Acid production flowsheets

Fig. 23.1. Simplified single contact sulfuric acid production flowsheet. Its inputs are moist feed gas and water. Its outputs are 98 mass% H2S04, 2 mass% H20 sulfuric acid and dilute S02, 02, N2 gas. The acid output combines gas dehydration tower acid, H2S04 making tower acid and liquid water. The equivalent sulfur burning acid plant sends moist air (rather than moist feed gas) to dehydration. Appendix V gives an example sulfur burning calculation.

In the acid deficient flowsheet the acid released from A1(N03)3 hydrolysis was neutralized to give an organic product containing 0.5 M U02(N03)2 but only 0.05 M HN03. The A1(N03)3, Na2Cr207 and FPs were retained in the aqueous raffinate from the extraction section, while the organic product was passed to the U/Pu partition contacter. 

Fig. 1.4. Double contact sulfuric acid manufacture flowsheet. The three main S02 sources are at the top. Sulfur burning is by far the biggest source. The acid product leaves from two H2SO4 making towers at the bottom. Barren tail gas leaves the final H2S04 making tower, right arrow.

Fig. 5.1. Spent sulfuric acid regeneration flowsheet. H2S04(f) in the contaminated spent acid is decomposed to S02(g), 02(g) and H20(g) in a mildly oxidizing, 1300 K fuel fired furnace. The furnace offgas (6-14 volume% S02, 2 volume% 02, remainder N2, H20, C02) is cooled, cleaned and dried. It is then sent to catalytic S02 + Vi02 —> S03 oxidation and H2S04 making, Eqn. (1.2). Air is added just before dehydration (top right) to provide 02 for catalytic S02 oxidation. Molten sulfur is often burnt as fuel in the decomposition furnace. It provides heat for H2S04 decomposition and S02 for additional H2S04 production. Tables 5.2 and 5.3 give details of industrial operations.

Extractants derived from the carbamoylmethylphosphoryl moiety (CMP) were studied in the phosphonate, phosphinate, and phosphine oxide classes. Our studies focused on dihexyl-N,N-diethylcarba-moylmethylphosphonate, DHDECMP, hexyl hexyl-N,N-diethylcarbamoyl-methylphosphinate, HHDECMP, and octyl(phenyl)-N,N-diisobutylcarba-moylmethylphosphine oxide, 0D[ IB]CMP0. The three types of CMP extractants were compared on the basis of nitric acid and extractant dependencies for Am(III), solubility of complexes on loading with Nd(III) and U(VI), and selectivity over fission products. On the basis of the above data two conceptual flowsheets were developed. The first flowsheet involves the extraction of all of the actinides from HLLW using 0.4 M 0D[IB]CMP0 in DEB. The second flowsheet involves the extraction of all of the actinides from dissolved spent LWR fuel using 0.8 M DHDECMP in DEB. 

A depressant system developed for beneficiation of Ta/Nb-Zr ores involves oxalic acid-hydro fluoro silicic acid and depressant SHQ. SHQ is a mixture of a low-molecular-weight acrylic acid and condensation product of disulphonic acid (Suspendol PKK, manufactured by Cognis, Germany). After the development of the final reagent scheme, a series of locked-cycle tests were performed using the flowsheet shown in Figure 23.7. 

Figure 7. Flowsheet of the acetic acid process 1) reactor, 2) separator, 3) scrubber, 4) light ends separator, 5) drying column, 6) product recovery, 7) product finishing.

ICFs Commercial Process. In 1960 ICI constructed a concentration plant using this extractive distillation process (18) with a capacity of 16,000 tonnes/ annum of product acid (99.5 wt% HNO3) which has subsequently been extended. A flowsheet is given in Figure 8, and the process description is as follows. 

TBP is a sufficiently powerful extractant for actinides that it may be used in diluted form. Dilution improves the hydrodynamic properties of the solvent, allowing more complete and rapid phase disengagement. Typically concentrations of 20-30 v/o TBP in OK are used in process flowsheets. Although TBP is relatively stable as an extractant, radiolysis does lead to the formation of some acidic phosphate esters, HDBP and H2MBP, which can impair process performance.289 An aqueous alkali wash of the recycled solvent is usually carried out to remove those by products. Radiolytic degradation of the diluent in the presence of nitric acid can result in the formation of hydroxamic acids,290 which can lead to fission product retention by the organic phase. Again the solvent wash is used to prevent the accumulation of such species. A comprehensive account of the industrial utilization of TBP has recently been published.291... 

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