Accommodating Process Variation in the Design and Sizing Of Thermal Drying Facilities
Abstract:The City of Wilmington's James A. Loughlin Wastewater Treatment Plant liquid and solids treatment trains are currently being designed for upgrade and expansion to 16-mgd capacity. Class A residuals management alternatives were investigated as a part of the preliminary engineering phase due to concerns over the long-term viability, risks and economics of the current Class B land application program. These preliminary investigations resulted in the selection of thermal sludge drying as the preferred Class A residual management alternative.
Specifically, this paper presents the following information related to the sizing and operating economics of the thermal drying facilities:
Development of the thermal dryer sizing design basis using an influence diagram process design model coupled with a Monte' Carlo statistical simulation. This model develops a design basis for total dry sludge production, water evaporation rate, and thermal dryer utilization rate.
Development of the thermal dryer economic cost model using an influence diagram model coupled with a Monté Carlo statistical simulation. This model examines both the incremental operating costs and the fully allocated costs for development of the thermal drying alternative as compared to the current Class B land application program
This approach for conducting the sizing and economic evaluations provides for the rapid and simultaneous consideration and evaluation of a combination of possible input variables on the key output performance criteria. Simulation results indicate that a thermal dryer with 4,000 kg per hour (8,800 lbs./hr) evaporative capacity would provide sufficient thermal drying capacity to eet process needs at the 16-mgd design flow condition. The economic evaluation simulation indicated that the incremental operating costs associated with thermal drying were less than the current Class B land application program operating costs, however, the fully allocated costs for thermal drying were greater than the current Class B land application program costs.
Document Type: Research Article
Publication date: 2002-01-01
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