Water Network Integration And Optimization Of Coal To Methanol Process

New coal chemical industry, as an important way of clean utilization of coal, has been recognized as an important method to satisfy the demand of oil and gas. Coal chemical industry in China is mainly located in the area which is rich in coal and deficient in water resource. However, coal chemical industry has a large amount of water consumption and wastewater discharge. Therefore, the conflict between the growing demand of regional water and water shortage has become a bottleneck affecting the development of coal chemical industry.Based on the principle of traditional water pinch analysis, a new concept of water footprint pinch analysis is proposed. From the point of view of life cycle, a framework for water management is proposed. In the framework the location of coal to methanol plant is first identified, i.e. in the "rich" or "poor" area. Then, it can determine the water saving strategies with water footprint pinch analysis based on different water saving target. When the plant located at water deficient area, it has a high water-saving goal. The appropriate strategy is to reduce the water consumption of the whole process, i.e. coal and methanol production. When the plant is located at water rich area, it has less pressure of water shortage and requires a low water-saving target. The feasible solution is only considered water saving water from the methanol production process.For methanol production process, the water utilization of all the units is analyzed in detail and the water balance of the entire enterprise is presented. Water-using network with multiple contaminants is designed by step by step linear programming method. The minimum freshwater consumption is identified as 87 t/h, which has a freshwater reduction of 52.2%.For the coal production process, two water-saving scheme i.e. direct reuse and regeneration for reuse were analyzed using water cascade analysis. For the water direct reuse scheme, both the minimum freshwater consumption and wastewater discharge are identified as 386.5 t/d. It has reduced freshwater consumption by 48.1% compared with the base case. For the water regeneration for reuse scheme, both the minimum freshwater consumption and wastewater are determined as 196.70 t/d, which can achieve a freshwater saving target of 73.6%. Finally, the nearest algorithm was used to design the water network with the minimum freshwater consumption target.