Batch chemical reactor

A batch chemical reactor contains 10,000 kg of reacting liquid material. A relief device must be properly sized for a potential runaway reaction. 

The CSB survey identified examples of modified or hybrid techniques to identify reactive hazard scenarios and ensure the implementation of adequate safeguards. For example, companies conducting reactions in batch chemical reactors often conduct HAZOP studies by evaluating deviations from... 

Company D is a large pharmaceutical manufacturer with worldwide operations. CSB staff visited a pilot-plant facility and thermal hazards laboratory. Pilot-plant operations included the use of several batch chemical reactors. Like Company A, this company also frequently changes chemicals handled and manufacturing techniques. 

Toulouse, C., Cezerac, J., Cabassud, M., Lann, M.V.L. and Casamatta, G. (1996) Optimization and scale-up of batch chemical reactors impact of safety constraints. Chemical Engineering Science, 51 (10), 2243-52. 

Therefore, the analysis of the main object of this book, namely, the batch chemical reactor, can start by considering the different ideal chemical reactors. In fact, ideal reactors are strongly simplified models of real chemical reactors [10], which however capture the two major features mentioned above. These models can be classified according to the mode of operation (i.e., discontinuous vs. continuous) and to the quality of mixing (i.e., perfect mixing vs. no mixing). The three resulting ideal reactors are sketched in Fig. 2.1. 

F. Strozzi and J.M. Zaldfvar. Thermal stability of batch chemical reactors by sensitivity calculation based on Lyapunov exponents. Chemical Engineering Science, 49 2681-2688, 1994. 

J. Alvarez-Ramirez and J. Alvarez. Robust temperature control for batch chemical reactors. Chemical Engineering Science, 60 7108-7120, 2005. 

Batch processes are often nonisothermal and characterized by nonlinear dynamics, whose effects are further emphasized by intrinsically unsteady operating conditions. Hence, methodological and technological problems related to batch chemical reactors are often very challenging and require contributions from different disciplines (chemistry, chemical engineering, control engineering, measurement, and sensing). 

Davidson, R. S. (1989). Using process information to control a multipurpose batch chemical reactor. Computs Chem. Eng., 13(1 /2), 83-84. 

Engineers develop mathematical models to describe processes of interest to them. For example, the process of converting a reactant A to a product B in a batch chemical reactor can be described by a first order, ordinary differential equation with a known initial condition. This type of model is often referred to as an initial value problem (IVP), because the initial conditions of the dependent variables must be known to determine how the dependent variables change with time. In this chapter, we will describe how one can obtain analytical and numerical solutions for linear IVPs and numerical solutions for nonlinear IVPs. 

J. B. Rawlings, N. F. Jerome, J. W. Hamer, and T. M. Bruemmer. End- point control In semi-batch chemical reactors. In Proceedings of the IFAC Symposium on Dynamics and Control of Chemical Reactors,. Distillation Columns, and Batch Processes, pages 323-328,1989. 

Consider another example of a component interaction accident that occurred in a batch chemical reactor in England [103]. The design of this system is shown in figure 2.1. The computer was responsible for controlling the flow of catalyst into the reactor and also the flow of water into the reflux condenser to cool off the reaction. Additionally, sensor inputs to the computer were supposed to warn of any problems in various parts of the plant. The programmers were told that if a fault occurred in the plant, they were to leave all controlled variables as they were and to sound an alarm. 

Accidents hke the Mars Polar Lander or the British batch chemical reactor losses, where the cause lies in dysfunctional interactions of non-failing, reliable components—i.e., the problem is in the overaU system design—illustrate reliable components in an unsafe system. There can also be safe systems with unreliable components if the system is designed and operated so that component failures do not create hazardous system states. Design techniques to prevent accidents are described in chapter 16 of Safeware. One obvious example is systems that are fail-safe, that is, they are designed to fail into a safe state. 

In the Mars Polar Lander loss, the software requirements did not include information about the potential for the landing leg sensors to generate noise or, alternatively, to ignore any inputs from the sensors while the spacecraft was more than forty meters above the planet surface. In the batch chemical reactor accident, the software engineers were never told to open the water valve before the catalyst valve and apparently thought the ordering was therefore irrelevant. 

The new model of accidents introduced in part II of this book incorporates the basic systems theory idea of hierarchical levels, where constraints or lack of constraints at the higher levels control or allow lower-level behavior. Safety is treated as an emergent property at each of these levels. Safety depends on the enforcement of constraints on the behavior of the components in the system, including constraints on their potential interactions. Safety in the batch chemical reactor in the previous chapter, for example, depends on the enforcement of a constraint on the relationship between the state of the catalyst valve and the water valve. 

In the batch chemical reactor accident described in chapter 2, one safety constraint is a hmitation on the temperature of the contents of the reactor. 

Figure 20.8 Utilities subsystem for a batch chemical reactor.

This example involves a two-stage Jacketed exothermic batch chemical reactor based on a model published by Luyben (1990). The reaction system involves two consecutive... 

With regard to batch processes which must be started up several times a day, this problem is serious. Particularly demanding is temperature control of a batch chemical reactor, where overshoot is intolerable. The situation can be improved to some degree with a controller whose derivative acts upon the input. Many new controllers incorporate this feature. 

A batch chemical reactor is to be brought up to operating temperature with a dual-mode system. Full controller output supplies heat through a hot-water valve, while zero output opens a cold-mater valve fully at 50 percent output, both valves are closed. While full heating is applied, the temperature of the batch rises at, IT/min the time constant of the jacket is estimated at 3 min, and the total dead time of the system is 2 min. The normal load is equivalent to 30 percent, of controller output. Estimate the required values for the three adjustments in the optimal switching program. 

Run-to-run control is particularly useful to compensate for processes where the controlled variable drifts over time. For example, in a chemical vapor deposition process or in a batch chemical reactor, the reactor walls may become fouled due to byproduct deposition. This slow drift in the reactor chamber condition requires occasional changes to the batch recipe in order to ensure that the controlled variables remain on-target. Eventually, the reactor chamber must be cleaned to remove the wall deposits, effectively causing a step... 

Figure 4.7 Dynamic concentrations of species in a batch chemical reactor (A + B C, C + B D).

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