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A S Jessup-Bould:

Sewage Sludge Incineration and Gas Cleaning Experience







Project Background




End Client: North West Water, Shell Green, Widnes



This sewage sludge incineration facility was designed and built by OSC Process Engineering as part of North West Water’s (United Utilities) Mersey Valley Processing Centre at Shell Green. The plant accepts sewage sludge from the Manchester and Liverpool conurbations.






Process Design of Flue Gas Cleaning and Chemical Storage / Dilution


Plant operating manuals.


Commissioning Shift Team Supervisor.

Responsible for client's personnel training.





Summary of Process





Sludge containing 3% dry solids is received and processed in the Dewatering Hall. The resulting 30% dry solids cake is received in the buffer storage silos.

The sludge is combusted in 2 fluidised bed incinerators each rated at 2.8 tonnes per hour dry solids, with waste heat being used to raise steam for power generation and export to the grid.

Ash carried in the flue gas is removed in the bag filter. Scrubbing removes heavy metals and acid components. Final polishing with PAC/Lime removes trace volatile metals and other contaminants.

Specific Responsibilities

  • Process Design Engineer (Including bag filtration, reagents storage and handling).
  • Production of operating manuals.
  • Training of commissioning and plant personnel.
  • Commissioning Shift Team Leader.

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  • The successful commissioning of OSC's only sewage sludge incineration facility.







Unit Operations



Sludge pumping.

Steam raising system.

Cooling water system

Power generation. (Steam / diesel driven).

Bag filtration.

Flue gas scrubbing.

Condensation & heat exchange.

Dense & lean phase solids conveying.

Solids cooling & mechanical conveying.

Materials of Construction

Steels; carbon, stainless, hardened, lined.

"Derekane", refractory brickwork.

Documents Produced

PFDs & mass balances.


Process data sheets.

Operating manuals.

Training manuals.



Combustible solids (sludge, activated carbon).

Fuels (natural gas, gas oil).

Gases arising from process (CH4, H2S, CO).

Corrosive reagents (Conc HCl & NaOH).

Corrosive process liquors.

Dusts containing heavy metals.

Hot surfaces and materials.

High voltage switch gear.

Heavy rotating machinery.


Confined spaces.


OSC commissioning team.

OSC construction team.

Principle contractor's engineers.

Client's plant management, operating & maintenance personnel.

OSC sub-contractors and Dewatering plant contractor.

Standards etc.

Commissioning plan.

Permit to work, hot-work permits.