Multiproduct

In continuous processes, all those sources of process waste associated with start-up and shutdown also apply to product changeover in multiproduct plants. 

Eig. 15. Eurfural, phenols, and ethanol production from wood in a multiproduct process biomass chemical plant (52). Wood (qv) is ca 50% cellulose (qv),... 

Fig. 1. Abbreviated flow sheet of the multiproducts of Great Salt Lake Minerals Corporation.

Where multiproduct plants are produced using the same processing equipment. 

From diese various estimates, die total batch cycle time t(, is used in batch reactor design to determine die productivity of die reactor. Batch reactors are used in operations dial are small and when multiproducts are required. Pilot plant trials for sales samples in a new market development are carried out in batch reactors. Use of batch reactors can be seen in pharmaceutical, fine chemicals, biochemical, and dye industries. This is because multi-product, changeable demand often requues a single unit to be used in various production campaigns. However, batch reactors are seldom employed on an industrial scale for gas phase reactions. This is due to die limited quantity produced, aldiough batch reactors can be readily employed for kinetic studies of gas phase reactions. Figure 5-4 illustrates die performance equations for batch reactors. 

Rippin, D.W.T. (1983) Simulation of single and multiproduct batch chemical plants for optimal design and operation. Comput. Chem. Eng., 7 (3), 137-156. 

The typical factors to consider when pondering B2C will include size and scale of operation, use of existing equipment, flexibility for multiproduct operation, start-up and shutdown, cleaning frequency, inventory, validation, traceability of product with respect to raw materials, equipment design, and availability as well as operational experience [50]. 

Rajagopaian, D., and Karimi, I.A., Completion times in serial mixed-storage multiproduct processes with transfer and set-up times. Comput. Chem. Eng. 13(1/2), 175-186 (1989). 

Plants for the manufacture of fine chemicals are discussed in Chapter 7 with emphasis put on multiproduct plants. Types of production plants and typical equipment for multiproduct plants with cost considerations are presented in more detail. Problems of designing and scheduling multiproduct and multipurpose plants with particular emphasis given on process data needed to realise this task are discussed. 

The recommended ranges for impeller dimensions are given in Table 5.4-27. A high-efficiency turbine or four-bladed flat turbine with D/Dr as advised in Table 5.4-27 and C/D., equal to 0.75 seem to be the most versatile agitators in reactors for multiproduct plant. 

The fine chemicals business is characterized by a small volume of products manufactured. Therefore, batch production predominates and small-scale reactors are used. The need to implement fine chemistry processes into existing multiproduct plants often forces the choice of batch reactors. However, safety considerations may lead to the choice of continuous processing in spite of the small scale of operation. The inventory of hazardous materials must be kept low and this is achieved only in smaller continuous reactors. Thermal mnaways are less probable in continuous equipment as proven by statistics of accidents in the chemical industries. For short reaction times, continuous or semicontinuous operation is preferred. 

There are three basic types of plants for the manufacture of fine chemicals dedicated plants, multiproduct and multipurpose plants, and mixed plants. 

The makespan for multiproduct plants depends on the campaign arrangement. If the campaigns are carried out in series (product A,A,A. .. product B,B,B), the makespan is the sum of times required for all campaigns if time for cleaning between campaigns is negligible. 

There are numerous constraints and factors that affect procedures for design of multiproduct and multipurpose plants ... 

Combining equations (7.4-24)-(7.4-26) gives a system of non-linear equations that can be solved using iterative techniques. Savings in equipment costs as compared to initial guesses are approximately 30 %. The real savings will be lower because the optimal choices for equipment units are usually not available on the chemical equipment market. The standard sizes greater but nearest to the optimal sizes will be selected. The total cost for the standard equipment is very close to the minimum found. Robinson and Loonkar (1972) extended their procedure for multiproduct batch plants. 

A major problem to be solved for multiproduct plants is the occurrence of disparities in the cycle times and size requirements for the different stages. In the following it will be assumed that the size factors as well as the cycle times of all units are independent on equipment size. This assumption is usually relaxed in further stages of the design. In case of batch heating and cooling, or reactors operated in semi-continuous mode, this is necessary in order to adopt the cycle times to the capacity of equipment, which is related to batch size. 

Figure 7.4-10. Equipment. sizing (multiproduct plant, non-overlapping campaigns). 

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