ZLD: New Silica Based Inhibitor Chemistry Permits Cost Effective Water Conservation for HVAC and Industrial Cooling Towers

摘要

Zero liquid discharge (ZLD) approaches for cooling towers have existed for decades; but capital and operating cost generally made them impractical. New “green” chemistry now makes ZLD operation highly economical for small HVAC to heavy industrial tower systems. This new ZLD enabling process uses pretreatment removal of hardness to eliminate scale formation, and provides silica corrosion inhibitor chemistry to protect metals from corrosion at high total dissolved solids (TDS). Silica chemistry can be used with municipal or other water sources that can be softened by pre-treatment. The patented corrosion and scale inhibitor chemistry is particularly effective for waters that contain high levels of hardness, silica, chloride, TDS and soluble organics. Reuse or reclaim waste waters that contain soluble phosphate, organics and ammonia can also be used without corrosion, and biological proliferation is impeded by natural high pH and TDS chemistry. Silica corrosion inhibition chemistry protects all metals typically used in cooling water, including carbon steel, galvanized steel, and the various alloys of stainless steel, copper, and aluminum. Use of simple, salt efficient pretreatment equipment design permits even small cooling towers to be treated very cost effectively and reliably. Treatment costs are lowered by elimination of tower water wastage required with existing water treatment technologies, without sacrificing corrosion or scale protection. Corrosion rates are less than 0.1 mpy for all metals. This report presents results of case studies from a number of ongoing applications in HVAC and industrial cooling towers and reviews the respective source water qualities, tower water chemistries and system metallurgy evaluated.