The article discusses how the Huangyuchuan Coal Preparation Plant designed a process to improve coal quality for sale to power plants. By studying the coal properties from specific seams, they developed a washing process to make different coal products. They use methods like shallow slotting for big pieces and cyclones for smaller particles. The process helps make many types of coal products efficiently. Since the plant started using this method, it has been successful in producing high-quality coal that meets market demands.