Inert-gas bleed

A rupture disk is a thin sheet of metal installed below the valve, intended to protect the relief valve from plugging. The rupture disk ruptures at the relief-valve-set pressure. A better approach to retard this plugging problem is to maintain a steam purge, or inert-gas bleed, below the relief valve to prevent the accumulation of solids below the valve. 

Insert a short needle through the septum of Schlenk tube B to make an inert gas bleed. 

From equation (17.6) we can see that open-loop pressure dynamics are essentially first order. Since in most cases the inert gas bleed and the vent flow are fiiirly small, the valve gains, SwjgIBBc and dwJdBc, tend to be small. Together with the first-order dynamics, this commonly leads to large controller gains (small proporticmal bands) and control valve saturation fcM" fairly small disturbances. 

Perhaps the most efficient and convenient methods for providing a supply of dry oxygen-free inert gas employs BTS catalyst (BASF) in conjunction with molecular sieves. The catalyst is a pelleted form of finely divided copper on an inert support and is used in a system like that shown in Figure 6.7. The nitrogen passes through molecular sieves, BTS catalyst, and another column of molecular sieves. The output gas will have an oxygen and water content each below 1 ppm in a carefully built system. The three-way stopcocks in the inlets are used to bleed the regulators and inlet lines when the cylinders are... 

Use an air or inert gas (nitrogen) capillary bleed during vacuum distillation (seep. 110). 

Column top pressure is controlled by a vent/bleed system i.e., inert gas is added if pressure is low, and gas from the reflux drum is vented if pressure is high. 

The gas mixture containing approximately 80vol% Hj is fed directly to the bioreactor. The CO2 gas is used as a carbon source for the bacteria. To achieve good mixing without introducing high shear forces, a gas-lift loop type reactor is used, as illustrated in Figure 4. The fresh H2 from the reformer is mixed with the recycle gas and is distributed over the riser surfaee of the reactor. A small amount of the gas recirculation flow is bled off to remove inert components (mainly N2). The gas bleed is used as fuel for the burner of the reformer system. 

Decanter Models in Aspen. Up to this point, we have been using the Decanter model in the simulations. It assumes that there are only two phases, both liquid, and that the decanter pressure is fixed at the specified design value (pressure does not change with temperature or composition). These assumptions do not reflect reality but appear to suffice for steady-state design. In a real decanter, there is a vapor space above the two liquid phases, and pressure will vary with compositions and temperatures unless an inert gas is used to keep a constant pressure via a vent-bleed split-ranged valve setup. 

SO that it can be cooled by air or water when it is necessary to freeze the eutectic. The lid itself carries a 9 in. deep cooling coil of stainless-steel piping, together with branches for evacuation, feeding of inert gas, and bleeding of excess gas pressure to atmosphere. Provision is also made for the attachment of a cable to the centre of the lid, which then passes over a pulley and is connected to a counter-weight. The position of the lid is then indicated by the movement of a pointer connected to the pulley. 

For a vacuum column with a small amount of inerts, the arrangement of Figure 3.10 may require an impractically small vent valve. In this event the arrangement of Figure 3.11, with a controlled bleed from the atmosphere (or source of inert gas), is better. 

In the one-stage process (Fig. 2), ethylene, oxygen, and recycle gas are directed to a vertical reactor for contact with the catalyst solution under slight pressure. The water evaporated during the reaction absorbs the heat evolved, and make-up water is fed as necessary to maintain the desired catalyst concentration. The gases are water-scmbbed and the resulting acetaldehyde solution is fed to a distUlation column. The tad-gas from the scmbber is recycled to the reactor. Inert materials are eliminated from the recycle gas in a bleed-stream which flows to an auxdiary reactor for additional ethylene conversion. 

If tars are formed (which happened in the trial with mixed PVC waste), it is necessary to apply a partial oxidation to convert these tars into gaseous products. Via a quench, HCl is recovered from the product stream which consists of fuel gas and HCl. After purification the HCl can be used for producing ethylene dichloride (EDC) via oxychlorination. The recovery of CI2 is more then 90%, in general 94%-97%. Inert materials in the feed, such as the chalk and metal stabilisers present in a PVC-formulation, are separated from the flue gas as fly ash or will be set free as a bleed from the circulating sand. 

Packed column widely used in gas chrpmatography is valuable for many routine analyses and necessary in certain cases. However, recent developments in the manufacture of open tubular fused silica columns have resulted in a new product, the large bore column, which provides much better resolution, an inert system with less bleeding, and shorter analysis lime. This offers a very superior alternative for packed column in most cases, and with the same convenience in application. They have already opened a new horizon in gas chromatography especially for routine analyses. 

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