DE20005259U1 - Device for retrofitting wet ash systems to incinerators for dewatering wet ash - Google Patents

Description

The invention relates to a device for retrofitting wet ash removal systems to incineration plants for dewatering the wet ash after it has been conveyed away by means of a conveyor means continuously rotating in a trough supplied with coolant, e.g. a scraper belt rotating in water, into a discharge chute provided with a vibrating pusher screen.

In a steam generator in which, for example, coal dust is burned to generate steam, ash and slag accumulate at the outlet of the combustion chamber hopper, which must be removed. For this purpose, continuously operating extraction devices are provided under the outlet of the combustion chamber hopper. In wet ash removal, the ash and slag lumps fall into a trough filled with water, in which a scraper belt is provided for removing the wet ash and slag. The water in the trough extinguishes the hot ash on the one hand and also breaks up the even larger slag lumps on the other.

Conveyor systems for removing the wet ash are arranged downstream of the scraper belt. For this purpose, it is known to feed the wet ash to a discharge chute using the scraper belt, which ends above a conveyor belt, which feeds the wet ash to a silo, if necessary via further downstream conveyor belts. The wet ash is temporarily stored in this silo. The wet ash can also be loaded into containers that are then dumped in appropriate landfills.

Any slag chunks that may arise from the steam generator are caught by a vibrating screen arranged in the discharge chute. The fine wet ash falls through the vibrating screen onto the conveyor belt, the slag chunks are held back and fed through the vibrating screen, which is slightly inclined in one direction, to a crusher arranged to the side of the vibrating screen.

Such a vibrating-push screen with crusher is known, for example, from the published patent application DE 195 04 589. In this case, a vibrating-push screen is installed upstream of the crusher for crushing cooled material from a grate cooler in order to be able to operate the grate cooler with a high throughput in a reliable manner and with as little clogging as possible.
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During the entire removal of wet ash, it has proven to be very disadvantageous if the wet ash has too high a water content, i.e. the

Wet ash does not release the required amount of water on its way to being discharged into the discharge chute. Wet ash with too high a water content causes the conveyors downstream of the scraper belt to become so heavily contaminated that the conveyors can no longer operate properly, which can also lead to the conveyors failing. Wet ash discharged from one conveyor belt onto a subsequent conveyor belt forms puddles of water on the surface of the wet ash being transported, and this water runs down at certain points along the transport path and, for example, contaminates the conveyor belt rollers. These are therefore subject to greater wear.

There are also massive problems with the temporary storage of this wet ash with a high water content in silos. After a certain time, it is no longer possible to remove the wet ash because the wet ash has solidified to such an extent that it is very difficult to empty the silos.

A method for dewatering ash is known from DE 198 30 943 A1, in which the ash produced during combustion in a coal dust furnace is cooled in a water-cooled wet ash collector after being discharged from the coal dust furnace. To dewater the wet ash, it is fed into a vibrating dewaterer after being discharged from the wet ash collector, where it is freed from the adhering water and transferred to a state that is suitable for transport and further processing. The vibrating dewaterer has a driven, vibrating sieve box with a sieve bottom, with the feed device for the wet ash on one side of the sieve bottom and a discharge device for the dewatered wet ash on the opposite end. The water running through the sieve bottom is collected in a collecting tray and returned by means of a pump via cyclone devices.

In wet ash removal plants, vibrating pusher screens are arranged in the wet ash transport path for slag chunks that occasionally accrue from combustion in the discharge hopper after a scraper chain conveyor. The wet ash thrown out by the scraper chain conveyor falls through the sieve bottoms of these vibrating pusher screens onto a conveyor belt arranged under the discharge hopper. Only slag chunks are held by the sieve bottom and are fed to a lateral discharge opening due to the inclination of the sieve bottom and the pushing movement of the sieve bottom.

The slag chunks fall from this discharge opening into a slag crusher located below the discharge opening, in which the slag chunks are ground into fine pieces of ash. This eliminates the risk of the slag chunks blocking the transport path for the wet ash. The wet ash is not dewatered in the vibrating-push screen. It would not make economic sense to replace the vibrating-push screen with a vibrating dewaterer in accordance with DE 198 30 943 A1. Continuous operation of the vibrating dewaterer in accordance with DE 198 30 943 A1 is also not guaranteed when slag is generated.

The invention is therefore based on the object of further developing a vibrating feed screen arranged in the transport path of the wet ash in such a way that when the wet ash passes through the vibrating feed screen, dewatering of the wet ash and control of slag lumps are also possible.

The object is achieved according to the invention in that a sheet is arranged directly on the screen surface of the vibrating screen, which is provided with drainage openings over its entire surface,
on the sheet metal at the edge of an upstand lying in the conveying direction of the vibrating screen and

Above and essentially parallel to the sheet metal, an impact rake is arranged to protect it.

Advantageously, the drainage openings in the sheet are evenly spaced from each other. The drainage openings are designed as 1-2 mm holes or slots. The sheet is provided with a drainage guide plate that extends under the vibrating pusher screen on the underside of the edge of the screen surface that lies in the conveying direction of the vibrating pusher screen.

The invention will be explained in more detail below using an exemplary embodiment. The

Fig. 1: a schematic side view of a drainage device

of a steam generator with a vibrating screen installed in the discharge hopper

Fig. 2: a spatial representation of the screen surface of the Schwing

shear screen mounted sheet and the impact rake

In a brown coal-fired steam generator, a trough 7 filled with water is arranged in the outlet 6 of the hopper of the steam generator for the removal of the ash and slag produced during the combustion of brown coal, in which a scraper belt 8 in the water draws the ash and slag from the area where the ash and slag fall on the upper tower 9 of the scraper belt 8 and feeds it to the discharge hopper 11 via an upwardly inclined scraper belt slope 10 outside the water-filled trough 7 (Fig. 1).

In the discharge hopper 11, a vibrating-push screen 1 is arranged in the fall path of the wet ash. The bars of the vibrating-push screen are spaced far enough apart that the wet ash reaches a conveyor belt 12 located below the vibrating-push screen 1. Only larger slag chunks are caught by the vibrating-push screen 1 and, through the pushing movement of the vibrating-push screen 1 and the slight inclination of the screen surface, are fed to a side discharge of the vibrating-push screen 1, from which the slag chunks are discharged into a slag crusher 13 located below this discharge. In the slag crusher 13, the slag chunks are ground up and also fall onto the conveyor belt 12.

In order to use the vibrating-push screen 1 for dewatering the wet ash, a sheet 2 is mounted (screwed or welded) directly on the screen surface of the vibrating-push screen. This sheet 2 is provided with drainage openings 3 over the entire surface, which are designed as holes of approx. 2 mm (Fig. 2). Other borehole sizes are also conceivable. The holes are arranged in a grid pattern and are spaced approx. 20 mm apart. Any other grid spacing or another arrangement of the holes is also possible. Instead of holes, the sheet 2 can also be provided with elongated holes. The sheet 2 is also provided with an upstand 4 on the edge lying in the conveying direction of the vibrating-push screen 1.

The raised edge 4 causes a build-up of the wet ash to be dewatered when the wet ash is transported away in the direction of the slag crusher 13 in order to extend the residence time of the ash on the sheet. This has a positive effect on the dewatering of the wet ash.

An impact rake 5 is attached to four supports 14 (e.g. made of angle steel) attached to the corners of the screen surface of the vibrating screen approximately 400 mm above and essentially parallel to the sheet 2, which, like the screen bottom of the

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vibrating screen 1 and protects the sheet 2 from falling lumps of slag. The impact rake 5 essentially consists of grid bars arranged parallel to the vibrating feed direction of the vibrating screen 1 and at a distance from one another.

The slag lumps are conveyed by the impact rake 5, which, like the screening surface of the vibrating-push screen, is slightly inclined in the conveying direction of the vibrating-push screen 2, towards the slag crusher 13 and are thrown into it.

The wet ash falling onto the sheet 2 is dewatered by the shaking movement, with the water running downwards through the holes. From there it reaches a funnel 15 located beneath the vibrating screen 1 and via pipes into a corresponding dewatering system. Due to the shaking movement, the dewatered wet ash is thrown over the raised edge 4 into the slag crusher 13 and from there reaches the conveyor belt 12 for removal.

A drainage guide plate 16 is mounted on the underside of the edge of the plate 2 lying in the conveying direction of the vibrating pusher screen 1 and projects under the vibrating pusher screen 1. This ensures that the water running through the holes is not led into the slag crusher 13 due to the inclination of the plate 2 and thus returns to the conveyor belt 12 to the dewatered wet ash.

To control the proper drainage of the water accumulating during the dewatering of the wet ash at the vibrating screen 1, 15 inspection openings, e.g. lockable hatches, can be arranged in the hopper.

The device for dewatering wet ash provides a simple and cost-effective way to retrofit existing wet ash treatment plants with vibrating screens, i.e. to greatly improve the dewatering of wet ash on the installed plant.

This eliminates the need for, for example, the retrofitting of complex units (shaking devices), which are associated with high financial expenditure (installation costs, maintenance costs, susceptibility to failure, provision of additional workers).

Even if slag accumulates from the steam generator, the operation of the
Wet ash dewatering is manageable.

Reference character line

1 Vibrating screen 2 sheet 3 Drain opening 4 Upstand 5 Impact rake 6 Outlet 7 trough 8th Scratch tape 9 Upper Tower 10 Scraper belt slope 11 Discharge funnel 12 Conveyor belt 13 Slag crusher 14 support 15 funnel 16 Drain baffle

Claims (3)

1. Device for retrofitting wet ash removal systems to combustion plants for dewatering the wet ash after it has been conveyed away by means of a conveyor means circulating continuously in a trough supplied with coolant, e.g. a scraper belt circulating in water, into a discharge chute provided with a vibrating pusher screen, characterized in that
that a sheet ( 2 ) is arranged directly on the screen surface of the vibrating screen ( 1 ), which is provided with drainage openings ( 3 ) over its entire surface,
on the sheet ( 2 ) at the edge of an upstand ( 4 ) lying in the conveying direction of the vibrating screen ( 1 ) and an impact rake ( 5 ) is arranged above and substantially parallel to the sheet to protect it. 2. Device according to claim 1 or 2, characterized in that the drainage openings ( 3 ) are evenly spaced from one another, wherein the drainage openings ( 3 ) are designed as 1-2 mm large bores or elongated holes. 3. Devices according to claim 1 or 2, characterized in that the sheet ( 2 ) is provided on the underside of the edge lying in the conveying direction of the vibrating pusher screen ( 1 ) with a discharge guide plate ( 16 ) projecting below the vibrating pusher screen ( 1 ).