Two-pump system

The pumping rate of the lower pump is adjusted to produce sufficient water to cause a cone of depression extending outward to intercept and retrieve the LNAPL. While the water pump operates continually, the upper product pump cycles on and off as necessary to recover the product as it accumulates. 

Automatic interface detection probes attached near the intakes of both pumps provide an operating logic. The upper probe is adjusted to detect both air-product 

FIGURE 7.15 Schematic of an open-chambered skimmer pump. 

There are numerous advantages to a two-pump system. LNAPL is separated in the well, reducing the need for aboveground separators. Occasionally, the LNAPL can be recycled without further treatment. Because the mixing of product and water in the well is minimized, soluble components are not added to the pumped water. The most important advantage is that the system is fully automatic and can be operated continuously with minimal adjustment after start-up. 

Although this system is the preferred choice for many situations, it is commonly overused, and several disadvantages must be considered. Because all of the operating 

---

Two-pump systems Submersible turbine Moderate to high Unlimited Yes Yes ... 

The recovery most often used at sites with significant quantities of recoverable LNAPL is the two-pump system. A submersible water pump installed below the lowest possible probable interface level is used to create a drawdown cone of depression, while a second pump is suspended with its intake port located at the oil-water interface. A typical two-pump system installation is shown in Figure 7.15. 

Combined one- and two-pump system with reinjection (and vacuum enhancement). 

LNAPL recovery operations in the southwestern portion of the refinery have been conducted using a two-pump recovery system. This system currently includes up to four two-pump hydrocarbon recovery wells. Each two-pump system uses a 16-in.-diameter recovery well that is designed to accommodate two independently operated pumps placed at different levels within the well. 

The B components as described above all contain a certain amount of aqueous phase to safeguard the B pump seals in two-pump systems. If the pumping system uses one pump and partitioning valves, the B component as well as additional ones can be pure solvents. Indeed, with very hydrophobic peptides that will not elute with 60% MeCN, the concentration of the B component in MeCN must be increased to 80 or even 100%. 

Preparative separations in the grams per injection level are different. Separations are run isocratic in 1- to 3-in columns with large pore, fully porous packings (35-60jUm). An analytical, two-pump system can just barely reach the 20-mL/min flow rates needed to run a 1-in column. Special preparative HPLC systems deliver flow rates of 50-500 mL/min to handle the larger bore columns. A stream splitter is used to send part of the flow through a refractive index detector with a flow cell designed for concentrated solutions. 

Figure 4. Two pump system (a) clamp pump, Kw use (b) injection extruder...

A through-flow system with a continuous feed from two pump systems (illustrated in Figure 4.3.2) was used in order to minimize the rate of depletion of PAHs due to adsorption to the walls of the system, and to uptake by passive samplers deployed in the tank. The first pump provided a circulation of the Maas river water at a constant 10 Lh-1 flow rate, and the second one added a solution of 16 PAHs (prepared by the dilution of a stock working solution containing equal concentrations of the test 16 PAHs) in acetonitrile at a rate of 0.1 mF min-1. 

Figure 3.3 A schematic of the core of a high-pressure mixing (two-pump) system. The pumps are called binary, ternary or quaternary depending upon the number of solvents that can be mixed together (here binary). The mixing chamber, which controls the mobile phase composition, is at the output of the two high-pressure pumps on the downstream side of the pumps.

The heart is actually two pumping systems operated in series. The left heart pumps blood throughout the systemic blood vessels. The right heart pumps blood throughout the pulmonary system. Blood pressures in the systemic vessels are higher than blood pressures in the pulmonary system. 

A two-pump system for highly precise and accurate gradient formation for separation of complex samples. 

When pumps are connected in parallel, more than three of them would be required in such ULOF because there may be some reverse flow through the pump at fault. In a serially arranged two-pump system of the 4S-LMR, the core flow rate can be sustained at more than 50% of the rated flow, because there is no reverse flow and the functioning pump could be able to sustain a higher flow due to its flow-head curve. The analytical results obtained for the 4S-LMR indicate that this more severe ULOF pushes the temperatures up by about 10°C only, which is acceptable. They also point to certain margins in core pressure drop and... 

Comment on the following statement For a two-pump system, it is always best to run the two pumps in series rather than in parallel because greater scale-up will be possible. 

---