85 Economics Of Wasteheat Recovery 851 General

are no different from those used for the analysis of any other industrial capital project. These techniques are thoroughly discussed in Chapter 4 of this volume.18 The economic potential for this class of systems is often limited by factors that are crucial yet overlooked. Although the capital cost of these systems is proportional to the peak rate of heat recovery, the capital recovery depends principally on the annual fuel savings. These savings depend on a number of factors, such as the time distribution of waste-heat source availability, the time distribution of heat-load availability, the availability of waste-heat-recovery equipment that can perform at the specified thermal conditions, and the current and future utility rates and prices of fuel. The inability to accurately predict these factors can make the normal investment decision-making process ineffectual.

There is another important distinction to be made about waste-heat recovery investment. When capital projects involve production-related equipment, the rate

Steam Out Cooled Waste

Steam Out Cooled Waste

Figure 8.29 Two-pass waste-heat boiler.

Economic analysis techniques used for analyzing investment potential for waste-heat-recovery systems

Figure 8.29 Two-pass waste-heat boiler.

Figure 8.30 A Recirculation waste-heat boiler.
Table 8.8 Operation and Application Characteristics of Industrial Heat Exchangers

Specifications for Waste Recovery \ Unit

Commercial

Heat-Transfer

Equipment

Low temperature: subzero -250°F

Intermediate temp: 250-1200°F

High temperature: 1200-2000°F

Recovers moisture

Large temperature differentials permitted

Packaged units available

contamination

Compact size

Gas-to-gas heat exchange

Gas-to-liquid heat exchanger

Liquid-to-liquid heat exchanger

Corrosive gases permitted with special construction

Radiation recuperator

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