Consider a privately owned retail business that sells metal accessories. The business receives approximately 250 Ibs of new merchandise every day. Since much of the merchandise sold must be matched to an old sample for verification, most customers bring their old merchandise into the store.
A number of customers leave their old parts behind to be disposed of by the business. It is estimated that about 20 percent of the total amount of metal sold is brought in and left by customers.
Of the amount of total merchandise received, approximately 9 percent of the weight is in packaging material (paper and cardboard). Eighty-seven percent of the packaging material is cardboard, of which 60 percent is recycled after the merchandise is unpacked. About 7 percent of the paper and 15 percent of the cardboard is sold with merchandise over the counter. The remaining paper and cardboard is disposed of in the dumpster.
The remaining weight of merchandise is metal parts and chemicals. Chemicals make up 11 percent of the total and all but 10 percent are sold daily. The remaining 10 percent is used within the business for cleaning equipment and is disposed ofas hazardous waste. Seventy-eight percent of the metal parts are sold per day with the remainder stored internally. Perform a mass balance and a flow diagram. (Courtesy of Paul Renter.)