RU182263U1 - SOLID FUEL BOILER - Google Patents

Abstract

The proposed utility model relates to a power system, and relates to the furnace of a solid fuel boiler, which operates primarily on biofuel in the form of wood chips and wood pellets. The solid-fuel boiler furnace contains a movable grate with grill grates, a combustion chamber with multilayer walls made sequentially from the inside from a heavy lining with a high heat transfer coefficient, a lightweight lining with a low heat transfer coefficient, an air channel, and thermal insulation. Additionally, the device contains a water-cooled frame made around the perimeter of the grate of a metal rectangular pipe filled with water. In this case, the multilayer walls of the combustion chamber are mounted on a water-cooled frame. The technical result of using the utility model is to simplify the design and reduce the weight of the furnace of a solid fuel boiler. 2 of FIG.

Description

The proposed utility model relates to a power system and relates to the furnace of a solid fuel boiler, which operates primarily on biofuel in the form of wood chips and wood pellets.

The most commonly used solution for the efficient burning of wood chips with a moisture content of up to 50% is the use of a movable grate with grating. In this case, the constant movement of fuel, its drying, high-quality combustion, ash removal and the fight against the formation of slags is ensured. The cooling of the grate is carried out due to the removal of heat by the primary air passing through the grooves between the grate. At the same time, for boilers with a capacity of more than 200 kW, additional cooling of the grate becomes relevant, for example, with the help of water-cooled grate. The design of the grate is significantly complicated.

A feature of wood burning in the form of wood chips or pellets is a two-stage process - the so-called pyrolysis. At the first stage, wood is heated and burned, with primary air supply and with the release of volatile gases up to 85% by weight, and up to 70% by calorific value. At the second stage - the combustion of volatile gases with the supply of secondary air. Volatile gases also include resins in the vapor state. When the temperature in the combustion chamber drops below 700 ° C, the latter do not burn, but settle on the walls of the combustion chamber and heat exchanger. In order to prevent the deposition of tar and soot on the walls of the combustion chamber, it is necessary to ensure, under any conditions, the temperature in the combustion chamber in the range of 800-1200 ° C. To do this, the boiler’s combustion chamber must have hot insulated walls, the result is the so-called adiabatic boiler. In a modern adiabatic boiler, optimized for burning wood, the efficiency is more than 92%.

For boilers more than a megawatt of power, hot walls are not so relevant, since the volume of the combustion chamber grows in a cube relative to linear dimensions, and the heat transfer surface is only squared. The absolute size of the boiler is also affected, and quite efficiently, with tube efficiency of 85%, water-tube coal boilers can be used.

A classic solution for the walls of an adiabatic boiler with a capacity of less than a megawatt is the use of chamotte, which is characterized by fire resistance and a relatively low heat transfer coefficient.

For example, an adiabatic solid fuel boiler with a movable step grate, which moves the fuel to the ash removal point, is known (DE 19851085, class F23H 7/08, published May 11, 2000). The cooling of the grate is carried out due to the removal of heat by the primary air passing through the grooves between the grate. Additional water cooling grate is not used. The walls of the boiler furnace contain refractory - fireclay and air gap.

The disadvantages of this device include the large weight and not optimal thermal regime of the combustion chamber. Fireclay is not a fully insulating material, its thermal conductivity is 3-4 times higher than that of lightweight materials, and its weight is 2-3 times more. Satisfactory thermal insulation in this boiler can only be achieved due to the high weight of the refractory. The temperature distribution of the walls in the combustion chamber is uneven and depends on the local intensity of heat generation in the immediate vicinity of the wall.

A more effective solution is to use multilayer walls in the combustion chamber, consisting of two or more thermally insulated layers. For example, the Turbomat boiler furnace from Froling, Austria is known: https://www.froeling.com/fileadmin/content/produkte/Prospekte_Flyer/RU/RU_Prospekt_Turbomat.pdf. The boiler furnace contains a movable grate, multilayer walls, consistently consisting of chamotte, thermal insulation, air duct, and external thermal insulation from the inside. Additionally, the furnace contains water cooling of the high-temperature section of the fuel loading zone in the immediate vicinity of the grate.

The disadvantage of using chamotte as the inner layer of the combustion chamber of this boiler is the uneven heating of the walls, since low heat transfer occurs both in the depth of the walls and along the surface. For example, in the zone of intense combustion, the surface temperature of the walls of the combustion chamber will be 1200 ° C, and nearby in the zone of wood heating may be 300 ° C.

The modern solution is to use multilayer walls with a different composition of layers in the combustion chamber. The inner layer is a refractory material with a high heat transfer coefficient. For example, silicon carbite has a heat transfer coefficient higher than that of steel. The second layer is a lightweight refractory with a low heat transfer coefficient. The third layer is the air channel for heating primary and secondary air, and heat removal from the refractory. The outer layer is a heat-insulating material. The use of a refractory with a high heat transfer coefficient as an inner layer evens the temperature of the walls of the combustion chamber along the length and maintains it in the range of 800-1200 ° С.

The closest in technical essence and the achieved technical result to the proposed utility model is the boiler furnace ETA HACK 333-350 kW, company ETA, Austria, https://www.eta.co.at/index.php?id=151&download=64240a23bfd8d805b40fclelb_a5b5е42, adopted for the closest analogue (prototype).

The solid-fuel boiler furnace according to the prototype contains a movable step-grate grate with repulsive grates, a combustion chamber having multilayer walls, consisting successively from the inside of a heavy lining with a high heat transfer coefficient, a lightweight lining with a low heat transfer coefficient, an air channel, and thermal insulation. Uniform heating of the walls of the combustion chamber eliminates local local deposition of unburned resins and soot on the walls of the furnace under any boiler operating conditions. Water-cooled walls are made for additional cooling of the grate near the grate. The prototype device provides a more complete combustion of fuel, reducing the required volume of secondary air and increasing the efficiency of the boiler.

However, the prototype is not without flaws. The water cooling system of the walls of the grate is a separate, additional device, which complicates the design of the furnace and increases its weight.

The objective of the proposed utility model is the improvement of the design of the furnace of a solid fuel boiler.

The technical result of using the utility model is to simplify the design and reduce the weight of the furnace of a solid fuel boiler.

The task is achieved in that the furnace of a solid fuel boiler containing a movable grate with grill grates, a combustion chamber with multilayer walls made sequentially from the inside from a heavy lining with a high heat transfer coefficient, a lightweight lining with a low heat transfer coefficient, an air channel, and heat insulation, additionally contains water cooling a frame made around the perimeter of the grate of a rectangular metal pipe filled with water, while m multilayer walls of the combustion chamber are mounted on a water-cooled frame.

In FIG. 1 is a drawing of a furnace of a solid fuel boiler, cross section.

In FIG. 2 shows a drawing of the furnace of a solid fuel boiler, a longitudinal section.

Structurally, the combustion chamber of the solid fuel boiler of FIG. 1-2 contains:

1 - grate;

2 - a combustion chamber;

3 - heavy lining with a high heat transfer coefficient;

4 - lightweight lining with a low coefficient of heat transfer;

5 - air channel;

6 - thermal insulation;

7 - water-cooled frame;

8 - nozzles for supplying secondary air;

9 - drive mobile grates;

10 - multilayer screen;

11 - thermal insulation layer.

Grate 1 is made with repulsive moving grate.

The combustion chamber 2 is made with multilayer walls, consisting sequentially from the inside: of a heavy lining with a high heat transfer coefficient 3, a lightweight lining with a low heat transfer coefficient 4, an air channel 5, thermal insulation 6.

The combustion chamber 2 is mounted on a water-cooled frame 7, made around the perimeter of the grate 1 from a rectangular metal pipe filled with water.

Multilayer walls 3-6 of the combustion chamber 2 are installed on the water of the cooled frame 7.

The grate of the grate 1 is driven by the drive 9.

Secondary air is supplied from the air channel 5 through the secondary air nozzle 8.

To prevent overcooling of the grate between the grate 1 and the water-cooled frame 7, a multilayer screen 10 is installed.

To maintain the temperature of the multilayer walls 3-6 of the combustion chamber 2 in the operating range, a heat-insulating layer 11 is made between them and the water-cooled frame 7.

The proposed utility model works as follows.

Fuel in the form of wood chips or pellets is fed to the grate 1, where it is dried and burned. The drive 9 moves the moving grate. Fuel heats up, is constantly mixed and moves forward by means of mobile grid-irons. Heating and drying of the fuel is carried out both due to the heat of combustion of the fuel on the grate 1, and due to the radiation of heat from the heated walls of the heavy lining with a high heat transfer coefficient 3 of the combustion chamber 2. Primary air is supplied through openings in the grates. Dried fuel burns out. A large amount of volatile gases is released. Secondary air is heated in the air channel 5 and fed into the combustion chamber 2 through nozzles 8. During the combustion of volatile gases, the bulk of the heat of combustion of the fuel is released. The heat heats the multilayer walls 3-6 of the combustion chamber 2: first, a heavy lining 3, then partially delayed by a lightweight lining with a low heat transfer coefficient 4, heats the air channel 5 and is finally delayed by thermal insulation 6.

The water-cooled frame 7 cools the grate 1 and removes excess heat from the multilayer walls of the combustion chamber 2. Using the multilayer screen 10 prevents overcooling of the grate. The temperature of the multilayer walls 3-6 of the combustion chamber 2 is maintained in the operating range due to the presence of a heat-insulating layer 11.

The water-cooled frame 7 divides the furnace into two zones: the upper hot one, consisting of a combustion chamber 2 with multilayer walls 3-6, and the lower cold one, consisting of a grate 1, a drive device 9 of moving grates, etc. This separation optimizes the operation of both the combustion chamber 2 and the grate 1. The excess heat coming from above is absorbed by the water-cooled frame 7 and does not interfere with the work of the grate of the grate 1, drive 9 of the moving grate, etc. Moreover, the water-cooled frame 7 is part of the proposed design, which simplifies the design and reduces the weight of the furnace of a solid fuel boiler.

Claims (1)

A solid fuel boiler furnace containing a movable grate with grill grates, a combustion chamber with multilayer walls made sequentially from the inside of a heavy lining with a high heat transfer coefficient, a lightweight lining with a low heat transfer coefficient, an air channel, and thermal insulation, characterized in that it additionally contains a water-cooled made around the perimeter of the grate of a rectangular metal pipe filled with water, while the multilayer walls The ki of the combustion chamber are mounted on a water-cooled frame.

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