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A preliminary process design and economic analysis into the possible threat of ethylene- based acrylic acid manufacture is presented. Pipeline ethylene is fed at 14,000 ft2/hr to the first block of this process. The epoxidation of ethylene to ethylene oxide takes advantage of microchannel technology and eliminates the need for inerts, thus decreasing equipment sizing downstream while achieving a yield of 80% overall. The resulting ethylene oxide stream is carbonylated in a liquid phase, homogeneous reaction. The β-propiolactone is then rearranged in phosphoric acid to produce 37,000 lbs of acrylic acid per hour for a yearly rate of just over 300M pounds at greater than 99.4% mass purity. The product contains 300 ppm mono-methyl ether hydroquinone to prevent the product from polymerizing and entering the explosive limits.
Using an after tax discount rate of 15%, the NPV is -$50M in December, 2014, 35 years from construction start date. The IRR is 13.84% and confirms the notion that a microchannel costs need to be further evaluated to determine the profitability. In the project, the EO plant accounts for 90% of the equipment cost and 50% of the total invested capital cost.
A cost plus analysis of ethylene oxide costs was determined and IRR data was determined based on the variability of ethylene prices and the cost-plus price of producing ethylene oxide. It was determined that the project has an IRR of 42.17% with a NPV of $288M when an after tax cash flow analysis was conducted with an after tax discount rate of 15%.
It was concluded that the feasibility of this project depends heavily on the cost of the microchannel reactors, and at this stage, the costs of the microchannel do not outweigh the advantages offered by the new reactor. It is recommended that further analysis be done to more accurately cost the microchannel reactor and to investigate the benefits of increasing the per pass conversion of ethylene. Further analysis on the reactor designs and rates for the carbonylation step and rearrangement step could help hone in the reality of an ethylene based acrylic acid process. Most importantly, further economics should be conducted to see if the best-case scenario assumptions used in this paper are too ideal. The new economics should be compared to the sensitivity analysis conducted in this study.
Date Posted: 25 July 2014