WO1996006673A1

WO1996006673A1 - Method and apparatus for the equalization of pressure in a piston feeder

Info

Publication number: WO1996006673A1
Application number: PCT/FI1995/000448
Authority: WO
Inventors: Risto Laukkanen; Reijo Kilpeläinen
Original assignee: Andritz Patentverwaltungs GmbH
Current assignee: Andritz Patentverwaltungs GmbH
Priority date: 1994-08-26
Filing date: 1995-08-23
Publication date: 1996-03-07
Anticipated expiration: 1997-02-26
Also published as: AU3258995A; FI95504B; FI943915A0; FI95504C

Abstract

The invention relates to a method and an apparatus for the equalization of pressure when using a piston feeder (10, 11) for feeding material into a pressurized space (1). The method involves the introduction of material into a cylinder space (8) included in the piston feeder, closing and pressurizing the cylinder space (8), and using a piston (11) included in the piston feeder for advancing the material into the pressurized space (1). According to the invention, a compression piston (52), fitted in a compression cylinder (50) connected to the pressurized space (1), is driven simultaneously with the piston (11) of the piston feeder such that a pressure in the pressurized space (1) remains substantially unchanged and that the kinetic energy of said compression piston (52) is used for operating the piston (11) of the piston feeder.

Description

METHOD AND APPARATUS FOR THE EQUALIZATION OF PRESSURE IN A PISTON FEEDER

The invention relates to a method as set forth in the pream¬ ble of claim 1 and to an apparatus as set forth in the preamble of claim 4 for the equalization of pressure when feeding material into a pressurized space by means of a piston feeder.

Patent application FI A 921403 discloses a method and appa¬ ratus for feeding material into a pressurized space. This prior known solution involves the use of two pistons or plungers one nested inside the other, the material to be fed being first introduced into a piston-cylinder through a charge opening which is shut by bringing the outer piston to a bottom position in the piston-cylinder. Thereafter, the inner piston operable within the outer piston is used for carrying the material into a pressurized space. A gate leading to the pressurized space is opened after the charge opening has been shut and separate pressure and gas sources are used for maintaining the pressure as well as the gas composition in the cylinder as equal as possible to that existing in the pressurized space.

In the above-described pressure feeder, it is possible to maintain a sufficiently high pressure at various operating stages of the feeder. On the other hand, when material is forced by means of a piston or plunger into a pressurized space, the volume decreases with a resulting increase of pressure. In some applications, e.g. when feeding a fuel for the combustion in a pressurized space, it is nevertheless very important to avoid any upward pressure fluctuations as well. On the other hand, a high energy output is required for operating the inner piston because of the pressure increase. This has been achieved by using pressure accumula¬ tors, which increase the price of the apparatus. An object of the present invention is to eliminate some of the prior art deficiencies and to create a new solution which satisfies the operating requirements at all stages of operation. In order to achieve this, a method of the inven- tion is characterized by the specific features set forth in the characterizing clause of claim 1 and an apparatus of the invention is characterized by the specific features set forth in the characterizing clause of claim 4. The specific features of preferred embodiments of the invention have been defined in the non-independent claims.

A solution of the invention is capable of securing the pressure fluctuations within an acceptable range as material is fed into a pressurized space by the high-speed action of a feed piston. The energy required for a piston feeder in the delivery of material is preferably acquired from a pressurized space. In fact, all that is required is to overcome the resistance caused by kinetic frictions of the pistons. The power acquired by the apparatus from external energy sources does not show sudden fluctuations. The energy demand is lower and no pressure accumulators are needed to produce a high peak power for a piston, feeder.

The pressure differences between a carburator and a pressure chamber at various stages of material feed and process can be minimized. The gas used in high-pressure combustion is nitrogen. A solution of the invention is capable of consid¬ erably reducing the loss of nitrogen. On the other hand, by controlling the pressure difference it is possible to block the escape of combustion gases from the carburator back into the feeding chamber.

The invention will now be described in detail by means of one embodiment thereof with reference made to the accompany- ing drawings, in which

fig. 1 shows a piston feeder exploiting the invention, - fig. 2 shows an equalizing piston of the invention and

- fig. 3 shows various operating stages in a solution of the invention.

Fig. 1 illustrates a piston feeder for delivering material into a pressurized space. Regarding the feed of material, the apparatus corresponds essentially to that described in the Patent application FI A 921403. The apparatus is used for feeding a solid fuel into a pressurized silo 1 by carry- ing the fuel along a supply pipe to a connector 30 included in the apparatus. The housing of a solid-material feeding apparatus comprises a cylinder 8, whose wall is provided with an opening 28 in line with the connector 30 for delivering a solid material into the apparatus. The cylinder 8 is provided with a cover 31 which is fastened to the flanged top rim of the cylinder. The bottom rim of the cylinder is provided with a collar 32, to which is fastened a collar 33 included in a feeding chamber 12 and located below the cylinder. Between the collars or flanges 32 and 33 is fitted a spacer 34 and the inner surface of the spacer is provided with a gasket 40.

A piston 9 is operated in the cylinder 8 by means of a hydraulic actuator 35 mounted on the cover 31. In its rear- ward position, the piston has its leading edge flush with the top edge of the opening 28 such that the opening is open and, its forward position, the piston's leading edge is fitted to gasket 40 between cylinder 8 and feeding chamber 12, said feeding chamber 12 becoming tightly sealed on its side facing the cylinder 8. At the same time, the piston shuts off said opening 28 in the wall of cylinder 8. The piston 9 comprises an outer piston 10 and an inner piston 11, which is operable relative to the outer piston 10. In its rearward position, the inner piston lies within the outer piston and its travel path extends in its forward position all the way to the bottom of feeding chamber 12. The inner piston is operated by means of a hydraulic inner- piston actuator 36 , which is connected via a conduit 56 and control elements to a pressure cylinder 50 which the inner piston receives its operating energy from, as described hereinbelow. Between the inner piston 11 and the outer piston 10 are fitted gasket rings 37 for sealing the inter- piston contact surface. The gasket rings can be teflon- coated steel rings and tha outer piston is provided with corresponding grooves therefor.

The bottom rim of feeding chamber 12 is fitted with a pres¬ sure gate 13 pivotable about a hinge pin 38 and providing a closure means between the feeding chamber 12 and a space 39 leading to the silo 1. The space 39 is defined by a wall 42 having its bottom section provided with a collar 44 to which is fastened a collar 46 included in the pressurized silo 1. The material feed into the silo 1 is described sequentially hereinbelow in reference to fig. 3.

In accordance with the present invention, the silo 1 is provided with a pipe 48 to connect therewith a compression cylinder 50 with a compression piston 52 fitted therein. As described in more detail hereinbelow with reference to fig. 2, the compression piston 52 is part of a hydraulic mecha¬ nism 54, which is further linked by way of a hydraulic cylinder 66, a valve mechanism 72 and a hydraulic piping 56, serving as energy transmitters, to a drive unit for the inner piston 11 of a piston feeder. The hydraulic mechanism 54 consists of said compression cylinder 50, inside which is fitted the compression piston 52 sealed against the inner walls of the cylinder 50 by means of gaskets 58 mounted on the piston. The compression cylinder 50 is fastened by its bottom collars or flanges 60 to a spacer element 62, which is further fastened to the pipe 48 extending to the silo 1. The bottom section of said spacer element is fitted with a filter 63 for blocking the passage of solid material from the pressurized silo into the compression cylinder. The filter can also be located in some part of the pipe 48. The compression cylinder has its top collar 64 fastened to a bottom plate 68 included in the hydraulic cylinder 66 mount¬ ed thereupon. Inside the hydraulic cylinder is fitted a hydraulic piston (not shown), which is permanently linked to a rod 70 included in the compression piston 52 and extending through the bottom plate 68. On top of the hydraulic cylin¬ der is the valve mechanism 72 for controlling a hydraulic fluid as required by various operating sequences of the apparatus. The valve mechanism is connected means of a pipe 74 with the bottom section of the hydraulic cylinder below the hydraulic piston. Extending from the valve mechanism is also the pipe or conduit 56 to the drive unit for the inner piston of a pressure feeder, as pointed out above. The valve mechanism further includes hydraulic pumps for pumping a hydraulic fluid to various sections of a hydraulic system, as described hereinbelow. The bottom plate of the hydraulic cylinder is provided with an opening 76, which is fitted with an indicator 78 showing the position of the piston.

Various operating sequences for a method of the invention will now be described with reference to figs. 3 a) - g). In this exemplary embodiment, the duration of a single full working sequence or cycle is about 30 seconds.

In the sequence of fig. 3 a) the outer piston 10 is re¬ tracted to a rearward position and the pressure gate 13 is closed. Above the pressure gate 13 exists an atmo¬ spheric pressure and below e.g. a pressure of 30 bars. A charge 80 of solid material is delivered through the feeding connector on top of the pressure gate. The com¬ pression piston 52 lies about half-way down the compres¬ sion cylinder 50 and being advanced towards the bottom of the compression cylinder by using the valve mechanism for pumping a hydraulic fluid through the pipe 74 from below to above the hydraulic piston. The outer piston 10 is extended to a forward position towards the pressure chamber such that its leading edge comes into a contact with the sealing surface included in the junction between the cylinder and the feeding chamber (fig. 3 b). The inner piston 11 lies within the outer piston 10 at this point. The solid material 80 is retained in an isolated space whose pressure is equalized with the space below the pressure gate 13, the latter space being in communication with the pressurized feeding silo. This is effected by introducing into this space a gas having a pressure equal to that in the feeding silo. The final pressure equalization is effected by opening a valve (not shown) included in a pipe connecting said spaces. At the same time, the compression piston 52 is almost in its bottom position, which it reaches prior to opening the pressure gate 13 (fig. 3c).

In this sequence of a cycle, the valve mechanism is con¬ trolled such that the silo pressure, acting through the pipe 48 on the bottom surface of the compression piston, is transmitted under the control of said valve mechanism 72 through the hydraulic mechanism 66 and piping 56 to act on and operate the inner piston of a pressure feeder. Thus, the compression piston 52 travels to its top posi- tion and the inner piston 11 of a pressure feeder pushes to the forward position towards the pressurized space (fig. 3 ), the solid material charge 80 progressing into the space over on the other side of the gate. Since the pressurized space has a volume which remains constant during this temporally relatively short sequence, all that the piston-operating mechanisms are required to produce is a force needed for overcoming the kinetic frictions of the inner piston and compression piston.

Following the feed of material, the pressure gate 13

(fig. 3 e) is closed and the inner piston 11 of a pres¬ sure feeder is retracted to the rearward position (fig. 3 f) and the compression piston of the compression cylinder is commenced towards the bottom position by means of the valve mechanism. Finally, the outer piston 10 is retract¬ ed to its rearward position for the introduction of a subsequent charge of solid material and the compression piston is advanced to its bottom position (fig. 3 g). This is followed by commencing another cycle, as described above.

In the method, the outer and inner pistons as well as the pressure gate and compression piston and valves are con¬ trolled relatively synchronized, whereby the pressure gate can only be open when the feeding chamber is pressurized and the outer piston is in a tight abutment against the top edge of said feeding chamber to seal the pressure chamber. The operating equipment for the pistons and a drive mechanism (not shown) for the pressure gate are preferably linked to each other. There are several options to achieve this.

The invention has been described above by illustrating one embodiment thereof. However, the description must not be regarded as a limitation to the scope of protection of the invention, but it may vary within the range afforded by the following claims.

Claims

1. A method for the equalization of pressure when using a piston feeder (10, 11) for feeding material into a pressur- ized space (1), said method involving the introduction of material into a cylinder space (8) included in the piston feeder, closing and pressurizing the cylinder space (8), and using a piston (11) included in the piston feeder for ad¬ vancing the material into the pressurized space (1), c h a - r a c t e r i z e d in that a compression piston (52), fitted in a second cylinder (50) connected to the pressurized space (1), is driven simultaneously with the piston (11) of the piston feeder such that a pressure in the pressurized space (1) remains substantially unchanged and that the kinetic energy of said compression piston (52) is used for operating the piston (11) of the piston feeder.

2. A method as set forth in claim 1, c h a r a c t e r i ¬ z e d in that the kinetic energy of said compression piston (52) is transmitted from the compression piston by way of energy transmitting elements (66, 72, 56) to driving equipment for the piston (11).

3. A method as set forth in claim 2, c h a r a c t e r i - z e d in that the compression piston (52) is returned during the intervals between subsequent material feeding cycles.

4. An apparatus for feeding material into a pressurized space (1), said apparatus comprising a piston feeder (8, 10, 11) which includes a cylinder space (12), wherefrom the material is transferable by means of a feeding piston (11) of said piston feeder into the pressurized space (1), c h a r a c t e r i z e d in that the pressurized space (1) has connected there with a compression cylinder (50), provided with a compression piston (52) which is in communication with the pressurized space (1) and the compression piston (52) is by way of energy transmitting elements (66, 72, 56) in communication with the feeding piston (11), which is operable by the action of a force acting on the compression piston (52) of said pressurized space (1 ) .

5. An apparatus as set forth in claim 4, c h a r a c t e ¬ r i z e in that said energy transmitting elements

(56, 66, 72) include a hydraulic cylinder (66), a valve mechanism (72) and a hydraulic piping (56).

6. An apparatus as set forth in claim 5, c h a r a c t e ¬ r i z e d in that alongside the hydraulic cylinder (66) is a shunt pipe (74), whereby the fluid contained in the hydraulic cylinder (66) can be supplied on the opposite sides of a hydraulic piston according to the operating sequences of the apparatus.

AMENDED CLAIMS

[received by the International Bureau on 22 January 1996 (22.01.96); original claims 1-6 replaced by new claims 1-5 (2 pages)]

1. A method for the equalization of pressure when using a piston feeder (10, 11) for feeding material into a pressur- ized space (1), said method involving the introduction of material into a cylinder space (8) included in the piston feeder, closing and pressurizing the cylinder space (8), and using a piston (11) included in the piston feeder for ad¬ vancing the material into the pressurized space (1), which pressurized space (1) has connected there with a compression cylinder (50) provided with a compression piston (52) which is in communication with the pressurized space (1), c h a ¬ r a c t e r i z e d in that the compression piston (52), fitted in the cylinder (50), is driven simultaneously with the piston (11) of the piston feeder such that a pressure in the pressurized space (1) remains substantially unchanged and that the kinetic energy of said compression piston (52) is used for operating the piston (11) of the piston feeder.

2. A method as set forth in claim 1, c h a r a c t e r i ¬ z e in that the kinetic energy of said compression piston (52) is transmitted from the compression piston by way of energy transmitting elements (66, 72, 56) to driving equipment for the piston (11).

3. A method as set forth in claim 2, c h a r a c t e r i ¬ z e d in that the compression piston (52) is returned during the intervals between subsequent material feeding cycles.

4. An apparatus for feeding material into a pressurized space (1), said apparatus comprising a piston feeder (8, 10, 11) which includes a cylinder space (12), wherefrom the material is transferable by means of a feeding piston (11) of said piston feeder into the pressurized space (1), which pressurized space (1) has connected there with a compression cylinder (50), provided with a compression 11

piston (52) which is in communication with the pressurized space (1), c h a r a c t e r i s e d in that the compression piston (52) is by way of energy transmitting elements, which include a hydraulic cylinder (66), a valve mechanism (72) and a hydraulic piping (56), in communication with the feeding piston (11), which is operable by the action of a force acting on the compression piston (52) by said pressurized space (1).

5. An apparatus as set forth in claim 4, c h a r a c t e ¬ r i z e d in that alongside the hydraulic cylinder (66) is a shunt pipe (74), whereby the fluid contained in the hydraulic cylinder (66) can be supplied on the opposite sides of a hydraulic piston according to the operating sequences of the apparatus.