CN115597340A - System and method for indirectly drying water-washed fly ash - Google Patents

Abstract

The invention discloses a system and method for indirect drying of washed fly ash. The washed fly ash is dried in an indirect drying manner. The system mainly includes a mixing unit, a heat source generating unit, an indirect drying unit, a flue gas processing unit, and a finished fly ash storage unit. The mixing unit is the inlet of the washed fly ash indirect drying system, the outlet of the mixing unit is connected to the feed port of the indirect drying unit, the outlet of the heat source generating unit is connected to the heat source inlet of the indirect drying unit The dust gas outlet of the indirect drying unit is connected with the inlet of the flue gas treatment unit, the outlet of the indirect drying unit is connected with the inlet of the finished fly ash storage unit, and the finished fly ash storage unit The outlet is the outlet of the indirect drying system for washed fly ash. The steps of the method include material mixture preparation, equipment preheating, indirect drying, fly ash storage, flue gas treatment and waste heat utilization. It is beneficial to reduce the energy consumption of the whole system.

Description

A system and method for indirect drying of washed fly ash

technical field

The invention belongs to the technical field of domestic waste incineration fly ash treatment, and relates to a system and method for indirect drying of washed fly ash.

Background technique

In recent years, the amount of domestic waste incineration in my country has shown an increasing trend year by year. The increasing amount of domestic waste incineration has led to an increase in the output of its by-product—fly ash. The fly ash of domestic waste incineration contains heavy metals, dioxins, and furans. Toxic substances such as fly ash are identified as hazardous waste by many countries, therefore, the disposal of fly ash is very important.

Although fly ash is hazardous waste, the main components of fly ash are calcium, silicon compounds and soluble salts, which can be processed as resources, such as co-processing in cement kilns, high-temperature sintering, plasma melting, etc. However, the soluble salts in fly ash will affect the subsequent high-temperature disposal kiln, and desalination pretreatment of fly ash is required. Fly ash washing can effectively remove the soluble salt content, which is an essential pretreatment link before fly ash resource disposal. After the fly ash is washed and pretreated, the soluble salts can be extracted for industrial utilization. After washing, the fly ash can be used as a building material raw material, saving raw materials and reducing costs.

During the pretreatment process of fly ash washing, a centrifuge is usually used for solid-liquid separation. The water content of the washed fly ash after separation is about 30%-40%. If the high-temperature calcination is directly used for resource disposal, it will cause great damage to the high-temperature kiln. impact, and consumes a lot of energy. Therefore, it is necessary to dry the washed fly ash. At present, the washed fly ash usually adopts the direct drying method, which uses the existing heat source of the resource-based enterprises to reduce its moisture content through direct contact with the washed fly ash. This method has high heat transfer efficiency and good drying efficiency of the washed fly ash. However, This method needs to use the existing heat source of the resource enterprise, and the heat source consumption is relatively large, which is easy to affect the existing production line of the resource enterprise. In addition, the method of direct drying of washed fly ash produces a large amount of tail gas, and the content of particulate matter in the tail gas is relatively large, and the subsequent tail gas treatment pressure is high.

The particle size of fly ash is relatively fine (1-100μm), and its viscosity is relatively high. During the drying process, it is easy to hang on the wall, and it is easy to harden. It is difficult to clean and affects the drying efficiency; if the moisture content of fly ash is high, the During the drying process, the phenomenon of "clumping" is prone to occur, that is, the surface of the "clump" fly ash is dry, but the moisture content inside the "clump" is still high. Therefore, it is more difficult to directly dry fly ash with higher moisture content. Aiming at the deficiencies of the prior art, combined with the physical characteristics of the fly ash, the present invention proposes a system and method for indirect drying of the washed fly ash. The indirect drying method is used to dry the washed fly ash, and the water content of the washed fly ash can be reduced from 40% is reduced to less than 5%, which solves the problems of high energy consumption and difficult tail gas treatment caused by direct drying, and solves the problems of wall hanging and hardening that are prone to occur in indirect drying, and further optimizes the process of fly ash washing pretreatment The drying link can improve the fly ash resource disposal capacity.

(1) Prior art one relates to a process and system device for indirect drying of lignite by low-temperature steam. The system device mainly includes a raw coal bunker, a coal feeder, a dryer, a rotary sealed feed valve, a buried scraper conveyor, a condensation tank, Traps, condensate pumps, dust collectors, fans. The detailed process steps are as follows: ① Put the lignite with a water content of 35% to 50% in mass percentage and a particle size of ≤20mm from the raw coal bunker into the drying pipe of the dryer through a coal feeder; Outside the drying tube, the brown coal in the drying tube and the steam outside the drying tube are subjected to indirect heat exchange to achieve the purpose of drying the lignite. The pressure of the low-temperature steam is 0.55-0.6MPaG and the temperature is 165-175°C; ③In step ② The condensate after heat exchange enters the condensation tank through the steam trap; the condensate is finally discharged by the condensate pump; ④The dried lignite in step ② comes out of the discharge port of the dryer, and enters the buried scraper through the rotary sealing feed valve. Plate conveyor; 5. step 2. in the lignite drying process, the water vapor produced by lignite and the air with pulverized coal form tail gas, and the tail gas is discharged after being filtered by the dust collector under the suction of the blower fan; 6. step 5. The coal powder filtered by the dust collector enters the buried scraper conveyor through the coal drop pipe.

The raw material processed by this prior art is lignite, and the particle size is much larger than that of fly ash. Most of the existing indirect drying equipment is used in sludge and coal chemical drying industries, and is rarely used in drying treatment of washed fly ash. Although the overall drying process and equipment are similar, due to the hazardous waste properties of fly ash and the characteristics of fly ash, the indirect drying technology of fly ash still needs to solve some problems, such as fine particle size of fly ash and equipment wear and tear. Therefore, water washing The fly ash indirect drying technology belongs to a new technical field.

(2) The second prior art relates to a thermal drying system and method for sludge (invention application) (CN 113371975 A)

(1) A sludge thermal drying system, including an air compression system, a heat exchange system and a sludge drying system, characterized in that the air compression system includes a screw heat pump, which is used to circulate the pure steam in the entire system reheat;

Heat exchange system, including falling film evaporator, for heat exchange and evaporation of condensed water of pure steam;

Sludge drying system, including drying machine, is used to reduce the moisture content of sludge, and discharge the sludge with low water content to the fuel rod production equipment;

Among them, the air compression system also includes a gas-liquid separator. After the high-temperature steam heated by the screw heat pump passes through the gas-liquid separator, it enters the heat exchange mechanism of the dryer to dry the sludge in the dryer. The heat exchange mechanism The condensed water generated in the dryer enters the shell side of the falling film evaporator, and the sludge steam generated by the dryer enters the tube side of the falling film evaporator, and the condensed water generated by the heat exchange mechanism of the dryer is evaporated, and the steam passes through the screw After the heat pump heats up, a self-circulation is formed in the system. A water washing tower is installed between the sludge steam outlet of the drying machine and the falling film evaporator. The non-condensable gas generated by the tube side of the device is sent to the exhaust gas treatment device.

(2) thermal drying method of sludge

Ⅰ. Equipment preheating: Add pure water to the gas-liquid separator, and the pure water enters the falling film evaporator through the pipeline. The heating device installed in the falling film evaporator first evaporates the pure water to form clean steam, which is produced by the The steam outlet of the evaporator enters the screw heat pump to be compressed and heated up to form high-amplitude compressed hot steam. The compressed hot steam enters the heat exchange mechanism of the dryer through the gas-liquid separator to preheat the dryer;

Ⅱ. Sludge drying: The sludge with a moisture content of 70%-90% is sent into the dryer through a screw feeder, and under the action of the drive shaft of the dryer, the sludge is heated inside the dryer Gradually dry, and the dried sludge goes to the fuel rod making device along the discharge port of the dryer;

Ⅲ. Steam cycle: The sludge steam generated during the sludge drying process enters the tube side of the falling film evaporator through the water washing tower along the sludge steam outlet of the dryer, and at the same time, it is discharged from the heat exchange device of the dryer The distilled water enters the spray port of the shell side of the falling film evaporator, and the distilled water sprayed out of the spray port evaporates under the high temperature of the heat exchange tube to form a clean steam cycle;

After the sludge steam enters the heat exchange tube for heat exchange, the formed water enters the water washing tower, and the water washing tower circulates the stored water to the washing water inlet of the water washing tower through the circulation pump, and washes the sludge steam from the dryer. impurities;

Ⅳ. Waste treatment: In the process of evaporating pure water in the falling film evaporator, part of the sludge steam in the heat exchange tube is converted into water and enters the water washing tower, and part of the non-condensable gas enters the tail gas treatment pipeline to the tail gas treatment device. The processing pipeline is connected to the plate heat exchanger to cool down the non-condensable gas, and the plate heat exchanger uses the water from the gas-liquid separator to cool down;

The sewage discharged from the water washing tower enters the sleeve structure of the screw feeder, and after passing through the preheating layer of the silo, it is discharged to the sewage treatment device.

(3) Lack of technology

The falling film evaporator is used to generate steam to dry the sludge and reduce the moisture content of the sludge. It is not clearly stated that the drying device is indirect drying, but it can be seen from the description that the drying equipment is indirect drying equipment, and the recycling of condensed water and secondary steam is proposed, and the whole system is relatively mature. However, the physical and chemical properties of fly ash and sludge are very different. Fly ash has a finer particle size (1-100um) and higher viscosity. It is more difficult; if the moisture content of the fly ash is high, the phenomenon of "clumping" will easily occur during the drying process, that is, the surface of the "clump" fly ash is dry, but the moisture content inside the "clump" is still high. Therefore, fly ash with high moisture content cannot be directly dried.

To sum up, the indirect drying system and method for washing fly ash need to be designed and implemented in combination with the characteristics of fly ash.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention proposes a system and method for indirect drying of washed fly ash, which uses indirect drying to dry washed fly ash to provide technical support for subsequent resource utilization of fly ash.

In order to solve the problems of the technologies described above, the first technical solution provided by the present invention is as follows:

A system for indirect drying of washed fly ash mainly includes a mixing unit, a heat source generating unit, an indirect drying unit, a flue gas processing unit, and a finished fly ash storage unit.

The mixing unit is the inlet of the washed fly ash indirect drying system, the outlet of the mixing unit is connected to the feed port of the indirect drying unit, the outlet of the heat source generating unit is connected to the heat source inlet of the indirect drying unit The dust gas outlet of the indirect drying unit is connected with the inlet of the flue gas treatment unit, the discharge port of the indirect drying unit is connected with the inlet of the finished fly ash storage unit, and the finished fly ash storage unit The outlet is the outlet of the indirect drying system for washed fly ash.

The mixing unit includes a mixer and a fly ash conveying device. The mixer is provided with two feed ports, which are the feed port for washed fly ash and the feed port for dry fly ash, and the dry fly ash and washed fly ash are homogeneously mixed in the mixer to reduce the overall moisture content of the material , and keep the material in a uniform state.

Further, the dry fly ash feed port of the mixer is connected with the outlet of the finished fly ash temporary storage bin.

Further, the mixer is preferably a horizontal mixer, so as to facilitate feeding and control the mixing time.

Further, the fly ash conveying device is preferably a screw conveyor, so as to control the mixing amount of dry fly ash.

The heat source generating unit includes a water softener, a heat source generator, a condensed water collector, and a heat exchanger. The inlet of the water softener is the inlet of the heat source generating unit, the outlet of the water softener is connected to the inlet of the heat source generator, and the outlet of the heat source generator is connected to the heat source inlet of the indirect dryer.

Further, the inlet of the water softener is connected with the tap water pipeline to provide softened water for the heat source generator to prevent scaling and blockage of the heat source generator.

Further, the inlet of the condensed water collector is connected with the condensed water outlet of the indirect dryer, and the outlet of the condensed water collector is connected with the inlet of the heat source generator to collect condensed water stably and achieve recycling.

Further, the inlet of the heat exchanger is connected to the outlet of the flue gas treatment unit, and the outlet of the heat exchanger is connected to the jacket steam inlet of the indirect dryer, so that the outer jacket of the indirect dryer The thermal insulation further improves the drying efficiency of fly ash.

Further, the heat exchanger performs secondary heating for the high-temperature flue gas discharged from the flue gas treatment unit, so as to better realize heat recycling and reduce system energy consumption.

Further, the pipes conveying saturated steam in the heat source generating unit are provided with insulation layers to reduce heat loss.

The indirect drying unit includes a quantitative feeder and an indirect dryer. The outlet of the quantitative feeder is connected to the inlet of the indirect dryer, the outlet of the indirect dryer is connected to the inlet of the finished fly ash storage unit, and the dust gas outlet of the indirect dryer is connected to the inlet of the finished fly ash storage unit. The flue gas treatment unit is connected.

Further, the indirect dryer can be a rotary dryer, a rotary dryer, or a paddle dryer. The heat exchange efficiency of the above indirect drying equipment is high, and all of them can meet the requirements of the process system of the present invention.

Further, the quantitative feeder is preferably a screw feeder to ensure uniform feeding.

Further, the rotating shaft of the indirect dryer is adjustable by frequency conversion, so as to control the indirect drying time and better ensure the moisture content of the output.

Further, the heat source of the indirect dryer can be saturated steam, superheated steam or heat transfer oil. Steam and heat transfer oil are commonly used heat sources for indirect drying equipment, both of which have good thermodynamic properties and high heat utilization rate.

Furthermore, when the indirect drying system of water-washed fly ash is established in a resource disposal enterprise, the existing heat source in the plant area can be used to further save energy consumption. If the resource-based enterprise has available saturated steam heat source, the saturated steam can be pretreated by the temperature and pressure reduction device, and used as the heat source of the indirect drying system for washing fly ash;

Further, the internal gas environment of the indirect dryer is slightly negative pressure, so as to facilitate the discharge of the moisture-carrying smoke generated inside, and at the same time prevent gas leakage.

Further, the inside of the indirect dryer is equipped with structural parts to prevent the fly ash from sticking to the wall and help maintain the looseness of the fly ash.

Further, the outlet of the indirect dryer is provided with a feeding valve, which can automatically control the feeding speed.

The flue gas treatment unit includes a dust collector, an induced draft fan, and monitoring instruments. The inlet of the dust collector is the inlet of the flue gas processing unit, the outlet of the dust collector is connected to the inlet of the induced fan, and the outlet of the induced fan is the outlet of the flue gas processing unit.

Further, the dust collector is preferably a pulse bag filter to remove particulate matter in the flue gas.

Further, the bag material of the pulse bag filter is preferably PTFE film, which has high dust removal efficiency and strong air permeability.

Further, the monitoring instruments are temperature and pressure instruments, which are installed before and after the dust collector to better monitor the flue gas data of the system.

Further, the fly ash collected at the bottom of the dust collector is sent into the finished fly ash storage bin.

The finished fly ash storage unit includes a finished fly ash storage bin, a finished fly ash temporary storage bin, and a finished fly ash conveying pipeline. The entrance of the finished fly ash storage bin is the entrance of the fly ash storage unit, and the outlet of the finished fly ash storage bin is the exit of the fly ash storage unit, which is connected to the subsequent fly ash resource disposal system.

Further, the entrance of the finished fly ash temporary storage bin is connected to the entrance of the finished fly ash storage bin, and the fly ash is transported to the finished fly ash storage bin and the finished fly ash temporary storage bin through a chute.

Further, the bottoms of the finished fly ash storage bin and the finished fly ash temporary storage bin are provided with air nozzles to facilitate unimpeded feeding.

The second technical solution of the present invention is a method for indirect drying of washed fly ash, the steps are as follows:

① Mixing preparation: the washed fly ash (with a moisture content of about 40%) is transported to the washed fly ash inlet of the mixer, and the dry fly ash in the fly ash temporary storage bin is transported to the dry fly ash inlet of the mixer through a quantitative feeder. The washed fly ash and the dried fly ash are stirred and mixed in the mixer to reduce the moisture content of the mixed material to 10%-30%, and the material mixing time is 2-3min.

②Equipment preheating: turn on the tap water switch, and enter the heat source generator after being softened by the water softener. Then, the saturated steam generated is transported to the heat source inlet of the indirect dryer through the insulation pipeline to preheat the indirect dryer;

Among them, the condition of saturated steam is 0.5-0.8MPa.

③Indirect drying: After the saturated steam preheats the indirect dryer, the fly ash mixed in step ① is conveyed to the feed port of the indirect dryer by a screw, and the material moves to the discharge end through the rotation of the inner rotary table of the dryer. During the process, the purpose of reducing the moisture content of fly ash is achieved by contacting the partition wall of the heat source for heat transfer. In addition, there are structural parts inside the dryer, which can effectively prevent fly ash from sticking to the wall and clumping together, which is conducive to maintaining the uniformity of fly ash discharge. and looseness. Wherein, the moisture content of the fly ash after drying is ≤5%, and the drying time can be set at 1.5-2.5 hours.

At the same time, the condensed water discharged from the indirect dryer enters the condensed water collector for recycling.

④ Fly ash storage: The dried material in step ③ is transported to the finished fly ash storage bin and the finished fly ash temporary storage bin through the discharge end. Among them, the fly ash in the finished fly ash storage bin is used for subsequent resource disposal, and the fly ash in the finished fly ash temporary storage bin is returned to the mixing unit for recycling.

⑤ Flue gas treatment: In step ③, the wet flue gas generated inside the indirect dryer enters the flue gas treatment unit, and the dust is removed by the bag filter to ensure that the particle concentration in the flue gas is ≤10mg/m ³ . Among them, the front end of the bag filter is equipped with temperature and pressure monitoring instruments, and through data monitoring, it is possible to prevent condensation of wet flue gas and cause blockage of the bag filter. The fly ash collected by the bag filter enters the finished fly ash storage bin.

⑥Residual heat utilization: After the high-temperature flue gas after dedusting in step ⑤ is reheated by the heat exchanger, it can be used as a heat source again in the jacket of the indirect dryer for secondary use.

Beneficial effect:

Compared with the prior art, it has the following technical effects:

(1) The method of indirect drying is adopted, and the moisture content in the fly ash is reduced by using the heat transfer of the partition wall, and the heat transfer efficiency is high, which can fully meet the needs of the drying process.

(2) The indirect drying method is used to reduce the moisture content in the fly ash by using the heat transfer of the partition wall. The heat source does not directly contact the fly ash, and the generated flue gas and dust content are small, and the pressure of the subsequent flue gas treatment process is relatively small.

(3) The method of mixing pretreatment is used to mix the washed fly ash with the dried finished product ash to reduce the moisture content of the feed to the dryer. While improving the drying efficiency, the material is evenly dispersed and effectively It is beneficial to the fluidity of the fly ash mixture in the indirect drying equipment, and is conducive to ensuring the loose state of the output.

(4) The indirect drying of washed fly ash has changed the previous direct drying method of using the existing heat source of resource enterprises, reduced the impact on the equipment of resource enterprises, and is conducive to reducing the energy consumption of the entire system.

Description of drawings

Fig. 1 system flow diagram of indirect drying of washed fly ash;

Fig. 2 Process flow chart of indirect drying of washed fly ash (saturated steam).

Fig. 3 Process flow chart of indirect drying of washed fly ash (heat transfer oil).

detailed description

The present invention will be further described below, and a clear and complete description will be given below, and all implementation modes of the present invention cannot be enumerated in the examples.

(1) Saturated steam

① Mixing preparation: the washed fly ash with a moisture content of 40% is transported to the water-washed fly ash inlet of the mixer, and the dry fly ash in the fly ash temporary storage bin is conveyed to the dry fly ash inlet of the mixer by a screw conveyor , stirring and mixing the washed fly ash and the dried fly ash in the mixer, the material mixing time is 2min, and the moisture content of the mixed material is reduced to 20%.

②Equipment preheating: Turn on the tap water switch, and enter the heat source generator after being softened by the water softener. Then, the generated 0.6Mpa saturated steam is transported to the heat source inlet of the indirect dryer through the insulation pipeline to preheat the indirect dryer.

③Indirect drying: After the saturated steam preheats the indirect dryer, the mixed fly ash with a moisture content of 20% in step ① is conveyed to the feed port of the indirect dryer by a screw, and the material moves to the discharge end through the rotation of the inner rotary table of the dryer. The drying time is set at 2 hours, and the moisture content of the fly ash after drying is ≤5%. At the same time, the condensed water discharged from the indirect dryer enters the condensed water collector for recycling.

④Fly ash storage: In step ③, the materials with a moisture content of ≤5% are transported to the finished fly ash storage bin and the finished fly ash temporary storage bin through the discharge end.

⑤ Flue gas treatment: In step ③, the wet flue gas generated inside the indirect dryer enters the flue gas treatment unit, and the dust is removed by the bag filter. The concentration of particulate matter in the flue gas after treatment is ≤10mg/m ³ . By monitoring the temperature and pressure monitors at the front end of the bag filter to prevent condensation of wet flue gas. The fly ash collected by the bag filter enters the finished fly ash storage bin.

⑥Residual heat utilization: After the high-temperature flue gas after dedusting in step ⑤ is reheated by the heat exchanger, the temperature reaches 160°C, and then enters the jacket of the indirect dryer as a heat source for secondary use.

(2) heat transfer oil

① Mixing preparation: the washed fly ash with a moisture content of 40% is transported to the water-washed fly ash inlet of the mixer, and the dry fly ash in the fly ash temporary storage bin is conveyed to the dry fly ash inlet of the mixer by a screw conveyor , stirring and mixing the washed fly ash and the dried fly ash in the mixer, the material mixing time is 2min, and the moisture content of the mixed material is reduced to 20%.

②Equipment preheating: Turn on the electric heating device to heat the heat transfer oil. The heating temperature of the heat transfer oil is set to 140°C. Then, the heat transfer oil is transported to the heat source inlet of the indirect dryer through the insulation pipeline to preheat the indirect dryer.

③Indirect drying: After the heat conduction oil preheats the indirect dryer, the mixed fly ash with a moisture content of 20% in step ① is conveyed to the feed port of the indirect dryer by a screw, and the material moves to the discharge end through the rotation of the inner rotary table of the dryer. The drying time is set at 2 hours, and the moisture content of the fly ash after drying is ≤5%. At the same time, the heat transfer oil discharged from the indirect dryer is returned to the electric heating device for recycling.

④Fly ash storage: In step ③, the materials with a moisture content of ≤5% are transported to the finished fly ash storage bin and the finished fly ash temporary storage bin through the discharge end.

⑤ Flue gas treatment: In step ③, the wet flue gas generated inside the indirect dryer enters the flue gas treatment unit, and the dust is removed by the bag filter. The concentration of particulate matter in the flue gas after treatment is ≤10mg/m ³ . By monitoring the temperature and pressure monitors at the front end of the bag filter to prevent condensation of wet flue gas. The fly ash collected by the bag filter enters the finished fly ash storage bin.

⑥Residual heat utilization: After the high-temperature flue gas after dedusting in step ⑤ is reheated by the heat exchanger, the temperature reaches 160°C, and then enters the jacket of the indirect dryer as a heat source for secondary use.

The technological parameter of embodiment 3-11

First of all, after the indirect drying of the washed fly ash, the moisture content of the fly ash can be reduced from 40% to below 5%, so as to facilitate the subsequent resource disposal and reduce the impact on the resource disposal equipment, thereby effectively ensuring the resource utilization of the fly ash Disposal capacity;

Second, the indirect drying method is used to reduce the moisture content in the fly ash by using the heat transfer of the partition wall. The heat source is in direct contact with the fly ash, and the generated flue gas and dust content are small, and the subsequent flue gas treatment process is relatively simple;

Third, before indirect drying, the washed fly ash (moisture content 40%) is mixed with the dried finished product ash by mixing pretreatment to reduce the moisture content of the feed to the dryer and further improve the drying efficiency , to fully ensure that the moisture content of fly ash after drying is ≤5%;

Fourth, the mixing pretreatment realizes the uniform dispersion of the material while reducing the moisture content of the feed, which is beneficial to the fluidity of the fly ash mixture in the indirect drying equipment, and can reduce the occurrence of material sticking to the wall, which is beneficial to Ensure the loose state of the material;

Fifth, the indirect drying of washed fly ash has changed the previous direct drying method of using the existing heat source of resource-based enterprises, reduced the impact on the equipment of resource-based enterprises, and is conducive to reducing the energy consumption of the entire system;

Sixth, the condensed water and secondary steam generated during the drying process are recycled to save steam consumption and improve overall economic benefits;

Seventh, the whole set of indirect drying system for washing fly ash in the present invention is equipped with temperature and flow monitoring instruments, and monitors the stability of the drying system operation through real-time online data, so as to adjust the various process control conditions in the system and fully ensure the washing process. Drying efficiency of fly ash.

The invention uses the indirect drying method to dry the washed fly ash, changes the traditional direct drying technology, reduces the generation of flue gas, reduces the dust content of the flue gas, and reduces the overall energy consumption of the system.

Claims (10)

1. A system for indirect drying of washed fly ash, characterized in that it mainly includes a mixing unit, a heat source generating unit, an indirect drying unit, a flue gas processing unit, and a finished fly ash storage unit; Wherein, the mixing unit is the inlet of the water-washed fly ash indirect drying system, the outlet of the mixing unit is connected to the feed port of the indirect drying unit, the outlet of the heat source generating unit is connected to the indirect drying unit The inlet of the heat source is connected, the dust gas outlet of the indirect drying unit is connected with the inlet of the flue gas treatment unit, the outlet of the indirect drying unit is connected with the inlet of the finished fly ash storage unit, and the finished fly ash The outlet of the storage unit is the outlet of the indirect drying system for washed fly ash. 2. A system for indirect drying of washed fly ash according to claim 1, characterized in that: the mixing unit includes a mixer and a fly ash conveying device; the mixer is provided with two feeding ports, respectively A water-washed fly ash feed port and a dry fly ash feed port, the dry fly ash and the washed fly ash are homogeneously mixed in the mixer. 3. A system for indirect drying of washed fly ash according to claim 1, characterized in that: the heat source generating unit includes a water softener, a heat source generator, a condensed water collector, and a heat exchanger; The inlet of the condensed water collector is connected to the condensed water outlet of the indirect dryer, the outlet of the condensed water collector is connected to the inlet of the heat source generator, and the inlet of the heat exchanger is connected to the flue gas The outlet of the processing unit is connected, and the outlet of the heat exchanger is connected with the jacket steam inlet of the indirect dryer; the heat exchanger performs secondary heating for the high-temperature flue gas discharged from the flue gas processing unit. 4. A system for indirect drying of washed fly ash according to claim 1, characterized in that: the indirect drying unit includes a quantitative feeder and an indirect dryer; The indirect dryer selects a rotary disc dryer, a rotary dryer, and a paddle dryer; the rotating shaft of the indirect dryer is adjustable by frequency conversion; the internal gas environment of the indirect dryer is a slight negative pressure, which is 5KPa lower than the ambient pressure The following; the indirect dryer is equipped with structural parts; the heat source of the indirect dryer is saturated steam, superheated steam or heat transfer oil. 5. A system for indirect drying of washed fly ash according to claim 1, characterized in that: the flue gas treatment unit includes a dust collector, an induced draft fan, and a monitoring instrument; The dust collector is a pulse bag filter, and the bag material of the pulse bag filter is preferably PTFE film; the monitoring instruments are temperature and pressure instruments, which are installed before and after the dust collector. 6. A system for indirect drying of washed fly ash according to claim 1, characterized in that: the finished fly ash storage unit includes a finished fly ash storage bin, a finished fly ash temporary storage bin, and a finished fly ash delivery pipeline; The entrance of the fly ash temporary storage bin is connected to the entrance of the fly ash storage bin, and the fly ash is transported to the finished fly ash storage bin and the finished fly ash temporary storage bin by a chute; the finished fly ash The temporary storage bin is reused to the mixing unit. 7. The method for indirect drying of water-washed fly ash of the system according to any one of claims 1 to 6, characterized in that: comprising the following steps ① Mixing preparation: the washed fly ash is transported to the washed fly ash inlet of the mixer, the dry fly ash in the fly ash temporary storage bin is transported to the dry fly ash inlet of the mixer by a screw conveyor, and the washed fly ash is mixed with water in the mixer. Dried fly ash is stirred and mixed; ②Equipment preheating: turn on the tap water switch, and enter the heat source generator after being softened by the water softener. Then, the saturated steam generated is transported to the heat source inlet of the indirect dryer through the insulation pipeline to preheat the indirect dryer; ③Indirect drying: After the heat source preheats the indirect dryer, the fly ash mixed in step ① is conveyed to the feed port of the indirect dryer by a screw, and the material moves to the discharge end through the rotation of the inner rotary table of the dryer. In this process, the moisture content of the fly ash is reduced by contacting the partition wall of the heat source to achieve the purpose of reducing the moisture content of the fly ash. In addition, there are structural parts inside the dryer, which can effectively prevent the fly ash from sticking to the wall and clumping together, which is conducive to maintaining the uniformity and smoothness of the fly ash discharge. degree of looseness; at the same time, the condensed water discharged from the indirect dryer enters the condensed water collector for recycling; ④ Fly ash storage: The dried material in step ③ is transported to the finished fly ash storage bin and the finished fly ash temporary storage bin through the discharge end; among them, the fly ash in the finished fly ash storage bin is used for subsequent resource disposal and utilization, and the finished product The fly ash in the fly ash temporary storage bin is returned to the mixing unit for recycling; ⑤ Flue gas treatment: In step ③, the wet flue gas generated inside the indirect dryer enters the flue gas treatment unit, and the dust is removed by the bag filter to ensure that the particle concentration in the flue gas is ≤10mg/m ³ ; among them, before the bag filter , The rear end is equipped with temperature and pressure monitoring instruments, through data monitoring, to prevent condensation of wet flue gas, causing blockage of the bag filter; the fly ash collected by the bag filter enters the finished fly ash storage bin; ⑥Residual heat utilization: After the high-temperature flue gas after dedusting in step ⑤ is reheated by the heat exchanger, it can be used as a heat source again in the jacket of the indirect dryer for secondary use. 8. The method for indirect drying of washed fly ash according to claim 7, characterized in that, in the step ①, the moisture content of the mixed material is reduced to 10%-30% in the mixer, and the material mixing time is 2-3min. 9. The method for indirect drying of washed fly ash according to claim 7, characterized in that the condition of saturated steam in the step ② is 0.5-0.8 MPa. 10. The method for indirect drying of washed fly ash according to claim 7, characterized in that the moisture content of the fly ash after drying in step ③ is ≤5%, and the drying time can be set to 1.5-2.5 hours.

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