CN112050243A

CN112050243A - Process for generating power by coupling sludge drying and incineration through middle storage type pulverizing system

Info

Publication number: CN112050243A
Application number: CN202010976193.XA
Authority: CN
Inventors: 王慧青; 查琼亮; 赵永坚; 冯斌
Original assignee: Xian Thermal Power Research Institute Co Ltd
Current assignee: Xian Thermal Power Research Institute Co Ltd
Priority date: 2020-09-16
Filing date: 2020-09-16
Publication date: 2020-12-08

Abstract

The invention discloses a process for generating power by coupling sludge drying and incineration through a middle storage type powder making system. According to the invention, the furnace smoke extraction pipe is additionally arranged, hot smoke at the bottom of the hearth is extracted to enter the steel ball coal mill, the drying capacity of the powder preparation system is improved, the sludge can be fully dried, and the humidity-carrying exhaust gas finally enters the hearth through the tertiary air nozzle, so that staged combustion is realized, and the NOx emission is reduced. The hot flue gas that the smoke tube of taking out the stove extracted can form inert atmosphere in the powder process system to improve the adaptability of powder process system to mixing mud volatile, reduced explosion-proof risk.

Description

Process for generating power by coupling sludge drying and incineration through middle storage type pulverizing system

Technical Field

The invention belongs to the technical field of coal-fired coupled sludge power generation, and particularly relates to a process for generating power by coupling a middle storage pulverizing system with sludge drying and incineration.

Background

Along with the rapid improvement of the urbanization rate and the urbanization level in China, the urban sewage treatment capacity in China is continuously improved. By 2016, the total amount of national wastewater discharge is 711.10 hundred million t, the domestic sewage discharge accounts for 71.4 percent, and only 31 main urban domestic sewage discharge reaches 176.81 million. The urban domestic sewage treatment rate is 93.44%, and the sludge yield of main cities in China is about 4000 ten thousand tons based on 80% of water. Although the municipal sludge is rich in organic matters and various nutrient elements, the municipal sludge also contains a large amount of pathogenic bacteria, parasitic ova, heavy metals, polycyclic aromatic hydrocarbons and other toxic and harmful substances. The sludge treatment technology mainly comprises sludge drying, concentration and dehydration, anaerobic digestion, aerobic fermentation and the like, and the sludge disposal mode mainly comprises landfill, land utilization, building material utilization, incineration and the like.

At present, the sludge treatment technology in developed countries is relatively mature, and the legal system is also relatively perfect. Sludge disposal in european areas is gradually developed from land utilization and landfill to incineration, sludge disposal in north america has been mainly for agricultural use and incineration, and sludge disposal in japan is mainly for building material utilization after incineration due to land restriction.

The sludge treatment in cities and towns in China is mainly land landfill, and the landfill sites of all main cities are nearly saturated, so that the phenomenon of sludge enclosing the city is gradually formed. With the stricter urban environmental protection policy, the proportion of direct landfill treatment of urban sludge is gradually reduced. Meanwhile, most municipal industrial and domestic sewage share the same pipe network, so that the content of various heavy metals in the sludge is high, and the land utilization is limited. In contrast, sludge incineration can not only eliminate harmful substances, but also greatly reduce the volume of sludge, can realize harmless treatment of sludge, and is one of the most promising sludge disposal methods.

Municipal sludge, also called municipal sludge, mainly refers to sludge from sewage treatment plants, which is the largest amount of sludge, and mainly has the following characteristics:

1) the water content is high and can reach about 80 percent generally;

2) the content of microorganisms and pathogens is high;

3) the odor pollutes the environment;

4) contains heavy metals;

5) contains fine powder.

The characteristics of the sludge bring great difficulty to the harmless treatment of the sludge, but the sludge contains a plurality of organic matters and has certain utilization value. Generally, the sludge treatment should be carried out according to the principles of harmlessness, reduction and resource utilization, and the sludge incineration by the coal-fired unit coupling completely conforms to the principles.

The coal-fired unit coupled sludge power generation is used as a sludge incineration utilization form, has the unique advantages of high treatment capacity, strong adaptability, high system efficiency and the like, and has attracted extensive attention in recent years. The national energy agency proposes in 2017 that 'areas mainly based on landfill sites are selected preferentially to generate a cogeneration coal-electric machine set, and lay out technical improvement projects of coupling garbage and sludge power generation by burning coal, with the emphasis on 36 key cities such as direct prefectures, provincial cities, planned single-row cities and the like, large garbage and sludge generation amount and difficult land utilization or limited space', and 42 demonstration projects of coupling sludge power generation are approved for the first time.

The current coal-fired coupled sludge incineration power generation mainly adopts the following three modes:

1) for a circulating fluidized bed CFB boiler, sludge to the plant is pumped into the CFB boiler by a pumping system and combusted by a plunger pump. The sludge blending combustion proportion of the method can reach 5 to 10 percent generally;

2) the advantage that a power plant has different step heat sources is utilized, sludge arriving at the plant is dried through a steam indirect drying (tube array and disc) process, the moisture of the dried sludge can be controlled to be about 40%, and the dried sludge can be mixed with raw coal in a coal yard, then enters a coal mill through a coal supply system and finally enters a boiler for combustion. This approach is commonly used in pulverized coal boilers equipped with various types of coal mills. The mixing proportion can reach 10 percent;

3) high-temperature flue gas generated by a power station boiler is used for drying sludge arriving at a factory through a flue gas drying process, and the sludge is dried by an integrated processor and is sent into a hearth for combustion through a pipeline. This approach is commonly used in pulverized coal boilers equipped with various types of coal mills. The mixing proportion can reach 5 percent.

The above three sludge mixing burning modes can only select the second mode or the third mode for the power station boiler provided with the storage type powder making system in the steel ball coal mill. The mode II (sludge drying) has large investment, complex system, higher operation energy consumption and high drying cost of each ton of sludge; the investment of the third mode is slightly reduced compared with that of the second mode, but a sludge integrated processor still needs to be arranged.

Disclosure of Invention

The invention aims to overcome the defect that the existing sludge mixing combustion technology cannot realize large-proportion sludge mixing combustion on a storage type powder making system in a steel ball coal mill, and provides a process for generating power by coupling sludge drying combustion with the storage type powder making system.

The invention is realized by adopting the following technical scheme:

the process for generating power by coupling the sludge drying and burning through the middle storage type powder making system comprises a furnace pumping smoke pipe and a steel ball coal mill, wherein the steel ball coal mill uses sludge conveyed by a pumping system, the furnace pumping smoke pipe is used for pumping hot smoke at the bottom of a boiler hearth and sending the hot smoke into the steel ball coal mill to predry the sludge.

The invention is further improved in that the water content of the sludge is +/-80%.

The invention is further improved in that the storage type pulverizing system also comprises a primary air fan, an air feeder, an air preheater arranged in a flue at the tail part of the boiler, a burner and a tertiary air nozzle which are sequentially arranged on the side wall of the boiler from bottom to top, primary air and secondary air sent by the primary air fan and the air feeder are respectively preheated by the air preheater, the preheated primary air is sent to the burner, and the preheated secondary air and hot flue gas sucked by a smoke pipe of the boiler are sent to a steel ball coal mill together.

The invention is further improved in that the intermediate storage type pulverizing system also comprises a powder discharge fan and a powder feeding exhaust gas regulating valve, wherein the powder discharge fan is used for providing negative pressure suction, under the negative pressure suction of the powder discharge fan, exhaust gas carries pulverized coal to sequentially enter a coarse powder separator and a fine powder separator, the exhaust gas is separated by the fine powder separator and then is divided into two parts, one part is mixed with hot primary air through the powder feeding exhaust gas regulating valve, the pulverized coal output by the powder feeder is fed into a burner by hot air exhaust gas mixed gas and then enters a hearth for combustion, and the other part of the exhaust gas is directly fed into a tertiary air nozzle and is sprayed into the hearth.

The invention is further improved in that the coal powder prepared by the steel ball coal mill falls into the powder bin after being screened by the coarse powder separator and the fine powder separator in turn, and the coal powder in the powder bin is sent into the combustor by the powder feeder.

The invention further improves that the storage pulverizing system also comprises a coal feeder, and an air lock is arranged between the coal feeder and the coarse powder separator and used for preventing air from leaking in during powder unloading.

The invention has at least the following beneficial technical effects:

according to the process for generating power by coupling the sludge drying incineration with the middle storage type powder making system, the furnace smoke pumping pipe is additionally arranged, hot smoke at the bottom of the hearth is pumped to enter the steel ball coal mill, the drying capacity of the powder making system is improved, the sludge can be fully dried, the humidity-carrying exhaust gas finally enters the hearth through the tertiary air nozzle, staged combustion is realized, and NOx emission is reduced. The hot flue gas that the smoke tube of taking out the stove extracted can form inert atmosphere in the powder process system to improve the adaptability of powder process system to mixing mud volatile, reduced explosion-proof risk.

Compared with the existing sludge co-combustion technology, the method adopts a mode of extracting the hot furnace smoke, greatly improves the temperature of the initial drying agent, and increases the heat capacity and drying capacity of the drying agent. The hot furnace smoke meets the sludge conveyed by the sludge pumping system at the spiral feeding hole, so that the sludge is quickly pre-dried, the moisture of the sludge entering the cylinder is reduced, the probability of wrapping the steel ball by the sludge can be correspondingly reduced, and the influence of the co-combustion sludge on the grinding capacity of the steel ball coal mill is reduced to a lower level. Because the oxygen content of the drying agent can be reduced by doping the hot furnace smoke, an inert atmosphere is formed in the powder making system, the adaptability of the powder making system to the doped sludge volatile components is improved, and the explosion-proof risk is reduced. The pulverized coal conveying mode is a hot air and exhaust gas mixed powder conveying mode, so that the explosion-proof requirement of the powder preparation system after sludge is mixed and burned can be met, and the NOx emission can be further reduced. The hot air and exhaust gas mixed powder feeding system is also provided with an exhaust gas adjusting device, so that the proportion of hot air and exhaust gas can be adjusted, and the change of different volatile components can be adapted. The design fully meets the objective conditions required by blending and burning the sludge, thereby exerting the conveying capacity of the sludge pumping system to the maximum extent, and the process is a process for generating electricity by coupling the storage pulverizing system with sludge drying and burning.

Drawings

FIG. 1 is a schematic view of a process for generating electricity by coupling a sludge drying and incineration with a storage pulverizing system.

The notation in the figure is:

the device comprises a boiler 1, an air preheater 2, a primary air fan 3, a blower 4, a coal feeder 5, a steel ball coal mill 6, a coarse powder separator 7, an air locker 8, a fine powder separator 9, a powder discharge fan 10, a powder feeding exhaust air regulating valve 11, a powder bin 12, a powder feeder 13, a combustor 14 and a tertiary air nozzle 15.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

Referring to fig. 1, the process for generating power by coupling sludge drying and incineration with a storage pulverizing system provided by the invention comprises a furnace smoke extraction pipe, an air preheater 2, a primary air fan 3, a blower 4, a coal feeder 5, a steel ball coal mill 6, a coarse powder separator 7, a fine powder separator 9, a powder discharge fan 10, a powder feeding exhaust air regulating valve 11, a powder bin 12, a powder feeder 13, and a combustor 14 and a tertiary air nozzle 15 which are sequentially arranged on the side wall of a boiler 1 from bottom to top. Wherein the steel ball coal mill 6 uses the sludge delivered by a pumping system, and the furnace smoke pumping pipe is used for pumping hot smoke at the bottom of the hearth of the boiler 1 and delivering the hot smoke into the steel ball coal mill 6 to pre-dry the sludge. The primary air and the secondary air sent by the primary air fan 3 and the air feeder 4 are respectively preheated by the air preheater 2, the preheated primary air is sent to the burner 14, and the preheated secondary air and the hot flue gas sucked by the smoke tube of the furnace are sent to the steel ball coal mill 6 together. The coal powder prepared by the steel ball coal mill 6 is screened by the coarse powder separator 7 and the fine powder separator 9 in turn and then falls into the powder bin 12, and the coal powder in the powder bin 12 is sent into the combustor 14 by the powder feeder 13. An air lock 8 is arranged between the coal feeder 5 and the coarse powder separator 7 and is used for preventing air from leaking in during powder unloading. The powder discharge fan 10 is used for providing negative pressure suction, under the negative pressure suction of the powder discharge fan 10, exhaust gas carries coal powder to sequentially enter the coarse powder separator 7 and the fine powder separator 9, the exhaust gas is separated by the fine powder separator 9 and then is divided into two streams, one stream is mixed with hot primary air through the powder feeding exhaust air regulating valve 11, hot air exhaust gas mixed gas sends the coal powder output by the powder feeder 13 to the combustor 14 to enter the hearth for combustion, and the other stream of exhaust gas is directly sent to the tertiary air nozzle 15 to be sprayed into the hearth.

When the device works, sludge is directly conveyed to a spiral feeding port of a steel ball coal mill by a pumping system and directly contacts with hot flue gas and hot secondary air sucked from the bottom of a hearth of a boiler 1 for heat exchange; the heat capacity and drying capacity of the drying agent are greatly improved due to the collection of the hot flue gas, so that the sludge is quickly pre-dried during axial feeding, and the moisture of the sludge is reduced to a certain extent; the sludge after pre-drying and the raw coal sent by the coal feeder 5 fall into a cylinder of a steel ball coal mill 6 together, and are further crushed and ground by steel balls, and the moisture of the sludge is further reduced to 40% along with drying in the grinding process; under the negative pressure suction of a powder discharge fan 10, exhaust gas carries coal powder to enter a coarse powder separator 7 and a fine powder separator 9 in sequence, finally the coal powder with qualified moisture and fineness falls into a powder bin 12, the exhaust gas is separated by the fine powder separator 9 and then divided into two parts, one part is mixed with hot primary air through a powder feeding exhaust gas regulating valve 11, the hot air exhaust gas mixed gas sends the coal powder output by a powder feeder 13 to a combustor 14 to enter a hearth for combustion, and the other part of the exhaust gas is directly sent to a tertiary air nozzle 15 to be sprayed into the hearth.

In this system, mud is carried by comparatively ripe reliable mud pumping system and comes, and moisture is usually about 80%, before getting into barrel direct contact steel ball, mud in hollow shaft spiral feeding structure with hot stove cigarette, the abundant contact heat transfer of hot overgrate air, accomplish predrying, mud moisture after the predrying reduces, the stickness reduces, the parcel steel ball causes the probability that grinds the inefficacy to reduce, has just also reduced the influence of exerting oneself to the grinding of steel ball coal mill. After the hot furnace smoke is introduced, the temperature and the heat capacity of the drying agent are greatly improved, and the drying capacity of the powder making system is greatly improved, so that 10% of sludge mixed combustion can be realized.

The invention fully considers the high organic matter content in the sludge and the high volatile content of the sludge. The introduction of the hot furnace smoke reduces the oxygen content of the drying agent, so that the powder making system is in an inert atmosphere, and the problem of doping the sludge with high volatile components is solved.

The invention adopts a waste gas and hot air mixed powder feeding mode, and the powder feeding waste gas pipeline is provided with the adjusting valve, thereby realizing the adjustment of the proportion of the waste gas and the hot air. The exhaust gas and hot air mixed powder feeding not only can be well adapted to the change of fuel characteristics, but also can further reduce the emission of NOx and meet the requirement of environmental protection.

In conclusion, the furnace smoke extraction pipe is additionally arranged, the hot smoke in the furnace is extracted to enter the steel ball coal mill, the drying capacity of the powder making system is improved, the sludge consumption capacity is further improved, meanwhile, the inert atmosphere can be formed in the powder making system, the adaptability of the powder making system to the doped sludge volatile components is improved, and the explosion-proof risk is reduced; the powder feeding mode of mixing exhaust gas and hot air is adopted, the proportion of the exhaust gas and the hot air is adjustable, the change of fuel characteristics can be well adapted, the requirement of environmental protection is also considered, and the emission of NOx is further reduced. The improved coal pulverizing system has the advantages of less modification work amount, simple system arrangement, matching with a sludge pumping system, capability of realizing large-proportion sludge mixed combustion, low production and operation cost and capability of realizing considerable economic benefit.

Claims

1. The process is characterized in that the intermediate storage type powder making system used by the process comprises a furnace smoke extraction pipe and a steel ball coal mill (6), wherein the steel ball coal mill (6) uses sludge conveyed by a pumping system, the furnace smoke extraction pipe is used for extracting hot smoke at the bottom of a hearth of a boiler (1) and conveying the hot smoke into the steel ball coal mill (6) to predry the sludge.

2. The process of claim 1, wherein the moisture content of the sludge is ± 80%.

3. The process for generating power by coupling sludge drying and incineration through the mesostorage pulverizing system according to claim 1, characterized in that the mesostorage pulverizing system further comprises a primary air fan (3), a blower (4), an air preheater (2) arranged in a flue at the tail of the boiler (1), and a burner (14) and a tertiary air nozzle (15) which are sequentially arranged on the side wall of the boiler (1) from bottom to top, wherein primary air and secondary air sent by the primary air fan (3) and the blower (4) are respectively preheated by the air preheater (2), the preheated primary air is sent to the burner (14), and the preheated secondary air and hot flue gas sucked by a smoke pipe of the furnace are sent to the steel ball coal mill (6) together.

4. The process for generating power by coupling sludge drying and incineration through the intermediately stored pulverizing system according to claim 3, characterized in that the intermediately stored pulverizing system further comprises a powder discharge fan (10) and a powder feeding exhaust air regulating valve (11), wherein the powder discharge fan (10) is used for providing negative pressure suction, under the negative pressure suction of the powder discharge fan (10), exhaust gas carries pulverized coal to sequentially enter the coarse powder separator (7) and the fine powder separator (9), the exhaust gas is separated by the fine powder separator (9) and then divided into two streams, one stream is mixed with hot primary air through the powder feeding exhaust air regulating valve (11), the pulverized coal output by the powder feeder (13) is fed into the combustor (14) through hot air exhaust gas mixed gas to be combusted, and the other stream is directly fed into the tertiary air nozzle (15) to be sprayed into the hearth.

5. The process for generating power by coupling sludge drying and incineration through the intermediately storing pulverizing system according to claim 3, wherein pulverized coal produced by the steel ball coal mill (6) is screened sequentially through the coarse powder separator (7) and the fine powder separator (9) and then falls into the powder bin (12), and the pulverized coal in the powder bin (12) is fed into the combustor (14) through the powder feeder (13).

6. The process for generating power by coupling sludge drying and incineration with the bin-feeder pulverizing system as claimed in claim 3, characterized in that the bin-feeder pulverizing system further comprises a coal feeder (5), and an air lock (8) is further arranged between the coal feeder (5) and the coarse powder separator (7) for preventing air from leaking in during discharging.