Hydrogen Liquefaction Optimization

In the process of hydrogen liquefaction, one must consider the inversion temperature (-361°F or -183°C or 90°K) of hydrogen, because the behavior of this gas changes (inverses) at that temperature. Below the inversion temperature, when the pressure is reduced, the hydrogen temperature will drop (above that temperature, the opposite occurs a drop in pressure causes a rise in tern- 

Post-Oil Energy Technology After the Age of Fossil Fuels 

The control and optimization of a nitrogen precooled hydrogen liquefaction process. 

Before hydrogen can be liquefied, it must be purified and converted from the normal to the para form. LH2 is 99.8% para and only 0.2% ortho. Cata- 

The two key temperatures of the liquefaction process (inversion and liquid product temperatures) are controlled by TC-25 and TC-26. TC-25 modulates the level set point of LC-24 of the LN2 accumulator, and TC-26 adjusts the level set point of FC-27 of the LH2 accumulator. The LH2 (or nitrogen) supplies to the evaporators are controlled by cascade loops that adjust the levels in the accumulators, which in turn vary the heat transfer area, and therefore, the rate of evaporation. 

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A number of other optimization strategies will be discussed later in this chapter. The savings resulting from replacing the letdown valves with expander turbine generators will be discussed in Section 2.13. The optimization of multistage chillers will be covered in connection with hydrogen liquefaction in Section 2.15.3, and coolant distribution controls will be covered under pump optimization in Section 2.17.2. 

To improve selectivity and conservation of hydrogen over present liquefaction technology in the conversion of coal to high quality liquids, we believe that thermal reactions should be kept as short as possible. Catalytic processes must be used for upgrading but should be used in a temperature regime which is optimal for such catalysts. 

This statement applies without any restriction to coal liquefaction as well. Hence, for hydrogenation process engineering the optimization of the reaction conditions has precedence over the raw material properties. 

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