Cleveland Experience three New Fluid Bed Municipal Sludge Incinerators and A Steam Turbine To Generate Power

Southerly Wastewater Treatment Center is located at 6000 Canal Road, Cuyahoga Heights, Ohio and is owned and operated by the North East Ohio Regional Sewer District (NEORSD). The plant serves more than 600,000 people living in the area and has an average wastewater treatment capacity of 473 million liter per day (125 million gallon per day, mgd). Maximum wastewater treatment capacity is 1.5 billion liter per day (400 mgd). The plant has another 1.3 billion liter per day (335 mgd) additional capacity for the primary treatment of storm water.Southerly plant has three new fluid bed incinerators (one stand by) with three heat recovery systems producing superheated steam to generate power through a steam turbine, which is designed to handle two incinerators due to one incinerator being on stand-by during normal operation. Turbine is designed to generate 2.4 MW when two incinerators are in operation with 11,975 kg/hr (26,400 lb/hr) steam flow. Maximum power generation rate for the turbine is 3.54 MW, when three incinerators are in operation having 18,144 kg/hr (40,000 lb/hr) steam flow. All three fluid bed units are of type hot wind-box with refractory arch air distributor and refractory lined windbox. Each fluid bed unit has the capacity to incinerate 90.72 metric dry ton per day (100 US dry ton per day) (DTPD) total solids.Unit No. 2 passed the performance testing on Sept. 3, 2014. Unit No. 1 passed the performance testing on Sept. 23, 2014. Unit No. 3 passed the performance testing on Oct. 7th, 2014. All three fluid bed units have satisfied the emission requirements listed in the air permit and project specifications. All three units have been retrofitted in 2015 with the mercury removal system to be in compliance with US EPA MACT Quad M emission limits. Stack emission tests in 2015 and 2016 indicated that all three retrofitted units were in compliance with MACT limits for an existing fluid bed incinerator.Each fluid bed unit is equipped with a waste-heat recovery system employing a primary heat exchanger and a waste heat boiler. Primary heat exchanger (shell and tube design) is used to preheat the fluidization air to approximately 584 C (1,083 F) minimizing the auxiliary fuel usage during the steady state operation. Each unit was designed to be autogenous at 68% volatile, 28% total solids, and 5,833 kcal/kg (10,500 BTU/lb) sludge heat value based on volatile part of dry solids including skimmings (processed grease and fats) introduced into the sludge cake. Flue gas from the fluid bed reactor is passed through a primary heat exchanger and then discharged into a waste heat boiler to produce 6,895 kg/hr (15,200 lb/hr) superheated steam at 371 C (700 F), 44 barg – 4,400 kpa (635 psig). From waste heat boiler, flue gas is sent to a plume suppression heat exchanger and then discharged into a wet scrubber to remove particulate and acid gases (SO2, HCl). Wet scrubber is not equipped with a caustic injection system. Clean flue gas discharged from the wet scrubber flows through the mercury removal system and an ID Fan before being discharged into the plume suppression heat exchanger (shell and tube design). ID Fan is installed between the mercury removal system and plume suppression heat exchanger to maintain vacuum conditions inside the waste heat boiler to prevent any potential flue gas/ash leak into the building. Plume suppression heat exchanger is used to suppress the visible plume in stack by increasing the clean flue gas temperature to 121C (250F).The text provides the detailed information on the process, the scope of equipment installed and the information regarding the performance test results.Southerly fluid bed units have been successfully started up, commissioned, and passed the performance testing in 2014, 2015, and 2016, respectively. All three units have met the emission requirements listed in the air permit, project specifications and MACT limits. The successful operation at Southerly plant has shown that the improved thermal oxidizer design incorporating a power generation system can reduce the operational expenditures significantly and is also an economical, environmentally friendly, and cost effective solution for sludge disposal.