An ash-disposal system with submerged scraper

Abstract

 Apparatus for handling ash and slag produced in the combustion of coal or other ash-bearing fuel in the furnace (10) of a steam generator, including an ash hopper (14) beneath the furnace into which the ash initially falls. A pair of scraper conveyors (30,32) which are submerged in water are located below the ash hopper (14) from which the ash is continuously disposed of. Water nozzles (40) are located in the ash hopper (14) for cooling and moving the ash.

Description

[0001] The invention relates to an ash-disposal system for ashes discharged from a coal-fired or other ash-bearing fuel-fired combustion chamber.

[0002] In coal-fired steam generators, the manner in which the ash is handled and disposed of is an item of considerable importance. The equipment for handling the.ash cannot only be costly, but if it requires much maintenance, it can also lead to untimely and lengthy shut-downs of the entire steam generator.

[0003] The invention as claimed is intended to provide a remedy by providing an ash-handling or ash-disposal system for the furnaces of steam generators, including an ash hopper beneath the furnace into which the ash and slag initially falls. A pair of scraper conveyors which are submerged in water are located below the ash hopper from which the ash is continuously disposed of. Water nozzles are located in the ash hopper for cooling and moving the ash.

[0004] One way of carrying out the invention is described in detail below with reference to drawings which illustrate only one specific embodiment in which:

Figure 1 is a cross-sectional side view of the ash handling apparatus for the furnace of a steam generator; and

Figure 2 is a view taken on line 2-2 of Figure 1.

[0005] Referring to Figure 1, numeral 10 denotes the furnace bottom opening of a coal-fired steam generator, through which molten ash and slag are discharged. A water seal 12 permits thermal expansion of the top-supported furnace, while preventing exposure of the interior of ash hopper 14 to the atmosphere.

[0006] Ash falls into the ash hopper (Figure 2), sliding down the angled floor to one of-the openings 18,20. These openings can be closed by gates 22,-24 when necessary, as later described. This hopper may or may not be refractory-lined and may or may not be water-cooled.

[0007] The ash falls through the openings 18, 20 into one or the other of the longitudinal tanks 26, 28. Each tank contains a scraper conveyor 30, 32, the upper runs of which are'submerged, or located beneath the water level maintained in each tank. The upper runs of the conveyors carry the clinkers to the end of the tanks, where they can be discharged into trucks or onto mechanical conveyors (not shown) and transported away. A portion of the water in the tanks is constantly removed and replenished to maintain the main body of water at a temperature not exceeding 160°F (71°C).

[0008] In normal operation, the conveyors are in constant operation, continuously removing ash. When one of the conveyors need repair, its corresponding gate valve, for example 22, can be closed, so all of the ash is then discharged through opening 20 into tank 28. Tank 26 can then be drained so-that the conveyor 30, or other broken equipment, can be repaired without necessitating shutdown of the steam generator.

[0009] If both conveyors need some minor repairs simultaneously, both gate valves 22 and 24 can be closed. Water from the nozzles 40 can then be used.to fill the ash hopper 14 to a given level, and the ash can be temporarily stored in the ash hopper for a short time while minor repair or maintenance work is done to the conveyors. An overflow pipe 42 keeps the water at a constant level during this type of operation.

[0010] The water nozzles 40 provide an additional function. During normal operation, they direct jets or sprays of water onto the falling ash, thus providing hydraulic fracturing and sluicing of large ash particles, preventing the openings 18 and 20 from becoming clogged. Alternatively, the gates can be kept closed, and the ash hopper normally filled with water. The gates could then be intermittently opened to allow discharge of the ash.

[0011] From the above, it can be seen that in normal operation, the ash is continuously removed by both of the scraper conveyors. Falling ash from furnace 10 strikes surface 16 of the ash hopper, preventing damage to the conveyors 30, 32. The drop from the ash hopper bottom to the conveyors is relatively short compared to the height of the ash hopper. When repair work is required on one of the conveyors, the ash is removed by the other one. This is accomplished without the necessity of moving the tank and conveyor and also without shutting down the steam generator. In addition, minor maintenance can be done to both of the conveyors while the ash is temporarily stored in the ash hopper 14. Certainly, the length of time of this operation is limited by the ash storage capacity of the hopper 14.

Claims

1. An ash-disposal system for ashes discharged from a coal-fired or other ash-bearing fuel-fired combustion chamber (10), including an ash hopper (14) positioned beneath the combustion chamber (10) into which the ash falls, spray nozzles (40) for directing water jets onto the falling ash, a pair of openings (18,20) in opposite walls of the ash hopper (14) adjacent to the bottom thereof, a pair of tanks (26,28) located beneath the ash hopper (14), each being beneath the respective ash hopper openings (18,20), means for maintaining a given level of water in each tank (26,28), and conveyor means (30,32) located in each tank beneath the water level for removing ash from the tanks (26,28).

2. The ash-disposal system of Claim 1, including a pair of gate valves (22,24) associated with the ash-hopper openings (18,2₀).

3. The ash-disposal system of Claim 2, including means for maintaining a given water level in the ash hopper (14) when both gate valves (22,24) are in their closed positions.

4. The ash-disposal system set forth in Claim 3, including water seal means (12) between the combustion chamber (10) and the ash hopper (14), and between the ash hopper (14) and the tanks (26,28), so that the dry ash fines cannot escape to the atmosphere, and atmospheric air cannot enter the combustion chamber (10).

Drawing