Intermediate heat exchangers critical temperature

Helium gas of the Hl IR coolant is circulated under a pressure of 4 MPa, and through an intermediate heat exchanger, high temperature heat is transferred to the hydrogen production process as shown in Figure 5. The first criticality of the HTTR was achieved in 1998, and the Full power operation of 30 MW was attained in 2001. Then, the reactor outlet temperature was 850°C. Safety demonstration tests have been conducted since 2002. In April 2004, we conducted first high-temperature operation of 950°C (3). 

The HTTR is an experimental helium-cooled 30 MW(t) reactor. The HTTR is not designed for electrical power production, but its high temperature process heat capability makes it worthy of inclusion here. Construction started in March 1991 [47] and first criticality is expected in 1998 [48]. The prismatic graphite core of the HTTR is contained in a steel pressure vessel 13.3 m in height and 5.5 m in diameter. The reactor outlet coolant temperature is 850°C under normal rated operation and 950°C under high temperature test operation. The HTTR has a primary helium coolant loop with an intermediate helium-helium heat exchanger and a pressurized water cooler in parallel. The reactor is thus capable of providing... 

The miscibility of water and hquid carbon dioxide is very poor and an intermediate solvent has to be used to allow the replacement of water by carbon dioxide. In a procedure initially developed to prepare representative samples for electron microscopy, water is replaced by ethanol through exchanges with alcoholic solutions of increasing concentration. The alcogel prepared by a final exchange with absolute ethanol (Fig. 3c) is introduced in a pressure vessel in which liquid CO2 is admitted and replaces ethanol in the gel. The C02-impregnated gel is compressed and heated above the critical point of CO2 (31.05°C, 73.8 bar). Release of pressure above the critical temperature allows CO2 to be extracted without the formation of any liquid-vapor interface and a dried aerogel is formed (Fig. 3d). 

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