Vacuum pumps, capture

Several variations of air sparge procedures are currently in common use, with each designed for site-specific situations. Vacuum vaporization is accomplished by attaching a vacuum pump to the top of an in-well aeration system. The vacuum removes the vapors and also draws soil vapors from the vadose zone. The combination of air sparging and SVE can provide effective capture of vapors with a minimum of wells. 

Fig. 19.4 Aspects of optimisation of the pervaporation process, apart from the membrane material 1 module design for optimum upstream and downstream conditions 2 condensation temperature(s) or aroma capture strategy 3 vacuum applied and type of vacuum pump. All aspects of the optimisation are interdependent in pervaporation and therefore need to be tackled as a whole, rather than individimlly...

Backstreaming can be one of the main limitations for mechanical pumps to achieve a better vacuum. Because molecular sieve and Micromaze traps are so efficient at capturing (and not releasing) vapors, Strattman experimented with a Micromaze foreline trap to trap the hydrocarbon oils from a mechanical pump. After proper baking and cooling, he was able to achieve pressures of 10 5 torr consistently with only a mechanical vacuum pump. 

Fig. 4.8. A summary of the three steps of the parylene deposition process. Parylene-C is shown. First, the stable dimer is vaporized at approximately 170°C, and diffuses into the cracker, which is held around 700°C. The cracker breaks the dimer into two reactive monomer units which diffuse into the deposition chamber and condense into a fully reacted polymer at room temperature. Unreacted material is captured in a cold trap to protect the vacuum pump, and the deposition process occurs at approximately 10-50mtorr for parylene-C.

Whether the emission source is a vacuum-pump discharge vent, a gas chromatograph exit port, or the top of a fractional distillation column, the local exhaust requirements are similar. The total airflow should be high enough to transport the volume of gases or vapors being emitted, and the capture velocity should be sufficient to collect the gases or vapors. 

Figure 2.8 Example of carbon dioxide separation from power plant flue gas using a two-step membrane process with two options for managing the permeate from the second membrane step. In Option 1 purple double-dotted lines), air is used directly in the burner while a vacuum pump creates partial pressure driving force in the second membrane step with return of the second step permeate to front of membrane process. In Option 2 blue dashed lines), the combustion air is used as a countercurrent permeate sweep gas in the second membrane step. Adapted from Figs. 11 and 12 in Merkel TC, Lin H, Wei X, Baker R. Power plant post-combustion carbon dioxide capture an opportunity for membranes. J Membr Sci 2010 359(1—2) 126—139.

The installation of a capture box will be required for those work place layouts where the floor drain is located in the same room as the sterilizer or in a room where workers are normally present. A capture box is a piece of equipment that totally encloses the floor drain where the discharge from the sterilizer is pumped. The capture box is to be vented directly to a non-recirculating or dedicated ventilation system. Sufficient air intake should be allowed at the bottom of the box to handle the volume of air that is ventilated from the top of the box. The capture box can be made of metal, plastic, wood or other equivalent material. The box is intended to reduce levels of EtO discharged into the work room atmosphere. The use of a capture box is not required if (1) The vacuum pump discharge floor drain is located in a well ventilated equipment or other room where workers are not normally present or (2) the water sealed vacuum pump discharges directly to a closed sealed sewer line (check local plumbing codes). 

BiopUes are variants of landfarms that permit treatment conditions to be more directly controlled. Also known as soil-heaping operations, biopiles use less land area and produce fewer air emissions than landfarms. Volatile compounds lost from biopUes are readily captured and treated, a major advantage of this technology (Bossert and Compeau 1995). To produce a biopile, soil is excavated and then mounded and covered by a plastic sheet within a lined treatment cell. An internal system of perforated pipes is placed within the pile and used to draw air in by means of vacuum pumps. Air also may be blown into... 

Adsorption pump, vacuum (vacuum technology) A capture-type vacuum pump that pumps by cryocondensation or cryotrapping on a surface of temperature less than — 150°C. See also Vacuum pump. 

Roots blower (vacuum technology) A compression-type mechanical pump that uses lobeshaped interlocking rotors to capture and compress the gas. The roots pump uses tight mechanical tolerances for sealing (no oil) and so is sometimes classed as a dry pump. See also Vacuum pump. 

Sputter-ion pump A capture (getter) pump in which the gettering material is continuously being renewed by sputter deposition. See also Vacuum pump. 

Vacuum pump (vacuum technology) A device for reducing the gas pressure in a container to less than the ambient gas pressure. The vacuum pump can operate by capturing and holding the gases or by compressing and expelling them. 

Vacuum pump, cryopump A capture-type pump that operates by condensation and/or adsorption on cold surfaces. Typically there are several stages of cold surfaces and one of the stages will have a temperature below 120 K. See also Cryopanel Cryosorption pump. 

Vacuum pump, ion pump A capture-type vacuum pump where a getter material is deposited by sputtering and gaseous ions are accelerated to the reactive surface to react with the surface or be physically buried in the depositing material. Also called a Getter ion pump. 

Vacuum pump, sorption pump A capture-type vacuum pump that operates by cryocon-densation of gases on a large-adsorption-area, cryogenically cooled (< — 150°C) surface. 

Third, what is the corresponding membrane surfaee area This variable, together with compressors and/or vacuum pumps, will play a key role in the eapital expenses (CAPEX) of the process. A design challenge takes place here, since an interplay between the operating eonditions (pressure difference in the module) and the corresponding surface area has to be addressed here, in order to minimize the overall capture cost. The membrane productivity (i.e. permeance), which includes the intrinsic permeability and effective active layer thickness obviously plays a key role here. This point will be discussed afterwards. 

Figure 2.8 Influence of membrane selectivity on energy requirement for 10% and 20% CO2 content in feed mixture. Operating conditions vacuum pumping. Separation targets capture ratio R) 80%, CO2 purity (y) 0.8.

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