Batch reactor control

The batch process is similar to the semibatch process except that most or all of the ingredients are added at the beginning of the reaction. Heat generation during a pure batch process makes reactor temperature control difficult, especially for high soHds latices. Seed, usually at 5—10% soHds, is routinely made via a batch process to produce a uniform particle-size distribution. Most kinetic studies and models are based on batch processes (69). 

Basic process control system (BPCS) loops are needed to control operating parameters like reactor temperature and pressure. This involves monitoring and manipulation of process variables. The batch process, however, is discontinuous. This adds a new dimension to batch control because of frequent start-ups and shutdowns. During these transient states, control-tuning parameters such as controller gain may have to be adjusted for optimum dynamic response. 

The pyrolysis of the plastics was carried out in a semi-batch reactor which was made of cylindrical stainless steel tube with 80mm in internal diameter and 135mm in height. A schematic diagram of the experimental apparatus is shown in Fig. 1, which includes the main reactor, temperature controller, agitator, condenser and analyzers. 

GL 13] [R 1] [P 12] By using a nickel plate, space-time yields up to 401 mol 1 h were achieved in the falling film micro reactor [6]. Control experiments in a batch reactor at a 30 min reaction time resulted in a space-time yield of only 1.3 mol 1 h , hence orders of magnitude smaller. By using an iron plate, space-time yields up to 346 mol h were achieved in the falling film micro reactor. 

Two simple forms of a batch reactor temperature control are possible, in which the reactor is either heated by a controlled supply of steam to the heating jacket, or cooled by a controlled flow of coolant (Fig. 3.18) Other control schemes would be to regulate the reactor flow rate or feed concentration, in order to maintain a given reaction rate (see simulation example SEMIEX). 

Apparatus. Since all the polymer modification reactions presented in this paper involved gas consumption, an automated gas consumption measuring system was designed, fabricated and used to keep constant pressure and record continuously the consumption of gas in a batch type laboratory scale reactor. Process control, data acquisition, and analysis was carried out using a personal computer (IBM) and an interface device (Lab-master, Tecmar Inc.). 

Cyanide oxidation consists of a reaction with sodium hypochlorite under alkaline conditions in either a batch or continuous system. A complete system includes reactors, sensors, controls, mixers, and... 

In pulp and paper processing, anthraquinone (AQ) accelerates the delignification of wood and improves liquor selectivity. The kinetics of the liquid-phase oxidation of anthracene (AN) to AQ with NO2 in acetic acid as solvent has been studied by Rodriguez and Tijero (1989) in a semibatch reactor (batch with respect to the liquid phase), under conditions such that the kinetics of the overall gas-liquid process is controlled by the rate of the liquid-phase reaction. This reaction proceeds through the formation of the intermediate compound anthrone (ANT) ... 

Area 200 control uses a batch controller. Each reactor is monitored and controlled separately. Level sensors and control valves meter the agent, energetics, or propellant along with sodium hydroxide into the empty reactor vessel. Fluid density is used to monitor and control the caustic concentration in the reactor vessel. 

All reactors, batch or flow, may be operated in three main ways in regard to temperature. These are isothermal, adiabatic and temperature-programmed. For the last, in a batch reactor the variation of temperature with time may be programmed, or in a fixed bed reactor the variation of temperature along the length of the bed may be controlled. 

The comparative experiments are carried out only in semi-batch operation mode the experimental conditions and the operation procedure are identical for both the SCISR and the STR, and the specific effective power inputs for the two reactors are controlled rigorously to be identical. 

In this section we discuss in a qualitative way the classical types of reactors batch, continuous stirred-tank reactor (CSTR), and plug flow reactor (PFR). Our purpose is to point out the features of each that impact the ease or difficulty of their temperature control. 

Several special features of a batch reactor impact control ... 

Mathematical models of batch reactors and control strategies are developed in Chapter 4. Both classical batch and fed-batch reactors are discussed using numerical examples. 

Hydrogenation reactions are frequently run in fed-batch reactors. The chemical component to be hydrogenated is charged to the reactor vessel. The hydrogen is then fed into the vessel on pressure control. The temperature of the reactor is controlled by manipulating the flowrate of coolant to the jacket, coil, or external heat exchanger. Thus this system has two manipulated variables (the flowrate of hydrogen and the flowrate of coolant) and two controlled variables (pressure and temperature). 

So it is important to vent off some vapor to get rid of the ethane, but not too much. The vent valve (AC) is split-range, so that it is closed when the pressure controller output signal is 83% of full scale. It is wide open when the controller output is at 0%. The sizing of the steam, chilled water, and vent valves is critical to the safe and efficient operation of this batch reactor. Figure 4.42 gives a sketch of the reactor, the controller, the setpoint generator, and the three control valves. 

In the present work, the objective was to develop and implement a control algorithm for addition of hydrolysate, based on the total gas flow from a pilot development unit (PDU)-scale reactor. The control algorithm was tested in fed-batch fermentations of dilute-acid hydrolysate made with two different yeast strains. 

Start up of a jacketed batch reactor requires control of the heat-up and cool-down rates. This involves determining and setting the jacket heat transfer fluid temperatures. An alternative is to make a trial heat-up and incorporate the results into a time-dependent heat transfer equation ... 

Emulsion Polymerization in a CSTR. Emulsion polymerization is usually carried out isothermally in batch or continuous stirred tank reactors. Temperature control is much easier than for bulk or solution polymerization because the small (. 5 Jim) polymer particles, which are the locus of reaction, are suspended in a continuous aqueous medium as shown in Figure 5. This complex, multiphase reactor also shows multiple steady states under isothermal conditions. Gerrens and coworkers at BASF seem to be the first to report these phenomena both computationally and experimentally. Figure 6 (taken from ref. (253)) plots the autocatalytic behavior of the reaction rate for styrene polymerization vs. monomer conversion in the reactor. The intersection... 

Semibatch Reactors Some of the reactants are loaded into the reactor, and the rest of the reactants are fed gradually. Alternatively, one reactant is loaded into the reactor, and the other reactant is fed continuously. Once the reactor is full, it may be operated in a batch mode to complete the reaction. Semibatch reactors are especially favored when there are large heat effects and heat-transfer capability is limited. Exothermic reactions may be slowed down and endothermic reactions controlled by limiting reactant concentration. In bioreactors, the reactant concentration may be limited to minimize toxicity. Other situations that may call for semibatch reactors include control of undesirable by-products or when one of the reactants is a gas of limited solubility that is fed continuously at the dissolution rate. 

The general characteristics of the main types of reactors—batch and continuous—are clear. Batch processes are suited to small production rates, to long reaction times, or to reactions where they may have superior selectivity, as in some polymerizations. They are conducted in tanks with stirring of the contents by internal impellers, gas bubbles, or pumparound. Temperature control is with internal surfaces or jackets, reflux condensers, or pumparound through an exchanger. 

The S88 approach to batch control provides a framework for the architecture of the system, having essentially four layers of control that operate on plant units (e.g., reactors, filters, driers) within a process cell (a collection of plant units within a facility or used for a process stage). 

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