Understanding the slag transformation behaviors during entrained‐flow gasification based on comparative analysis of slag properties

Abstract

In this work, four slag samples were collected from the OMB CWS gasification, and the mineral behavior and morphology were studied to explore the formation mechanism of blockage slag. Results showed that amorphous phase is dominant in all slag samples, which was mainly glassy substances rich in low-temperature eutectic of iron. The precipitation of metallic iron and the crystals of SiC, calcite, and quartz were found in slags which were taken from the bottom of the combustion chamber (S-b). The quench slag collected from stable operation conditions (S-s) had a low content of quartz crystalline. While slag from the down pipe of the quench chamber (S-b) and bulk slag from the water-cooled pool (S-p) had observed the precipitation of crystals. Comparing to S-s, carbon matters in S-b had a higher order degree of carbon structure. By comparing the slag sample obtained during stable operation (S-s) with slag blocking occurs (S-b, S-d, S-p), it is found that the blockage of the OMB CWS gasifier was strongly related to unreacted residual carbon and the high content of sodium and iron in coal. They will interact with each other and form small number of crystals and most of the amorphous material.

Regulation Mechanism of Ash Fusion of Iron‐Rich Coal in Xinjiang with Different Additives

“…Unfortunately, when this iron-rich coal from Xinjiang is used as raw material in local coal-fired boilers, gasifiers, and other equipment, a more severe slagging phenomenon occurs. [11,12] It is worth noting that high-iron coal is not limited to Xinjiang; it is widely distributed throughout China. [13] Consequently, the future use of iron-rich coal as raw material in entrained bed gasifiers is inevitable.…”

“…In recent years, as coal mining in Xinjiang has progressed, certain coal seams have shown a new characteristic: high iron (Fe) content alongside the Na and Ca elements. Unfortunately, when this iron‐rich coal from Xinjiang is used as raw material in local coal‐fired boilers, gasifiers, and other equipment, a more severe slagging phenomenon occurs [11,12] . It is worth noting that high‐iron coal is not limited to Xinjiang; it is widely distributed throughout China [13] .…”

Ash fusion characteristics of iron‐rich coal in Xinjiang under different atmospheres and the influence mechanism of adding red mud and pipeline scale

“…However, in local coal-fired boilers and gasifiers and other equipment, when this Xinjiang coal with high iron content is used as raw material, a more serious slagging phenomenon will occur. 7,8 So far, to alleviate the above problems, the main measures taken by local enterprises are to further expand resource utilization by blending coal with Xinjiang coal or blending suitable additives to obtain blended coal. Usually, to ensure a sufficiently high carbon conversion rate, the addition ratio of coal blending can reach about 40-50%, while the addition ratio of additives is generally required to be less than 15%.…”

“…In recent years, with the continuous development of coal mining in Xinjiang, coal produced from some coal seams has high Fe characteristics except for Na and Ca elements. However, in local coal‐fired boilers and gasifiers and other equipment, when this Xinjiang coal with high iron content is used as raw material, a more serious slagging phenomenon will occur 7,8 …”

Performance of minerals and crystallization properties of synthetic slags with various CaO/MgO in slagging gasifiers

“…1 The influence of slag tapping in the entrained-flow gasifier has been widely studied. 2,3 During this process, high-temperature molten slag flows along the wall surface of the gasifier and discharged from the slag outlet of gasifier. The operating temperature of the entrained-flow gasifier is always above the ash fusion temperatures (AFTs) of coal ash to ensure the good fluidity of the slag.…”