Phosphoric acid evaporation

Major equipment components in phosphoric acid plants are phosphoric acid evaporators, barometric condensers, storage tanks and... 

The codeine that occurs naturally in small amounts in opium is isolated from the aqueous morphine alkaloid mother liquors by immiscible extraction with a nonaqueous solvent. Dilute sulfuric acid is employed to extract the codeine sulfate from the nonaqueous solvent. This solution is evaporated, crystallized, and recrystallized. The alkaloid is precipitated from a sulfate solution by alkali and purified, if necessary, by alcoholic crystallization. It is converted into the phosphate by solution in phosphoric acid, evaporation, crystallization, centrifugation, and drying. 

FIGURE 10.6 Emission control devices used with the vapor from a phosphoric acid evaporator to decrease fluoride emissions. The water used to condense steam by direct contact with cold water also serves to control fluoride vapor losses quite efficiently. (From Slack [55], page 747, by permission, Marcel Dekker, Inc.)... 

Collect sample in impinger containing alkaline ethanol add phosphoric acid evaporate add phosphate buffer and toluene to extract derivatize with PFPA analyze toluene layer... 

Fig. 22.1 (a) BoL phosphoric acid evaporation rates from Celtec MEAs as a function of temperature, (b) Phosphoric acid evaporation rate from a Celtec MEA operated at 160 °C over a period of 1 year (/e/t axis) and... 

Alloy Performance in Phosphoric Acid Evaporator (71% Phosphoric Acid at 440°F)... 

Phosphoric acid evaporation Proton conductivity, IR-drop increase Evaporation,/(T,p)... 

The phosphoric acid may be recovered by diluting the residue in the three-necked flask with water, filtering, and then evaporating with a little nitric acid to a concentration of about 85 per cent. 

Solvent extraction—purification of wet-process phosphoric acid is based on preferential extraction of H PO by an organic solvent vs the cationic impurities present in the acid. Because selectivity of acid over anionic impurities is usually not sufficient, precipitation or evaporation steps are included in the purification process for removal. Cmde wet-process acid is typically concentrated and clarified prior to extraction to remove post-precipitated sludge and improve partition of the acid into the solvent. Concentration also partially eliminates fluoride by evaporation of HF and/or SiF. Chemical precipitation of sulfate (as Ba or Ca salts), fluorosiUcates (as Na salt), and arsenic (as sulfides) may also be used as a prepurification step preceding solvent extraction. 

Commercial condensed phosphoric acids are mixtures of linear polyphosphoric acids made by the thermal process either direcdy or as a by-product of heat recovery. Wet-process acid may also be concentrated to - 70% P2O5 by evaporation. Liaear phosphoric acids are strongly hygroscopic and undergo viscosity changes and hydrolysis to less complex forms when exposed to moist air. Upon dissolution ia excess water, hydrolytic degradation to phosphoric acid occurs the hydrolysis rate is highly temperature-dependent. At 25°C, the half-life for the formation of phosphoric acid from the condensed forms is several days, whereas at 100°C the half-life is a matter of minutes. 

Condensed Phosphoric Acid. The largest use of polyphosphoric (superphosphoric) acid is as an intermediate in the production of high quahty Hquid fertilizers. The TVA pioneered the development of electric-furnace superphosphoric acid for this appHcation. However, wet-process superphosphoric acid prepared by evaporation of water from wet-process phosphoric acid has almost completely replaced furnace-grade acid in fertilizer manufacture. 

Both mono- and disodium phosphates are prepared commercially by neutralization of phosphoric acid using sodium carbonate or hydroxide. Crystals of a specific hydrate can then be obtained by evaporation of the resultant solution within the temperature range over which the hydrate is stable. For the preparation of trisodium phosphate, sodium hydroxide must be used to reach the high end pH because CO2 cannot be stripped readily from the solution above a pH of near 8. 

The general manufacturing scheme for phosphate salts is shown in Figure 11. Condensed phosphates are prepared from the appropriate orthophosphate or mixture of orthophosphates, so the preparation of orthophosphates must be considered first for the manufacture of any phosphate salt. Phosphoric acid is neutralized to form a solution or slurry with a carefully adjusted acid/base ratio according to the desired orthophosphate product. The orthophosphate may be recovered either by crystallization from solution, or the entire solution or slurry may be evaporated to dryness. The dewatering (qv) method is determined by the solubihty properties of the product and by its desired physical properties such as crystal size and shape, bulk density, and surface area. Acid orthophosphate salts may be converted to condensed phosphates by thermal dehydration (calcination). 

As of 1993—1994, over 70% of sulfuric acid production was not sold as such, but used captively to make other materials. At almost all large fertilizer plants, sulfuric acid is made on site, and by-product steam from these sulfur-burning plants is generally used for concentrating phosphoric acid ia evaporators. Most of the fertilizer plants are located ia Florida, Georgia, Idaho, Louisiana, and North Carolina. In the production of phosphate fertilizers, the primary role of sulfuric acid is to convert phosphate rock to phosphoric acid and soHd calcium sulfates, which are removed by filtration. 

Evaporators have performed successfully in a number of industrial applications. Typical materials that are processed in evaporators include Caustic Soda, Caustic Potash, Sodium Carbonate, Sodium Dichromate, Sodium Nitrate, Ammonium Nitrate, Phosphoric Acid Superacid, Potash, Urea, Glue, Glycerine,... 

Free hypophosphorous acid is obtained by acidifying aqueous solutions of hypophosphites but the pure acid cannot be isolated simply by evaporating such solutions because of its ready oxidation to phosphorous and phosphoric acids and disproportionation to phosphine and phosphorous acid (Fig. 12.16). Pure H3PO2 is obtained by continuous cxiraction from aqueous solutions into Ft 0 it forms white crystals mp... 

Cyclohexanedione (5) 2,5-Dicarbethoxy-l,4-cyclohexanedione (10 g) is suspended in a solution of 34 g of 85 % phosphoric acid, 250 ml of water, and 5 ml of ethanol in a 500-ml round-bottom flask. The mixture is refluxed for 5 days (or until all the solid material has dissolved), cooled, and extracted six times with 100-ml portions of chloroform (or better, continuously extracted with chloroform). The combined chloroform extracts are dried (sodium sulfate) and the solvent is removed (rotary evaporator). The residue on distillation affords 1,4-cyclohexanedione, bp 130-133720 mm. The product solidifies and may be recrystallized from carbon tetrachloride, mp 11-19°. 

When the entire quantity of the phosphoric acid has thus been added, agitation of the mixture is continued for about a half-hour or more to insure complete conversion. The precipitate is then allowed to settle, the supernatant liquid is drawn off, and the residue is filtered. The precipitate thus separated may, if desired, be washed with acetone and is then dried by evaporation to constant weight. It forms a fine, white, impalpable powder consisting of pure monobasic amphetamine phosphate. 

One gram of 6,7-dihydro-5H-dibenz[c,e] azepine hydrochloride was dissolved in water, made alkaline with concentrated ammonia, and the resultant base extracted twice with benzene. The benzene layers were combined, dried with anhydrous potassium carbonate, and mixed with 0.261 g of allyl bromide at 25°-30°C. The reaction solution became turbid within a few minutes and showed a considerable crystalline deposit after standing 3 A days. The mixture was warmed VA hours on the steam bath in a loosely-stoppered flask, then cooled and filtered. The filtrate was washed twice with water and the benzene layer evaporated at diminished pressure. The liquid residue was dissolved in alcohol, shaken with charcoal and filtered. Addition to the filtrate of 0.3 gram of 85% phosphoric acid in alcohol gave a clear solution which, when seeded and rubbed, yielded 6-allyl-6,7-dihydro-5H-dlbenz[c,e] azepine phosphate, MP about 211°-215°C with decomposition. 

Benzhydryl 3-carbamoyloxymethyl-7j3-(2-thienylacetamido)-70 -methoxydecephalosporanate (300 mg) in 0.5 ml in anisole and 2.5 ml of trifluoroacetic acid is reacted for 15 minutes at 10°C. The resulting mixture is evaporated at reduced pressure and flushed twice with anisole. The residue is dissolved in methylene chloride and extracted with 5% sodium bicarbonate solution. The aqueous solution is adjusted to pH 1. B with 5% phosphoric acid and extracted with ethyl acetate. The organic solution is dried and evaporated to yield the pure 3-carba-moyloxymethyl-70 -methoxy-7/3-(2-thienylacetamido)decephalosporanic acid, MP 165°C to 167°C. This may then be converted to the sodium salt. 

A solution of 75 g (Mo mol) of 1,3-propanolamine and 202 g of triethylamine in 100 cc of absolute dioxane Is added dropwise at 25°C to 30°C while stirring well to a solution of 25.9 g (Vio mol) of N,N-bis-( -chloroethyl)-phosphorlc acid amide dichlorlde in 100 cc of absolute dioxane. After the reaction is complete, the product is separated from the precipitated triethylamine hydrochloride and the filtrate Is concentrated by evaporation In waterjet vacuum at 35°C. The residue Is dissolved in a large amount of ether and mixed to saturation with water. The N,N-bis-( -chloroethyl)-N,0-propylene phosphoric acid diamide crystallizes out of the ethereal solution, after it has stood for some time in a refrigerator, in the form of colorless water-soluble crystals. MP 48 C to 49°C. Yield 65% to 70% of the theoretical. 

A solution of bis-triethylamine phosphate was prepared by slowly adding 2.36 ml of B5% phosphoric acid to 20 ml of acetonitrile containing 9.9 ml of triethylamine at 20°C. This solution was added to a stirred solution of 4.70 g of 9a-fluoro-11(3,170,21 -trihydroxy-160-methyl-1,4-pregnadiene-3,20-dione 21 -methanesulfonate and 20 ml of acetonitrile. The mixture was heated under reflux for four hours and then evaporated under reduced pressure to a volume of 12 ml. This mixture was a concentrated solution of 9a-fluoro-11(3,170,21 -tri-hydroxy-160-methyl-1,4-pregnadiene-3,20-dione 21 -phosphate triethylamine salt with some inorganic phosphate. 

A characteristic of the group (a) of resins is that they air-dry solely by solvent evaporation and remain permanently solvent soluble. This fact, combined with the need to use strong solvents, makes brush application very difficult, but sprayed coats can be applied at intervals of one hour. A full vinyl system such as (o) possesses excellent chemical and water resistance. Many members of group (o) have very poor adhesion to metal, and have therefore been exploited as strip lacquers for temporary protection. Excellent adhesion is, however, obtained by initial application of an etching primer the best known of such primers comprises polyvinyl butyral, zinc tetroxy-chromate and phosphoric acid. 

B. exo-cis-Bicyclo[3.3.0]octane-2-carboxylic acid. A mixture of 100 g. (0.440 mole) of 2-(trichloromethyl)bicyclo[3.3.0]octane and 500 ml. of 85% phosphoric acid is put into a 1-1. three-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer. The mixture is stirred and heated at 150° for 16 hours, during which time it evolves hydrogen chloride and darkens. The product is then allowed to cool and is poured into a separatory funnel. One liter of water is added and the resulting mixture is extracted with four 250-ml. portions of ether. The combined ether extract is then extracted with four 250-ml. portions of 2% aqueous sodium hydroxide (Note 9), and the resulting alkaline extract is washed with 100 ml. of ether to remove any neutral material (Note 10). The alkaline extract is acidified (to pH 2-3) with concentrated hydrochloric acid, and the oil which precipitates is extracted with three 250-ml. portions of ether. The resulting ether extract is dried with 15 g. of magnesium sulfate, filtered, and evaporated at 50° (30 mm.). The residue is then distilled at reduced pressure to obtain 29-32 g. 

Ny lon-6 (108 g) carpet backed with calcium-carbonate-filled latex and polypropylene was charged to a 1000-mL three-neck round-bottom flask (equipped with a condenser) with 6 mL of 85% phosphoric acid. Superheated steam was injected continuously during a 45-min period. The vapor temperature of the reaction medium was 250-300°C. The volume of distillate collected was 1065 mL. The distillate contained 1.9% e-caprolactam (as determined by GC), which corresponded to a crude yield of 37.5%. The distillate was fractionated in a distillation column and the nonaqueous phase removed. The remaining aqueous phase was treated with 2% potassium permanganate at 40-50°C for 2 h. Evaporation of... 

---