Marsh gas pretreatment and impurity filtering device

The invention discloses a marsh gas pretreatment and impurity filtering device. During using, marsh gas is introduced into a gas inlet cavity through a gas inlet pipe, gravel is put in a filtering box, and a telescopic air cylinder is started to drive a pushing block to extend towards the outer side, so that a connection rod drives a rotary supporting rod to extend towards the outer side, a rotaryplate is supported, and a rotary supporting plate blocks an opening of a waste discharging pipe to avoid falling of the gravel; marsh gas is subjected to impurity filtering through a filtering port in an installing plate and the gravel in the filtering box, after filtering is conducted for some time, the telescopic air cylinder is started so that the rotary supporting rod can retract and rotate,at the moment, the rotary plate can be bent and fall, and after filtering is conducted, smudgy gravel is discharged; driving motors are started to drive lifting slide blocks to ascend and descend, thefiltering box is driven to