Wizbi
10-10-2015, 06:42 AM
In another Thread, BowHunter described a RO design that does not use a booster pump and does have concentrate recirculating directly into the suction line of the high pressure pump.
I have been trying to justify eliminating the use of a booster or feed pump due to issues to matching flow rates to the needs of a Procon pump and to desiring to do everything more cost consciously. An elevated tank is ideal for me in leue of forking over more $ on a pump and worrying about starving a procon pump.
Bowhunter identified benefit to teeing the concentrate flow in the procon pump suction line as to reduce pre-filters fouling.
Steve Childs of Princeton has convinced me via his Utube videos that recycling RO concentrate is a good way to multi-pass an RO system to get brix up on the sap before going to the evaporator.
Most RO DIY designs include a prefilter and a high pressure Procon pump. Prefilter differential pressure must be overcome to move fluid into the HP pump. This pressure differential is ~3psi for clean filters and as high as 15psi for filters needing changeout. Pressure differential can be mitigated by elevating feed tank.
Considering both perspectives, I decided to consider combining recycling and recirculation and tuning the ratios of flow into the suction line. I have attached a diagram that combines both recycling and recirculation. This would introduce an additional needle valve. Two concentrate needle valves would be set in a combined way similar to most RO designs having a single concentrate needle valve. One for recycling flow and one for recirculation flow. I have also attached a spreadsheet image that shows this analysis. Expectation is that the procon pump can only pull part of its input requirement through the prefilter, considering little to no head pressure on the feed tank. Results indicate that a 5:1 recycling to recirculation ratio will universally satisfy procon pump suction requirements provided feed tank/prefilter are elevated above Procon pump for all levels of prefilter fouling. Of course, elevating the head tank more can increase how much feed sap can reasonably flow into the suction line relative to the volume flowing via the direct concentrate return line (recirculation).
Procon pumps are spec'd to 6 ft max lift in a flooded suction scenario. I take the liberty to translate "max lift" to mean "max pull". What I find is that depending on the level of prefilter fouling, a ratio of recircultaion and recycling can be attained to best route as much concentrate through the feed tank/prefilter as possible and also keep the procon pump from cavitating. Recirculataion can also provide some backpressure on the prefilter cartridge to keep it from fouling as fast.
Additionally, the recyling line can be used to transfer sap that has desired elevated brix onward to the evaporator just by repositioning the return hose.
I am wondering if anyone else has considered this. Any thoughts ?
1200212003
I have been trying to justify eliminating the use of a booster or feed pump due to issues to matching flow rates to the needs of a Procon pump and to desiring to do everything more cost consciously. An elevated tank is ideal for me in leue of forking over more $ on a pump and worrying about starving a procon pump.
Bowhunter identified benefit to teeing the concentrate flow in the procon pump suction line as to reduce pre-filters fouling.
Steve Childs of Princeton has convinced me via his Utube videos that recycling RO concentrate is a good way to multi-pass an RO system to get brix up on the sap before going to the evaporator.
Most RO DIY designs include a prefilter and a high pressure Procon pump. Prefilter differential pressure must be overcome to move fluid into the HP pump. This pressure differential is ~3psi for clean filters and as high as 15psi for filters needing changeout. Pressure differential can be mitigated by elevating feed tank.
Considering both perspectives, I decided to consider combining recycling and recirculation and tuning the ratios of flow into the suction line. I have attached a diagram that combines both recycling and recirculation. This would introduce an additional needle valve. Two concentrate needle valves would be set in a combined way similar to most RO designs having a single concentrate needle valve. One for recycling flow and one for recirculation flow. I have also attached a spreadsheet image that shows this analysis. Expectation is that the procon pump can only pull part of its input requirement through the prefilter, considering little to no head pressure on the feed tank. Results indicate that a 5:1 recycling to recirculation ratio will universally satisfy procon pump suction requirements provided feed tank/prefilter are elevated above Procon pump for all levels of prefilter fouling. Of course, elevating the head tank more can increase how much feed sap can reasonably flow into the suction line relative to the volume flowing via the direct concentrate return line (recirculation).
Procon pumps are spec'd to 6 ft max lift in a flooded suction scenario. I take the liberty to translate "max lift" to mean "max pull". What I find is that depending on the level of prefilter fouling, a ratio of recircultaion and recycling can be attained to best route as much concentrate through the feed tank/prefilter as possible and also keep the procon pump from cavitating. Recirculataion can also provide some backpressure on the prefilter cartridge to keep it from fouling as fast.
Additionally, the recyling line can be used to transfer sap that has desired elevated brix onward to the evaporator just by repositioning the return hose.
I am wondering if anyone else has considered this. Any thoughts ?
1200212003