Experimental Study On Carbothermal Reaction Between CuO And Ash Components

The greenhouse effect caused by the large-scale use of fossil fuels has received increasing attention.Coal/biomass chemical-looping gasification（CLG）is a clean and efficient syngas production technology,which can effectively slow down the increase of CO₂ in the atmosphere.CLG transfers lattice oxygen to the fuel by using the oxygen carrier,however,the existing technology has not been able to effectively separate the oxygen carriers from the ash.The interaction between the oxygen carrier and ash will cause the deactivation and sintering of the oxygen carrier.In this paper,the effects of minerals in coal/biomass ash on Cu-based oxygen carriers were systematically studied,which has a certain guiding significance for the practical application of CLG.Firstly,the effects of different substances on Cu-based oxygen carriers were systematically and comprehensively studied through carbothermal reactions between oxides,minerals commonly found in ash and Cu-based oxygen carriers at different temperatures.The results show that both Ca O and calcite can easily react with CuO to form Ca CuO₂ and Ca₂CuO₃.In any case,neither Si O₂ nor quartz reacted directly with CuO.Both Al₂O₃ and kaolinite can react with CuO to form Cu Al₂O₄ or Cu Al O₂.Fe₂O₃ and pyrite have a greater effect on CuO.In addition to the formation of Cu-Fe compounds,S produced by the decomposition of pyrite is easily combined with CuO/Cu₂O to form copper-containing compounds such as Cu Fe S₂ and Cu₂S.Secondly,different types of coal ash and biomass ash were selected on the basis of a single material,and the ratio of temperature to bamboo charcoal was changed to explore the influence of different ash components on the carbothermal reaction process of Cu-based oxygen carriers.The results showed that under the condition of no carbon,a large number of silicate compounds were generated at high temperature in GY ash and DC ash with high silicon content,which had a great negative effect on the Cu-based oxygen carrier.The high calcium content of SM ash reacts with CuO to produce a large proportion of Ca-Cu compounds which also inactivate part of the Cu-based oxygen carrier.LJ ash with more uniform composition had the least influence among the four kinds of ash.A small amount of carbon can promote the reaction between ash and Cu-based oxygen carrier.Excessive carbon has a barrier effect on the solid-solid reaction between CuO and ash,thereby reducing the deactivation of oxygen carrier.Finally,CLG process was simulated by reciprocating the redox atmosphere of the fixed bed reactor,and the reaction between the CuO and the minerals in the ash was experimentally studied from three aspects:temperature,ash type and ash ratio.The results showed that Ca O could alleviate the sintering by inhibiting the formation of Cu-Al compounds and CuO-Si O₂melt.CuO can be easily dissolved into Ca Si O₃,Mg Si O₃ and other silicates to generate Ca Cu Si₂O₆ and Cu Mg Si₂O₆.With the increase of ash content,Ca₂Fe₉O₁₃ generated by the enrichment of Ca²⁺and Fe³⁺plasma is easy to react with Si O₂ to form three-phase eutectic Ca Fe Si₂O₆,which can hinder the oxygen release process of CuO.