A low-temperature methanol washing energy-saving device and process

Abstract

The invention discloses a low-temperature methanol washing energy-saving device and process; the device includes a medium-pressure flash tower connected to a reabsorption tower, and a semi-lean liquid stripping tower, which includes an upper tower, a middle tower and a lower tower, the middle tower The pressure flash tower is also connected to the upper tower of the semi-lean liquid stripping tower; the top of the upper tower is connected to the first heat exchanger, the bottom is connected to the middle tower, the top of the middle tower is connected to the second heat exchanger, and the bottom of the middle tower passes through the third The heat exchanger is connected to the lower tower, and the bottom of the lower tower is connected to the carbon dioxide absorption tower. In the present invention, flash evaporation is carried out by adding a semi-lean liquid stripping tower, and the flash evaporated carbon dioxide and tail gas are used as the cold source of the previous process, and exchange heat with lean methanol and shift gas to provide cooling capacity for the system. Adopting this process reduces the cooling capacity of the low-temperature methanol washing device system, saves the consumption of regenerative energy, and ensures the operating load of the device; the equipment structure is simple, the process flow is reasonable, and it has good economic and social benefits.

Description

technical field [0001] The invention belongs to the technical field of chemical industry and relates to low-temperature methanol washing, in particular to an energy-saving device and process for low-temperature methanol washing. Background technique [0002] In 2013, the low-temperature methanol washing unit underwent a 4-month renovation to meet the needs of our factory’s transition to produce 200,000 tons / year of ethylene glycol. After the renovation, the unit was put into production and operation in October 2013. After nearly two years of In terms of operating conditions, the low-temperature methanol washing unit has basically reached the pre-retrofit vision, and can deliver qualified process gas to the ethylene glycol and synthetic ammonia units at the same time. However, the device itself has also exposed some defects: reabsorbing the tail gas emitted by the tower, CO 2 The outlet temperature of the unconverted purified gas is far from the design value, and the cooling...

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Problems solved by technology

However, the device itself has also exposed some defects: reabsorbing the tail gas emitted by the tower, CO 2 The outlet temperature of the unconverted purified gas is far from the design value, and the loss of cooling capacity is serious, resulting in uneven distribution of cooling capacity for low-temperature methanol washing, and it is difficult to increase the system load

[0003] The CO emitted by low-temperature methanol washing 2 , exhaust gas and unconverted purified gas took away a lot of cooling capacity of the system, resulting in a very serious loss of system cooling capacity. In order to maintain the stable operation of the low-temperature methanol washing device, the load of the ice machine was forced to increase to meet the production demand, but in summer high temperature Under the environment, due to the continuous rise of circulating water temperature, the cooling effect of the ice machine is reduced, and the steam consumption is increased. Sometimes the full load operation of the ice machine cannot meet the production needs of the low-temperature methanol washing device, and the coal gasification device is forced to reduce the load. In 2015 In the past, the load of the coal gasification device could basically only be maintained below 80%, which virtually increased the production and operation costs of the enterprise

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