(320ar) Development and Scale-up Studies of a Smb Process for the Production of Citric Acid

With an estimated annual porduction of about 1,000,000 tons, citric acid (CA) is one of fermentation products with the highest level of production worldwide. Commercially production of citric acid is generally by submerged fermentation of sucrose or molasses. At the end of the process, the fermentation broth still contains residual sugar, protein, pigment, colloid matter, inorganic salt and other impurities. Because of this, a series of purification steps are adopted to obtain CA with the needed purity. The main refining process nowadays used in industry is the precipitation process as a calcium salt. Using this process, the production costs are high and huge amounts of environmentally harmful waste (approx. 30m3 CO2, 40 tons of wastewater and two tons of gypsum for every ton of CA) are produced. This constitutes the major obstacle for further development of the CA industry. We propose a considerably simplied process scheme: The fermentation broth containing CA and impurities is fed into the SMB adsorption zones. From the raffinate port, pure glucose is collected and recycled to the fermenter while pure CA is collected as the extract. Water is the eluent. The homemade stationary phase is a new kind of the tertiary poly(4-vinylpyridine) resin. It has a high affinity to CA while the impurities are only weakly retained. The system achieves satisfactory separation results in pilot scale. The presentation reports on simulation results and pilot scale experiments. The SMB-process is modelled by means of the commercial simulation package gPROMs®. The simulation results are validated by experimental findings obtained on a 10-column SMB system with L1.7m×Φ0.052m. The separation and scale-up studies proved that this new, environmentally benign process can replace all refining steps in the precipitation process. The yield increases about 10% while the production costs are decreased by more than 10%. Present work concentrates on scaling up the process to a 10-column SMB system with L4.5m×Ф1.2m.