Unique Advantages of Gasification-Coke Prepared with Low-Rank Coal Blends via Reasonable Granularity Control

Abstract

To perfectly solve the shortage of high-strength lump-feedstock resources and the problems of phenolic wastewater treatment and furnace corrosion restricting long-term operation of moving (fixed) bed gasification, high-strength gasification-coke with a large amount of low-rank coal blends has been prepared by reasonable granularity control at low cost. To further understand the physicochemical properties of this coke, the effects of the blending ratio of low-rank coals and particle size distribution on coke reactivity were investigated in this study. At the same time, the release ratio of Na in gasification-coke with blending sodium-rich coal was detected during the pyrolysis, gasification, and combustion stages. The results show that coke gasification reactivity with the fast reaction rate range mainly depends on the blending ratio of low-rank coals. The reasonable granularity control, which requires a small amount of strong-caking coal fines (<0.2 mm) bonded with coarse particles (1–3 mm ratio > 60%) of low-rank coals and weak-caking coals, gives rise to coke in a cage shape having a large pore structure with the process of gasification. The residues of coke also exhibit a relatively high mechanical strength. The unique feature of gasification-coke can inhibit about 45% Na volatilization more than that of the investigated sodium-rich coal because of the formation of a strong skeleton structure of the former that locks up the low-rank coal ash firmly during the gasification process. Most water-soluble Na (Na2SO4) retained in the low-rank coal ash further promotes the gasification reactivity of residues (caking coal components) in the later stage of gasification, and then it enters the ash with subsequent combustion at high temperature and transforms to aluminum silicate, which can reduce the furnace corrosion remarkably.

Distribution Characteristics of Coking Products and Mechanism of Tar Lightening in Preparation of High-Strength Gasification-Coke with Low-Rank Coal Blending

“…Long flame coal (SMC, low-rank coal), gas coal (GC, weak caking coal), and fat coal (FC, strong caking coal) were used in this study. − SMC was collected from Shaanxi province, and GC and FC were collected from Inner Mongolia in China. Detailed proximate and ultimate analysis, as well as the caking indexes ( G R.I. , a modified Roga index according to GB/T5447-2014) and mean maximum reflectance of vitrinite ( R o , max , according to GB/T 6948-2008) of these coals are given in Table .…”

“…Thus, the formation of value-added chemicals and coke has become the focus during the staged conversion of low-rank coal. To this end, high-strength gasification-coke with controllable granularity was successfully prepared and demonstrated as a very suitable feedstock for moving bed gasification in our previous research. − We developed a method to prepare this high-strength coke by blending low-rank coal with an equal amount of inferior caking coal . The formation of a cage-shaped coke structure with high strength and tunable sizes after partial gasification could reduce the pressure drop during the moving-bed gasification.…”

“…The formation of a cage-shaped coke structure with high strength and tunable sizes after partial gasification could reduce the pressure drop during the moving-bed gasification. Also, the resultant coke could be used in fluidized bed gasification to maintain a stable fluidization process . However, detailed evolution mechanisms of pyrolysis gas and tar are still unclear despite the resultant coke having met the strength requirement.…”

Three-Dimensional Physical Similarity Simulation Experiments for a Transparent Shaft Coal Pocket Wall in Coal Mines

“…19 − 22 There still exist some pending issues, which need to be investigated such as the stability of the shaft coal pocket wall, bulk flow properties, and the induced change of mechanical behaviors of the contact surface between the surrounding rock and the shaft wall. 23 − 27 Nedderman and Léonard et al studied about the bunker stress distribution. 28 , 29 Different coal particles have different properties due to their different components, so the impact is different.…”

In-Situ Catalytic Upgrading of Tar and Coke during Biomass/Coal Co-pyrolysis

“…In this regard, the production of high-mechanical strength ( M 25 > 80%) biomass coke is desired. In previous efforts to efficiently utilize coke powder after staged conversion of low-rank coal, high strength gasification-coke with controllable granularity was successfully prepared during the low-rank coal pyrolysis intensification. − Given the similarity between the biomass and low-rank coal, high strength biomass coke may also be prepared through a similar process. Moreover, based on the above-mentioned literature, controlled modification of solid-waste containing alkali, alkali earth, and/or transition metals may generate catalysts that are capable of improving tar quality significantly.…”