CN111174209A

CN111174209A - High-temperature waste incineration furnace grate system based on material circulation and working method

Info

Publication number: CN111174209A
Application number: CN202010113205.6A
Authority: CN
Inventors: 袁野; 肖平; 高洪培; 时正海; 王海涛; 孙献斌
Original assignee: Huaneng Clean Energy Research Institute
Current assignee: Huaneng Clean Energy Research Institute
Priority date: 2020-02-24
Filing date: 2020-02-24
Publication date: 2020-05-19

Abstract

The invention discloses a high-temperature waste incineration furnace grate system based on material circulation and a working method, and belongs to the technical field of waste incineration and clean combustion. Comprises a grate furnace, a primary air fan, a primary air steam preheater, an air preheater, an economizer, a flue gas treatment system, a chimney, a conveying fluidized fan and a separator; the fine sand material is added in the grate furnace and used as a heat carrying medium, so that the internal combustion of the grate furnace is enhanced, the uniformity of the temperature in the whole furnace is improved, and the formation of a concentrated high-temperature area is avoided. Meanwhile, the primary air is heated by the steam heater and the air preheater, so that the combustion intensity in the grate furnace is further improved, local low-temperature areas are reduced, and the emission of harmful substances is effectively reduced.

Description

High-temperature waste incineration furnace grate system based on material circulation and working method

Technical Field

The invention belongs to the technical field of waste incineration and clean combustion, and particularly relates to a high-temperature waste incineration furnace grate system based on material circulation and a working method.

Background

The national domestic garbage clearing and transporting amount in 2016 is about 21500.5 ten thousand tons. A large amount of solid wastes bring great harm to the environment, which is mainly manifested by land invasion, pollution to the atmosphere, soil and water, and difficult recovery of the caused harm. At present, although the proportion of waste incineration treatment in China is rapidly improved, because the classification of waste sources in China is not effectively carried out, smoke dust, fly ash and slag are generated in the combustion process, and a large amount of dioxin and heavy metal elements are contained in the fly ash. These pollutants are extremely harmful to the atmosphere, soil, sea and freshwater ecosystems, especially they can also be bio-concentrated through the food chain, eventually creating environmental problems. After the garbage is incinerated, the final products are discharged smoke, fly ash and incineration residues. The incineration ash is generally divided into two types, bottom ash and fly ash, and the bottom ash generally comprises furnace slag and grate ash. The bottom ash accounts for about 80 percent of the total amount of the ash, and mainly comprises slag, black and nonferrous metals, ceramic fragments, glass, other incombustibles and unburned organic matters. The fly ash is residue collected in a flue gas purification system and a heat recovery and utilization system, and accounts for about 20 percent of the total amount of ash.

The domestic garbage is easy to generate secondary pollution in the incineration process, and the fly ash is a main carrier of the secondary pollution. Since the fly ash contains various harmful heavy metal substances and salts such as Cd, Pb, Cu, Zn and Cr which can be leached by water, and high-concentration dioxin organic pollutants with the strongest toxicity are also enriched, the national hazardous waste records clearly stipulate that the household garbage incineration fly ash is hazardous waste, namely the number of the household garbage incineration fly ash is HW18, and the fly ash must be treated strictly according to the standard of the hazardous waste. The control technology of special pollutants such as heavy metal, dioxin and the like is mainly divided into control before incineration, control during incineration and control after incineration. Before incineration, the control mainly comprises the steps of enhancing pretreatment (garbage classification and sorting) of the garbage, adding special additives and reducing generation of heavy metals and dioxin in the garbage incineration process. The control in incineration is mainly started from two aspects: on one hand, the temperature distribution, the combustion atmosphere and the residence time are controlled through a reasonable combustion structure, so that heavy metals stay in bottom slag or fly ash as much as possible, and subsequent ash treatment is facilitated. On the other hand, a more effective adsorbent is developed, and a proper adsorption temperature interval is selected for removing the heavy metal adsorbent. After incineration, the control is mainly to carry out relevant treatment on the fly ash containing more harmful substances so as to reduce the harmless degree of the fly ash. The control technology after incineration is various, and mainly comprises a solidification and stabilization treatment technology, a chemical treatment technology and a heat treatment technology. Compared with the control technology before and after incineration, if the generation of special pollutants can be reduced in the incineration process, the subsequent treatment cost can be greatly reduced, and the investment and the operating pressure of treatment equipment are reduced.

Patent document No. CN107191941A discloses a process and a system for incinerating domestic garbage to reduce the pollutants in the incineration flue gas, which comprises transferring the domestic garbage into a garbage incinerator for primary combustion, adding petroleum coke and calcium carbonate into the garbage incinerator, and performing secondary combustion on the flue gas generated by the primary combustion and the odor generated during the storage of the domestic garbage. The system requires secondary combustion, the treatment system is complex, and the operating cost is high. Patent document No. CN101029727A discloses a cyclone melting furnace for refuse incineration fly ash. The corresponding garbage is preheated, dried and ignited under the action of high-temperature air in the primary air box, so that the high-temperature combustion process of the garbage is completed. The system does not relate to a specific scheme corresponding to high-temperature air heating and the relation between the overall combustion temperature and the resultant heavy metal and dioxin.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a high-temperature waste incineration grate furnace system based on material circulation and a working method thereof, so that the internal combustion of the grate furnace is enhanced, the uniformity of the temperature in the whole furnace is improved, the formation of a concentrated high-temperature area is avoided, and the emission of harmful substances is effectively reduced.

The invention is realized by the following technical scheme:

the invention discloses a high-temperature waste incineration furnace grate system based on material circulation, which comprises a grate furnace, a primary fan, a primary air steam preheater, an air preheater, an economizer, a flue gas treatment system, a chimney, a conveying fluidized fan and a sorting machine, wherein the primary air steam preheater is arranged on the grate furnace;

the primary air fan is connected with the primary air steam preheater, the primary air steam preheater is connected with the air inlet of the air preheater, and the air outlet of the air preheater is connected with the primary air inlet of the grate furnace; a sand material feeding port is formed in a hearth of the grate furnace, and a heated surface at the tail of the grate furnace is communicated with a sorting machine through a slag falling pipe; a light material outlet and a conveying fluidization fan of the separator are connected with a sand material feeding port through a fine sand material conveying pipe for conveying fine sand materials; a heavy material outlet of the separator is connected with a slag discharge pipe; the smoke outlet of the tail heating surface is connected with the smoke inlet of the air preheater, and the smoke outlet of the air preheater is sequentially connected with the economizer, the smoke treatment system and the chimney.

Preferably, the sand material inlet is arranged above the drying section of the fire grate.

Preferably, the classifier is a fluidized classifier, and the classifier is connected with a conveying fluidized fan.

Preferably, the fine sand material is quartz sand, river sand or coal ash, and the particle size of the fine sand material is less than 10 mm.

Preferably, a quick discharging and detaching device is arranged at the bent pipe of the fine sand conveying pipe.

Preferably, the fine sand conveying pipe is provided with a plurality of air supply branch pipes.

The invention discloses a working method of a high-temperature waste incineration furnace grate system based on material circulation, which comprises the following steps:

fine sand materials enter a grate furnace through a sand material feeding port, then enter a tail heating surface along with flue gas, fall into a separator through a slag falling pipe under the action of gravity, are separated by the separator, and the fine sand materials with low density and light weight enter a fine sand material conveying pipe through a light material outlet and are conveyed to the sand material feeding port by a conveying fluidized fan to continue the next round of circulation; the slag with high density and heavy weight enters a slag discharge pipe from a heavy material outlet to be discharged out of the system;

burning the garbage in a grate furnace, enabling the generated flue gas to sequentially flow through an air preheater and a coal economizer from a tail heating surface, cooling, then entering a flue gas treatment system, and discharging the treated flue gas out of the system through a chimney; the primary air enters the primary air steam preheater through the primary air fan, is heated, then enters the air preheater, is continuously heated, and enters the grate furnace through the primary air inlet.

Preferably, the temperature of the primary air is raised to 190-210 ℃ in the primary air steam preheater.

Preferably, the temperature of the primary air is raised to 300-400 ℃ in the air preheater.

Preferably, the temperature of the flue gas discharged by the economizer is 180-200 ℃.

Compared with the prior art, the invention has the following beneficial technical effects:

according to the high-temperature waste incineration grate furnace system based on material circulation, fine sand materials are added into the grate furnace to serve as heat carrying media, so that internal combustion of the grate furnace is enhanced, the uniformity of temperature in the whole furnace is improved, and a concentrated high-temperature area is avoided. Meanwhile, the primary air is heated by the steam heater and the air preheater, so that the combustion intensity in the grate furnace is further improved, a local low-temperature area is reduced, and the decomposition rate of harmful substances is improved.

The combustion temperature is crucial for the migration of heavy metals and the formation of dioxins, and heavy metals are classified into three categories according to volatility: non-volatile elements, semi-volatile elements and volatile elements. Nonvolatile elements such as Mn, Ni, Cu, Cr and the like are mainly distributed in low slag after being burnt; semi-volatile elements such As Cd, Pb, Zn, As and the like are partially or completely gasified in the incineration process, and physical changes such As nucleation, heterogeneous condensation and the like occur in the subsequent cooling process, and finally the semi-volatile elements are enriched on fine particles and fired to form heavy metal fine particles which are not easy to be captured by a dust remover; volatile elements such as Hg and Se are easily gasified during incineration and are mainly discharged into the atmosphere in a gaseous state. The volatilization release rate of metal can be greatly improved by increasing the incineration temperature, certain heavy metal can be promoted to be separated out like gas phase by increasing the combustion temperature, nano-to micron-grade particles are formed in the condensation process, and the particles can be collected in the dust removal and desulfurization processes. In general, researchers believe that PCDD/Fs (dioxins) are formed by two mechanisms. One is from homogeneous reaction and the temperature range is 500-800 ℃. The main process is the rearrangement of the chlorinated precursors, such as Chlorophenol (CP) and chlorobenzene (CBz). The PCDD/Fs in this process is called homogeneous PCDD/Fs or high-temperature PCDD/Fs. The PCDD/Fs can also form a reaction through a heterogeneous reaction, and the temperature range is 200-400 ℃. Heterogeneous reactions are mainly formed by CP, CBz, or carbon in fly ash, i.e. de novo process (source generation), under the catalytic action in fly ash. For different dioxin generation mechanisms, the dioxin in the fly ash is thoroughly decomposed and destroyed in a high-temperature environment, so that the aim of reducing the dioxin is fulfilled. Research results show that when the combustion temperature is higher than 1200 ℃, the decomposition rate of dioxin can be obviously improved. The decomposition characteristics of the conditions such as temperature and atmosphere on the fly ash melting process show that the higher the melting temperature, the higher the decomposition rate, and the higher the oxidative atmosphere decomposition rate than the inert atmosphere.

Therefore, the fine sand circulation and the primary air temperature increase of the invention can strengthen the internal combustion of the grate furnace, improve the uniformity of the temperature in the whole furnace, avoid the formation of a concentrated high-temperature area, reduce a local low-temperature area, have long retention time when the material is in the high-temperature area, obviously improve the dioxin decomposition rate when the combustion temperature is increased to 1100-1200 ℃, and simultaneously, heavy metals enter fly ash to be trapped by subsequent pollutant removal equipment through the processes of separation, nucleation and agglomeration, so the discharged flue gas can more easily reach the discharge standard.

Furthermore, the sand material feeding port is arranged above the drying section of the fire grate, the feeding is not influenced by the position of the inlet, and meanwhile, fine sand materials are easy to roll along with the fire grate to fill the whole hearth, so that the aim of enabling the temperature distribution to be more uniform is fulfilled.

Furthermore, the fluidized separator is selected as the separator, so that fine sand materials with small and light density and slag materials with large and heavy density can be effectively separated, and the efficiency is high.

Furthermore, quartz sand, river sand or coal ash residue have strong heat storage capacity and low cost, the particle size of the fine sand material is less than 10mm, on one hand, the fine sand material is easy to heat and store heat, and meanwhile, the small particle size of the fine sand material also ensures that the fine sand material can be carried by flue gas and cannot be accumulated on the surface of the fire grate.

Furthermore, because the local resistance of the elbow is large, the speed of fluidized fine sand is reduced at the elbow, the energy is reduced, the blockage is easily caused, and the quick discharging and detaching device is arranged at the elbow of the fine sand conveying pipe, so that the elbow can be conveniently treated, and the maintenance is convenient.

Furthermore, a plurality of air supply branch pipes are arranged on the fine sand conveying pipe, so that the blockage caused by bridging can be effectively reduced, the efficiency and distance of fine sand conveying are improved, and the reliability and stability of the system are improved.

The working method of the high-temperature waste incineration grate furnace system based on material circulation disclosed by the invention strengthens the internal combustion of the grate furnace, improves the uniformity of the temperature in the whole furnace, avoids the formation of a concentrated high-temperature area, and effectively reduces the emission of harmful substances.

Further, the temperature of primary air is increased to 190-210 ℃ in the primary air steam preheater, and if the temperature is continuously increased, the required steam quantity is too large, the steam temperature is too high, and the system operation is influenced.

Further, primary air is heated to 300-400 ℃ in an air preheater, and the smoke temperature is too high, so that great smoke exhaust loss is brought.

Further, due to the fact that the flue gas temperature is 10-20 ℃ higher than the acid dew point in the semi-dry desulfurization method adopted by most of the existing garbage grate furnaces, and meanwhile corrosion is considered, the flue gas temperature cannot be too low, and therefore the flue gas temperature discharged by the economizer is set to be 180-200 ℃.

Drawings

FIG. 1 is a schematic diagram of the system configuration and process flow of the present invention;

in the figure: 1-primary air fan, 2-primary air steam preheater, 3-air preheater, 4-economizer, 5-flue gas treatment system, 6-chimney, 7-tail heating surface, 8-hearth, 9-conveying fluidized fan, 10-fine sand conveying pipe, 11-sorting machine, 12-slag falling pipe and 13-sand material feeding port.

Detailed Description

The invention will now be described in further detail with reference to the following drawings and specific examples, which are intended to be illustrative and not limiting:

the invention relates to a high-temperature waste incineration furnace grate system based on material circulation, which comprises a furnace grate, a primary air fan 1, a primary air steam preheater 2, an air preheater 3, an economizer 4, a flue gas treatment system 5, a chimney 6, a conveying fluidization fan 9 and a sorting machine 11, wherein the primary air steam preheater 2 is arranged on the furnace grate;

the primary air fan 1 is connected with the primary air steam preheater 2, the primary air steam preheater 2 is connected with the air inlet of the air preheater 3, and the air outlet of the air preheater 3 is connected with the primary air inlet of the grate furnace; the hearth 8 of the grate furnace is provided with a sand material inlet 13, and the sand material inlet 13 can be arranged above the drying section of the grate. A heated surface 7 (comprising a primary evaporator, a high-temperature superheater, a medium-temperature superheater, a low-temperature superheater, a secondary evaporator and the like) at the tail part of the grate furnace is communicated with a separator 11 through a slag falling pipe 12;

a light material outlet of the separator 11 and a conveying fluidized fan 9 are connected with a sand material feeding port 13 through a fine sand material conveying pipe 10 for conveying fine sand materials; a heavy material outlet of the separator 11 is connected with a slag discharge pipe; the classifier 11 can be a fluidized classifier, the classifier 11 is connected with the conveying fluidized fan 9, and the conveying fluidized fan 9 can provide fluidized airflow for the classifier 11. The fine sand material can be selected from quartz sand, river sand or coal ash with the grain diameter less than 10mm, a quick discharging and detaching device can be arranged at the bent pipe of the fine sand material conveying pipe 10, and a straight pipe section with an excessively long length can be arranged as appropriate, so that the fine sand material conveying pipe is convenient to overhaul and maintain in the blockage process. Considering the on-way resistance of the straight pipe section and the local resistance of the bent pipe section, the fine sand conveying pipe 10 is provided with a plurality of air supply branch pipes to prevent blockage caused by bridging.

The flue gas outlet of the tail heating surface 7 is connected with the flue gas inlet of the air preheater 3, and the flue gas outlet of the air preheater 3 is sequentially connected with the economizer 4, the flue gas treatment system 5 (comprising a semi-dry desulfurization reaction tower, a dust remover, a low-temperature SCR system, wet desulfurization and the like) and the chimney 6.

The working principle and the working flow of the high-temperature waste incineration furnace grate system based on material circulation are explained as follows:

the garbage is placed in a grate furnace for incineration, the generated flue gas enters a tail heating surface 7 after passing through a hearth 8 of the grate furnace, enters an air preheater 3 and an economizer 4 after being cooled, then enters a subsequent flue gas purification system 5, and is discharged into a chimney 6 through a draught fan after being treated. The primary air firstly enters a primary air steam preheater 2 through a primary fan 1, the primary air can be heated to about 200 ℃ by utilizing steam generally, and if the temperature is continuously increased, the required steam amount is too large, the steam temperature is too high, and the system operation is influenced. And then, the primary air heated by steam further enters an air preheater 3 arranged behind a tail heating surface 7, the air preheater 3 is designed by adopting a compact and high heat exchange coefficient due to the limitation of the space of a flue at the tail of the grate furnace, and the primary air heater is heated by the air preheater 3 at 300-400 ℃. The high-temperature primary air after secondary heating is introduced into the fire grate from the lower part of the fire grate to be combusted. Theoretically, the combustion temperature can be increased by 70-80 ℃ every time the primary air is increased by 100 ℃. Therefore, the combustion temperature of the grate furnace hearth 8 can reach 1100-1200 ℃. Meanwhile, after the temperature of primary air is integrally increased, the garbage fuel is easier to dry, the integral combustion strength is improved, the combustion on the upper part of the grate is more uniform, the local low-temperature area is reduced, and the possibility of decomposition of dioxin is further improved. In addition, the flue gas temperature is required to be 10-20 ℃ higher than the acid dew point by adopting the semi-dry desulfurization method adopted by most of the existing garbage grate furnaces, and meanwhile, corrosion is considered, so the flue gas temperature cannot be too low, the heat exchange area of the economizer 4 is reduced, and the flue gas temperature can be kept about 190 ℃. If other flue gas treatment systems 5 are adopted, the corresponding heating surface design can be changed correspondingly.

Meanwhile, fine sand materials are added into the furnace grate through the sand material feeding port 13 and enter the tail flue 7 along with flue gas to form material circulation to serve as a heat carrying medium, so that the upper temperature and the lower temperature of the hearth are balanced, the integral combustion strength of the boiler is improved, the combustion concentration on the furnace grate is avoided, the regional temperature is greatly increased, and the coking possibility is reduced. The fine sand material enters the tail heating surface 7 along with the flue gas, falls into the slag falling pipe 12 under the action of gravity, enters the separator 11, takes fine particles as heavy materials, and forms a gas-solid suspension body with certain density under the action of uniform ascending air flow, and the gas-solid suspension body has the property similar to fluid. When the particles enter the separator 11, they will be layered under the action of the buoyancy and gravity of the average density of the bed, and if the density of the particles is higher than the average density of the bed, the particles will sink, otherwise they will float. Therefore, the fine sand with small density and light weight floats on the surface of the bed layer due to the buoyancy, is guided out from the upper layer of the separator 11, falls into the fine sand conveying pipe 10 and returns to the hearth 8. The great heavier slag charge of density sinks in the bed bottom, is derived by sorter 11 lower floor, gets into the scum pipe, and then has formed the material circulation of fine sand material, and the better heat on having passed the grate has promoted the whole burning intensity of grate furnace for temperature distribution is more even.

It should be noted that the above description is only one embodiment of the present invention, and all equivalent changes of the system described in the present invention are included in the protection scope of the present invention. Persons skilled in the art to which this invention pertains may substitute similar alternatives for the specific embodiments described, without departing from the scope of the invention as defined by the claims.

Claims

1. A high-temperature waste incineration furnace grate system based on material circulation is characterized by comprising a grate furnace, a primary fan (1), a primary air steam preheater (2), an air preheater (3), an economizer (4), a flue gas treatment system (5), a chimney (6), a conveying fluidized fan (9) and a separator (11);

the primary air fan (1) is connected with the primary air steam preheater (2), the primary air steam preheater (2) is connected with the air inlet of the air preheater (3), and the air outlet of the air preheater (3) is connected with the primary air inlet of the grate furnace; a sand material feeding port (13) is formed in a hearth (8) of the grate furnace, and a tail heating surface (7) of the grate furnace is communicated with a separator (11) through a slag falling pipe (12); a light material outlet of the separator (11) and a conveying fluidization fan (9) are connected with a sand material feeding port (13) through a fine sand material conveying pipe (10) for conveying fine sand materials; a heavy material outlet of the separator (11) is connected with a slag discharge pipe; the smoke outlet of the tail heating surface (7) is connected with the smoke inlet of the air preheater (3), and the smoke outlet of the air preheater (3) is sequentially connected with the economizer (4), the smoke treatment system (5) and the chimney (6).

2. The high-temperature waste incineration furnace grate system based on material circulation as claimed in claim 1, wherein the sand material inlet (13) is arranged above the drying section of the grate.

3. The high-temperature waste incineration furnace system based on material circulation as claimed in claim 1, characterized in that the separator (11) is a fluidized separator, and the separator (11) is connected with a conveying fluidized fan (9).

4. The high temperature waste incineration furnace grate system based on material circulation of claim 1, wherein the fine sand material is quartz sand, river sand or coal ash, and the particle size of the fine sand material is less than 10 mm.

5. The high-temperature waste incineration furnace grate system based on material circulation as claimed in claim 1, wherein a fast discharging and detaching device is arranged at the elbow of the fine sand conveying pipe (10).

6. The high-temperature waste incineration furnace grate system based on material circulation as claimed in claim 1, wherein the fine sand conveying pipe (10) is provided with a plurality of air supply branch pipes.

7. A working method of a high-temperature waste incineration furnace grate system based on material circulation is characterized by comprising the following steps:

fine sand materials enter a grate furnace through a sand material feeding port (13), then enter a tail heating surface (7) along with flue gas, fall into a separator (11) through a slag falling pipe (12) under the action of gravity, are separated by the separator (11), enter a fine sand material conveying pipe (10) through a light material outlet, are conveyed to the sand material feeding port (13) through a conveying fluidization fan (9), and continue to circulate for the next round; the slag with high density and heavy weight enters a slag discharge pipe from a heavy material outlet to be discharged out of the system;

the garbage is burned in a grate furnace, the generated flue gas flows through an air preheater (3) and an economizer (4) from a tail heating surface (7) in sequence, enters a flue gas treatment system (5) after being cooled, and is discharged out of the system through a chimney (6) after being treated; the primary air enters the primary air steam preheater (2) through the primary fan (1) to be heated, then enters the air preheater (3) to be continuously heated, and enters the grate furnace through the primary air inlet.

8. The clean combustion process of the high-temperature waste incineration furnace grate system based on the material circulation as claimed in claim 7, wherein the temperature of primary air in the primary air steam preheater (2) is raised to 190-210 ℃.

9. The clean combustion process of the high-temperature waste incineration furnace grate system based on the material circulation as claimed in claim 7, wherein the temperature of primary air in the air preheater (3) is raised to 300-400 ℃.

10. The clean combustion process of the high-temperature waste incineration furnace grate system based on the material circulation as claimed in claim 7, wherein the temperature of the flue gas discharged by the economizer (4) is 180-200 ℃.