Industrial ethylene reactor

Tarafder, A., Lee, B., Ray, A. K. and Rangaiah, G. P. (2005a). Multi-objective optimization of an industrial ethylene reactor using a Non-dominated sorting genetic algorithm. Industrial and Engineering Chemistry Research, 44, pp. 124-141. 

An important application of this approach is the radical polymerization of ethylene at high pressure. In101 an attempt is made to model a process which takes place in an industrial mixing reactor. It appears that by solving an inverse kinetic problem, the researchers have verified the pre-exponential factors and the E values for a series of elementary stages, although what these stages are is not mentioned in the paper. 

Figure 1. Simulation of an industrial ethylene epoxidation reactor tube.

Comelio AA. Dynamic modelling of an industrial ethylene oxide reactor. Indian Chemical Engineer. Section A 2006 48 164-177. 

Union Carbide Corp. also uses a siUca-supported chromium catalyst in their extremely low cost Unipol gas-phase linear low density ethylene copolymer process, which revolutionized the industry when it was introduced in 1977 (86—88). The productivity of this catalyst is 10 —10 kg polymer/kg transition metal contained in the catalyst. By 1990, the capacity of Unipol linear low density polyethylene reactors was sufficient to supply 25% of the world s total demand for polyethylene. 

Vinyl chloride is made from ethylene and chlorine with Cu and K chlorides. The Stauffer process employs 3 multitubular reactors in series with 25 mm (0.082 ft) ID tubes (Naworski and Velez, in Leach, ed.. Applied Industrial Catalysis, vol. 1, Academic Press, 1983, p. 251). 

The effect of physical processes on reactor performance is more complex than for two-phase systems because both gas-liquid and liquid-solid interphase transport effects may be coupled with the intrinsic rate. The most common types of three-phase reactors are the slurry and trickle-bed reactors. These have found wide applications in the petroleum industry. A slurry reactor is a multi-phase flow reactor in which the reactant gas is bubbled through a solution containing solid catalyst particles. The reactor may operate continuously as a steady flow system with respect to both gas and liquid phases. Alternatively, a fixed charge of liquid is initially added to the stirred vessel, and the gas is continuously added such that the reactor is batch with respect to the liquid phase. This method is used in some hydrogenation reactions such as hydrogenation of oils in a slurry of nickel catalyst particles. Figure 4-15 shows a slurry-type reactor used for polymerization of ethylene in a sluiTy of solid catalyst particles in a solvent of cyclohexane. 

However, these investigations also point out that we need a proper definition of space-time yields for micro reactors. This refers to defining what essentially the reaction volume of a micro reactor is. Here, different definitions lead to varying values of the respective space-time yields. Following another definition of this parameter for ethylene oxide formation, a value of only 0.13 t h m is obtained -still within the industrial window [159, 162, 163]. 

Industrial reactors work below or above the explosion regime, hence operahon cannot be carried out at any ethylene-to-oxygen raho (see original citations in [43]). 

The very promising results for ethylene oxide synthesis by micro-channel processing given above shll await industrial implementation. Selechvity needs to be further improved above 80%, as the costs for ethylene contribute 80% to the overall process costs ]4]. In addihon to the costs argument, the usual requirements for transfer from laboratory to industrial scale will face the micro reactor reliability, proper process control and much more. 

Mixtures of aqueous sodium hypochlorite (presumably the 15% available chlorine commercial product) and ethylene glycol were observed to erupt violently after an induction period of 4 to 8 minutes. Caution is advised in view of the use of glycol as a cooling fluid in industrial reactors. 

Quite new ideas for the reactor design of aqueous multiphase fluid/fluid reactions have been reported by researchers from Oxeno. In packed tubular reactors and under unconventional reaction conditions they observed very high space-time yields which increased the rate compared with conventional operation by a factor of 10 due to a combination of mass transfer area and kinetics [29]. Thus the old question of aqueous-biphase hydroformylation "Where does the reaction takes place " - i.e., at the interphase or the bulk of the liquid phase [23,56h] - is again questionable, at least under the conditions (packed tubular reactors, other hydrodynamic conditions, in mini plants, and in the unusual,and costly presence of ethylene glycol) and not in harsh industrial operation. The considerable reduction of the laminar boundary layer in highly loaded packed tubular reactors increases the mass transfer coefficients, thus Oxeno claim the successful hydroformylation of 1-octene [25a,26,29c,49a,49e,58d,58f], The search for a new reactor design may also include operation in microreactors [59]. 

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