Thick matter pump
Thick matter pumps are pumps for conveying mixtures of liquid and solid components. They work according to the hydrostatic principle, displace the medium to be pumped and thus generate a flow rate.
Thick substances and their promotion
Thick substances are mixtures of liquid and solid components. They differ physically and chemically according to their specific weight, dry matter content, (maximum) grain size and their behavior, for example thixotropic, abrasive or adhesive.
Typical examples of thick matter are sludge with up to 50 percent by weight of solids, as well as suspensions , in which finely divided solids with a grain size of up to two millimeters are suspended in a liquid ( slurry ).
In industrial plants, substances with a high proportion of solids, such as mechanically dewatered sewage sludge , filter cakes , hard coal , waste and process sludge , have to be moved over greater distances to landfills or incinerators. In principle, (mechanical) conveyor technology or ( hydraulic ) thick matter pumps are suitable for this purpose.
Mechanical conveyors include belts, augers, scrapers, and troughs. They are suitable for almost all types of thick matter.
Hydraulic thick matter pumps can be used to convey thick matter in closed pipelines. However, thick matter can only be pumped depending on its plasticity. Requirements for pumpability are:
- Mixing ratio: The mixture of the solid and liquid components of a thick matter must be built up in such a way that a plastically deformable mass results.
- Saturation: A pumpable thick matter must be saturated, i.e. This means that the pore volume of the solids must be filled with a sufficient proportion of their own grain so that grain to grain can be supported by a viscous plastic liquid and gaps are filled.
- Gas content: With discontinuous pumping in the pipe system, so-called pipe bumps can occur due to pressure fluctuations. In the case of thick matter without natural gas components, this can be prevented by feeding in around two percent air.
Types of thick matter pumps
Depending on the displacement principle, a distinction is made between rotating pumps (with rotor) and oscillating pumps (with piston). The first category includes a. Eccentric screw pumps, centrifugal pumps and screw spindles. The second category includes plunger, diaphragm and piston pumps.
The most extensively applicable thick matter pump is the hydraulically driven piston machine. It is technically designed as a one- or two-cylinder machine, the medium to be conveyed is fed and displaced or sucked in and displaced in push-pull.
Types of piston machines for conveying thick matter
Transfer tube pump
Seat valve pump
Ball valve pump
Single cylinder piston pump
Type transfer tube pump (2-cylinder)
Design features
The essential element of the transfer tube pump is the so-called S-tube installed on the material feed hopper. It connects the respective conveying cylinder of the thick matter pump with the conveying line via a so-called glasses plate. When the end of the piston stroke is reached or near the end of the piston stroke , the S-tube connected to the delivery line is swiveled, a hydraulic system synchronizes the position of the S-tube with the movements of the two delivery pistons.
The required quick and low-wear swiveling of the S-tube is done with the help of two plunger cylinders. A corresponding wear ring ensures the tightness between the lens plate and the S-tube during the pumping phase.
The cross-section of the S-tube is circular with a decreasing diameter in the conveying direction to reduce the risk of clogging. The sealing surfaces of the goggle plate and the wear ring are parallel to the pivoting movement of the S-tube. This prevents them from being damaged when foreign bodies are cut through or jammed.
Components to prevent material backflow are not required.
Operational properties
Transfer tube pumps are suitable for concrete and mortar, for sludge with a dry matter content of up to 50 percent by weight and a different grain size distribution and for the suspension of fly ash , coal or minerals .
With a diameter of the feed cylinder of 200 mm, thick materials with an average grain size of up to 80 mm can be pumped. The maximum diameter of individual foreign bodies can be up to 60% (in this case = 120 mm).
Design seat valve pump (2-cylinder)
Design features
The housing of a seat valve pump contains four hydraulically controlled seat valves, two suction and two pressure valves, each with a hydraulic cylinder. The suction and pressure valves of the pump head are synchronized with the hydraulics of the delivery pistons, so the delivery cylinder content is always the same as the delivery volume. When the "sucking" piston reaches its end position, the relevant suction or pressure valve is hydraulically closed or opened at the same time. If there is overpressure in the delivery line , the suction valve closes first. This prevents the material being conveyed from the pressure line from getting back into the funnel. Check valves are not required.
Operational properties
Seat valve pumps are particularly well suited for the uniform pumping of media with a dry matter content of up to 50% and for high-pressure pumping of pasty industrial thick matter such as sludge. Because of the existing valves, they are suitable for grain sizes up to a maximum of 8 mm.
The choice of valve shape depends on the thick matter to be conveyed. Media containing grains with a dry matter content of up to 50% should preferably be designed with a metallic, sharp-edged valve seal. The large-area elastomer valve seal is ideal for low-viscosity, more aqueous, fine sludges.
In a hydraulic control variant, the respective valve is passively opened by the thrust of the thick matter. The pressure valve then has a reliable non-return function in order to prevent backflow from the pressure line. At the same time, the thick matter is pre-compressed almost to line pressure before the pressure valve opens silently. Line bumps as a result of the pressure pulsations can thus be avoided.
Ball valve pump design (2-cylinder)
Design features
During the suction stroke of the delivery piston, the thick matter is sucked in via the open suction ball valve. The ball valve on the pressure side is drawn into the valve seat by the negative pressure created by the suction effect (self-regulating valves). At the same time, the second delivery piston performs the pressure stroke and displaces the medium into the delivery line via the pressure ball valve. The suction valve is pressed into its seat due to the delivery pressure and thus closes the connection to the suction connection of the pump.
Operational properties
The two-cylinder thick matter pump with ball valves is suitable for the lower to medium pressure range for pumping thin to pasty thick matter, as long as it can be sucked in through the valve openings, e.g. B. for mortar , mineral and sewage sludge . The ball valve pump is largely insensitive to aggressive and abrasive media, as the ball valves do not have to be closed and opened from the outside.
Type of piston pump (1-cylinder)
Design features
The pumped medium is "stuffed" from a material feed hopper into the feed cylinder and pressed into the feed line when the feed piston moves forward. Depending on the level of the delivery pressure in the pipeline and the flow properties of the thick matter, a flat slide valve or a medium barrier is attached to the pressure flange of the pump to prevent the material column from flowing back during the return stroke. The delivery piston is selected according to the material to be pumped: flowable media make Perbunan sealing elements necessary, bulky materials are crushed during pumping by means of hardened cutting edges.
Operational properties
The single-cylinder piston pump is also suitable for bulk goods with a coarse composition, for example wood chips, biomass or paper chips. If such (unsaturated) material has to be conveyed over greater distances, there is the possibility of hybrid conveyance. Compressed air is also injected into the delivery line here. The compressed air pushes the material plug into the pipeline. When the compressed air expands, the conveyed material is loosened and divided. With increasing distance from the injection site, the initial plug delivery changes into flight delivery. The amount of air required and the pipe diameter depend on the type and quantity of the conveyed material.
Assemblies of thick matter pumps
The essential components of a thick matter pump include:
- the feed opening / material feed
- the pressure cylinder (s) and the hydraulic unit
- Components for sealing the system
- electrotechnical and control systems
and depending on the design
- Pipe switch
- Valves
as well as in the periphery u. a.
- Silos (with / without discharge system)
- Screw conveyors, conveyor lines
- Compressed air injection
- Lubricant dosage
- Damping devices
Selection of slurry pumps
The special conveying medium "thick matter" and the large number of process engineering areas of application of thick matter pumps require different construction principles. The following table allows you to choose between four types depending on the material being conveyed:
| design type | Conveyed material (thick matter) | |||
|---|---|---|---|---|
| aqueous | stiff | loose | with foreign objects | |
| Transfer tube pump | + | + + | - | + |
| Seat valve pump | + + | + | - | - |
| Ball valve pump | + | O | - | - |
| Single cylinder piston pump | - | + + | + + | + + |
| + + very suitable, + well suitable, o partially suitable, - not suitable | ||||
Application examples
The hydraulic conveyance of solids with high dry matter contents is a versatile task in process engineering. In the construction industry, oil-hydraulically driven two-cylinder piston pumps with S-pipes have been used for pumping concrete for many years. This technology can be transferred to other areas of application in various industrial sectors.
NaWaRo
Renewable raw materials in the form of silage or as liquid manure and solid manure fractions are conveyed to treatment systems (e.g. fermenters or hydrolysis stages).
Sewage technology
The pipeline-based conveyance of mechanically dewatered sewage sludge is more environmentally friendly than other conveying systems (because it has little odor) and has been tried and tested for years.
Power plants
The pressurized fluidized bed combustion is a process for the efficiency-optimized and environmentally friendly operation of the boiler. Two-cylinder thick matter pumps are used to inject the coal-lime mixture directly into the combustion chamber.
Waste management
Common thick matter includes biological waste (biomass) and residual waste. These are transported to and from the mechanical-biological treatment plants ( MBT ) with thick matter pumps .
Even Hazardous waste such as paint sludge, hospital waste, laboratory chemicals and filter dust are physically, chemically and biologically treated, to reduce the volumes produced. For material transport, thick matter pumps with the advantage of pipeline conveyance are often used.
Mining
Overburden or pit water in mining or trenchless tunnel construction can also be pumped hydraulically.
Technological conditions
Funding routes
There are various aspects to consider when planning and implementing conveyor systems. These include the space required, accessibility for cleaning or service as well as necessary material transfers when combining horizontal and vertical conveying paths.
Environmental protection (noise and odor nuisance)
Due to the type of material being conveyed and the type of conveyance, noise and, in particular, odor nuisance are to be expected during the transport of thick matter. The right choice of conveyor technology (see above) can reduce environmental pollution.
Energy expenditure
When moving thick matter, three main forces have to be overcome:
- The delivery distance (see records for concrete pumps )
- Friction between the medium and the pipeline, especially in tapers or in pipe bends
- Internal frictional force due to deformation of the thick matter
Calculation example:
- Promotion of a suspension
- Delivery line with a diameter of 200 mm (DN200)
- Thick matter with mineral or carbon solids content as a mixture of coarse and fine grains
- Max. Grain size 50 mm
- Solids content up to 80 percent by weight
Energy consumption (depending on the system situation and permissible system pressures) = between 0.1 and 0.5 kWh per ton of conveyed goods and kilometer.
literature
- Wolfgang Zey: Thick matter pumps: structure and application . Verlag Moderne Industrie, Landsberg / Lech 1995 (The Library of Technology; Vol. 113) ISBN 3-478-93127-4 .