Regenerative heat recovery

For large-capacity plants with subautogenic feeds, regenerative heat recovery is very important to minimize the need for supplementary fuel and/or additional oxidant. 

An early configuration of the LTS-100 was tested in January 2005 in an oil-fired float glass furnace that used a cross-fired furnace with regenerative heat recovery (Jenkins and Bergmans 2005). Figure 14.13 shows a... 

Regenerative heat exchange can be more expensive to install but can readily offer 95% heat recovery efficiency. Regenerative systems are therefore best suited to more dilute streams or those with variable VOC concentration they are widely used in coatings applications. Recuperative systems are more cost effective for higher-concentration VOC streams of constant composition they find widespread use in chemical production. Both recuperative and regenerative heat recovery can be used with either thermal or catalytic oxidation systems and with secondary heat recovery. 

Figure 13-2. Simplified flow diagram of three-bed thermal oxidation system with regenerative heat recovery and positive purge.

Many compounds can cause problems in pollutant-control equipment. Particulate matter, liquids, or solids in the waste stream can plug the adsorber beds, heat-recovery beds in regenerative thermal incinerator systems and biofilters. Conventional filtration systems are used to remove particulate matter before or after the process. 

The results of the performance calculations are summarized in Table 9-24. The efficiency of the overall power system, work output divided by the lower heating value (LHV) of the CH4 fuel, is increased from 57% for the fuel cell alone to 82% for the overall system with a 30 F difference in the recuperative exchanger and to 76% for an 80 F difference. This regenerative Brayton cycle heat rejection and heat-fuel recovery arrangement is perhaps the simplest approach to heat recovery. It makes minimal demands on fuel cell heat removal and gas turbine arrangements, has minimal number of system components, and makes the most of the inherent high efficiency of the fuel cell. 

The results of the performance calculations for the fuel cell, Rankine cycle heat recovery system, summarized in Table 9-24, indicate that the efficiency of the overall system is increased from 57% for the fuel cell alone to 72% for the overall system. This Rankine cycle heat-fuel recovery arrangement is less complex but less efficient than the combined Brayton-Rankine cycle approach, and more complex and less efficient than the regenerative Brayton approach. It does, however, eliminate the requirement for a large, high temperature gas to gas heat exchanger. And in applications where cogeneration and the supply of heat is desired, it provides a source of steam. 

Figure 2. Simplified schematic drawing of the extraction plant (1 regenerative pump, 2 fluid cyclone, 3 storage tank, 4 gear pump, 5 circulation gas condensator, 6 diaphragm pump, 7 heat recovery, 8 preheater, 9 heat exchanger, 10 cyclone separator, 11 feed pump, 12 feed preheater, 13 thermostatic chamber)...

In incineration, gaseous organic-vapor emissions are converted to carbon dioxide and water through combustion. There are two types of thermal incinerator, based on heat recovery employed, regenerative and recuperative. 

Most heat recovery efforts are aimed at utilizing the waste heat exiting through the flues. Some forms of heat recovery are air preheating, fuel preheating, load preheating (Fig. 1.17), recuperative, regenerative, and waste heat boilers—all discussed in chapter 5. 

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