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9.3 Fixed Cost Summary
Fixed costs for the process were estimated according to the methods described in Seider, Seader, Lewin, and Widago. Operations expense was estimated by assuming 6 operators per shift
with 5 shifts, an hourly wage of 40operator hour, and including 30 of direct wages and benefits. Maintenance expense was estimated by including 4.5 of depreciable capital for wages
Table 9.4: Fixed Cost Summary
Operations Direct Wages and Benefits
2,496,000 Direct Salaries and Benefits
748,800 Operating Supplies and Services
149,760 Technical Assistance to Manufacturing
4,500,000 Control Laboratory
4,500,000 Total Operations
12,394,560 Maintenance
Wages and Benefits 3,026,807
Salaries and Benefits 756,702
Materials and Services 3,026,807
Maintenance Overhead 151,340
Total Maintenance 6,961,656
Operating Overhead General Plant Overhead
527,123 Mechanical Department Services
210,849 Employee Relations Department
421,699 Business Services
520,095 Total Operating Overhead
1,679,766 Property Taxes and Insurance
Property Taxes and Insurance 2,017,871
Other Annual Expenses Rental Fees:
- Licensing Fees:
-
Total Fixed Costs 23,053,854
108 and benefits, 25 of maintenance wages and benefits for salaries and benefits, 5 of
maintenance wages and benefits for maintenance overhead and 100 of maintenance wages and benefits for materials and services. Operating overhead was computed as 7.5 of wages and
benefits for general plant overhead, 3 of wages and benefits for mechanical department services, 6 of wages and benefits for employee relations department, and 7.4 of wages and
benefits for business services. Property taxes and insurance were estimated as 3 of total depreciable capital. Depreciation is not calculated as an operating expense and instead the
MACRS depreciation schedule is used.
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9.4 Pricing of Wastewater and Purge Streams
A cost was assigned to the aggregated wastewater stream as a function of the flow rate of water in gpm and the loading of organic compounds. The operating cost of Deep-Tank
Activated-Sludge Treatment is 300yr ·gpm of hydraulic flow plus 2,000yr·lb organichr,
summing to 7,564,660 per year with the current waste water stream.
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The resulting water stream is then considered safe to discharge into the environment. As stated in the project charter,
the design and costing of construction of the wastewater facility is considered out of project scope, and the investment costs of the wastewater plant were not calculated.
The lower heating values of propane, propene, acrylic acid, and acetic acid were mass- weighted and used to calculate the resulting heating value of the stream. Approximately 116.1
MM BTUhr can be released through burning the purge stream. If this stream could be converted to electricity with an assumed 20 efficiency at 0.16kWh, the stream is worth approximately
8.6 million per year. Alternatively, if the same stream could be converted to heat at 50 efficiency at 0.06kWh, the stream is worth 8.1 million. It was determined that it will be more
economical to convert the stream to heat in order to avoid the considerable equipment costs of turbines, generators, condensers, and the like that would be required to generate the electricity.
The heating value of 116 MM BTUhr can be deducted from the required energy utility inputs.
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Mulholland, K. L., Dyer, J. A. 1998. Pollution Prevention: Methodology, Technologies and Practices: American Institute of Chemical Engineers.
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