Practical Regeneration Systems

Practical Aspects There are a number of process-specific concerns that are accounted for in good design. In regenerate systems, sorbents age, losing capacity because of fouling by heavy contaminants, loss of surface area or crystallinity, oxidation, and the like. Mass-transfer resistances may increase over time. Because of particle shape, size distribution, or column packing method,... 

The straightforward concept for the direct light-driven regeneration of flavin-dependent enzymes has been successfully applied for two representative classes of such enzymes a reductase and a monooxygenase. Therefore, it can be expected that this concept can also be applied to other flavin-dependent enzymes, potentially leading to additional practical catalyst systems for applications in synthetic organic chemistry. 

In most plant design situations of practical interest, however, the several pieces of equipment interact with each other, the output of one unit being the input to another that in turn may recycle part of its output to the inputter. Common examples are an absorber-stripper combination in which the performance of the absorber depends on the quality of the absorbent being returned from the stripper, or a catalytic cracker-catalyst regenerator system whose two parts interact closely. 

The use of isolated enzymes to form or cleave P-O bonds is an important application of biocatalysts. Restriction endonucleases, (deoxy)ribonucleases, DNA/ RNA-ligases, DNA-RNA-polymerases, reverse transcriptases etc. are central to modern molecular biology(1). Enzyme catalyzed phosphoryl transfer reactions have also found important applications in synthetic organic chemistry. In particular, the development of convenient cofactor regeneration systems has made possible the practical scale synthesis of carbohydrates, nucleoside phosphates, nucleoside phosphate sugars and other natural products and their analogs. This chapter gives an overview of this field of research. 

A nucleoside phosphate regeneration system must meet several specifications to be practical. To be economical, a regeneration method must be capable of recycling the cofactor 102-106 times1391. All materials should be readily available, inexpensive, easily handled, stable under reaction conditions and compatible with the rest of the reaction system. The transfer of phosphate should be thermodynamically and... 

ADP phosphorylation with polyphosphate (P ) and polyphosphate kinase (P K E.C. 2.7.4.1) has also been demonstrated1441. The cheap, stable polyphosphates and the stability of P K are highly attractive. Unfortunately, P has a low phosphorylating potential and P K is not readily available. These facts may explain why this regeneration system has not found any practical application. 

Efficient regeneration of the zinc particles is required to provide for a practical, efficient system. It is projected that for the practical application of this system, the spent electrolyte and residual particles would be removed at local service centers and the vehicle would be quiekly refueled by the addition of regenerated zinc powder and electrolyte. The system under development involves stopping the discharge of the battery described when the voltage falls below a practieal value rather than when the voltage becomes zero. Under these eonditions, no precipitation has occurred and the electrolyte is clear. The processing of produets removed from the cell is then simply one of redeposition of zinc onto the particles. 

Lowering regenerator temperature by only allowing part of the coke to bum to CO2 has been practiced for many years in conventional one stage regenerators. The two regenerator system... 

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