Combu-Changer Regenerative Thermal-oxidizer System Provides Phased Low-solvent VOC Abatement
In 1988, a major Wisconsin coater and converter initiated a solvent volatile organic compound (VOC) reduction program to meet or exceed federal EPA and State of Wisconsin, Department of Natural Resources (DNR) abatement requirements. Initially, a 15,000 scfm coating line was brought into compliance with <%=company%> patented air-preheater Combu-Changer® regenerative thermal-oxidizer system, which provided a 95 percent primary energy recovery and virtually fuel-free operation above a 2 percent LEL (lower explosion limit) solvent loading.
The company selected the Combu-Changer for its patented in-bed combustion design, which allows incineration and oxidation of high or low VOC emissions at temperatures exceeding 1800 F inside a compact gravel heat exchanger. The result is a space-saving modular design that installs for one-fourth to one-third the cost of canister designs and in less than half the time. Each of the systems provides greater than 95 percent solvent VOC control with no traceable nitrogen oxides (measured according to U.S. EPA Method 18 and Method 25A stack tests). Competitive burner-fired regenerative systems could not achieve the levels obtained with the clean electrical heating system integral to the ABB system.
The coater/converter's in-house technical staff took on an energy-recovery, air-handling, air-pollution control consultant to aid in the project's design and implementation. The consultant provided the turnkey installation, interconnecting ductwork design, capture systems, and process/controls interface. In 1989 the company's engineers again teamed with the same consultant to provide six additional Combu-Changer modules, bringing into compliance a connected process-flow load of 72,000 scfm.
The consultant's design allows process-flow diversion from any solvent-coating source to virtually any group of oxidizers. This setup provides for isolating individual regenerative modules for inspection or maintenance without process shutdown. Each of the seven regenerative thermal oxidizer modules situates on the ground between the plant and an access road.
The consultant's experience in process-flow reductions allowed the coater/converter to obtain 100 percent capture efficiency from the solvent-based coating lines and floor sweeps--the first such capture system approved by the State of Wisconsin's Department of Natural Resources.
The coater/converter called again on the design and installation experience of its consultant in 1990 when it added a 30,000-scfm ABB Air Preheater, Inc. Cor-Pak®. The addition of the recuperative thermal oxidizer system allowed the company to switch an existing aqueous-based coating line to accommodate a high-solvent adhesive- and tape-coating line. The system provides 99+ percent VOC abatement at typical solvent loadings in the range of 10-35 percent LEL. This recuperative system uses a durable shell-and-tube metallic heat exchanger custom-designed for high-solvent operation that is rated at 70 percent primary heat recovery. An integral hot-gas bypass protects the system's heat exchanger from excessive metal temperatures at solvent loadings above 25 percent LEL. A second, smaller 15,000-scfm Cor-Pak system was installed in 1992.
According to the client and its consultant, ABB Air Preheater provides them with expedient, first-rate, timely service. The converter now has nine ABB Air Preheater regenerative and recuperative thermal oxidizers. They handle more than 130,000 scfm of process air while providing maximum achievable control technology (MACT) to meet the environmental air-quality regulations of today and the future. The same modular expandable approach will likely come into play during additional expansions, providing this converter with leading-edge affordable technology for a controlled environment.
Combu-Changer Regenerative Thermal Oxidizer with In-bed Combustion Design