Phosphoric acid process

Dimersol is a commercial process for the dimeri2ation of propylene, butylenes, or a mixture of both, to and Cg olefins this process produces a more linear olefin than the phosphoric acid process. The reaction is conducted at ambient temperature, using a water-soluble catalyst complex (16). 

Fig. 3. Thermal phosphoric acid processes (a) wetted-waH combustion chamber (b) air-cooled combustion chamber (c) water-cooled combustion...

Cineol by Direct Absorption with Resorcin Solution. Cineol by Absorption with Resorcin after Fractionation. Cineol by Phosphoric Acid Process. 

As compared with the B.P. phosphoric acid process the results were from 4-4 per cent, higher in the case of 80 per cent, oils to 10 5 per cent, higher in the case of cajuput oil indicating 50 per cent, by the B.P. process. 

Phosphoric acid processing is usually associated with onerous conditions, involving hot strong acid, often with appreciable contents of impurities such as sulphuric or hydrofluoric acids. Limited use is made of the austenitic steels, especially 316 group. 

Triple Superphosphate (TSP). Triple superphosphate is produced by the reaction between ground phosphate rock and phosphoric acid by one of two processes. One utilizes concentrated phosphoric acid and generates obnoxious gases. The dilute phosphoric acid process permits the ready collection of dusts and obnoxious gases generated. 

The more significant commercial catalytic polymerization processes have proved to be phosphoric acid processes and sulfuric acid processes. 

Leyshon, D. W The Origin of the Modern Dihydrate Phosphoric Acid Process—Cominco 1931, A.I.Ch.E., Orlando, FL, 1990. 

Carpenter, G., and Pierce, R.R., Linings for Sulfuric and Phosphoric Acid Process... 

C. Earl, A. Davister, and E Thirion, High Strength Phosphoric Acid Process. Chem. Eng. Prog. 82, 34-37, Oct. (1986). 

Norit CAl 1400 Chemically activated by the phosphoric acid process 3.0... 

Table 2 summarizes the global material balances, and again gives the comparison with the phosphoric acid process. 

SYNTHESIS Polycondensation of a terephthalic acid with 4,6-diamino-1,3-benzenediol dihydrochloride in poly(phosphoric acid). Processing is primarily limited to variations of wet extrusion. 

Rapid cellulose dissolution in anhydrous phosphoric acid is the basis for the Akzo phosphoric acid process [36,74]. A similar concept has been practiced for making Kevlar fibers, in which anhydrous sulfuric acid is used to dissolve poly(p-phenylene terephthalamide). However, anhydrous sulfuric acid is highly corrosive and is produced by mixing concentrated sulfuric acid with small amounts of fuming sulfuric acid. 

FIGURE 10.46 Tensile stress-strain curves for 1, Fiber B (Akzo phosphoric acid process) 2, Cordenka EHM 3, Cordenka 700 4, Cordenka 660 and 5, Enka Viscose. The solid dots indicate the stress related to the reduced cross section at fracture. The hyperbola-shaped failure envelope is represented by the dashed line. (From Northolt, M.G., Boerstoel, H., Maatman, H., Huisman, R., Veurink, J., and Elzerman, H., Polymer, 42, 8249, 2001. Reprinted with permission of Elsevier B. V.)... 

Before starting to describe particular industrial processes, it should be noted that each process is based on information supplied by a different engineering and construction organization. Each of the organizations offers a range of processes to meet various dient needs. In addition, several other companies, not mentioned, offer phosphoric acid processes, and there is no intention of implying that processes offered by the companies mentioned by name are necessarily superior to those offered by other companies and does not imply any kind of endorsement by UNIDO or DFDC. 

Strontium and lanthanides (rare earths), found in igneous rocks, inhibit rehydration of the hemihy-drate to gypsum, which can cause problems in certain phosphoric acid processes. Moreover strontium causes problems in the concentration sections because strontium sulfate has a minimum solubility in 40% P2O5 acid. An extremely thin film of SrS04 causes a very pronounced reduction in the capacity of the concentration unit. 

Table 11.20. Process Requirements of the Hemihydrate Process Product Phosphoric Acid Process Hemihydrate...

Table 11.21. Raw Material and Product Analyses for Norsk Hydro Fertilizers Phosphoric Acid Processes (wt %)... 

Introduction of phosphogypsum as an additive to cement accounts for about 4 million tonnes per annum. Portland cement usually contains about 5% gypsum, which is added to control (retard) the setting time. Phosphate, fluoride, and organic impurities in the phosphogypsum are undesirable and should be reduced to acceptable levels. Material from double crystallization phosphoric acid processes is satisfactorily employed in Belgium and Japan. 

Most phosphate rocks of the fluoroapatite - type contain a significant quantity of fluorine, usually 3%-4% F by weight. In some cases up to 60% of this can be evolved during the manufacture of wet-process phosphoric acid. The remainder of the fluorine is retained in the gypsum (depending mainly on the rock composition), and most of remainder is in the filter acid 130], The fluorine is evolved from various stages of phosphoric acid processes from the reactor slurry surface, in the flash cooler, and in the concentration plant. In a dihydrate process the proportions are ------ --------------... 

Uranium occurs in most phosphate rocks, but its concentration varies from deposit to deposit. Some sedimentary rocks show notably higher concentrations than most igneous rocks. The most uranium-rich rocks found to date are those of Florida (up to 300 ppmw U), Morocco (up to 230 ppmw U), and Jordan (up to 240 ppmw U) [32,33[. In comparison, conventional uranium deposits such as pitchblende typically have a uranium content of 1,000-3,000 ppmw. When the phosphate rock is acidulated, up to 80% or 90% of the ur ium passes into solution in the phosphoric add. The exact amount of PR acidulated depends on its characteristics and the parameters of the phosphoric acid process employed. Examples of the uranium contents of different phosphate rocks and of phosphoric acids produced from them are indicated in Table 11.29. 

Figure 11.31 shows a typical flowsheet of the HCl phosphoric acid process. 

Figure 11.31. Flowsheet of the IMI Phosphoric Acid Process (HCl-Route).

Environmental Impact - The phosphoric acid process produces large amounts of phosphogypsum. The latter requires either a large land surface for disposal or a transportation system for disposal into deep sea. Dis-... 

Minford also studied the effects of four different phosphoric acid processing conditions under stress and intermittent salt-water immersion testing of 6061-T6 aluminum alloys. None of the joints pretreated by varying phosphoric acid anodizing conditions failed after 480 days exposure, even... 

Phosphate rock is a potentially valuable source of fluorine and there is currently much interest in the economic recovery of the element from both the electric furnace process and the wet phosphoric acid process (Chapter 5.2). It is estimated that the quantity of fluorine present in the annual total production of mined rock exceeds that presently mined as fluorospar, Cap2. 

---