Airlift pump

A lift pump, also airlift, air lift, gas lift or after its inventor Carl Emanuel Löscher (formerly ) also called extinguisher pump is a vertical in a liquid, usually water, plunging, pipe in which below the liquid level, a gas, usually air, by means of a compressor is pressed. It is used preferably to raise solid laden liquids.

Carl Emanuel Löscher called his invention in 1797 as the " aerostatic Kunstgezeug " - a name which even then could not prevail. The pictorial, the operating principle of better befitting name lift pump is believed to have been assigned by the vernacular a little bit later and probably. The earliest use of the name lift pump in the literature is known from 1846. Since then, this name did not last general naturalized because of its advertising effectiveness.

Function and types

If an open to the atmosphere U-tube partially filled with water, the same water level at rest in both legs (Fig. 1a). If a quantity of air taken in one of the legs above the water level and simultaneously injected at a lower place, here the water level rises until the air has escaped through their buoyancy from the water. In the other legs of the water level unchanged (Fig. 1b) remains. Permanent repetition of the process itself sets a difference in the water level that can be used to promote the water to a greater height.

Based on the water level resting position, created by the injection of air, a density difference between the two sides of the U-tube, which is often - is regarded as the driving torque of the lift pump - but wrongly. It is not true that the "lighter" made ​​by air liquid column in the one leg now " heavier " by the liquid column in the other leg is pushed upward. With such an approach can in particular not explain why - at no increased air use - relatively better efficiencies are achieved when pumping solid -water mixtures than in pure water pumping or lift pumps with small, slowly rising air bubbles work better than with large, fast ascending ( inhibition or slowing down of the air passage ).

If, however, the consideration of boundaries (correctly or the entire above oppressive atmosphere layer) relative to the top edge of the U-tube, it is not important for the density, whether the quantity of air just looked at is above or below the water level. Both sides always contain the same amount of water and air. With this approach, there is then that for the function of lift pump alone the floorboard time of air bubbles is crucial due to the mixture column.

Moreover, the principle of the mammoth pump delivery is also given where vapors ascend in liquids. Such pumps are called bladder pumps ( engl. vapor or vapor lift lift ). They are thermally driven by the liquid is heated in one of the legs to above the boiling point, so that vapor bubbles that rise in the liquid. The head of a bubble pump is very low in general, and it can only liquids or suspensions are used, which allow nucleate boiling (coffee maker, diffusion absorption refrigerator, airlift reactor ).

Figure ( 2) represents mammoth pumps, in which the required immersion depth must be created structurally. Such mammoth pumps were used in the sugar industry to raise beet -water mixtures and often required costly abzuteufende shafts ( known there as well).

Image ( 3) shows the construction in which the required insertion depth is provided from the outset. This mammoth pumps are still often in use, for example in the promotion of mud, sand, gravel from the bottom of a lake in the hold of a ship. Working also with air aquarium pumps belong to this design.

Figure (4 ) shows the design of a, well lots of lift pump ' with which the Abteufung a shaft can be avoided. As seen in the conveying direction, is taken first with a vacuum -operated, almost upside-down lift pump (which could also work alone). In the second part of a mammoth pump works with the immersion depth generated by the front -lift pump. About the large-scale testing beyond use cases are not known.

Features

Can be adjusted by selecting suitable lift pump pipe diameter and immersion ratios ( ratio of depth of immersion e to rise height s ) diverse conveying tasks. They promote the more, the larger the pipe diameter, thereby promoting the better, the greater the immersion ratio. The lifting height of the lift pump design as shown in ( 2) is seldom an economic point of more than 10 - 20 m.

According to Werner Maltry apply - based on the dissertation of Hans Behringer - for common types of lift pumps for water pumping on the parameters shown in two examples in the following nomogram:

The nomogram connects the tube length of the lift pump with flow rates for water and air (air at STP ) at the point of best efficiency for immersion ratios of e / s = 0.4 ... 0.8. For example, is the task of 300 m³ / h of water at 5 m with a lift pump in the immersion ratio = raise e / s 0.5, then - starting from the curve intersections for water and air - a tube length of about 370 mm and an air requirement required of about 1,060 m³ / h; The immersion depth is 5 m s (left nomogram ). Can other hand, for the same task, the immersion depth of the lift pump to 12 m can be increased, so that at 5 m head an immersion ratio of about e / s = 0.7, derives pipe diameter and air needs leave on for about 310 mm and about 400 m³ / h decrease (right nomogram ). In this way, the nomogram can be used for a überschlägliche sizing (larger) lift pump, and it is immaterial whether the air or the amount of water is assumed as the target size of the pipe diameter. The head h is e at lift pump always related to the depth of immersion

For smaller models (up to 100 mm tube length ) Abed provides the basis of a physico- mathematical model values ​​determined in a similar representation.

When pumping solid -water mixtures, a larger or smaller air rate is required depending on the mixture density. To reduce loss of pipe while the tube diameter or the radii of curvature should be selected at least twice or three times as large as the grain diameter.

Based on the output from the compressor capacity, reach lift pump as a function of immersion ratio efficiencies of 20 % ... 65%. Including the air compressor, the overall efficiency is even worse, and is usually below 20%. The design ( 4) cuts on principle and because of the water to be used ring compressor ( wily water shares ) are particularly badly.

Pump characteristics comparable to those of centrifugal pumps or piston pumps, there are not for lift pumps. Despite the simplest technique, the flow conditions are so complicated that the few reported in the literature figures differ greatly from one another. Therefore, all figures reported here with the utmost caution must be considered.

Use

Due to the absence of any moving parts lift pumps are well suited for the transport of solids, which require a special protection (sugar beet, potatoes, vegetables, live fish, activated sludge from sewage treatment plants, electronic components, etc.). Supposedly in lift pump for sugar beet production in a case of " the greyhound of the Director " and in another case, " a working boy," the passage have survived unscathed through a lift pump.

Next is this principle in the hobby use. In conjunction with a filter mat ( Hamburg mat filter) you can find very often use because the small animals that still come through the filter mat, not to be killed, for example, in the breeding tank or shrimp basin.

If it's not on the conservation of solids at, lift pump other pump types for reasons of wear can still be superior. That is, for example, in grit chambers of wastewater treatment is the case, why lift pumps are widely used there. Their application is suitable also for the extraction of minerals from the seabed ( manganese nodules ). Lift pump should have been used from 1897 to the oil production on the fields at Baku will be a great sensation at the World Exhibition 1892/93 in Chicago ( with the participation of Mendeleev), from 1901 on American oil fields, previously had such a machine.

A lift pump can also serve as a chemical reactor, because in her always held a turbulent mixing of liquid, gas and solid. In such reactors, the airlift circulation of ingredients ( in particular a solution or suspension), not with stirrers, but rather solely by the injection of air or the generation of steam is performed.

Even so-called Gasrührwerke or the targeted circulation of natural water bodies by air injection (seawater circulation ) are based on the principle of lift pump, although in these cases no funding is intended to a greater height. If the liquid is supersaturated with gases, a promotion function without external gas supply. This is for degassing of gas-rich natural lakes used ( Lake Nyos and Lake Kivu ).

Furthermore, the principle of the lift pump is used in the Ruhr steel -Heraeus - procedures as well as the sinking of geological and drilling wellbores. In the former, there is the so-called " vacuum circulation process ", the latter to the " Lufthebebohrverfahren ".

In essence, the use of airlift pumps is limited to cases in which

• It to the absolute energy consumption does not arrive ( small pipe diameters ),
• The protection to be conveyed solids in the foreground,
• Other types of pumps from wear or cost out of the question and / or
• Favorable conditions are present ( large immersion ratio).