ABSTRACT
Acetic anhydride ((CH3CO)2O) is an active solvent, colorless, and has a pungent odor. It is usually used in the manufacturing of cellulose acetate, filter tow, filament yarn, aspirines and can also act as a solvent for the preparation of organic materials. There is no acetic anhydride plant found in Indonesia, to comply the domestic demands, and  openly export opportunities, this accetic anhydride plant was designed with 100.000 tons/year capacity, with the requirement of raw materials are 89.895 tons/year of acetone and 64.974 tons/year of acetic acid. This plant will be built in Kawasan Industri Wijayakusuma, Mangkangwetan, Semarang, Jawa Tengah, in 2019, and operated in 2020. The plant will operate for 24 hours a day, in 330 days/year with a scheduled annual onemonth shut down for each year.
The formation of acetic anhydride by reacting acetone and acetic acid in ketene process can  occur in two type of processes, which the first is the formation of ketene by decomposing acetone at a temperature of 750 - 760ºC and a pressure of 1,5 atm in a plug flow reactor (PFR). This stage includes the preparation of raw materials, the formation of ketene, formation of acetic anhydride, purification phase and storage of the product. In addition of ketene compound, the decomposition of acetone is also producing methane, ethylene, and carbon monoxide as the by-products. In the second ones, the acetic anhydride gained from ketene gas with liquid acetic acid, this process occurred in a temperature of 55ºC and pressure of 1,5 atm in a packed reactive absorber. The purification stage can be done in a distillation column with 99,94% purity of the product.
Utilities of the plant consist : (i) a water supply unit (the water was supplied from a desalination of 144,71 m3/hour sea water), (ii) a steam supply unit for about 17.829,16 kg/hour), (iii) an electricity unit for about 19 MWh/day (772,28 kWh for plant usage and 18.227,72 kWh will be sold to PLN), (iv) a compressed air supply unit for about 15.004,60 m3/hour (61,75 m3 pneumatic usage and 14.942,85 m3 will act for air combustion), and (v) a fuel supply unit for about 21.150,72 kg methane for every start up. The plant is also equipped with a laboratory as maintain the quality of product and the protective equipments  providing the safety to the workers in accordance with the allowed standards.
The organization form of the plant is Perseroan Terbatas (PT), with line and staff  structure. This structure distributes  the workers into two systems : a shift and non-shift system.
An economic analysis resulted 87,34% before taxes Return on Investment (ROI) and 65,50% after taxes; 1,05 year before taxes Pay Out Time (POT) and 1,36 year after taxes; 52,06% Break Even Point (BEP); 43,82% Shut Down Point (SDP); and 29,52% Discounted Cash Flow (DCF). Based on this evaluation, the Acetic Anhydride Plant from Acetone and Acetic Acid in Ketene Process with 100.000 Tons/Year Capacity could be considered feasible to be established.