Size of Unit Operations

The term process intensification is used synonymously with minimization. Process intensification is also often used more specifically to describe new technologies which reduce the size of unit operations equipment, particularly reactors. Innovative process intensification techniques are receiving more and more attention. Interesting possibilities for a range of unit operations, including reaction, gas-liq-... 

Microreactors evolved from the process intensification concepts and microfabrication techniques developed for the microelectronics industry. Process intensification was pioneered in the 1970s, arguably by Imperial Chemical Industries (ICI) researcher Colin Ramshaw, who began developing technologies and approaches that considerably reduced the physical size of unit operations while maintaining their... 

Design alternatives. For each alternative identified at the point 1 the procedure should be repeated and alternatives ranked. The generation of a "base-case" is recommended, against which the other alternatives can be evaluated. Design modifications may concern the (re)sizing of unit operations, and alternative flowsheet (recycle) structures. 

Fig. 1. Ink removal effectiveness of unit operations as a function of ink particle size (a) particle size distribution ia pulper (b) unit removal efficiency (4).

The applieation of a PHA to a proeess may involve the use of different methodologies for various parts of the proeess. For example, a proeess involving a series of unit operations of varying sizes, eomplexi-ties, and ages may use different methodologies and team members for eaeh operation. Then the eonehisions ean be integrated into one final study and evaluation. 

We need to develop a systematic approach to analyzing the impact of making changes in the cormections between process units or in the size of units that are undertaken to improve operating costs, plant flexibihty, or safety. 

The use of recombinant bST does not reduce GHG emissions but increases milk production so that the calculated emissions/unit of milk produced is reduced (Baumann, 1992). Capper et ah (2008) evaluated the environmental impact of using bST in a conventional dairying system and reported reductions in CH4 emissions of 8.3%. 15.2% of the total of small (<100 cows), medium (100 < cows < 500), and large farm operations (cows > 500) surveyed in the United States used bST on 17.2% of the cows (USDA, 2007). The use of bST increased with the size of the operation, with 9.1% of small farms using bST and 42.7% of large farms reporting use of bST. 

Some asceptic processes are developed initially in non-sterile facilities and need to be re-designed to produce a sterile product. Thus the type, size and material used for vessels, piping and tubing (particularly product contact surfaces), the selection of appropriate equipment for each unit process i.e. mixing, filtration, filling, etc., the use of disposable or re-usable equipment, the order of unit operations, the fluid transfer between unit operations and... 

For every commercial catalyst an optimal combination of unit operation sequence exists for the manufacture of that specific catalyst and there will for each unit operation exist preferential process equipment, i.e. fluid bed calciner for calcination. The sequence of unit operations with the special selection of process equipment and all process parameters forms the know-how for manufacturing a catalyst product of large commercial value. But know-how does not mean that you always know why the desired properties are obtained due to the insufficient scientific characterisation of the catalyst material as described above under 2.1. Even small adjustments of the process can change strength, pore size distribution, bulk density, crystallite size etc. of the product and, thus, harm the performance in the industrial reactor. It has normally been costly and time-consuming to reach the final recipe and, therefore, all catalyst companies want to keep it secret. If a single unit operation is changed it will often influence the optimisation of most of the other unit operations, and much of the development will have to be redone. 

The choice of size of unit was dependent not only on investment costs, but also on the availability of membranes of suitable size and price. Many other design and operating considerations had to be considered. These have been fully discussed (9). 

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