Ethylene oxide plant

Air-Based Direct Oxidation Process. A schematic flow diagram of the air-based ethylene oxide process is shown in Figure 2. Pubhshed information on the detailed evolution of commercial ethylene oxide processes is very scanty, and Figure 2 does not necessarily correspond to the actual equipment or process employed in any modem ethylene oxide plant. Precise information regarding process technology is proprietary. However, Figure 2 does illustrate all the saUent concepts involved in the manufacturing process. The process can be conveniently divided into three primary sections reaction system, oxide recovery, and oxide purification. 

One Dies in Union Carbide Ethylene Oxide Plant Explosion ... 

Figure 7-8. The ethylene oxide plant after the fire and explosioti. (Photo courtesy of BP Chemicals Limited.)...

An ethylene oxide plant tripped, and a light on the panel told the operator that the oxygen valve had closed. Because the plant was going to be restarted immediately, he did not close the hand-operated isolation valve as well. Before the plant could be restarted, an explosion occurred. The oxygen valve had not closed, and oxygen continued to enter the plant (Figure 14-5). 

Britton, L. G. 1990. Thermal Stability and Deflagration of Ethylene Oxide. Plant/Operations Progress, 9(2). 

There are two important methods for the manufacture of propylene oxide, each accounting for one half the total amount produced. The older method involves chlorohydrin formation from the reaction of propylene with chlorine water. Before 1969 this was the exclusive method. Unlike the analogous procedure for making ethylene oxide from ethylene, which now is obsolete, this method for propylene oxide is still economically competitive. Many old ethylene oxide plants have been converted to propylene oxide synthesis. 

As detailed below the basic sources of CO2 are natural gas processing plants, ethanol plants, ammonia plants, hydrogen plants and ethylene oxide plants. In addition, there are a variety of dilute sources, the largest category of which is power plants. As shown below, of the man-made sources, the largest is ammonia production approximately 1100 MCF (million standard cubic feet). 

The conventional route to ethylene oxide entails the direct vapor phase oxidation of ethylene. The reaction proceeds at 200-300°C and 10-30 atmospheres to produce ethylene oxide in 65-80 mole percent selectivity. The success of this technology is attributable to the development of fairly selective silver oxide catalysts which limit combustion of ethylene to CO, CO and water. The CO2 is present in the purge gas. Oxygen-based ethylene oxide plants produce approximately 60 MCF of CO2 per day. 

Until 1969, the only method for producing propylene oxide was the chlorohydrin process, using a technique similar to that used to synthesize ethylene oxide, and most of the production units were converted ethylene oxide plants. 

Improvements in the direct-oxidation route to ethylene oxide, contributing to reduced costs, have resulted in increased manufacturing capacity which now surpasses the chlorohydrin process capacity. By the direct-oxidation route, catalysts costs have been reported to be in the range 0.38-0.40 cents per pound ethylene oxide. Fixed-bed catalyst plants have been stated to attain yields of 55-65 per cent in commercial practice. Investment costs for large-scale direct-oxidation ethylene oxide plants have been reported to be 10-11 cents per annual pound of capacity. ... 

The cost of oxygen is largely dependent upon the capacity, pressure, and purity required. The exact oxygen requirements for a specific ethylene oxide plant design are dependent on the licensor s process, especially catalyst selectivity, as well as other site specific conditions. Nevertheless, Figure 4 can be used to estimate the oxygen plant capacity, purity, and pressure and thus its approximate cost. 

The capacity of a modern ethylene oxide plant is typically between 100 million and 550 million pounds per year. Table 3 shows the capital investments for both air-based and oxygen-based plants of 330 million pounds per year. When ethylene oxide is produced without ethylene glycol there is a slight increase in overall cost, primarily due to increased off-site costs. However, most ethylene oxide is produced as feed for ethylene glycol, so the cost estimate shown is based on an ethylene oxide plant where all of the product is used to produce ethylene glycol in a tandem glycol plant. 

An ethylene oxide plant at Chemische Werke Hills is illustrated in a review article on hydrocarbon oxidation by Broich 19). It is stated that ethylene oxidation is at 240-260° over a supported silver catalyst using 4 % ethylene and 7 % oxygen (added as air) with the balance inert gas. The pressure is 90-150 psig, conversion per pass is 34-40%, and selectivity to ethylene oxide about 60 mole %. The production rate is 300 gm of oxide per liter of catalyst per hour. 

Industrially important absorption processes are for example the removal of sour gases (CO2, H2S) from natural gas or synthesis gas, the removal of carbon dioxide in chemical plants such as ethylene oxide plants, the removal of SO2 from flue gas, or the absorption of CO2 in power plants (carbon capture and storage (CCS)), and so on. One has to distinguish physical and chemical absorption... 

A company that uses ethylene oxide as a raw material traditionally used to purchase it from a vendor. The material was shipped to the plant and stored in a large tank prior to use. A new manufacturing plant was built adjacent to the ethylene oxide plant, and it was received by pipeline, eliminating the need for storage and transportation of large quantities of the hazardous chemical (Orrell and Cryan, 1987). This approach minimized the intensity of possible hazard. 

Table 5.5.5 Fixed and variable costs of an ethylene oxide plant for a utilization degree of 100% (annual production rate of 1800001 in 2006) [data from Baerns et o/.(2006)].

Figure 5.5.5 Influence of degree of utilization on the production costs and revenues of an ethylene oxide plant (annual production rate of ISOOOOt) - a simplified diagram with a linear increase of variable costs with plant utilization. Adapted from Baerns etal. (2006).

Figure 6.12.2 Flow sheet of an ethylene oxide plant. Adapted from Moulijn et al. (2004).

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