CN111780095B - Combustion system and control method thereof, preheating equipment - Google Patents

Abstract

The invention relates to a combustion system comprising: the preheating device comprises preheating chambers, a first gas-solid separator and a material returning device which are communicated with each other in pairs; the upper outlet of the first gas-solid separator is communicated with the inlet of the second gas-solid separator, and the second gas-solid separator is provided with a gas fuel outlet positioned at the upper part and a solid fuel outlet positioned at the lower part; the hearth is provided with a solid fuel inlet and a gas fuel inlet, the solid fuel outlet is communicated with the solid fuel inlet, the gas fuel outlet is communicated with the gas fuel inlet, and the gas fuel inlet is higher than the solid fuel inlet in the height direction. The invention also relates to a preheating device and a method for controlling a combustion system.

Description

Combustion system and control method thereof, preheating equipment

Technical Field

The embodiments of the present invention relate to the field of preheating combustion, and in particular to a combustion system and a control method thereof, and a preheating device.

Background Art

China is a country that uses coal as its main energy source, with an annual coal consumption of about 2.4 billion tons. NOx emitted from coal combustion is an important cause of atmospheric haze. The original NOx emissions of boilers burning bituminous coal and lignite are mostly above 200 mg/ ^m3 . They achieve ultra-low NOx emission levels through non-selective catalytic reduction SNCR and selective catalytic reduction SCR combined denitrification measures (SNCR and SCR are post-combustion removal technologies). The original NOx emissions of boilers burning anthracite are mostly above 600 mg/ ^m3 . Even through SNCR and SCR combined denitrification measures, it is impossible to achieve ultra-low NOx emission levels below 50 mg/ ^m3 . In addition, the combined denitrification process of SNCR and SCR will bring about secondary pollution problems caused by ammonia escape. Therefore, significantly reducing NOx emissions during coal powder combustion is an important direction for the development of clean coal combustion technology and coal-fired boilers and a major demand of the industry.

Preheating combustion is a method of preheating pulverized coal and then burning it. The preheating temperature of pulverized coal is higher than 800°C. During the preheating process, not only is the fuel modified, but the conversion rate of coal nitrogen to _N2 can reach more than 40%. Preheating creates conditions for efficient combustion and low NOx emissions of coal, especially low-volatile coal.

However, during the preheating combustion of pulverized coal, the preheating fuel enters the furnace all at once, which is not conducive to the efficient reduction of NOx generated by the combustion of the preheating fuel.

Summary of the invention

The present invention is proposed to alleviate or solve at least one aspect or at least one point of the above problems.

In the present invention, a strong reducing gas such as high-temperature coal gas can be used to achieve NOx reduction, which can significantly reduce the NOx emission level of coal powder preheating combustion, and is conducive to achieving ultra-low NOx emissions of coal powder preheating combustion.

According to one aspect of an embodiment of the present invention, a combustion system is provided, comprising:

A preheating device, the preheating device comprising a preheating chamber, a first gas-solid separator and a material return device which are interconnected;

A second gas-solid separator, wherein the upper outlet of the first gas-solid separator is communicated with the inlet of the second gas-solid separator, and the second gas-solid separator has a gas fuel outlet at the upper part and a solid fuel outlet at the lower part;

The furnace is provided with a solid fuel inlet and a gas fuel inlet, wherein the solid fuel outlet is communicated with the solid fuel inlet, the gas fuel outlet is communicated with the gas fuel inlet, and the gas fuel inlet is higher than the solid fuel inlet in height direction.

According to another aspect of an embodiment of the present invention, a control method for the above-mentioned combustion system is proposed, wherein the furnace is provided with a tertiary air inlet, and the tertiary air inlet is located between the solid fuel inlet and the gas fuel inlet in the height direction, and the method comprises the steps of: allowing the solid fuel from the second gas-solid separator and the gas fuel to be burned in partitions.

According to another aspect of an embodiment of the present invention, a preheating device is provided, comprising:

A preheating device, the preheating device comprising a preheating chamber, a first gas-solid separator and a material return device which are interconnected; and

The second gas-solid separator, the upper outlet of the first gas-solid separator is communicated with the inlet of the second gas-solid separator, and the second gas-solid separator has a gas fuel outlet located at the upper part and a solid fuel outlet located at the lower part.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a combustion system according to an exemplary embodiment of the present invention;

FIG2 is a schematic diagram exemplarily illustrating the division of combustion zones of the combustion system in FIG1 ;

FIG3 is a schematic diagram of a combustion system according to another exemplary embodiment of the present invention;

FIG. 4 is a schematic diagram of a combustion system according to yet another exemplary embodiment of the present invention.

DETAILED DESCRIPTION

The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention, and should not be understood as a limitation of the present invention. In the accompanying drawings, the same reference numerals represent the same or similar components.

As shown in FIG. 1 , a boiler (corresponding to a combustion system) according to an exemplary embodiment of the present invention mainly includes a preheater 1 , a gas-solid separator 2 and a furnace 3 .

In one embodiment, the preheater 1 is a circulating fluidized bed, and the primary air transports the pulverized coal into the preheater, where the pulverized coal is preheated to a temperature above 800° C. After preheating, the pulverized coal is converted into preheating fuel containing high-temperature coal gas and high-temperature coke.

As shown in FIG1 , the preheater 1 includes a preheating chamber 10, which provides a space for preheating the fuel. Although not shown, the preheating chamber may be provided with: a fuel inlet, which is provided at the lower part or bottom of the preheating chamber 10, and is suitable for passing the fuel, such as coal, into the preheating chamber; a preheating air inlet, which is provided at the bottom of the preheating chamber 10, and is suitable for passing the preheating air into the preheating chamber. The preheating air will be used to fluidize the solid materials in the preheating chamber 10 and provide oxygen required for partial combustion of the fuel. In conjunction with the preheating air inlet, an air distribution device may be provided at the bottom of the preheating chamber 10 to uniformly pass the preheating air into the preheating chamber.

As shown in FIG1 , the preheater further includes a first gas-solid separator 12, which may be a cyclone separator. Although not shown, it may include: a barrel section, a cone section and a top plate. The upper portion of the separator 12 is connected to the upper portion of the preheating chamber 10, and is suitable for separating the high-temperature fuel preheated in the preheating chamber; a central barrel is provided on the top plate, and the high-temperature fuel (including high-temperature coal gas and high-temperature coke) that meets the requirements after preheating leaves the first gas-solid separator 12 from the central barrel; a discharge pipe is provided at the lower portion of the cone section, and the high-temperature solid fuel and bed material captured by the separator enter the discharge pipe. The barrel section corresponds to the separation chamber of the first gas-solid separator.

As shown in FIG. 1 , the preheater further includes a returner 13 , which is connected to a feed pipe at the lower portion of the first gas-solid separator 12 and a lower portion of the preheating chamber 10 , and is suitable for returning high-temperature solid fuel and bed material in the feed pipe to the preheating chamber 10 .

The gas-solid separator 2 is the second gas-solid separator, including an inlet, a gas outlet and a solid outlet. It can be a cyclone separator or an inertial separator, and can have the same structure as the first gas-solid separator, that is, it has a cyclone tube and a feed pipe 21 (corresponding to the solid outlet) and an upper outlet (corresponding to the gas outlet). Its inlet is connected to the outlet of the center tube of the first gas-solid separator 12, the gas outlet of the second gas-solid separator is connected to the furnace, and the solid outlet is connected to the furnace through another position. The high-temperature fuel (high-temperature coal gas carrying high-temperature coke) from the center tube of the first gas-solid separator 12 flows into the gas-solid separator 2. Under the separation action of the second gas-solid separator, the solid particles (high-temperature coke) enter the boiler for combustion from the separator feed pipe 21 through the high-temperature solid fuel nozzle; the gas carries a small amount of unseparated coke through the upper outlet 22 and enters the furnace at a different position from the high-temperature solid fuel.

As shown in FIG1 , the furnace wall of the furnace includes a shoulder A, which makes the cross-sectional area of the lower part of the furnace larger than that of the upper part of the furnace, and the external included angle θ between the shoulder A and the vertical direction is an obtuse angle (in the figure, it is assumed that the furnace wall above the shoulder of the furnace is a vertical wall, corresponding to the vertical direction), and the shoulder A and other furnace walls together define the internal space of the furnace; and the high-temperature solid fuel separated by the second separator enters the furnace from the position of the shoulder, and a high-temperature solid fuel nozzle is provided at the shoulder. The high-temperature gas fuel nozzle 22 is provided on the vertical wall surface of the furnace. Above the high-temperature gas fuel nozzle 22, a burnout air 33 is also provided.

The space of the furnace is divided into a lower space and an upper space by a horizontal plane at the intersection of the furnace shoulder A and the vertical wall of the furnace. More specifically, the front wall and the rear wall of the lower part of the furnace 3 are inclined outwards compared with the upper part (the inclined part constitutes the shoulder A), the lower space of the furnace is large, the furnace 3 includes a uniform secondary air distribution device 31 located at the bottom of the furnace, the secondary air is uniformly supplied from the bottom of the furnace, after the preheated fuel is sprayed into the furnace from the shoulder obliquely downward, it reacts with the secondary air from the bottom of the furnace, the slag formed by the high-temperature coke during the combustion process at the bottom of the furnace can be discharged from the bottom of the boiler, the tertiary air is sprayed from the adjacent parts of the lower space and the upper space of the furnace, and the tertiary air inlet is arranged on the vertical wall of the furnace. The amount of secondary air is controlled so that the area between the secondary air and the tertiary air nozzle 32 (in the lower space of the furnace) is a high-temperature coke reduction zone, and the high-temperature coke burns in a reducing atmosphere; the area between the tertiary air nozzle 32 and the high-temperature gas fuel nozzle 22 (in the upper space of the furnace) is a high-temperature coke oxidation zone, the area from the high-temperature gas fuel nozzle 22 to the burnout air 33 is a high-temperature coal gas reduction zone, and the area above the burnout air 33 is a burnout zone. The above high-temperature coke reduction zone, high-temperature coke oxidation zone, high-temperature coal gas reduction zone and burnout zone are exemplarily shown in FIG. 2.

Therefore, in the embodiment shown in Figure 1, the high-temperature gas-solid mixed fuel containing high-temperature coal gas and high-temperature coke generated after the coal powder is preheated is not directly sprayed into the furnace, but passes through the gas-solid separator 2 to achieve the zoned combustion of high-temperature coke and high-temperature coal gas. Thus, the combustion in the furnace can be divided into four control areas: high-temperature coke reduction zone-high-temperature coke oxidation zone-high-temperature coal gas reduction zone-burnout zone.

The specific working process and principle of the embodiment in FIG. 1 are exemplarily described below.

The primary air transports the coal powder to the preheater 1. The preheater can be a circulating fluidized bed. The primary air volume accounts for 15-30% of the theoretical combustion air volume of the coal powder, that is, the primary air-fuel equivalence ratio is 0.15-0.30. The circulating fluidized bed can be adiabatic or have a built-in water-cooled heating surface. The coal powder preheating temperature is 800-1000°C, which exceeds the ignition point. During the preheating process of the bituminous coal powder in the preheater, the volatile matter and part of the coke released by the bituminous coal powder undergo combustion and gasification reactions with the primary air to maintain heat balance, and are converted into high-temperature coal gas at the same time. The solid materials that have not reacted with the primary air are converted into high-temperature coke. After the coal powder is preheated by the circulating fluidized bed, the inner pores of the coke become rich and the activity is enhanced, which is conducive to the combustion and burnout of the coke. In order to promote the modification effect of the coke, some water vapor can also be introduced into the preheater to achieve the coke activation effect. During the preheating process of coal powder in the circulating fluidized bed, the bed is filled with a strong reducing atmosphere, and the coal nitrogen precipitated during the preheating is easily converted into _N2 , which creates conditions for ultra-low NOx emissions from coal combustion.

After the preheated fuel enters the separator 2, gas-solid separation can be achieved, and the solid, i.e., high-temperature coke, flows into the lower part of the boiler furnace. Since the temperature of the high-temperature coke exceeds 800°C, the high-temperature coke has already caught fire. Therefore, after the high-temperature coke is sprayed into the furnace, it meets the secondary air that flows uniformly from the bottom of the furnace to generate a spatial combustion reaction. The secondary air at the bottom of the furnace plays a role in both combustion support and bottom support, preventing coal powder particles from directly rushing into the ash hopper area at the bottom of the furnace to reduce combustion losses.

The area between the secondary air and the tertiary air in the lower part of the furnace is the high-temperature coke reduction zone. Since the high-temperature coke is fully mixed with the secondary air, the local oxygen concentration is low, and the temperature of the reduction zone is high, the temperature of the reduction zone can be controlled below the ash melting point, for example, 1200°C. This can reduce the slagging tendency of the ash and is beneficial to the stable operation of the boiler. On the other hand, in such a temperature range, especially when the furnace temperature is higher than 1000°C, the reduction reaction of coke and nitrogen oxides has a higher rate, which can effectively reduce nitrogen oxides and better avoid the formation of thermal NOx.

The area between the tertiary air nozzle 32 and the high-temperature gas fuel nozzle 22 is the high-temperature coke oxidation zone. The high-temperature coke burns out in this area. The combustion temperature is, for example, 1100°C. Because most of the N in the high-temperature coke has been precipitated in the reduction zone and converted to _N2 , the high-temperature coke has very little N content in the oxidation zone. After the N in the coke is precipitated from the surface, part of it is converted into NOx and part of it is converted into _N2 .

The NOx formed by the N in the high-temperature coke moves upward with the air flow and enters the high-temperature coal gas reduction zone again. Because the high-temperature gas fuel contains strong reducing gases such as _CH4 , _H2 , and CO, the NOx formed by the high-temperature coke is easily reduced and converted to _N2 . At the same time, some HCN and _NH3 in the coal gas will also undergo reduction reactions.

Finally, the gases from the combustion of high-temperature solid fuel and high-temperature gas fuel enter the burnout zone, and the unreacted gases or a very small amount of coke particles are mixed with the burnout air and burned out.

By setting a gas-solid separator 2 at the outlet of the preheater, the stratified and zoned combustion of high-temperature coke and high-temperature coal gas is realized, the combustion reaction time of high-temperature coke is effectively prolonged, and different control methods for the migration and transformation of coke nitrogen and volatile nitrogen are realized, that is, coke nitrogen is mainly reduced with coke in a heterogeneous manner after being precipitated in the lower part of the furnace, and volatile nitrogen undergoes reduction reaction with generated NOx and reduction reaction of hydrocarbon gas or CO in the high-temperature coal gas reduction zone. In addition, during the preheating combustion of pulverized coal, the combustion temperature can be controlled to be lower than the ash melting point, reducing the tendency of slagging corrosion in the furnace, which is conducive to the stable and safe operation of the boiler.

In a more specific exemplary embodiment, the primary air carries bituminous coal into the preheater, the primary air equivalent ratio is 0.2-0.3, the preheater operating temperature is 800-900°C, the preheated fuel flows out of the nozzle at a speed of 20-30m/s, and the preheated fuel flows into the gas-solid separator 2 to achieve the separation of high-temperature gas and high-temperature coke. The high-temperature coke is sprayed into the high-temperature coke reduction zone from the bottom at a speed of 3-8m/s, and the high-temperature gas is sprayed into the upper part of the furnace at a speed of 20-35m/s. The secondary air equivalent ratio is 0.3-0.5, the average combustion temperature of high-temperature coke is 1100°C, the tertiary air equivalent ratio is 0.2-0.4, the burnout air equivalent ratio is 0.1-0.3, and the NOx emission of bituminous coal powder preheating combustion is about 30-50mg/ ^m3 .

In another more specific exemplary embodiment, the primary air carries anthracite into the preheater, the primary air equivalent ratio is 0.1-0.2, the preheater operating temperature is 900-1000°C, the preheated fuel flows out of the nozzle at a speed of 15-25m/s, and the preheated fuel flows into the gas-solid separator 2 to achieve the separation of high-temperature gas and high-temperature coke. The high-temperature coke is sprayed into the high-temperature coke reduction zone from the bottom at a speed of 3-8m/s, and the high-temperature gas is sprayed into the upper part of the furnace at a speed of 20-35m/s. The secondary air equivalent ratio is 0.3-0.5, the average temperature of high-temperature coke combustion is 1100°C, the tertiary air equivalent ratio is 0.2-0.4, the burnout air equivalent ratio is 0.1-0.3, and the NOx emission of anthracite powder preheating combustion is about 50-80mg/ ^m3 .

In the structure shown in Figures 1-2 and the subsequently mentioned Figures 3 and 4, secondary air is provided from the bottom of the furnace in a vertically upward direction. The secondary air serves as both combustion-supporting air and bottom supporting air, thereby reducing the risk of preheated fuel or solid fuel directly rushing into the ash hopper area at the bottom of the furnace.

In an optional embodiment, although not shown, the secondary air vents may also be provided on the inclined side wall of the lower portion of the furnace as shown in FIGS. 1-4 , so as to provide secondary air in an inclined upward direction. In a further optional embodiment, the angle formed between the outlet direction of the secondary air vents and the direction in which the solid fuel enters the furnace is an acute angle greater than 30 degrees.

Furthermore, in an optional embodiment, although not shown, the direction of the secondary air provided by the secondary air vent is not limited to being inclined upward, but may also be roughly horizontal, as long as it is conducive to lifting the solid fuel.

In Fig. 1-2, the lower part of the furnace is enlarged due to the presence of the shoulder A, but the present invention is not limited thereto. Fig. 3 is a schematic diagram of a combustion system according to another exemplary embodiment of the present invention, wherein the overall cross-sectional shape of the furnace combustion area above the preheating fuel nozzle can remain unchanged. As can be understood by those skilled in the art, the "remaining unchanged" here also includes the situation of being substantially unchanged.

As shown in FIG3 , the furnace is provided with a fuel inlet channel B, which is communicated with the high-temperature solid fuel nozzle. As shown in FIG3 , the fuel inlet channel extends obliquely downward, and the solid fuel outlet of the second separator 2 is communicated with the fuel inlet channel A.

As shown in FIG. 3 , the fuel inlet channel B includes an end portion B1 , the end surface of the end portion forms an obtuse angle θ with the outer portion in the vertical direction, and the solid fuel outlet of the second separator 2 is connected to the fuel inlet channel B at the end surface.

In FIGS. 1-3 , two sets of preheating devices and second separators are arranged on opposite vertical walls of the furnace, but the present invention is not limited thereto. One set of preheating devices and one second separator may also be arranged on only one vertical wall of the furnace, as shown in FIG. 4 .

In the present invention, the high-temperature gas-solid mixed fuel containing high-temperature coal gas (i.e., high-temperature gas fuel) and high-temperature coke (i.e., high-temperature solid fuel) generated after the coal powder is preheated is first separated from the high-temperature coal gas and the high-temperature coke by a gas-solid separator. The high-temperature coke enters from the bottom of the furnace and the high-temperature coal gas enters from the top of the furnace. The combustion area of the furnace can be divided into a high-temperature coke reduction zone, a high-temperature coke oxidation zone, a high-temperature coal gas reduction zone and a burnout zone with a reducing and oxidizing alternating atmosphere, thereby realizing the zoning control of high-temperature coke combustion and high-temperature coal gas combustion, and achieving the effect of low (ultra-low) NOx emissions from a pulverized coal boiler.

By adopting the scheme of the present invention, a coal pulverized preheating combustion ultra-low NOx boiler can be realized, which can achieve low (ultra-low) NOx emissions of bituminous coal, lignite and anthracite. For example, the original NOx emission of bituminous coal combustion can be lower than 50 mg/m ³ , and ammonia injection facilities are no longer required, which reduces the secondary pollution of ammonia escape, eliminates the technical difficulties of catalyst secondary disposal, and improves economic and environmental benefits. For another example, the original NOx emission of anthracite combustion can be lower than 100 mg/m ³ or directly reach below 50 mg/m ^3. Combined with SNCR measures, ultra-low NOx emissions of anthracite combustion can be achieved, solving the technical problem that anthracite combustion cannot meet ultra-low NOx emissions.

By adopting the scheme of the present invention, the combustion temperature of pulverized coal can be lower than the ash melting point, reducing the risk of boiler slagging, which is conducive to safe and stable operation.

By adopting the scheme of the present invention, the secondary air at the bottom of the boiler furnace serves as combustion-supporting air and bottom supporting air, reducing the risk of preheated fuel directly rushing into the ash hopper area at the bottom of the furnace. Through the uniform arrangement of the secondary air, high-temperature coke achieves volumetric combustion at the bottom of the furnace.

In the present invention, the structure formed by the preheating device and the second separator can form a preheating device, which is not limited to the preheating system or boiler combustion system shown in Figures 1-4, and can also be used alone or in combination with other devices other than the pulverized coal boiler.

It should be pointed out that in the present invention, each numerical range, except for explicitly stating that it does not include the endpoint value, can be the endpoint value or the median value of each numerical range, all of which are within the protection scope of the present invention.

Based on the above, the present invention proposes the following technical solutions:

1. A combustion system, comprising:

A preheating device, the preheating device comprising a preheating chamber, a first gas-solid separator and a material return device which are interconnected;

A second gas-solid separator, wherein the upper outlet of the first gas-solid separator is communicated with the inlet of the second gas-solid separator, and the second gas-solid separator has a gas fuel outlet at the upper part and a solid fuel outlet at the lower part;

The furnace is provided with a solid fuel inlet and a gas fuel inlet, wherein the solid fuel outlet is communicated with the solid fuel inlet, the gas fuel outlet is communicated with the gas fuel inlet, and the gas fuel inlet is higher than the solid fuel inlet in height direction.

2. The combustion system according to item 1, wherein:

The furnace is provided with a secondary air inlet, which is lower than the solid fuel inlet in height direction.

3. The combustion system according to 2, wherein:

The secondary air from the secondary air inlet is vertical secondary air; or

The secondary air from the secondary air inlet is horizontal or inclined upward secondary air.

4. The combustion system according to 2, wherein:

The secondary air inlet is arranged on the inclined side wall at the lower part of the furnace, and the angle formed between the air outlet direction of the secondary air inlet and the direction in which the solid fuel enters the furnace is an acute angle greater than 30 degrees.

5. A combustion system according to any one of 1 to 4, wherein:

The furnace is provided with a tertiary air inlet, and the tertiary air inlet is located between the solid fuel inlet and the gas fuel inlet in the height direction.

6. A combustion system according to any one of 1 to 5, wherein:

The furnace is provided with a burnt-out air inlet, which is higher than the gas fuel inlet.

7. The combustion system according to item 1, wherein:

The first gas-solid separator and the second gas-solid separator are both cyclone separators.

8. The combustion system according to item 1, wherein:

Two opposite furnace walls of the furnace are respectively provided with a preheating device and a second gas-solid separator.

9. The combustion system according to item 1, wherein:

The solid fuel is coke produced by a preheating device, and the gaseous fuel is coal gas produced by a preheating device.

10. The combustion system according to any one of 1 to 9, wherein:

The furnace wall of the furnace comprises a shoulder, the outer angle between the shoulder and the vertical direction is an obtuse angle between 90 degrees and 180 degrees, and the shoulder defines a part of the inner space of the furnace; and

The solid fuel inlet is disposed on the shoulder.

11. The combustion system according to any one of 1 to 9, wherein:

The furnace is provided with a fuel inlet channel, the fuel inlet channel is communicated with the solid fuel inlet, and the fuel inlet channel extends obliquely downward, and the solid fuel outlet is communicated with the fuel inlet channel.

12. The combustion system according to 11, wherein:

The fuel inlet passage comprises an end portion, an end surface of the end portion forms an obtuse angle with an outer portion in the vertical direction between 90 degrees and 180 degrees, and the solid fuel outlet is connected to the fuel inlet passage at the end surface.

13. The combustion system according to 12, wherein:

The overall cross-sectional shape of the furnace upward from the solid fuel inlet remains unchanged.

14. A method for controlling a combustion system according to 5, the method comprising the steps of:

The solid fuel and the gaseous fuel from the second gas-solid separator are combusted in different areas.

15. The method according to 14, wherein the combustion system is the combustion system according to 5, primary air and solid fuel are introduced into the preheating chamber, and the furnace is provided with a secondary air inlet, a tertiary air inlet and a burnout air inlet, and the method comprises the steps of:

The combustion areas in the furnace are solid fuel reduction zone, solid fuel oxidation zone, gas fuel reduction zone and burnout zone in the height direction, among which: the solid fuel reduction zone is between the secondary air inlet and the tertiary air inlet, the solid fuel oxidation zone is between the tertiary air inlet and the gas fuel inlet, the gas fuel reduction zone is between the gas fuel inlet and the burnout air inlet, and the burnout zone is above the burnout air inlet.

16. The method according to 15, wherein:

The primary air volume accounts for 15-30% of the theoretical combustion air volume of the solid fuel entering the preheating chamber, the secondary air volume accounts for 25-70% of the theoretical combustion air volume of the solid fuel entering the preheating chamber, the tertiary air volume accounts for 20-40% of the theoretical combustion air volume of the solid fuel entering the preheating chamber, and the burnout air volume accounts for 10-40% of the theoretical combustion air volume of the solid fuel entering the preheating chamber.

17. A preheating device comprising:

A preheating device, the preheating device comprising a preheating chamber, a first gas-solid separator and a material return device which are interconnected;

The second gas-solid separator, the upper outlet of the first gas-solid separator is communicated with the inlet of the second gas-solid separator, and the second gas-solid separator has a gas fuel outlet located at the upper part and a solid fuel outlet located at the lower part.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made to the embodiments and combinations of elements may be made without departing from the principles and spirit of the invention, the scope of the invention being defined by the appended claims and their equivalents.

Claims (15)

1. A combustion system, comprising:

the preheating device is used for preheating fuel and comprises preheating chambers, a first gas-solid separator and a material returning device which are communicated with each other in pairs;

a second gas-solid separator having a gas fuel outlet at an upper portion and a solid fuel outlet at a lower portion;

A hearth provided with a solid fuel inlet and a gaseous fuel inlet,

Wherein:

An inlet of the first gas-solid separator is communicated with an outlet of the preheating chamber, and an upper outlet of the first gas-solid separator is communicated with an inlet of the second gas-solid separator;

The solid fuel outlet of the second gas-solid separator is communicated with the solid fuel inlet through a blanking pipe of the second gas-solid separator, the gas fuel outlet of the second gas-solid separator is communicated with the gas fuel inlet, and the gas fuel inlet is higher than the solid fuel inlet in the height direction;

The gas fuel and the solid fuel generated by the preheating device are suitable for entering the hearth through a gas fuel outlet and a solid fuel outlet of the second gas-solid separator;

the hearth is provided with a tertiary air inlet which is positioned between the solid fuel inlet and the gas fuel inlet in the height direction;

The hearth area between the tertiary air inlet and the gas fuel inlet is a high-temperature coke oxidation area, and the hearth area below the tertiary air inlet is a high-temperature coke reduction area;

The hearth is sequentially provided with a high-temperature coke reduction area, a high-temperature coke oxidation area, a high-temperature gas reduction area and a burnout area from bottom to top.

2. The combustion system of claim 1, wherein:

The furnace is provided with a secondary air inlet which is lower than the solid fuel inlet in the height direction.

3. The combustion system of claim 2, wherein:

The secondary air from the secondary air inlet is vertical secondary air; or alternatively

The secondary air from the secondary air inlet is transverse or inclined upward.

4. The combustion system of claim 2, wherein:

The secondary air inlet is arranged on the inclined side wall of the lower part of the hearth, and the angle formed between the air outlet direction of the secondary air inlet and the direction of the solid fuel entering the hearth is an acute angle larger than 30 degrees.

5. The combustion system of claim 1, wherein:

the furnace is provided with an overfire air inlet, which is higher than the gaseous fuel inlet.

6. The combustion system of claim 1, wherein:

the first gas-solid separator and the second gas-solid separator are cyclone separators.

7. The combustion system of claim 1, wherein:

The two opposite furnace walls of the furnace are respectively provided with a preheating device and a second gas-solid separator.

8. The combustion system of claim 1, wherein:

The fuel solid is coke generated by the preheating device, and the gas fuel is gas generated by the preheating device.

9. The combustion system of any one of claims 1-8, wherein:

The hearth wall of the hearth comprises a shoulder, the included angle between the shoulder and the outside of the vertical direction is an obtuse angle, and the shoulder defines a part of the internal space of the hearth; and is also provided with

The solid fuel inlet is disposed at the shoulder.

10. The combustion system of any one of claims 1-8, wherein:

the hearth is provided with a fuel inlet channel which is communicated with the solid fuel inlet, the fuel inlet channel extends obliquely downwards, and the solid fuel outlet is communicated with the fuel inlet channel.

11. The combustion system of claim 10, wherein:

The fuel inlet channel comprises an end part, the end surface of the end part and the outer included angle of the vertical direction are obtuse angles, and the solid fuel outlet is communicated with the fuel inlet channel at the end surface.

12. The combustion system of claim 11, wherein:

The overall cross-sectional shape of the furnace with the solid fuel inlet up remains unchanged.

13. A control method of a combustion system according to any one of claims 1-12, the method comprising the steps of:

the solid fuel from the second gas-solid separator and the gaseous fuel are combusted in separate zones.

14. The method of claim 13, the combustion system being according to claim 5, primary air and solid fuel being introduced into a preheating chamber, and the furnace being provided with a secondary air inlet, a tertiary air inlet and an overfire air inlet, the method comprising the steps of:

The combustion area in the hearth is sequentially provided with a solid fuel reduction area, a solid fuel oxidation area, a gas fuel reduction area and a burnout area in the height direction, wherein: the solid fuel reduction zone is arranged between the secondary air inlet and the tertiary air inlet, the solid fuel oxidation zone is arranged between the tertiary air inlet and the gas fuel inlet, the gas fuel reduction zone is arranged between the gas fuel inlet and the over-fire air inlet, and the over-fire zone is arranged above the over-fire air inlet.

15. The method according to claim 14, wherein:

The primary air volume accounts for 15-30% of the theoretical combustion air volume of the solid fuel entering the preheating chamber, the secondary air volume accounts for 25-70% of the theoretical combustion air volume of the solid fuel entering the preheating chamber, the tertiary air volume accounts for 20-40% of the theoretical combustion air volume of the solid fuel entering the preheating chamber, and the over-fire air volume accounts for 10-40% of the theoretical combustion air volume of the solid fuel entering the preheating chamber.