Materials or plans related to EO/EG pipeline construction

Currently, large-scale ethylene glycol production both domestically and internationally employs the direct hydration process, in which a large excess of water and ethylene oxide are used (water/EO mass ratio of 9/1) to carry out the reaction at temperatures of 150–200 °C and pressures of 0.8–2.0 MPa; the resulting product is an ethylene glycol aqueous solution with a mass fraction of about 14%. The world’s EO/EG production technologies are primarily monopolized by the United Kingdom, Shell in the Netherlands, and SD and UCC in the United States. The production capacity utilizing the technologies of these three companies accounts for over 90% of the total EO production capacity, with Shell providing only oxygen-based technology ； SD Company can provide two technologies: the air method and the oxygen method ； UCC Corporation possesses oxygen and air oxidation technologies, but they are used only in its own production facilities. In addition, the American company Dow Chemical, the Japanese company Catalyst, the German company Hurls, and the Italian company Sham also possess their own patented technologies. The process flows for EO/EG generally consist of main units such as the oxidation reaction of ethylene oxide, ethylene oxide recovery, carbon dioxide removal, ethylene oxide purification and storage, ethylene glycol hydration reaction, multi-effect evaporation and drying, and ethylene glycol purification and storage. The EO/EG process technologies and flow processes of Shell Company, SD Company, and UCC Company are essentially similar: ethylene and oxygen are used as raw materials, and under the presence of a silver catalyst, methane or nitrogen as stabilizers, and chloride inhibitors, ethylene is directly oxidized to EO. Subsequently, EO reacts with water in a certain molar ratio within a tubular reactor to produce EG. The EG solution is then evaporated to increase its concentration, dehydrated, and distilled to yield EG along with other diol by-products. In addition, the entire process is equipped with systems such as air separation units suited to its production capacity, carbonate treatment, and treatment of waste gases and liquids. The main differences in the patented technologies of the three companies lie in the catalysts, reaction and absorption processes, as well as certain technical details. The companies abroad that provide EO catalyst technology are mainly Shell, SD, UCC, and Nippon Catalyst. According to statistics, 50% of the silver catalysts used in the world are supplied by Shelf Corporation. SD Corporation and LTCC Corporation each account for 10% of the total demand for catalysts, while Catalyst Corporation accounts for 5%. In addition, Mitsubishi Oil Chemical Company, ICI Corporation, BASF Corporation, Dow Chemical Company, and Huels Company are also engaged in the development and production of catalysts. In the research and development of EG technology, certain techniques (such as EO catalytic hydration and the technology for producing EG from ethylene carbonate) have reached the final stages of development. In particular, the EO catalytic hydration technique has been applied in industrial EG production facilities with a capacity of 400 kt/year, and industrialization is expected to take place soon. As for the numerous technologies for the direct or indirect synthesis of EG using syngas as a raw material, they are still in the laboratory research stage and are far from industrial application.

Could you provide some information on the ease of manufacturing EO reactors?

The upper part of the reactor tubes is equipped with inert balls, which serve as a preheating zone to raise the temperature of the feed gas to the temperature required to initiate the reaction. The preheated circulating gas then enters the catalyst zone of the reactor tubes, where the reaction takes place. The recycle gas flow rate is maintained at a high level, resulting in only 10.5% of the ethylene being converted each time it passes through the reactor. The hot reactor outlet gas is rapidly cooled in the gas cooling section of the reactor/gas cooler, to prevent uncontrolled reactions (backburning) that may occur outside the reactor tubes. The hot reactor outlet gas passes through the tubes of the gas cooling section of the reactor/gas cooler, causing the water on the shell side to evaporate. Water circulates under the effect of thermal siphonage.