Date of this Version
This project explores the plant-scale process design and economic viability of production of ethylene glycol using a patented direct route from cellulose. Switchgrass was selected as the source of cellulose because it is a low-cost, non-feedstock plant capable of growing under a variety of conditions. The plant is designed to produce 100 million pounds of 99.5 % pure ethylene glycol which is the required purity for ethylene glycol used in plastic bottle production. The project is environmentally friendly and meets the Federal and state emission regulations.
The process design consists of three major components: pre-treatment, reaction and separation. In the pre-treatment stage, the switchgrass is ground and cellulose is extracted using highly dilute base. The reaction occurs in water solvent under 5 MPa of hydrogen in a fixed bed catalytic reactor with a retention time of 30 minutes. The ethylene glycol product is separated from the solvent and byproducts by flash vessels and column distillation in order to attain 99.5 % purity. A side product, propylene glycol, is also produced at 99.5 % purity and is separated in a similar fashion.
For the economic analysis, the plant was assumed to be located in Tennessee (near the Gulf Coast) where switchgrass is readily available. The total capital investment is $349,000,000, including a working capital of $7,747,000. The process is sensitive to the amount of solvent used. In the base case scenario using the same amount of solvent as used in the patent with ethylene glycol priced at $0.50/lb, propylene glycol byproduct priced at $0.78/lb, switchgrass priced at $50/dry ton, hydrogen priced at $1.00/lb, and catalyst priced at $5.08/lb, the net present value (NPV) of the project is negative $565,500,000 based on an interest rate of 15%, and the investor’s rate of return (IRR) is negative. The process is not profitable under the current conditions but may become profitable with advances in technology as described by the sensitivity analysis section of the report. Although the current version of the process is unprofitable, it is expect that the further development of the technology described in the referenced patent will allow for profitable future versions of this process, and it is recommended by the design team that the management retain this report for future reference
Date Posted: 20 August 2012