amount of calcium but no further alkalinity. Where the supply water is of high hardness and alkalinity but has lower levels of chlorides and sulfates, neutralization after the degasser, using caustic soda, is the preferred practice. 

Drum dryers potatoes, cereals, buttermilk, skim milk, dextrins, yeasts, instant oat meal, polyacylamides, sodium benzoate, propionates, acetates, phosphates, chelates, aluminum oxide, m-disulfuric acid, barium sulfate, calcium acetate-arsenate-carbonate-hydrate-phosphate, caustic, ferrous sulfate, glue, lead arsenate, sodium benzene sulfonate, and sodium chloride... 

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