Question

A storage tank is purged continuously with a stream of nitrogen. The purgestream leaving the tank is saturated with the product stored in the tank. A majorpart of the product lost in the purge could be recovered by installing a scrubbingtower to absorb the product in a solvent. The solution from the tower could befed to a stage in the production process, and the product and solvent recoveredwithout significant additional cost. A preliminary design of the purge recoverysystem has been made. It would consist of:1. A small tower 0.5 m diameter, 4 m high, packed with 25 mm ceramic saddles,packed height 3 m.2. A small storage tank for the solution, 5 m3 capacity.3. The necessary pipe work, pump, and instrumentation.All materials of construction, carbon steel.Using the following data, evaluate whether it would be economical to install therecovery system:1. cost of product £5 per kg,2. cost of solvent 20 p/kg,3. additional solvent make-up 10 kg/d,4. current loss of product 0.7 kg/h,5. anticipated recovery of product 80 per cent,6. additional service(utility) costs, negligible.Other operating costs will be insignificant.

Answer 1

Answer:

It is economical

Explanation:

Given data for determining

cost of product = £5 per kg

cost of solvent = £20 per /kg

additional solvent makeup = 10 kg/d

current loss of product = 0.7 kg/h

anticipated recovery of product = 80%

additional service ( utility cost ) = negligible

Determine if it is economical to install the recovery system

cost of product = £5 per kg

cost of solvent = £20 per /kg

additional solvent required = 10 kg / d

cost of additional solvent in a day  = £200 / day  ( £20 per kg * 10 kg / d )

product lost = 0.7 kg/h

product recovered = 0.7 * 80% = 0.56 kg/h

therefore product recovered in a day = 0.56 * 24 = 13.44 kg / day

Next :

calculate income generated from product recovery

13.44 kg/day *  £20 /kg =  £268.88 / day

Determine if it is economical

Income - cost

= £268.88 - £200

=  £68.88  ( hence it is economical )