Gas purging

This eliminates the vapor space but sealing the edge can be a problem. Double seals can help and sometimes a fixed roof is also added above the floating roof to help capture any leaks from the seal. However in this case, the space between the fixed and floating roof now breathes and an inert gas purge of this space would typically be used. The inert gas would be vented to atmosphere after treatment. 

Stea.ming Retjuirements. The steaming of fixed beds of activated carbon is a combination of thermal swing and displacement purge swing. The exothermic heat released when the water adsorbs from the vapor phase is much higher than is possible with heated gas purging. This cycle has been successhiUy modeled by equiUbrium theory (128). 

Gas Chromatography. Gas chromatography is a technique utili2ed for separating volatile substances (or those that can be made volatile) between two phases, one of which is a gas. Purge-and-trap methods are frequently used for trace analysis. Various detectors have been employed in trace analysis, the most commonly used being flame ioni2ation and electron capture detectors. 

Unreacted phosgene is removed from the cmde chloroformates by vacuum stripping or gas purging. Chloroformates of lower primary alcohols are distillable however, heavy-metal contamination should be avoided. As stated earlier, chloroformates generating a stable carbonium ion on decomposition, ie, secondary or tertiary chloroformates or henzylic chloroformates, are especially unstable in the presence of heavy metals and more specifically Lewis acids and, hence, should be distilled at as low a temperature and high vacuum as possible. 

A purge-swing adsorpfion cycle is usually considered to be one in which desorpfion takes place at the same temperature and total pressure as adsorpfion. Desorpdon is accomplished either by pardal-pressure reduction using an inert gas purge or by adsorbate displace-... 

Leakage from Use adequate shaft sealing (mechanical or multimill ignited by pie gas purged lip or chevron seals). Harden spark or hot shafts in seal area surface., pressure tight flexible connections and clamps on mill inlets and outlets Provide adequate fixed fire protection where appropriate CCPS G-23 CCPS G-29 NFPA 13 NFPA 15 NFPA 16... 

The bubbles shapes in gas purging vary from small spherical bubbles, of radius less than one centimen e, to larger spherical-cap bubbles. The mass transfer coefficient to these larger bubbles may be calculated according to the equation... 

Figure 15-4. Seai oii system, gas vent inert-gas purge...

Blakey and Orlando give useful methods for determining inert gas purging requirements. 

If movable stator blades were used, the linkage should be checked for binding and wear. If a clean gas purge was used to keep the linkage clean and dry, the source and supply lines should be inspected to make sure they all work as intended when the compressor is restarted. 

The gas is non-flammable, and is used for inert gas purging. Because it is 1.5 times heavier than air it may accumulate at low level. The general handling precautions are those in Table 9.3. 

Sharp separation between the mother and wash solutions is required O The cake tends to crack smoothing avoids the wash liquid, air or gas purge from by- passing. 

Flashback protection is required for H2S flaring systems, either by water seal or continuous gas purge. If a water seal is used, special requirements apply to the disposal of the effluent seal water. In the case of an HjS flaring system handling a flow of HjS which in uninterrupted throughout the period that a plant is in operation, and which stops only when the producing plant is shutdown, then flashback protection is not required. However, steam or inert gas connections are required to permit purging the flare line startup and shutdown. 

The suction shut-down bypass valve is used to purge the piping system of air prior to compressor start-up. This valve is small to prevent high gas purge rates from spinning the impellers. 

Gaseous CO2 is extensively used to carbonate soft drinks and this use alone accounts for 20% of production. Other quasi-chemical applications are its use as a gas purge, as an inert protective gas for welding, and for the neutralization of caustic and alkaline waste waters. Small amounts are also used in the manufacture of sodium salicylate, basic lead carbonate ( white lead ), and various carbonates such as M2CO3 and M HC03 (M = Na, K, NH4, etc.). One of the most important uses of CO2 is to manufacture urea via ammonium carbamate ... 

Purging may be by either the direct or slug method, and may involve the use of an intermediate inert gas purge. At all stages, the vent point is sampled and the purge is deemed satisfactory when certain criteria are met. 

Inert to gas, purge complete with combustible levels greater than 90 per cent. 

Fuel gas to fuel gas purging The purge may be carried out by burning the gas under supervision on an appliance or appliances. If the two fuel gases have different burning characteristics and Wobbe numbers, correct burner selection is important. 

The chief engineer calls you into his office and asks you to prepare an outline design for an inert gas purging and blanketing system for the reactors and other equipment, on shutdown. This request arises from a report into an explosion and fire at another site manufacturing a similar product. 

Hazards attendant on use of ethylene oxide in steriliser chambers arise from difficulties in its subsequent removal by evacuation procedures, owing to its ready absorption or adsorption by the treated material. Even after 2 evacuation cycles the oxide may still be present. Safety is ensured by using the oxide diluted with up to 90% of Freon or carbon dioxide. If high concentrations of oxide are used, an inert gas purge between cycles is essential [7], The main factors in safe handling... 

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