I have two questions:
1) As you can see from the diagram I have attached, there is a line from the first fixed bed being connected to the second fixed bed. There is also a connection from the second fixed bed with the first fixed bed. What is that purpose for? Is it for dilution? For mixing?
2) From the decanter, the organic phase has to be recovered. Can I assumed that it is actually pure and does not need to be treated?
Dear Md.Badriadib,
The Carbon filters can be installed either series or parallel or both. In your figure two numbers carbon filters are in parallel with regeneration stream with steam along with air scoring with blower. When the carbon filters exhausted the backwash carry with steam.
Advantages of Parallel the pressure reduced in parallel stream this is the advantageous.
Carbon contactors can be configured as either
1. Down flow fixed beds
2. Up flow fixed or expanded beds, or
3. Pulsed beds; with single or multiple adsorbers operated in series or in parallel.
In down flow fixed beds in series, each unit is connected in series with the first adsorber receiving the highest contaminant loading and the last unit receiving the lightest contaminant load. Carbon is removed for reactivation from the first unit, with the next adsorber becoming the lead unit. For down flow fixed beds in parallel, each unit receives the same flow and contaminant load. To maximize carbon usage, multiple contactors are frequently operated in parallel-staggered mode in which each contactor is at a different stage of carbon exhaustion. Since effluent from each contactor is blended, individual contactors can be operated beyond breakthrough such that the blended flow still meets the treatment goal. Upflow expanded beds permit removal of suspended solids by periodic bed expansion and allow using smaller carbon particles without significantly increasing head loss. In pulsed bed adsorbers, removal of spent carbon occurs from the bottom of the bed while fresh carbon is added at the top without system shutdown. A pulsed bed cannot be completely exhausted, which prevents contaminant breakthrough in the effluent.
Adsorption itself is a phenomenon where gas molecules passing through a bed of solid particles are selectively held there by attractive forces which are weaker and less specific than those of chemical bonds .
Most gases (“adsorbates”) can be removed (“desorbed”) from the adsorbent by heating to a sufficiently high temperature, usually via steam with air scoring by blower.
Once the carbon reaches a certain VOC content, the unit is shut down and either the carbon or the cannister is replaced. The carbon or cannister is then returned to a reclaimation facility or regenerated at the central facility. Each cannister unit consists of a vessel, activated carbon, inlet connection and distributer leading to the carbon bed, and an outlet connection for the purified gas stream. The type of carbon used depends on the nature of the VOC to be treated .Non-regenrable vessles can be placed in a series, this protects agianst breakthrough because in the event that the first cannister or vessel becomes saturated with VOC, the second then becomes the primary carbon adsorber. One option would be to periodically remove the most saturated cannister or carbon bed and add a fresh cannister or carbon bed to the clean end. Periodic sampling for breakthrough between the carbon beds would assure that replacement occured frequently enough to avoid breakthrough to the atmosphere. This approach also improves cost effectiveness of carbon replacement because the carbon is at or near its saturation point when it is replaced.
Regards,
Prem Baboo
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