| In the process of solid waste incineration,heavy metals will directly escape in the form of gas or be enriched on fine particles,which are discharged into the atmosphere with flue gas and cause environmental pollution.Therefore,finding an effective method to remove heavy metals and the precursor of fine particulate matter as an enrichment carrier of heavy metals is of great significance to the pollution control of solid waste incineration flue gas.In this paper,boric acid and melamine were as raw materials,thiourea was as sulfur source.The traditional precursor method for preparation of boron nitride materials was improved.Sulphur-doped boron nitride（S-BN）as adsorbent materials were prepared by combining the precursor method and high temperature diffusion modification method.We used the self-built adsorption device experimental platform to explore the adsorption characteristics of S-BN for heavy metals in incineration flue gas and the adsorption performance of high-temperature heavy metal flue gas.And then we used high-temperature activated modified boron nitride material as an adsorbent to explore its adsorption performance for fine particle precursors.The research results in this paper shown that the S-BN prepared in the experiment is a fibrous structure with prismatic grooves on the surface,its particle size can reach nanometers,the internal pore volume is about 0.17 cm3/g～0.39 cm3/g,and the thickness of the adsorption layer is 0.36 nm～0.55 nm,pore size distribution is 0.85 nm～284.39 nm,average pore size is 2.95 nm～4.19 nm.It is a typical mesoporous solid.The content of S in the prepared S-BN ranged from 1.02 mg/g to 58.55 mg/g,and the content of S gradually increased with the increased of doping ratio.The maximum specific surface area of S-BN was 524.17 m2/g when the doping molar ratio of S was 0.75 and calcined at high temperature for 5 h.Through the adsorption experiment of mixed heavy metal flue gas,it had the best adsorption capacity at 150℃～200 ℃,and there was some difference in the adsorption of different heavy metals,and it had obvious selective adsorption for Pb.With the increased of adsorption temperature,the adsorption process was dominated by the transformation from physical adsorption to chemical adsorption.At the temperature of 800℃,S-BN still maintained good adsorption activity.The adsorption capacity of S-BN for heavy metals Pb and Zn was relatively stable,but the adsorption effect of S-BN for heavy metals Cr was not ideal.Through high-temperature activated modified BN and activated carbon to compare the adsorption performance of fine particle precursors in flue gas,it was found that both adsorbents had a certain adsorption capacity for fine particle precursors.But their adsorption capacity was far less than that for heavy metals.Activated carbon was deactivated at 100℃,resulting in a decrease in adsorption capacity,while high-temperature activated BN always maintained a good adsorption capacity,reaching a saturated adsorption capacity of 1.59 mg/g at 100℃.When the temperature was higher than 200℃,the adsorption capacity of activated BN decreased obviously,but the adsorption capacity fluctuated little.The adsorption temperature below 200℃ was mainly physical adsorption process,and the adsorption temperature above 200℃was mainly chemical adsorption process.The results of this experiment provide a new idea for the high temperature adsorption of incineration flue gas and the synergistic removal of fine particles and heavy metals in incineration flue gas. |
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