Non-condensable gas

Just inside the shell of the tube bundle is a cylindrical baffle F that extends nearly to the top of the heating element. The steam rises between this baffle and the wall of the healing element and then flows downward around the tubes. This displaces non-condensed gases to the bottom, where they are removed at G. Condensate is removed from the bottom of the heating element at H. This evaporator is especially suited for foamy liquids, for viscous liquids, and for those liquids which tend to deposit scale or crystals on the heating surfaces. Vessel J is a salt separator. 

Evaporators, Horizontal-Tube Type - The basic horizontal-tube evaporator is illustrated in Figure 12. The body of this evaporator is the liquor compartment and is in the form of a vertical cylinder. It is closed, top and bottom, with dished heads, although the bottom may be conical. The lower body ring is provided on opposite sides with steam compartments, closed on the outside by cover plates and on the inside by tube sheets. Between these tube sheets are fastened a number of horizontal tubes. The two steam chests with their connecting mbes form the steam compartment, and the tube wall heating surface. Steam is introduced into one steam chest and as it flows through the tubes it washes non-condensed gases and condensate ahead of it, so that these are withdrawn from the opposite steam chest. 

In ordinary operation only condensate and non-condensed gases are removed from the exit steam chest. The connection for feeding the liquid to be evaporated may be attached to the body at any convenient point (D), but the discharge for thick liquor is usually in the center of the bottom (E). Suitable brackets are cast on the bottom to rest on the supporting steel. Most evaporators are provided with sight glasses. 

Placing the fluid through the tubes is a consideration when special alloy materials aie needed for corrosion control, because the materials would be needed only on the tubes. If the corrosive material is in the shell, both the tubes and the shell would need to be protected with special alloy. It the fluid is at high pressure, it should be put in tubes because tubes can contain high pressure much more cheaply as they are much smaller in diameter than the shell. The low-pressure fluid would be in the shell. If the fluid contains vapor and non-condensable gases, heat transfer will be greater if it is placed in the tubes. If the fluid is scale forming it should be in the tubes, which can be reamed out. 

Based on handling pure liquids, without entrained air or other non-condensable gases, which adversely affect the pump performance. 

Non-condensable gases released from gases originally injected into the process for purge, products of reaction, etc. 

Non-condensable gases, usually air, released from direct contact water injection. 

Fj = F + Vj = mols of feed plus mols of non-condensable gases From Henry s Law ... 

Vt = V + Vs = mols of vapor formed plus mols non-condensed gases... 

Xf = mol fraction of a component in feed Xf = mol fraction of any component in the feed. Ft where Xf = F Xf/F( for all components in F for the non-condensable gases, Xf = V /Ft F = mols of feed entering flash zone per unit time contains all components except non-condensable gases Ft=F-tV,... 

Vt = V + Vs mols of vapor at a specific temperature and pressure, leaving flash zone per unit time Vs = mols of non-condensable gases entering with the feed, F, and leaving with the vapor, V, per unit time... 

For the simplified case of a mixture free of non-condensable gases, see Equation 8-23A, where Xf = Xf. 

Feed rate to tower, lb mols/hr or, mols of feed, (batch distillation) entering flash zone/time all components except non-condensable gases Factor for contribution of other feed flow to minimum reflux Mols of liquid feed Mols of vapor feed... 

Vg = Vapor flowrate up stripping section of tower, lb mols/hr or mols non-condensable gases entering wath feed, F, and leaving with vapor, V/time... 

Baasel, W. D. and J. S. Smith, A Mathematical Solution for the Condensation of Vapors from Non-Condensing Gases in Laminar Elow Inside Vertical Cylinders, AIChE Journal, Nov. (1963) p. 826. 

The presence of non-condensable gases in steam systems (e.g. air and CO2) will reduce the partial pressure of the steam, and hence its temperature, thus affecting the output of the appliance. A further adverse effect is the presence of a non-condensable gas at the inside surface of a heat emitter. These impede condensation and, hence, heat output. It is therefore imperative that suitable means are provided to prevent formation of CO2 and to evacuate all gases from the system. 

Device used to vent non-condensable gases from a boiler during startup and shutdown procedures. 

A type of steam-heated open FW heater containing a vent and vent condenser and employed for the elimination of non-condensable gases. Depending upon deaerator design and operation, it is sometimes possible to reduce FW dissolved oxygen (DO) levels to below 0.005 cc/1 (7.2 ppb). 

The Okuaizu geothermal system is characterized by high temperatures (maximum 340°C), high salinity (about 2 wt% total dissolved solids (TDS)) and large amounts of non-condensable gases (1 wt% CO2 and 200 ppm H2S). The pH of the hydrothermal solution measured at 25°C is 6.44 (Table 2.6). However, the pH of the original fluid in the reservoir is computed to be 4.05. This pH as well as alkali and alkali earth element concentrations are plotted near the equilibrium curve of albite, K-mica, anhydrite and calcite (Fig. 2.19) (Seki, 1991). 

COLBURN, A. P. and Hougen, O. A. (1934) Ind. Eng. Chem. 26, 1178. Design of cooler condensers for mixtures of vapors with non-condensing gases. 

Battistelli A., Calore C., et al. The simulator TOUGH2/EWASG for modeling geothermal reservoirs with brines and non-condensible gases. 1997 Geothermics 26(4) 437-464. 

The system can measure non-condensable gases to greater than 3% error when the final pressure is 460 to about 700 Torr. Note that the TorrSeal o-ring was tested to 50 psig at room temperature. The expectation is to run the unit where the maximum expected pressure is below 1000 Torr. 

The organic compounds are combustible and can be divided into volatiles (gases) and non-volatiles (solids), see Figure 54. The volatile part is, in turn, divided into condensible and non-condensible gases. The condensible volatiles are termed tars and the non-condensibles volatiles are also called volatile organic compounds (VOCs). The non-volatile organics are referred to as chars. [9]... 

The vacuum system must be able to attain the required pressures reliably despite these high gas loads. In the example shown, the system is evacuated with a combination of a backing and Roots pump. A diffusion pump along with a cold surface forms the high vacuum pump system. The cold surfaces pump a large portion of the vapor and volatile substances emitted by the plastic parts while the diffusion pump basically removes the non-condensable gases as well as the noble gas required for the sputter process. 

Gas ejectors (an ejector is a vent for removing non-condensable gases from the condensing unit located downstream from the turbine. Condensate from the cooling towers is pumped to the condenser unit to condense the steam leaving the turbine. In this way, low pressure is created downstream from the turbine, which leads to improved efficiency to generate electric... 

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