An integrated device for fluidizing, drying and incineration of high-ash sludge

Abstract

The present invention discloses an integrated device for fluidized drying and incineration of high-ash sludge, which is composed of a spiral feeder, a fluidized bed incinerator, a cyclone separator, and a fluidized drying bed connected in sequence. The fluidized drying bed is connected to the ash return pipe of the cyclone separator with a three-way valve control to receive high-temperature return ash; the fluidized drying bed is equipped with a wet sludge granulator, an exhaust port connected to the incinerator, a double-layer air distribution plate with different apertures, a sludge discharge port and a nitrogen protection device. The integrated device utilizes the waste heat of the high-temperature return ash to directly contact the wet sludge after granulation for heat exchange, thereby realizing rapid drying of the sludge. The arrangement of the double-layer air distribution plate and the return of the drying tail gas to the furnace can avoid the thermal impact caused by instantaneous high temperature, and treat polluted gases and fine particles. It has the advantages of efficient utilization of waste heat, economic safety, environmental protection and energy saving, and is suitable for the incineration application of high-ash sludge.

Description

Technical Field

[0001] The invention relates to the field of sludge resource processing, and in particular to an integrated device for fluidizing, drying and incinerating high-ash sludge. Background Art

[0002] Incineration is a common treatment and disposal technology for sludge resource utilization. It has the advantages of high efficiency, large reduction, strong harmlessness, and thermal energy reuse. Its market share has gradually increased in recent years. However, in actual applications, due to the high moisture content of sludge, the moisture content is still 40-80% after belt or plate and frame filter press dehydration treatment in the sewage plant. It cannot be directly fed into the incineration furnace and often requires drying pretreatment. Sludge drying pretreatment accounts for 40% of the total incineration cost. At present, low-temperature electric auxiliary heating or low-temperature flue gas circulation is generally used as a heat source, which has problems such as high energy consumption, long time consumption, and large land area. At the same time, the complex components in a large amount of flue gas will also increase the difficulty of treating drying odor. Therefore, it is necessary to further develop new technologies or equipment for sludge drying that are energy-saving, efficient, and environmentally friendly.

[0003] Chinese patent CN207486791U designs a circulating fluidized bed boiler that burns low calorific value and high ash fuel. Part of the high-temperature return ash is placed in the gas-solid heat exchange chamber through the ash discharge pipe, and primary air is introduced through the air distribution plate to perform fluidized heat exchange with the return ash. After the heat exchange, the high-temperature gas is supplied to the furnace for combustion, which is beneficial to improve the heat exchange efficiency and realize the waste heat utilization of the high-temperature ash.

[0004] Chinese patent CN107311424A discloses a wet sludge drying method and a fluidized bed dryer. Using solid particles at 200-500°C as heat carriers to fluidize and heat the wet sludge can reduce the risk of spontaneous combustion of the sludge during high-temperature drying.

[0005] Chinese patent CN101708940A proposes a sludge drying and incineration treatment system that utilizes gas-solid waste heat. The high-temperature sludge return ash at 800-900°C after incineration is mixed with the dehydrated sludge, and then the mixture is semi-dried with 100-200°C flue gas before entering the dust collector, which captures dust in the flue gas while utilizing the return ash and flue gas waste heat.

[0006] The above methods all adopt the idea of ​​high-temperature sludge drying. Compared with traditional drying, it is conducive to improving drying efficiency and saving drying time. However, there are still some shortcomings: 1) The high-temperature solid heat source used for sludge drying should be actually existing and easily available in the industrial chain. The subsequent disposal of sludge drying is often incineration. Due to the limitation of incineration temperature (greater than 850°C), the temperature of return ash is generally limited to about 800°C. When it is directly mixed with wet sludge, there is a risk of spontaneous combustion when the wet sludge has a low moisture content and sufficient oxygen. In addition, local high temperature is easy to cause pollution. The sludge undergoes devolatilization reaction and loses calorific value; 2) Gas-solid heat exchange is mostly adopted, and the high-temperature ash transfers heat to the gas, and then the gas transfers heat to the wet sludge for drying. The heat transfer efficiency is low and the waste heat loss is high; 3) The amount of dust generated in the low-temperature flue gas is large, but the waste heat is small and has been burned. After being captured by the wet sludge and then entering the furnace, it increases the burden on the furnace. What is important is that the odor and fine particulate matter (including sludge particles and return ash) generated during the drying process are not effectively treated; 4) The wet sludge is not pretreated, fluidization is difficult, and the heat exchange efficiency is low. Summary of the invention

[0007] In order to improve the drying efficiency of sludge, safely realize the efficient thermal utilization of high-temperature fly ash, and treat the polluted gas released by drying, the present invention proposes an integrated device for fluidizing, drying and incinerating high-ash sludge.

[0008] An integrated device for fluidizing, drying and incineration of high-ash sludge, comprising:

[0009] A screw feeder, a fluidized bed incinerator, a cyclone separator and a fluidized drying bed connected in sequence;

[0010] The fluidized bed incinerator is provided with a primary air inlet, an air distribution plate and a secondary air inlet; the fluidized drying bed is provided with a wet sludge granulator, a double-layer air distribution plate, an exhaust port, an air blower and a sludge discharge port.

[0011] Furthermore, the ash return pipe at the bottom of the cyclone separator is provided with a three-way regulating valve, and the ash return pipe is connected to the double-layer air distribution plates of the fluidized drying bed, and the high-temperature ash return rate is controlled according to the wet sludge flow and the temperature in the fluidized drying bed.

[0012] Furthermore, the wet sludge granulator is located on the top of the fluidized drying bed to granulate the sludge with a moisture content of 40 to 80%.

[0013] Furthermore, the double-layer air distribution plates in the fluidized drying bed are spaced 0.5 to 1 m apart, wherein the aperture of the upper air distribution plate (7) is 1 to 2 cm, and the aperture of the lower air distribution plate (11) is 0.3 to 0.5 cm, providing a gas-solid heat exchange buffer space to avoid adverse effects caused by instantaneous high-temperature thermal reactions.

[0014] Furthermore, the exhaust port at the upper end of the fluidized drying bed is connected to the incinerator, wherein the connection point of the incinerator is located 0.5 to 1 m above the upper end of its secondary air port, which is used to treat gaseous pollutants and fine particulate solids (sludge and return ash) in the drying exhaust gas and supplement the secondary air volume.

[0015] Furthermore, the fluidized drying bed is provided with a temperature sensor, and a nitrogen protection device is connected to the bottom wind chamber. The protection device is in a closed state during normal drying. When local combustion occurs during drying, i.e., the temperature rises abnormally, the protection device is activated to blow in nitrogen.

[0016] The technical effects of the present invention are embodied in:

[0017] The present invention uses the residual heat of the sludge to dry the sludge in a fluidized manner on the basis of the need for secondary incineration of the sludge return ash. The device embodies the following advantages: 1) The wet sludge is pre-treated by granulation before drying, which can enhance the fluidity and heat exchange surface area of ​​the sludge and greatly improve the drying efficiency; 2) There are both gas-solid heat exchange and solid-solid heat exchange modes, and a certain buffer zone is provided for gas-solid heat exchange before the high-temperature return ash contacts the sludge for heat exchange, so as to avoid the sludge and return ash contacting under high temperature to cause devolatilization and combustion reaction, reduce the heat loss of the sludge, and at the same time, with the assistance of a nitrogen protection device, the safety of the high-temperature drying system is improved; 3) The drying tail gas directly enters the furnace for combustion, and while treating the polluted gas and fine solid particles (including sludge and return ash) in the drying tail gas, the secondary air volume and heat are supplemented. Therefore, the device has the advantages of high waste heat utilization, economic safety, environmental protection and energy saving, and is suitable for the incineration application of high-ash sludge. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of an integrated device for fluidizing, drying and incineration of high-ash sludge according to the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0020] like Figure 1 As shown, the present invention comprises a screw feeder (1), a fluidized bed incinerator (3), a cyclone separator (4) and a fluidized drying bed (6) which are connected in sequence;

[0021] The fluidized bed incinerator is provided with a primary air inlet (10), an air distribution plate (2) and a secondary air inlet (9);

[0022] The top of the fluidized drying bed is connected to a wet sludge granulator (5); an exhaust port (14) is arranged at the top, the exhaust port is connected to an incinerator, and the incinerator connection point is located 0.5 to 1 m above the secondary air port of the incinerator; a double-layer air distribution plate (7, 11) is arranged at the bottom, the air distribution plate is spaced 0.5 to 1 m apart, and the middle of the double-layer air distribution plate is connected to an ash return pipe with a three-way regulating valve (13) at the bottom of the cyclone separator; a sludge discharge port (8) is arranged on the side; and an air blast port (12) and a nitrogen protection device (15) are arranged at the bottom.

[0023] The working process of the present invention is as follows:

[0024] The dried sludge enters the fluidized bed incinerator (3) through a screw feeder (1) for combustion, and the combustion temperature is 850-950°C, wherein the primary air (10) is blown in from the bottom, passes through the air distribution plate (2) to fluidize and burn the sludge particles, and the secondary air (9) is blown in from the side of the incinerator to supplement the oxygen required for combustion; after combustion, the flue gas and fly ash immediately enter the connected cyclone separator (4) for gas-solid separation, and the flue gas enters the subsequent waste heat utilization and flue gas purification system from the top of the cyclone separator, and the fly ash at 600-800°C enters the fluidized drying bed (6) from the bottom through the return pipe as a sludge drying heat source, wherein the return pipe is equipped with a three-way control valve (13) to control the rate of the return ash according to the flow rate and drying temperature of the wet sludge in the fluidized drying bed;

[0025] During the sludge drying process, wet sludge with a moisture content of 40-80% is pre-treated in a granulator (5) and then enters a fluidized drying bed (6). A certain amount of air is blown in through the bottom blast port (12) to maintain a fluidized state. Granulation pre-treatment can enhance the fluidizability and specific surface area of ​​the sludge and improve the sludge drying efficiency. High-temperature return ash enters the fluidized drying bed from between the double-layer air distribution plates (7, 11), and performs preliminary heat exchange with the air in this interval to reduce the high temperature of the return ash surface. Then, it passes through the upper air distribution plate with the air flow to contact the fluidized sludge for another heat exchange, thereby achieving sludge drying. In this process, the air that has reached a certain temperature can also provide heat for sludge drying through gas-solid heat exchange. The double-layer air distribution plate can reduce the risk of spontaneous combustion caused by direct contact between high-temperature return ash and sludge after entering the drying bed, or avoid the reduction of calorific value of mud due to high-temperature thermal decomposition of sludge during the drying process; on the other hand, it can separate the fluidization zones of sludge and return ash, so as to avoid the impact of unsatisfactory sludge fluidization in the initial stage of drying on the fluidization and heat exchange of return ash, causing sludge and ash to agglomerate and block the air distribution plate, thereby reducing the drying efficiency. After drying, the sludge is discharged through the discharge port (8) and stored for sludge incineration; the tail gas enters the furnace through the exhaust port (14) for incineration, and while replenishing the secondary air volume, the dried polluted gas and fine particles therein are incinerated to achieve low-pollution drying of the sludge. When the drying system is operating normally, the nitrogen protection device connected to the wind chamber at the bottom of the fluidized drying bed is in a closed state. When local combustion of sludge may occur due to excessively high temperature of the return ash, the temperature sensor will display abnormal high temperature, and the nitrogen protection device will be immediately started to blow in nitrogen, which will reduce the temperature and oxygen content at the same time, thereby enhancing the safety performance of the system.

[0026] Compared with the traditional drying device that uses flue gas waste heat as a heat source and a chain-type moving fixed bed as a drying device, the above-mentioned embodiment of a high-ash sludge fluidized drying and incineration integrated device occupies less space and has a lower investment cost. High-temperature and fluidized drying can greatly improve the drying efficiency and reduce the drying time. The setting of double-layer air distribution plates and nitrogen protection devices reduces the risk of high-temperature drying of sludge. At the same time, the incineration treatment of tail gas reduces the pollution risk of drying. The device has huge market application potential for the incineration of high-ash sludge.

Claims

1. An integrated device for fluidizing, drying and incineration of high-ash sludge, characterized in that: The invention comprises a screw feeder (1), a fluidized bed incinerator (3), a cyclone separator (4) and a fluidized drying bed (6) which are connected in sequence; wherein the fluidized bed incinerator is provided with a primary air inlet (10), an air distribution plate (2) and a secondary air inlet (9); wherein the fluidized drying bed is provided with a wet sludge granulator (5), a double-layer air distribution plate, an exhaust port (14), an air blast port (12), a sludge discharge port (8) and a nitrogen protection device (15); The ash return pipe at the bottom of the cyclone separator (4) is provided with a three-way regulating valve (13), and the connection point between the ash return pipe and the fluidized drying bed (6) is located between the double-layer air distribution plates; The wet sludge granulator (5) is located on the top of the fluidized drying bed (6) and processes wet sludge with a moisture content ranging from 40 to 80%; The exhaust port (14) at the upper end of the fluidized drying bed (6) is connected to the incinerator, wherein the connection point of the incinerator is located 0.5 to 1 m above the upper end of the secondary air port (9).

2. The high-ash sludge fluidization, drying and incineration integrated device according to claim 1 is characterized in that: The double-layer air distribution plates in the fluidized drying bed (6) are spaced 0.5 to 1 m apart; the aperture of the upper air distribution plate (7) is 1 to 2 cm, and the aperture of the lower air distribution plate (11) is 0.3 to 0.5 cm.

3. The high-ash sludge fluidization, drying and incineration integrated device according to claim 1 is characterized in that: The fluidized drying bed (6) is provided with a temperature sensor, and the bottom wind chamber is connected to a nitrogen protection device (15); during normal drying, the protection device is in a closed state, and when local combustion occurs during drying, i.e., the temperature rises abnormally, the protection device is activated to blow in nitrogen.

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