Increased heat recovery

These sources of waste from the steam system can be reduced by increasing the percentage of condensate returned (in addition to reducing steam generation by increased heat recovery). 

A more obvious energy loss is the heat to the stack flue gases. The sensible heat losses can be minimized by reduced total air flow, ie, low excess air operation. Flue gas losses are also minimized by lowering the discharge temperature via increased heat recovery in economizers, air preheaters, etc. When fuels containing sulfur are burned, the final exit flue gas temperature is usually not permitted to go below about 100°C because of severe problems relating to sulfuric acid corrosion. Special economizers having Teflon-coated tubes permit lower temperatures but are not commonly used. 

Vapor-phase coohng reduces the cost of the cooling system, increases heat recovery, and may result in improved engine efficiency. 

Chemical in South Korea in 1987.38 39 The process is based on 310 stainless steel, which resists corrosion in 98.5 percent H2S04 at temperatures up to 220°C. The intermediate absorber at Namhae takes 194°C gas from the converter third stage economizer and absorbs the S03 in 199°C, 99 percent acid. Recirculated acid from the absorber is cooled from 220°C in a 10-bar HRS boiler. The added energy recovery for this process is reported to increase the total recovery to 90 percent. Monsanto s proposed Monarch process combines HRS technology with the wet catalytic converter process (Lurgi) to increase heat recovery and shift it to high-pressure steam production for electric power generation.36... 

Increase heat recovery from the product gas to the feed streams to preheat the reactor feed and reduce the amount of oxygen that is needed. 

Rotary kilns can also be fitted with a kiln-feed preheater see Figure 6.8, which enables a shorter kiln to be used, approximately one-half the length of a conventional rotary. The exhaust heat is used to preheat the burden entering the kiln thus increasing heat recovery and improving the thermal efficiency of the furnace. 

In the pulping industry, sulfur oxides emissions represent loss of pulping chemical, but the economic loss is apparently not regarded as very serious, at least in this period of relatively abundant and cheap sulfur. In current practice, much sulfur is evidently lost to become either a water or air pollutant (16, 53, 102), but pollution control regulations are forcing increased recovery and recycling of sulfur and other pulping chemicals. The need to increase heat recovery and use should also influence emission controls. 

Rotary kilns fitted with pre-heaters (type K in Table 16.1 Figs. 16.16 and 16.17) are generally considerably shorter than the conventional rotary kiln (e.g. 40 to 60 m). The heat usage decreases because of reduced radiation and convection losses as well as the increased heat recovery from the exhaust gases. Thus, with coal firing, net heat usages below 1250 kcal/kg are reported. 

The network pinch identifies the heat recovery limit inherent in an existing heat exchanger network and therefore indicates the requirement of structural changes to the HEN. In other words, when a network reaches its network pinch limit, the only way to overcome it or increase heat recovery is to make stmctural changes if no process changes are considered. 

Third Step Low Capital Investment via Increased Heat Recovery... 

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