Executive Summary

          In the design of a new acrylic acid facility, the current process was examined for potential improvements. The current process reactor operates at 310 ⁰C and uses a cooling loop to quench the reactor effluent to 40 ⁰C. The reactor duty of 83849 MJ/h is removed from the salt loop by cooling water in E-301. The feed to the reactor is being heated by LPS to 191 ⁰C.

          The new process unit will use less propylene feed by decreasing the reactor temperature to 290 ⁰C. The conventional process feeds 127 kmol/h of propylene, the improved design requires only 117.5 kmol/h. The improved design also feeds 275 kmol/h of LPS, a decrease of 717 kmol/h from the conventional feed of 992 kmol/h. These feed changes result in a savings of over $2 million per year. The steam added pre-heats the reactor feed to 163 ⁰C in the new design. These feeds correspond to the minimum steam required by the new catalyst available (require only 1 kg steam per kg propylene). If coking reactions are observed in the new reactor, the steam feed may need to be increased to further dilute the reactants. It is important to see how this new catalyst will behave in an industrial environment.

          The conventional cooling water heat exchanger in the salt loop should be replaced with a waste heat boiler (WHB) with an area of 361 m². This new exchanger will produce 34.47 tonne/h of LPS at an annual profit of $2.1 million. The cooling loop used to quench the reactor effluent should be replaced with a process water jet injector system that adds 1.80 tonne/h of process water at 25 ⁰C to quench the effluent to 193 ⁰C. An added exchanger E-302 the produces 0.55 tonne/h of LPS from this stream at an annual profit of $34,000.

          A flash vessel is then used to send excess gas to the gas adsorption unit, T-301. The flash vessel (V-301) operates at 400 kPa and 55 ⁰C. The acid distillation column (T-302) should operate at a top pressure of 6.5 kPa and an optimum reflux rate of 60 kmol/h with the feed onto stage nine of a total of 31 stages. These changes help reduce the condenser duty from 4920 MJ/h to 2726 MJ/h. The reboiler duty is decreased from 4872 MJ/h to 2679 MJ/h.

          These process changes result in a NPV of $211 million after 10 years of production. This is an improvement of $54 million over the current NPV of $157 million. The new plant will have a DCFROR of nearly 54% compared with a DCFROR of 36% with the current plant.

Letter of Transmittal
Executive Summary
Introduciton
Results
Discussion
Conclusions
Recommendations
References