Continuous recycling method of NMP (N-methyl pyrrolidone) solvent for polyphenylene sulfide production device

Abstract

The invention discloses a novel continuous recycling method of an NMP (N-methyl pyrrolidone) solvent for a polyphenylene sulfide production device. The polyphenylene sulfide production device comprises three vacuum rectifying towers, a heat exchanger, a centrifuge machine, a storage tank, a pump and relevant pipelines. In an existing polyphenylene sulfide solvent recycling process, pipelines are easily blocked by salt crystals in a dehydration process, so that the halt maintenance needs to be frequently carried out, the rate of equipment utilization is low, and the solvent loss is high. According to the novel continuous recycling method of the NMP (N-methyl pyrrolidone) solvent for the polyphenylene sulfide production device, a novel technological process device is developed; by virtue of forced circulation of high-concentration salt fraction at the tower bottoms, solid salt formed after water and the solvent are removed can be adequately stirred and circulated, and the blockage, caused by the salt crystals, of valves of the pipelines is avoided, so that the heating efficiency of the column bottoms is increased, the yield of NMP is improved, the quality of an recycled NMP product can reach 99.5% or above, recycling requirements of a system are met, and meanwhile, the long-period, stable and efficient operation of the device are guaranteed.

Description

technical field [0001] The invention belongs to the field of recovery of chemical engineering materials, and in particular relates to a new method for continuous recovery of N-methylpyrrolidone (NMP) solvent in a polyphenylene sulfide production device. Background technique [0002] Polyphenylene sulfide (PPS for short) is a high-performance special engineering plastic. Widely used in aerospace, military, electronics, electrical appliances, precision instruments, automobiles, machinery, home appliances, coatings and other fields. Since 1978, many domestic scientific research institutes have launched research and development on PPS. However, due to the slow progress in key technologies such as polymerization process, solvent recovery, and engineering scale-up, the production cost of PPS resin remains high, resulting in relatively low domestic market development. Lag, it is difficult to form industrial production capacity. Through the unremitting efforts of scientific and te...

AI Technical Summary

Problems solved by technology

However, in the actual application process, its shortcomings are also more significant: when the mixed solution is dehydrated by intermittent vacuum distillation, since NaCl is not dissolved in the NMP solvent, during the dehydration process, a large amount of NaCl will Crystallization precipitates, and it is easy to block the tower kettle and pipeline when the crystallized salt is generated

Therefore, it is necessary to stop the operation regularly to clean the NaCl solid crystallized on the surface of the tower kettle. The cleaning process takes away a certain amount of NMP solvent, which not only increases the time for equipment maintenance, but also increases the loss of NMP solvent. At the same time, due to the excessive organic content in the discharged brine Many, so that the utilization of waste brine has been greatly restricted

Images