A coil coating facility added a waste heat steam boiler to its pollution control system and saved $216,770 a year. Here's how the company did it.
The coil coater had a new a 15,000 scfm regenerative thermal oxidizer with a nominal heat transfer efficiency rate of 90 percent. The unit was designed with supplemental fuel injection used during low volatile organic compound-loading conditions, which helped save fuel, but the facility also wanted to decrease its exhaust-air temperature.
The high exhaust temperature, which was above 650°F (343°C), and the large airflow of 12,650 scfm in the oxidizer exhaust stack provided the customer an opportunity to add energy recovery measures that would further optimize its process and decrease operating costs. The coil coating process required a significant amount of steam, which likely would provide the quickest payback for an energy recovery project.
Anguil Environmental Systems Inc., Milwaukee, installed an air-to-stream waste-heat recovery boiler system to recover exhaust waste heat from a natural gas-fired regenerative thermal oxidizer to produce 25 psig steam. The boilers use X-ID tubing for enhanced heat transfer through the helical ribs on the inside of the tubes.
The skid-mounted waste heat boiler package has a forced-circulation, fire tube and heat recovery steam generator. The unit has an automatic modulating exhaust gas bypass controlled by steam pressure. The package also includes a boiler feedwater and blowdown separator.
Installing the waste-heat boiler system recovered approximately 2.58 million BTU/hr of energy, lowering the stack temperature to 338°F (170°C). The addition of the boiler package on this application saved the facility $216,770 annually for total payback of less than six months.