Steam production principles

An important principle for making steam from acid is that Fig. 24.8 s boiler feed acid should be as hot as possible while  

The net result is hotter absorption tower exit acid (i.e., boiler feed acid). 

A slight temperature increase can also be obtained by increasing absorption tower feed gas temperature (Fig. 24.3). 

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This is the same principle as IFGR—the steam dilutes the fuel gas thus reducing both the flame temperature and the localized hot spots. Systems have used up to 8% steam injection (the steam injection rate is 8% of the total steam production from the boiler). 

Drum Drying. The dmm or roHer dryers used for milk operate on the same principles as for other products. A thin layer or film of product is dried over an internally steam-heated dmm with steam pressures up to 620 kPa (90 psi) and 149°C. Approximately 1.2—1.3 kg of steam ate requited per kilogram of water evaporated. The dry film produced on the roHer is scraped from the surface, moved from the dryer by conveyor, and pulverized, sized, cooled, and put iato a container. 

A fourth type of innovation is one which results in an entirely new process in the engineering sense. All the process coefficients may be very different in fact, entirely different inputs may be used, or new physical or chemical principles may be employed. In contrast to production of ammonia from coal, steam reforming of natural gas was such an innovation, as was the shift from propellor to jet aircraft. Current research to produce nitrogen-fixing (ammonia-producing) bacteria that are symbiotic with corn through DNA manipulation is innovative activity of the fourth type. 

In principle, the flowsheet of an industrial facility is similar to those of the different hydrotreating processes (Figure 5.2-42) [61]. The feedstock C4 cut rid of water is pressurized to about 15 to 20 bar by pumping, injected with a hydrogen-rich gas and then, preheated by heat exchange with the reaction effluent and by steam. In a downflow stream, it then enters the reactor, which operates in a gas-liquid mixed phase with one or more catalyst beds (palladium, rhodium on inert alumina). After cooling, the isomerization products are flashed... 

The reactor can operate with either a liquid-phase reaction or a gas-phase reaction. In both types, temperature is very important. With a gas-phase reaction, the operating pressure is also a critical design variable because the kinetic reaction rates in most gas-phase reactions depend on partial pressures of reactants and products. For example, in ammonia synthesis (N2 + 3H2 O 2NH3), the gas-phase reactor is operated at high pressure because of LeChatelier s principle, namely that reactions with a net decrease in moles should be mn at high pressure. The same principle leads to the conclusion that the steam-methane reforming reaction to form synthesis gas (CH4 + H20 O CO + 3 H2) should be conducted at low pressure. 

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