EP0663565A2 - Grate bar and grate with cooling device and cooling method - Google Patents

Abstract

Fluid-cooled grate bars and grates for use in a combustion furnace such as a garbage incineration plant and a process for cooling the grate bars and grates. The grate bar has a duct defined therewithin for guiding a coolant supplied by a fluid-cooling apparatus. The primary coolant is preferably water. Steam formation is prevented by pressurizing the water. Additional or replacement coolant such, for example, as air may be employed for the grate bars and grates.

Description

The invention relates to a grate bar and grate with cooling device and a method for cooling for incinerators, in particular waste incineration plants.

A grate for incinerators is usually formed by rows of grate bars that lie one above the other and extend transversely to the transport direction of the firing material.
Grate firing is also used as a tried and tested apparatus for domestic waste incineration. The individual grids are covered with grate bars. These have the task of transporting the garbage, mixing (so-called stoking) and taking over the burnout. The processes of drying, preheating, degassing, gasification and C-burnout run on the grate, and thus the grate bars, one after the other.

The grate bars are provided with openings (slots, gaps, holes, etc.) through which combustion air is blown.

The grate bars are particularly subject to mechanical abrasion as well as thermal and chemical wear. Corresponding wear leads to changes in the fire control, the burn-out qualities and ultimately to business interruptions. The wear of the grate bars is essentially temperature-dependent.

Through appropriate measures, part of the supplied combustion air - so-called primary air - is used to cool the grate bars. The cooling effect depends primarily on the amount of air. The remaining part is added as secondary air for further combustion of the gases in the combustion chamber.

Due to changes in household waste, primarily with a view to higher calorific values (recycling of glass, biological materials / green waste, increased proportion of plastics / plastics) and increased fluctuations in the area of high calorific values, the grate rod temperatures increase, partly due to more intensive combustion others, however, also due to less air under the grate (decreasing cooling effect). The high calorific value causes a redistribution of the entire combustion air in such a way that a higher proportion is required in the combustion chamber for the combustion of the gases.

The invention is based on the problem of creating grate bars and a grate which are wear-resistant when burning high-calorific materials, do not change their shape and thus do not change the combustion behavior and the transport and mixing behavior in the furnace. In addition, good emergency running properties in the event of water failure and a relatively low heating of the water to less than 100 degrees Celsius, preferably to less than 50 degrees Celsius, are to be achieved. In addition, steam formation is to be effectively prevented.

According to the invention the problem is solved by claims 1, 7 and 12. Advantageous developments of the invention are specified in the subclaims.

The grate bar according to the invention with a cooling device, on which at least one inlet and one outlet opening is arranged, has at least one channel in the grate bar for guiding cooling water, essentially in the longitudinal direction of the Rust bar, on. Since the longitudinal direction of the grate bar corresponds to the material feed device, particularly good cooling of the individual grate bars is thereby achieved. By cooling each individual grate bar, the heating of the cooling medium can be kept relatively low. This increases the operational reliability of the cooling and the service life of the grates or cooling system. Water is preferably used as the cooling medium. Other, higher-boiling cooling media can also be used for special applications.

The channel arranged in the grate bar preferably has two, essentially parallel sections with opposite flow directions, these being connected to a deflection arranged in the head region of the grate bar. The sections of the channel with the opposite flow direction can lie side by side or one above the other in the horizontal or vertical plane. The channels are optimized in terms of flow technology with regard to the heat to be removed, so that the heating of the cooling liquid is not more than about 50 degrees Celsius, preferably about 20 degrees Celsius. In particular in the case of sections of the cooling channel lying approximately one above the other, these can have different cross-sectional shapes and areas. The deflection arranged in the head region of the grate bar can lie in the plane that passes through the central axes of the approximately parallel sections of the cooling channel.

The deflection is preferably guided into the area of the edge of the grate bar head resting on an adjacent row of grate bars. It is approximately U-shaped in the area of the grate bar head.

In a special version there are inlet and outlet openings for the coolant at the base of the grate bar in the area of the arranged for the coolant at the base of the grate bar in the area of the grate bar support.
Air outlet openings for combustion air are further preferably arranged in the head part. This further improves the cooling of the grate bar. According to a special design, recesses for the exit of combustion air are also arranged in the long sides of the grate bar.

In a further special case, a closed, overpressure-operated cooling device is arranged on the grate, which advantageously prevents the formation of steam within the cooling circuit and thus also within individual grate bars or grates. This cooling system advantageously consists of an expansion or compensation vessel (32), the cooled grate bars (34), a recooler (35) as well as a pump (36) and a connection (31) for filling or emptying the cooling system together with a pressure control valve (33 ).

When using water, the cooling medium is operated in a cooling system under excess pressure, preferably between 1 and 6 bar. This avoids the formation of steam and e.g. prevents a two-phase flow or formation of "steam cushions" with correspondingly poor heat transfer.

The grate according to the invention for incinerators, in particular waste incineration plants, with adjacent rows of alternately fixed and movable grate bar rows, which are composed of the grate bars described above, is characterized in that the inlet and outlet openings of all grate bars are connected in parallel with a main inlet line and a main outlet line. This makes the same for all grate bars Cooling effect achieved. For each grate bar there is essentially the same temperature distribution (assuming the same heat load), so that each grate bar also has approximately the same temperature-related expansion.

For individual applications, however, a plurality of grate bars lying side by side in the direction of the grate width can also be connected to one another in series, so that, for example, an adapted cooling effect of the grate bars is achieved in adaptation to the different heat loads in the center and edge regions of the grate. In a special version with fourteen grate bars lying next to each other, for example, the first, sixth and eleventh grate bars are connected to the main feed line with their inlet opening. The fifth, tenth and fourteenth grate bars are connected to the main drain line with their drain opening. The remaining drainage or inlet openings of adjacent grate bars are interconnected. In particular, it is provided to cool both the fixed rows of grate bars and the moving rows of grate bars.

According to a particularly preferred feature of the invention, valves are located between the main inlet and main outlet opening and the inlet and outlet opening of the first or last grate bar of a row of grate bars or a portion of a row of grate bars in which the inlet and outlet openings of the individual grate bars are connected to one another arranged for supplying or removing a further cooling medium, in particular air, and for interrupting the main inlet or outlet line. This has the advantage that, in the event of a leak in one or more grate bars in a row of grate bars, air cooling is used instead of water cooling, and thus operation is planned until the next Downtime can be maintained. In addition, thermally lightly loaded grate bar rows with cheaper cooling media, such as. B. air, are cooled. The combination of several rows of grate bars in parallel connection to grate zones with a common inlet and outlet line and valves for the inlet and outlet of a further cooling medium, in particular air, and a shut-off to the main inlet and outlet line reveals a particularly economical variant.

The design of the grate bar according to the invention is described using an exemplary embodiment.

Figur 1

eine Seitenansicht der Roststablängsseite;

Figur 2

einen Schnitt II nach Figur 1, für eine Umlenkung, die bis in den Bereich der auf einer benachbarten Roststabreihe aufliegenden Kante des Roststabes geführt ist;

Figur 3

einen Schnitt II nach Figur 1, für eine Ausführung der Umlenkung, bei der die Umlenkung etwa in der Mittelebene der parallelen Abschnitte des Kühlkanals liegt;

Figur 4

ein Fließschema eines Rostes, bei dem Ventile zur Zu- und Abfuhr eines weiteren Kühlmediums
angeordnet sind.

Figur 5

zeigt ein Schema des Kühlsystems, mit dem die Roststäbe bzw. der Rost gekühlt werden.

Show it:

Figure 1

a side view of the grate bar side;

Figure 2

a section II of Figure 1, for a deflection, which is performed in the area of the resting on an adjacent row of grate bar edge of the grate bar;

Figure 3

a section II of Figure 1, for an embodiment of the deflection, in which the deflection lies approximately in the central plane of the parallel sections of the cooling channel;

Figure 4

a flow diagram of a grate, in the valves for the supply and removal of another cooling medium
are arranged.

Figure 5

shows a schematic of the cooling system with which the grate bars or the grate are cooled.

1 shows a grate bar 1 with grate bar support 2 in the area of the grate bar foot 3. The grate bar head 4 lies with the edge 5 on a grate bar one adjacent row of grate bars. The grate bar is made of cast iron. It has a channel 6 which has approximately parallel sections (one behind the other in FIG. 1). These parallel sections are connected to one another by a deflection 7. The channel 6 is provided with drainage openings 8. These inlet and outlet openings are preferably attached directly to the foot end of the channel 6.

FIG. 2 shows a section II according to FIG. 1 through the grate bar head 4. The approximately parallel sections of the channel 6, here referred to as 6 'and 6' ', open into a deflection 7, which is approximately U-shaped in the plane of the section II and is guided into the lower edge 5 of the grate bar head 4. Air outlet openings 9 are provided in the grate bar head 4 between and next to the legs of the U-shaped deflection 7.

FIG. 3 shows a section II according to FIG. 1 for an embodiment in which the deflection is not drawn into the area of the edge 5. The deflection 7 forms here together with the channel sections 6 'and 6' 'in their plane also an approximately U-shaped cross section. Correspondingly, the sections 6 'and 6' 'can also be arranged one above the other.

A flow diagram of a grate is shown in FIG.

Valves are located between the main inlet 10 and the main outlet line 11 of a cooling medium, in particular water, and the inlet 12 and outlet opening 13 of the first 14 and last 15 grate bars of each grate bar row, the inlet and outlet openings of the individual grate bars being connected to one another in series arranged for the supply 16 or discharge 17 of a further cooling medium, in particular air, and for interrupting the main inlet 18 or the main outlet line 19. The feed of the second Cooling medium takes place via the main feed line 20 or main discharge line 21. The arrow 22 indicates a preferred direction of waste flow.

The grate and the grate bar according to the invention have the advantage that the grate bars can be used without further modification of the incinerator. It therefore remains with the previous combustion technology. The mechanical transport and mixing behavior (forward / return stroke) also remain unchanged. This applies to both the weight and the stroke length and so on. The grate is also extremely wear-resistant, as the grate bars are made of cast iron as before. The grate bar and grate according to the invention therefore also have excellent emergency running properties in the event of malfunctions, for example in the event of water failure. The grate bars preferably have the shape known hitherto, the width of the grate bars being approximately doubled, so that in one half, that is to say the usual grate bar width, the cooling water is conducted forward to the head and returned in the second half becomes. The parallel channel sections have a clear height of approximately 15 to 25 mm and a clear width of approximately 40 to 60 mm. The flow rate is between 0.5 and 2 m per second. The temperature of the grate bar is approximately 100 degrees Celsius in the middle between the head and foot area. This prevents corrosion due to condensation. A temperature of about 150 degrees Celsius is maintained in the area of the head part, so that there is no disadvantage with regard to the burnout behavior.

In a special exemplary embodiment, the grate bars or the grates are integrated and operated in a closed, water-cooled cooling system which is under pressure. The temperature of the water is, for example, 90 ° C, but this can be increased to 120 ° C, and the system pressure is 1 to 6 bar. preferably 5 bar.

Here, the cooling system pressure is set by means of a compressor which conveys air into the outer space of an expansion vessel or compensation vessel, which is separated from the water side by a bladder. The system pressure in the cooling water circuit is set via an expansion automat integrated in the expansion vessel: A contact manometer starts the compressor of the expansion automat as soon as a lower limit pressure is reached in the system. The compressor is switched off as soon as the pressure reaches an upper limit. If an adjustable upper limit pressure value is exceeded, e.g. 6 bar, air is blown off via a valve. The two switching points can be set between 1.0 and 6.0 bar. The separation of air, which is located inside the expandable bladder, preferably a rubber bladder, of the expansion vessel, and water, which is located outside the bladder, advantageously prevents the cooling water from absorbing oxygen and thus promoting corrosion on the grate bars.

FIG. 5 shows the diagram of a cooling device. Water is fed into the cooling device through the connection 31, the pressure control valve 33 protecting the system against pressures at the grate inlet above 2 bar. The pump 36 conveys the water through one or more grate bars or grate 34 and the cooling device. The expansion or compensation vessel 32 is provided with a level measuring device, with the aid of which fresh water is automatically fed into the system when the temperature falls below a lower limit and at the same time a message is sent to the control room. At the When the water reaches an upper limit, the water supply is automatically interrupted. Due to the frequency of reporting to the control room via the water feed, leaks in the system can be identified, so that appropriate measures can be initiated. Each grate bar or row of grate bars can be locked separately. In addition, a water mass flow measuring device 37, a temperature measuring device 38, 39 and a cooling system pressure measuring device 40 are provided as measuring devices. The fan 41 cools the recooler 35.

Reference symbol list:

31:

Water supply

32:

Expansion vessel

33:

Pressure control valve

34:

Rust, chilled

35:

Recooler

36:

pump

37:

Water mass flow measuring device

38:

Temperature measuring device

39:

Temperature measuring device

40:

System pressure measuring device

41:

fan

Claims (13)

Grate bar with cooling device, an inlet and an outlet opening being arranged in the grate bar, characterized in that
in the grate bar (1) at least one channel (6) for guiding cooling water runs essentially in the longitudinal direction of the grate bar (1). Grate bar according to claim 1, characterized in that the channel 2 has essentially parallel sections (6 ', 6' ') with opposite flow directions, these being connected to a deflection (7) provided in the head region (4) of the grate bar. Grate bar according to claim 2, characterized in that the deflection (7) is guided into the area of the edge (5) of the grate bar head (4) resting on an adjacent row of grate bars, in particular in the area of the grate bar head (4) is approximately U-shaped. Grate bar according to claim 3, characterized in that inlet and outlet openings (8) are arranged at the foot (3) of the grate bar (1) in the region of the grate bar support (2). Grate bar according to one of claims 1 to 4, characterized in that
Air outlet openings (9) are arranged in the head part (4). Grate bar according to one of claims 1 to 5, characterized in that
In the long sides of the grate bar (1) there are recesses for air outlet. Grate for incinerators, in particular waste incineration plants, with adjacent rows of alternately fixed and movable grate bar rows made of grate bars of claims 1 to 6, characterized in that
Inlet and outlet openings (8) of all grate bars are connected in parallel with a main inlet or a main outlet line. Grate for incinerators, in particular waste incineration plants, with adjacent rows of alternately fixed and movable rows of grate bars made of grate bars of claims 1 to 6, characterized in that
Inlet and outlet openings (8) of several adjacent grate bars are connected to one another in series. Grate for incinerators, in particular waste incineration plants, with adjacent rows of alternately fixed and movable grate bar rows made of grate bars of claims 1 to 6, characterized in that a closed, overpressure-operated cooling device is arranged on the grate, in particular with a compressor and an expansion vessel. Grate for incinerators, in particular waste incineration plants, with rows of grate bars of grate bars of claims 1 to 6 lying next to one another, characterized in that
between the main inlet (10) and main outlet line (11) and inlet (12) and outlet opening (13) of the first (14) or last grate bar (15) of a grate bar row, in which the inlet and outlet openings of the individual grate bars are connected in series, valves for supplying (16) or discharging (17) another cooling medium, in particular air, and for interrupting the main inlet (18) or main outlet line (19) are arranged. Grate for incinerators, in particular waste incineration plants, with rows of grate bars made of grate bars lying side by side according to claim 10, characterized in that
several rows of grate bars are connected to each other in parallel to grate zones and have a common inlet and outlet line in which valves for the inlet and outlet of a further cooling medium, preferably air, are arranged. Process for the direct cooling of grate bars and grates of incinerators, in particular waste incineration plants, characterized in that the cooling medium flowing through the grate bar or the grate is guided in a cooling system under excess pressure. A method according to claim 12, characterized in that the overpressure of the cooling device is adjustable by means of an expansion vessel coupled to a compressor.

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