Duct Booster
 |
 6 Inch 530 CFM COMMERCIAL GRADE Inline Duct Fan Booster Vent Hydroponic Blower $79.89 Time Remaining: 18d 15h 27m Buy It Now for only: $79.89 |
 Tjernlund DB 2 Air Duct Flow Booster NEW $81.08 Time Remaining: 5d 20h 4m Buy It Now for only: $89.98 |
 Tjernlund Automatic 8 Duct Booster Fan with Cord EF $129.10 Time Remaining: 13d 2h 2m Buy It Now for only: $129.10 |
 14 Aero Flo 1350 HIGH CFMs inline Duct Air Booster Fan $78.90 Time Remaining: 13d 23h 24m Buy It Now for only: $78.90 |
 8 Inch Inline Fan Duct Booster Blower Hydroponic Air Vent Exhaust Heating Radon $109.89 Time Remaining: 18d 14h 45m Buy It Now for only: $109.89 |
 NEW 4 Inline DUCT FAN BOOSTER same as SUNCOURT DB204 $31.76 Time Remaining: 8d 12h 22m Buy It Now for only: $31.76 |
 Aero Flo 240 HIGH CFMs 6 inline Duct Air Booster Fan 100 NEW+FAST SHIPPING $28.95 Time Remaining: 25d 21h 16m Buy It Now for only: $28.95 |
 Tjernlund DB2 Duct Booster for Rectangular Ducts $95.88 Time Remaining: 14d 18h 43m Buy It Now for only: $95.88 |
 TJERNLUND DUCT BOOSTER FAN MODEL EF 12 $80.00 Time Remaining: 29d 19h 50m Buy It Now for only: $80.00 |
 Furnace Duct Booster Fan Air Circulation Heat Transfer $59.00 Time Remaining: 2d 23h 13m Buy It Now for only: $59.00 |
 Duct Booster 6 115 vac 60hz Increases Low Air Flow Areas $27.95 Time Remaining: 4d 9h 43m Buy It Now for only: $27.95 |
 DUCT BOOSTER Increase Air Flow Easy Installation 8 $36.55 Time Remaining: 14d 22h 32m Buy It Now for only: $36.55 |
 TJERNLUND EF 6 DUCT BOOSTER DUCT AIR FLOW BOOSTER $42.25 Time Remaining: 18d 15h 39m Buy It Now for only: $42.25 |
 Air booster fan booster fan for air ducts 6 or larger $69.99 Time Remaining: 20d 17h 30m Buy It Now for only: $69.99 |
 Duct Booster 8 115 vac 60hz Increases Low Air Flow Areas $32.95 Time Remaining: 4d 9h 44m Buy It Now for only: $32.95 |
 DUCT BOOSTER Heat Ducting Booster Fan 150 CFM 110V $123.00 Time Remaining: 6d 11h 1m Buy It Now for only: $123.00 |
 Tjernlund Duct Booster Fan 12in 875 CFM NEW $139.99 Time Remaining: 24d 22h 19m Buy It Now for only: $139.99 |
 8 Inline DUCT FAN BOOSTER exhaust vent boost SUNCOURT WILL FEDEX SHIP TO CANADA $34.95 Time Remaining: 26d 15h 5m Buy It Now for only: $34.95 |
 Waterline Products AIR BOOSTER 1950101 5 round ducting heating cooling furnace $46.19 Time Remaining: 16d 12h 34m Buy It Now for only: $46.19 |
 10 Aero Flo 650 HIGH CFMs inline Duct Air Booster Fan $49.41 Time Remaining: 18d 10h 49m Buy It Now for only: $49.41 |
 Tjernlund DB 2 Air Duct Flow Booster NEW $81.08 Time Remaining: 5d 21h 40m Buy It Now for only: $89.98 |
 Tjernlund Duct Booster Fan 14in 1200 CFM EF 14 $169.99 Time Remaining: 29d 6h 45m Buy It Now for only: $169.99 |
 Tjernlund Duct Booster Fan 10in 475 CFM NEW $119.99 Time Remaining: 21d 8h 42m Buy It Now for only: $119.99 |
 12 Aero Flo 975 HIGH CFMs inline Duct Air Booster Fan $66.00 Time Remaining: 10d 11h 28m Buy It Now for only: $66.00 |
 6 240 HIGH CFMS Aero Flo Furnace duct Booster Fan $30.90 Time Remaining: 23d 4h 52m Buy It Now for only: $30.90 |
 14 Aero Flo 1350 HIGH CFMs inline Duct Air Booster Fan $76.00 Time Remaining: 10d 11h 27m Buy It Now for only: $76.00 |
 8 Aero Flo 420 HIGH CFMs inline Duct Air Booster Fan $31.00 Time Remaining: 10d 11h 32m Buy It Now for only: $31.00 |
 8 Aero Flo 420 HIGH CFMS Attic Booster Fan Duct Fan $33.90 Time Remaining: 23d 4h 58m Buy It Now for only: $33.90 |
 8 Aero Flo 755 HIGH CFMs inline Duct Air Booster Fan $120.00 Time Remaining: 19h Buy It Now for only: $120.00 |
 10x25 APS Poly Flex Duct duct booster line extension $48.00 Time Remaining: 22d 14h 57m Buy It Now for only: $48.00 |
 6 240 HIGH CFMS Aero Flo Furnace duct Booster Fan $29.00 Time Remaining: 10d 11h 33m Buy It Now for only: $29.00 |
 14 Aero Flo 1350 HIGH CFMs inline Duct Air Booster Fan $78.90 Time Remaining: 21d 1h 49m Buy It Now for only: $78.90 |
 8 inch Inline Duct Booster $39.99 Time Remaining: 9d 22h 32m Buy It Now for only: $39.99 |
 8 Aero Flo 420 HIGH CFMs inline Duct Air Booster Fan $33.90 Time Remaining: 9d 11h 22m Buy It Now for only: $33.90 |
 6 Aero Flo 240 HIGH CFMs inline Duct Air Booster Fan $30.90 Time Remaining: 2d 22h 28m Buy It Now for only: $30.90 |
 10 Aero Flo 650 HIGH CFMs inline Duct Air Booster Fan $54.90 Time Remaining: 9d 11h 21m Buy It Now for only: $54.90 |
 8 420 HIGH CFMS Aero Flo Furnace duct Booster Fan $33.90 Time Remaining: 19d 18h 57m Buy It Now for only: $33.90 |
 10 Aero Flo 650 HIGH CFMs inline Duct Air Booster Fan $52.00 Time Remaining: 10d 11h 30m Buy It Now for only: $52.00 |
 4 Aero Flo 185 HIGH CFMs inline Duct Air Booster Fan $64.00 Time Remaining: 19h 1m Buy It Now for only: $64.00 |
| Account limit of 2197 requests per hour exceeded. |
How to Design and Operate a Px® System Part 1
The new pressure exchanger (PX) device transfers the energy from the concentrate stream directly to the feed stream. This direct, positive displacement approach results in a net transfer efficiency of over 95%. Although application of the PX technology is simple in both theory and practice, in order to get the most benefit from this technology it is important to reconsider the SWRO design and operation approach. Pertinent design considerations include pre-filtration, conversion rate optimization; pump selection, and operating pressures. Some important operating procedures and characteristics are start up, high pressure regulation, conversion rate optimization, flow balancing, and shutdown. Furthermore, it will be shown that these considerations affect the design and operation of SWRO systems counter-intuitively and may possibly reverse given standards that have been developed over the past 20 years of SWRO design.
There has been a recent proliferation of commercially available energy recovery devices based on the positive displacement direct pressure exchange approach. This increased interest is driven by the fact that the technology can reduce the energy consumption of an SWRO system by as much as 60%. Since energy costs are rising and can consume as much as 75% of the total operating costs of an SWRO plant, it is important that the technology be encouraged and disseminated throughout the industry. Although the authors of this paper are directly associated with Energy Recovery, Inc., a leading company in pressure exchanger technology, the principles and theories presented in this paper will be applicable to all devices based on the positive displacement, direct pressure exchange approach.
1.0 INTRODUCTION
The PX is a new pressure exchanger device that transfers the energy from the concentrate/reject stream directly to the feed stream in a cylindrical rotor with longitudinal ducts. The rotor spins inside a sleeve between two end covers that divide the rotor into high and low pressure halves. When designing a seawater RO system using the new pressure exchanger device it is only necessary to reconsider the high pressure portion of the system. This is because this is the only portion that differs from earlier RO designs. Pertinent design considerations include conversion rate optimization, pump selection, and operating pressures. Some important operating procedures and characteristics are start up, high pressure regulation, conversion rate optimization, flow balancing, and shutdown. Although application of the pressure exchanger is simple in both theory and practice it is vastly different from typical SWRO design and operation. These differences affect the design and operation of SWRO systems in surprising ways that can be used to improve other aspects of system performance beyond the scope of energy consumption alone.
2.0 PRINCIPLE OF OPERATION
The PX unit utilizes the principle of positive displacement to transfer the energy in the reject stream directly to the feed stream. It is interesting to note that the reject stream is continuously and directly connected to the feed stream. This direct connection allows a real net transfer efficiency of energy from the reject stream to the feed stream of over 95%. The PX device uses a cylindrical rotor with longitudinal ducts parallel to its rotational axis to transfer the pressure energy from the concentrate/reject stream to the feed stream.
The rotor spins inside a sleeve between two end covers with port openings for low and high pressure. The low-pressure side of the rotor fills with seawater while the high-pressure side discharges seawater. The rotation simply facilitates the valving mechanism, which is to transport the ducts from one side to the other.
By rotation the ducts are exposed to the low pressure feed water, which fills the duct and displaces the reject water. The rotor continues to rotate and is exposed to the high-pressure concentrate, which fills the duct from the opposite direction, and displaces the feed water at high pressure. This rotational action is similar to a Gatling machine gun firing high-pressure bullets and being refilled with new seawater cartridges from the muzzle. A liquid piston moves back and forth inside each duct creating a barrier that inhibits mixing between the concentrated reject and new seawater streams. At 1500 rpm one revolution is completed every 1/25 second. Due to this short cycle time, membrane feed water concentrations typically increase only 1%-2%. See Figure 4-1 below.
Applying PX pressure exchanger technology to SWRO is different from conventional energy recovery device system design, but in practice is quite simple. The reject brine from the SWRO membranes is passed into the PX unit, where its pressure energy is transferred directly to a portion of the incoming raw seawater at up to 97% efficiency. This seawater stream, nearly equal in volume and pressure to the reject stream, then passes through a high-pressure booster pump, not the main high-pressure pump. This booster pump is making up the pressure losses across the RO membrane (approx. 2 bar), PX unit(s) (approx. 1 bar) and piping losses (approx. 0.5 bar). The total head provided by the boost pump is typically around 3.5 bar. See figure 4-2 and table 4-1 below.
It is important to notice that the PX and associated boost pump are handling nearly 100% of the reject flow. The size of the main high-pressure pump has been reduced to a make up pump for the permeate flow that is exiting the RO system. Product water flow and reject flow are being provided by two independent pumping systems and therefore are independent of one another.
Since the PX unit is providing nearly 100% of the reject flow at over 95% efficiency there is very little energy penalty associated with increasing this flow and thereby lower the conversion rate of the RO system. At lower conversion rate the pressure required to produce the same amount of product water is lower. Since the main high-pressure pump flow equals the product water flow an energy savings is actually achieved at lower conversion rates.
3.0 CONVERSION OPTIMIZATION
There are many factors that effect RO conversion optimization but none has been more influential than energy consumption. This is because energy costs can be as much as 75% of the entire operating cost of an SWRO plant. In the past the sewater to fresh water conversion rate has had a major and direct impact on the energy consumption of an RO plant. This is because of the inherent shortcomings of the energy recovery and pumping devices that have been used such as the Pelton wheels, turbines, and pumps. These technologies have real/overall net transfer efficiencies of 40-70 percent and are designed to pump the entire feed flow of an RO plant. Therefore at lower conversion rates these inefficient devices are pumping more water. The only way to make these devices pump less water and thereby consume less energy is to increase the conversion rate of the RO system. This is all very logical, and with rising energy costs it is natural that SWRO systems are now being designed at the membrane challenging conversion rates of 50-60%.
System designs with the PX device are different. This is because the PX, a 95% efficient device, is pumping the reject water independently of the product water being produced. The overall energy consumption of an SWRO plant using the PX device has a low point at conversion rates typically between 30-40%. Outside these conversion points the plant will start to consume slightly higher amounts of power. See figure 3 below.
It is important to remember that with the PX device the main high pressure pump flow approximately equals the product water flow. At lower conversion rates it requires lower pressure to produce the same amount of product water. Therefore, the main high-pressure pump will consume less power pumping against less pressure at the lower conversion rates. This phenomenon yields the net energy decrease shown in Figure 3.
Another important point to consider is water quality. In the past, system design had to balance high conversion rate with good water quality. In high salinity applications this has been a difficult challenge. Figure 4 below shows how a lower conversion rate yields better water quality.
Logically combining the kWh/m3 vs Conversion Rate curve of Figure 3 with the diminishing water quality curve as the conversion rate increases in figure 4 shows us that there are good reasons now to consider SWRO designs with lower conversion rates. There are also additional benefits associated with lower conversion rate designs such as ease of operation, fewer cleaning cycles, longer membrane life and a better balance of flux (GFD) from the lead element to the end element in an RO pressure vessel. Figure 5 below shows how GFD is balanced as the system conversion rate lowers(5).
Of course decreasing the system conversion rate does have its disadvantages mainly in increasing the size of the pretreatment system. This effect is less significant in smaller systems under 1000 m3/day because of the less expensive piping materials, pressure media filtration systems and other components typically employed in these systems. However on larger plants using open seawater intakes with large-scale gravity feed media filtration systems, and when the chemical additions associated with coagulation are significant operating costs, conversion rates between 45-50% may be more practical.
About the Author
Wayne M of the American Water Works Assoc writes articles relating to Energy Recovery Inc., a Clean Technology Company that provides affordable Seawater Desalination with the PX Pressure Exchanger which reduces energy costs up to 98%.