A mixture of benzene, air, and hydrochloric acid is fed to a reactor (R1) producing monochlorobenzene (MCB) as the primary product. The reactor operates continuously with a 20% conversion per pass of benzene, 5% of the benzene converted per pass combusts. The reactor isolates isothermally at 270°C. All reactants enter at the reactor temperature. The hot reactor products pass to a boiler wherein they are used to boil water to produce dry saturated steam at 100°C. This dry saturated steam is fed to a heat exchanger which preheats recycled hydrochloric acid (HCl) en route to R1. The cooled reactor products exit the boiler at 150°C and are immediately passed to a second heat exchanger. The reactor products are further cooled here to 60°C and are then discharged to a vented vessel which allows gases to exit the process. The remaining process liquid passes to a decanter. In the decanter, the organic and aqueous phases are separated. Both phases are sent to intermediate holding sections. The holding vessel which accommodates storage of the water, prior to use as a hydrolysis feed, incorporates an overflow system. The overflow system ultimately discharges to the drain. The organic liquid from the decanter passes to the extractor unit purposed with the recovery of phenol from liquid hydrochloric acid arriving pre-cooled (at 50°C) from the hydrolyzing unit. The organic liquid exiting the extractor passes to a distillation section which sequentially separates the constituents. The first unit, distillation column (K1), recovers the phenol product at 99 mol% purity. This product stream, which may be assumed to contain no benzene, is sent for further processing elsewhere in the plant. The top product from K1 passes to a second distillation column, wherein the binary mixture is separated producing two streams which are used as feedstock for the reactors. You may assume that the benzene composition of the top and bottom product streams produced by K2 are 98 mol% and 2 mol% respectively. The main MCB output from the distillation section is hydrolyzed in a second reactor which operates isothermally at 310°C with a 22% conversion per pass of MCB. You may assume that any benzene present in the feed passes through the reactor. The reactor products move to an ideal separator which fully recovers all unconverted MCB (at 99.9% purity), which is recycled to the reactor. This recycle operates with a small purge stream (r = 0.905) to prevent build-up of unwanted volatiles.
Additional Information:
The process operates continuously. The overall conversion of benzene within the process is 100%.
The process runs under steady state conditions. The levels in the buffer (holding) tanks do not change under normal operating conditions. All pressures are approximately 1 bar absolute. Benzene and hydrochloric acid (25 wt%) are available from separate storage facilities to feed the process as required. Process conditions are such that no HCl gas leaves the chlorination unit. Hydrogen gas does not appear in the process. Discharge to the water drain must not exceed 560 kg/hour. The molar feed ratio (steam/MCB) for the hydrolysis unit is 3:2. The R1 molar feed ratio (air/benzene) is 2:1. You may assume that the temperature of the liquid feed supplied to K1 is 90°C. K1 operates with a reflux ratio of 2.
Overview of main tasks to consider:
1. Construct a material balance for the process.
2. Perform energy balances for specified items within the process.
