A clarified broth from fermentation of sucrose using Aspergillus niger consists of 16.94 wt% citric acid,...

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A clarified broth from fermentation of sucrose using Aspergillus niger consists of 16.94 wt% citric acid, 82.69 wt% water, and 0.37 wt% other solutes. To recover citric acid, the broth would normally be treated first with calcium hydroxide to neutralize the acid and precipitate it as calcium citrate, and then with sulfuric acid to convert calcium citrate back to citric acid. To avoid the need for calcium hydroxide and sulfuric acid, U.S. Patent 4,251,671 describes a solvent-extraction process using N,N- diethyldodecanamide, which is insoluble in water and has a density of 0.847 g/cm3. In a typical experiment at 30C, 50 g of 20 wt% citric acid and 80 wt% water was contacted with 0.85 g of amide. The resulting organic phase, assumed to be in equilibrium with the aqueous phase, contained 6.39 wt% citric acid and 2.97 wt% water. Determine: (a) the partition (distribution) coefficients for citric acid and water. (b) the solvent flow rate in kg/h needed to extract 98% of the citric acid in 1,300 kg/h of broth using five countercurrent, equilibrium stages, with the partition coefficients from part (a), but ignoring the solubility of water in the organic phase. (c) propose a series of steps you would undertake to produce near-pure citric acid. Explain the selection of each step. (d) In part (b), how serious would it be to ignore the solubility of water in the organic phase? A clarified broth from fermentation of sucrose using Aspergillus niger consists of 16.94 wt% citric acid, 82.69 wt% water, and 0.37 wt% other solutes. To recover citric acid, the broth would normally be treated first with calcium hydroxide to neutralize the acid and precipitate it as calcium citrate, and then with sulfuric acid to convert calcium citrate back to citric acid. To avoid the need for calcium hydroxide and sulfuric acid, U.S. Patent 4,251,671 describes a solvent-extraction process using N,N- diethyldodecanamide, which is insoluble in water and has a density of 0.847 g/cm3. In a typical experiment at 30C, 50 g of 20 wt% citric acid and 80 wt% water was contacted with 0.85 g of amide. The resulting organic phase, assumed to be in equilibrium with the aqueous phase, contained 6.39 wt% citric acid and 2.97 wt% water. Determine: (a) the partition (distribution) coefficients for citric acid and water. (b) the solvent flow rate in kg/h needed to extract 98% of the citric acid in 1,300 kg/h of broth using five countercurrent, equilibrium stages, with the partition coefficients from part (a), but ignoring the solubility of water in the organic phase. (c) propose a series of steps you would undertake to produce near-pure citric acid. Explain the selection of each step. (d) In part (b), how serious would it be to ignore the solubility of water in the organic phase?