Integrated Process Development

The aim of pollution prevention R&D is to modify processes or test alternate routes to minimize waste streams in the first place. For waste that is unavoidable, this goal involves integrating recovery or waste destruction into the process. In this procedure, the chemical engineer must evaluate the type and quality of the starting materials, the optimal recycling options, and improved treatment or elimination of process waste as a whole at the development stage. Thus for each process, optimum chemical and physical conditions must first be established in the laboratory and then at the pilot plant. The engineer must establish process balances and develop technologies for the optimal treatment of waste streams.

The decision tree approach (see Figure 3.6.10) relates a production plant and its waste streams, with emphasis on process safety. Integrated process development allows a dynamic search for the optimum process conditions by iterative use of the established tools of process chemists and engineers. The described approach for an environmentally sound chemical process applies to both individual process steps and complete, complex, multistage processes.

Figure 3.6.11 shows the process balances of letter acid production before and after the development work (Laing 1992). The upgraded process requires about sixty man-years' work for chemists, chemical engineers, and other engineers. The cost of the new plant is several hundred millions of dollars. Large production volumes, similarities in products, and the possibility of building a new plant at a new site facilitated a near perfect solution.

The following benefits were achieved:

Before

FIG. 3.6.10 Integrated process development.

Product for Sales

Product 1tn

Product 1tn

After

1.2tn t

Feed 7.5tn

SO2 (Liquid)

Processing

Solvent

Solid

Waste / 1.9tn J (Inorganic)

Crude Effluent 13.6cum Salts: 3.6tn Organic waste „ G.66tn

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