AU2016204480B2

AU2016204480B2 - Apparatus and method for dewatering a material containing water

Info

Publication number: AU2016204480B2
Application number: AU2016204480A
Authority: AU
Inventors: Steffen AUMÜLLER
Original assignee: Siempelkamp Maschinen und Anlagenbau GmbH and Co KG
Current assignee: Siempelkamp Maschinen und Anlagenbau GmbH and Co KG
Priority date: 2015-08-01
Filing date: 2016-06-29
Publication date: 2021-03-04
Anticipated expiration: 2036-06-29
Also published as: EP3127688B1; DE102015010056B4; PL3127688T3; CN106393777B; AU2016204480A1; CN106393777A; EP3127688A1; DE102015010056A1

Abstract

: The invention relates to an apparatus for dewatering a material (5) that contains water, by means of pressure and heat; with a) a device for metered delivery (2) of the material (5) onto a transport 5 device (3), b) a transfer section (C), in which the material (5) can be transferred, by means of the transport device (3), into a twin-belt press (4), and c) a twin-belt press (4) with - a lower press part (7) and an upper press part (6), 10 - steel press-belts (9a, 9b) circulating continuously, in a circulation direction, in the lower press part (7) and the upper press part (6), - at least one heatable heating plate (8a, 8b) in the lower press part (7) and upper press part (6) respectively, and - at least one actuator (11) in the lower press part (7) and/or the 15 upper press part (6), whereby pressure can be applied to the material (5) by means of at least one heating plate (8a, 8b) and one steel press-belt (9a, 9b). To achieve dewatering and a dewatering-method that will enable a considerably higher throughput of water-containing material, it is a feature 20 of the invention that the twin-belt press (4), when in operation, has at least a first, heating, section (A), where the material is subjected to pressures of below 4 MPa and heating-plate surface temperatures of above 160°C, and - downstream thereof (in the direction of travel) - at least a second, dewatering, section (B), where the material (5) is subjected to pressures 25 of greater than 4 MPa. Fig. 2 2784350v1 2/3 12 10 11 8a +-6 20a 9a 15 v -16 15 14 13 17 9b 20b 8b Fig. 2

Description

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12 10 11 8a

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Apparatus and Method for Dewatering a Material Containing Water

Description

The invention relates to an apparatus for dewatering a material that contains water, by means of pressure and heat, said apparatus having a) a device for metered delivery of the material, b) a transfer section, in which the material can be transferred - from a transport device, or directly - into a twin-belt press, and c) a twin-belt press with 1o - a lower press part and an upper press part, - steel press-belts circulating continuously, in a circulation-direction, in the lower press part and the upper press part, - at least one heatable heating-plate in the lower and upper press parts respectively, and is - at least one actuator in the lower press part and/or the upper press part, whereby pressure can be applied to the material by means of at least one heating plate and one steel press-belt.

The invention also relates to a method of dewatering a water-containing material by means of said apparatus.

In this invention, the term "water-containing material" may be understood as primarily meaning coal, particularly brown coal (lignite), or sludge. However, the invention is not intended to exclude other materials capable of being dewatered.

Energy production using brown coal (lignite) is a common process, in which, the higher the coal's moisture content is, the more inefficient the process will be. There are various methods of reducing the moisture content of brown coal or sewage-sludge by pressing or heating.

2784350v1

A device for metered delivery of the material onto a transport device is known in the art, from e.g. DE 10016944 Al.

DE 472419 C has already described a press for dewatering vegetable and mineral substances that have a high water content. This press has two endless belts, converging wedge-wise, with permeable walls attached to them that give rise to successive pressing chambers. Such an apparatus is very elaborate, and is only suitable for low speeds and low pressures.

DE 19535315 Al and DE 19537286 B4 disclose batch presses that can operate quasi-continuously. Due to their closed pressing chamber, lignite or sludge can 1o be heated with steam supplied to it. With such a plant, approximately 25 tonnes of lignite per hour can be dewatered down to the desired moisture content. Considering that, these days, a 1GW unit of a coal power plant requires over 800 tonnes of coal per hour, it is easy to see that the required throughput would be possible only with a large number of presses such as those described in DE 19535315 Al. Also mentioned in passing as prior art, in this published specification, are twin-belt presses such as those described in particular by the above-mentioned patent DE 472 419 C.

Therefore, the objective of the invention is to provide a dewatering apparatus, and a dewatering method using said apparatus, that enable a significantly higher throughput of water-containing material, in particular coal or sludge.

As regards the apparatus, this objective is achieved through the features of claim 1; as regards the method, it is achieved through the features of claim 8.

In particular, the apparatus is characterised in that, when operating, the twin-belt press has: at least a first, heating, section, where the material is subjected to pressures of less than 4 MPa and heating-plate surface temperatures of greater than 160OC; and - downstream thereof (in the direction of travel) - at least a second, dewatering, section, where the material is subjected to pressures of greater than 4 MPa and generally does not require any further heating.

Thus, in the invention, two processes that have up to now been performed successively, i.e at separate times, in one press station are now performed in two

2784350v1 different sections of a twin-belt press, thus resulting in a continuous dewatering process, which significantly increases the throughput of the material. The twin belt press does require a consecutive length of 70 metres or more; nevertheless, constructing such a twin-belt press is still much more economical than having to use a number of batch presses instead. As a rule, this twin-belt press's heating section will be somewhat longer than its dewatering section. In its heating section, the material is heated by very hot plates, between which the material is being transported. In this section, evaporation is kept within limits. The water contained in the pores is heated, and changes its material properties, with e.g. a 1o decrease in viscosity and surface tension. In the solids, fusions can occur, due to the high temperatures involved. Once the material is transferred to the dewatering section, in which the pressure is very high, the water within the material can be expelled by high pressure and discharged as a liquid and partly also as steam. The material is compacted, and leaves the twin-belt press as a flat product.

It is beneficial if, at least in the dewatering section, there are suction exhaust devices operating between the steel press belts, at least in sections, to deal with water and/or steam emerging from the material. In the enclosed space between the impermeable steel belts, the liquid squeezed out and the steam arising can be very easily extracted by suction. As a rule, the suction exhaust device is arranged, for this purpose, at the side of the twin-belt press, in such a way that the suction extraction openings are directed at the gap between the steel press belts. The suction exhaust device should be designed for about 0.2 to 0.6 bar vacuum relative to atmosphere, and an extraction volume of up to 200,000 m 3/h. This prevents moisture from condensing in the dewatering hall of the works building and possibly attacking machine parts. In addition, the suction exhaust device makes for better climate control in the premises. The evacuated condensate can also be used for energy in heat exchangers.

The suction exhaust devices preferably have lateral suction openings that are sealed off from the steel belts. Since slight losses due to leaks are immaterial, a relatively simple seal at the suction opening will suffice, and will undergo minimal wear, since its contact pressure with the circulating steel press-belt is low. The seal may even be able to

2784350v1 be spaced slightly apart from the steel press-belt, and thus experience no wear at all.

Preferably, at least one steel press-belt circulates together with a membrane belt that faces the material.

Particularly in the dewatering section, the membrane belt lets water and steam from the material pass through to the steel press-belt but holds solids back. Separating the liquid and gaseous water from the solids makes the material easier to dewater and more suitable for subsequent combustion.

Another advantageous provision of the invention is that the membrane belt 1o consists of a woven material or perforated belt with a mesh width of 0.1 to 20 pm. Such woven materials may be made of metal or of synthetic fibres. For perforated belts, metal materials are preferred. Their mesh size is adapted to the circumstances, particularly the material to be dewatered, so that reverse osmosis will occur. With a suitable mesh size, it is even possible to achieve an outcome in which, in the heating section A, the water scarcely passes through the membrane, whereas, in the dewatering section, it passes through with no problem. To ensure that the membrane always works properly, cleaning devices are provided in the membrane belt's return run.

A particularly preferred feature is that a screen belt is arranged between the steel press-belt and the membrane belt. The screen belt, whose openings are larger than those of the membrane belt, creates a space between the membrane belt and the steel press-belt, to accommodate the expelled steam and water. This facilitates their extraction, by suction, from this region, without pressure transfer being adversely affected. Also, channels may advantageously be provided within the screen belt, through which the steam and water can be conducted to the edge of the steel press-belt.

In an advantageous embodiment, the membrane belt and the screen belt are connected to each other. This prevents differential lateral running, and friction, between these two belts.

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Characterising features of the inventive dewatering method are that: the material is heated to at least 130°C in a first, heating, section of the twin-belt press, with pressures on the material of below 4 MPa and heating-plate surface temperatures of above 160OC; and is dewatered - downstream thereof (in the direction of travel) - in at least a second, dewatering, section of the press, with pressures of greater than 4 MPa on the material.

In the heating section, the water in the material is heated up and changes its material properties, as already described. Once it has passed into the dewatering section, the heated material can be pressed much more easily, so that water can 1o escape from it mostly in liquid form, and be removed by suction. In this way, the material loses more than half its moisture, measured as percent by weight.

Advantageously, the water and/or steam can be removed by suction at at-least one edge of at least one steel press-belt. In this way, the compression process in the twin belt press is not disturbed. In tests, pressures of below 4 MPa have proved sufficient in the heating section, whereas, in the dewatering section, pressures in the order of approximately 6 MPa have proved to be particularly effective.

Preferably, at least in the dewatering section, water and/or steam is pressed through a membrane belt that is impermeable to solids. Separating the liquid or gaseous water from the solids enables the material to be dewatered more easily, as already described in the disclosure of the device.

The invention will now be explained in greater detail through examples referring to the attached drawings. In the drawings:

Fig. 1 is a side view of an apparatus according to this invention,

Fig. 2 is a diagrammatic cross section through the inventive apparatus, and

Fig. 3 is a detailed, sectioned, view of the implementation of the dewatering section of the inventive apparatus.

Fig. 1 shows the inventive dewatering apparatus 1. First, the material 5 to be treated is spread out, by a metered-delivery device 2, onto a transport device. 3 These two devices are only indicated schematically, because they precede the

2784350v1 actual dewatering process. The metered-delivery device 2 is usually a storage bunker with a controllable release valve and spreader, and the transport device 3 is normally a conveyor belt. In this way, a "carpet" or "mat" of the material 5 to be dewatered is delivered into the twin-belt press 4 in section C.

The twin-belt press is composed of an upper press part 6 and a lower press part 7, which are supported by numerous frames 10. In both the upper 6 and lower 7 press-parts respectively, there is a water-and-steam-permeable steel press-belt 9a, 9b running round a deflection roller 19. Pressure can be applied to the material between the steel press-belts 9a, 9b. Looking from the material 5, there 1o is at least one heatable plate 8a, 8b on the other side of the steel press-belt 9a, 9b and within the latter's orbit, in both the upper press part 6 and the lower press part 7. To reduce the friction between the steel press-belt 9a, 9b and the associated heating plate 8a, 8b, revolving rolling elements 20a, 20b are also provided.

With the support of the frame or foundation, force is applied to at least one of the heatable plates 8a, 8b, and thus to the material 5, by means of at least one actuator 11. The heated plates also give off their heat to the respective steel press-belt 9a, 9b, thereby heating the material. The plates can be heated in a manner not shown in the drawings - e.g. by heat-transfer media conducted in channels; or electrically; or by induction.

The twin-belt press is divided into two sections, labelled A and B. In section A, which is the heating section, the material is brought to a high temperature, at low pressure. Even water inside the material is brought at least close to evaporation. For this, the heating surfaces of at least one of the heatable plates 8a, 8b are heated to over 160°C, with the pressure maintained at below 4 MPa. The heat of the heated plates is transferred to the steel press-belts 9a, 9b by radiation, convection, and thermal conduction, by way of the rolling elements 20a, 20b arranged between each heatable plate 8a, 8b and the associated steel press-belt 9a, 9b. To be able to transfer the amount of heat required to heat the material 5, it is necessary for the heated plates 8a, 8b to have a minimum surface temperature of 160°C.

2784350v1

Finally, the heated material reaches section B, the dewatering section, where the pressure is significantly higher than 4 MPa, preferably about 6 MPa. Under this high pressure, the majority of the water is expelled from the material, and, together with the evolving steam, is conducted from the side of the twin-belt press to the outside. To exhaust the water and steam, suction exhaust devices 12 are provided beside the dewatering part B of the twin-belt press 4. These are normally boxes, with suction openings 13 in the region between the steel press belts 9a, 9b and the discharge channels 14.

This is shown more clearly in Fig. 2, which is a schematic partial cross section 1o taken through the dewatering section B of the twin-belt press 4. Fig. 2 shows a rectangular frame 10 with a detail. Two actuators 11, normally hydraulic cylinders, are borne on the upper cross member. The number of actuators will vary, of course, depending on the width of the twin-belt press 4 and the material to be dewatered. The actuators' 11 force goes into the upper heatable plate 8a and is is able to push it down. The opposing element is the lower heatable plate 8b, which is mounted and supported on the lower frame part. Also provided, in both the upper press part 6 and the lower press part 7, are circulating steel press-belts 9a and 9b, between which the material 5 is pressed. The return runs of the steel press-belts 9a, 9b (for example, above and below the frame 10) are not shown in Fig. 2. Also not shown, for the sake of simplicity and clarity, are the heating medium feeds to the heatable plates 8a, 8b.

On both sides, there are suction exhaust devices 12, each with a suction opening 13 and a discharge channel 14 for steam and water. In the discharge channel, a partial vacuum of 0.2 to 0.6 bar is maintained by an exhaust fan (not shown). The suction opening is sealed vis-a-vis the two steel press-belts 9a, 9b by a sliding or non-contact seal 15.

Together with the lower steel press-belt 9b, there runs a membrane belt 16 and also, if necessary, a screen belt 17, in which case the membrane belt 16 and the screen belt 17 can form a unit.

In Fig. 3, the belts are again shown enlarged, in a sectional side view. Fig. 3 is bounded above and below by the heated plates 8a and 8b, which are cropped. The rolling elements 20a and 20b run on them at about half the speed of the

2784350v1 steel press-belts 9a and 9b. The upper steel press-belt 9a presses directly onto the material 5. Interposed between the material 5 and the lower steel press-belt 9b are the membrane belt 16 and a screen belt 17. The membrane belt 16 consists of a woven material or perforated belt. The passages in the membrane belt 16 and the screen belt 17 are not shown; but, for the membrane belt, mesh sizes of 0.1 to 20 pm are used, depending on the nature of the material 5. This membrane pore opening size allows water and steam, but essentially not solids, to pass through. The screen belt additionally provided in this embodiment has larger passage-opening widths. Their dimensions are such that they can accept 1o sufficient water and steam at the pressure provided in the dewatering section. In addition, discharge channels 18 may be provided, to conduct the output-product laterally, to the suction exhaust devices 12.

In this specification, the terms "comprise", "comprises", "comprising" or similar terms are intended to mean a non-exclusive inclusion, such that a system, method or apparatus that comprises a list of elements does not include those elements solely, but may well include other elements not listed.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

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Claims

1. A method for dewatering a material that contains water, by means of pressure and heat; with an apparatus having a) a device for metered delivery of the material, b) a transfer section, in which the material can be transferred - by means of a transport device, or directly - into a twin-belt press, and c) a twin-belt press with - a lower press part and an upper press part, - steel press-belts circulating continuously, in a circulation-direction, in the lower press part and the upper press part, - at least one heatable heating plate in the lower press part and the upper press part respectively, and - at least one actuator in the lower press part and/or in the upper press part, whereby pressure can be applied to the material by means of at least one heating plate and one steel press-belt, wherein the material is heated to at least 130 °C in a first, heating section of the twin-belt press, with pressures of below 4 MPa and heating-plate surface temperatures of above 160°C, and is dewatered - downstream thereof in the direction of travel - in at least a second, dewatering section of the twin belt press, with pressures of greater than 4 MPa.

2. The method as claimed in claim 1, wherein water and/or steam is removed by suction at at-least one edge of at least one of the steel press-belts.

3. The method as claimed in claim 1 or 2, wherein, at least in the dewatering section (B), water and/or steam is pressed through a membrane belt that is largely impermeable to solids.

4. An Apparatus for dewatering a material that contains water with a method according to any of claim 1 to 3; with a) a device for metered delivery of the material, b) a transfer section, in which the material can be transferred - by means of a transport device, or directly - into a twin-belt press, and c) a twin-belt press with - a lower press part and an upper press part,

- steel press-belts circulating continuously, in a circulation-direction, in the lower press part and the upper press part, - at least one heatable heating plate in the lower press part and the upper press part respectively, and - at least one actuator in the lower press part and/or in the upper press part, whereby pressure can be applied to the material by means of at least one heating plate and one steel press-belt, wherein, when operating, the twin-belt press has at least a first, heating section, where the material is subject to pressures of below 4 MPa and heating- plate surface temperatures of above 160°C, and - downstream thereof (in the direction of travel) at least a second, dewatering, section, where the material is subjected to pressures of greater than 4 MPa, wherein at least in the dewatering section, there are suction exhaust devices operating between the steel press-belts at least in sections, for vapour and/or liquids emerging from the material, wherein, at least in the dewatering section, at least one steel press-belt circulates together with a membrane belt facing the material, and wherein, between the steel press-belt and the membrane belt, there is a screen belt.

5. An apparatus as claims in claim 4, wherein the suction exhaust devices have lateral suction openings, which have a seal vis-a-vis the steel press-belts.

6. An apparatus as claimed in claim 4 or 5, wherein the membrane belt consists of a woven material or perforated belt with a mesh or hole width of 0.1 to 20 pm.

7. An apparatus as claimed in claim 4 or 5, wherein the membrane belt and the screen belt are connected to each other.