Evaporation:Energy

Management of the Metal Removal Fluid Environment

Evaporation:Energy

Cost Of Energy Required For Evaporation

It requires 960 (British Thermal Units) BTUs of energy to turn one pound of water into steam. Natural gas has approximately 1,000,000 BTUs of energy per thousand cubic feet. Propane has 91,300 BTUs of energy per gallon. Electricity has 3,412 BTUs per kilowatt-hour. Fuel oil has approximately 135,000 BTUs of energy per gallon. Natural gas, propane, and fuel oil operate at efficiencies in the range of 65% to 75%. Electrical systems can operate at efficiencies near 99%.

Example Calculation:

How much does it cost to evaporate 1,000 gallons of a spent metal removal fluid?

Assume: 5% oil by volume starting concentration

Final concentration is 50% oil and water (volume/volume)

Natural gas is the fuel

System efficiency is 65%

Natural gas costs $6.50 / 1000 cubic feet ($6.50/MCF)

950 gallons water + 50 gallons of oil = 1,000 gallons starting volume

950 starting gallons of water - 50 gallons water remaining = 900 gallons water to evaporate.

900 gallons of water x 8.34 pounds of water per gallon = 7,506 pounds of water to evaporate.

7,506 pounds of water x 960 BTUs to evaporate one pound of water = 7,205,760 net BTUs.

7,205,760 net BTUs ¸ 0.65 system efficiency = 11,085,784 total BTUs required

11,085,784 BTUs ¸ 1,000,000 BTUs per MCF natural gas = 11.1 MCF natural gas required

11.1 MCF x $6.50 Per MCF of natural gas = $72.15 to treat 1,000 gallons of metal removal fluid by evaporation or about 7.2 cents per gallon.

This leaves 100 gallons left to haul at 50% water and 50% oil.

Membrane Cost Comparisons (1998)

Type	Base Cost per Sq. Ft.	Cost for Anticipated Module Life per Sq. Ft.
1" tubes	$150	$23
½" tubes	$40	$20
hollow fiber (5")	$32	$16
spiral (4")	$24	$16
spiral (8")	$14	$10

Quantity ordered affects costs. Above represents cost for "mid-size" orders. Expect higher costs for smaller orders and lower costs for higher volume orders.

Prepared by AWARE Services