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

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.