Accident Report
Continuous stirred tank reactor models
Dr. M.J. Willis Dept. of Chemical and Process Engineering, University of Newcastle. e-mail: Tel. Written: Updated: mark.willis@ncl.ac.uk 0191 222 7242 November, 1998 April, 1999; March, 2000
Aims and objectives
Chemical reactors are the most influential and therefore important units that a chemical engineer will encounter. To ensure the successful operation of a continuous stirred tank reactor (CSTR) it is necessary to understand their dynamic characteristics. A good understanding will ultimately enable effective control systems design. The aim of these notes is to introduce some basic concepts of chemical reaction systems modelling and develop simulation models for CSTR's . Non-linear and linear systems descriptions are derived.
Introduction
To describe the dynamic behaviour of a CSTR mass, component and energy balance equations must be developed. This requires an understanding of the functional expressions that describe chemical reaction. A reaction will create new components while simultaneously reducing reactant concentrations. The reaction may give off heat or my require energy to proceed. The mass balance (typical units, kg/s) Without reaction, the basic mass balance expression for a system (e.g tank) is written: Rate of mass flow in – Rate of mass flow out = Rate of change of mass within system Writing the mass balance expression for a stirred tank Consider a well-mixed tank of liquid (figure 1). The inlet stream flow is Fin (m3/s) with density ρin (kg/m3). The volume of the liquid in the tank is V (m3) with constant density ρ (kg/m3). The flow leaving the tank is F (m3/s) with liquid density ρ (kg/m3).
Table 1 summarises each term that appears in the mass balance.
Figure 1. Mixed Tank of Liquid
Rate of mass flow in inlet flowrate × density
Rate of mass flow out exit flowrate × density
Rate of change of mass within system
d(volume × density) dt d(Vρ ) Finρin Fρ dt Table 1. The terms in the
Dr. M.J. Willis Dept. of Chemical and Process Engineering, University of Newcastle. e-mail: Tel. Written: Updated: mark.willis@ncl.ac.uk 0191 222 7242 November, 1998 April, 1999; March, 2000
Aims and objectives
Chemical reactors are the most influential and therefore important units that a chemical engineer will encounter. To ensure the successful operation of a continuous stirred tank reactor (CSTR) it is necessary to understand their dynamic characteristics. A good understanding will ultimately enable effective control systems design. The aim of these notes is to introduce some basic concepts of chemical reaction systems modelling and develop simulation models for CSTR's . Non-linear and linear systems descriptions are derived.
Introduction
To describe the dynamic behaviour of a CSTR mass, component and energy balance equations must be developed. This requires an understanding of the functional expressions that describe chemical reaction. A reaction will create new components while simultaneously reducing reactant concentrations. The reaction may give off heat or my require energy to proceed. The mass balance (typical units, kg/s) Without reaction, the basic mass balance expression for a system (e.g tank) is written: Rate of mass flow in – Rate of mass flow out = Rate of change of mass within system Writing the mass balance expression for a stirred tank Consider a well-mixed tank of liquid (figure 1). The inlet stream flow is Fin (m3/s) with density ρin (kg/m3). The volume of the liquid in the tank is V (m3) with constant density ρ (kg/m3). The flow leaving the tank is F (m3/s) with liquid density ρ (kg/m3).
Table 1 summarises each term that appears in the mass balance.
Figure 1. Mixed Tank of Liquid
Rate of mass flow in inlet flowrate × density
Rate of mass flow out exit flowrate × density
Rate of change of mass within system
d(volume × density) dt d(Vρ ) Finρin Fρ dt Table 1. The terms in the