This column is based on “Epichlorohydrin Production from Propylene – Cost Analysis,” a report published by Intratec. It can be found at: www.intratec.us/analysis/epichlorohydrin-production-cost.
Epichlorohydrin, (also known as ECH and chloromethyloxirane), is an organochlorine compound and a highly reactive epoxide that is widely used in the production of epoxy resins. Produced with purities of greater than 98%, epichlorohydrin is a clear, colorless liquid. At commercial scale, epichlorohydrin is mainly produced via chlorohydrination of allyl chloride, obtained in turn from the chlorination of propylene at high-temperature. Epichlorohydrin is mainly used in the production of bisphenol A, a raw material for epoxy resins, glycerol, and elastomers.
The process under analysis comprises three major sections: allyl chloride reaction; propylene recovery; and epichlorohydrin (ECH) production. Figure 1 presents a simplified flow diagram.
Allyl chloride reaction. Initially, chemical-grade propylene is preheated, mixed with chlorine and fed to a reactor where the chlorination reaction is carried out. The reaction occurs in the vapor phase, generating allyl chloride and byproducts. The chlorination products are cooled and then directed to the prefractionator, where a stream rich in organic chlorides is separated from unreacted propylene and hydrogen chloride. The organic chlorides are routed to two distillation columns for the removal of light-end impurities and heavy-end impurities.
Propylene recovery. The distillate from the prefractionator is washed countercurrently with water in an absorber, in such a way that the HCl is absorbed. This process forms an HCl solution, which is removed from the column bottom. The gaseous stream from the overhead of the absorber is fed to a caustic scrubber, where residual hydrogen chloride is removed. The washed propylene gas is compressed in a multi-stage compressor and then recycled to the preheating stage.
Epichlorohydrin production. The allyl chloride stream is reacted with hypochlorous acid, formed in turn by chlorine dispersion in water. The chlorohydrination reaction is conducted in the liquid phase, adiabatically. The liquid product from this reaction is passed through a separator system, which separates the aqueous phase from the hydrocarbon phase. The aqueous phase, containing hypochlorous acid, is recycled, and the hydrocarbon phase, containing glycerol dichlorohydrins, is reacted with calcium hydroxide to yield epichlorohydrin product. The crude ECH stream is passed through one stripper and two distillation columns for the removal of calcium chloride, light-end impurities and heavy-end impurities.
Epichlorohydrin is commonly produced from allyl chloride, derived from propylene. Production routes based on allyl alcohol and on the glycerol byproduct from biodiesel production have also been used. Different pathways for ECH production are presented in Figure 2.
The total operating cost (raw materials, utilities, fixed costs and depreciation costs) estimated to produce epichlorohydrin was about $1,850 per ton of epichlorohydrin in the second quarter of 2015. The analysis was based on a plant constructed in the U.S. with capacity to produce 80,000 metric ton per year of ECH.
Edited by Scott Jenkins
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