The market for EO, about 70% of which is converted to EG, is expected to grow at around 5% per year. In January 2016 there were 146 plants producing over 30 million t/y of EO equivalents. Since the EO derivatives market is highly competitive, low-cost producers are best positioned for long-term business strength. As well as low feedstock prices and large plant capacities, the application of best-available technology is also of key importance.
About the technology
Shell Global Solutions is one of the market’s leading EO/EG process licensors. Moreover, the Shell Group (“Shell”) is a major producer of EO and EG through its production facilities in Canada, China, the Netherlands, Singapore and the USA. Experience from own plant operations is used for continuous design upgrading. CRI Catalyst Company (CRI) is the leading EO catalyst producer and a pioneer in the industry. For more than 50 years, CRI and Shell have led the industry in improving the performance and lifespan of EO catalysts. Over 50% of the world’s current EO production is manufactured using a CRI EO catalyst.
Two versions of the Shell EO/EG process are licensed:
- the Shell MASTER process, which is based on catalytic conversion of ethylene to EO and thermal conversion of EO to EG; and
- the Shell OMEGA process, which is based on catalytic conversion of both ethylene to EO and EO to EG.
In the Shell MASTER process, EO and water are converted to glycols by thermal hydration in a tubular reactor. This process yields roughly 8–10% diethylene glycol (DEG) and triethylene glycol (TEG). The MEG yield depends on the amount of water used in the reaction. Excess water is removed by multiple-effect evaporation, and the individual glycol products are then recovered and purified by distillation.
In the Shell OMEGA process, EO is first reacted with carbon dioxide to form ethylene carbonate, which is then hydrolysed to MEG and carbon dioxide (Figure 1 overleaf). As EO is not present in the hydrolysis reaction, the co-production of DEG and heavier glycols is negligible. Both processes have the option to co-produce high-purity EO.
Both the Shell MASTER process and the Shell OMEGA process are based on and optimised around the use of state-of-the-art CRI EO catalysts with high selectivity and high stability that enable at least three years of operation between catalyst changes at an average catalyst selectivity of about 90%.
The Shell MASTER process co-produces DEG and TEG. The MEG yield is typically 90–92%, depending on customer requirements.
The Shell OMEGA process produces MEG only, and offers significant advantages compared with conventional processes. For instance, it:
- has a MEG selectivity in excess of 99%, which means that virtually no DEG or TEG is co-produced;
- produces superior quality MEG;
- uses about 20% less steam at equal EO selectivity; and
- produces about 30% less waste water.
In addition, a Shell OMEGA plant costs about 10% less to build for the same yield.
Since Shell started licensing its EO/EG technology in 1956, more than 70 Shell-designed EO/EG units were commissioned or are currently under construction.
The Shell OMEGA process was acclaimed in the prestigious IChemE Innovation and Excellence Awards 2008 by winning the Engineering Excellence Award.
Have you ever considered how you can
- Optimise your technology configuration to meet local market conditions?
- Achieve a fast and smooth start-up?
- Minimise the production of heavy-glycol by-products?
As every plant is tailor-made and tuned to customer wishes and local conditions and constraints, capital investment costs will vary from plant to plant. In 2004, the capital costs of a 600-kt/y MEG unit were estimated at $120–160 million for the inside-battery-limits portion, but construction and material prices have increased significantly since. After plant start-up, Shell and CRI will continue to provide operational support. Process design studies relating to plant modifications or debottlenecking can also be accommodated.