TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: A raw material gas inlet (12) of the second raw material gas cooler is connected to the raw material gas outlet of the low-temperature methanol washing device using a fifth pipeline. A raw material gas outlet (14) of the second raw material gas cooler is connected to the raw material gas inlet of the third raw material gas cooler using a sixth pipeline. A raw material gas outlet of the third raw material gas cooler is connected to the raw material gas inlet at the sidewall of the separating pot using a seventh pipeline. A top of the separating pot is provided with the raw material gas outlet separating the methanol fraction. A bottom of the separating pot is provided with methanol fraction liquid outlet (21). The raw material gas outlet separating the methanol fraction is consented with the raw material gas inlet at the lower part of the nitrogen washing tower using a eighth pipeline. A methanol fraction liquid outlet is connected to the methanol fraction inlet at the lower part of the methanol rectifying column using a ninth pipeline. A top of the nitrogen washing tower is provided with the nitrogen washing gas outlet while the bottom is provided with the fraction liquid outlet. A top of the methanol rectifying column is provided with the gas outlet while the bottom is provided with the SNG liquid outlet. A nitrogen washing gas outlet (26) is connected to the inlet of the gas-liquid mixer using a tenth pipeline. An outlet of the gas-liquid mixer is connected to the nitrogen washing gas inlet of the third raw material gas cooler. The gas-liquid mixer is provided with a first nitrogen distribution port. The first nitrogen distribution port is connected to the fourth pipeline using a eleventh pipeline and a first throttle valve. A nitrogen washing gas outlet of the third raw material gas cooler is connected to the inlet of the gas-gas mixer. An outlet of the gas-gas mixer is connected to the nitrogen washing gas inlet of the second raw material gas cooler using a twelfth pipeline. The gas-gas mixer is provided with a second nitrogen distribution port. The second nitrogen distribution port is connected to the third pipeline using a thirteenth pipeline and a second throttle valve. The nitrogen washing gas outlet of the second raw material gas cooler is connected to the cold synthesis gas inlet in the low-temperature methanol washing device using a fourteenth pipeline and connected to the synthesis gas inlet of the first raw material gas cooler using a fifth pipeline. A synthesis gas outlet of the first raw material gas cooler is connected to the thermal synthesis gas inlet of the ammonia synthesis device using a sixteenth pipeline. A thermal synthesis gas outlet of the low-temperature methanol washing device is connected to the sixteenth pipeline. A fraction liquid outlet of the bottom of the nitrogen washing tower is connected to the fraction liquid inlet of the flash drum using a seventeenth pipeline. A gas outlet of the top of the methanol rectifying column is connected to the gas inlet of a flash drum using a eighteenth pipeline. A top of the flash drum is provided with the gas outlet. A bottom of the flash drum is provided with the liquid outlet. The gas outlet of the top of the flash drum is connected to the fuel gas inlet of the third raw material gas cooler using a nineteenth pipeline. A liquid outlet of the bottom of the flash drum is connected to the fuel gas inlet of the third raw material gas cooler using a twentieth pipeline. A fuel gas outlet of the third raw material gas cooler is connected to the fuel gas inlet of the second raw material gas cooler using a twenty first pipeline. A fuel gas outlet of the second raw material gas cooler is connected to the fuel gas inlet of the first raw material gas cooler using a twenty second pipeline. The fuel gas outlet of the first raw material gas cooler is connected to the fuel gas storing pot using a twenty third pipeline. The SNG liquid outlet at the bottom of the methanol rectifying column is connected to the SNG inlet of the third raw material gas cooler using a twenty fourth pipeline. A SNG outlet of the third raw material gas cooler is connected to the SNG inlet of the second raw material gas cooler using a twenty fifth pipeline. A SNG outlet of the second raw material gas cooler is connected to the SNG inlet of the first raw material gas cooler using a twenty sixth pipeline. A SNG outlet of the first raw material gas cooler is connected to the SNG outlet of the liquid nitrogen washing device and connected to the SNG storing pot using a twenty seventh pipeline. The bottom of the methanol rectifying column is provided with a reboiler. An inlet and an outlet of the reboiler are connected to the third pipeline or the sixth pipeline.