TRANSFER CHAMBERS FOR THE CONVEYOR IN A PNEUMATIC TRANSPORT SYSTEM

Abstract: A pneumatic transport system for transferring particulate material from a first pressurized container to a second container which is under a lower pressure while successively reducing the pressure, comprising a number of parallel tubes (36), arranged in series, said tubes being joined together at their ends by means of transfer chambers (38) for transferring a gas/material stream from an upstream tube (36) to a downstream tube (36). The tubes (36) are joined to the transfer chambers (38) by hexagonal flanges (58, 60). This design of the flange makes possible a compact construction of a discharge device which may be used as a cooler for the transported material.

Description: Transfer chambers for the conveyor in a pneumatic transport system TECHNICAL FIELD The invention relates to a pneumatic transport system for transferring particulate material from a first pressurized container to a second container which is under a lower pressure, while successively reducing the pressure. It is built up of a number of parallel tubes, arranged in series, which at their ends are joined to transfer chambers for the gas/material flow from an upstream tube to a downstream tube. Transport systems of this kind may advantageously be used for discharging dust (ashes) from gas cleaners in a PFBC power plant or bed material from a combustor in such a plant. PFBC are the initial letters of the English expression Pressurized Fluidized Bed (Combustion. BACKGROUND ART A transport device of the above kind for successive reduc¬ tion of the pressure by repeatedly changing a gas/particle stream is disclosed in European Patent 0 108 505 applied to a PFBC power plant. In this a combustor and a cleaner for combustion gases are enclosed within a pressure vessel and surrounded by compressed combustion air. The operating pressure in the plant may amount to about 20 bar. The material to be fed out from a gas cleaner or a combus ¬ tor is often abrasive and has a high temperature, up to about 900°C. Since the transport device is able to work continuously and without valves, as in the lock hopper sys¬ tem, it is most suitable for feeding out dust/ashes from gas cleaners. SUMMARY OF THE INVENTION The object of the invention is to provide a compact trans ¬ port device of such a design that it becomes an effective cooler. According to the invention the transfer chambers are formed with tubular inlets and outlets with hexagonal flanges for connection to parallel tubes in the transport device. Con ¬ veniently, the transfer chambers are cast in a heat-resis ¬ tant and abrasion-resistant alloy and the flanges are joined together at one of the sides so as to obtain a con ¬ tinuous flange with ten of the two sides of the hexagonal flanges. By the hexagonal embodiment of the flanges, the transport device can be formed, in a simple manner, as an effective cooler. The hexagonal shape makes it possible to obtain in a simple manner, at the transition of a horizontal tube layer to the subsequent tube layer, a displacement of the tubes by half a tube pitch and a small vertical distance between two tube layers. BRIEF DESCRIPTION OF THE DRAWING The invention will be described in greater detail with ref ¬ erence to the accompanying drawing, wherein Figure 1 shows a PFBC power plant in which the invention is utilized as a pressure-reducing discharge device and cooler of ashes separated in a gas cleaner, Figure 2 shows a diagram of such an ash discharge device and cooler comprising 30 tube parts and 29 transfer cham ¬ bers connecting the tube parts, Figure 3 shows a side view of an ash discharge device/ cooler, Figure 4 shows a section through this along A-A in Figure 3, Figure 5 shows a longitudinal section through a transfer chamber according to C-C in Figure 6, Figure 6 shows a section through a transfer chamber accor ¬ ding to B-B in Figure 5, and Figure 7 shows an end view of a transfer chamber accor ¬ ding to D-D in Figure 5. DESCRIPTION OF THE PREFERRED EMBODIMENT In the figures, 10 designates a pressure vessel which sur ¬ rounds a combustor 12 and a gas cleaning plant 14 which is symbolized by a cyclone. In the gas cleaning plant 14, dust from combustion gases are separated from the combus ¬ tor 12 before being supplied to a gas turbine (not shown) via the conduit 16. The gas turbine drives a compressor which, via the conduit 18, feeds the space 20 between the combustor 12, the cleaning plant 14 and the pressure vessel 10 with compressed combustion air. The combustion is per ¬ formed in a bed 22 of particulate material in the combustor 12. Fuel is supplied to the combustor 12 in the lower part of the bed 22 via the conduit 24 and nozzles (not shown). The combustor 12 is supplied with compressed air from the space 20 for fluidization of the bed 22 and combustion of supplied fuel via the duct 26 and the bottom 28 with air nozzles 30. The combustor 12 includes tubes 32 for cooling of the bed 22 and generation of steam for a steam turbine. Dust separated in the gas cleaner 14 and consisting of ashes and residues of bed material is fed out via the con¬ duit 25 and a pressure-reducing pneumatic discharge device 34, formed as a cooler and placed in the duct 26. The device 34 is composed of a number of tubes 36 and transfer chambers 38 connecting an upstream tube 36 to a subsequent downstream tube 36. The dust is forwarded in the conduit 40 to a collecting container 42 with a filter 44 for cleaning the transport gas. Figure 2 shows a diagram of a discharge device with 30 parallel tubes 36 connected together by means of 29 trans- fer chambers 38, an inlet tube 46 and an outlet tube 48. The conduit 46 is connected to the conduit 25 from .the cleaning plant 14 and the outlet conduit 48 is connected to the conduit 40 in the container 42. The numbers 1-30 in the tubes 36 in Figure 2 and Figure 4 denote the ordinal numbers of the tubes 36 forming part of the discharge device 34. As is shown in Figure 3 and Figure 4, the tubes 36 and the transfer chambers 38 in the discharge device 34 used as a cooler are arranged in six layers in a frame 50 with the tubes 36 in contiguous layers being displaced in lateral direction by a distance corresponding to half the distance between two tubes 36. In this way the best cooling of a cooling gas stream passing through the discharge device 34 is obtained. As is shown in Figure 5 and Figure 6, the transfer chambers are formed with a tubular inlet 52, a space 54, a tubular outlet 56 and a flange 58. The flange 58 is composed of two parts 58a and 58b of hexagonal shape joined to each other at one of the sides. The transfer chambers 38 are manufactured by casting of a wear-resistant alloy. The tubes 36 are provided at their ends with flanges 60, suita ¬ bly also of hexagonal shape. Also the tubes 46 and 48 are provided with suitably hexagonal flanges 62 and 64, res ¬ pectively, for connection to the first and last tubes, 36 (1) and 36 (30), respectively. The tubes 36 and the transfer chambers 38 are joined together by means of these flanges 58, 60 and bolted joints. The shape of the flanges with two hexagonal parts is exceedingly advantageous. As can be seen from Figure 4, the tubes 36 and the transfer chambers 38 may be placed in a simple manner in several layers with a small distance between the layers of the tubes 36. The flanges of an upper layer rest on the flanges of an underlying layer. By turning a transfer chamber 30° or 60 , a change from a lower layer to an upper layer in the discharge device 32 can be made in a simple manner, and a displacement of the tubes in the various layers by half a tube pitch, which is desirable in view of cooling, is automatically obtained. In the embo ¬ diment shown in Figure 3 and Figure 4, the change is per ¬ formed between the first and last tube layers in that transfer chamber which at the righthand end of the dis- charge device connects tubes Nos. 5 and 6. See Figures 2 and 4. The change between the second and third layers takes place in that transfer chamber which at the left- hand end of the discharge device connects tubes Nos. 10 and 11 , and so on.

Claims: CLAIMS 1. A pneumatic transport system for transferring parti ¬ culate material from a first pressurized container (14) to a second container (42) which is under a lower pressure while successively reducing the pressure, for example for discharging ashes or bed material in a PFBC power plant, comprising a number of parallel tubes (36), arranged in series, and transfer chambers (38) connected at the ends of the tubes (36) for transferring a gas/material stream from an upstream tube (36) to a downstream tube (36), c h a r a c t e r i z e d in that the transfer chambers (38) have tubular inlets and outlets (52, 56) and that these tubular inlets and outlets (52, 56) and/or the tubes (36) are formed with hexagonal flanges (58a, 58b) for connecting together the transfer chambers (38) and the tubes (36). 2. A transport system according to claim 1, c h a a c ¬ t e r i z e d in that the flanges (58a,. 58b) are joined to each other at one side so as to form a continuous flange (58). 3= A transport system according to any of claim 1 or 2, c h a r a c t e r i z e d in that the tubes (36) and the transfer chambers (38) are arranged in several layers with the tubes (36) and the transfer chambers (38) in the various layers displaced in the lateral direction with respect to each other. 4. A transport system according to claim 3, c h a r a c ¬ t e r i z e d in that the tubes (36) are horizontal and that the connection between tubes (38) and transfer cham ¬ bers (38) in the various layers are positioned in common vertical planes.

Inventors: BRAENNSTROEM ROINE, BRAENNSTROEM, ROINE
Applicants: ABB STAL AB
Application year: 1990
Main classification: F23C11
IPC codes: B65G53, F23C10, F23J1, F23J3