TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The molecular sieve of the sulfuric acid refining furnace air filter is 200 meshes. The composition of adsorbent from bottom to top in the carbon molecular sieve adsorption tank as follows: the bottom layer contains 30-40% of crude porous silica gel, the second layer contains 20-30% of fine porous silica gel, the third layer contains 10-20% of sodium bentonite, the fourth layer contains 5-10% of X-type molecule sieve and the upper layer contains 15-20% of carbon molecular sieve. The adsorbent contains biogas residue activated carbon and multiple composite additive, where the amount of each component as follows: 65-80% biogas residue activated carbon, 4-7% biogas digested sludge carbonized material, 10-15% silica sol, 4-8% liquid paraffin and ammonium bicarbonate mixture of ratio 1:5, and 2-5% sodium bentonite. Preferred Method: The frequency conversion compressor discharge pressure is 0.13-0.55 MPa and the discharge temperature is 35-41 degrees C. Preparation of the biogas residue activated carbon as follows: cleaning biogas residue in biogas tank after fermentation, filtering, removing impurities, extruding and dehydrating in a spiral extruding machine or three-roller extruding machine, controlling moisture content to 8-10%, where the mass ratio is 10-20%, soaking in zinc chloride solution at 30-40 degrees C for 35-40 hours, extruding and dehydrating in the spiral extruding machine or three-roller extruding machine, drying to moisture content of 5-10%, placing the biogas residue in ceramic or silicon carbide crucible, microwave irradiating and carbonizing under irradiation power of 2000-3000 W for 20-30 minutes, naturally cooling, rinsing using 30-40 degrees C deionized water, baking for 25 hours, and crushing into fine powder of 200-400 meshes sieve. Preparation of the biogas digested sludge carbonized material as follows: filtering and precipitating sludge in the biogas fermentation tank, draining, adding 10-20% mass concentration of zinc chloride solution, soaking at 30-40 degrees C for 20 hours, drying for 24 hours, placing in ceramic or silicon carbide crucible, microwave irradiating and carbonizing under irradiation power of 2000-3000 W for 10-20 minutes, rinsing using 30-40 degrees C deionized water, baking for 25 hours, and crushing into fine powder of 200-400 meshes sieve.