Liquefaction Plants

A hydrogen liquefier consists of piston compressors that usually can operate at three pressure levels and a liquefier cold box. The cold box includes a 

in the heat pumps, the energy of compression is not recovered but is wasted in letdown valves (as the pressure of the working fluid is reduced to the low pressure of the evaporator (Joule-Thomson cycle), the liquefaction efficiency will be low (35-60%). This range of efficiencies is a function of the liquefier size and refrigerant used. If the letdown valves are replaced by turbo expanders (Brayton cycle), which recover some of the compression energy during pressure letdown, and if helium or neon refrigerants are used, the efficiency can theoretically reach 80-90%. 

For a plant capacity of 100 kg/h of LH2 production, the electric energy requirement is about 60 mj/kg (17 kWh/kg). The specific energy input drops as plant size increases to a minimum of about 40 mj/kg (11 kWh/kg). As the HHV of H2 is 141.5 mj/kg (39.3 kWh/kg), the energy cost of liquefaction at a 100 kg/h capacity is about 42%. In small units, the energy cost of production can exceed the HHV of the H2, and even in large plants (1,000 kg/h capacity), it can be around 35%. 

In the process of liquefaction, one must also consider the inversion temperature (-361°F or -183°C or 90°K) of H2, because the behavior of this gas changes (inverses) at that temperature. Below the inversion temperature, when the pressure is reduced, the H2 temperature will drop. Above that temperature the opposite occurs a drop in pressure causes a rise in temperature. Therefore, in the process of liquefaction, H2 first has to be cooled below its inversion temperature—by such means as cooling with LN2—before the Joule-Thomson effect can be utilized. 

Refrigeration down to 80°K is therefore provided by LN2. The next step of refrigeration from 80 to 30°K is carried out using the Brayton cycle, in which high-pressure H2 is expanded in a number of turbo expanders in series. From 30°K to liquefaction, the Joule-Thomson cycle is used, where high-pressure gas is throttled to low pressure to provide further cooling. 

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Fig. 4. Equipment flow sheet of elemental fluorine production and liquefaction plant, 9 t/d capacity. Step 1 purging residual F2 at rates indicated all but a trace of residual F2 is removed in 15min N2 purge is maintained for 1 h to remove last traces. Step 2 HF removal at rates indicated all but a trace of HF is...

Direct-Liquefaction Processes Figure 27-8 presents a simph-fied process flow diagram of a typical direct coal liquefaction plant. Specific processes are described in the following paragraphs. 

Status of Indirect Liquefaction Technology The only commercial indirect coal liquefaction plants for the production of transportation fuels are operated by SASOL in South Africa. Construction of the original plant was begun in 1950, and operations began in 1955. This plant employs both fixed-bed (Arge) and entrained-bed (Synthol) reactors. Two additional plants were later constructed with start-ups in 1980 and 1983. These latter plants employ dry-ash Lurgi Mark IV coal gasifiers and entrained-bed (Synthol) reactors for synthesis gas conversion. These plants currently produce 45 percent of South Africa s transportation fuel requirements, and, in addition, they produce more than 120 other products from coal. 

TABLE 27-16 Estimated Costs of Direct Coal Liquefaction Plant... 

TABLE 27-17 Estimated Costs of Indirect Coal Liquefaction Plant (1993 US Dollars)... 

Large quantities of inert gas are required for the inert blanketing of taiiks and for purging. This gas usually is supplied from a central facility. Nitrogen is normally used and can be manufactured on site in an air liquefaction plant or purchased as liquid in tankers. 

All currents that had to be measured were sent to a central measurement room in which many mirror galvanometers were situated on top of vibration-free columns that were separated from the foundations of the building. One should realize that the many announcements in the early literature of the liquefaction of specific gases pertained to not much more than a mist or a few drops Kamerlingh Onnes planned to make liquid gases by the gallon. A separate hydrogen liquefaction plant was located in a special room with a roof that could be blown off easily. 

Because much of the world lacks the natural gas resources and transportation pipelines of the United States, remote natural gas must be liquefied and transported by ship. Gas-rich countries want to capture stranded gas by liquefying and shipping it to gas-poor regions as LNG. The gas-poor countries enter into contracts so that a long-term supply is available to warrant the investment in the electricity-generating infrastructure. The overall investment is enormous, not only in the liquefaction plant, but in the refrigerated tankers and the regasification plant at the deliveiy site. 

Installations Compressor station k LNG storage with liquefaction plant Underground storage (salt cavity)... 

The chlorine value can be converted into hypochlorite bleach by absorption into lime or caustic soda. It can also be used to produce hydrogen chloride by combining with hydrogen in a burner. The latter technique is particularly useful when the acid can be consumed on site in brine acidification or ion-exchange resin regeneration. Another approach that has found some favour in the past is the absorption of the chlorine into a solvent from which it could then be stripped and returned to the liquefaction plant. 

The chlorine liquefaction plant comprises a bromine-removal column, a compression-condensation unit and a Tetra absorption/distillation unit (Fig. 14.2). Waste streams of chlorine are absorbed in diluted cell-liquor in the chlorine destruction area. As a result, the destruction liquid contains sodium chloride and less sodium hydroxide than is usual. Bromine from the bromine-removal column is also added to the chlorine destruction unit. The hypochlorite solution that is formed contains a reasonable amount of bromine and salts. However, it is a hypochlorite of non-marketable quality. 

Oil from shale or coal liquefaction can be less expensive than crude oil at current prices, but production costs are higher than developed oil fields. There is an investment risk that crude oil prices could and then liquefaction plants could not compete. Nuclear energy does not have this disadvantage. 

Up to now, there are only about ten commercial-scale hydrogen liquefaction plants worldwide, of which the largest production capacities are located in the USA, which... 

The principal options for hydrogen transport and distribution include pipelines, gaseous and liquid trailers. The choice for the most economic option depends on transport volumes and transport distances. For the transport of liquid hydrogen, additionally the costs of the liquefaction plant need to be taken into account. Another possibility could be to blend hydrogen with natural gas up to a certain extent and either separate the two at the delivery point, or use the mixture, e.g., in... 

Integer variables are included in the model to ensure that new capacities can only be installed as integer multiples of a given plant capacity (if, e.g., hydrogen liquefaction plants in the model are only defined for a capacity of 100 MWh2, only liquefaction capacities of 100 MWh2, 200 MWh2, etc., can be installed). This approach allows the definition of different capacity classes of, e.g., production plants or transport... 

Figure 14.13 exemplifies the location of hydrogen liquefaction plants in Germany in 2030, as well as the transport flows of hydrogen by trailer and pipeline, respectively. 

Exxon Coal Liquefaction Plant Prepared for Startup," Coal R D 3 (February 15, 1980), pp 1-2 Porter, Robert. "April Startup set for Synfuel Plant in Texas," Energy Insider 3 (February 18, 1980), pp 1, 5 3 (July 7, 1980), p 1 ... 

SELECTION OF CEFiAMIC PIPING FOR COAL SLURRIES IN A COAL LIQUEFACTION PLANT 827... 

If the Illinois 6 coal was used as feedstock for both the indirect and direct liquefaction plants, then approximately the same amount of sulfur per barrel would be produced. 

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