Page 31 - Microsoft Word - Sulfo and Sulfa 1.doc

Sulfonation Plant Control

A typical sulfonation plant control system consists of two components that are integrated
into a single system: A main instrument control panel (ICP) and a motor control center
(MCC). When properly designed and installed, this system not only allows operation of
the sulfonation plant but also improves the operators' understanding of the plant's
operation through graphic interfaces. Better control results in improved product
consistency and quality.

The ICP integrates the loop control, logic control, data acquisition, and operator interface
into a single system. The functions include: analog control or PID control loops;
discrete control, e.g., to automatically sequence valves in the air dryers, and when
diverting gas from the sulfonator to the SO absorber; interlocks to reduce operator errors
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that could result in damage to the equipment or environmental releases; alarm
monitoring; and recipes that automatically enter variables used to calculate set points for
organic feed and the neutralizer raw materials.

The hardware can be as simple as individual electronic controllers or as complicated as
integrated, plant-wide distributed control systems. Naturally, more complex and
expensive control systems allow more control functions and permit data logging. They
also reduce the dependence on operator knowledge to produce top quality products.

As a cost effective option which allows maximum control at minimum cost, many
sulfonation plants employ a PLC-based control system in which the operator interaction
is accomplished by at least two, redundant PC-based workstations. These workstations
connect directly to the controllers and supply the operator with information necessary to
operate the plant. Normally a graphic display package is included in the control system
software. It shows graphic representations resembling a Process & Instrumentation
Diagram, which displays the main operating variables and indicates which motors are
operating. Typical displays include: sulfur metering system; air dryer system; SO gas
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generator system; sulfonator system; neutralizer system; and effluent gas treatment
system. The system is also capable of trending selected variables, logging alarms and
collecting data for historical logs.

The motor control center (MCC) includes a main power disconnect, a lighting
transformer, motor starters, variable frequency speed controllers, and disconnects as
required for the equipment.

Page 30 of 36 © 1997 The Chemithon Corporation