Effects of Indigenous and Added Minerals on Transformation of Organic and Inorganic Sulfur in Density Separated Coal Fractions during CO₂-Pyrolysis^†

Abstract

The present paper was addressed toward the impacts of indigenous and added minerals on the organic and inorganic sulfur transformations during CO 2 -pyrolysis in a fixed-bed reactor at a temperature range of 400-800 °C. A Chinese bituminous coal was separated into three density fractions using the float-sink method: light (<1.4 g/cm 3 ), medium (1.4-2.0 g/cm 3 ), and heavy (>2.0 g/cm 3 ). The sulfur retention of the three coal fractions was characterized in detail to study the influence of indigenous minerals on organic and inorganic sulfur transformation. Moreover, the role of added minerals was investigated by adding NaCl and kaolinite. The results indicated that indigenous minerals promoted the sulfur retention in coal char, especially in C >2.0 , but had little effect on the decomposition of inorganic sulfur. Meanwhile, it was found that the added minerals also increased the sulfur retention. NaCl had a remarkable effect on sulfur retention at a low temperature range but appeared to have little capacity of sulfur retention due to the volatilization of itself at high temperatures above 700 °C. As for kaolinite, it was observed that there was an indistinct ability to retain sulfur during CO 2 -pyrolysis in our study. In comparison with added minerals, indigenous minerals had more significant effects on sulfur transformation because they were inherently embedded in the organic matrix of coal, while added minerals were physically dispersed within coal.

Effects of Temperature and Potassium Compounds on the Transformation Behavior of Sulfur during Pyrolysis of Oily Sludge

“…It can be directly observed from Figure that the main sulfur compounds remaining in solid residues were thiophene, and sulfate while ZH contained much more sulfate sulfur than ZS sample attributing to high inorganic sulfur content in the raw ZH sludge sample. For ZH sample, as the final temperature rose from 350 to 550 °C, the content of sulfate decreased continuously and that of thiophenic sulfur increased correspondingly, which was in agreement with previous studies that gaseous sulfur evolving from the degradation of inorganic sulfur may secondarily convert into organic sulfur during pyrolysis. ,− As mentioned in Figure , Fe 2 (SO 4 ) 3 , FeSO 4 , and CaSO 4 were the main sulfates in the ZH raw sludge sample, and iron sulfates had been reported to decompose at 450 °C during pyrolysis . Therefore, the reduction of sulfate in the solid residues was due to the thermal degradation of sulfate, and the possible reactions could be described as follows: where Me is the inherent metal in oily sludge.…”

Acidic Peroxidation of Brazilian Coal: Desulfurization and Estimation of the Forms of Sulfur

“…Sulfur is one of the most significant indicators of quality in coal, particularly with regard to the environmental impact caused by coal processing as well as the residue/waste generated while using this fuel. Sulfur is a major source of pollution in coal exploitation, along with other environmental impacts, and inhibits effective and extensive clean coal utilization. − It is assumed that burning coal containing more than 1.0–1.5% of S demands the desulfurization of the fuel or flue gases. Despite the fact that most coal-fired power plants in developed countries have SO x control procedures to meet air pollution regulations, significant amounts of solid residues are generated during these processes (usually CaSO 4 ).…”

Effects of chromium ion on sulfur removal during pyrolysis and hydropyrolysis of coal

“…NaCl/KCl and KOH/NaOH were proved to have apparent sulfur fixing effects at low temperature range, but have little capacity of sulfur retention at high temperature due to the volatilization of Na and K during pyrolysis above 700 • C [12,13]. The extent of desulfurization and formation of H 2 S was reduced by alkaline inorganic additives [14].…”