Headers hydrogen header

Figure 13 demonstrates a typical operation cyclogram of the unit. This example corresponds to the volume of the gas header (hydrogen collector) equal to 100 cm3 and the residual hydrogen storage capacity in the storage equal to 130 / (60% of the maximum value). 

It is possible to run one header for each service to cover both rows of cells. It is common practice to do this for the gases. A frequent variation, included in Fig. 8.1, is to run two separate hydrogen headers (usually carbon steel), which can serve as structural supports for the saddles that hold a single chlorine header (usually FRP). Liquid headers more frequently are installed in pairs. One reason for this is the reduction of leakage currents, which are the topic of Section 8.3.2.2. 

IB. Hydrogen. Low-pressurehydrogeniseasily handled, but designers and operators should be aware that there is always liquid in a hydrogen header. At its most iimocuous, this is simply water that condenses as the gas cools. Entrained liquor from the cells can make the liquid in the pipe conductive. In a mercury-cell plant, there is the added complication of liquid mercury condensing in the lines. 

Hydrogen headers should be designed to drain from known points to collecting vessels, from which the liquid can be handled properly. Design of the receiving system should recognize that entrained hydrogen gas may be released over time, and there should be some way to vent it safely. 

Since the differential pressure between the two gas headers is so important, neither gas should be considered independently of the other. This discussion, therefore, is incomplete without reading Section 11.4.2.1 on the hydrogen header. 

A. Operation Near Atmospheric Pressure. The simplest approach to hydrogen header control at very low pressure uses large water-sealed vents designed to maintain a fairly precise back-pressiure with little or no fluctuation. Figure 11.35 shows such a vent. Section 9.1.10.1 gives design details for this type of system as a pressure-relief device with little heed to gas flow distribution. For more precise control, it is important to distribute the gas as small bubbles over a wider area of the water seal (10-20 nun deep) in order to provide minimum pressure drop and fluctuation in flow. 

FIGURE 11.35. Hydrogen header pressure control (atmospheric pressure). 

C. Safety Systems. The cell room hydrogen header should be automatically purged with nitrogen at high flow rate for a fixed time whenever the rectifiers shut down (Fig. 11.40). This ensures that condensation of water vapor does not lower the header... 

Diversion to Compressor System. Section 11.4.2.1 discussed the hydrogen header pressure control arrangement. It did not cover the mechanism for diversion of the gas to the compression system. 

B. Hydrogen Users Priority Control. While the discussion immediately above assumed that there was only one user of hydrogen, there are frequently several. Even with only one user, shutdown or curtailment of the offtake can force some of the hydrogen to be vented or diverted for use as fuel. The total demand by multiple hydrogen users, on the other hand, also can exceed the rate of supply. It is, therefore, the usual practice to establish user priorities by staging the hydrogen header pressure control system (Fig. 11.44). 

FIGURE 11.4S. Diaphragm-cell hydrogen header pressure control. 

The circulation tank operates at the pressure of the cell-room hydrogen header. When the rectifiers stop for any reason, nitrogen enters the vapor space of the tank to prevent development of an explosive environment or a vacuum due to vapor cooling. Excess gas vents through the hydrogen seal pot. The tank may be vertical, as shown, or horizontal. 

Since the circulation tank rides on the hydrogen header, as in Fig. 11.49, pressure compensation is necessary for accurate measurement of the level. The level instrument uses a dual remote diaphragm seal system on a d/p cell. The lower diaphragm is connected... 

The rate of flow of the nitrogen purge in the hydrogen header is an important process design factor. Considerations include ... 

Cell room acid addition rate Electrolyzer acid addition rates Caustic export flow rate Cell room outlet caustic temperature Electrolyzer outlet caustic temperatures Chlorine header pressure Hydrogen header pressure Differential pressure between gas headers... 

The flic presented contains 11 data items. The header lines arc property names as used by CACTVS [64, 65], and arc sufficiently self-descriptive. For example, E NHDONORS is the number of hydrogen bond donor.s, E SM1LES" is the SMILES string representing the structure of sulfamidc, and E LOGP is the logP value (octanol/water partition coefficient) for this substance. 

Cathodic protection of water power turbines is characterized by wide variations in protection current requirements. This is due to the operating conditions (flow velocity, water level) and in the case of the Werra River, the salt content. For this reason potential-controlled rectifiers must be used. This is also necessary to avoid overprotection and thereby damage to the coating (see Sections 5.2.1.4 and 5.2.1.5 as well as Refs. 4 and 5). Safety measures must be addressed for the reasons stated in Section 20.1.5. Notices were fixed to the turbine and the external access to the box headers which warned of the danger of explosion from hydrogen and included the regulations for the avoidance of accidents (see Ref. 4). 

Verify that increased hydrogen content will not impact any heaters. Depending on the header design, it could be a problem if it all goes to the same branch of the header. 

In a printed circuit board etching line using copper(II) chloride solution, 45 wt% hydrogen peroxide solution was used to recover the copper salts. The peroxide header tank became contaminated with trace amounts of the etching solution, and catalytic decomposition of the peroxide led to a pressure burst of the tank. 

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