Microwave Pyrolysis Sewage Sludge Hydrogen Sulfide Release Impact Factor And Treatment Research

Urban wastewater treatment plants are built in urbanization and sewage sludgeis produced in urban wastewater treatment. Water treatment techniques areadvancing day after day with the development of science and technology, but sludgereduction, safety disposal and recycling are becoming new bottleneck and attentionhotspot. Microwave pyrolysis of sewage sludge have obvious reduction effect,pyrolysis products can be recycling. It has the properties of faster pyrolysis rate,effective heavy mental fixation and slight smoke pollution, which becomes aresearch hotspot of scholars at home and abroad. By taking GC technique tomeasure gas concentration, using drainage to test the total volume of pyrolysisbiogas and pyrolysis mass using chemical titration, the influences of sludgecharacteristics （sludge varieties, water contents） and microwave pyrolysisconditions （pyrolysis temperature, heating rate and adding mineral catalysts） insewage sludge microwave pyrolysis process to H₂S gas productivities were studied.At last, recyclable copper-iron adsorption method and sludge activated carbonadsorbents were used to control H₂S gas through by taking full advantage of theadsorption abilities of pyrolysis mass.GC-MS analysis showed that sewage sludge microwave pyrolysis producedsulfocompounds gas including hydrogen sulfide, carbonyl sulfide, carbon disulfide.Sludge characteristics and microwave pyrolysis conditions affected the H₂S gasproductivities in microwave pyrolysis process. The sewage sludge from differentwastewater treatment processes and digest treatment had different series and content,H₂S productivity of microwave pyrolysis was different. In the range of50%—80%,H₂S productivity increased with the promotion of sludge water content, but H₂Sproductivity was not detected when water content was90%. Pyrolysis temperaturehad the most important effect on gas volume. The higher pyrolysis temperature, thehigher volumes of pyrolysis biogas and H₂S gas.1gram dry sludge produced976.7mL biogas and5.86mg gas. Reducing gas （H₂and CO） helped the release of H₂Sgas. When heating rate was increased, H₂S volume decreased.1gram dry sludgeproduced5.25mg H₂S using the heating rate of constant temperature, gasproductivity was5.21mg/g with the rate of300℃/min. Mineral catalyst had sulfurfixation function, especially nickel catalyst. H₂S productivity could reach4.15mg/gby adding nickel catalyst in the pyrolysis temperature of800℃, which decreasedabout30%compared with not adding catalyst. Besides, H₂S productivity only was5.72mg/g with dolomite, which decreased about2.4%.Microwave pyrolysis sewage sludge process produces stench gases including H₂S, which leads to serious air pollution like producing acid rain, corrodingbuildings, polluting soil, damaging human health. If the gas is applied to SolidOxide Fuel Cell （SOFC）, the longevity of the cell will be affected, so H₂S must becontrolled. Copper-iron adsorption solution had high efficiency of H₂S adsorption,simple substance S could be recyclable, as well as adsorption solution after airoxidation. Pyrolysis mass of sewage sludge without catalyst had high specificsurface area of596m2/g and high pore volume of0.256cm3/g.Adsorption-desorption curve of liquid nitrogen showed that micropore was the mainpore in pyrolysis mass and average aperture was close to H₂S molecular diameter.Scanning electron microscope showed that there were large number of micropores inpyrolysis mass, which could adsorb H₂S efficiently. Combined copper-ironadsorption solution and sludge activated carbon adsorption process, H₂S gas wasremoved safely. The stench gas of pyrolysis biogas was inferior to the plantemission limits of Emission standards for odor pollutants （GB14554-93）, thebiogas could be used safely.