Ethylene oxide operating pressure

In the glycol reactor (2), sufficient residence time is provided to react (noncatalytically) all of the ethylene oxide. Operating pressure of the reaction is controlled at a level that limits or avoids vaporization of ethylene oxide from the aqueous solution. 

Despite these precautions, an explosion occurred. One day, when ethylene oxide addition was started, the pressure in the reactor rose. This showed that the ethylene oxide was not reacting. The operator decided that perhaps the temperature point was reading low or perhaps a bit more heat was required to start the reaction, so he adjusted the trip setting and allowed the indicated temperature to rise to 200°C. Still the pressure did not fall. 

Figure 7-4. The Scientific Design Co. process for producing ethylene glycols from ethylene oxide (1) feed tank, (2) reactor, (3,4,5) multiple stage evaporators, 4 operates at lower pressure than 3, while 5 operates under vacuum, evaporated water is recycled to feed tank, (6) light ends stripper, (7,8) vacuum distillation columns.

Ethylene is currently converted to ethylene oxide with a selectivity of more than 80% under commercial conditions. Typical operating conditions are temperatures in the range 470 to 600 K with total pressures of 1 to 3 Mpa. In order to attain high selectivity to ethylene oxide (>80%), alkali promoters (e.g Rb or Cs) are added to the silver catalyst and ppm levels of chlorinated hydrocarbons (moderators) are added to the gas phase. Recently the addition of Re to the metal and of ppm levels of NOx to the gas phase has been found to further enhance the selectivity to ethylene oxide. 

At lower temperatures (260°C) higher operating pressures (5 bar) and high C2H4 to 02 ratios (Fig. 8.42) ethylene oxide formation and C02 formation both exhibit electrophobic behaviour over the entire Uwr range 47 Both rates vary by a factor of 200 as UWr is varied by 0.6 V (p varies between 3 and 0.015). The selectivity to ethylene oxide exhibits two local maxima 47 More interestingly, acetaldehyde appears as a new product47... 

Another study drew a comparison between the polymerisation of ethylene oxides and propylene oxides in similar operating conditions and in the presence of 10% of sodium hydroxide. When the polymerisation reached its maximum speed, the temperature reached 439°C for the former and 451 °C for the latter the pressures obtained are 44.6 and 26.6 bar respectively. 

Operation at too high pressure (e.g., acetylene, ethylene, ethylene oxide)... 

A continuous flow stirred reactor operates off the decomposition of gaseous ethylene oxide fuel. If the fuel injection temperature is 300 K, the volume of the reactor is 1500 cm3, and the operating pressure is 20 atm, calculate the maximum rate of heat evolution possible in the reactor. Assume that the ethylene oxide follows homogeneous first-order reaction kinetics and that values of the reaction rate constant k are... 

An ethylene oxide monopropellant rocket motor is considered part of a ram rocket power plant in which the turbulent exhaust of the rocket reacts with induced air in an afterburner. The exit area of the rocket motor is 8 cm2. After testing it is found that the afterburner length must be reduced by 42.3%. What size must the exit port of the new rocket be to accomplish this reduction with the same afterburner combustion efficiency The new rocket would operate at the same chamber pressure and area ratio. How many of the new rockets would be required to maintain the same level of thrust as the original power plant ... 

The nature of ethylene oxide and, to a lesser degree, the higher alkylene oxides, because of their high reactivity, flammability and explosion hazards mean that plants handling these reactants must be designed to eliminate all possible ignition sources. Reactions must be operated in inert conditions and have explosion pressure rated plant design [ 1-4]. 

Although thermodynamic calculations show that the pressure has no effect on conversion at the reaction temperatures, operations are conducted at,I to 3.106 Pa absolute to facilitate the subsequent absorption of ethylene oxide in water. Yield per pass reaches a maximum with increased-residence time, but, to maintain high selectivity, this is limited to between 1 and 4 s in industrial plants.. 

The aqueous solution rich in ethylene oxide is sent to purification. It passes through a stripping column, which operates under vacuum and separates the ethylene oxide at the top. The aqueous effluent leaving at the bottom is recycled to the absorption stage. It can be treated in an auxiliary unit to recover the glycol it contains. The top effluent which, in addition to carbon dioxide, contains acetaldehyde and hydrocarbon traces, is sent to two distillation columns in series, one for dehydration ( = 20 trays), and the second for purification (S 50 trays). These columns produce high-purity ethylene oxide with a very low acetaldehyde content. The product is stored in liquid form in tanks under nitrogen pressure. 

The improved process utilizes CO2 to extract ethylene oxide from water in a flow scheme which is similar to the other liquid extractions described previously. A block diagram in the patent depicts operation of the process. Ethylene oxidation and adsorption of the ethylene oxide in an absorber are carried out in the traditional manner, but the water stream from the absorber is then sent to a stripper where CO2 strip extracts the ethylene oxide from the water solution. The CO2 stream containing the ethylene oxide is lowered in pressure and sent to a high pressure distillation column called the ethylene oxide purifier. CO2 is vaporized, and as previously described throughout this book, vapor CO2 exhibits little dissolving power. Almost pure CO2 vapor is distilled and condensed in the column and a concentrated ethylene oxide stream containing some CO2 is obtained. 

---