Research on Blending Washing of Coking Raw Coal Based on Coal Quality Characteristics

Fine - grained coal blending and washing based on the coal quality characteristics of different coal resources is an effective means for coal enterprises to achieve resource integration and cost-effective operations. In order to investigate the influence of different proportions on the main indexes of clean coal, the complete float-sink analysis is carried out on raw coal samples from Pulongwan in Zuoyun District, Datong City (PLW) and from three surrounding mines (BJZ, HJW, KQ) to analyze the washability of the four raw coals. The basic coal quality characteristics of single coal and clean coal are analyzed through proximate analysis and washability tests. Three-stage float-sink tests are conducted on raw coal with different blending ratios. Key indicators such as the yield, ash content, sulfur content, and caking index of clean coal in the density fraction < 1.4 g/cm³ are compared to determine the optimal blending ratio for PLW raw coal. The results show that PLW and BJZ raw coals contain relatively high levels of minerals and gangue, resulting in lower clean coal yields. In contrast, KQ and HJW raw coals exhibit higher clean coal yields. Leveraging the coal quality characteristics, binary and ternary blending of PLW raw coal (with relatively low yield) with the other three raw coals is carried out to achieve clean coal with an ash content < 9%, sulfur content < 0.8%, and relatively favorable caking index. Within the blending ratio range specified in the plan: in the binary blending scheme, the highest clean coal yield is achieved when the blending ratio of PLW and KQ raw coal is 4∶6, reaching 35.12%. The ash content of clean coal is 6.21%, the sulfur content is 0.75%, and the caking index is 73, all meeting the expected blending washing index requirements, with a good effect. In the ternary blending scheme, the highest clean coal yield is achieved when the blending ratio of PLW, HJW, and BJZ raw coal is 4∶3∶3, reaching 32.00%. The ash content of clean coal is 8.10%, and the sulfur content is 0.73%, also meeting requirements. Based on the coal quality characteristics of single coals, blending and washing can compensate for the shortcomings of Pulongwan coal, such as high internal ash and low clean coal yield. This provides a strong basis and application guidance for subsequent coal blending and washing in coal preparation plants, thereby improving the economic benefits of coal preparation plants and rationalizing the utilization of coal resources.