Hearth structure of circulating fluidized bed boiler for purely burning furfural residues

Abstract

The utility model discloses a hearth structure of a circulating fluidized bed boiler for purely burning furfural residues, and solves the problems of how to ensure sufficient burning of burning materials and how to avoid smoke return and fire channeling phenomena when the furfural residues enter the hearth, and how to ensure that slag is easy to form on a heating surface in the hearth and how to avoid the occurrence of the phenomena of smoke return and fire channeling when the furfural residues enter the hearth. A secondary air lower annular air bellow (13) and a secondary air upper annular air bellow (14) are respectively arranged on the outer side wall of the hearth (2) at the dense-phase area (11); the air distribution quantity of a secondary air lower branch air pipe (15) is equal to that of the secondary air upper annular air bellow (14); the ratio of the secondary air distribution quantity to the primary air distribution quantity in the hearth is 55: 45; a furfural residue feeding port (17) is arranged on the outer side wall of the hearth (2) between the secondary air lower annular air bellow and the secondary air upper annular air bellow, the shrinkage ratio of the hearth on the dense-phase area (11) is 40%, and the pressure intensity at the furfural residue feeding port in the dense-phase area of the hearth is zero by setting the air inducing capacity of an induced draft fan (19).

Description

TECHNICAL FIELD

[0001] The present application relates to a circulating fluidized bed boiler, in particular to a hearth structure of a circulating fluidized bed boiler for burning furfural residue. BACKGROUND

[0002] Furfural residue is a kind of biomass material, which is a kind of biomass waste after furfural is extracted; acid, sulfur and chlorine components are left in the furfural residue, and it is rich in alkali metal, which has the characteristics of high moisture and low calorific value; how to treat the furfural residue in an environmentally friendly manner is a difficult problem that the relevant enterprises and environmental protection departments urgently need to solve at present; in the prior art, small-capacity chain furnaces are used to burn and treat furfural residue, but this treatment method has the defect that the treatment capacity of furfural residue is limited, and cannot meet the market demand for large-scale treatment of furfural residue; in addition, due to the characteristics of furfural residue, there is also a problem of easy slagging in the hearth; how to develop a circulating fluidized bed boiler suitable for burning furfural residue by means of flow state reconstruction, and cover the treatment capacity of furfural residue to 10-62 tons per hour (calculated at 45% moisture content), so as to realize large-scale digestion of furfural residue and produce steam from waste, and the steam pressure is 3.82-13.73 MPa, which has become a problem that needs to be solved on site.

[0003] Furfural residue has the characteristics of small particle size and light specific gravity, and when it is burned in the hearth, there is no large particle material to stabilize the bed pressure and bed temperature, and the proportion of suspended combustion in the upper part of the hearth is large; the conventional flow rate of 5 meters per second in the circulating fluidized bed hearth is completely not suitable for the combustion and heat transfer of furfural residue fuel; the alkali metal content of the fuel is high, the K2O content in the ash is about 15%, the fuel ash has a low melting point, and is easy to stick in the hearth, resulting in poor circulating fluidization of the fuel in the hearth; the primary air ratio of the conventional circulating fluidized bed boiler design is about 50-60%, the main role of the primary air is to ensure fluidization, and the main role of the secondary air is to enhance the mixing and combustion of the fuel, but for the circulating fluidized bed burning furfural residue, due to the small particle size and light specific gravity of furfural residue, there are few coarse particles in the lower part, and the proportion of upper combustion must be increased, how to design the ratio of primary and secondary air to meet the characteristics of furfural residue combustion needs to be explored and tested; in addition, in the process of conveying a large amount of furfural residue into the hearth, it is necessary to ensure the normal circulation and fluidization in the hearth, and at the same time, to avoid the phenomenon of back smoke and fire jumping of light furfural residue entering the hearth as much as possible, which is also a difficult problem that needs to be solved on site. SUMMARY

[0004] The present application provides a hearth structure of a circulating fluidized bed boiler for burning furfural residue, which solves the technical problems of how to ensure sufficient combustion of the fuel and prevent slagging of the heating surface in the hearth, and how to avoid the phenomenon of back smoke and fire jumping of furfural residue entering the hearth.

[0005] The present application solves the above technical problems by the following technical solutions:

[0006] The blast furnace of the present invention is to be provided with a blast furnace of the present invention, and the blast furnace of the present invention is provided with a blast furnace of the present invention. They are arranged parallel to each other and at intervals, the lower annular bellows of secondary air is connected to the dense phase zone through the lower branch duct of secondary air, and the upper annular bellows of secondary air is connected to the dense phase zone through the upper branch duct of secondary air, the air distribution volume of the lower branch duct of secondary air is equal to the air distribution volume of the upper annular bellows of secondary air; the ratio of the secondary air distribution volume to the primary air distribution volume in the furnace is 55:45; a furfural slag feeding port is provided on the outer wall of the furnace between the lower annular bellows of secondary air and the upper annular bellows of secondary air, the distance H2 between the furfural slag feeding port and the air distribution plate is 4.5 meters, the distance H1 between the inlet of the lower branch duct of secondary air on the furnace and the air distribution plate is 2.5 meters, and the distance H3 between the upper branch duct of secondary air and the air distribution plate is 5.5-6 meters; the contraction ratio of the furnace in the dense phase zone is 40%, and the height of the dense phase zone is 9-11 meters; by setting the induced draft capacity of the induced draft fan, the pressure at the furfural slag feeding port in the dense phase zone of the furnace is made 0.

[0007] The cross-sectional flue gas flow velocity in the furnace is 3.6-4.2 meters per second; the design temperature of the furnace is 740-780℃; dense pins are set in the dense phase area, and the dense pins are coated with a wear-resistant layer; an online bottom material adding system is set on the furnace to add coarser particle bottom material to the dense phase area of ​​the furnace.

[0008] An anti-corrosion coating is provided on the inner wall of the upper furnace in the dilute phase zone; a high-temperature superheating screen and a medium-temperature superheating screen are provided in the dilute phase zone; and a cyclone separator realizes the circulation of flue gas particles with a particle size greater than 50 microns.

[0009] The present application realizes sufficient combustion of a large amount of furfural residue, solves the problems that the back pressure of the furnace is high and the furfural residue is difficult to be fed into the furnace due to the too low furfural residue feeding port, and the lower part of the circulating fluidized bed has no combustible material due to the too high furfural residue feeding port, which is not conducive to combustion because the role of the coarse particles in the bed in stabilizing the bed temperature is lost; the secondary air of the present application is arranged in two layers, and a layer of secondary air is arranged above the feeding port, which can ensure that the gas quickly resolved after the furfural residue fuel is fed into the furnace can be completely combusted, in addition, because the position of the feeding port cannot be too low, the height from the air distribution plate is higher than that of the conventional coal-fired boiler, so a layer of secondary air needs to be arranged below the feeding port to ensure effective connection with the primary air, and the height of the lower inlet of the secondary air needs to be ensured to ensure the normal operation of the circulating combustion system; the present application increases the pressure head of the induced draft fan, creatively expands the negative pressure area in the furnace, and lowers the zero pressure area to the furfural residue feeding port, thereby completely solving the back smoke and fire flash phenomenon during the feeding of the furfural residue into the furnace. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a structural schematic diagram of the present application;

[0011] Figure 2 is a structural schematic diagram in the top view. DETAILED DESCRIPTION

[0012] The present application will be described in detail below in combination with the drawings:

[0013] The application discloses a furnace structure of a circulating fluidized bed boiler for pure furfural residue, which comprises a steel frame 1, a furnace 2 and a cyclone separator arranged on the steel frame 1 respectively, the furnace 2 is communicated with the upper cylinder 3 of the cyclone separator through the furnace upper outlet flue 4, the lower cone 5 of the cyclone separator is connected to the lower end of the upper cylinder 3, the separator center outlet cylinder 18 is arranged at the top end of the upper cylinder 3, the tail flue is connected to the other end of the separator center outlet cylinder 18, and the induced draft fan 19 is connected to the outlet of the tail flue; the water-cooled air chamber 7 is arranged at the lower end of the furnace 2, the air distribution plate 8 is arranged at the connecting position of the water-cooled air chamber 7 and the furnace 2, the primary air box 9 and the ignition device 10 are connected to the water-cooled air chamber 7, the lower part of the furnace 2 is the dense phase zone 11, and the upper part of the furnace 2 is the dilute phase zone 12; the secondary air lower annular air box 13 and the secondary air upper annular air box 14 are arranged on the outer side wall of the furnace 2 at the dense phase zone 11 respectively, the secondary air lower annular air box 13 and the secondary air upper annular air box 14 are parallel to each other and arranged at intervals, the secondary air lower annular air box 13 is communicated with the dense phase zone 11 through the secondary air lower branch air pipe 15, the secondary air upper annular air box 14 is communicated with the dense phase zone 11 through the secondary air upper branch air pipe 16, the air distribution amount of the secondary air lower branch air pipe 15 is equal to the air distribution amount of the secondary air upper annular air box 14, or the air distribution amount of the secondary air lower branch air pipe 15 is 51.2% of the total secondary air amount, and the air distribution amount of the secondary air upper branch air pipe 16 is 48.8% of the total secondary air amount, the air distribution mode of the secondary air in the furnace is a countermeasure designed according to the characteristics that the upper part of the furnace has a high combustion proportion of the furfural residue with a relatively light specific gravity, and can ensure that the gas quickly resolved after the fuel is put into the furnace can be completely combusted; the ratio of the secondary air distribution amount to the primary air distribution amount in the furnace is 55:45; the furfural residue feeding port 17 is arranged on the outer side wall of the furnace 2 between the secondary air lower annular air box 13 and the secondary air upper annular air box 14, the distance H2 between the furfural residue feeding port 17 and the air distribution plate 8 is 4.5 meters, the distance H1 between the inlet of the secondary air lower branch air pipe 15 on the furnace 2 and the air distribution plate 8 is 2.5 meters, and the distance H3 between the secondary air upper branch air pipe 16 and the air distribution plate 8 is 5.5-6 meters; the shrinkage ratio of the furnace 2 on the dense phase zone 11 is 40%, the ratio of the boiler bed cross section B1 to the furnace cross section B2 is 40:100, the height of the dense phase zone 11 is 9-11 meters, and the above indexes are all obtained through repeated field tests; the pressure at the furfural residue feeding port 17 in the dense phase zone 11 of the furnace 2 is 0 by setting the induced draft capacity of the induced draft fan 19, the smoke gas in the whole boiler system is mainly discharged by the induced draft of the induced draft fan 19 at the tail, the power of the existing circulating fluidized bed induced draft fan 19 is generally set at the top of the furnace based on the setting of the negative pressure zone at the upper outlet of the furnace, that is, 0 pressure, the negative pressure zone is enlarged and the 0 pressure zone is lowered to the furfural residue feeding port on the furnace, and the problem of the smoke returning to the feeding device and the fire backfiring phenomenon of the furfural residue with small particle size and light specific gravity into the furnace is creatively solved.

[0014] The cross-sectional flow velocity of the smoke gas in the furnace 2 is 3.6-4.2 meters per second; the design temperature of the furnace is 740-780 DEG C; dense pins are arranged in the dense phase zone 11, and the dense pins are coated with a wear-resistant layer; the high-temperature superheater and the medium-temperature superheater 20 are arranged in the furnace, and the pipe material is TP347H with better corrosion resistance; according to the characteristics of the fuel, the fly ash is easy to adhere to the heated surface pipe with a wall temperature of 500-600 DEG C to cause scale corrosion, the medium temperature of the high-temperature superheater is 540 DEG C, and the wall temperature is 550-580 DEG C, so the high-temperature superheater is arranged in the furnace, a large amount of wall-attached backflow material is used to wash the heated surface, and the problem of corrosion caused by dust adhesion is avoided. The arrangement solves the corrosion problem of the high-temperature heated surface.

[0015] A corrosion-resistant coating layer is arranged on the inner side wall of the upper furnace 2 of the dilute phase zone 12; the cyclone separator realizes the circulating fluidization of the smoke gas particles with a particle size greater than 50 microns, the furnace 2 is communicated with the upper cylinder 3 of the cyclone separator through the furnace upper outlet flue 4, the separator throat C of the furnace upper outlet flue 4 entering the upper cylinder 3 of the cyclone separator is narrowed, and the diameter QD of the upper cylinder 3 of the cyclone separator is increased, so that the velocity of the smoke gas carrying the circulating particles in the furnace 2 is increased from 3.6-4.2 meters per second to 30 meters per second when passing through the separator throat C, so that the ash particles entering the cyclone separator from the dilute phase zone 12 cannot escape from the center outlet cylinder 18, the efficiency of the separator is improved through the above effective means, the ability of the separator to capture fine particles is greatly improved, the bed quality in the furnace is ensured, and favorable conditions for the stability and environmental protection of the boiler are created, so that the residence time of the particles in the furnace is lengthened, which is beneficial to the burning of the fine furfural residue fuel. At the same time, the limestone desulfurization system is put into the furnace, which is beneficial to the effective utilization rate of limestone and improves the desulfurization efficiency in the furnace to control the SO2 emission at the outlet of the furnace.

[0016] For the existing circulating fluidized bed boiler, both fine particles and coarse particles are needed in the furnace to transfer heat and stabilize bed pressure and temperature. However, when using furfural residue as fuel, there are almost no coarse particles in the fuel. Therefore, a bottom material online adding system is set up in the furnace to add coarse bottom material to the dense phase zone of the furnace to ensure the stable and reliable operation of the boiler.

Claims

1. A furnace structure of a circulating fluidized bed boiler for pure pyrolysis of furfural residue, comprising a steel frame (1), a furnace (2) and a cyclone separator arranged on the steel frame (1) respectively, the furnace (2) and the upper cylinder (3) of the cyclone separator are communicated together through the furnace upper outlet flue (4), the lower cone (5) of the cyclone separator is connected at the lower end of the upper cylinder (3), the lower end of the lower cone (5) is communicated together with the furnace (2) through the return device (6), the separator center outlet cylinder (18) is arranged at the top end of the upper cylinder (3), the tail flue is connected at the other end of the separator center outlet cylinder (18), the induced draft fan (19) is connected at the outlet of the tail flue; the water-cooled air chamber (7) is arranged at the lower end of the furnace (2), the air distribution plate (8) is arranged at the connection between the water-cooled air chamber (7) and the furnace (2); the primary air box (9) and the ignition device (10) are connected on the water-cooled air chamber (7); the lower part of the furnace (2) is the dense phase zone (11), and the upper part of the furnace (2) is the dilute phase zone (12); characterized in that, The lower secondary air annular air box (13) and the upper secondary air annular air box (14) are parallel and spaced apart, the lower secondary air annular air box (13) is communicated with the dense phase zone (11) through the lower secondary air branch air pipe (15), the upper secondary air annular air box (14) is communicated with the dense phase zone (11) through the upper secondary air branch air pipe (16), and the air distribution amount of the lower secondary air branch air pipe (15) is equal to the air distribution amount of the upper secondary air annular air box (14); the ratio of the secondary air distribution amount to the primary air distribution amount in the furnace is 55:45; the furfural residue feeding port (17) is arranged on the outer side wall of the furnace (2) between the lower secondary air annular air box (13) and the upper secondary air annular air box (14), the distance H2 between the furfural residue feeding port (17) and the air distribution plate (8) is 4.5 meters, the distance H1 between the inlet of the lower secondary air branch air pipe (15) on the furnace (2) and the air distribution plate (8) is 2.5 meters, and the distance H3 between the upper secondary air branch air pipe (16) and the air distribution plate (8) is 5.5-6 meters; the contraction ratio of the furnace (2) on the dense phase zone (11) is 40%, and the height of the dense phase zone (11) is 9-11 meters; the pressure at the furfural residue feeding port (17) in the dense phase zone (11) of the furnace (2) is 0 by setting the induced draft capacity of the induced draft fan (19).

2. A furnace structure of a circulating fluidized bed boiler for pure pyrolysis of furfural residue according to claim 1, characterized in that, The cross-sectional smoke flow velocity in the furnace (2) is 3.6-4.2 meters per second; the furnace design temperature is 740-780 DEG C; dense pins are arranged in the dense phase zone (11), and the dense pins are coated with a wear-resistant layer; a bottom material online adding system is arranged on the furnace, and relatively coarse bottom material is added to the dense phase zone (11) of the furnace (2).

3. A furnace structure of a circulating fluidized bed boiler for pure pyrolysis of furfural residue according to claim 1 or 2, characterized in that, A corrosion-resistant coating layer is arranged on the inner side wall of the upper furnace (2) of the dilute phase zone (12); high-temperature and medium-temperature overheating screens (20) are arranged in the dilute phase zone (12); and the cyclone separator realizes the circulation of smoke particles with a particle size greater than 50 microns.

Images