Utility systems process efficiency

One-electron reduction or oxidation of organic compounds provides a useful method for the generation of anion radicals or cation radicals, respectively. These methods are used as key processes in radical reactions. Redox properties of transition metals can be utilized for the efficient one-electron reduction or oxidation (Scheme 1). In particular, the redox function of early transition metals including titanium, vanadium, and manganese has been of synthetic potential from this point of view [1-8]. The synthetic limitation exists in the use of a stoichiometric or excess amount of metallic reductants or oxidants to complete the reaction. Generally, the construction of a catalytic redox cycle for one-electron reduction is difficult to achieve. A catalytic system should be constructed to avoid the use of such amounts of expensive and/or toxic metallic reagents. 

Most processes operate in the context of an existing site in which a number of processes are linked to the same utility system. The utility systems of most sites have evolved over a period of many years without fundamental questions being addressed as to the design and operation of the utility system. The picture is complicated by individual production processes on a site belonging to different business areas, each assessing investment proposals independently from one another and each planning for the future in terms of their own business. Yet, the efficiency of the site infrastructure and the required investment is of strategic importance and must be considered across the site as a whole, even if this crosses the boundaries of different business areas. 

However, a more useful measure of the utility system performance is the cogeneration efficiency. Of the fuel fired in the utility system, some of this energy produces power, some provides useful process heat and some is lost. The cogeneration efficiency recognizes the amount of fuel consumed to produce both power and useful process heat, and can be defined as1516 ... 

While this basic definition of cogeneration efficiency seems straightforward, complications are created by the process steam generated from waste heat recovery that can be used for power generation or process heating and that does not require any fuel to be fired in the utility system. The heat supply can be defined as the sum of the heat from fuel (both in the utility boilers and fired heaters) and steam generation from the waste heat recovery (see Figure 23.44)17 ... 

Increased energy efficiency at the point of use can be achieved effectively by improved heat integration. Increased energy efficiency of the utility system can be improved through better matching between processes and the utility system, improved cogeneration, and so on. Improvements to combustion processes are effective for NO reduction. 

Although a fuel cell produces electricity, a fuel cell power system requires the integration of many components beyond the fuel cell stack itself, for the fuel cell will produce only dc power and utilize only processed fuel. Various system components are incorporated into a power system to allow operation with conventional fuels, to tie into the ac power grid, and often, to utilize rejected heat to achieve high efficiency. In a rudimentary form, fuel cell power systems consist of a fuel processor, fuel cell power section, power conditioner, and potentially a cogeneration or bottoming cycle to utilize the rejected heat. A simple schematic of these basic systems and their interconnections is presented in Figure 9-1. 

Economics This process uses a proprietary resin catalyst system it has consistently achieved greater than 98% efficiency of raw-material utilization. The process is simple and requires few processing steps resulting in a low equipment count and capital cost. 

Remove exothermic heats of reaction. The elimination of excess heat directly to utility could lead to a more responsive but inefficient process. Transfer to another unit(s) via process stream(s) improves the energy efficiency, but might affect controllability. After all the excess heat will be dissipated to the utility system. 

Efficient integration of the process with the utility system involves reducing the two principal areas of irreversibility that are inherent in the cyde the... 

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