Method for synthesizing ammonia by taking byproduct tail gas in process of producing acetylene by pyrolyzing natural gas as raw material

The invention discloses a method for synthesizing ammonia by taking byproduct tail gas in a process of producing acetylene by pyrolyzing natural gas as a raw material. The method comprises the following steps: step S1, carrying out a tail gas purification procedure, wherein the content of hydrogen in purification raw material gas is 99.0 percent or more; step S2, carrying out a methanation procedure and forming ammonia synthetic gas by the purified raw material gas in the step S1 and nitrogen gas; enabling the sum of the content of carbon monoxide and carbon dioxide in qualified synthetic gas to be smaller than 10ppm; step S3, carrying out an ammonia synthesis procedure: conveying the qualified synthetic gas in the step S2 into the ammonia synthesis procedure, so as to prepare the ammonia. According to the method disclosed by the invention, a purification method is adopted and pure hydrogen gas is directly extracted from byproduct tail gas; the pure hydrogen gas is used as raw material gas of the ammonia synt