Downstream processing upstream considerations

Traditionally, the upstream fermentation and cell culture processes have been viewed as being distinct from the subsequent downstream processing and purification steps, and the two different sets of processes nave been optimized individually. In some instances, careful consideration of the conditions used in the fermentation process, or manipulation of the genetic makeup of the host, can simplify and even... 

The first consideration in any design and optimization problem is to decide the boundaries of the system. A reactor can rarely be optimized without considering the upstream and downstream processes connected to it. Chapter 6 attempts to integrate the reactor design concepts of Chapters 1-5 with process economics. The goal is an optimized process design that includes the costs of product recovery, in-process recycling, and by-product disposition. The reactions are... 

This chapter will only deal with the possible gas transport mechanisms and their relevance for separation of gas mixtures. Beside the transport mechanisms, process parameters also have a marked influence on the separation efficiency. Effects like backdiffusion and concentration polarization are determined by the operating downstream and upstream pressure, the flow regime, etc. This can decrease the separation efficiency considerably. Since these effects are to some extent treated in literature (Hsieh, Bhave and Fleming 1988, Keizer et al. 1988), they will not be considered here, save for one example at the end of Section 6.2.1. It seemed more important to describe the possibilities of inorganic membranes for gas separation than to deal with optimization of the process. Therefore, this chapter will only describe the possibilities of the several transport mechanisms in inorganic membranes for selective gas separation with high permeability at variable temperature and pressure. 

Often an improvement in one section of a line or plant will cause the rate-limiting section to shift to either an upstream or downstream process. These types of projects often have considerable value associated with them because of the multiple bottlenecks that exist. 

As can be seen from the four different examples, the choice of purification steps and procedures depends on the product location and properties and ultimately very much on the target application. Considerations are if the molecule is intracellular, cell associated, or extracellular and if it is soluble in the aqueous fermentation liquid or not. Other considerations are the fermentation medium itself and the fermentation organism. Large-scale industrial fermentation media often relies on complex, crude feedstocks as nutrient sources, as using defined nutrient sources is usually cost prohibitive. One of the major challenges is that complex fermentation media can lead to more variability in the fermentation output. To consistently deliver a robust product, downstream processing and formulation need to be able to normalize the upstream variability. 

Then, product quality control loops are closed on each of the individual units. These loops typically use fast PI controllers to hold product streams as close as possible to specification values. Since these loops are considerably faster than the slow inventory loops, interaction between the two is generally not a probleia Also, since the manipulated variables used to hold product qualities are often streams that are internal to each individual unit, changes in these manipulated variables have little effect on the downstream process. The manipulated variables frequently are utility streams that are provided by the plant utility system, i.e. cooling water, steam, refrigerant, etc. Thus, the boiler house will be disturbed, but the other process units in the plant will not see disturbances coming from upstream process units. Of course, this is only tme when the plant utilities systems have effective control systems that can respond quickly to the many disturbances that they see coming in from units all over the plant. 

There is much current interest aimed at the implementation of processes that integrate the upstream and downstream operation for protein recovery.131419 Although adsorption in fluidised beds provides a considerable saving in cost and time over conventional purification techniques, it still deploys a discrete operation with which the desired protein is captured at termination of fermentation or once a cell suspension has been disrupted. The main... 

The economics of the solvent extraction process are very dependent upon upstream and downstream portions of the plant. Integration of the total processing step is essential to obtain maximum return. Variables, such as tonnage rates and changes in solution composition, can have a most significant result on the economics of solvent extraction. Generally, economic considerations may be divided into two major areas (1) capital investments and (2) operating costs. 

Given an initial temperature for the node, T, it is possible to find the specific internal energy, u = u(T), and the specific volume, v = v(T), and hence the mass m = V/v. Equation (18.65), taken in conjunction with auxiliary equations (18.63), represents an implicit equation in the nodal pressure, p, which may be solved using the methods already outlined, either iteration or the Method of Referred Derivatives. The upstream and downstream flows, Wyp, and Wj , may then be found, so that it becomes possible to calculate the right-hand side of the temperature differential equation (18.64). Equation (18.64) may then be integrated to find the temperature of the node at the next timestep. The process may then be repeated for the duration of the transient under consideration. 

Typically the sizing of drums is related to a process consideration such as liquid holdup (surge), storage volume, or velocity considerations for separation. Surge volume in process units relates to the response time required for the alarms and operators to respond to upstream or downstream conditions. 

Consideration of the impact of washing and water within the life cycle of inkjet printed textiles might be complemented by steps in the supply chain that are upstream or downstream from the inkjet print process. Downstream are the uses for the printed cloth, usually as raw material for another industry, such as fashion, before it reaches the final consumer. Upstream, the process of inkjet printing on textiles, can be considered to begin with the preparation of the fabric for ink jet or digital printing. 

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