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FIG. 3.10.2 Adding feed to a reactor. (a) This method results in poor mixing. (b) Inline static mixers improve reactor performance.

Product

Reactant A

Product

Reactant B

Solvent

Static Mixers

Solvent

Feed Stream

Recycling

Feed Stream

Reactor Product

FIG. 3.10.3 A separate, small reactor for recycling waste streams.

Examining Heating and Cooling Techniques

A company should examine the techniques for heating and cooling the reactor to avoid hot or cold spots in a fixed-bed reactor or overheated feed streams, both of which usually give unwanted by-products.

Providing Online Analysis

Online analysis and control of process parameters, raw material feed rates, or reaction conversion rates can significantly reduce by-products and waste.

Implementing Routine Calibration

Routine calibration of process measurement and control equipment can minimize inaccurate parameter set points and faulty control.

Upgrading Process Controls

Upgrading process parameter measurement and control equipment to ensure more accurate control within a narrow range can reduce process conditions that contribute to by-product formation.

Considering a Different Reactor Design

The classic stirred-tank, back-mix reactor is not necessarily the best choice. A plug reactor has the advantage that it can be staged and each stage can run at different conditions, with close control of the reaction for optimum product mix (minimum waste). Many hybrid innovative designs are possible.

formation. Converting a process from batch to continuous mode reduces this waste. This option may require modification of piping and equipment.

Optimizing Operating Procedures

This option includes investigating different ways of adding the reactant (e.g., slurry or solid powders), changing process conditions and avoiding the hydrolysis of raw materials to unwanted by-products, and using chemical emulsion breakers to improve organic-water separation in decanters. A common cause of by-product formation is a reaction time that is either too short or too long. In such cases, increasing or decreasing the feed rate can reduce byproducts. Optimization of the reactant ratio can reduce excess constituents that may be involved in side, by-product-forming reactions.

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