CO2 temperature control

The CO2 temperature control allows high temperature-control performance as well as temperature control of slim cores in inaccessible areas and in material accumulations. However, this type of temperature control is seen as a complementary facility for problem areas and not as the sole temperature control method. Otherwise this type of temperature control would lead to significant costs. 

The catalytic reforming of CH4 by CO2 was carried out in a conventional fixed bed reactor system. Flow rates of reactants were controlled by mass flow controllers [Bronkhorst HI-TEC Co.]. The reactor, with an inner diameter of 0.007 m, was heated in an electric furnace. The reaction temperatoe was controlled by a PID temperature controller and was monitored by a separated thermocouple placed in the catalyst bed. The effluent gases were analyzed by an online GC [Hewlett Packard Co., HP-6890 Series II] equipped with a thermal conductivity detector (TCD) and carbosphere column (0.0032 m O.D. and 2.5 m length, 80/100 meshes), and identified by a GC/MS [Hewlett Packard Co., 5890/5971] equipped with an HP-1 capillary column (0.0002 m O.D. and 50 m length). 

The catalysts were tested for their CO oxidation activity in an automated microreactor apparatus. The catalysts were tested at space velocities of 7,000 -60,000 hr . A small quantity of catalyst (typically 0.1 - 0.5 g.) was supported on a frit in a quartz microreactor. The composition of the gases to the inlet of the reactor was controlled by mass flow controllers and was CO = 50 ppm, CO2 = 0, or 7,000 ppm, HjO = 40% relative humidity (at 25°C), balance air. These conditions are typical of conditions found in spacecraft cabin atmospheres. The temperature of the catalyst bed was measured with a thermocouple placed half way into the catalyst bed, and controlled using a temperature controller. The inlet and outlet CO/CO2 concentrations were measured by non-dispersive infrared (NDIR) monitors. 

Berndt et al. (1989) have indicated that aQ +/a + and aNa+/r H+ of midoceanic ridge hydrothermal fluids is controlled by clinozoisite, Ca-feldspar, and Na-feldspar. In addition to these assemblages, calcite is in equilibrium with fluids. Therefore, we can derive the /CO2 temperature relationship from the following equilibrium relations. 

The SFE process was carried out in a JASCO system. For each run, which lasted for an hour, 0.5g of the as-synthesised HMS was being loaded into the extraction cell housed in an oven. The system uses a HPLC and a syringe pump for pumping liquid CO2 and the modifier (methanol) respectively so as to build up the system pressure. The desired system pressure was set and controlled by a back pressure regulator while the system temperature was set and controlled by the temperature controller attached to the oven. The extracted amine surfactant is collected in a vial placed at the outlet of the back pressure regulator. 

Figure 3. A block diagram showing the electro-optical components of the fast response ln-situ CO2 sensor. The illustration shows a specific arrangement of the components identified in Figure 2. Temperature controlled regions are shown within dashed lines.

CM imposes specific constraints anatomic integrity of the berries and healthy fruit as well as special requirements for harvesting, transportation, and temperature control. It also requires a CO2 saturated atmosphere at the beginning and throughout the first step of fermentation. 

Figure C.2. Photograph of the supercritical fluid system used for nanoparticle synthesis. Shown is the 300-mL high-pressure reactor (A), with pressure/temperature controllers (B). The system is rated for safe operation at temperatures and pressures below 200°C and 10,000psi, respectively. The vessel may be slowly vented, or exposed to a dynamic CO2 flow, using a multiturn restrictor valve (C), which provides a sensitive control over system depressurization, allowing for the collection of C02-solvated species in the stainless steel collector (D). For deposition using the rapid expansion of tlie supercritical solution (RESS), nanoparticles were blown onto a TEM grid that was placed under the stopcock below D. Also shown is the cosolvent addition pump (E) used for the synthesis of aluminum oxide nanoparticles, capable of delivering liquids into the chamber against a back-pressure of <5,000 psi.

Up to now, only a few physical parameters such as temperature, pressure, and agitation, or basic chemical parameters such as pH, dissolved oxygen and CO2, are controlled on-line on a routine basis. Other important parameters, such as concentration of biomass, reaction products, substrates, and inhibitors, are more difficult to measure on-line, since suitable systems for their measurements have to fulfil strict requirements of selectivity, reliability, robustness, suitable detection range, and easy maintenance. 

A typical supercritical fluid extractor includes a supercritical fluid (most often CO2 or CO2 with an organic modifier) source, a means of pressurizing the fluid, a pumping system (for the liquid CO2), an extraction thimble, a device to depressurize the supercritical fluid (flow restrictor), an analyte collection device, temperature-control systems for several zones, and an overall system controller. 

A schematic drawing of the main parts of the SFC system is shown in Fig. 2. It consists of a high-pressure pump for pressurizing and delivering the solvent, usually CO2, connected to an oven, generally a modified gas chromatograph used as the temperature controller for the SFC column. The injector should introduce small sample volumes into the column and a restrictor is placed between the end of the column and the detector to maintain the mobile phase in the supercritical state. A detailed description of each part of the system follows. 

MC medium or HD medium were used for culturing Chlorella sp. UKOOl. Cells were placed in a flat culture vessel with 2.5 cm thickness and with 100 ml medium. The vessels were placed in temperature controlled water bath and illuminated by projector lamps. CO2 enriched air was aerated into culture at the flow rate of 100 ml/min (1 wm). 

Methanol synthesis from CO2 and H2 has received much attention as one of the most promising processes to convert C02 into chemicals. Gas-phase methanol synthesis process should recycle a large quantity of unconverted gas and furthermore the single pass conversion is limited by the large heat release in the reaction. Liquid-phase methanol synthesis in solvent has received considerable attention, since temperature control is much easier in the liquid phase than in the gas phase. 

Repeating the procedure for all critical control variables yields actuators as follows coolant flow rate for temperature, ammonia flow rate for pH, air flow rate for DO and dissolved CO2, stirrer speed for homogeneity control in the fermentor, steam flow rate for heat sterilization temperature control and stirring duration for homogeneity in the mixing tank. 

Boom, A., Marchant, R., Hooghiemstra, H., Siiminghe Damste, J. S. 2002. CO2- and temperature- controlled altitudinal shifts of C4 and Ca-dominated grasslands allow... 

---