Process improvement for producing epichlorohydrin by using glycerin method dichloropropanol as raw material

The invention aim at providing a method for producing epichlorohydrin by using glycerin method dichloropropanol as a raw material with step-by-step saponification. Compared with the prior art, the process has the characteristics of mild reaction conditions, simple process, low alkali consumption, low brine TOC, high ECH yield, and the like. Different reaction speeds of each component in DCH are used, the step-by-step saponification method is used, firstly primary normal pressure intermittent or continuous saponification is used, oil and water are layered, an oil layer is rectified in order to obtain an ECH product, and negative pressure secondary saponification is carried out for unreacted DCH in a column reactor. A washing process is used, most monochloropropanediol in a primary saponification rectifying still residue is separated, monochloropropanedio and DCH in a washing water layer return to a glycerin chlorination system for reusage. After washing, negative pressure high alkali ratio is used for the primary saponification rectifying still residue in order to carry out secondary saponification, and continuous industrial production is realized.