Control of reactor temperature

Fig. 6. A primary means of regulating polyethylene chain length is through control of reactor temperature. Increasing the temperature enhances termination, probably by destabilizing the Cr-chain bond, resulting in shorter chains.

In the same manner as in hydrocracking (Dolbear, 1997), hydrogen is added at intermediate points in hydrodesulfurization reactors. This is important for control of reactor temperatures. The mechanical devices in the reactor, called reactor internals, which accomplish this step are very important to successful processes. If redistribution is not efficient, some areas of the catalyst bed will have more contact with the feedstock. This can lead to three levels of problems ... 

P, I, D system (Figure 9.10). This type of temperature control requires careful tuning of the control parameters, in order to avoid oscillations, which may lead to loss of control of reactor temperatures in cases where an exothermal reaction is carried out. The main advantage of the isothermal control is to give a smooth and reproducible reaction course, as long as the controller is well tuned. 

Fig. 3. The proposed strategy for on-line update and control of reactor temperature profile.

In this book, automatic control of reactor temperature is the most interesting target to this purpose, the manipulated variable is usually one (or a combination of) the following [3] ... 

The properties of the two species are very different in terms of their solubility, viscosity and detergency. The alkene sulphonate is the better performing surfactant and the manufacturing process is developed to maximise this more desirable product. The sulphonation process is significantly more exothermic than LAB sulphonation, requiring careful control of reactor temperatures and more dilute S03 which often results in lower reactor loadings and hence lower productivity, compared to LAB. Low product colours can be achieved but require very careful control of sulphonation, neutralisation and hydrolysis. Earlier processes relied heavily... 

Step 3. The open-loop instability of the reactor acts somewhat like a constraint, since closed-loop control of reactor temperature is required. By design, the exothermic reactor heat is removed via cooling water in the reactor and product condenser. We choose to control reactor temperature with reactor cooling water flow because of its direct effect. There are no process-to-process heat exchangers and no heat integration in this process. Disturbances can then be rejected to the plant utility system via cooling water or steam. 

Finally, the product obtained is separated from the distillation tower, such as gas product, light oil product and heavy oil product. Our target is light oil product and/or heavy oil product, which is generally obtained by control of reactor temperature and distillation system such as temperature gradient, reflux ratio and reboiler temperamre, etc. The distribution of the oil product must be decided by market circumstances. 

The catalyst was Rh on y-alumina in the form of particles with diameter of 0.1-0.3 mm. In some measurements, supported Pt or Pd were also utilized. The catalyst was packed in a specially designed, 8-mm i.d. tubular reactor, between two layers of inert material. A forced ventilation oven allowed control of reactor temperature. The expressions reactor inlet and reactor outlet adopted in the text to describe the reaction front motion, are referred to the catalyst bed only, without taking into account the inert layer. 

RgureSJI PID control of reactor temperature in a batch reactor. 

The naphthalene is vaporized, mixed with air, and fed to the top of the reactor. This process also allows for mixtures of ortho- s.yXen.e [95-47-6] to be mixed with the naphthalene and air, which permits the use of dual feedstocks. Both feedstocks are oxidized to phthaUc anhydride. The typical range of reactor temperature is 340—380°C. The reactor temperatures are controlled by an external molten salt. 

As mentioned before, the vast majority of accidents in batch processing arise when the control of the temperature of the reaction mixture is lost. This situation often leads to a temperature thermal) runaway, i.e. a temperature overshoot that can result in undesired reactions (decompositions), evaporation, or gas formation. As a consequence, pressure is built up inside a reactor and this can cau.se an explosion. The explosion is usually accompanied by damage to the equipment and release of hazardous (toxic, explosive, or flammable) species to the. surroundings. 

As shown in several of the simulation examples, the fact that Q is now a function of the flow rate, Fj, provides a convenient basis for the modelling of cooling effects, and control of the temperature of the reactor by regulation of the flow of coolant. 

An exothermic reaction involving two reactants is run in a semi-continuous reactor. The heat evolution can be controlled by varying the feed rate of one component. This is done with feedback control with reactor temperature... 

Figure 5.167. The feed rate of B, FB, was manipulated by the control equation to control the reactor temperature. At the end of the batch, when the reaction rate decreased due to decreasing CA, FB increased gradually to its maximum.

The diagram above shows an interactive MIMO system, where the controlled variables, outlet flow temperature and concentration, both depend on the manipulated variables. In order to design a decentralized control, a pairing of variables should be decided. A look at the state Eq.(23) suggests the assignment of the control of the temperature to the cooling flow and the concentration control to the reactor inlet flow. In this case, the internal variable Tj may be used to implement a cascade control of the reactor temperature. Nevertheless, a detailed study of the elements of the transfer matrix may recommend another option (see, for instance, [1]). 

Whatever the merits of each process in a continuous commercial operation, the slurry process is very convenient for batch polymerization studies in the laboratory. The diluent permits precise control of the temperature and serves to dissolve ethylene and other reactants that must contact the catalyst during polymerization. Most of the work reported here was done in a slurry reactor. 

Source Considerations. Many CVD sources, especially sources for or-ganometallic CVD, such as Ga(CH3)3 and Ga(C2H5)3, are liquids at near room temperatures, and they can be introduced readily into the reactor by bubbling a carrier gas through the liquid. In the absence of mass-transfer limitations, the partial pressure of the reactant in the gas stream leaving the bubbler is equal to the vapor pressure of the liquid source. Thus, liquid-vapor equilibrium calculations become necessary in estimating the inlet concentrations. For the MOCVD of compound-semiconductor alloys, the computations have also been used to establish limits on the control of bubbler temperature to maintain a constant inlet composition and, implicitly, a constant film composition (79). Similar gas-solid equilibrium considerations govern the use of solid sources such as In(CH3)3. 

Figu re 9.14 Principles of a cascade controller. The master controller controls the reactor temperature (Tr) the slave controls the cooling system temperature (Tc). 

This section presents the design of a controller to control the reactor temperature following a desired temperature tra-... 

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