Energy exchange steam generation

PWR reactor Nuclear reactor where the core power is transported by pressurized water which circulates in a system of primary circuits. The production occurs within a set of Heat Exchangers (Steam Generators), using the thermal energy contained in primary water (PWR = Pressurized Water Reactor). 

Pressurized vs. boiling LWRs The pressurized water reactor (PWR) transfers its energy from the fuel to an intermediate heat exchanger to generate the steam that... 

Indirect or direct fired heaters are widely used in the process industries. Heat loss is kept to a minimum by refractory coatings on the furnace wall. Any material in the fuel that is corrosive or forms excess soot has to be avoided. Usually 20-25% excess air is required for fuel oil vs. 5-10% for gaseous fuel, hence the latter is more economic. Energy in the exit flue gas not used to heat water or a product can be recovered by heat exchangers that generate additional steam or preheat the entering air. 

The trend followed in newer plants is to increase conversion per pass with the result of higher ammonia outlet concentrations and lower outlet temperatures from the last bed. However, as optimum energy efficiency of the whole ammonia plant requires maximum high-pressure steam generation, part of the heat must be recovered before the reaction is completed in the reactor system. This can be accomplished [900], [901], [930], [931] by using three catalyst beds in separate pressure vessels with boilers after the second and the third vessel and an inlet - outlet heat exchanger for the first catalyst bed. 

This system also demonstrates the latest technologies in heat recovery by heat exchange of the hot oil in the drop tank with the incoming cold oil and by steam generation for reactor cooling. The hydrogenation department becomes a net exporter of steam, the ultimate form of energy conservation. 

The steady state model is based on the mass and energy balances which were carried out over the furnace, heat exchanger area, economising section, dolezal, drum, generating section and superheaters. A set of nonlinear algebraic equations were used to accurately predict changes in the physical state of each system. Fig. 1 shows a simplified PFD for recovery boiler steam generation cycle. 

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