Natural gas molecular sieve adsorption dehydration system provided with heat recycling structure, and method

Abstract

The invention discloses a natural gas molecular sieve adsorption dehydration system provided with a heat recycling structure, and a method. The natural gas molecular sieve adsorption dehydration system comprises an adsorption tower assembly composed of a plurality of adsorption towers, a filter, a heater, a heat recycling heat exchanger, an air cooler, a gas-liquid separator, and a compressor; inthe adsorption tower assembly, at least on adsorption tower is taken as a dehydration tower, at least one adsorption tower is taken as a cooling regeneration tower, at least one adsorption tower is taken as a thermal regeneration tower, and at least one adsorption tower is taken as a standby tower; dehydration, cooling regeneration, and thermal regeneration process is realized through cooperationof a switch valve and the adsorption towers, no exhaust gas is discharged, natural gas waste or adoption of other processing equipment is avoided, device operation flexibility and operation reliability are increased, large scale continuous dehydration operation is realized, and the natural gas molecular sieve adsorption dehydration system can be widely used in natural gas dehydration.

Description

technical field [0001] The invention relates to the technical field of natural gas liquefaction, in particular to a natural gas molecular sieve adsorption and dehydration system and method with heat recovery and utilization structure. Background technique [0002] The natural gas liquefaction process is a series of processes in which the raw natural gas from the long-distance pipeline network is pressurized and purified, and then liquefied in a cold box. Before liquefaction, the raw natural gas must be purified and pretreated to remove impurities such as carbon dioxide, hydrogen sulfide, water, mercury, and heavy hydrocarbons contained in the raw natural gas. These substances will freeze at the low temperature used in the liquefaction process and block equipment or reduce the performance of the heat exchanger, usually use triethylene glycol to absorb dehydration to reduce the dew point of natural gas water to 5°C below the ambient temperature, but the depth of triethylene gl...

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Problems solved by technology

[0003] At present, the commonly used molecular sieve dehydration processes are mainly 1+1 scheme (1 tower for adsorption and 1 tower for regeneration) and 2+1 scheme (2 towers for adsorption and 1 tower for regeneration). Non-stop production of natural gas processing units to replace molecular sieves

Since the regeneration of molecular sieve requires high temperature to be fully regenerated, and the molecular sieve regenerated at high temperature needs to be cooled before it can be put into the next round of adsorption operation, the heat generated by cooling the molecular sieve is wasted because it is not recycled.

In addition, the molecular sieve adsorbent has a certain service life. After the service life expires, the molecular sieve will be pulverized and the adsorption capacity will decrease. Therefore, the molecular sieve adsorbent needs to be replaced once every few years. It can only be directly transported to the downstream. If the downstream is an LNG liquefaction system, the water-saturated natural gas will freeze the cold box and damage related equipment, making the device unable to operate normally.

[0004] The Chinese patent "CN108822909A" has a natural gas dehydration system for the preheating utilization of molecular sieve regeneration gas. Although the preheating recovery of molecular sieve regeneration gas is realized, a cold regeneration heat exchange mechanism and a hot regeneration heat exchange mechanism are added to the system at the same time, and usually When there is a molecular sieve that needs to be replaced, the entire process will be stopped, resulting in waste and loss of resources

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