CZ278769B6 - Process for burning brown coal in a stoker-fired boiler - Google Patents

Abstract

In the grate boiler with at least one grate chamber and at least one undergrowth chamber, air is blown with the undergrowth chamber into the grate chamber and into this blower air at a temperature of 160 to 180 ° C and a pressure of 0.5 up to 0.8 MPa water is injected at a pressure of 0.4 up to 0.6 MPa, with the maximum amount injected water is 0.8 m3 per hour for each undergrowth chamber at fuel calorific value at least 9 210 kJ / kg and / or minimal the amount of water injected is 0.3 m3 / hr at maximum fuel calorific value of 12,351 kJ / kg.

Description

The subject of the invention is a method of burning brown coal in a grate boiler.

In Poland, industrial boilers are heated with both lignite and lignite, as well as waste products such as sawdust, sludge and, in special cases, litter. Carbon is the basic fuel component. In pure carbon combustion, the amount of heat produced is 33,900 kJ / kg. In addition to carbon, solid fuel contains hydrogen, three organic forms of sulfur, more than 40% oxygen, phosphorus, nitrogen. A wide range of different types of brown coal is used as fuel.

Incineration in the furnace consists in the interaction of the fuel components with the oxygen contained in the air, generating light and heat. To initiate combustion, the fuel must be heated to the ignition temperature at which ignition takes place. The ignition temperature depends on the type of fuel, its chemical composition, classification. The smaller the fuel particles, the easier the ignition. The final products of combustion are carbon dioxide C0 ₂ , sulfur dioxide S0 _? and NO ₂ . Incomplete combustion occurs when the flue gas contains carbon monoxide CO and unburnt hydrocarbons, which are normally not determinable. Therefore, it is necessary to ignite the fuel in excess air so that each fuel particle has an excess of oxygen.

In brown-coal-fired power plants, the flue gas may contain various oxides, depending on the method of burning brown coal - carbon dioxide CO ₂ , carbon monoxide CO, oxygen O ₂ , nitrogen N ₂ , sulfur dioxide SO ₂ , nitrogen oxides Ν _χ Ο ^. The result of the reaction of CO ₂ , SO ₂ , SO ₃ , N ₂ O ₅ with saturated steam at a pressure of 19 613.3 Pa to

400.9 Pa blowing into the chamber is the formation of weakly corrosive carbonic and sulfuric acids together with strongly corrosive sulfuric and nitric acids. The reaction of hot condensed steam with combustion products produces a gas containing carbonic acid, sulfuric acid, sulfuric acid, nitrous acid and nitric acid. The mixture of these combustion products has different concentrations of the individual components, which depend on gas dissolution, evaporation, moisture, condensate amount. The approximate composition of the flue-gases in lignite combustion is as follows:

n ₂ 0 ₅ 190 250 mg / Nm ³ what 21 27 Mar: mg / Nm ³ Sat ₃ 2100 2400 O mg / Nm diffused fly ash around 200 mg / Nm ³

the gas temperature in the channels is 240 ° C

When coal is burned, it is easy to produce a slag with a high content of combustible particles with melting ash or brown coal lumps. The slag clogs the grate vents and the lumps of sintered slag prevent the passage of air, resulting in uneven combustion. This can be avoided by increasing the excess air, which reduces the furnace - furnace temperature and produces less slag. Boiler efficiency will decrease - but when burning unsuitable or bad coal it is necessary to count with worse boiler efficiency. The use of charcoal, which produces a strong cinder, gives good blowing results

Saturated steam at a pressure of 19,613.3 Pa and 32,419.9 Pa to the zone where the most intense combustion occurs and where the boiler temperature is highest. The amount of steam used is 0.25 to 0.5% of the total amount of steam produced. The steam cools the bars and the granulated sintered slag, which becomes a loose. The use of this method not only allows better combustion, but also protects the large grate from premature wear. It is also necessary to prevent the grate from stopping, since the grate bars are overheated and more slag is formed when stopped.

The aforementioned drawbacks are eliminated by a method of burning brown coal in a grate boiler with at least one grate chamber and at least one under grate chamber according to the invention, in which air is blown from the under grate chamber into the grate chamber, up to 180 ° C and a pressure of 0.5 to 0.8 MPa, water is injected at a pressure of 0.4 to 0.6 MPa, with the maximum amount of water injected

O

0,8 m per hour for each undergrowth chamber with a fuel calorific value of at least 9210 kJ / kg and / or the minimum injection rate

O is 0.3 m / h with a maximum fuel calorific value of 12,351 kJ / kg.

The injected water streams are metered to ensure adequate evaporation of water throughout the volume of vaporized air. The treated air thus injected allows a complex effect, which is to lower the air temperature by converting this temperature to vaporize the water and break the sintered lumps by the steam contained in the air. A lower air temperature lowers the combustion temperature, resulting in less caking.

The invention allows a remarkable reduction of the combustion temperature in the fuel layer without noticeable disturbance of the heat balance in the furnace chamber. This contributes to the granulation of the fuel in the layer, which results in a reduction of the furnace stack loss of about 2 to 3%. Furthermore, the reduction of the excess air for combustion allows a reduction in the boiler heat loss of about 2 to 3%. Further, the degree of sulfur bound in the cinder components is increased and the release of nitrogen oxide is reduced.

The method of combustion of lignite in a grate boiler according to the invention will be more readily understood from the exemplary embodiment and from the accompanying drawing, in which Fig. 1 schematically shows the grate of the boiler, the airflow draft zone and water evaporation.

Fig. 1 shows a boiler with a combustion chamber 4, with a grate 6 and under grate chambers 7. The figure also shows a layer of brown coal 5 lying on the grate 6. The boiler is further provided with an air duct 2 and water distribution 3, to which sprayer connected 1.

The combustion process is then as follows. A layer of lignite 5 is combusted on the grate 6, with heated air being blown from the air duct 2 into the combustion chamber 4 by the sub-grate chambers 7. Water is injected into the blown air heated to the desired temperature, i.e. about 160 to 180 ° C and at a pressure of about 0.5 to 0.8 MPa, from a sprayer 1 supplied by a water distribution system 3.

0.4 to 0.6 MPa. The maximum amount of water injected is 0.8 m per hour for each underframe chamber 7 with a fuel calorific value of at least 9 210 kJ / kg. The minimum amount of water injected is then

-2GB 278769 B6

0.3 m ³ per hour at a maximum calorific value of 12 351 kJ / kg.

Example

Without water With a water addition of 0.3 m ³ / h Fuel calorific value [kJ / kg] 11 731.4 11 827.7 Chimney loss [%] 18.75 16.63 He didn't finish in the cinder [%] 8.94 8.67 Heat loss of the furnace [%] 9.78 9.67 Efficiency [%] 69.51 71.66

The efficiency increase was 2.15% and the stack loss decreased by 2.12%.

By utilizing the invention, the combustion process in lignite furnaces and industrial furnaces is improved by reducing the combustion temperature of the fuel and more uniformly releasing the burnt fuel to the grate. By using this process, brown coal is better burned and furnace losses are reduced.

Claims (1)

A method of combusting lignite in a grate boiler with at least one grate chamber and at least one undergrowth chamber, wherein air is blown from the undergrowth chamber into the grate chamber, characterized in that it is blown into air at 160 to 180 ° C and a pressure of 0.5 up to 0.8 MPa, water is injected at a pressure of 0.4 to 0.6 MPa, with a maximum injection rate of 0.8 m ³ per hour for each sub-grid chamber with a fuel calorific value of at least 9 210 kJ / kg and / or a minimum , the amount of water injected is 0.3 m / h with a maximum fuel calorific value of 12 351 kJ / kg.