Method for controlling pH value of process water circulation system for ethylene production by steam cracking

Abstract

The invention discloses a method for controlling the pH value of a process water circulation system ethylene production by steam cracking. The method is characterized in that a water solution having a pH value of 4.7 and containing ring-B ring-C cation polyether with concentration of 10wt% is taken as an anti-phase demulsifying agent, a pentanediol solution having a pH value of more than 6.9 and containing diethylene triamine penta methylene phosphonic acid with concentration of 10wt%-30wt% is taken as a corrosion inhibitor, an alcohol ether solution having a pH value of less than 5.1 and containing naphthalene with concentration of 10wt% is taken as dispersing agent, a water solution having a pH value of more than 13 and containing N.N-diethyl ethylene diamine with concentration of more than 60wt% is taken as a neutralizer, and a water solution having a pH value of more than 13 and containing sodium hydroxide with concentration of more than 10wt% is taken as an alkaline corrosion inhibitor; and the solutions are sequentially injected according to a given injection sequence as well as given injection points and injection amounts, and then are adjusted according to monitoring projects and analysis indexes. According to the method, the pH value of the process water system is stably controlled, the water quality is obviously improved, and the qualified rate is above 98%. During the running of the processing water circulation system for 3 years, the system is not subjected to a process water emulsion phenomenon, and heat exchangers and other equipment as well as pipes are not subjected to leakage.

Description

technical field [0001] The present invention relates to a method for controlling quenching water for producing ethylene by steam cracking and a method for controlling process water produced by a dilution steam generating system, and specifically describes a method for controlling the acidity and alkalinity of the process water circulation system for producing ethylene by steam cracking. Background technique [0002] In the steam cracking ethylene production process, the heat of quenching oil at the bottom of the oil washing tower of the quenching unit is recovered to vaporize the process water to generate steam, which is recycled as the dilution steam of the raw material of the cracking unit. It is very important to control the acidity and alkalinity (i.e. pH value) of quenching water and process water during operation. If the acidity is too high (i.e. low pH value), acid corrosion will occur in the system, and long-term operation will cause leakage of equipment and pipelines...

AI Technical Summary

Problems solved by technology

Since the key component in the lye is sodium hydroxide, which is a strong alkali, it is difficult to stabilize the pH value of the system during actual adjustment, and it is easy to cause large fluctuations in the pH value, and emulsification of quenched water often occurs, resulting in long-term operation. The dilution steam generator (process water part) is severely corroded, and the heat exchanger leaks

Therefore, the device must regularly overhaul the heat exchanger, and the heat exchanger that has been overhauled many times must be replaced, which not only affects the normal and stable production of the device, but also increases the maintenance cost of the device, consuming a lot of manpower, material and financial resources

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