Using a natural gas engine emitted to CN Ⅵ emission standard

the engine’s emission data under normal operating conditions were collected by a full-flow dilution system

and the influence of excess air ratio

catalyst temperature

and CO and NOx emission concentrations on NH3 emissions was analyzed. And on this basis

several methods for controlling NH3 emission were proposed. Results show that when the excess air ratio is greater than 0.965

NH3 emission will gradually decrease

while CO emission has a greater impact on NH3 emission

causing NH3 emission to show a positive growth with increased CO concentration within a certain range. However

there is no obvious relationship between NH3 emission and NOx emission. Moreover

when the three-way catalytic(TWC) converter system is wrapped with thermal insulation material

NH3 emission decreases with the increase of catalyst temperature. In view of this

among the 3 kinds of technologies for controlling NH3 emission from natural gas engines

it is currently recommended to use two-stage TWC technology to control the NH3 emissions of natural gas engines. When an applicable ammonia slip catalyst(ASC) can be successfully developed to eliminate NH3 escaped from TWC aftertreatment system

the use of TWC plus ASC will be a preferred solution for the emission control of natural gas engines in the future.