Desalter costs

While a desalter costs more to install than the flash drum system, it has the advantage of removing up to 95% of the salt from the oil permanently. Because less salt reaches the fractionating tower in a unit equipped with a desalter, a smaller quantity of corrosion products is formed due to high temperature breakdown and hydrolysis, and the salt content of the residual fuel oil is much lower. 

Neutralizing chemicals (incl. half of desalting cost). 

Equipment and Economics A veiy large electrodialysis plant would produce 500 /s of desalted water. A rather typical plant was built in 1993 to process 4700 mVday (54.4 /s). Capital costs for this plant, running on low-salinity brackish feed were 1,210,000 for all the process equipment, including pumps, membranes, instrumentation, and so on. Building and site preparation cost an additional 600,000. The building footprint is 300 itt. For plants above a threshold level of about 40 m Vday, process-equipment costs usually scale at around the 0.7 power, not too different from other process eqiiip-ment. On this basis, process equipment (excluding the ouilding) for a 2000 mVday plant would have a 1993 predicted cost of 665,000. 

One of the most important operations in a refinery is the initial distillation of the crude oil into its various boiling point fractions. Distillation involves the heating, vaporization, fractionation, condensation, and cooling of feedstocks. This subsection discusses the atmospheric and vacuum distillation processes which when used in sequence result in lower costs and higher efficiencies. This subsection also discusses the important first step of desalting the crude oil prior to distillation. 

During cheese making, the coagulated milk or curd is used to make cheese while the supernatant whey is a waste product rich in salts, proteins, and lactose. Whey concentration and desalting by UF produce a retentate product that can be used as an animal feed supplement or food additive. The MMV process (Maubois et al., French Patent 2,052,121) involves concentrating the milk by UF after centrifugation to remove the cream and before coagulation to improve yields and reduce disposal costs. 

The synthesis of complex carbohydrate structures can preferably be accomplished using several enzymes in one-pot or sequential mode. Crude intermediate products may be either directly processed by the follow-up enzyme, or a fast and simple purification step may be included like desalting, concentrating, etc. This approach saves both time and costs, however, it requires a relatively high specificity, regioselectivity and yields in all the steps, which somehow limits the choice of glycosidases available. 

The energy requirements and a summary of the costing of the listed alternatives, based on large capacity plants in the range of 100,000 cu. m/day for seawater desalting and 20,000 cu. m/day or larger for brackish feeds, are shown in Table IV. 

Table IV Energy requirements and costing of desalting alterantives for Israel... 

Ion exchange processes use natural or synthetic granular materials that exchange one ion for another. The new (captured) ion is held for a finite period and then released to a regenerating solution. Because regeneration costs increased proportionally with the TDS reduction, the ion exchange process has not been competitive with membrane processes for desalting... 

If the derivative of the cost expression is set equal to zero and solved for current density, a value is obtained which will desalt the water at smallest cost. This smallest cost, the required optimum current, and the resulting membrane area are ... 

Lorain, O., B. Hersant, F. Persin, A. Grasmick, N. Brunard, and J. M. Espenan. 2007. Ultrafiltration membrane pre-treatment benefits for reverse osmosis process in seawater desalting. Quantification in terms of capital investment cost and operating cost reduction. Desalination 203 277-285. 

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