Atmospheric discharge

This is the release of vapors and gases from a PRV and a depressuring system to tile atmosphere. The following points must be considered before deciding on any discharge to fhe atmosphere  

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In offsite locations, thermal expansion PR valves may discharge to a flare header upstream of a knockout drum, if available, or to the equipment (e.g., a tank) on the opposite side of one of the blocking-in valves, or to the atmosphere. Atmospheric discharges must be at grade level in a safe location... 

PR valves discharging vapors which do not fall into the above categories but which would be significant contributors to atmospheric pollution. Such releases should not normally be used to size the closed system but should be tied in up to the limit of its capacity. The order of preference for tying in is (1) malodorous vapors, (2) unsaturated hydrocarbons, (3) saturated hydrocarbons. If local requirements do not permit such atmospheric discharges, it will be... 

PR valves where atmospheric discharge is permissible, but connection to an adjacent closed header (provided that capacity is available) is less costly than an atmospheric discharge line to an acceptable location. 

Back Pressure - The combined atmosphere discharge system must be designed to comply with the superimposed back pressure limitations. 

The vapor outlet may be discharged either to the atmosphere or to a flare. Atmospheric discharge may be considered, provided that a safe location can be achieved, as defined by the following ... 

Electrostatic precipitators (ESP) and wet gas scrubbers (WGS) are widely used to remove particulates from the FCC flue gas. Both can recover over 80% of filtrable solids. An ESP (Figure 10-6) is typically installed downstream of the flue gas heat recovery (prior to atmospheric discharge) to minimize particulate concentration. If both low particulate and low SO requirements are to be met, a wet gas scrubber such as Belco s (Figure 10-7) should be considered. If SO removal... 

Nerve gas is to be thermally decomposed by oxidation using a large excess of air in a 5-cm i.d. tubular reactor that is approximately isothermal at 620°C. The entering concentration of nerve gas is 1% by volume. The outlet concentration must be less than 1 part in lO by volume. The observed half-life for the reaction is 0.2 s. How long should the tube be for an inlet velocity of 2m/s What will be the pressure drop given an atmospheric discharge ... 

Fog Condensation—The Other Way to Make Little Droplets For a variety of reasons, a gas or vapor can become supersaturated with a condensable component. Surface tension and mass transfer impose barriers on immediate condensation, so growth of fog particles lags behind what equilibrium predicts. Droplets formed by Fog condensation are usually much finer (0.1 to 10 pm) than those formed by mechanical breakup and hence more difficult to collect. Sometimes fog can be a serious problem, as in the atmospheric discharge of a valuable or a hazardous material. More commonly, fog is a curiosity rather than a dominating element in chemical processing. 

There are different ways of processing the effluent of a pressure relief [35], One is atmospheric discharge, which is rare as only harmless effluents can be so used. The second is flaring or incineration, which is only sparsely available in fine chemicals or pharmaceutical industries. Total containment is another approach, but it requires pressure resistant equipment (see Section 10.5.2). Thus, the most used is partial containment... 

Not all possible deficiencies are included in the above statistical analysis. There are also concerns about items such as excessive flare radiation levels, inadequate knockout drums, poorly designed quench systems, discharge of toxic fluids to atmosphere, discharge of combustible or toxic liquids and gases to atmosphere and a general lack of process safety information upon which to base a safe pressure relief system design. Therefore, it could be stated that the actual total deficiency rates reported may even be understated. 

The main pathways of the POP pesticides that enter water include drift during field application, air-water diffusion, dry and wet deposition from the atmosphere, discharges of polluted wastewater, and exchange between groundwater and sediments. Water, suspended particles, living species, and sediments are often monitored separately. In this section, pollutants in the water phase and pore water are summarized. Suspended particles and sediments will be described in Section 3.3.4. 

Example 9.1 on the partial oxidation of o-xylene used a pseudo-first-order kinetic scheme. For this to be justified, the oxygen concentration must be approximately constant, which in turn requires low oxygen consumption and a low pressure drop. Are these assumptions reasonable for the reactor in Example 9.1 Specifically, estimate the total change in oxygen concentration given atmospheric discharge pressure and aout = 21 g/m3. Assume = 0.4. 

Atmospheric discharges from wet process phosphoric acid plant 0.03-0.2 0.0009-0.06 0.0001-0.010 0.03-0.3... 

Atmospheric discharges from a uranium recovery plant 0.05 0.007 — 0.06... 

The review of atmospheric discharges has indicated that earlier figures for emissions, particularly for particulates, in the earlier years of plant operation were... 

PCBs are another well known POP that has accumulated in the environment with reported adverse effects in wildlife. Previous discharge of PCBs into streams, rivers, and lakes, disposal in landfills, and atmospheric discharge has resulted in widespread environmental distribution of PCBs. The manufacturing of PCBs also may result in the production of by-products, such as dioxins and furans, which also... 

FPD.5 ATMOSPHERIC DISCHARGE CALCULATION Since fV < 0.222, Stokes s law applies, and... 

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