At present, large-scale petrochemical plants, chemical fertilizer plants, and natural gas purification plants in my country must carry out desulfurization and sulfur production. N-methyldiethanolamine, referred to as MDEA, is a new desulfurization and decarburization solvent. It has been applied in industry in foreign countries in the 1970s. It has been applied on the Internet and has been widely promoted in China by the beginning of this century. MDEA is obtained by the reaction of monomethylamine and ethylene oxide.
2.1 Synthesis reaction
After the monomethylamine and ethylene oxide are measured separately, enter the mixer for mixing, and react under the conditions of 6.3 MPa and 135 ℃, and carry out the polymerization reaction. In the initial stage of the reaction, the heat required for the reaction enters the bottom of the reactor directly from the steam. During the reaction process, a large amount of heat generated by the material reaction will cause the reaction temperature to rise sharply. In order to maintain the reaction temperature, the temperature at the outlet of the reactor and the gas phase temperature in the reactor are used to control the circulating water volume of the cooler at the top of the reactor. .
2.2 Deamination
The reactants enter the deamination tower, and most of the unreacted monomethylamine comes out from the top of the tower, and is recycled after being cooled by the top condenser. The amine liquid at the bottom of the deamination tower is sent to the primary flash tower.
2.3 Flash
The reactant from the deamination tower flashes part of the monomethylamine in the primary flash tower, and then enters the secondary absorption tower after being cooled by the top condenser, and the liquid from the bottom of the primary flash tower enters The secondary flash tower flashes unreacted monomethylamine out.
2.4 Absorption
The gas from the top of the secondary flash distillation tower enters the lower part of the primary absorption tower, where a part of the light components in the primary distillation tower are used as the absorption liquid for absorption. The liquid from the primary absorption tower enters the secondary absorption tower as absorption liquid. After cooling, the gas phase from the top of the primary flash tower enters the lower part of the secondary absorption tower, and is absorbed by the absorption liquid from the bottom of the primary absorption tower. The gas from the top of the secondary absorption tower is treated and discharged.
2.5 Initial distillation
The reaction product comes out from the bottom of the secondary flash distillation tower, enters the middle part of the primary distillation tower, and the light component amine gas is evaporated from the top of the tower. The top reflux liquid of the distillation tower is sent to the primary absorption tower as the absorption liquid in the other way. The heat required for the initial distillation is supplied by heating the bottom reboiler of the initial distillation column with steam. The vacuum system of the initial distillation tower is evacuated by the vacuum pump unit of the initial distillation tower.
2.6 Distillation
The reaction product from the removal of light components comes out of the bottom of the initial distillation tower, and is pumped out by the feed pump of the rectification tower to the middle of the rectification tower. Through rectification, the gas from the top of the tower passes through the top of the rectification tower After the condenser is cooled by circulating water, it is divided into two routes, one route is sent to the top of the rectification tower as the reflux liquid of the rectification tower, and the other route is used as the main product of the device. The heat required for rectification is supplied by steam heating in the bottom reboiler of the rectification column. The heavy component from the bottom of the column is pumped to the raffinate receiving tank through the bottom tank of the rectification tower.
