Control of reactors

Slurry reactor Good control of reactor Expensive... 

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] ... 

Existing literature on the control of reactor-external heat-exchanger processes is relatively scarce, concerning mostly the implementation of linear (Ali and Alhumaizi 2000, Henderson and Cornejo 1989) and nonlinear (Dadebo et al. 1997) control structures on specific processes. These studies report several control challenges, including difficult tuning of PID and model-based controllers due to the ill-conditioning of the process model. 

Baldea, M. and Daoutidis, P. (2006). Model reduction and control of reactor-heat exchanger networks. J. Proc. Contr., 16, 265-274. 

The plantwide control structure is presented in Figure 7.11. The most interesting points are discussed below. Firstly, we fix the reactor-inlet flow rate and feed the fresh EDC on level control. Control of reactor and cooling section does not raise any problem. Since the HCl column operates mainly as a stripper, the temperature in the bottom is controlled by manipulating the steam rate, so as to ensure... 

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... 

So far we have dealt with control of reactors as isolated units. We now examine how reactors are controlled when they are part of an integrated plant. In principle, nothing new is introduced beyond the useful concepts involved in partial control. We can delineate among three cases ... 

The HDA reactor is unpacked and therefore cannot exhibit the wrongway behavior discussed in Chap. 4. However, it is quite common that gas phase reactions are carried out over a catalyst so it is important to understand the implications of the wrong-way behavior on the control of reactors with feed-effluent heat exchangers. 

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. 

Diluent and unreacted components are separated from the polymer, produced in the loop reactor, in a flash tank, thus the loop reactor and the gas-phase reactor are fully independent from each other. This enables easy control of reactor conditions and a wide product range. 

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. 

Excessively high temperature, over and above that for which the equipment was designed, can cause structural failure and initiate a disaster. High temperatures can arise from loss of control of reactors and heaters and, externally, from open fires. In the design of processes where high temperatures are a hazard, protection against high temperatures is provided by... 

Copolymer properties are known to be a function of the molecular weight distribution (MWD), the copolymer composition distribution (CCD) and in some cases the sequence length distribution (SLD). The optimal design, operation and control of reactors to produce high quality copolymers with efficient production rates requires ... 

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. 

Polymer properties such as molecular weight, molecular-weight distribution (MWD), crystallinity, and density are controlled through catalyst selection and control of reactor conditions Among the LLDPE processes, the gas-phase process has shown the greatest flexibility to produce resins over the full commercial range. 

Considering that aluminum trichloride is a very important commercial catalyst wifli over 25,000 tonnes produced annually in the USA alone, such hquids containing aluminum trichloride and allowing for differing levels of acidity have been extensively studied as first generation ionic catalytic solvents in a wide variety of synthetic and catalytic processes. Ionic liquids could therefore be used as substitutes for conventional solid or suspended sources of aluminum(III) chloride. As liquid phase catalysts, they allow for tremendous control of reactor inventories and can be cleaned and recycled with ease. Therefore, ionic liquids, in ideal cases, have no waste associated with them, whereas the supported alumi-num(III) chloride catalysts will require large (and annually rising) waste disposal costs. 

The RCCAs of a reactor control protection system (CPS) are the most important elements of the reactor maintenance safe operation, which ensure control of reactor core power level and fast reactor core transfer from initial condition to sub critical condition during the accident. Share of RCCA in fuel reloading cost is 1-1,2%. However for CR materials choice it is necessary to take into account a possibility of inexpensive RCCA recovery or disposal. 

RgureSJI PID control of reactor temperature in a batch reactor. 

Nowadays gamma-ray spectrometry is the most important tool for radio assay. Quality control in radionuclide production, control of reactor operation, surveillance of the environment, and radio activation analysis are only a few examples for the application of gamma-ray spectrometry. 

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