CN103398371B - A kind of two low type boiler using high basic metal coal - Google Patents

Abstract

A double-low boiler for burning high-alkali metal coal, including a furnace. The furnace is divided into a small-sized furnace dense-phase area and a large-sized furnace dilute-phase area. The small-sized furnace dense-phase area is connected to the coal feeding system, and the large-sized furnace is dilute-phase. The area is connected to the inlet flue of the separator, and the volume of the dilute-phase area of the large-sized furnace is more than 5 times that of the dense-phase area of the small-sized furnace. , reduce the operating temperature of the furnace and the outlet temperature of the separator, control the temperature of the combustion area between 650 and 850 ° C, change the precipitation form of alkali metals and their compounds and reduce their precipitation, so that the gaseous alkali metals and their compounds generated during combustion Most of the compounds are solidified in the fly ash, bottom slag and bed material, avoiding serious ash deposition and slagging, and improving the continuous operation cycle. The boiler also has low pollutant emissions, is not limited by unit capacity, and has wide adaptability to coal types. It has the advantages of low fuel load, high combustion efficiency, and low bottom slag discharge without oil injection.

Description

A double-low boiler for burning high-alkali metal coal

technical field

The invention belongs to the technical field of clean coal combustion and utilization, in particular to a double-low boiler for burning high-alkali metal coal.

Background technique

my country is a country rich in coal resources. The total coal resources are predicted to exceed 5 trillion tons, ranking third in the world. However, most of my country's coal resources are located in Xinjiang and other western regions. In the process of burning coal in Xinjiang and other places, it was found that a considerable number of boiler furnaces, superheaters and reheater areas would form large areas of highly cohesive ash in a short period of time, accompanied by severe high-temperature corrosion, and eventually This caused a large area of the boiler to explode, which directly affected the reliability, safety and economy of the boiler operation. Research has found that the main cause of the above problems is the high content of alkali metals such as sodium and potassium in coal. This type of coal with high alkali metal content generally has high moisture and volatile matter content, and low ash content and calorific value. Affected by the high content of alkali metals such as sodium and potassium in coal ash, the ash melting point of coal is generally low. During the combustion process, coal ash shows a strong staining property, which belongs to the strong ash-depositing and slagging type ash.

Because burning coal with high alkali metal content will cause the heating surface to be contaminated and affect the heat transfer of the boiler, in the existing technical means, generally by increasing the cross-sectional area of the furnace, optimizing combustion and air distribution, increasing the frequency of soot blowing, using additives, and mixing coal Burning and other means are delayed, but it is still difficult to cure. Combustion of coal with high alkali metal content is a major problem at home and abroad, so coal with high alkali metal content is only used in a few power plants in the United States, Australia and Xinjiang. During the process of co-firing, pulverized coal boilers are prone to slagging in the burner area of the furnace and contamination and clogging of high-temperature superheaters and high-temperature reheaters; circulating fluidized bed boilers are prone to coking on the bed surface and staining Dirt clogging problem. Although generally speaking, the operating period of circulating fluidized bed boilers burning coal with high alkali metal content is longer than that of pulverized coal boilers, and the blending ratio of circulating fluidized bed boilers is higher than that of pulverized coal boilers (generally 40% to 50% ), but due to the high price of the blended coal, the economy of unit operation has been significantly affected.

Therefore, in order to realize the large-scale utilization of coal resources in our country, it is urgent to seek a device and method for directly burning high-alkali metal coal.

Contents of the invention

In order to overcome the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a double-low boiler for burning high-alkali metal coal, which can cleanly and efficiently burn high-alkali metal coal and avoid ash accumulation and slagging.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A double-low type boiler burning high-alkali metal coal, including a furnace, the furnace is divided into a small-sized furnace dense-phase area 1 and a large-sized furnace dilute-phase area 2, and the small-sized furnace dense-phase area 1 is connected to a coal feeding system 18 , the large-size furnace dilute-phase zone 2 is connected to the separator inlet flue 3, and the volume of the large-size furnace dilute-phase zone 2 is more than 5 times the volume of the small-size furnace dense-phase zone 1.

The clear height of the large-size furnace dilute-phase zone 2 is more than twice the length of the small-size furnace dense-phase zone 1 or more than 5 times the width of the small-size furnace dense-phase zone 1 .

In the dilute-phase zone 2 of the large-sized furnace, there is an enhanced heating surface A in the furnace.

The enhanced heating surface A in the furnace is a panel-type heating surface arranged in multiple pieces.

The intercept between the panel heating surfaces is greater than 0.5m, the height is greater than 60% of the net height of the dilute-phase zone 2 of the large-scale furnace, and the width is greater than 15% of the net width of the dilute-phase zone 2 of the large-scale furnace.

The dense-phase zone 1 of the small-sized furnace is connected with a feeder 6 through a return pipe 7, and the feeder 6 is connected to the dust outlet of the eccentric cyclone separator 4 through the standpipe 5, and the dust-containing flue gas of the eccentric cyclone separator 4 The outlet is connected to the large-size furnace dilute phase zone 2 through the separator inlet flue 3, and the clean flue gas after dust removal by the eccentric cyclone separator 4 enters the diverting flue 9 from the separator center tube 8, and the diverting flue 9 is connected to the longitudinal tail flue 10. There is an ash hopper 11 at the bottom of the tail flue 10 .

In order to improve the combustion efficiency, the center cylinder of the separator can also adopt a variable diameter arrangement. The separation efficiency of the eccentric cyclone separator 4 of the present invention is above 99.5%.

The diversion flue 9 is provided with an additional enhanced cooling heating surface C, the additional enhanced cooling heating surface C is preferably a convective heating surface, which can reduce the flue gas temperature by more than 50°C.

The tail flue 10 is provided with a plurality of parallel tail flue heating surfaces B, and the cooled flue gas is finally discharged from the outlet of the tail flue 10 . Preferably, the heating surface B of the tail flue adopts a large intercept design, the intercept between the heating surfaces B of adjacent tail flues is greater than 0.15m, and the volume of the tail flue 10 is 20 times the volume of the heating surface B of the tail flue above.

The heating surface B of the tail flue,

The small-sized furnace dense-phase zone 1:

Connect the inert bed material addition system 14 through the inert bed material addition pipe 15;

Connect the desulfurizing agent adding system 16 through the desulfurizing agent adding pipe 17;

A slag outlet 23 is provided.

Limestone, slaked lime, carbide slag or substances that can act as desulfurizers can be regularly or continuously supplemented through the desulfurizer adding system 16 to reduce the concentration of SO2 emissions.

The inlet flue 3 of the separator is provided with a denitrification reducing agent injection port 21, through which denitrification reducing agent injection port 21 can be regularly or continuously sprayed into urea aqueous solution, ammonia water, liquid ammonia or substances that can serve as denitrification agents to reduce NO _x emission concentration.

The inlet flue 3 of the separator, the turning flue 9 and the tail flue 10 are all equipped with a flue gas along-process blowing and dust removal system 20, which performs enhanced soot blowing along the flue gas flow direction, and blows the flue gas along the course. There are dust removal holes around the dust removal system 20, which can be supplemented by manpower or machinery.

The flue gas blowing along the soot cleaning system 20 mainly includes soot blowers, which can be closely arranged between different heating surfaces or between different areas of the same heating surface along the flue gas flow direction, and the number of soot blowers is 1 per meter Above, the soot blowing medium can be steam, air, gas or water.

The dense-phase zone 1 of the small-sized furnace and the dilute-phase zone 2 of the large-sized furnace:

The working temperature is controlled between 650～850℃;

Air flow velocity is 3~5m/s;

The residence time of high alkali metal coal is more than 5s.

Compared with prior art, the beneficial effect of the present invention is:

1. Due to the low combustion temperature, the release of alkali metals and their compounds is minimized;

2. Although the combustion temperature has been reduced, the high-efficiency eccentric cyclone separator is used to realize the efficient capture and return of fly ash, the low air velocity, and the high net height of the furnace prolong the residence time of particles and ensure the combustion efficiency;

3. While burning high-alkali metal coal, desulfurization and denitrification are realized at the same time, and the environmental protection index of the boiler is superior;

4. Using a large amount of self-circulation of the bed material in the furnace ensures the self-cleaning effect of the water-cooled wall in the furnace and the enhanced heating surface in the furnace;

5. The ash accumulation on the heating surface of the large-volume tail flue and the large-intercept tail flue is very loose, and the dust removal system is easy to clean along the flue gas, avoiding deposition.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the present invention. .

FIG. 2 is a top view of FIG. 1 .

detailed description

The present invention will be further described below in conjunction with accompanying drawing. However, those skilled in the art understand that the protection scope of the present invention is not limited to the content of the following examples, and any improvements and changes made on the basis of the present invention are within the protection scope of the present invention.

Example 1:

A large boiler used to generate electricity that primarily burns coal with a high alkali metal content. Referring to Figures 1 and 2, the furnace of the boiler includes a small-sized furnace dense-phase area 1 and a large-sized furnace dilute-phase area 2 above it, and the small-sized furnace dense-phase area 1 is connected to the coal feeding system 18, desulfurizer addition system 16 and an inert bed material addition system 14, and a slagging port 23 is provided at the bottom. The dilute-phase zone 2 of the large-scale furnace is connected to the inlet flue 3 of the separator. In the dilute-phase zone 2 of the large-scale furnace, there is an enhanced heating surface A in the furnace, which is a panel-type heating surface arranged in 16 pieces. The fuel required for combustion is sent to the dense-phase zone 1 of the small-sized furnace through the coal feeding system 18 and the coal-falling pipe 19. In order to reduce the concentration of SO ₂ emissions, limestone is continuously added to the dense-phase zone 1 of the small-sized furnace through the desulfurizer adding system 16 As a desulfurizer for furnace desulfurization.

The dilute-phase zone 2 of the large-size furnace is designed with large volume and high clear height. The volume of the dilute-phase zone 2 of the large-size furnace is 5 times that of the dense-phase zone 1 of the small-size furnace. At the same time, the clear height of the dilute-phase zone 2 of the large-size furnace is Twice the length of the dense-phase zone of the small-sized furnace. The strengthened heating surface A in the furnace is arranged symmetrically on the front wall and the rear wall of the furnace, and 8 pieces are arranged symmetrically. It is greater than 15% of the net width of the dilute-phase zone of the large-scale furnace.

The dilute-phase zone 2 of the large-scale furnace is connected with the eccentric cyclone separator 4 through the separator inlet flue 3. There are 3 sets of eccentric cyclone separators 4 in total. Entering into the diversion flue 9, the center cylinder 8 of the separator is arranged eccentrically. In order to avoid the deposition of alkali metals and their oxides in the tail flue, an additional enhanced cooling heating surface C is provided in the diversion flue 9, which is a convection heating surface, through which the flue gas temperature can be reduced by more than 50°C.

The diverting flue 9 is connected with a longitudinal tail flue 10, and there is an ash hopper 11 at the bottom of the tail flue 10, and the tail flue heating surface B is arranged in the tail flue 10, and the cooled flue gas is finally discharged from the tail flue outlet 13 . After a small amount of dust gathers in the ash hopper 11, it is discharged from the ash hopper ash discharge port 12. The tail flue 10 is a large-volume tail flue, and its volume is more than 40 times the total volume of the heating surface B of the tail flue. At the same time, the heating surface B of the tail flue adopts a large intercept design, and its intercept is greater than 0.3m.

The temperature in the dense-phase zone 1 of the small-sized furnace and the dilute-phase zone 2 of the large-sized furnace is controlled between 650 and 850°C, and the airflow velocity is 4.5m/s. Since this temperature is lower than the optimum combustion temperature of the circulating fluidized bed boiler , so various means are used to ensure combustion efficiency. First, adopt the overall high-clean-height design of the boiler to ensure that the overall residence time of the particles is more than 5s; second, use the inert bed material addition system to regularly or supplement circulating ash as the bed material to reduce the residual carbon of the bed material and improve the utilization efficiency of the desulfurizer ; Third, use the method to improve the separation efficiency of the separator to more than 99.5%, and reduce the heat loss of incomplete combustion.

The fine particles of ash and slag are carried away by the flue gas, and some of them are regularly discharged from the slag discharge port 23 provided in the dense-phase zone 1 of the small-sized furnace and the alkali metal enriched ash discharge system 22 provided in the return device 6 . Due to the low combustion temperature, gaseous alkali metals and their compounds condensed and solidified in the fly ash, bottom slag and bed material can also be replaced and enriched and discharged through the slag outlet 23 and the alkali metal enriched ash discharge system 22 .

Because the alkali metal and its oxide will form a layer of attachment on the heating surface, and then bonded to the heating surface, as the running time prolongs, it will gradually thicken until it is blocked. For this reason, a flue gas along-process purging and cleaning system 20 is installed in the separator inlet flue 3, diverting flue 9, and tail flue 10. The flue gas along-course purging and cleaning system 20 mainly includes a soot blower , carry out enhanced soot blowing along the flue gas flow direction, steam and gas are selected as the soot blowing medium, and the arrangement density of soot blowers is 1.5 units per meter. In addition, there are soot cleaning holes around the flue gas blowing and cleaning system 20 , which can be supplemented by manpower in special cases. The ash hopper 11 and the ash hopper ash outlet 12 provided at the bottom of the tail flue 10 can regularly discharge the accumulated ash in the tail flue.

In order to reduce the concentration of NOX emissions, the boiler is also equipped with a denitrification reducing agent injection port 21, and continuously sprays urea aqueous solution as a denitrification agent during operation to perform flue gas denitrification.

Example 2:

A small boiler for steam supply, primarily fired with high alkali metal coal. In the dilute-phase zone 2 of the large-scale furnace, there are four screen-type heating surfaces A arranged on the front wall, and the intercept between each screen-type heating surface is 3m. A total of two eccentric cyclone separators 4 are provided.

The temperature of the dense-phase zone 1 of the small-scale furnace and the dilute-phase zone 2 of the large-scale furnace is controlled at 840°C, and the airflow velocity is 4.2m/s. No additional enhanced cooling heating surface C is provided in the diversion flue 9 .

The boiler is not equipped with an alkali metal enriched ash discharge system 2, and gaseous alkali metals and their compounds condensed and solidified in the fly ash, bottom slag and bed material are enriched and discharged through the slag discharge port 23.

The flue gas is blown along the soot cleaning system 20, the density of soot blowers is 1 per meter, and the soot blowing medium is steam.

Claims (8)

1. one kind uses the two low type boiler of high basic metal coal, comprise burner hearth, it is characterized in that, described burner hearth is divided into small size burner hearth emulsion zone (1) and is positioned at the large scale burner hearth dilute-phase zone (2) of small size burner hearth emulsion zone (1) top, small size burner hearth emulsion zone (1) connects coal supply system (18), large scale burner hearth dilute-phase zone (2) connects separator inlet flue (3), large scale burner hearth dilute-phase zone (2) adopts large volume, high clear height design, and the volume of large scale burner hearth dilute-phase zone (2) is more than 5 times of small size burner hearth emulsion zone (1) volume, the free height of described large scale burner hearth dilute-phase zone (2) is more than 2 times of small size burner hearth emulsion zone (1) length or more than 5 times of small size burner hearth emulsion zone (1) width, the operating temperature of small size burner hearth emulsion zone (1) and large scale burner hearth dilute-phase zone (2) controls between 650 ~ 850 DEG C, air current flow speed is 3 ~ 5m/s, the high basic metal coal time of staying is more than 5s.

2. the two low type boiler using high basic metal coal according to claim 1, is characterized in that, is provided with strengthening heating surface (A) in stove in described large scale burner hearth dilute-phase zone (2).

3. the two low type boiler using high basic metal coal according to claim 2, is characterized in that, the curtain wall that in described stove, strengthening heating surface (A) is arranged for multi-disc.

4. the two low type boiler using high basic metal coal according to claim 3, it is characterized in that, intercept between described curtain wall is greater than 0.5m, highly be greater than 60% of large scale burner hearth dilute-phase zone (2) free height, width is greater than 15% of large scale burner hearth dilute-phase zone (2) span width.

5. the two low type boiler using high basic metal coal according to claim 1, it is characterized in that, described small size burner hearth emulsion zone (1) is connected with material returning device (6) by feed back pipe (7), material returning device (6) connects the dust-exhausting port of eccentric cyclone separator (4) by standpipe (5), the ash-laden gas outlet of eccentric cyclone separator (4) connects large scale burner hearth dilute-phase zone (2) by separator inlet flue (3), clean flue gas after the dedusting of eccentric cyclone separator (4) is entered by central cylinder of separator (8) and turns to flue (9), flue (9) is turned to connect longitudinal back-end ductwork (10), back-end ductwork (10) bottom is provided with ash bucket (11).

6. the two low type boiler using high basic metal coal according to claim 5, is characterized in that, described in turn in flue (9) be provided with additional hardening cooling heating surface (C); Multiple parallel back-end ductwork heating surface (B) is provided with in described back-end ductwork (10), intercept between adjacent tail portions flue surface (B) is greater than 0.15m, and the volume of back-end ductwork (10) is more than 20 times of back-end ductwork heating surface (B) volume.

7. the two low type boiler using high basic metal coal according to claim 5, it is characterized in that, denitrification reducing agent entrance (21) is provided with in described separator inlet flue (3), described separator inlet flue (3), turn to and be provided with flue gas in flue (9) and back-end ductwork (10) and purge soot cleaning system (20) along journey, purge soot cleaning system (20) periphery at flue gas along journey and be provided with ash removing opening.

8. the two low type boiler using high basic metal coal according to claim 1, is characterized in that, described small size burner hearth emulsion zone (1):

Inert bed material add-on system (14) is connected by inert bed material adding tube (15);

Desulfurizing agent add-on system (16) is connected by desulfurizing agent adding tube (17);

Be provided with slag-drip opening (23).