Problems with coal crushing in ramming coking

Either method works; in my opinion, it’s better to grind first and then mix, as grinding results in a more uniform mixture. With finer particles, the surface area in contact during mixing increases, which leads to a more even mixture.

Most are mixed first and then powdered. If there are large pieces, pre-crushing can be performed.

The fineness of the coal used in combustion is related to factors such as the crusher, the amount of coal fed in, and the gap between the hammers; adjustments are required in all these areas. For the crushing process, it is recommended to mix first and then crush, so as to achieve uniform mixing. For certain types of coal, such as bituminous coal, pre-crushing can be employed.

We are currently using the method of preparing first and then adding powder, which helps optimize the manufacturing process and yields good results

For most cases, mixing is done first followed by grinding; for hard-to-grind coals such as bituminous coal and lean coal, pre-grinding can be carried out before mixing

The process of mixing first and then crushing involves first combining the various types of coal used in coking at specified proportions, and then carrying out the crushing process. Referred to as the “Hunpo” process, this is the process flow. This type of process is characterized by simple technology, compact layout, few pieces of equipment, low investment costs, and easy operation. However, it is not possible to adjust the particle size of grinding according to different coal types during operation; therefore, it is only suitable for coal with a relatively uniform quality and good caking properties. When there are significant differences in the hardness of the raw coal, the particle size of the crushed material becomes uneven, which has an impact on the quality of the coke. However, due to its low investment requirements and simple operation, this process is widely used in many coking plants. First, the coal is crushed, and then a blending process is carried out. In this process, the various types of coal that make up coking coal are crushed to different degrees of fineness depending on their respective properties, and then blended together in specified proportions in order to improve the quality of the coke. However, this process is complex; it requires multiple crushers, and separate mixing equipment is needed after coal blending, resulting in high investment costs and complicated operations. To simplify the process, when coking coal consists of only 1–2 types of coals with high hardness, these hard coals can be pre-ground first, and then mixed in proportion with other coals before being ground further. Since the fineness requirement for gas coal is higher than that for coking coal and fat coal, this process is often used for the pre-grinding of gas coal. The location of some coal pre-crushers can be placed in front of the coal blending bin or behind it. In the former arrangement, the capacity of the pre-crusher must be compatible with that of the coal conveying system prior to coal blending; as a result, the pre-crusher is large in size and requires significant investment in equipment ； The capacity of the pre-crusher in the latter arrangement can be appropriately reduced, resulting in lighter equipment and lower investment costs. Group crushing process flow: This process flow involves first grouping the various types of coal that make up the blended coal according to their different properties and requirements, then crushing each group to a different degree of fineness, and finally mixing them together. Compared with the process of crushing first and then mixing, this process reduces the need for crushing equipment, thereby simplifying the procedure ； Compared to the process of mixing first and then crushing, it requires more coal mixing tanks and crushers, resulting in higher investment costs. Therefore, it is generally used in coking plants with large production scales, a large variety of coal types, and significant differences in coal quality. Select the crushing process flow. The characteristic of this process is that it takes into account the differences in hardness among various coal types and lithological compositions in the coking coal feed, and combines crushing with screening according to the required particle sizes, thereby achieving uniformity in the coal material. This eliminates large particles, prevents excessive fine grinding, and ensures that the inert components reach the desired fineness. 　　Depending on the coal quality, there are various processes available for crushing. For coal materials with good coking properties but uneven lithological composition, a single-pass cyclic crushing process that first screens out the fine particles can be employed. During transfer and loading/unloading, coal with high contents of cohesive components and soft vitrinite is easier to crush, resulting in smaller particle sizes. To avoid excessive pulverization, these materials are first screened out; the larger-sized, less compressible inert components and coal lumps that remain on the screen are then fed into the crusher for crushing. Subsequently, they are mixed with the original coal in a mixing drum, and the fine particles are screened out again, with the material remaining on the screen being sent back for further crushing. This allows various coal and lithofacies components to be crushed to roughly the same particle size, thereby improving the coking process. When the coal mixture contains coal types with significant differences in caking tendency, the single-pass circulation approach, which controls the particle size composition based on one particle size range, cannot meet the requirement to adjust particle sizes according to different caking tendencies; therefore, a multi-pass circulation system should be used to select the appropriate crushing process.