Steps to thoroughly clean the screen changer

The purpose of the screen changer cleaning is to make the polymer residue on the dirty candle filter as little as possible, so that the next TEG cleaning and alkaline cleaning can be carried out. The self-cleaning of the screen changer is divided into 3 major steps. Hydrolysis, pre-oxidation, oxidation.

Steps for cleaning the screen changer:

The first stage is the hydrolysis stage. Start the superheat heater E01, and open the steam valve EV2, use the high-temperature steam after heat treatment as a heat carrier to promote the cracking of the polymer on the surface of the filter element, break the molecular chain of the polymer, and turn it into a small molecule structure. The viscosity drops. In this process, steam also has a role as a transport carrier, taking the cracked gas produced by cracking and the polymer particles produced by cracking away from the filter element. At this time, the steam also acts as a transport medium. The main purpose of this stage is to reduce the viscosity of the high-viscosity melt, so that the melt wrapped on the filter element can become a small particle structure as much as possible, so that the subsequent pre-oxidation and oxidation stages can be carried out more fully.

The second stage-pre-oxidation stage. At this stage, the temperature of the superheating heater E01 continues to rise, and the steam valve EV2 remains open and steam continues to be added. In the first small step of this stage, one small air valve EV6 is opened; in the second small step, the two small air valves EV6 and EV5 are both opened, and the temperature continues to rise. The basic cracking reaction is completed in the hydrolysis stage. After a long time of reaction, the melt on the surface of the filter element forms a honeycomb structure with particle characteristics. It is difficult to clean them more thoroughly by continuing to use steam. In this case Down. Adding a small amount of air to the steam can cause a small amount of oxidation reaction on the surface of the particles. Due to the control of the oxidation reaction process, the amount of oxygen can only be increased by a small amount. To reduce the concentration of oxygen entering the reaction, one and two small 8 mm air valves were opened in the first and second stages, respectively.

The third stage-oxidation stage. The steam valve EV2 is closed, the two 8 mm small air valves EV6 and EV5 are also closed, and the 20 mm large air valve EV1 is opened. At this time, the relatively easy-to-react small melt particles have undergone a relatively complete oxidation reaction, and some of the larger particles have undergone a preliminary oxidation reaction on the surface. After the oxygen concentration is increased, the oxidation reaction will proceed more completely. . As we all know, the severity of the chemical reaction is closely related to the concentration of the reacting substance. The basic principle of self-cleaning is to make the melt wrapped on the filter element become as small as possible during the hydrolysis process. Afterwards, an oxidation reaction is carried out to make the melt particles burn in a small amount on the filter element, so as to achieve the purpose of cleaning.

The second stage-the pre-oxidation stage and the third stage-the oxidation stage is actually the main reaction is the oxidation reaction, but the oxidation reaction environment is different, the oxygen concentration is different.

Practice has proved that after adding the second stage, a pre-oxidation stage, the safety of the cleaning process becomes more reliable. There is one point to pay special attention to during the cleaning process: the oxidation stage is the stage where the melt particles are burned on the filter element in a small amount! In this stage, if there is a slight deviation in the control, the combustion of the melt particles on the filter element will be out of control and become Violent combustion, and the result of intense combustion is damage to the filter element.