Brief introduction of non-circulating methanation process:
The gas produced by coal gasification is divided into two parts, one part (about one-third of the total gas volume) is transformed into synthesis gas with lower CO content (that is, rich in hydrogen), and the other part (about three-thirds of the total gas volume) 2/2) without conversion (CO-rich gas). The two-part syngas undergoes methanation after sulfur decarbonization through low temperature methanol elution.
The methanation uses a fixed-bed adiabatic reactor. The shifted syngas with lower CO content (hydrogen-rich) is preheated and then enters the primary reactor, and the outlet temperature is 650-750 °C (thermodynamic equilibrium temperature); (CO-rich gas) is mixed and enters the secondary reactor, the temperature of the secondary outlet is 650-750 °C; after the outlet gas of the secondary reactor is cooled, it is mixed with the remaining untransformed synthesis gas (CO-rich gas) and enters the tertiary reaction device.
The first three stages are high temperature methanation reactors, and the latter stages are medium and low temperature reactors. Similar to the DAVY process or TOPSOE process currently used in industry, the methane content of the last stage outlet gas can reach 95-98% after cooling and dehydration.
The process adopts mature and advanced industrial technologies, such as: sulfur-resistant shift, low-temperature methanol washing, high-temperature adiabatic methanation, etc., and there is no principle technical obstacle to industrial application.
The main advantages of this process flow are:
(1) No recycling equipment, saving investment;
(2) Compared with the circulating process, the high temperature reactor is less likely to fly over temperature, and the operation is more stable and safe;
(3) Operational energy consumption is reduced (compared with the circulation process, it is reduced by about a quarter).