The invention relates to a method for controlling the CO / H2
molar ratio in a
coal to
methanol purification device. The method is characterized by comprising the following steps: (1) feeding rough synthesis gas from a gasification unit into a gas-liquid separator, performing gas-liquid separation, and dividing the separated
gas phase into two paths, namely a first path of synthesis gas and a second path of synthesis gas, wherein the
flow ratio of the first path of synthesis gas to the second path of synthesis gas is 1:(0.58-0.85); (2) performing heat exchange on the first path of synthesis gas, and performing CO conversion in a CO conversion unit to obtain converted gas; (3) performing heat exchange on the converted gas until the temperature of the converted gas is less than or equal to 50 DEG C, separating out a
liquid phase, performing low-temperature
rectisol in a first absorption
tower to obtain a first path of purified gas, performing heat exchange on the second path of synthesis gas until the temperature of the second path of synthesis gas is less than or equal to 50 DEG C, separating out a
liquid phase, and performing low-temperature
rectisol in a second absorption
tower to obtain a second path of purified gas; and (4) merging the first path of purified gas and the second path of purified gas to obtain
methanol synthesis gas. By utilizing the method, a perfect CO / H2
mole ratio can be obtained, the
energy consumption of the device is low, and the purpose of reinforcing the
operability of the device can be achieved.