Mammoth pump

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A mammoth pump , also known as compressed air lifter , airlift , gas lift or, after its inventor Carl Immanuel Löscher (earlier), also called extinguisher pump , is a pipe that is preferably vertically immersed in a liquid , usually water, into which a gas , usually air, is inserted below the liquid level Compressor is pressed. It is primarily used to lift solids-laden liquids.

In 1797, Löscher described his invention as aerostatic artifacts - a name that did not catch on even then. The pictorial and effective advertising name Mammut Pump was used a little later; the earliest use of this name in literature since 1846 is documented.

Function and designs

Mammoth pump : function and designs

If a U-tube that is open to the atmosphere is partially filled with water, the water level will be the same in both legs (in Figure 1a). If a quantity of air is removed from one of the legs above the water level and at the same time blown in at the lower point, the water level rises here until the air has escaped from the water again through its buoyancy . In the other leg, the water level remains unchanged (in Figure 1b). With constant repetition of the process, there is a difference in the water level, which can be used to convey the water to a greater height.

In relation to the water level at rest, the air injection creates a density difference between the two sides of the U-tube, which is at least a driving torque of the mammoth pumps. Because air is mixed in, the density in the leg decreases with the mixture and the level rises here compared to the level of the pure water in the other leg according to the ratio of air to water. That already explains the function of the mammoth pump. In addition, dynamic effects can influence the delivery head and the efficiency of mammoth pumps.

If the observation limits are related to the upper edge of the U-tube (or, more correctly, to the entire layer of the atmosphere above it), it is not important for the density whether the air quantum under consideration is just above or below the water level.

Incidentally, the principle of mammoth pump delivery is also given where vapors rise in liquids. Such pumps are called bubble pumps (vapor lift or vapor lift). They are thermally driven by heating the liquid in one of the legs above the boiling point, creating vapor bubbles that rise in the liquid. The delivery head of a bubble pump is generally very low, and only liquids or suspensions that enable nucleate boiling can be used ( coffee machine , diffusion absorption refrigerator , airlift reactor ).

Image (2) shows a mammoth pump, where the required immersion depth has to be structurally created. Such mammoth pumps were used in the sugar industry for lifting beet- water mixtures and often required expensive shafts (called wells there).

Figure (3) shows the design in which the required immersion depth is given from the start. Such mammoth pumps are often used to z. B. to promote mud, sand, gravel from the bottom of a lake into the hold of a ship. This also includes aquarium pumps that work with air.

Figure (4) shows the design of a " well-less mammoth pump" with which the sinking of a shaft can be avoided. Seen in the conveying direction, a mammoth pump that is virtually turned upside down is used first (which could also work alone). In the second part, a mammoth pump works with the immersion depth generated by the front vacuum mammoth pump. However, no applications beyond large-scale testing are known.

Performance characteristics and design

Mammoth pump: nomograms

Mammoth pumps can be adapted to a wide variety of pumping tasks by selecting suitable pipe diameters and immersion conditions (ratio of immersion depth  e to height of rise  s ). The larger the pipe diameter, the more they convey, and the greater the immersion ratio, the better. From an economic point of view, the delivery head of mammoth pumps of the type shown in Figure (2) is rarely more than 10-20 m.

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

The nomogram connects the pipe width of the mammoth pump with the volume flows for water and air (air in the standard state ) at the point of best efficiency for immersion ratios of e / s = 0.4 ... 0.8. For example, if the task is to lift 300 m³ / h of water by 5 m with a mammoth pump with an immersion ratio of e / s = 0.5, then - based on the intersection of the curves for water and air - a pipe width of about 370 mm and an air requirement of about 1,060 m³ / h required; the immersion depth e is 5 m (left nomogram). If, on the other hand, the immersion depth of the mammoth pump can be increased to 12 m for the same task, so that an immersion ratio of about e / s = 0.7 results at a delivery height of 5 m, the pipe width and air requirement can be about 310 mm and about 400 m³ / h decrease (right nomogram). In this way, the nomogram can be used for an approximate dimensioning of (larger) mammoth pumps, regardless of whether the target size is the pipe size, the amount of air or the amount of water. With mammoth pumps, the delivery head h is always related to the immersion depth e.

For smaller versions (up to 100 mm pipe width) Abed offers values ​​determined using a physical-mathematical model in a similar representation.

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

Based on the output from the compressor, mammoth pumps achieve efficiencies of 20% to 65%, depending on the immersion ratio. Including the air compressor, the overall efficiency is even worse and is usually below 20%. The design (4) performs particularly poorly due to the principle and because of the water ring compressor to be used (over-torn water).

Pump characteristics comparable to those of centrifugal pumps or piston pumps do not exist for mammoth pumps. Despite the simplest technology, the flow conditions are so complicated that the few figures reported in the literature differ greatly from one another. Therefore, all the figures given here must be viewed with the greatest of caution.

use

The reasons why mammoth pumps are used in spite of their low overall efficiency are that they do not put a mechanical load on the goods to be pumped, hardly clog them and introduce air into the aqueous fluid , whereby they are used, for example, for pumping wastewater containing microorganisms or activated sludge or for Circulation of aquarium water to water filters .

Due to the lack of any moving parts, mammoth pumps are well suited for pumping solids that require special care (sugar beets, potatoes, vegetables, live fish, activated sludge from wastewater treatment systems, electronic components, etc.).

This principle is also used in aquaristics. In connection with a filter mat ( Hamburg mat filter ), they are very often used, for example, in rearing tanks or shrimp tanks, as the small animals that still get through the filter mat are not killed.

The gentle effect on the pumped material is said to have been described in specialist articles from the beet processing industry; allegedly had in mammoth pumps for the sugar beet production in one case "the greyhound even survived the Director" and in another case "a working guy," the passage by a mammoth pump unscathed.

If it is not important to protect the solids, mammoth pumps can still be superior to other pump types due to wear and tear. This is the case, for example, in sand trap systems for wastewater treatment, which is why mammoth pumps are widespread there. They can also be used for the extraction of mineral resources from the seabed ( manganese nodules ). Mammoth pumps are said to have been used for oil production in the fields near Baku from 1897 (with the assistance of Mendeleev ), and then from 1901 on American oil fields; previously such a machine had caused a sensation at the world exhibition in Chicago in 1892/93 .

A mammoth pump can also serve as a chemical reactor, as there is always a turbulent mixing of liquid, gas and solid in it. In such airlift reactors , the ingredients (in particular solution or suspension ) are not circulated with stirrers , but exclusively by blowing in air or generating steam.

So-called gas agitators or the targeted circulation of natural water bodies by blowing in air (sea water circulation) are also based on the principle of the mammoth pump, even if in these cases no delivery to a greater height is intended. If the liquid is oversaturated with gases, pumping can also work without an external gas supply. This is used to degas natural lakes rich in gas ( Lake Nyos and Lake Kiwu ).

Furthermore, the principle of the mammoth pump is used in the Ruhrstahl-Heraeus process and in the drilling of geological boreholes and shaft boreholes. The former is the so-called vacuum circulation process , the latter the air-lift drilling process .

In essence, the use of mammoth pumps is limited to cases where

  • the absolute energy consumption is not important (small pipe diameters),
  • the focus is on protecting the solids to be conveyed,
  • other pump types are out of the question for reasons of wear and tear and / or
  • favorable conditions are present (high immersion ratio).

literature

  • H. Behringer: The liquid pumping according to the principle of the mammoth pump . Dissertation. Technical University of Karlsruhe, 1930.
  • W. Maltry: For dimensioning mammoth pumps. In: Deutsche Agrartechnik. 18, 5, 1968, pp. 233-235.
  • U. Gutteck: Design guidelines for mammoth pumps and washing channels . Institute for Research and Rationalization of the Sugar Industry, Halle (S.) 1984.
  • U. Gutteck: Well-less mammoth pump . R / D report, Institute for Research and Rationalization of the Sugar Industry, Halle (S.) 1986.
  • P.-V. Schmidt: Sugar beet - storage and processing . Publishing house Dr. Albert Bartens, Berlin 1990.
  • KA Abed: Operational Criteria of Performance of Air-lift Pumps (design criteria for mammoth pumps). In: The Institution of Engineers (India) Journal-MC. Vol. 84, April 2003.

Web links

Commons : Mammoth Pump  - Collection of Images

Individual evidence

  1. ↑ a b ИСТОРИЯ СОЗДАНИЯ, ИССЛЕДОВАНИЯ И ОБЛАСТЬ ПРИМЕНЕНИЯ ЭРЛИФТОВ Папаяни Ф. А., Козыряцкий Л. Н., Кононенко А. П., Пащенко В. С. Retrieved April 4, 2019 .
  2. ↑ Wayback Machine. October 4, 2006, accessed April 4, 2019 .