Atmospheric releases, avoidance

A portion of the combustion gases released from the hot oil system is used as sweep gas in the thermal processor. The warm sweep gas (i.e., 700°F and very low oxygen content) removes the organics from the processor. Sweep gas is introduced to maintain an exhaust gas temperature from the processor of about 350°F. The sweep gas also provides an inert atmosphere to avoid exceeding the lower explosive limit (LEL) of contaminants within the thermal processor and downstream equipment. The remaining portion of combustion gases from the oil system is released for atmospheric discharge. 

Safety-related layout of the plant comprises double-walled pipes in product gas carrying ducts and deployment of isolation valves. Released process gases should be routed immediately into the atmosphere to avoid accumulation inside the reactor building. 

Avoidance of Atmospheric Releases—The release or exposure of combustible vapors or liquids to the operating environment should not be allowed. Relief valve oudets should be connected to a flare or blowdown header, pump seal leakages should be immediately corrected, and vibration stresses on piping components should be avoided. 

Atmospheric dispersion of any rupture disc discharges would result in a vapor cloud with gas concentrations above the lower explosive limit. Thus, such releases must be avoided, and other mitigation procedures should be used. However, as an additional check on the situation, mapping of the potential gas cloud versus the plant layout was conducted with the conclusion that no ignition sources were likely to be present in the region where the vapor cloud would be flammable. 

When a pipeline is to be placed in service, the air in it shall be displaced. In order to avoid the creation of a combustible mixture, a slug of inert gas shall be introduced between the hydrogen and air. The hydrogen gas flow shall then be continued without interruption until all the air and inert gas have been removed from the facility. The vented gases shall be monitored and the vent closed before any substantial quantity of hydrogen gas is released to the atmosphere. Dead-ended legs of the pipeline system that cannot be swept by inert gas must be pressure purged. 

The in situ generation of 2,3 BPG is accelerated by low atmospheric Po2, for example at high altitude. Lower Po2 at altitude could compromise tissue oxygenation so to avoid cellular hypoxia, 02 is released from haemoglobin. 

Unsteady State Diffusion. The apparatus, experimental procedures, and the computational procedures used to calculate the diffusion parameter D /r (where D is the diffusion coefficient and r is the diffusion path length) have been described in detail previously (6, 8). A differential experimental system was used to avoid errors caused by small temperature fluctuations. In principle, the procedure consisted of charging the sample under consideration with argon to an absolute pressure of 1204 12 torr (an equilibrium time of about 24 hours was allowed) and then measuring the unsteady state release of the gas after suddenly reducing the pressure outside the particles back to atmospheric. 

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