AU725794B2 - Method, filter press as well as control and regulating device to reduce the water content of solid materials and/or sludges - Google Patents

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: 9 9.

9 9*99* Name of Applicant: Maschinenfabrik J. Dieffenbacher GmbH Co.

Actual Inventor(s): Friedrich B. Bielfeldt Eckhard Kintscher Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: METHOD, FILTER PRESS AS WELL AS CONTROL AND REGULATING DEVICE TO REDUCE THE WATER CONTENT OF SOLID MATERIALS AND/OR SLUDGES Our Ref 522152 POF Code: 283870/283888 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1- 1A The invention concerns a method, a press as well as a control and regulating device to reduce the water content bound by capillary action in the fibre cells of carboniferous, finely pulverized solid materials and/or sludges, according to the generic part of patent claim 1.

One object of the invention is to enable the large-scale use of lignite by a new method using a thermo-mechanical dehydration, wherein the total efficiency of the current generation in the power station processes is improved and that the continuous throughput of large quantities of carbon-containing solid materials required for this purpose is achieved. To prevent a blow-out at the edges of the bulk material mat due to the steam pressure and to achieve a uniform thermal energy distribution over the pressing area without reducing the steam pressure at the edges a further technical solution for a plant and press is applied which does not contain or prevents the described disadvantages.

This objective is achieved by the method of combining the following process steps: a) an input material is used which at the commencement of the operating cycle is subjected to steam using a steam overheated up to a1500C in an essentially steam-tight enclosed pressure chamber which is pre-heated up to over 1000C, wherein i

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20 b) the compression pressure on the input material is greater than the pressure caused in the input material by the bulk density, corresponds approximately to the maximum of the applied steam pressure of 5 to 8 bar and subsequently c) after having reached a temperature of approx. a125°C in the input material 0the steam injection is terminated and depending on the grain size of the input 25 material a higher mechanical, specific compression pressure up to a maximum of bar will prevail to reduce the residual water content up to 20% of the weight.

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C:\WINWORD\GAY\NODELETE\5221 52.DOC Corresponding to the thermo-mechanical dehydration method according to Australian Patent Application No. 60639/96 it is possible to dehydrate lignite economically with a low usage of thermal and mechanical energy. To generate current from lignite with high moisture content the total efficiency of the power plant process can be clearly improved by connecting upstream the energy-advantageous method according to the invention to remove the water. In addition, when compared with known thermal drying methods, energy used for the vaporising of the water is saved.

A further objective of the present invention is to provide a plant to carry out the process steps according to Australian Patent Application No. 60639/96. This is achieved by that a circulating dispersion belt is passed through a pressure chamber integrated in a single-stage press and this pressure chamber is opened and closed by a lock system in accordance with the cycles of the process stages, wherein the main parts of the plant comprise a reversible, continuously operating dispersion machine, an intermittently operating filter press which can be heated and a dispersion belt box system with a rectangular dispersion pattern for the lignite granules, whose endless dispersion belt is guided by two endless lateral steel belts through a pressure chamber, which can be sealed gas-tight, in the press and wherein transversely to the direction of transport at the entry and outlet of the 20 pressure chamber it can be closed and opened by a blade which can travel up and down and a gate valve.

**This two-stage process of thermo-mechanical dehydration leads to that with the supply of thermal energy by means of steam at the end of the mechanical S"squeezing the compressed dried lignite material in the enclosed pressure chamber o• 25 of the filter press and the coal and the residual moisture acquire the steam temperature, i.e. the residual moisture is expanded when the pressure plate moves up and is released as steam. There is therefore the problem, depending on the temperature (from 1250C C:\WINWORD\GAY\NODELETE\522152.DOC to 200'C and steam pressure of up to approx. 20 bar), to dispose of this residual moisture in a controlled manner during the discharge of the press. When the top pressure plate moves up while the pressure chamber is closed, i.e. the hydraulic bulkhead walls are placed in position and the locks are closed, the residual moisture in the dehydrated lignite slab is released as steam. If the opening movement of the pressure plate is carried out slowly, a steam expansion pressure occurs in the expansion chamber corresponding to a coal temperature of approx. 200 0 C and a steam pressure of approx. 16 bar. This would have the disadvantage, that in the case of a discharge of this expansion steam through the corresponding discharge channels these channels or lines have to be designed in accordance with the existing high steam pressure. Without a targeted disposal of the vapour within the press in the outlet region of the filter press large quantities of vapour steam would occur, which have to be seized by means of additional suction devices and disposed of by means of expensive wet dustremoving devices. However, since the thermo-mechanical dehydrating process is carried out in an intermittent manner, the vapour steam generated (vapour steam in this case is a mixture of steam and coal dust) at the end of each press cycle has to be introduced to the wet dust-removal by additional suction devices, wherein the additional intermittently occurring quantities of dust can be seized only within a *e relatively short time of approx. 5 to 10 of the total cycle time during the discharge of the filter press. This means that the suction and dust-removing devices have to be dimensioned to correspond with these short-period quantity flows, requiring very high investments. A further disadvantage is that the vapour steam to be exhausted as heat quantity is lost as energy.

The object of the invention is to provide a method, according 5 to which the major part of the residual moisture remaining in the dehydrated lignite slab at the end of the mechanical compression can be removed deliberately without expensive suction devices before the discharge from the pressure 'chamber and in addition the amount of heat contained in the residual moisture can be used thermally.

When the pressure chamber is opened quickly by moving up the movable pressure plate, two decisive advantages can be made use of. Due to the higher expansion speed a lower steam pressure is created in the steam expansion chamber and due to the high expansion speed the dehydrated lignite slab (dry lignite compressed material) is impact-like loosened due to the explosion-like expansion steam pressure, i.e. corresponding to the original grain size of the raw lignite granules the lignite slab obtains a loose crumbly state, which is very advantageous for the subsequent fine grinding, since due to this smaller grinding units and consequently more cost-effective machines can be used. The basic concept of the teaching according to the invention is based on the cyclical release of the heat of the steam in a water storage condenser system, while, in turn, this accumulated amount of heat can be introduced to a further use via one or several heat exchanger systems over the entire cycle period, for example to heat the air for the space itself for the entire plant as well as the amount of air required for postdrying the dehydrated and dried lignite slab and to heat the combustion air for the combustion chambers or the water in the turbine circuit. In addition to the use of the enthalpic heat from the vapour for energy, there are considerable economic 20 advantages by combining between the cyclical heat delivery of the vapour S.condensate and the permanent removal in the heat exchanger connected downstream in a ratio of the time periods of ten to one by minimising the establishment costs of the plant also in a ratio of ten to one.

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Co C:\WINWORD\GA \NODELETE\522152.DOC Further advantages of the invention become apparent from the following description of the drawing and the auxiliary and subclaims. They show in: Fig.l a schematic illustration of the filter press according to the invention with the raw lignite granule supply and the vapour condenser heat-exchanger system connected downstream to the vapour lock system to carry out the method, Fig.2 a section C-C from Fig.12 as an alternative to the lock system according to Figs.6 and 7, Fig.3 the situation according to section C-C according to Fig,12, yet at the end of the mechanical compression for the hot water squeezing, Fig.4 the vapour expansion in the expanded steam chamber of the filter press with open outlet valve, in a section B-B from Fig.2 the arrangement of the cylindrical valve body, the vapour lock system at the outlet of the filter press at the end of the mechanical final compression, analogously to Fig.3, 9 9 9* 99 9 9 *.2 99 9.

9 9 o 9* 9 9 0* 9 9 9 Fig.6 Fig.7 the vapour lock system according to Fig.6 when the press ram is in the top position analogously to Fig.4 and the outlet lock II is open analogously to the outlet ram according to Fig.4, Fig.8 an alternative of the execution according to Figs.2 and 6 of the vapour lock system, Fig.9 the expanded steam situation when the pressure chamber is open, Fig.ll Fig.12 a section A-A from Fig.8 showing the arrangement of the top slot openings in the bulkhead walls, the filter press in side view with the locks I, II and

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the filter press with the locks I, II and III as well as the hydraulically adjustable bulk head walls, in section E-E from Fig.ll, the operating situation, wherein all locks I, II and III are open and the discharge or charging of the pressure chamber is started, in section F-F from Fig.12, and Fig.13 Fig.14 the supply of the filter press shortly before the end of this step according to Fig.13.

The drawing according to Fig.l shows the subject matter of the invention comprising the part of the plant for a thermomechanical dehydrating system for raw lignite granules 6, consisting of:

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A) a dispersing section for an intermittent bed-like dispersion 2 of the input material on the dispersion and supply belt 4, B) a single-stage filter press 5 with integrated pressure chamber and lock system, and C) the discharge transport of the squeezed lignite slab 31 from the pressure chamber 40 with the pre-breaking device 74 for •a subsequent grinding drying.

The dispersing section A of Fig.l shows further the continuous 5 transfer of the raw lignite granules 6 from the transfer belt 2 into the stationary hopper 1. The stationary dispersion machine 3, which forms a constructional unit with the hopper 1, disperses the raw lignite granules 6 onto the dispersion and supply belt 4, which is circulating through the filter press The dispersion and supply belt system (see also Figs.ll and 12) consists of the bottom endless dispersion and supply belt 4 and the bulkhead walls 63 provided vertically left and right from it within the filter press. At the same time the dispersion and supply belt 4 is constructed as a steam-permeable woven metal belt and is driven synchronously through the pressure chamber of the filter press 5. The raw lignite granules 6 are dispersed by the dispersing machine 3 up to the piling height H with an accurate geometrical rectangular cross-section and following this introduced unchanged into the pressure chamber and taken out after being compressed.

Simultaneously with the piling of the raw lignite granule bed onto the dispersion and supply belt 4 and the removal of the lignite slab 31 from the press plant the introduction of the next raw lignite granule bed is carried out. Before the starting up of the dispersion and supply belt 4 the pressure chamber 40 is opened at the entry 26 and outlet 27 and the bulkhead walls 63 of the pressure chamber 40 are pressure relieved, i.e. released. The transport of the bulk raw lignite bed to the exit 27 is carried out by numerical controlling the dispersion and supply belt 4. After the dispersion and supply belt has reached the exit lock II, the pressure chamber 40 is closed again, this means that the bulkhead walls 63 are placed back (approx. 5 mm pressure stroke) and the inlet 26 and outlet 27 are closed again.

S The filter press 5 with integrated pressure chamber and lock system in the region B of the pressure chamber press is executed according to the drawing as a stationary single-stage piston press. The dispersion and supply belt 4 travels with the raw lignite granulate 6 endlessly from the dispersion section A into the pressure chamber press region B, where it slides over 5 the top, fixed heated pressure plate 13 of the pressure chamber The pressure chamber system is made up of the following functional elements: the bottom, stationary pressure plate 13, mounted in the press frame 0 the bulkhead walls 63, erected vertically on both longitudinal sides on the left and right, which in turn are pressed laterally by means of the hydraulic short-stroke cylinders 20 against the top pressure plate 17, which is driven by the hydraulic pressure cylinders 34, the long-stroke cylinders 34, which act vertically from the top, and the short-stroke cylinders 20, which press the pressure chamber 40 horizontally from both directions. The cylinders 34 and 20 are allocated to the press frame 30, as well as to the longitudinal sides and end faces of the pressure chamber The bulkhead walls 63 inside the filter press 5 are regulated by means of hydraulic short-stroke cylinders 20 by way of lateral pressure, i.e. relieved during the transporting movement of the dispersion and supply belt 4 and with varying lateral compression forces against the top pressure plate 17 during the steam injection and the compressing process. The top pressure plate 17 is sealed gas-tight against steam pressure by an elastic rubber seal 88. The bulkhead walls 63 are in turn sealed gas-tight with rubber-elastic seals 89 against the sealed bottom edge of the pressure plate 13, when by means of the hydraulic pressure cylinders 23 the bulkhead walls 63 are 0. pressed vertically downwards during the standstill of the dispersion and supply belt 4.

Simultaneously with the entry of the dispersed raw lignite granules 6 into the pressure chamber 40 the gate valve 28 of the outlet 27 is closed in a vertical movement by means of the hydraulic adjusting member 36 for the subsequent steam 5 injection process. At the same time the gate valve 22 in the inlet 26 is moved up by the hydraulic adjusting member 37 so far, i.e. released, that the dispersed raw lignite granules 6 with the piling height H can be moved trouble-free into the pressure chamber The controlled removal of the expanded steam from the pressure chamber 40 after the operating cycle of the filter press 5 is carried out according to the invention in accordance with the following method of a regulated lock system in the outlet region of the pressure chamber 40 according to Figs.l, 6 and 7.

The operation is as follows: The movable pressure plate 17 opens fast while the pressure chamber 40 is still closed. The starting position for this corresponds to Fig.6. Due to the explosion-like loosening a steam-coal dust mixture occurs in the expanded steam chamber 81, while the pressure chamber 40 is understood with closed filter press 5 and the expanded steam chamber 81 is understood with open filter press 5. With the commencement of the moving up of the pressure plate 17, but at least at the end of its movement, the outlet lock II is opened. Since the outlet lock II with a gate valve 28 is constructed over the entire width of the press, a large relieving cross-section can be opened suddenly in the direction of the vapour condenser 82. In the course of this operation according to Fig.7 the outlet lock III with the gate valve 90 remains closed as before, so that the vapour flows in the direction of the regulated outlet valve .5 The opening velocities of the outlet lock II and of the outlet valve 80 are regulated so that a controlled steam flow velocity is set in the opening cross-sections of these valve units, thus preventing that due to too great a flow velocities increased *i quantities of coal dust and granules would be introduced into the vapour condenser 82. As a rule, the opening of the pressure plate 17, of the outlet lock II and of the outlet valve 80 is controlled staggered in time relative to each other with a sequential switching on, so that with the charge-like occurring vapour 93 the expansion time of the steam can be set to <10 5 of the total cycle time in the discharge of the vapour 93 to the vapour condenser 82, without carrying with it large quantities of coal dust and granules.

The vapour condenser operates as follows: During the steam expansion time of 10 of the total cycle time the vapour 93 flows into the vapour condenser 82. During this time a corresponding quantity of water flows by gravity from a water container 83, which is provided above the vapour condenser 82, through the vapour condenser 82 and accumulates the released heat when, for example, a quantity of water with water temperature is added from the water container, thus the water will' take up a temperature of approx. 60°C in the condenser coil of the vapour condenser 82. The quantity of water is now introduced to a heat exchanger 84 with the advantage that now the stored heat can be transferred to further external heat exchanger systems 85 and 86 from this heat exchanger 84 over the entire cycle time in a quasicontinuous manner. Consequently, the total system can be designed correspondingly smaller and more cost-effectively. As a further advantage, the condensate from the expanded steam, which has a water temperature of 100°C, can be also used as energy via the heat exchanger system 86. A solid material separator 77 is connected upstream to the entire vapour condenser system to absorb coal dust and granule particles which may have been dragged along. Due to the expansion over the large cross-sections of the outlet lock II and the o:l expansion lock IV to the vapour condenser 82 due to the to pressure fall of, for example, 10 bar in the steam expansion chamber 81 to the vapour condenser 82 a relief to the normal pressure will occur, i.e. no additional suction device is necessary.

After the steam expansion time of 10 of the total cycle time the additional lock III, according to Fig.7, is opened by the gate valve 90 and the discharge of the filter press 5 can take place, as is shown in Figs.13 and 14.

A second, alternative, solution is the execution illustrated in Figs.2, 4 and 5. The operation is carried out as follows: 35 During the supply of the filter press 5 according to Fig.13 and during a dehydrating process until the final compression according to Fig.3, the cylindrical outlet openings 91, provided in the hydraulically adjustable bulkhead walls 63, are closed. According to Figs.2, 4 and 5 any number of these cylindrical outlet openings 91 can be provided between the hydraulic adjusting members 20, as a matter of fact so frequently that an adequately large outlet cross-section, as described above, can be opened during the steam expansion phase according to Fig.4. The advantage of this execution when compared with the above described alternative is that in the case of extremely long filter presses 5 the cross-section of the openings on both longitudinal sides of the pressure chamber 40 can be provided in a correspondingly large number and the expansion of the vapour 93 to the expansion lock IV is assured.

The cylindrical execution of the closing ram results in a selfcleaning effect for the outlet openings 91. The expansion lock IV is in turn allocated to the closing rams 92 in the outlet openings 91, so that the progress of the process takes place analogously to that described in Figs.6 and 7.

A further alternative solution is illustrated in Figs.8, 9 and as an alternative to the execution according to Figs.2 to The operation is carried out as follows: The supply situation in Fig.8 is illustrated analogously to Fig.13. This means that in the lateral hydraulically adjustable bulkhead walls 63 longitudinal slots 87 are provided above the piling height H of the raw lignite granules 6 which, during the compression process, i.e. the downward movement of the pressure plate 17, are automatically closed.

In the steam expansion situation according to Fig.9 the lateral longitudinal slots 87 will become free automatically when the pressure plate 17 is opened, so that the vapour 93 can be introduced to the vapour condenser 82 through the expansion e.lock IV.

In Fig.9 it can be Seen from the indicated speed progress of 5 the pressure plate 17, that at the commencement of the opening process a very high opening speed is set, but when reaching the slot openings 87 the speed of the pressure plate 17 is braked impact-like, so that a controlled steam expansion speed is set in the direction of the vapour condenser 82, as this has been shown already in Figs.6 and 7.

In the following the execution of the sealing system to the pressure chamber 40 in the filter press 5 is described.

In all examples of applications the steps of the process are carried out with the expanded steam discharge in the pressure chamber 40 enclosed on all sides. Only the pressure plate 17 moves inside the raw lignite and dry lignite regions, due to which the lateral walls of the pressure plate 17 and the inside walls of the adjustable bulkhead walls 63 and of the valves 22 and 28 are subjected to a natural closing load by the material to be compressed. For this reason the pressure plate 17 is constructed on all sides with its rectangular, vertical walls as a smooth steel body. The sealing elements are provided on the external walls, i.e. on the hydraulically adjustable bulkhead walls 63 and the gate valves 22 and 28 of the inlet lock I and the outlet lock II, in fact in the upper region of this hydraulically adjustable walls so that in the top position of the pressure plate 17 the seal 88 acts always in the wearfree area. In the case of the lateral bulkhead walls 63 the seal 88 is against the pressure plate 17 in the upper region of the bulkhead walls 63 and the seal 89 against the bottom pressure plate 13 is in the bottom region of the bulkhead wall 5 63. The provision of the seals 88 and 89 is chosen so that either the seal 88 is pressed against the pressure plate 17 and the bottom seal 89 against the fixed pressure plate 13 by means of the hydraulic adjusting member 20 via the bulkhead walls 63, so that an automatic seal will occur. In case of the lock system described, e.g. Figs.6 and 7, the top seal is pressed against the vertical wall of the pressure plate 17 by means of the locking kinematics 35, in the bottom region a self-sealing takes place, for example on the coal itself, inasmuch that the gate valves 22 and 28 with their bottom end faces 94 are :35 pressed vertically against the respective coal bed by means of the hydraulic adjusting members 36.

Claims (9)

1. A method for reducing the water content, bound by capillary action in the fibre cells of pulverized solid carboniferous materials and/or sludges, especially raw lignite, through the effects of thermal energy and pressure on the input material to be dehydrated, wherein the thermal energy consisting of superheated steam and the mechanical energy as surface pressure are supplied and exerted on the input material in a pressure chamber, the input material at the beginning of the operating cycle is vaporised in an essentially steamtight closed pressure chamber preheated to over 1 00C and with steam superheated up to ;150C, whereby the compression pressure on the input material is more than or equal to the pressure existing in the input material because of the piling density, to a maximum of approximately 5 bar to 8 bar in the introduced steam pressure and after reaching a temperature of approximately ;1250C in the input material the steam injection is terminated and, depending on the size of the grains in the input material, a high mechanical specific pressure in the press comes into effect, up to a maximum of 75 bar for the reduction to a residual water content of up to 20 percent by weight, wherein the vapour generated after the opening of the filter press is expanded further in a space to be opened subsequently and is discharged from there into a vapour condenser with controlled expansion velocity. 9 20

2. A method for reducing the water content, bound by capillary action in the fibre cells of pulverized solid carboniferous materials and/or sludges, especially raw lignite, through the effects of thermal energy and pressure on the input material to be dehydrated, wherein the thermal energy consisting of superheated steam and the mechanical energy as surface pressure are supplied and exerted on the input material in a pressure chamber, the input material at the beginning of the operating cycle is vaporised in an essentially steamtight closed pressure chamber preheated to over 100C and with steam superheated up to a1500C, whereby the compression pressure on the input material is more than or equal to the pressure existing in the input material because of the piling density, to a maximum of approximately 5 bar to 8 bar in the introduced steam pressure and after reaching a temperature of approximately 21250C in the input materialthe steam injection is terminated and, depending on the size of the grains in the input material, a high mechanical specific C:\WINWORD\GAYkNODELETE\522152.DOC pressure in the press comes into effect, up to a maximum of 75 bar for the reduction to a residual water content of up to 20 percent by weight, in particular according to claim 1, wherein the amount of vapour heat generated after each operating cycle is delivered to a first water storage condensate system, the amount of heat accumulated in this process is conveyed to one or several heat exchanger systems and from there to a further application.

3. A method according to claim 2, wherein the amount of vapour heat generated is transferred intermittently to a first water storage condensate system, which corresponds to approx. 10% of the time of an operating cycle, and that the amount of heat of the first water storage condensate system is transferred continuously to a second water storage condensate system.

4. A filter press to carry out the process according to one or several of the claims 1 to 3, including an expansion chamber provided downstream from the filter press and connected with the pressure chamber via a gate valve, which expansion chamber surrounds in a sealing manner the rest of the lignite slab dehydrated in the preceding operating cycles over the dispersion and coating belt with a further gate valve and wherein this expansion chamber is connected with a vapour condenser via a controllable discharge valve.

5. A filter press according to claim 4, wherein in their top halves the bulkhead S. 20 walls have cylindrical and/or rectangular openings or slotted openings, while the S. So. cylindrical outlet openings can be closed off by means of closing rams.

6. A filter press according to claim 4 and 5, wherein the moving pressure plate is constructed on all sides with vertical walls as a smooth steel body.

7. A filter press according to claims 4 and 6, wherein sealing elements are provided in the grooves of the bulkhead walls so that in the top region they seal the moving pressure plate and in the bottom region the fixed pressure plate. S o 09*0o8. A control and regulating device to carry out the method according to claim 1, wherein for a controlled flow velocity of the vapour in the expansion chamber and 5 5 S0: from it through the expansion lock in the vapour condenser the bulkhead walls, the gate valve, the outlet ram and the outlet valve are controllably constructed with regard their opening speeds.

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9. A control and regulating device to carry out the process according to claim 8, wherein the upward movement of the pressure plate and the opening of the lock and of the outlet valve are controlled staggered in time by a sequential switching on in such a manner that the discharge of the vapour from the expanded steam chamber is set to approx. .510% of the total cycle time. A method according to claim 1 substantially as hereinbefore described with reference to any of the figures. DATED: 12th March, 1998 PHILLIPS ORMONDE FITZPATRICK Attorneys for: 0 Lv- Ah MASCHINENFABRIK J. DIEFFENBACHER GmbH Co. S* 0o O* *o C:\WINWORD\GAY\NODELETE\522152.DOC