Problem 1 Cost for Hydrogen Recovery by ActivatedCarbon Adsorption Process
What is the cost, as cents per 1000 ft3 (at SC) of 95 mol % H2, for recovering hydrogen of 95 mol % purity from 10 million ft3 (at SC) of gaseous feed per day if the following conditions apply?
Feed composition by volume = 72.5 percent H2 and 27.5 percent CH,.
A hydrogen-recovery method based on selective adsorption by activated carbon will be used.
For the carbon adsorption, three separate beds will be needed so that one bed can be in continuous use while the other two are being desorbed or reactivated. Base the recovery on a single pass and an absorption cycle of 1 hour per bed.
0.00838 mol of material is adsorbed per hour per pound of activated carbon.
The composition of the adsorbed phase is 96.8 mol % CH„ the balance being hydrogen.
The cost of activated carbon is $3.65 per pound.
The annual amount of additional carbon necessary is 15 percent of the initial charge.
The total plant cost (equipment, piping, instrumentation, etc.) equals $4,750,000.
following problems are recommended for solution by students working in groups of two or three during a three-hour practice session. Many of these problems have been adapted from old Annual AIChE Student Contest Problems as shown by footnotes for the individual problems. The original problems and winning solutions are available from AIChE Headquarters, 345 E. 47 St., New York, NY 10017. A useful procedure for using these Practice-Session Problems is to have students examine the original AIChE Student Contest Problem and Solution before the class period and then have someone (student or teacher) present a discussion on it in the first ^ hour or 1 hour of the practice session. Then the students can break up into groups and carry out the solution to the problem assigned during the last 2 hours of the practice session. It is desirable for the students to have an opportunity to examine the correct solution to the problem immediately after they turn in their solution at the end of the 3-hour session. ^Adapted from 1947 AIChE Student Contest Problem.
The capital investment equals the total plant cost plus process materials (process materials are considered as auxiliaries-i.e., process materials are only the initial charge of activated carbon).
The capital investment must be completely paid off (no scrap value) in 5 years.
The operating cost per year, including labor, fuel, water, feed, regeneration, fixed charges minus depreciation, and repairs and maintenance, equals (operating costs not included in this value are the cost of the additional make-up carbon necessary and depreciation).
The plant operates 350 days/year.
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