Ingeneiria Quimica

3
Chemical Reactor Control
Azzouzi Messaouda1 and Popescu Dumitru2
1Ziane

Achour University of Djelfa
University of Bucharest
1Algeria
2Romania

2Politehnica

1. Introduction
The principal technological element of the industrial plants and the chemical reactions is the
chemical reactor. In this chapter, it is considered that the chemical reactor is an apparatus in
which thechemical process can be effectuated to obtain certain substances in technological
process. The automatic control systems by their dynamic bring those processes to a point
where the profile is optimal, a fact which imposes several methods to achieve the desired
performances. This chapter proposes a hierarchical configuration of control which treats
aspects related to the primary processing of data,processes identification, control and the
robustness analysis under some conditions of the operating regime for representative plants
in the chemical and petrochemical industry. It is a design of numerical control laws in a
pyrolysis reactor in order to achieve an efficient regime of operation that allows as much as
possible to optimize the concentration of produced ethylene by the chemicalreactions
(Popescu et al., 2006a; Landau & Zito, 2006).

2. Technologic overview of the plant
2.1 Technical description and operating conditions
The pyrolysis reactor as shown in figure (1) is planted in petrochemical plants and is
intended to obtain ethylene, the combination of a quantity of gas with water under certain
operative conditions can produce a chemical reaction, which has theethylene as a result
among the reaction products (Popescu et al., 2006b).
The block diagram shown in figure (1) describes the chemical transformations selected from
a petrochemical plant whose pyrolysis took a large space. The kinetic parameters of
reactions are determined by the mathematical adjustment to the experimental results
obtained in several scientific resources in the combined model inthe simplification of the oil
and on its derivatives (Mellol, 2004).
2.2 Automation solutions of the reactor
Gas and steam are introduced to the plant of two access roads at a constant flow, but the
amount of the necessary heat for the reaction is obtained from a heating system which uses

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Petrochemicals

Fig. 1. Integration of Pyrolysis reactor into apetrochemical plant
Where
PR: pyrolysis reactor
MR: Membrane reactor
RR: Reforming reactor
CR: Catalytic reactor
a straight fuel powered methane gas (Harriott, 2002). For the insurance of the desired
operation of the reactor, it is necessary to achieve an automation mechanism that provides a
measurement system, automatic control and supervision of the parameters I/O, the
automation solution isshown in figure (2), which there are implemented the four controllers:
Data were recorded using an acquisition card connected to a computer (Azzouzi, 2008).
Variables are limited in technological point of view such as:
x1: flow of primary matter (oil) (1000 to 1600 Nm3/h)
x2: flow of steam (430-540 Nm3/h)
x3: working pressure (3.2-4.5 atm)
x4: working temperature (820-860oC)
y (%): theconcentration of the useful product (ethylene) at the reactor output
2.2.1 Flow control
Automatic systems of flow control structure are made of simple adjustment depending on
the error, such a structure is used only to maintain a flow to a specified value or as a
secondary loop in a control structure that changes in cascade the flow with the level or
concentration (Borne et al., 1993).www.intechopen.com

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Chemical Reactor Control

Fig. 2. Controller loops that govern the pyrolysis reactor.
L
D
F

ΔP
FC

Fo
Fig. 3. Flow controller
Where:
R : radius of pipe
L: length de pipe
F : flow of fluid
F0: intial value of flow
∆P: pressure reduction by restriction
: flow coefficient
: density of fluid
kp: amplification factor, kp=0.5
V
pa: delay constant of channel,...