A municipal waste water treatment plant operates a 2,750 lb/hr fluid bed sewage sludge incinerator (SSI). The 
incinerator had been shut down due to safety issues with the granulated activated carbon (GAC) mercury control scrubber. The plant sought expert help to evaluate and recommend a technology solution to replace the GAC and to get the SSI back in operation.
Based on extensive waste incineration gas cleaning experience, the facility contracted Envitech to evaluate the process, make recommendations, and implement a solution.
Envitech reviewed
available literature and data to establish a conservative but justifiable design inlet concentration with sufficient capacity to meet a more conservative design condition without structural changes to the equipment.
An additional Envitech study compared W.L. Gore sorbent polymer catalyst (SPC) mercury control modules to sulfur impregnated activated carbon taking into account capital and operating cost, mercury removal efficiency, safety, and performance risk. The facility implemented Envitech’s recommendation for an Envitech SBC mercury control scrubber. A vessel constructed of fiber reinforced plastic (FRP) provides excellent corrosion resistance and low cost. An inlet heater duct with controls optimizes temperature for maximum performance. An internal duct with bottom outlet near grade direct connects to the existing stack. The vessel has extra capacity to double the number of SPC modules to meet the conservative inlet concentration if needed.
The equipment was commissioned in December, 2018. Inlet and outlet stack tests confirm greater than 96.4% removal and emissions less than 5% of the MACT limit for existing FB SSI. The Envitech SPC mercury control scrubber provides an economic, high performance, safe solution for continued incineration operation. It can be applied to other types of applications that require mercury control downstream of wet scrubber equipment. It provides a worthwhile technology to consider for mercury control.
Click on the link below to download a sewage sludge incinerator (SSI) mercury control scrubber case study and other SSI incinerator scrubbing literature.
