Refurbishment of an Aging Fluid Bed Biosolids Incinerator and Development of a 10 year Capital Plan: An Alternative to Replacement
Abstract:The City of London, Ontario operates a 60 dry tonne/day hot wind box fluid bed incinerator (FBI) at the Greenway Pollution Control Centre (PCC) to dispose of the biosolids generated at all of its municipal sewage treatment plants. The incinerator was commissioned in 1988 and had been in continuous duty since, with the exception of annual maintenance shutdowns. Currently the incinerator runs 6 or 7 days per week, 24 hours per day.
In 2007, meetings and site inspections were completed at the request of the City to investigate potential repairs to their FBI. Numerous areas on the upper freeboard of the FBI were severely degraded and had been extensively previously patched. Historic non–destructive testing results indicated that in localized areas less than 50% of the original steel casing thickness remained on the incinerator freeboard. Based on the age of the facility (20 years of operation), preliminary analysis of the information available, and our experience at other similar installations, AECOM identified the likely need for much more extensive repairs than originally anticipated by City staff.
A detailed incinerator assessment was completed in 2007 which involved identifying the system components, reviewing and recording the past repair history, identifying critical process equipment, evaluating the current condition of process equipment using various non-destructive testing techniques, estimating the remaining life, estimating the repair costs of the critical process equipment, and generating a capital timeline and cash flow.
The Report evaluated a number of scenarios ranging from simple repair to refurbishment to replacement with a new incinerator and considered capital cost as well as operating impacts (downtime). An implementation plan consisting of staged repairs, including an initial 4.6 million refurbishment and a total 10 year capital repair cost anticipated to be 13.4 million was recommended. This compares to 32+ for a new incinerator (depending on ancillaries) and interim repairs to the existing unit during procurement and construction.
Based on the recommended scope of work, a construction methodology was developed and a construction contract was tendered. Included in the scope of the project was detailed design of new incinerator refractory, new incinerator upper sidewalls and roof steel, new incinerator refractory lined outlet ductwork, new air to air pre-heater, new flue gas re-heater, and modified venturi scrubber.
Work on the 4.6M project occurred from 2007 to 2009. Given the high cost of disposing of sludge during the downtime a major consideration was limiting the downtime to the extent possible. An innovative construction incentive approach, consisting of penalties and bonuses was used to obtain the optimum balance between capital cost and downtime operating costs. The innovative approach resulted in the project being completed ahead of time and below budget.
Document Type: Research Article
Publication date: January 1, 2011
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