Effluent Removal Systems

The most important aspect of the design is to ensure that effluent is withdrawn uniformly from within the tank. Options to be looked into are as follows  

Fixed decanters including submerged outlet pipes with automated siphon control valves or a moving device and floating weirs-type outlet can be available. Vendor shall give the details in the GA drawing. 

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The selection requirements for each of the components of the SCWO system for treating a variety of waste types comes from environmental regulations, waste characteristics, and cost and safety criteria. Similar to the bench-scale experimental design, the major components to be included in the SCWO design involve three main subsystems (influent introduction, reactors, and effluent removal systems). Other auxiliary systems such as heat exchangers and effluent exhaust systems must also be designed. In addition, for scale-up operations, the waste pretreatment and handling systems have to be considered. Fig. 10 shows a schematic of a complete system. 

Figure 4.5 Some Effluent Removal Systems (a) Liquid Scrubbers, (b) Thermal Decomposition-Pyrolisis Scrubber, (c) Combustion, Liquid, Catalysis Scrubber System...

The capital cost of most aqueous waste treatment operations is proportional to the total flow of wastewater, and the operating cost increases with decreasing concentration for a given mass of contaminant to be removed. Thus, if two streams require different treatment operations, it makes no sense to mix them and treat both streams in both treatment operations. This will increase both capital and operating costs. Rather, the streams should be segregated and treated separately in a distributed effluent treatment system. Indeed, effective primary treatment might mean that some streams do not need biological treatment at all. 

Carbon Dioxide Removal. The effluent gases from the shift converters contain about 17—19 vol % (dry) carbon dioxide (qv) which is ultimately reduced to a few ppm by bulk CO2 removal, followed by a final purification step. Commercial CO2 removal systems can be broadly classified as... 

A bleed from the scmbbing system is sent to a sour slurry stripper. The water is then clarified and can be recycled to minimize the volume of effluent to be biotreated and discharged or evaporated. The acid gas from the acid gas removal system and from the sour slurry stripper is fed to a Claus plant, where salable elemental sulfur (qv) is produced. For maximum sulfur recovery and minimal sulfur emissions, the Shell Claus off-gas treating process (SCOT) is used. 

As with particulate removal systems, it is apparent that many choices are available for removal of gases from effluent streams. Table 29-5 presents some of the factors that should be considered in selecting equipment. 

Failure of the utilities and ancillary systems occurs when one or more of tlie following is lost electric power, cooling water or otlier heal removal systems, steam or other heat supply systems, fuel, air, inert gas, or effluent disposal facilities. 

The recommended design procedure is also from Guidelines for Pressure Relief and Effluent Handling Systems (AIChE-CCPS, 1998). As with a horizontal separator, the assumed value of K is expected to be suitable for most vertical separators in emergency relief services. However, if it is necessary to remove droplets smaller than 300 to 600 pm, then lower values of K should be used. 

The PRH hydrolysate is discharged to a stirred tank, where the hydrolysis of agent is completed. Air is drawn through the PRH to remove volatile materials, and the gaseous effluent is passed through a CATOX, scrubber, and carbon filters prior to release to the plant s HVAC system. The solids, consisting of the washed munitions parts, go into the HDC that treats metal parts from the projectile agent removal system (Step 16), where they are decontaminated to a 5X level. 

Effluent type System configuration Removal Application status References... 

About 10% of the ethylene feed is converted to carbon dioxide. Therefore, a carbon dioxide removal system, usually hot potassium carbonate, is used to separate carbon dioxide from the reactor effluent stream prior to recycle. 

The number of streams feeding the plant, the number of contaminated streams, the mercury concentration and the type of mercury removal system considered aU have a potential impact on the cost of the removal system. For overall economic assessment, one should consider the in-plant impact and the cost of removal systems for regeneration/waste effluent systems as well as down-stream client impacts. One should also consider other contaminants which are present in the natural gas condensate i.e. mainly arsenic but also sometimes phosphorus, lead or sihcon. For these contaminants, there is no removal process which is industrially apphed on the steam-cracker effluents. 

The study by Anderson and Clark [10] of heavy metals removal from the effluent of a medium-sized multi-product dyestuffs company illustrates the progressive development of an effluent control system. Typical concentrations of metals in the raw effluent and the discharge limits set by the water authority are set out in Table 6.5. 

The removal of CO2 from an H2 gas stream can be accomplished with a glass tube packed with KOH pellets, as shown in Figure 4.5B. This works best if used after a recombination-type O2 removal system because the H2O present in the effluent increases the solubility of CO2 into the thin layer of water on the KOH pellets. 

A different scheme is offered by C. F. Braun and Co., which takes the effluent vapor from the acid gas removal system and, after drying and cooling, feeds it to the depropanizer [15]. The overhead from this column is compressed to around 540 psia, hydrogenated to remove the dienes, and chilled to separate a hydrogen stream from the condensed hydrocarbons. Liquid condensates contain methane, plus the C-2 and C-3 hydrocarbons present in the feed to the depropanizer. These liquids are fed to the demethanizer, which strips the methane overhead. The demethanizer bottoms serve as feed to the deethanizer. The overhead from that column goes to the C-2 splitter, while the bottoms is the feed to the 03 splitter. The bottoms liquid from the original depropanizer is sent to the debutanizer for separation of the C-4 hydrocarbons from the aromatic gasoline fraction. 

Systems for removal of iodine from gaseous effluents at fuel reprocessing plants have generally been classed into primary, secondary, and final cleanup systems. Primary iodine removal systems are de-... 

Numerous fuel reprocessing plants have been operated (or planned) that included iodine removal systems on the gaseous effluent streams (CEC, 1982a). Table 6.1 lists several reprocessing plants along with type of iodine removal system used at each and the overall stack decontamination factor. Overall stack DFs can vary considerably compared to the theoretical efficiency of the individual systems because of routing in the plant of streams that may contain iodine. 

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