CN112696694A - Bubbling fluidized bed sludge boiler and combustion process thereof - Google Patents

Bubbling fluidized bed sludge boiler and combustion process thereof Download PDF

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Publication number
CN112696694A
CN112696694A CN202110116031.3A CN202110116031A CN112696694A CN 112696694 A CN112696694 A CN 112696694A CN 202110116031 A CN202110116031 A CN 202110116031A CN 112696694 A CN112696694 A CN 112696694A
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hearth
temperature
boiler
fluidized bed
sludge
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Chinese (zh)
Inventor
袁伟胜
曾祥霖
戴晓晔
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Zhuhai Kechuang Environmental Resource Co ltd
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Zhuhai Kechuang Environmental Resource Co ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C10/00—Fluidised bed combustion apparatus
    • F23C10/18—Details; Accessories
    • F23C10/20—Inlets for fluidisation air, e.g. grids; Bottoms
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C10/00—Fluidised bed combustion apparatus
    • F23C10/18—Details; Accessories
    • F23C10/24—Devices for removal of material from the bed
    • F23C10/26—Devices for removal of material from the bed combined with devices for partial reintroduction of material into the bed, e.g. after separation of agglomerated parts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
    • F23G5/30—Incineration of waste; Incinerator constructions; Details, accessories or control therefor having a fluidised bed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
    • F23G5/44—Details; Accessories
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J15/00—Arrangements of devices for treating smoke or fumes
    • F23J15/06—Arrangements of devices for treating smoke or fumes of coolers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
    • F23L15/00—Heating of air supplied for combustion
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluidized-Bed Combustion And Resonant Combustion (AREA)

Abstract

A bubbling fluidized bed sludge boiler and a combustion process thereof are disclosed, wherein a high-temperature dust removal separator is additionally arranged between a flue gas outlet at the upper part of a hearth and a high-temperature superheater, and the inner wall of the hearth is fully covered by a composite heat-preservation refractory castable material; the lower part is provided with a transverse buried pipe; the effective volume of the steam per ton of the effective volume in the hearth divided by the tonnage of the boiler is designed to be 15m3The above. The combustion process of the present invention comprises: 1) by means of drumsPure sludge is combusted in a bubbling fluidized bed boiler; 2) controlling the flow velocity of the flue gas in the hearth to be 0.5-2 m/s; 3) the residence time of the flue gas in the hearth is above 10 s; 4) the temperature of the hearth is set to 850-950 ℃; 5) the effective volume of the steam per ton is designed to be 15m3The above; 6) a transverse buried pipe is arranged at the lower part of the hearth; 7) the heat exchange surface of the inner wall of the hearth is fully covered by adopting a composite heat-preservation refractory castable; 8) and when the temperature of the hearth is lower than 800 ℃, stopping returning the materials by the material returning device of the high-temperature dust removal separator. The bubbling fluidized bed sludge boiler and the combustion process thereof achieve rated load and ideal thermal efficiency; the emission of nitrogen oxides and carbon monoxide reaches the standard.

Description

Bubbling fluidized bed sludge boiler and combustion process thereof
The technical field is as follows:
the invention relates to the technical field of environmental protection, in particular to a bubbling fluidized bed sludge boiler and a combustion process thereof.
Background art:
in the technical field of environmental protection, sludge treatment is a technical problem which is difficult to solve so far, sludge combustion is difficult to realize, so that the sludge combustion of domestic boilers can only be operated by adopting a coal-doped combustion mode, and the sludge pure-combustion technology of the boilers still belongs to a technical blank to be filled.
The process of the boiler for burning the sludge comprises the following steps: after filter pressing, the sludge with 80 percent of water content has 50-60 percent of water content, then after drying, the water content is less than 40 percent or the sludge is directly filter-pressed to be below 40 percent by using advanced technology, and finally after crushing, the particles are less than 10mm and are sent into a hearth by a feeder; air is heated to a certain temperature through heat exchange of an air preheater and then enters a hearth through an air duct, an air distribution plate and an air cap; the sludge and the hot air are fully mixed and intensively combusted in the hearth, and the generated flue gas enters the tail flue through the outlet of the separator. The flue gas generates steam required by a user after heat exchange through the superheater and the economizer. And the flue gas after heat exchange is treated by an air preheater and the flue gas and then discharged into the atmosphere after reaching the standard.
For sludge with high moisture and low calorific value, in order to ensure stable combustion of a boiler, a certain temperature field needs to be kept in a hearth besides enough oxygen, and if the temperature is lower than the temperature field, the combustion is insufficient and even flameout is realized; if the temperature is higher than this temperature field, coking is likely to occur.
How to ensure that the temperature of the hearth is within the temperature field range is the core of the design of the sludge boiler.
The sludge has the common characteristics of high water content, fine particles and difficult burning out. Meanwhile, the sludge has different sources, different properties and different organic matter contents, so that the heating value of the sludge is different. Therefore, when the sludge boiler is designed, the sludge boiler needs to be distinguished from the common coal-fired boiler, and the boiler can not be carried and copied, but is designed according to the characteristics of fuel.
The invention content is as follows:
the technical problem to be solved by the invention is as follows: the problems existing in the background technology are solved, and the bubbling fluidized bed sludge boiler for pure sludge combustion and the combustion process thereof are provided, and the following 4 indexes are realized:
1. the rated load is reached;
2. ideal thermal efficiency is achieved;
3. the emission of nitrogen oxides reaches the standard;
4. the carbon monoxide emission reaches the standard.
The technical scheme adopted by the invention is as follows:
a bubbling fluidized bed sludge boiler, which comprises a hearth, an air distribution plate, an air cap, a blast chamber, a feeding hopper, a drum, a high-temperature dust removal separator and a high-temperature superheater, the high-temperature dust removal device comprises a low-temperature superheater, a high-temperature economizer, a low-temperature economizer and an air preheater, wherein an air distribution plate, an air cap and a blast chamber are arranged on the lower part of a hearth; the inner wall of the hearth is fully covered by a composite heat-preservation refractory castable; a transverse buried pipe is arranged at the lower part of the hearth; the effective volume of the steam per ton of the effective volume in the hearth divided by the tonnage of the boiler is designed to be 15m3The above.
Among the above-mentioned technical scheme, be equipped with furnace temperature sensor in furnace, install temperature control device and returning charge ware in high temperature dust removal separator's below, furnace temperature sensor's temperature signal output connects temperature control device, and temperature control device's control signal output connects and controls returning charge ware.
A combustion process of a bubbling fluidized bed sludge boiler comprises the following steps:
1) combusting sludge by adopting a bubbling fluidized bed boiler;
bubbling fluidized bed boilers are commonly called as boiling furnaces, also called as low-rate circulating fluidized beds, generally have buried pipes, the fluidizing speed is below 3.5m/s, and the bubbling fluidized bed boilers are generally called as bubbling beds because the flow speed is low, the dense-phase region is in a surge flow state and a large amount of bubbles are generated;
the corresponding circulating fluidized bed, also called high-speed bed, has the fluidizing velocity of the combustion zone above 6.5m/s, presents a gas conveying state and has no bubbles. The bubbling bed is fundamentally different from the fluidized bed in that whether bubbles are generated or not is the case when the fluidized bed is combusted;
the original bubbling bed has no separator, so the combustion efficiency is lower, the flow rate of the bubbling bed is low, the bed surface area is large, the furnace type cannot be enlarged, but after the separator is additionally arranged on the bubbling fluidized bed, the separated coarse particles can be returned to a hearth for continuous combustion, so that the combustion is more sufficient, the combustion efficiency and the thermal efficiency are improved, and the abrasion of a tail heating surface is also reduced.
2) When the bubbling fluidized bed boiler burns sludge, the flow velocity of the flue gas in the hearth is controlled to be 0.5-2 m/s;
the method is characterized in that the flow velocity of the flue gas on the cross section of the hearth is selected to be 0.5-2m/s for the purpose of fully burning and stably burning the sludge because the sludge particles are fine and the flow velocity of the flue gas is easily lifted out of the hearth if the flow velocity is too high; therefore, the residence time of the flue gas in the hearth is ensured, and fine particles returned to the hearth are not easy to be pumped out of a main combustion area, so that the primary burning of the sludge is facilitated, and the secondary combustion of the returned ash is facilitated;
3) when the bubbling fluidized bed boiler burns sludge, the retention time of flue gas in a hearth is above 10 s;
the reason is that the particles of the sludge after combustion are fine and light, so the separator is difficult to capture, and even if the sludge is repeatedly and circularly combusted, the ideal effect cannot be achieved, so that the fuel is burnt out once in the hearth, namely the retention time of the flue gas in the hearth is required to be ensured to be more than 10 s. The common circulating fluidized bed boiler has the retention time of only about 3s in the hearth due to the increase of the circulation multiplying power. So the combustion effect is greatly enhanced compared with the common furnace type, and the burnout rate is also improved;
4) setting the hearth temperature to 850-950 ℃ when the bubbling fluidized bed boiler burns sludge;
the reason is that if the temperature of the hearth is lower than 850 ℃, the combustion is insufficient, even the flame is easy to extinguish, and if the temperature of the hearth is higher than 950 ℃, the coking is easy to occur;
5) the volume between the central line of the small hole of the blast cap and the central line of the outlet of the hearth and the temperature of between 850 and 950 ℃ in the hearth is called effective volume, the effective volume is divided by the tonnage of the boiler and is called effective volume of the steam per ton, and the effective volume of the steam per ton of the bubbling fluidized bed boiler for burning the sludge is designed to be 15m3The above.
Thus, the sufficient retention time of the flue gas can be ensured; because the existing smoke retention time can be calculated only by a few professionals, according to an empirical formula for many years: if the smoke retention time is as long as the effective volume of the ton of steam is multiplied by 0.7, the effective volume proportion of the ton of steam is increased in a positive proportion.
6) For the sludge with the combustion calorific value of more than 1200kcal/kg, a transverse buried pipe is required to be arranged at the lower part of a hearth of the bubbling fluidized bed boiler;
for sludge with the combustion calorific value of less than 1200kcal/kg, an incinerator and waste heat boiler mode is generally adopted, and the mode is mature.
However, for the sludge with the combustion heating value of more than 1200kcal/kg, the mode of the incinerator and the waste heat is continuously adopted because the input heat is large, the economic benefit is not good, and the difficulty in flue gas treatment is large. Therefore, the lower part of the hearth of the bubbling fluidized bed boiler is required to be provided with a transverse buried pipe; without the buried pipe, the primary combustion zone would be over-heated, resulting in coking. And if the output capacity of the boiler is required to be ensured, the buried pipe is not arranged, and the water-cooled wall heating surface is arranged in the hearth, so that the temperature difference in the hearth is unstable, the combustion effect is poor, and even the boiler is flamed out.
Only the transverse buried pipe is arranged at the lower part of the hearth, and the temperature of the main combustion area of the bubbling fluidized bed is controlled by absorbing heat through the transverse buried pipe, so that the stable combustion of the boiler is ensured, and the load of the boiler is also ensured.
7) The heat exchange surface of the inner wall of the hearth is fully covered by adopting a composite heat-preservation refractory castable, and the whole hearth is constructed into a heat preservation area;
because the temperature of a hearth is guaranteed to be between 850 ℃ and 950 ℃ when sludge is combusted, but the hearth is provided with the transverse buried pipe, the temperature of a main combustion area absorbs a part of heat through the transverse buried pipe, and if the water-cooled wall of the hearth further absorbs the temperature in the hearth, the temperature in the hearth is too low, so that the combustion stability is influenced. In order to ensure that the combustion temperature is in the range, the technology needs to fully cover the heat exchange surface of the inner wall of the hearth, and the whole hearth is constructed into a heat preservation area. Except the heat exchange of the transverse buried pipe, other parts of the whole combustion process are similar to an adiabatic combustion process, so that a combustion temperature area is reasonable, and the fuel state is stable;
the bubbling fluidized bed boiler using sludge is characterized in that the effective volume of the steam per ton is 3 times that of the common fluidized bed boiler, and then the area of the outer wall is 3 times that of the common fluidized bed boiler. At present, a common fluidized bed only needs to be covered by a common refractory castable, and the water cooling degree of a covered membrane wall is 0.3, so that the temperature field of a hearth can be ensured to be reasonable. If the bubbling fluidized bed boiler of mud continues to adopt the pouring of the same degree, then the boiler will be because the area is too big, and the heat dissipation is serious to can't guarantee furnace temperature. Therefore, the technology needs to adopt the composite heat-preservation refractory castable to fully cover, so that the water cooling degree of the membrane wall is below 0.1. By the measures, the effect is superior to the heat preservation effect of a common fluidized bed boiler;
8) returning ash separated by the high-temperature dust removal separator to the hearth for burning again, and stopping returning materials by a material returning device of the high-temperature dust removal separator when the temperature of the hearth is lower than 800 ℃;
if the return ash in the combustion process is completely returned to the hearth, the temperature of the hearth is inevitably reduced due to the low temperature of the return ash, and the stability of sludge combustion is influenced, so the return ash in sludge incineration adopts the flexible return mode; because enough smoke retention time is reserved in the invention, the carbon content of the return ash can be controlled within a controllable range by the flexible return mode, and the excessive carbon content cannot be caused.
In the technical scheme, the corresponding relation of the sludge with the combustion heat value of more than 1200kcal/kg and the arrangement of the transverse buried pipe at the lower part of the hearth of the bubbling fluidized bed boiler is as follows:
Figure BDA0002920478160000051
Figure BDA0002920478160000061
in the technical scheme, the thermal conductivity coefficient of the composite heat-insulation refractory castable is less than or equal to 0.07W/(m.k), and the refractoriness is more than or equal to 1300 ℃.
In the technical scheme, the composite heat-insulating refractory castable comprises aggregate, powder, a bonding agent and an additive, wherein the aggregate accounts for about 70-80 percent and is Al-containing2O3Clay accounting for more than 85 percent, powder alumina-silicate fiber accounting for about 10 to 15 percent, refractory powder accounting for about 10 to 15 percent in the powder, and nano powder selected to play roles in filling aggregate gaps and improving construction easiness; the binding agent is a material for cementing refractory aggregate and powder and enabling the refractory castable to generate strength, the composite heat-preservation refractory castable selects the most advanced process coagulation binding mode, and selects organic binding agents, namely lignosulfonate and starch; the additive determines the performance of the casting material, and accounts for about 5 percent, and if kyanite is adopted and added reasonably and properly, the performance and the operability of the composition material can be improved.
In the technical scheme, the additive is rare earth rhenium and accounts for 0.01 percent.
Experimental data
The invention carries out pure sludge combustion test on 1 10t/h bubbling fluidized bed boiler in paper mills in Chenzhou Yizhu county, Hunan, and the test data are as follows:
Figure BDA0002920478160000071
Figure BDA0002920478160000072
the invention realizes the success of the bubbling fluidized bed boiler for burning pure sludge through the process method and the test, fills the blank of the domestic boiler for burning pure sludge, changes the high energy consumption method for the operation of mixing coal in the sludge for burning in the prior art, and realizes the following performance indexes through the test:
1. the rated load is ensured to be reached, and 10% overload capacity is achieved;
2. the heat efficiency is ensured to be more than 80 percent;
3. the original emission of nitrogen and oxygen gas is less than 100mg/Nm3；
4. The original emission of carbon monoxide is less than 80mg/Nm3。
Description of the drawings:
FIG. 1 is a schematic structural view of a bubbling fluidized bed sludge boiler according to the present invention.
The attached drawings are marked as follows:
1-hearth, 2-air distribution plate, 3-hood, 4-coal hopper, 5-horizontal buried pipe, 6-hearth temperature sensor, 7-temperature control device, 8-composite heat preservation refractory castable, 9-high temperature dust remover, 10-hearth upper pressure measuring point, 11-drum, 12-high temperature superheater, 13-low temperature superheater, 14-high temperature economizer, 15-low temperature economizer, 16-air preheater, 17-material returning device and 18-blast chamber.
The specific implementation mode is as follows:
referring to fig. 1, the bubbling fluidized bed sludge boiler of the invention comprises a hearth 1, an air distribution plate 2, an air cap 3, a blast chamber, a coal feeding hopper 4, a boiler barrel and a high-temperature dust removal componentThe device comprises a separator, a high-temperature superheater 12, a low-temperature superheater 13, a high-temperature economizer 14, a low-temperature economizer 15 and an air preheater 16, wherein an air distribution plate 2, an air cap 3 and a blast chamber are arranged at the lower part of a hearth, a coal feeding hopper 4 is arranged at the front part of the hearth 1, a drum 11 is arranged at the top of the hearth 1, one side of the high-temperature dedusting separator is communicated with a flue gas outlet at the upper part of the hearth, a top flue of the high-temperature dedusting separator is communicated with the high-temperature superheater 12, the low-temperature superheater 13, the high-temperature economizer 14, the low-temperature economizer 15 and the air preheater 16 are sequentially communicated, an air preheating air outlet pipeline of the air preheater 16 is communicated with the blast chamber at the; the inner wall of the hearth is fully covered by a composite heat-preservation refractory castable; a transverse buried pipe 5 is arranged at the lower part of the hearth 1; the effective volume of the steam per ton of the effective volume in the hearth 1 divided by the tonnage of the boiler is designed to be 15m3The above.
In the technical scheme, a hearth temperature sensor 6 is arranged in a hearth 1, a temperature control device 7 and a material returning device 17 are arranged below the high-temperature dust removal separator, the temperature signal output of the hearth temperature sensor 6 is connected with the temperature control device 7, and the control signal output of the temperature control device 7 is connected with and controls the material returning device 17.
The invention relates to a combustion process of a bubbling fluidized bed sludge boiler, which comprises the following steps:
1) combusting sludge by adopting a bubbling fluidized bed boiler;
2) when the bubbling fluidized bed boiler burns sludge, controlling the flow velocity of the flue gas in the hearth to be 0.5-2 m/s;
3) when the bubbling fluidized bed boiler burns sludge, the retention time of flue gas in a hearth is above 10 s;
4) setting the temperature of a hearth to 850-950 ℃ when the bubbling fluidized bed boiler burns sludge;
5) the volume between the central line of the small hole of the blast cap and the central line of the outlet of the hearth and the temperature between 850 ℃ and 950 ℃ in the hearth is called effective volume, the effective volume is divided by the tonnage of the boiler and is called effective volume of the steam ton, and the effective volume of the steam ton of the bubbling fluidized bed boiler for burning the sludge is designed to be 15m3The above;
6) for sludge with the combustion calorific value of more than 1200kcal/kg, a transverse buried pipe is required to be arranged at the lower part of a hearth of the bubbling fluidized bed boiler;
7) the heat exchange surface of the inner wall of the hearth is fully covered by adopting a composite heat-preservation refractory castable, and the whole hearth is constructed into a heat preservation area;
8) returning ash separated by the high-temperature dust removal separator to the hearth for burning again, and stopping returning materials by a material returning device of the high-temperature dust removal separator when the temperature of the hearth is lower than 800 ℃;
the following further illustrates embodiments of the invention:
1. the bubbling in the bubbling fluidized bed sludge boiler is specifically explained as follows:
bubbling beds, commonly known as ebullating furnaces and also known as low-rate circulating fluidized beds, are generally provided with buried pipes, the fluidization speed is below 3.5m/s, and the bubbling beds are generally called as the bubbling beds because of the low flow speed and the turbulent flow state in a dense-phase region and the large amount of bubbles.
The corresponding circulating fluidized bed, also called high-speed bed, has the fluidizing velocity of the combustion zone above 6.5m/s, presents a gas conveying state and has no bubbles. The fundamental difference between bubbling beds and fluidized beds is whether or not bubbles are generated during combustion.
The original bubbling bed has no separator, so the combustion efficiency is low, the flow rate of the bubbling bed is low, the bed surface area is large, and the furnace type cannot be enlarged. However, after the separator is additionally arranged on the bubbling fluidized bed, the separated coarse particles can be returned to the hearth for continuous combustion, so that the combustion is more sufficient, the combustion efficiency and the heat efficiency are improved, and the abrasion of a tail heating surface is also reduced.
2. The flow velocity of flue gas in the hearth specified by the invention is 0.5-2 m/s:
when the evaporation capacity of the boiler is determined, the required flue gas capacity of the boiler is determined accordingly. For example, the conventional steam is 1t/h, and the amount of flue gas required by a boiler furnace is about 1.43m3/S。
According to the formula: the flow rate of the flue gas is equal to the flow cross section area, so that the flow rate of the flue gas is constant when the evaporation capacity is constant, and designers mainly change the flow cross section area of the flue gas, namely the furnace sectional area of the boiler, so that the flow rate of the flue gas is changed. The larger the furnace sectional area is, the smaller the flue gas flow velocity is. On the contrary, the smaller the furnace sectional area is, the higher the flue gas flow velocity is.
The amount of air blown is the amount of oxygen sufficient to ensure combustion, and is related to the amount of fuel, i.e., is directly proportional to the amount of evaporation. The larger the evaporation amount, the larger the blast amount. The main material layer of wind pressure is related to the resistance of the hearth and the tail flue, and the blast volume is not related to the flow rate of flue gas.
3. The invention is how to realize the retention time of the flue gas in the hearth to be more than 10 s:
from the formula: the path is the velocity time, i.e. the residence time of the flue gas in the furnace is the height of the furnace/flue gas flow velocity. Therefore, when the height of the hearth is fixed, the residence time and the flue gas velocity have an inverse relation, and the higher the flue gas velocity is, the shorter the residence time is.
For high rate circulating fluidized beds, designers have attempted to increase the residence time of unburned particles in the furnace by increasing the circulation rate to recycle the captured fine particles. However, this has a limited effect on the sludge. The sludge has fine particles and low density, the main fuel is mainly volatile, and a large amount of ash separators cannot capture the main fuel. And if the flue gas flow velocity in the hearth is high, the elutriation is large, the ash returning to the hearth can be quickly carried away from the hearth and cannot participate in combustion. So that the effect of prolonging the residence time in the furnace is not achieved.
The bubbling fluidized bed sludge boiler can lead the retention time of the flue gas in the boiler to reach more than 10s by reducing the flow velocity of the flue gas, thereby realizing the one-time full combustion of the sludge. For example, a 40t/h boiler has a flue gas flow rate of 2m/s, a furnace height of 24m, flue gas and
the retention time of the unburned particles in the furnace can be more than 10 s.
The flow velocity of the furnace flue gas of the common circulating fluidized bed boiler is 5.5-6m/s, and the residence time of the flue gas is about 3-3.5 s.
4. The invention realizes the following specific implementation mode that the effective volume of the steam per ton is more than 15 cubic meters:
the effective volume of the steam per ton is more than 15 cubic meters, and the steam per ton is generally used in a furnaceBore height and cross-sectional area. Therefore, the hearth is required to be made high and large to realize low flue gas flow velocity and guarantee the effective volume of the hearth. For example, a 40t/h sludge boiler with an effective volume of 600m3The height of the hearth is 24m, and the cross section is 35 square meters.
5. The invention fully covers the existing hearth water-cooled wall with the composite heat-preservation fireproof sintering material:
the invention still adopts a boiler structure, so the water-cooled wall of the hearth still exists. But basically no longer undertakes the work of the heated surface, namely basically no heat exchange with the flue gas. Therefore, pouring materials with excellent performance and technological measures are needed to fully cover the interior of the hearth. Otherwise, the high and large furnace chamber can absorb and dissipate heat in a large amount, the temperature of the furnace chamber cannot be ensured, and the operation stability and the operation effect cannot be realized.
Three specific examples of furnaces are given below:
three examples of the bubbling fluidized bed sludge boiler of the invention burning 1500kcal/kg sludge:
Figure BDA0002920478160000111
three prior art high-speed fluidized bed project controls burning 4500kcal/kg lean coal:
Figure BDA0002920478160000112
Figure BDA0002920478160000121

Claims (6)

1. a bubbling fluidized bed sludge boiler comprises a hearth, an air distribution plate, an air cap, a blast chamber, a coal feeding hopper, a boiler barrel, a high-temperature dust removal separator, a high-temperature superheater, a low-temperature superheater, a high-temperature economizer, a low-temperature economizer and an air preheater, wherein the air distribution plate, the air cap and the blast chamber are arranged at the lower part of the hearth, the coal feeding hopper is arranged at the front part of the hearth,the boiler barrel is installed on the top of the hearth, the high-temperature superheater, the low-temperature superheater, the high-temperature economizer, the low-temperature economizer and the air preheater are sequentially connected and communicated, and the air preheating air outlet pipeline of the air preheater is connected and communicated with a blast chamber at the lower part of the hearth, and the boiler barrel is characterized in that: a high-temperature dust removal separator is additionally arranged between the flue gas outlet at the upper part of the hearth and the high-temperature superheater, one side of the high-temperature dust removal separator is communicated with the flue gas outlet at the upper part of the hearth, a top flue of the high-temperature dust removal separator is communicated with the high-temperature superheater, and the bottom end of the high-temperature dust removal separator is communicated with the lower part of the hearth; the inner wall of the hearth is fully covered by a composite heat-preservation refractory castable; a transverse buried pipe is arranged at the lower part of the hearth; the effective volume of the steam per ton of the effective volume in the hearth divided by the tonnage of the boiler is designed to be 15m3The above.
2. The bubbling fluidized bed sludge boiler of claim 1, wherein: a hearth temperature sensor is arranged in the hearth, a temperature control device and a material returning device are arranged below the high-temperature dust removal separator, the temperature signal output of the hearth temperature sensor is connected with the temperature control device, and the control signal output of the temperature control device is connected with and controls the material returning device.
3. A combustion process of a bubbling fluidized bed sludge boiler is characterized by comprising the following steps:
1) combusting sludge by adopting a bubbling fluidized bed boiler;
2) when the bubbling fluidized bed boiler burns sludge, controlling the flow velocity of the flue gas in the hearth to be 0.5-2 m/s;
3) when the bubbling fluidized bed boiler burns sludge, the retention time of flue gas in a hearth is above 10 s;
4) setting the temperature of a hearth to 850-950 ℃ when the bubbling fluidized bed boiler burns sludge;
5) the volume between the central line of the small hole of the blast cap and the central line of the outlet of the hearth and the temperature between 850 ℃ and 950 ℃ in the hearth is called effective volume, the effective volume is divided by the tonnage of the boiler and is called effective volume of the steam ton, and the effective volume of the steam ton of the bubbling fluidized bed boiler for burning the sludge is designed to be 15m3The above;
6) for sludge with the combustion calorific value of more than 1200kcal/kg, a transverse buried pipe is required to be arranged at the lower part of a hearth of the bubbling fluidized bed boiler;
7) the heat exchange surface of the inner wall of the hearth is fully covered by adopting a composite heat-preservation refractory castable, and the whole hearth is constructed into a heat preservation area;
8) returning the ash separated by the high-temperature dust-removing separator to the hearth for burning again, and stopping returning the material by a material returning device of the high-temperature dust-removing separator when the temperature of the hearth is lower than 800 ℃.
4. The combustion process of a bubbling fluidized bed sludge boiler as claimed in claim 3, characterized by comprising: the corresponding relation of the arrangement of the transverse buried pipes at the lower part of the hearth of the bubbling fluidized bed boiler for burning the sludge with the calorific value of more than 1200kcal/kg is as follows:
Figure FDA0002920478150000021
5. the combustion process of a bubbling fluidized bed sludge boiler as claimed in claim 3, wherein: the heat conductivity coefficient of the composite heat-preservation refractory castable is less than or equal to 0.07W/(m.k), and the refractoriness is more than or equal to 1300 ℃.
6. The combustion process of a bubbling fluidized bed sludge boiler as claimed in claim 3, wherein: the composite heat-insulating refractory castable comprises aggregate, powder, a bonding agent and an additive, wherein the aggregate accounts for about 70-80 percent and is Al-containing2O3Clay accounting for more than 85 percent, powder alumina-silicate fiber accounting for about 10 to 15 percent, powder refractory powder accounting for about 10 to 15 percent, and nano powder selected to play roles in filling aggregate gaps and improving construction easiness; the binding agent is cemented refractory aggregate and powder, and the composite heat-preservation refractory casting material which enables the refractory casting material to generate strength adopts the most advanced process coagulation binding mode and selects organic binding agents, namely lignosulfonate and starch; the additive determines the performance of the casting materialAbout 5 percent, adopts kyanite, reasonably and properly adds the kyanite to improve the performance and the operability of the composition material, and the additive is rare earth rhenium accounting for 0.01 percent.
CN202110116031.3A 2021-01-28 2021-01-28 Bubbling fluidized bed sludge boiler and combustion process thereof Pending CN112696694A (en)

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CN202110116031.3A CN112696694A (en) 2021-01-28 2021-01-28 Bubbling fluidized bed sludge boiler and combustion process thereof

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Application Number Priority Date Filing Date Title
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CN112696694A true CN112696694A (en) 2021-04-23

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Country Link
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