Stepped evacuation process

Moisture is removed from the canister using a vacuum drying system or forced helium dehydration system. For canisters without high bum-up fuel, the vacuum drying system may be connected to the canister and used to remove all liquid water from the canister in a stepped evacuation process. A stepped evacuation process is used to preclude the formation of ice in the canister and vacuum drying system lines. The internal pressure is reduced to below 3 torr and held for 30 min to ensure that all liquid water is removed. 

Having defined and gathered data adequate for an initial reserves estimation, the next step is to look at the various options to develop the field. The objective of the feasibility study is to document various technical options, of which at least one should be economically viable. The study will contain the subsurface development options, the process design, equipment sizes, the proposed locations (e.g. offshore platforms), and the crude evacuation and export system. The cases considered will be accompanied by a cost estimate and planning schedule. Such a document gives a complete overview of all the requirements, opportunities, risks and constraints. 

Fig. 5. Equipment foi surface treating plastic components. Parts ate loaded into one of the two lower chambers which is then evacuated to remove most of the air. This chamber is then flooded with a dilute mixture of fluorine and nitrogen which is made and stored in the upper chamber. After the treatment is completed, the fluorine mixture is pumped back up to the upper chamber for storage and the lower chamber repeatedly flooded with air and evacuated to remove any traces of fluorine gas. Two treatment chambers are cycled between the loading/unloading operation and the treatment step to increase equipment output. The fluorine—nitrogen blend may be used several times before by-products from the treatment process begin to interfere. AH waste...

In the original process for the positive electrode, the plaques were placed in a metal vessel, which was evacuated to <5.3 kPa (40 mm Hg), and a nearly saturated solution of nickel nitrate (density 1.6 g/mL) admitted. After a 5—15 min soaking period, the plaques were transferred at 101 kPa (1 atm) to a polarizing unit where they were cathodicaHy polarized in hot caustic solution. After polarization the plates were washed and dried. These four steps were repeated four or five times until the desired weight gain of active material was achieved. 

Historically, measurements have classified ambient hydrocarbons in two classes methane (CH4) and all other nonmethane volatile organic compounds (NMVOCs). Analyzing hydrocarbons in the atmosphere involves a three-step process collection, separation, and quantification. Collection involves obtaining an aliquot of air, e.g., with an evacuated canister. The principal separation process is gas chromatography (GC), and the principal quantification technique is wdth a calibrated flame ionization detector (FID). Mass spectroscopy (MS) is used along with GC to identify individual hydrocarbon compounds. 

For food and pharmaceutical applications, the microbial count must be reduced to less than 10,000 viable cells per g exopolysaccharide. Treatment with propylene oxide gas has been used for reducing the number of viable cells in xanthan powders. The patented process involves propylene oxide treatment for 3 h in a tumbling reactor. There is an initial evacuation step before propylene oxide exposure. After treatment, evacuation and tumbling are alternated and if necessary the reactor is flushed with sterile nitrogen gas to reduce the residual propylene oxide level below the Food and Drug Administration permitted maximum (300 mg kg 1). The treated polysaccharide is then packaged aseptically. 

Alternatively, data points can be collected in the decreasing pressure mode . This procedure is usually applied for the quantification of activated adsorption processes (Reuel and Bartholomew, 1984), such as the adsorption of H2. After the pretreatment of the sample (usually after reduction or reaction, and evacuation for a certain period to remove all the adsorbed surface species) the temperature is lowered to the temperature of measurement. First, a known amount of adsorbate gas is added to the reactor. Subsequently, the pressure in the catalyst compartment is lowered stepwise by expansion of the gas into the repeatedly evacuated reference volume. The adsorbed amount of gas can be calculated for each step. From this procedure, the monolayer capacity of the catalyst can be evaluated. 

In a case of the PCX absorption curve after evacuation, the system must be heated up to a test temperature and thermally stabilized. Then by gradually increasing pressure we will observe hydrogen absorption related to a particular pressure of hydrogen. It is important that the time of visible pressure change at every step is closely connected with the kinetics of process at an applied temperature. 

The first step of the process is performed in a separate, dedicated building. The drums of arsenic trioxide are opened in an air-evacuated chamber and automatically dumped into 50% caustic soda. A dust collection system is used. The drums are carefully washed with water, the washwater is added to the reaction mixture, and the dmms are crushed and sold as scrap metal. The intermediate sodium arsenite is obtained as a 25% solution and is stored in large tanks prior to further reaction. In the next step, the 25% sodium arsenite is treated with methyl chloride to produce the disodium salt DSMA (disodium methanearsenate, hexahydrate). This DSMA can be sold as a herbicide however, it is more generally converted to MSMA, which has more favorable application properties [8]. 

Often a vacuum process covers several of the regions quoted here. In batch drying the process can, for example (see Fig. 2.74), begin in region A (evacuation of the empty vessel) and then move through regions B, C, and D in steps. Then the course of the process would be as follows ... 

If the sample was pretreated at temperatures above 573 K, i.e. in the 673 - 1073 K range, other process parameters had to be chosen in order to obtain optimal H/D exchange. Better results are obtained with increasing temperature in the adsorption step. The choice of adsorption and evacuation temperatures was limited to 673 K, by the glass material of the experimental apparatus. Figure 3.6 shows the FTIR-PAS spectra of silica gel pretreated at 973 K, before deuteration (fig. 3.6a), after deuteration at room temperature (fig 3.6b) and at 673 K (fig 3.6c). 

For GAS experiments the autoclave is filled with the non-volatile component and closed. Then, solvent is drawn into the evacuated vessel. With a pneumatically driven compressor a thermostated buffer vessel is filled with gas. From there it enters the high-pressure cell through the filter or the gas inlet at the top. Thus, the amount of gas can be determined by pvT measurement. Very fast pressure built-up rates can be achieved. After precipitation, the autoclave is placed in vertical position. The solution is then filtered and drained through the bottom valve. During that process the pressure is held constant by adding gas from the top. After the filtration step the solids can be washed with additional gas to remove any residual solvent. 

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