Operating strategy

Flocculants are designed to be very attractive to solid surfaces and adsorption takes place almost instantaneously. However this can lead to inefficient distribution, as polymer can be adsorbed by only the first part of the feed that it contacts, leaving other solids imtreated. 

This effect is exacerbated by the difficulty of dispersing the viscous polymer solution into a viscous slurry. Flocculant solution is therefore applied at as dilute a concentration as possible, typically 0.3%. However, this would require an excessively large flocculant dissolution facility. The compromise is often to maximise the preparation of a high concentration stock solution, for example 0.5-1.0%, and provide the facility for in-line dilution close to the polymer solution injection. The benefits of this are often overlooked. 

The efficiency of generating polymer/solids collisions with minimum floe breakdown is reduced in a viscous and crowded particulate suspension. Cost and efficiency improvements can be gained via feed dilution with water or recycled clarified liquor. 

The placement of the injection point of the flocculant solution can have a critical influence on the resulting performance. Generally a point of turbulence is chosen to ensure homogeneous distribution of polymer into the substrate. The point of addition also defines the mixing time. This needs to be sufficient for solids capture but, at the same time, not to give excessive floe rupture. 

The conflict between capture and size can be overcome by applying the flocculant at two or more points. The first dosage is exposed to sufficient mixing to maximise solids capture. A late addition under lower-shear conditions finally maximises bridging flocculation. 

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Choice of operating strategy has a significant effect on substrate conversion, product susceptibility to contamination and process reliability. 

To create an awareness of the program objectives and their importance, and to establish customer confidence in the program s operational strategies through training, mutual cooperation, communication, and management review... 

Connell GE (2006) Key operation strategies for chlorine disinfection operating systems. Proceedings of WEFTEC, Water Environment Federation... 

C. Case Study Operating Strategies for Desired Octane Number.394... 

In Section IV we provide illustrations of the modeling concepts presented in Section II and how the strategy of nonmonotonic planning has been used to synthesize the switchover operating strategy for a chemical process. 

However, the Pt anode is seriously poisoned by trace amounts of carbon monoxide in reformates (fuel gas reformed from hydrocarbon), because CO molecules strongly adsorb on the active sites and block the HOR [Lemons, 1990 Igarashi et ah, 1993]. Therefore, extensive efforts have been made to develop CO-tolerant anode catalysts and cell operating strategies to suppress CO poisoning, such as anode air-bleeding or pulsed discharging. 

The development of novel bioreactors and bioreactor operating strategies has the potential to improve the performance of cell culture systems. Some progress has been made in this area to enhance foreign protein production in plant tissue culture. 

The present survey addresses studies on azo-dye conversion by means of bacteria, with a close focus on bioreactor design and operational strategies. Other chapters of the Handbook and recently published reviews [1, 2] address instead the detailed biochemical pathways underlying azo-dye conversion and the fate of the conversion products. 

In another setting, the human players are provided with global information about the system. This means that all players are informed about inventory levels and orders placed for each of the components of the supply chain. Furthermore, they are encouraged to work out co-operative strategies to deal with the dynamics of the system. Compared to the local information structure, this usually results in lower inventory levels and less out-of-stock-situations for all participants. Typically, the stocks and the number of orders in this setting are much lower, resulting in much lower costs for operating the supply chain and lower costs for each player as well. 

Mdndez, C.A. and Cerda, J. (2003a) An MILP continuous-time framework for short-term scheduling of multipurpose batch processes under different operation strategies. Optim. Eng., 4, 7. 

Operant strategies. Techniques that use reinforcement or punishment to shape behavior. 

Dump fill, instantaneous addition of waster water into the reactor is rarely used in the field but is implemented practically by including a static fill in the operating strategy. The mathematical representation for the SBR with dump fill is the same as that for the plug reactor at steady state, where the hydraulic residence time in the PFR compares to the time for react in the SBR. 

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