Adiabatic reactor operation

This process takes place over Pt-10% Rh gauze in a catalyst and conditions essentially identical to that used for HNO3 synthesis in an atmospheric pressure adiabatic reactor operating at -1100°C with contact times of 1 msec. This process is the basis of HCN synthesis in Nylon and methylmethacrylate polymers. 

Except for adiabatic reactor operation, precise control of heat exchange is difficult. The local rate of heat exchange between the reactor and the surrounding and the local temperature are interrelated and depend on the fluid-dynamic conditions inside the reactor. 

The paper deals with the analysis of the dynamics of a system of two non-adiabatic reactors, operating in parallel. An effect of recycle degree and division of feedstock on generation of temperature-concentration chaotic oscillations in the system is investigated. 

Figure 28.4. ODH of ethane in an autothermal reactor in the presence of a BaMnAli 1O19 catalyst. Effect of ethane/02 feed ratio. Flow rate INL/min feed ethane/air pre-heat temperature 500 C. Dashed curves = calculated selectivity of ethylene and CO for a purely homogeneous adiabatic reactor, operating at the same inlet temperature and degree of reactant conversion. Adapted from Ref. 62. Copyright 2001 with permission from Elsevier.

Annable was the first to use the Temkin-Pyzhev equation to analyze operating data from industrial ammonia units [38] an adiabatic reactor operating at 245 atm and a multibed quench reactor operating at 300 atm. 

A detailed parametric study is undertaken in this chapter, using the full elliptic 2-D CFD code for both gas-phase and solid domains, in order to delineate the stable combustion regimes of propane-fueled catalytic microreactors at pressures 1 and 5 bar (pressures up to 5 bar are of interest to recuperated microturbine systems [1-3]), channel confinements 1.0 and 0.3 mm and wall thermal conductivities 2 and 16 W/mK. Methane simulations are also included, so as to exemplify the significant differences in both chemical and transport properties on microcombustor stability. The main objectives are to assess the effect of high pressure operation, molecular transport and gas-phase chemistry on the stability of propane-fueled catalytic microreactors and to study the impact of increased geometrical confinement and high wall thermal conductivity on the non-adiabatic reactor operation. Particular objectives were to quantify the differences between the two fuels in terms of reactor stability and performance. 

The most common approach to maintaining the desired reaction temperature is to operate with a significant excess of phenol in the reactor. An adiabatic reactor fed with 2 moles of phenol and 1 mole of isobutylene at 40°C would reach about 180°C if all the isobutylene formed PTBP. The selectivity towards the desired mono alkylphenol product almost always improves as the phenol to alkene mole ratio increases. These gains must be weighed... 

Adiabatic plug flow reactors operate under the condition that there is no heat input to the reactor (i.e., Q = 0). The heat released in the reaction is retained in the reaction mixture so that the temperature rise along the reactor parallels the extent of the conversion. Adiabatic operation is important in heterogeneous tubular reactors. 

Dr. Moeller I think to answer this question now is a bit difficult. It s just a mechanical problem of the maximum temperature the recycle compressor can handle. So, in the end, we will go to the inlet temperature to the compressor in the range of the inlet temperature to the reactor. So what we are endeavoring to attain is a simple reaction system consisting of an adiabatic reactor in series with waste heat boilers and nothing more than one recycle compressor. These compressors are used in the chemical industry with no problem in operation. So, in the end, you can go to hot recycle with an inlet compressor temperature the same as the inlet reactor temperature. All the heat from... 

A reactor is run adiabatically when no heat is exchanged between the reaction zone and the surroundings. The reaction temperature can then only be controlled by quenching with a cold stream of the reaction mixture or by inter-stage heat exchangers. For highly thermally sensitive large molecules treated in the fine chemicals sector this is a very impractical mode of operation. Therefore, adiabatic reactors will not be discussed here. 

ILLUSTRATION 10.3 ADIABATIC OPERATION OF CONTINUOUS STIRRED TANK REACTORS OPERATING IN SERIES... 

Keairns and Manning AIChE J., 15 (660), 1969] have used the reaction between sodium thiosulfate and hydrogen peroxide in a well-stirred flow reactor to check a computer simulation of adiabatic CSTR operation. Data on their experimental conditions and the reaction parameters are listed below. The reaction may be considered second-order in sodium thiosulfate. 

The computational effort required to carry out the design analysis is determined mainly by the magnitude and spatial distribution of the temperature variations that are taken into account. The maximum temperature difference between the inlet and outlet of the reactor occurs when the reactor operates adiabatically. In this case, heat transfer to the reactor wall is neglected so there is no temperature variation in the radial direction. However, the temperature does vary in the axial direction, so the material and energy balance equations are coupled through the dependence of the reaction rate on temperature. If the reactor is well insulated, and/or of large... 

The optimum steam/butene ratio in the feed for operation as a single adiabatic reactor. 

The estimated time required to achieve a fractional conversion of 0.99 is 1.80 h, and the temperature at this time is 333.5 K, if the reactor operates adiabatically. The fA(t) profile is given by the values listed in the second and last columns the T(t) profile is given by the third and last columns. 

The RC1 reactor system temperature control can be operated in three different modes isothermal (temperature of the reactor contents is constant), isoperibolic (temperature of the jacket is constant), or adiabatic (reactor contents temperature equals the jacket temperature). Critical operational parameters can then be evaluated under conditions comparable to those used in practice on a large scale, and relationships can be made relative to enthalpies of reaction, reaction rate constants, product purity, and physical properties. Such information is meaningful provided effective heat transfer exists. The heat generation rate, qr, resulting from the chemical reactions and/or physical characteristic changes of the reactor contents, is obtained from the transferred and accumulated heats as represented by Equation (3-17) ... 

In practice, large-scale reactors operate close to adiabatic conditions on loss of cooling which causes maximum increases in temperature. In smaller reactors, the temperature increase depends on the heating of coolant and reactor, and the heat loss to the reactor frame and confined coolant as well. 

A reversible reaction, At= B, takes place in a well-mixed tank reactor. This can be operated either batch-wise or continuously. It has a cooling jacket, which allows operation either isothermally or with a constant cooling water flowrate. Also without cooling it performs as an adiabatic reactor. In the simulation program the equilibrium constant can be set at a high value to give a first-order irreversible reaction. 

Although semi-analytical solutions are available in some cases [5], these are cumbersome and it is more usual to employ a numerical method. A simple example is presented below which illustrates the solution of the design equation for a batch reactor operated isothermally the adiabatic operation of the same system is then examined. 

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