Minimizing minerals-induced oil cracking through internals-regulated pyrolysis

The oil-cracking caused by minerals during the pyrolysis of ash-rich feedstocks was identified as one of the primary factors contributing to low tar yield. A novel internals-regulated pyrolysis showed the potential in mitigating mineral-induced oil-cracking through regulating the formed volatiles flowing from high temperature to low temperature. To validate the internals-regulated effectiveness, pyrolysis experiments were conducted on low-ash Shenmu coal samples with and without CaO (a representative inherent mineral) using reactors with and without internals. The decrease in tar yield by blending CaO during internals-regulated pyrolysis was far less than that during traditional pyrolysis at each tested temperature. Furthermore, as the temperature increased from 600 °C to 1000 °C, the decrease in the tar yield based on G-K yield due to CaO blending was almost unchanged for internals-regulated pyrolysis, whereas it surged from 5.65 % to 19.40 % for traditional pyrolysis. These findings indicated that oil-cracking caused by CaO was effectively inhibited through internals-regulated pyrolysis. For internals-regulated pyrolysis, volatiles flowed from high-to-low temperature regions, making tar-CaO reactions occurring at lower temperatures. As a result, the promotional effect of CaO on tar-cracking was weaker than that for traditional pyrolysis. This study achieved the minimization of oil loss caused by minerals through internals-regulated pyrolysis and provided novel insights into oil/chemicals production using high-ash feedstocks.