This work focused on the integrated process of the recirculating cooling water (RCW) treatment to achieve approximate zero emission in the coal chemical industry. The benefits of fractional and comprehensive RCW treatment were quantified and qualified by using a water and mass balance approach. Limits of cycle of concentrations and some encountered bottlenecks were used to ascertain set target limits for different water sources. Makeup water was mixed with water produced from reverse osmosis (RO) in the proportion of 6:4, which notably reduced salts discharge. Side infiltration, which settled down suspended solids, can reduce energy consumption by over 40%. An automated on-line monitoring organic phosphorus inhibitor feed maintains the RCW system stability in comparison to the manual feed. Two-step electrosorb technology (EST) instead of an acid feed can lead cycle of concentration of water to reach 7.0. The wastewater from RO, EST and filter was transferred into a concentration treatment system where metallic ions were adsorbed by permanent magnetic materials. Separation of water and salts was completed by using a magnetic disc separator. Applying the integrated process in a coal chemical industry, a benefit of 1.60 million Yuan annually in 2 years was gained and approximate zero emission was achieved. Moreover, both technical and economic feasibility were demonstrated in detail.
Keywords: limiting cycle of concentration, permanent magnetism, reverse osmosis, zero emission