Mechanism of Efficient Desulfurization Process by Catalytic Pyrolysis for High Sulfur Waste Residue
Based on the studies of catalytic pyrolysis for high-sulfur waste residue(HSWR),it is found that after 90 min pyrolysis at a temperature of 600℃,with Fe2 O3 as a sulfur fixation agent in a mass ratio of 1.5∶1 with HSWR,the total desulfurization rate can be around 85%.The volatile sulfur-containing complex organic matter in HSWR could be transformed into stable inorganic matter,among which the amorphous sulfur could be transformed into crystalline sulfur with purity over 95%.In the residue left after pyrolysis process for desulfurization,the main components include inorganic salts such as sodium sulfate and carbon black.The exhaust gas is mainly composed of simple molecular organics such as CH4 and C2 H4,and a small amount of inorganic compounds such as CO,SO2,CO2 and HCl.The pyrolysis process for desulfurization consists of four stages:firstly,the amorphous elemental sulfur is vaporized and then crystallized to form crystal sulfur;secondly,as for the elemental sulfur with attachment of organic matter and in a relatively more stable structure,its bond with the hydroxyl or carboxyl of organic phase is broken,leading to sulfur emitted into the atmosphere;at the third stage,the sulfur-containing organic phase is deactivated at the methylene and submethyl sites to form HCl,H2 S and carbon black,which are then adsorbed by sulfur-fixation agent and converted into sulfate;at the fourth stage,the carbon-carbon bond between nitrogen heterocyclic hydrocarbons becomes unstable after grouping,and is broken into small organic molecules such as CH4 and C2H4,as well as carbon black and a trace of H2. Meanwhile,C—N/C—NHx bonds are broken into NOx/NH3,and C—S/C—SO3 H bonds are broken into H2S and SO2,which are then adsorbed by sulfur fixation agents and converted into sulfate.
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