Comparison between forced circulation evaporation crystallization and DTB crystallization process, Kang Jinghui evaporator editor will talk about the comparison between forced circulation evaporation crystallization and DTB crystallization process.
At present, domestic ammonium sulfate basically comes from by-products of non-chemical fertilizer production industries, such as caprolactam, sulfuric acid tail gas desulfurization, electrowide desulfurization, acrylonitrile, methyl methacrylate, zinc oxide and other by-products in the coking industry.
Since ammonium sulfate is mostly a by-product, it is mainly discharged into the main system in the form of ammonium sulfate aqueous solution, so evaporation, concentration and crystallization have become the commonly used process routes for the extraction of ammonium sulfate, and forced evaporation crystallization and DTB evaporation crystallization are two common concentration processes.
1. Forced circulation evaporation crystallization process
Material flow direction: the solution is preheated by the condensate preheater and then enters the one-effect evaporator, and the heat exchange flash evaporation is carried out in the one-effect evaporator, and the solution after flash evaporation uses the pressure difference between the effects to enter the two-effect evaporator and then flashes and concentrates, and the concentrated solution is transported to the thickener by the two-effect discharge pump through the cyclone, and then enters the centrifuge for solid-liquid separation, the ammonium sulfate crystals can be directly packaged or the crystallized products are dried, and the mother liquor returns to the evaporation system after the mother liquor tank.
Flow direction of steam and condensate: the heat source of the first-effect heating chamber is live steam, and after the live steam in the first-effect heating chamber is heated and condensed, the condensate enters the first-effect condensate preheater to preheat the raw materials; The secondary steam generated by the first-effect separation chamber enters the second-effect heating chamber for heat exchange and condensation, the condensed condensate enters the condensate tank for collection, and the secondary steam generated by the second-effect separation chamber enters the indirect condenser for condensation and is recovered to the condensate tank.
2. DTB evaporation crystallization process
Material flow direction: the solution enters the DTB crystallizer, the solution is transported to the crystallization evaporator by the circulating pump to heat the solution to a superheated state, the superheated ammonium sulfate solution enters the DTB crystallizer for low-temperature flash evaporation and crystallization, and the solid-containing solution is then transported to the cyclone through the discharge pump to improve the solid content, and after the crystallization solution is centrifugally separated, the mother liquor returns to the DTB evaporation crystallizer, and the crystallized product can be packaged or dried again.
Steam condensate flow direction: After the raw steam enters the crystallization evaporator for condensation, the condensate is recovered and reused, and the secondary steam flashed out in the DTB evaporation crystallizer enters the indirect condenser for condensation recovery.
3. Comparison between forced circulation evaporation crystallization and DTB crystallization process
Compared with DTB evaporation crystallization, forced circulation evaporation crystallization has different advantages, suitable for different production conditions, DTB evaporation crystallization can be selected for small processing capacity and certain requirements for the particle size of crystalline products, on the contrary, forced circulation evaporation can be selected for relatively large treatment capacity and no requirements for crystalline products. In addition, when selecting the two production processes, it is necessary to consider the investment of the overall system, maintenance costs, production consumption costs, the technical level of the operators and other factors, and choose different production processes according to different situations.