The Huangyuchuan coal preparation plant wanted to make more money by improving how they process coal. They tried different ways to clean the coal that comes from their mine. They found that blending No.4 and No.6 coal in a specific ratio (4 parts No.4 coal to 6 parts No.6 coal), then screening it with a 25 mm screen and washing only the bigger pieces (200 mm to 25 mm), helped them get more useable coal without extra costs. Mixing the tiny waste (slime) into the good coal also made the process more efficient and profitable. So, this approach of blending and selective washing improved the economic benefits of the plant.