scope:

Introduction

The chemical, food, petrochemical and pharmaceutical industries need to be able to control their processes to ensure safety and environmental compliance and to optimise operations for maximum profitability. The use of on-line process analysers is a valuable tool in helping to achieve these objectives because analysers provide frequent (continuous or cyclic) analytical information on key process properties. This allows continuous on-line optimisation of the plant and rapid identification and correction of off-spec or undesirable operating conditions. Analyser repeatability is also usually better than the laboratory reference method as it allows closer control and targeting to product specification.

The correct design and installation of on-line analysers are essential to achieve the full benefits from analyser systems. Analysers are expensive to install and maintain and should only be installed when there is a clearly defined and quantified benefit. On-line process analysers are usually justified for one or more of the following reasons:

• personnel and plant safety;

• pollution control, measurement and prevention;

• optimising plant operations for throughput and yield;

• control of final products as closely as possible to maintain specification and minimise product quality give-away;

• minimising product degradation and reprocessing costs in cases of plant upsets, change in mode of operation and start-ups;

• improving energy efficiency of boilers, distillation columns, furnaces and reactors; and

• corrosion control.