A process system and method for directly drying sludge by using hot flue gas of incinerating sludge

Abstract

The application discloses a process method for directly drying sludge by using hot flue gas of sludge incineration, and a process system used mainly comprises a sludge incinerator, a sludge dryer, a drying tower, a dust removal system, a flue gas condensing tower, a regenerative thermal incinerator 10, a wet deacidification tower, a cold flue reheater and a chimney. The sludge is dried by using the hot flue gas generated by the sludge incineration, the dried sludge is incinerated again, the flue gas waste heat is utilized and discharged, the synchronous disposal of the sludge drying and incineration is realized, the sludge dryer is a rotary gas flow bed dryer, the sludge does not need to be crushed, granulated, made into strips or atomized by a nozzle, and the types of equipment are simplified. By adopting partial flue gas backflow, the flue gas emission and waste heat loss are reduced; the sludge drying process is operated under high humidity airflow, the oxygen content is not increased in the drying process, and the possibility of sludge explosion in the drying process is reduced. The regenerative thermal incinerator is used for removing VOCs and CO, and the problem of flue gas exceeding the standard caused by the sludge drying is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to a process system and method for drying sludge, in particular to a system and method for drying sludge by using hot flue gas generated by incinerating sludge, incinerating dried sludge, and utilizing and discharging flue gas waste heat in stages. BACKGROUND

[0002] At present, the mainstream way of sludge drying and incineration system is to use the waste heat after sludge incineration to heat the waste heat boiler, and the waste heat boiler generates steam by fuel supplementing heat, and then the steam is used to dry the sludge. The dried sludge is then incinerated in the incinerator, and the hot flue gas generated by incineration is discharged after reaching the standard through the flue gas treatment device. The above treatment method needs to supplement a large amount of heat source to make the waste heat boiler generate steam, and the waste heat boiler needs to be provided with a set of water treatment and flue gas system, in addition to the steam-water pipe system. The system has low thermal efficiency and a large number of equipment types.

[0003] The patent document with publication date of January 28, 2015 and publication number CN104310746A discloses a method for drying and incinerating dewatered sludge. The technical solution uses a spray drying tower to atomize the sludge. The sludge is pressurized by a pump and then atomized by a nozzle for gas-solid drying. The sludge pressurizing pump has high power consumption, and the nozzle is severely worn. The sludge with poor fluidity needs to be added with water for atomization, which directly causes a large increase in drying heat consumption and requires secondary drying. The equipment types are relatively large. Since the flue gas after drying the sludge does not pass through the incinerator, and CO is carried in the flue gas, no measures are proposed for treating CO in the flue gas.

[0004] The patent document with publication date of June 8, 2016 and publication number CN105645733A discloses a sludge drying and incineration system and an incineration process thereof. The technical solution uses hot air after heat exchange of hot flue gas generated by the incinerator to dry the sludge (the hot flue gas is reduced from 800℃ to 220-300℃). The waste heat of the flue gas is not fully utilized, the system has low thermal efficiency, and the sludge needs to be granulated before drying, which limits the range of water content of the sludge (60-70%). The flue gas after drying the sludge does not pass through the incinerator, and the composition of the flue gas is complex. In addition, no specific flue gas treatment measures are proposed in the technical solution.

[0005] Therefore, in order to fully utilize the waste heat resources, maximize the system thermal efficiency, reduce the auxiliary fuel consumption and the cost of direct incineration of municipal sludge, it is necessary to improve the flue gas treatment system according to the process requirements, and comprehensively control the emission of harmful gases such as nitrogen oxides, acid gases, VOCs (volatile organic compounds), and CO (carbon monoxide). SUMMARY

[0006] In view of the prior art, the present application provides a system for directly drying sludge by using hot flue gas of incinerated sludge, which can realize synchronous disposal of sludge drying and incineration, and can solve the problem of excessive volatile organic compounds and carbon monoxide in flue gas caused by post-drying of sludge by adding a regenerative thermal incinerator device in the process flow.

[0007] In order to solve the above technical problems, the present application provides a process system for directly drying sludge by using hot flue gas of incinerated sludge, which comprises a sludge incinerator, a sludge dryer, a dust removal system, a wet deacidification tower, a cold smoke reheater and a chimney, wherein the sludge incinerator is provided with a high-temperature separator; the process system further comprises a drying tower, a flue gas condensation tower and a regenerative thermal incinerator; the flue gas condensation tower comprises a flue gas temperature reducer and a flue gas condenser connected in series; the sludge dryer is a rotary gas flow bed dryer, which comprises a drying main cylinder, wherein a stirring pushing rod is arranged in the drying main cylinder, and the sludge is stirred and broken by the stirring pushing rod after entering the drying main cylinder; the high-temperature flue gas generated by the sludge incinerator is separated by the high-temperature separator and then enters the drying main cylinder through pipeline A to heat the sludge at high temperature, so as to realize rapid and uniform drying of the sludge, and the sludge moves to a sludge discharge port under the pushing of the stirring pushing rod; the sludge discharge port is connected to the drying tower, the outlet of the drying tower is connected to the inlet of the dust removal system, and the dust removal system comprises multiple dust collectors connected in series; the sludge outlet of each dust collector is connected to the inlet of a dry sludge scraper conveyor, and the outlet of the dry sludge scraper conveyor is connected to the inlet of the sludge incinerator; the flue gas outlet of the last-stage dust collector is connected to the flue gas condenser through the flue gas temperature reducer; the flue gas temperature reducer and the cold smoke reheater are connected by a heat conduction oil pipeline for heat exchange circulation; the outlet pipeline of the flue gas condenser is divided into two paths by a pipe joint, one path is connected to pipeline A through a flue gas backflow pipeline C, and the other path is connected to the regenerative thermal incinerator through pipeline B; the flue gas outlet of the regenerative thermal incinerator is connected to the wet deacidification tower, and the flue gas after deacidification treatment is heated by the cold smoke reheater and then discharged into the atmosphere through the chimney.

[0008] Further, the process system provided by the present application comprises the following:

[0009] The sludge incinerator is a bubbling fluidized bed incinerator, and the sludge incinerator is provided with an SNCR denitration device and a desulfurization device.

[0010] The dust removal system is a two-stage dust removal system composed of a cyclone dust collector and a bag dust collector connected in series, or a three-stage dust removal system composed of a cyclone dust collector, an electrostatic precipitator and a bag dust collector connected in series.

[0011] Meanwhile, the present application also provides a process method for directly drying sludge by using hot flue gas of incinerated sludge by using the above process system, which comprises the following steps:

[0012] Step 1, sludge drying

[0013] The dewatered sludge with water content of 60% to 80% from municipal sewage treatment plant is transported into the sludge drying machine by the conveyor, and at the same time, the sludge incinerator is started. In the sludge drying machine, the dewatered sludge is stirred and broken by the stirring push rod, and the high-temperature flue gas with a temperature of > 850℃ provided by the sludge incinerator contacts and fuses with the broken sludge, and the water in the sludge is evaporated through heat exchange to form small pieces of sludge which move to the sludge discharge port under the pushing of the stirring push rod. At the same time, in the sludge drying machine, the high-temperature flue gas becomes wet flue gas with a temperature of 150-160℃ within 2s, and then the wet flue gas carrying semi-dry sludge is discharged into the drying tower;

[0014] Step 2, semi-dry sludge backflow incineration

[0015] The semi-dry sludge after the drying tower has a water content of 25-35%, and the semi-dry sludge discharged from the drying tower enters the dust removal system and is incinerated in the sludge incinerator through dust removal and collection by the dry sludge scraper conveyor. The sludge incinerator is a bubbling fluidized bed incinerator, and the sludge incinerator is provided with an SNCR denitration device and a desulfurization device. In the sludge incinerator, dry desulfurization is carried out by limestone powder spray gun in the desulfurization device, and denitration is carried out by low-oxygen backflow wind low-nitrogen combustion. During the incineration process, according to the temperature detection device in the sludge incinerator, the combustion temperature in the sludge incinerator is controlled at 870-970℃ by adjusting the air supply and the output of auxiliary fuel. At the same time, the high-temperature separator carries out gas-solid separation, and the unburned sludge backflows to the sludge incinerator, and the burned ash is collected by the cold slag machine to the ash storage, and the separated high-temperature flue gas is discharged into the sludge drying machine;

[0016] Step 3, flue gas dust removal: the wet flue gas discharged from the drying tower enters the dust removal system, and according to the different structures of the dust removal system, the dust removal process is one of the following two situations:

[0017] One is that the dust removal system is a two-stage dust removal system composed of a cyclone dust collector and a bag dust collector connected in series. The process of flue gas dust removal is: the wet flue gas entering the two-stage dust removal system is first subjected to solid-gas separation by the cyclone dust collector, and the wet flue gas after preliminary dust removal by the cyclone dust collector enters the flue gas before the bag dust collector, and activated carbon is injected into the flue gas. The activated carbon enters the bag dust collector with the wet flue gas for dust removal treatment, and the activated carbon absorbs heavy metals and dioxins during the dust removal treatment. The dust collected by the bag dust collector and the used activated carbon are collected into the hazardous waste warehouse; the wet flue gas after dust removal treatment is discharged into the flue gas temperature reducer;

[0018] Secondly, the dust removal system is a three-stage dust removal system composed of a cyclone dust collector, an electrostatic dust collector and a bag dust collector connected in series; the process of flue gas dust removal is that the wet flue gas entering the three-stage dust removal system is firstly subjected to solid-gas separation by the cyclone dust collector, the wet flue gas after preliminary dust removal by the cyclone dust collector enters the electrostatic dust collector for flue gas purification and dust and gas separation; the wet flue gas after dust removal by the electrostatic dust collector enters the flue before the bag dust collector, and activated carbon is sprayed into the flue, the activated carbon enters the bag dust collector with the wet flue gas for dust removal treatment, in the dust removal treatment process, the activated carbon absorbs heavy metals and dioxins, and the dust collected by the bag dust collector and the used activated carbon are collected into a hazardous waste bin; the wet flue gas after dust removal treatment is discharged into the flue gas temperature reducer;

[0019] Step 4, flue gas condensation: the wet flue gas after dust removal treatment in step 3 is subjected to temperature reduction to 115±5℃ by the flue gas temperature reducer, and then enters the flue gas condensation tower for gas-liquid separation, the separated water is treated by a sewage treatment system and discharged after reaching the standard; a part of the separated flue gas is recycled to the sludge dryer through a flue gas return pipeline C for recycling, and the other part of the separated flue gas enters the regenerative thermal incinerator; the regenerative thermal incinerator comprises two regenerative chambers and a combustion chamber;

[0020] Step 5: removal of VOCs and CO in flue gas: the flue gas entering the regenerative thermal incinerator is preheated by one of the regenerative chambers and then enters the combustion chamber, and is heated to 760-800℃, so that VOCs and CO in the flue gas are oxidized into CO2 and H2O; the high-temperature flue gas generated in the oxidation process releases heat through the other regenerative chamber until the temperature is 115±5℃, and then is discharged from the regenerative thermal incinerator to the wet flue gas desulfurization tower;

[0021] Step 6, wet flue gas desulfurization: the wet flue gas desulfurization tower adopts a solution circulation mode outside the tower, and the solution is caustic soda or lye; the flue gas discharged from the regenerative thermal incinerator enters the wet flue gas desulfurization tower and contacts with the sprayed solution, so that the acid substances in the flue gas are removed, and the temperature of the flue gas is reduced to 50℃±5℃ at this time;

[0022] Step 7, flue gas discharge: the flue gas treated by the wet flue gas desulfurization tower is heated to 98℃±5℃ by the cold flue reheater, and then is discharged into the atmosphere through a chimney at a high altitude.

[0023] Further, the process method of the application, wherein a flow valve is arranged at the pipe joint of the outlet pipeline of the flue gas condenser, for controlling the flue gas return flow, and the flue gas return flow accounts for 20% of the total air volume.

[0024] Compared with the prior art, the application has the following beneficial effects:

[0025] (1) The technical scheme of the present application synchronously disposes sludge drying and incineration, adopts a rotary gas flow bed drier, does not need to crush, granulate, make strips, and nozzle atomize the sludge, has no requirement on the fluidity of the sludge, simplifies the types of equipment, can accept the dewatered sludge with a water content of 30-80% of the municipal sewage treatment plant, has a wide disposal range, has high system thermal efficiency, and has few types of equipment.

[0026] (2) The system thermal transfer efficiency is greatly improved by directly drying the sludge by using the hot flue gas of incinerated sludge; the auxiliary fuel addition amount can be maximally reduced, and the disposal cost of the municipal sludge direct incineration is reduced.

[0027] (3) The flue gas treatment system is improved according to process requirements, part of the flue gas is returned, the drying flue gas amount > the incineration flue gas amount = the flue gas emission amount, the waste heat resource is fully utilized, the system thermal efficiency is maximally improved, the flue gas treatment system load is reduced, the flue gas emission amount and waste heat loss are reduced; the sludge is operated under high humidity gas flow, and the oxygen content is not increased in the drying process, so that the possibility of sludge deflagration in the drying process is reduced.

[0028] (4) In view of the fact that the flue gas contains not only nitrogen oxides and acid gases, but also CO gas and VOCs generated by incomplete combustion of the flue gas, the heat accumulating type thermal incinerator is introduced to remove VOCs and CO, and the flue gas treatment system is further improved. The harmful gas emissions such as nitrogen oxides, acid gases, VOCs (volatile organic compounds), and CO (carbon monoxide) are comprehensively controlled. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is the process flow diagram for directly drying sludge by using the hot flue gas of incinerated sludge according to the present application;

[0030] Figure 2 It is the equipment schematic diagram for realizing the process flow shown in the figure; Figure 1

[0031] In the figure:

[0032] 1-sludge incinerator 2-high temperature separator 201-cold slag machine

[0033] 202-ash storage 3-sludge drier 301-sludge feeding hopper

[0034] 4-drying tower 5-cyclone dust collector 6-electrostatic precipitator

[0035] 7-bag-type dust collector 701-dry sludge scraper conveyor 702-hazardous waste bin

[0036] 703-bag bottom conveyor 8-flue gas temperature reducer 9-flue gas condensation tower

[0037] 10-heat accumulating type thermal incinerator 11-wet method acid removal tower 12-cold smoke reheater​

[0038] 13 - chimney DETAILED DESCRIPTION

[0039] The application will be further described below in connection with the drawings and specific examples, but the following examples are by no means limiting to the application.

[0040] As shown in the drawings, Figure 2 The process system for directly drying sludge by using hot flue gas of incinerated sludge is provided by the application, which comprises a sludge incinerator 1, a sludge dryer 3, a drying tower 4, a dust removal system, a flue gas condensing tower, a regenerative thermal incinerator 10, a wet deacidification tower 11, a cold flue reheater 12 and a chimney 13.

[0041] The sludge incinerator is a bubbling fluidized bed incinerator, the main body is a circular tower body, a distribution plate for distributing gas is arranged at the lower part, the tower is lined with refractory material and is provided with heat-resistant granular carriers, gas is introduced from the lower part and passes through the distribution plate at a certain speed, so that the carriers in the bed are bubbled to be in a fluidized state, sludge is added from the side or the top of the tower, and after drying, crushing, gasification and other processes in the bubbling furnace layer, the sludge is rapidly burned. At the same time, the sludge incinerator 1 is provided with a high-temperature separator 2, an SNCR denitration device and a desulfurization device; the high-temperature separator 2 is used to separate fly ash in high-temperature flue gas, and the ash produced by the sludge incinerator 1 and the high-temperature separator 2 is transported to an ash storage 202 through a cold slag machine 201 for storage. The SNCR device comprises a lance and an ammonia water or urea storage and transportation system outside the furnace, and denitration is performed through the lance; the desulfurization device comprises a limestone powder lance, a lime bin and a conveying device.

[0042] The sludge dryer 3 is a rotary gas flow bed dryer, and the rotary gas flow bed dryer used in the application has the drying principle as follows: the rotary gas flow bed dryer adopts gas-solid parallel flow operation, the drying time is generally 0.5-2 seconds, the thermal denaturation of the material is generally a function of temperature and time, and therefore, for heat-sensitive or low-melting-point materials, overheating or decomposition will not affect the quality. In the surface gasification stage, the material is always at the wet bulb temperature of the gas in contact with it, which is generally not more than 50-65 DEG C, in the material temperature rising stage at the end of the drying, the gas temperature has been greatly reduced, and the material temperature will not exceed 60-90 DEG C, and the drying waste gas temperature is lower than 160 DEG C. The rotary gas flow bed dryer comprises a drying main cylinder, wherein a stirring pushing rod is arranged in the drying main cylinder, the sludge enters the drying main cylinder and is stirred and broken by the stirring pushing rod, the 850 DEG C high-temperature flue gas generated by the front-end sludge incinerator 1 enters the drying main cylinder through pipeline A after being separated by the high-temperature separator 2, high-temperature heating is performed on the sludge in the sludge dryer 3, the rapid and uniform drying of the sludge is realized, and the sludge moves to the sludge discharge port under the pushing of the stirring pushing rod; at the same time, the hot flue gas becomes wet flue gas after heating the sludge, the temperature is reduced to about 160 DEG C, and the wet flue gas is discharged through the outlet.

[0043] The sludge discharge port is connected to the drying tower 4, and the drying tower 4 is used to increase the drying time of the sludge. The outlet of the drying tower 4 is connected to the inlet of a dust removal system, and the dust removal system comprises a plurality of dust collectors connected in series; in the application, the dust removal system is a two-stage dust removal system composed of a cyclone dust collector 5 and a bag dust collector 7 connected in series, or a three-stage dust removal system composed of a cyclone dust collector 5, an electrostatic dust collector 6 and a bag dust collector 7 connected in series, and the sludge outlet of each dust collector is connected to the feeding port of a dry sludge scraper conveyor 701, and the outlet of the dry sludge scraper conveyor 701 is connected to the feeding port of the sludge incinerator 1. Figure 2 The dust removal system shown in the figure is a three-stage dust removal system, and the semi-dry sludge is discharged from the lower part of the cyclone dust collector 5, the electrostatic dust collector 6 and the bag dust collector 7, and is returned to the sludge incinerator 1 through the dry sludge scraper conveyor 701 and the bag dust collector bottom conveyor 703 for incineration; the fly ash generated by the bag dust collector 7 enters the hazardous waste warehouse 702 for storage through the bag bottom conveyor 703.

[0044] The flue gas outlet of the last stage dust remover is connected to the flue gas condensing tower, which comprises a flue gas temperature reducer 8 and a flue gas condenser 9 connected in series. In the present application, the flue gas temperature reducer 8 is connected to the cold smoke reheater 12 through a heat conduction oil pipeline for heat exchange circulation. The outlet pipeline of the flue gas condenser 9 is divided into two paths through a pipe joint, one path is connected to pipeline A through a flue gas return pipeline C, and the other path is connected to the regenerative thermal incinerator 10 through pipeline B. A flow valve is arranged at the pipe joint of the outlet pipeline of the flue gas condenser 9 for controlling the flue gas return flow into the flue gas return pipeline C. In the present application, the flue gas return flow accounts for 20% of the total air volume. After being cooled, the flue gas enters the flue gas condensing tower 9 to condense and remove part of the water, and then part of the flue gas returns to the sludge dryer 3 through the flue gas return pipeline C for recycling, and the other part of the flue gas enters the regenerative thermal incinerator 10 through pipeline B to remove volatile organic compounds VOCs and carbon monoxide CO. The flue gas outlet of the regenerative thermal incinerator 10 is connected to the wet deacidification tower 11. The flue gas enters the wet deacidification tower 11 to remove acid gases. After deacidification treatment, the flue gas enters the cold smoke reheater 12, is heated, and is then discharged into the atmosphere through the chimney 13.

[0045] The regenerative thermal incinerator 10 in the present application mainly comprises a regenerative chamber, a combustion chamber and an air flow switching valve. The regenerative chamber is filled with ceramic regenerative bodies, and the combustion chamber is provided with a burner with proportional adjustment. There are six states of pre-blowing, ignition, temperature rising, incineration, temperature keeping and post-blowing shutdown. VOCs are first preheated in the regenerative chamber, and then enter the combustion chamber to be heated and raised to about 800 DEG C, so that VOCs are oxidized and decomposed into CO2 and H2O, and CO is oxidized to CO2 in the combustion chamber; the high-temperature flue gas generated after oxidation releases heat through another regenerative chamber, and then is discharged from the regenerative thermal incinerator 10 system. The process is continuously cycled and alternated, thereby effectively reducing the heat emission after waste gas treatment, saving the heat loss during the oxidation and temperature rising of the waste gas, keeping a high thermal efficiency of the whole system during the high-temperature oxidation of the waste gas, and solving the problem of excessive VOCs and CO concentration in the flue gas caused by direct contact between the flue gas and the dried sludge.

[0046] As shown in Figure 1 In the present application, the above-mentioned process system is used to realize the process method of directly drying sludge by burning sludge hot flue gas. The basic path of the flue gas is: generated in the sludge incinerator → sludge dryer → drying tower → dust removal system → flue gas condensing tower → cold smoke reheater → chimney. The basic path of the sludge is: 80% moisture content sludge first enters the sludge dryer from the sludge feeding hopper → drying tower (semi-dry sludge, moisture content 25-35%) → dust removal system (semi-dry sludge) → dry sludge conveyor (semi-dry sludge) → sludge incinerator (with a high-temperature separator to improve the combustion condition) → ash. The specific steps are as follows:

[0047] Step 1, sludge drying

[0048] The dewatered sludge with water content of 60% to 80% from the municipal sewage plant is transported to the sludge dryer 3 by the conveyor, and at the same time, the sludge incinerator 1 is started; the dewatered sludge is stirred and broken by the stirring push rod on the rotor in the sludge dryer 3, the initial high-temperature flue gas of >850℃ provided by the sludge incinerator 1 contacts and fuses with the broken sludge, and the sludge is heated at high temperature, and the water in the sludge is evaporated through heat exchange, so as to facilitate the rapid and uniform drying of the sludge. The broken sludge becomes small pieces of sludge with water, which is easy to boil, and is pushed by the stirring push rod to move uniformly to the sludge discharge port at a certain speed. After the sludge is heated by the hot flue gas in the sludge dryer 3, a large amount of water vapor is mixed, and the hot flue gas in the sludge dryer 3 is rapidly cooled by the sludge, and becomes wet flue gas with a temperature of 150-160℃ within 2s, thereby reducing the generation of dioxin. Due to the high flow rate of the wet flue gas, the semi-dry sludge is blown into the drying tower 4 for further drying, that is, the wet flue gas carrying the semi-dry sludge is discharged into the drying tower 4, and subsequent semi-dry sludge reflux incineration and flue gas treatment and discharge are carried out.

[0049] Step 2, semi-dry sludge reflux incineration

[0050] After being treated by the drying tower 4, the water content of the semi-dry sludge is 25-35%, and the semi-dry sludge is blown to the dust removal system due to water loss, and then falls to the bottom of the dust removal system and is transported back to the sludge incinerator by the dry sludge conveyor 701 for further incineration, as shown in Figure 2 Taking the three-stage dust removal system as an example, the semi-dry sludge is discharged from the lower part of the cyclone dust collector 5, the electrostatic precipitator 6, and the bag dust collector 7, and is incinerated in the sludge incinerator 1 by the dry sludge scraper conveyor 701 and the bag dust collector bottom conveyor 703; the fly ash generated by the bag dust collector 7 is stored in the hazardous waste warehouse 702 through the bag dust collector bottom conveyor 703.

[0051] In this embodiment, the sludge incinerator 1 is a bubbling fluidized bed incinerator, and the SNCR denitration device and the desulfurization device are arranged in the sludge incinerator 1. The sludge incinerator 1 uses fossil energy such as natural gas and fuel oil as auxiliary fuel, and the semi-dry sludge enters the sludge incinerator 1 for incineration. In the dense phase zone of the boiling section of the incinerator, the auxiliary fuel is mixed with the semi-dry sludge with water content of about 25-35% from the semi-dry sludge dryer 3, and the mixture is boiled and combusted by the primary air. In the dilute phase zone of the incinerator, the secondary air is added to disturb the flue gas in the furnace to enhance combustion. The flue gas generated by the incinerator at a temperature of 870-970°C reaches a reasonable residence time (more than 2s) and an excess air system (oxygen content of flue gas is 6-12%) to burn the mixed combustible and reduce the generation of dioxin. The limestone powder spray gun in the desulfurization device is used for in-furnace dry desulfurization in the sludge incinerator 1, and the SNCR (selective non-catalytic reduction) spray gun (ammonia water or urea solution) is used for in-furnace denitration by low-oxygen backflow air and low-nitrogen combustion. During the incineration process, the combustion temperature in the sludge incinerator 1 is controlled in the range of 870-970°C by adjusting the air supply and the output of auxiliary fuel according to the temperature detection device in the sludge incinerator 1. At the same time, the high-temperature separator 2 performs gas-solid separation, the unburned sludge is backflowed to the sludge incinerator 1, the burned ash is collected by the cold ash machine 201 to the ash storage 202, and the separated high-temperature flue gas is discharged to the sludge dryer 3.

[0052] Step 3, flue gas dust removal

[0053] The wet flue gas discharged from the drying tower 4 enters the dust removal system. According to different structures of the dust removal system, the dust removal process is one of the following two cases:

[0054] One is that the dust removal system is composed of a two-stage dust removal system of a cyclone dust collector 5 and a bag dust collector 7 connected in series. The process of flue gas dust removal is that the wet flue gas entering the two-stage dust removal system first undergoes solid-gas separation in the cyclone dust collector 5. The wet flue gas after preliminary dust removal in the cyclone dust collector 5 enters the flue before the bag dust collector 7, and activated carbon is sprayed into the flue. The activated carbon enters the bag dust collector 5 with the wet flue gas for dust removal treatment. During the dust removal treatment, the activated carbon absorbs heavy metals and dioxin. The dust collected by the bag dust collector 7 and the used activated carbon are collected to the hazardous waste bin 702. The wet flue gas after dust removal treatment is discharged to the flue gas temperature reducer 8.

[0055] Secondly, the dedusting system is a three-stage dedusting system composed of a cyclone dust collector 5, an electrostatic dust collector 6 and a bag dust collector 7 connected in series. The process of flue gas dedusting is as follows: the wet flue gas entering the three-stage dedusting system is firstly subjected to solid-gas separation in the cyclone dust collector 5, the wet flue gas after the preliminary dedusting in the cyclone dust collector 5 enters the electrostatic dust collector 6 for flue gas purification and dust-gas separation; the wet flue gas after the dedusting in the electrostatic dust collector 6 enters the flue before the bag dust collector 7, and activated carbon is sprayed into the flue, the activated carbon enters the bag dust collector 5 with the wet flue gas for dedusting treatment, in which the activated carbon absorbs heavy metals and dioxins, and the dust collected by the bag dust collector 7 and the used activated carbon are collected into the hazardous waste bin 702; the wet flue gas after the dedusting treatment is discharged into the flue gas temperature reducer 8.

[0056] The present embodiment takes the three-stage dedusting system as an example to describe the dedusting process.

[0057] The wet flue gas (150-160℃) after the sludge incinerator 1 and the sludge dryer 3 enters the cyclone dust collector 5, and the centrifugal force and gravity acting on the particles are used to separate solid and liquid particles from the airflow.

[0058] The wet flue gas (150-160℃) after the preliminary dedusting in the cyclone dust collector 5 enters the electrostatic dust collector 6, and the dust particles in the wet flue gas are charged (or charged in the ion diffusion motion) by colliding with positive and negative ions and electrons between the electrodes when passing through the high-voltage electrostatic field, and the dust particles with electrons and ions are moved to the heterogeneous electrode under the action of the electric field force and are adsorbed on the heterogeneous electrode, so that the wet flue gas passing through the electrostatic dust collector 6 is purified by means of vibration and other methods. The dust particles with different polarities are moved to different polarity electrodes under the action of the electric field force, and are deposited on the electrodes, so as to separate the dust and the gas.

[0059] The temperature of the wet flue gas after the treatment in the electrostatic dust collector 6 is reduced to 142-152℃, and then the wet flue gas enters the flue before the bag dust collector 7, activated carbon is sprayed into the flue before the bag dust collector 7, the activated carbon enters the bag dust collector with the flue gas for dedusting treatment, the activated carbon absorbs heavy metals and dioxins, and the dust and activated carbon collected by the bag dust collector 7 are hazardous waste, which are collected into the separate hazardous waste bin 702.

[0060] Step 4, flue gas condensation

[0061] The flue gas after the dedusting treatment in step 3 is cooled to 115±5℃ by the flue gas cooler 8, and then enters the flue gas condensing tower 9 for gas-liquid separation. The separated water is treated by a sewage treatment system and discharged after reaching the standard. Part of the separated flue gas is recycled to the sludge dryer 3 through the flue gas return pipeline C for recycling, and the other part of the separated flue gas enters the regenerative thermal incinerator 10. The regenerative thermal incinerator 10 comprises two regenerative chambers and a combustion chamber.

[0062] Step 5: removing VOCs and CO from the flue gas

[0063] The flue gas entering the regenerative thermal incinerator 10 is preheated by one of the regenerative chambers and then enters the combustion chamber, and is heated to 760-800℃, so that the VOCs and CO in the flue gas are oxidized into CO2 and H2O. The high-temperature flue gas generated in the oxidation process releases heat through the other regenerative chamber until the temperature is 115±5℃, and then is discharged from the regenerative thermal incinerator 10 to the wet deacidification tower 11.

[0064] Step 6: wet deacidification of the flue gas

[0065] The wet deacidification tower 11 adopts a solution circulation mode outside the tower, and the solution is caustic soda or lye. The flue gas discharged from the regenerative thermal incinerator 10 enters the wet deacidification tower 11 and contacts with the sprayed solution to remove SO2 and other acidic substances in the flue gas, and at this time the temperature of the flue gas is reduced to 50℃±5℃.

[0066] Step 7: flue gas discharge

[0067] The flue gas treated by the wet deacidification tower 11 is heated to 98℃±5℃ by the cold flue gas reheater 12, and then is discharged into the atmosphere through the chimney 13. The heat source of the cold flue gas reheater 12 comes from the flue gas cooler 8.

[0068] Although the present application has been described above with reference to the accompanying drawings, the present application is not limited to the specific embodiments described above, which are merely illustrative and not restrictive. Those skilled in the art can make many modifications to the present application without departing from the spirit of the present application, and these modifications are all within the scope of the present application.

Claims

1. A process system for directly drying sludge by using hot flue gas of sludge incineration, comprising a sludge incinerator (1), a sludge dryer (3), a dust removal system, a wet deacidification tower (11), a cold flue gas reheater (12) and a chimney (13), wherein a high-temperature separator (2) is arranged in the sludge incinerator (1); characterized in that: the process system further comprises a drying tower (4), a flue gas condensation tower and a regenerative thermal incinerator (10); the flue gas condensation tower comprises a flue gas temperature reducer (8) and a flue gas condenser (9) connected in series; the sludge dryer (3) is a rotary fluidized bed dryer, which comprises a drying main cylinder, wherein a stirring push rod is arranged in the drying main cylinder, and the sludge is stirred and broken by the stirring push rod after entering the drying main cylinder; the high-temperature flue gas generated by the sludge incinerator (1) is separated by the high-temperature separator (2) and then enters the drying main cylinder through pipeline A to heat the sludge at high temperature, thereby realizing rapid and uniform drying of the sludge, and the sludge moves to a sludge discharge port under the pushing of the stirring push rod; the sludge discharge port is connected to the drying tower (4), the outlet of the drying tower (4) is connected to the inlet of the dust removal system, and the dust removal system comprises multiple dust collectors connected in series; the sludge outlet of each dust collector is connected to the inlet of a dry sludge scraper conveyor (701), and the outlet of the dry sludge scraper conveyor (701) is connected to the inlet of the sludge incinerator (1); the flue gas outlet of the last-stage dust collector is connected to the flue gas condenser (9) after passing through the flue gas temperature reducer (8); the flue gas temperature reducer (8) and the cold flue gas reheater (12) are connected by a heat conduction oil pipeline for heat exchange circulation; the outlet pipeline of the flue gas condenser (9) is divided into two paths by a pipe joint, one path is connected to the pipeline A through a flue gas recirculation pipeline C, and the other path is connected to the regenerative thermal incinerator (10) through a pipeline B; the flue gas outlet of the regenerative thermal incinerator (10) is connected to the wet deacidification tower (11), and the flue gas after deacidification treatment is heated by the cold flue gas reheater (12) and then discharged into the atmosphere through the chimney (13). The sludge incinerator (1) is a bubbling fluidized bed incinerator, which is provided with an SNCR denitration device and a desulfurization device. The dust removal system is a two-stage dust removal system composed of a cyclone dust collector (5) and a bag dust collector (7) connected in series. The dust removal system is a three-stage dust removal system composed of a cyclone dust collector (5), an electrostatic precipitator (6) and a bag dust collector (7) connected in series. The process system of claim 1 is used, and the following steps are included: Step 1, sludge drying ​ 2. The process system of claim 1, wherein: ​ 3. The process system of claim 1, wherein: ​ 4. The process system of claim 1, wherein: ​ 5. A process for direct drying of sewage sludge using hot flue gases from incineration of sewage sludge, characterized in that, ​ ​ The municipal sewage plant dewatered sludge with water content of 60% to 80% is transported to the sludge drying machine (3) by the conveyor, and at the same time, the sludge incinerator (1) is started. In the sludge drying machine (3), the dewatered sludge is stirred and broken by the stirring push rod, and the high-temperature flue gas with a temperature of >850℃ provided by the sludge incinerator (1) contacts and fuses with the broken sludge, and the water in the sludge is evaporated through heat exchange to form small pieces of sludge which move to the sludge discharge port under the pushing of the stirring push rod. At the same time, in the sludge drying machine (3), the high-temperature flue gas becomes wet flue gas with a temperature of 150-160℃ within 2s, and then the wet flue gas carrying semi-dry sludge is discharged into the drying tower (4); Step 2, semi-dry sludge backflow incineration The semi-dry sludge after the drying tower (4) has a water content of 25-35%, and the semi-dry sludge discharged from the drying tower (4) enters the dust removal system and is incinerated in the sludge incinerator (1) through dust removal collection by the dry sludge scraper conveyor (701). The sludge incinerator (1) is a bubbling fluidized bed incinerator, and the sludge incinerator (1) is provided with an SNCR denitration device and a desulfurization device. In the sludge incinerator (1), dry desulfurization is carried out by limestone powder spray gun in the desulfurization device, and denitration is carried out by low-oxygen backflow wind low-nitrogen combustion. During the incineration process, according to the temperature detection device in the sludge incinerator (1), the combustion temperature in the sludge incinerator (1) is controlled at 870-970℃ by adjusting the air supply and the output of auxiliary fuel. At the same time, the high-temperature separator (2) carries out gas-solid separation, and the unburned sludge backflows to the sludge incinerator (1), and the burned ash is collected by the cold slag machine (201) to the ash storage (202), and the separated high-temperature flue gas is discharged into the sludge drying machine (3); Step 3, flue gas dust removal The wet flue gas discharged from the drying tower (4) enters the dust removal system, and according to the different structures of the dust removal system, the dust removal process is one of the following two situations: One is that the dust removal system is a two-stage dust removal system composed of a cyclone dust collector (5) and a bag dust collector (7) connected in series. The process of flue gas dust removal is: the wet flue gas entering the two-stage dust removal system first passes through the solid-gas separation of the cyclone dust collector (5), and the wet flue gas after the preliminary dust removal of the cyclone dust collector (5) enters the flue before the bag dust collector (7), and activated carbon is sprayed into the flue. The activated carbon enters the bag dust collector (5) with the wet flue gas for dust removal treatment, and the activated carbon absorbs heavy metals and dioxins during the dust removal treatment. The dust collected by the bag dust collector (7) and the used activated carbon are collected into the hazardous waste warehouse (702). The wet flue gas after dust removal treatment is discharged into the flue gas desuperheater (8); Secondly, the dust removal system is a three-stage dust removal system composed of a cyclone dust collector (5), an electrostatic dust collector (6) and a bag dust collector (7) connected in series; the process of flue gas dust removal is as follows: the wet flue gas entering the three-stage dust removal system is first subjected to solid-gas separation in the cyclone dust collector (5), the wet flue gas after preliminary dust removal in the cyclone dust collector (5) enters the electrostatic dust collector (6) for flue gas purification and dust and gas separation; the wet flue gas after dust removal in the electrostatic dust collector (6) enters the flue before the bag dust collector (7), and activated carbon is sprayed into the flue, the activated carbon enters the bag dust collector (5) with the wet flue gas for dust removal treatment, in which process the activated carbon absorbs heavy metals and dioxins, and the dust collected by the bag dust collector (7) and the used activated carbon are collected into a hazardous waste bin (702); the flue gas after dust removal treatment is discharged into the flue gas temperature reducer (8); Step 4, flue gas condensation The wet flue gas after dust removal treatment in step 3 is subjected to temperature reduction to 115±5℃ in the flue gas temperature reducer (8), and then enters the flue gas condensation tower (9) for gas-liquid separation, the separated water is treated by a sewage treatment system and discharged after reaching the standard; a part of the separated flue gas is returned to the sludge dryer (3) through a flue gas return pipeline C for recycling, and the other part of the separated flue gas enters the regenerative thermal incinerator (10); the regenerative thermal incinerator (10) comprises two regenerative chambers and a combustion chamber; Step 5: removal of VOCs and CO in flue gas The flue gas entering the regenerative thermal incinerator (10) is preheated in one of the regenerative chambers and then enters the combustion chamber, heated and raised to 760-800℃, so that the VOCs and CO therein are oxidized into CO2 and H2O; the high-temperature flue gas generated in the oxidation process releases heat through the other regenerative chamber until the temperature is 115±5℃, and then is discharged from the regenerative thermal incinerator (10) to the wet flue gas deacidification tower (11); Step 6, wet flue gas deacidification The wet flue gas deacidification tower (11) adopts a solution circulation mode outside the tower, and the solution is flaked alkali or lye; the flue gas discharged from the regenerative thermal incinerator (10) enters the wet flue gas deacidification tower (11) to contact with the sprayed solution, so as to remove the acidic substances in the flue gas, and at this time the flue gas temperature is reduced to 50℃±5℃; Step 7, flue gas discharge The flue gas treated by the wet flue gas deacidification tower (11) is heated to 98℃±5℃ by the cold flue reheater (12), and then is discharged into the atmosphere through the chimney (13) at a high altitude.

6. The process of claim 5, wherein: A flow valve is arranged at the pipe joint of the outlet pipeline of the flue gas condenser (9) for controlling the flue gas return amount, and the flue gas return amount accounts for 20% of the total air volume.

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