Operating cost refrigeration

Both vacuum operation and the use of refrigeration incur capital and operating cost penalties and increase the complexity of the design. They should be avoided if possible. For a first pass through... 

The operating cost for the refrigerant needed for toluene condensation is S6.0 X 10 / kg of toluene-laden air. 

The operating cost of the yth refrigerant (denoted by Cj, /kJ removed) is known. The flowrate of each refrigerant is unknown and is to be determined through optimization. 

In addition to the fixed capital investment needed to purchase and install process equipment and auxiliaries, there is a continuous expenditure referred to as operating cost, which is needed to operate the process. The operating cost (or manufacturing cost or production cost) includes raw materials, mass-separating agents, utilities (fuel, electricity, steam, water, refrigerants, air, etc.), catalysts, additives, labor, and maintenance. The total annualized cost of a process is defined as follows ... 

Operating costs can be estimated based on statistical analysis of operating costs in existing plants. Costs of waste disposal can be evaluated in the same way as costs for any chemical process since procedures for disposal include, in fact, unit chemical processes and operations. Costs of utilities and maintenance are best assessed based on the company data banks. Typical utility figures per m capacity of reactors in MPPs are 800-1100 kg steam/h, 60-80 kW power, and 7,000-8,000 kJ/h refrigeration capacity. 

If the feed is partially vaporized, the vapor flow below the feed will be lower than the top of the column. For above ambient temperature separations, the cost of operating the distillation will be dominated by the heat load in the reboiler and the vapor flow in the bottom of the column. For below ambient temperature separations, the cost of operating the column will be dominated by the cost of operating the refrigerated condenser and hence the vapor flow in the top of the column. If constant molar overflow is assumed, the vapor flow in the bottom of the column V is related to the vapor flow in the top of the column by... 

As noted already, the electrical energy needed to run the refrigeration unit for liquefaction of chlorine is about 335 kj kg-1, equivalent to 93 kWh per tonne of chlorine. The annual power consumption will be 19.5 million kWh. At a power cost of 5c per kWh, the annual cost is close to US 1.0 million. There will also be an operating cost associated with the incremental cooling water usage that has not been included. 

For routine work at around 0°C on any form of data collection device, a simple low-temperature attachment may be constructed from a copper coil, a refrigerated ethanol bath, a headess air drier, a compressor, and a flexible hose (Marsh and Petsko, 1973). Such an apparatus costs less than 2000 to build and has essentially no operating costs. It fulfllls the most important criterion for a successful low-temperature device that it be so easy to operate as to encourage its use. Its disadvantage is that very low temperatures are not attainable without more sophisticated—and expensive—hardware. 

The major costs involved in a home refrigerator are the capital costs of buying the compressor, the heating and cooling coils, the circulation pipes, and the expansion valves, as well as the yearly operating cost of electricity and maintenance. 

An HD CatOx system having a capacity of 200 standard cubic feet per minute (scfm) is priced at approximately 150,000 (1992 dollars). Daily operating costs for utilities and the caustic for hydrochloric acid neutralization are about 200 (1992 dollars). The preheater s monthly operating cost would be 220. Monthly electrical costs for the extraction blower and refrigeration unit would be approximately 800 (D135319, p. 530 D13108Y, p. 50). 

Nitrobenzene has the highest solvent power for extract oils and is best suited for Pennsylvania stocks. However, its high boiling point makes recovery difficult and its high solvency necessitates low temperature operation which requires costly refrigeration. 

For example, propylene and ethylene of polymer grade have been distilled at pressures as low as 4 bar and 6 bar absolute, respectively. However, the condenser must be operated at temperatures of -12.2°C for propylene, and -68°C for ethylene. This latter very low temperature will be produced by a costly refrigeration system. 

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