基于灰热载体的煤热解过程中,煤灰对煤热解特性的影响与其所含的CaSO4密切相关,但由于CaSO4与还原气和半焦之间存在复杂的竞争反应,导致CaSO4对热解的影响规律和作用机制尚不明确。在固定床反应器中考察了500℃~850℃条件下CaSO4对煤热解特性的影响规律,同时开展了CaSO4-模拟热解气的气-固反应实验和CaSO4-半焦的固-固反应实验,用于探究CaSO4与还原气和半焦之间的竞争反应。结果表明:添加CaSO4在低温时对H2收率无显著影响,但850℃时添加CaSO4导致H2收率由1.11%降到0.96%,模拟热解气与CaSO4的气-固反应验证了2H2+CaSO4→CaS+2H2O是H2收率降低的主要原因。高于700℃时,添加CaSO4导致CO和CO2的收率显著增加,如850℃时CO和CO2收率分别由原煤热解时的11.57%和15.2%增加到添加CaSO4热解时的31.60%和20.3%,CaSO4与半焦的固-固反应证实了2C+CaSO4→CaS+2CO2和4C+CaSO4→CaS+4CO是CO和CO2收率增加的主要原因。结合热解过程中CaSO4的分解率及质量衡算,固-固反应导致的CaSO4的分解量约占总分解量的91.95%,表明相较于CaSO4与还原气的气-固反应,热解过程中CaSO4的分解主要归因于CaSO4与半焦的固-固反应,这是CO和CO2的变化量远高于H2变化量的本质原因。

The impacts of coal ash are closely linked with CaSO during coal pyrolysis with ash as heat carriers. However, due to the existence of complicated competing reactions a- mong CaSO -pyrolytic gas and CaSO -char, the influence of CaSO on the characteristics of coal pyrolysis remains elusive. The impacts of CaSO in a fixed-bed reactor at temperatures of ℃ ℃ were investigated, and the experiments on gas-solid reactions and solid-solid reactions were also performed to clarify the competing reactions. The results show that H yield is less effected by CaSO at low temperatures, however, a decrease from 1.11% to 0.96% at ℃ is observed when CaSO is added. The gas-solid reactions between simulated pyrolytic gas and CaSO show that the reaction 2H +CaSO →CaS+2H O is mainly responsible for the varie- ties in H . CaSO is found to promote CO and CO yields at temperatures above ℃. For ex- ample, CO and CO yields are significantly increased from 11.57% and 15.2% to 31.60% and 20.3%, respectively, at ℃ with CaSO addition, which is ascribed to the reactions 2C+ CaSO →CaS+2CO and 4C+CaSO →CaS+4CO according to investigations on the solid- solid reactions between char and CaSO . Based on the analysis of mass balance and decomposition ratios, the decomposition amount of CaSO due to solid-solid reactions accounts about 91.95% of the overall decomposition amount. This indicates that compared to gas-solid reactions, the solid- solid reactions play a predominant role in how CaSO influences coal pyrolysis, elucidating the substantial increase in CO and CO compared to that of H .