Urea gas flow dynamic fluidized bed heat accumulation pyrolysis device and pyrolysis system

Abstract

The application discloses a urea gas flow power fluidized bed heat accumulation pyrolysis device and pyrolysis system, which comprises a fluidized tank, a gas distribution plate is installed at the hot air inlet at the bottom end of the fluidized tank, and a fluidized flow guide cylinder is installed in the fluidized tank; a urea particle conveying pipe is installed on the fluidized flow guide cylinder, a plurality of heat accumulation particles are filled in the fluidized tank, and an electric heating device is installed on the outer wall of the fluidized tank; a discharge port is arranged at the bottom of the fluidized tank; a gas ammonia port is arranged at the top end of the fluidized tank; the urea particles enter into the fluidized flow guide cylinder through the conveying pipe, the gas entering from the bottom fluidizes the heat accumulation particles, the heat accumulation particles flow upwards in the fluidized flow guide cylinder and flow into the bottom of the fluidized tank from both sides, the urea particles are heated, and ammonia gas and carbon dioxide are continuously generated in the process of continuous fluidization and movement, compared with a traditional urea solution pyrolysis method, the urea dissolution step and the corresponding device are omitted, the equipment is simplified, the land is reduced, and the energy is saved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ammonia preparation equipment, and particularly relates to a heat accumulation pyrolysis device for preparing ammonia by directly pyrolyzing urea particles and a pyrolysis system using the heat accumulation pyrolysis device. BACKGROUND

[0002] In the flue gas denitration emission treatment of coal-fired boilers, the SCR system becomes an indispensable technology. The wide application of this technology greatly reduces the emission of nitrogen oxides in flue gas, improves the surrounding atmospheric environment, and makes great contributions to environmental protection.

[0003] In the SCR system, the reducing agent is usually liquid ammonia, ammonia water and urea. Liquid ammonia is flammable and explosive, and the safety application conditions are harsh, which limits its large-scale application in industry; 10% ammonia water also enters the list of dangerous chemicals, and the safety application conditions are increasingly strict; On April 2, 2019, the General Office of the National Energy Administration issued the “Emergency Notice of the General Office of the National Energy Administration on Strengthening the Comprehensive Management of Dangerous Chemicals in the Electric Power Industry” (No. 132 of the General Office of the National Energy Administration) The text requires “actively carry out liquid ammonia tank area major hazard source management, and accelerate the urea substitution upgrading and reconstruction progress”; in this way, when the SCR system selects a reducing agent, urea will inevitably become the first choice of manufacturers. Whether it is liquid ammonia, ammonia water or urea, it must be converted into ammonia gas to be used by the SCR system.

[0004] In the current SCR system, urea is generally prepared by hydrolysis or pyrolysis. The hydrolysis method is to decompose urea in the form of aqueous solution. The pyrolysis method is to directly and quickly heat the atomized urea solution to obtain solid or molten urea. Pure urea is decomposed under heating conditions to provide reducing agent-ammonia for SCR. The hydrolysis process requires high operating pressure and temperature, and the system is complex and cumbersome, so it is rarely used. Currently, the commonly used method for preparing ammonia gas from urea is the urea solution spray pyrolysis process.

[0005] Urea solution spray pyrolysis mainly involves the preparation of urea solution, the preparation of high-temperature air in the pyrolysis chamber, the spray pyrolysis of urea solution in the pyrolysis chamber, and the urea solution preparation system, urea solution conveying system, spray system, hot air heating system, and pyrolysis system. The pyrolysis chamber requires high temperature (hot air requires more than 600 DEG C), and the process conditions are relatively harsh. If the design or operation is not proper, the system is easy to be blocked by crystallization. SUMMARY

[0006] One of the technical problems solved by the present application is to provide a urea gas flow dynamic fluidized bed heat accumulation pyrolysis device with simple structure, energy saving and good pyrolysis effect.

[0007] In order to solve the above technical problems, the technical scheme of the present application is: the urea gas flow power fluidized bed heat accumulation pyrolysis device, comprising a fluidized tank, the bottom end of the fluidized tank is provided with a hot air inlet, the hot air inlet is installed with a gas distribution plate, the bottom end of the fluidized tank is installed with a gas inlet connector which is in communication with the hot air inlet, the fluidized tank is installed with a fluidized flow guide cylinder which is open at the bottom end and the top end, and the bottom end of the fluidized flow guide cylinder and the inner wall of the fluidized tank leave a fluidized flow guide gap;

[0008] The fluidized flow guide cylinder is installed with a urea particle conveying pipe which is in communication with the inside of the fluidized flow guide cylinder at one end and extends out of the fluidized tank at the other end, the fluidized tank is filled with a plurality of heat accumulation particles which are located at the bottom of the fluidized tank and bury the fluidized flow guide cylinder, and the outer wall of the fluidized tank is installed with an electric heating device which heats the heat accumulation particles; the bottom of the fluidized tank is provided with a discharge port; and the top end of the fluidized tank is provided with a gaseous ammonia port.

[0009] As a preferred technical scheme, the gas distribution plate is a corundum gas distribution plate.

[0010] As a preferred technical scheme, the bottom of the fluidized tank is a conical structure, and the outlet end of the fluidized flow guide cylinder extends into the conical structure of the bottom end of the fluidized tank.

[0011] As a preferred technical scheme, the bottom of the fluidized flow guide cylinder is a flared horn structure.

[0012] As a preferred technical scheme, the central axis of the fluidized flow guide cylinder coincides with the central axis of the fluidized tank.

[0013] As a preferred technical scheme, the top side wall of the fluidized tank is provided with a transparent sight glass.

[0014] As a preferred technical scheme, the heat accumulation particles are ceramic particles, and the fluidized tank is installed with an anatase TiO2 doped in the heat accumulation particles.

[0015] According to the technical scheme, the urea gas dynamic fluidized bed heat storage pyrolysis device comprises a fluidized tank, a hot air inlet is arranged at the bottom end of the fluidized tank, a gas distribution plate is installed at the hot air inlet, an air inlet joint in communication with the hot air inlet is installed at the bottom end of the fluidized tank, a fluidized flow guide cylinder with openings at the bottom end and the top end is installed in the fluidized tank, and a fluidized flow guide gap is left between the bottom end of the fluidized flow guide cylinder and the inner wall of the fluidized tank; a urea particle conveying pipe with one end in communication with the inside of the fluidized flow guide cylinder and the other end extending out of the fluidized tank is installed on the fluidized flow guide cylinder, a plurality of heat storage particles located at the bottom of the fluidized tank and burying the fluidized flow guide cylinder are filled in the fluidized tank, an electric heating device for heating the heat storage particles is installed on the outer wall of the fluidized tank, a discharge port is arranged at the bottom of the fluidized tank, and an ammonia gas port is arranged at the top end of the fluidized tank; the urea particles enter the fluidized flow guide cylinder through the conveying pipe, the heat storage particles are fluidized by the gas entering from the bottom hot air inlet, the heat storage particles flow upwards in the fluidized flow guide cylinder and flow into the bottom of the fluidized tank from the two sides while wrapping the urea particles, the urea particles are heated, and ammonia gas and carbon dioxide are continuously generated in the process of continuous fluidization and movement, compared with the traditional urea solution pyrolysis method, the urea dissolution step and the corresponding device are omitted, the equipment is simplified, and energy is saved.

[0016] Another technical problem to be solved by the present application is a urea gas dynamic fluidized bed heat storage pyrolysis system based on the urea gas dynamic fluidized bed heat storage pyrolysis device.

[0017] To solve the above technical problems, the technical scheme of the present application is: a urea gas dynamic fluidized bed heat storage pyrolysis system, comprising the urea gas dynamic fluidized bed heat storage pyrolysis device described above, an air preheater and an air heater are sequentially installed between the outlet end of the flue gas discharge device of the SCR system and the air inlet joint, the urea particle conveying pipe is connected with a jet feeder, the air inlet port of the jet feeder is connected with a compressed air public system, the feed port of the jet feeder is connected with a urea particle supply device, and the ammonia gas port is connected to the ammonia injection grid of the SCR system through a pipeline.

[0018] As a preferred technical scheme, the urea particle supply device comprises a urea particle self-scoop elevator, the discharge end of the urea particle self-scoop elevator is connected with a urea addition bin, the bottom end of the urea addition bin is connected with a metering screw conveyor through a star-shaped discharger, and the discharge end of the metering screw conveyor is connected with the feed port of the jet feeder.

[0019] As a preferred technical scheme, a stirrer is installed in the urea addition bin.

[0020] The urea gas flow power fluidized bed heat accumulating pyrolysis system adopts a gas flow power fluidized bed heat accumulating urea particle direct pyrolysis process, abandons the traditional process route of preparing into a solution first and then pyrolyzing, adopts gas flow as power, and has no rotating and easy-to-damage components, so that the system is simple in structure, reduces land use, saves energy, is convenient to operate, and will not be blocked. BRIEF DESCRIPTION OF DRAWINGS

[0021] The following drawings are merely intended to schematically illustrate and explain the present application and do not limit the scope of the present application. Among them:

[0022] Figure 1 is a structural schematic view of the urea gas flow power fluidized bed heat accumulating pyrolysis device of the embodiment of the present application;

[0023] Figure 2 is a structural principle view of the urea gas flow power fluidized bed heat accumulating pyrolysis system of the embodiment of the present application;

[0024] In the drawing: 11 - fluidized tank; 12 - transparent sight glass; 21 - air distribution plate; 22 - air inlet joint; 3 - fluidized flow guide cylinder; 41 - urea particle conveying pipe; 42 - heat accumulating particle; 43 - electric heating device; 51 - discharge port; 52 - gaseous ammonia port; 61 - air preheater; 62 - air heater; 71 - jet feeder; 72 - urea feeding bin; 73 - star-shaped discharger; 74 - metering screw conveyor; 75 - stirrer. DETAILED DESCRIPTION

[0025] The present application will be further described below in combination with the drawings and embodiments. In the following detailed description, certain exemplary embodiments of the present application are described by way of illustration only. It is obvious for those skilled in the art that the described embodiments can be modified in various ways without departing from the spirit and scope of the present application. Therefore, the drawings and description are illustrative in nature and are not used to limit the protection scope of the claims.

[0026] As shown in Figure 1 The urea gas flow power fluidized bed heat accumulating pyrolysis device includes a fluidized tank 11, the bottom end of the fluidized tank 11 is provided with a hot air inlet, the hot air inlet is installed with an air distribution plate 21, the air distribution plate 21 adopts corundum air distribution plate 21; the bottom end of the fluidized tank 11 is installed with an air inlet joint 22 in communication with the hot air inlet, the fluidized tank 11 is installed with a fluidized flow guide cylinder 3 with openings at the bottom end and the top end, and a fluidized flow guide gap is left between the bottom end of the fluidized flow guide cylinder 3 and the inner wall of the fluidized tank 11; a heat shield (not shown in the drawing) is arranged outside the fluidized tank 11, which can prevent heat loss in the fluidized tank 11 and save energy.

[0027] The fluidizing draft tube 3 is provided with a urea particle conveying pipe 41, one end of which is in communication with the interior of the fluidizing tank 11 and the other end of which extends out of the fluidizing tank 11. The fluidizing tank 11 is filled with a plurality of heat storage particles 42 which are located at the bottom of the fluidizing tank 11 and which bury the fluidizing draft tube 3. The outer wall of the fluidizing tank 11 is provided with an electric heating device 43 for heating the heat storage particles 42. The electric heating device 43 is a commonly used electric heater in the prior art, and thus the structure and working principle of the electric heating device 43 are both in the prior art and will not be described here in detail. The bottom of the fluidizing tank 11 is provided with a discharge port 51. The top end of the fluidizing tank 11 is provided with a gaseous ammonia port 52.

[0028] The bottom of the fluidizing tank 11 is in a conical structure, and the outlet end of the fluidizing draft tube 3 extends into the conical structure at the bottom end of the fluidizing tank 11. The bottom of the fluidizing draft tube 3 is in a flared horn structure. The central axis of the fluidizing draft tube 3 coincides with the central axis of the fluidizing tank 11. The top portion of the sidewall of the fluidizing tank 11 is provided with a transparent sight glass 12. The heat storage particles 42 are ceramic particles, and the fluidizing tank 11 is filled with anatase TiO2 which is doped in the heat storage particles 42.

[0029] As shown in Figure 2 The urea gas flow dynamic fluidized bed heat storage pyrolysis system includes the urea gas flow dynamic fluidized bed heat storage pyrolysis device described above. An air preheater 61 and an air heater 62 are sequentially installed between the outlet end of the flue gas discharge device of the SCR system and the gas inlet joint 22. The urea particle conveying pipe 41 is connected with a jet feeder 71. The gas inlet port of the jet feeder 71 is connected with a compressed air public system. The material inlet port of the jet feeder 71 is connected with a urea particle supply device. The gaseous ammonia port 52 is connected to the ammonia injection grid of the SCR system through a pipeline.

[0030] The urea particle supply device includes a urea particle self-scoop elevator. The discharge end of the urea particle self-scoop elevator is connected with a urea dosing bin 72. The bottom end of the urea dosing bin 72 is connected with a metering screw conveyor 74 through a star-shaped discharger 73. The discharge end of the metering screw conveyor 74 is connected with the material inlet port of the jet feeder 71. The urea dosing bin 72 is provided with a stirrer 75.

[0031] In operation, the hot air after humidification at 320-350℃ enters the fluid tank 11, first passes through the corundum high-temperature cloth air distribution plate 21 for air distribution, and then rises into the fluid guide cylinder 3 to fluidize the ceramic particles mixed with anatase TiO2 in the cylinder. The fluidized ceramic particles first rise out of the fluid guide cylinder 3, then fall on the periphery outside the fluid guide cylinder 3, and then fall back to the fluid guide cylinder 3 under the action of gravity and air flow to form a cycle. The ceramic particles mixed with anatase TiO2 are heated by the electric heater outside the fluid tank 11 during the downward movement from the periphery of the fluid guide cylinder 3, and become heat storage carriers. The heat storage carriers with pyrolysis catalysis contact with the sprayed urea particles in the fluidized state in the fluid guide cylinder 3, and the urea particles are catalytically pyrolyzed by using the accumulated heat. The ammonia and carbon dioxide gases after pyrolysis are uniformly distributed in the hot air and flow out of the system with the hot air to the ammonia injection grid of the SCR system.

[0032] The fluidized hot air of the present application utilizes the flue gas of the boiler tail dust collector of the SCR system, does not introduce external air, and does not change the oxygen content and the nitrogen oxide conversion coefficient. Moreover, the normal pressure system is adopted, and there is no leakage and safe operation. The present application directly uses electric heating, and the structure is simple and not prone to failure. In the present application, the airflow is used as the power to fluidize the materials, and there is no mechanical rotating part, which is not prone to damage and has a very low maintenance amount. The heat storage filler containing the anatase TiO2 catalyst adopted in the present application has a low pyrolysis temperature and a high ammonia generation efficiency.

[0033] The present application has the following advantages: 1. The system configuration is simple, land saving, easy to manage and operate; 2. Energy saving. Compared with the urea solution spray pyrolysis, a large amount of water is not needed to be vaporized at the same time, so the energy consumption can be greatly reduced; 3. No rotating parts, low maintenance failure rate; 4. No system blockage. The solids in the system are all in flow, so there is no blockage; 5. Compared with the urea solution spray pyrolysis, the operating temperature is low, and the system is safe and reliable. The operating temperature of the pyrolysis chamber of the present system is 350℃, which is much lower than the operating temperature of the urea solution spray pyrolysis (more than 600℃).

[0034] The present application adopts the airflow power fluidized bed heat storage urea particle direct pyrolysis process, abandons the traditional process route of preparing into a solution first and then pyrolyzing, uses airflow as the power, and has no rotating and easy-to-damage parts, so that the system is simple in structure, land saving, energy saving, easy to operate, and will not be blocked.

[0035] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A urea gas stream dynamic fluidized bed regenerative pyrolysis system characterized by: The fluidized tank is provided with a hot air inlet at the bottom end, a gas distribution plate is installed at the hot air inlet, a gas fluidization guide cylinder with open top and bottom is installed in the fluidized tank, and a fluidization guide gap is left between the bottom end of the gas fluidization guide cylinder and the inner wall of the fluidized tank; A urea particle conveying pipe is installed on the gas fluidization guide cylinder, one end of which is communicated with the inside of the gas fluidization guide cylinder and the other end of which extends out of the fluidized tank, a plurality of heat storage particles are filled in the fluidized tank and buried in the gas fluidization guide cylinder at the bottom of the fluidized tank, an electric heating device for heating the heat storage particles is installed on the outer wall of the fluidized tank, a discharge port is arranged at the bottom of the fluidized tank, and an ammonia gas port is arranged at the top end of the fluidized tank; The heat storage particles are ceramic particles, and an anatase TiO2 doped in the heat storage particles is installed in the fluidized tank. An air preheater and an air heater are installed between the outlet end of the flue gas discharge device of the SCR system and the gas inlet joint in sequence, the urea particle conveying pipe is connected with a jet feeder, the gas inlet port of the jet feeder is connected with a compressed air public system, the feed port of the jet feeder is connected with a urea particle supply device, and the ammonia gas port is communicated to the ammonia injection grid of the SCR system through a pipeline.

2. The urea gas stream dynamic fluidized bed regenerative pyrolysis system of claim 1, wherein: The gas distribution plate is a corundum gas distribution plate.

3. The urea gas stream dynamic fluidized bed regenerative pyrolysis system of claim 1, wherein: The bottom of the fluidized tank is a conical structure, and the outlet end of the gas fluidization guide cylinder extends into the conical structure at the bottom end of the fluidized tank.

4. The urea gas stream dynamic fluidized bed regenerative pyrolysis system of claim 1, wherein: The bottom of the gas fluidization guide cylinder is a flared horn structure.

5. The urea gas stream dynamic fluidized bed regenerative pyrolysis system of claim 1, wherein: The central axis of the gas fluidization guide cylinder coincides with the central axis of the fluidized tank.

6. The urea gas stream dynamic fluidized bed regenerative pyrolysis system of claim 1, wherein: A transparent sight glass is arranged on the top side wall of the fluidized tank.

7. The urea gas stream dynamic fluidized bed regenerative pyrolysis system of claim 1, wherein: The urea particle supply device comprises a urea particle self-scoop elevator, a urea dosing bin is connected to the discharge end of the urea particle self-scoop elevator, a metering screw conveyor is connected to the bottom end of the urea dosing bin through a star-shaped discharger, and the discharge end of the metering screw conveyor is connected with the feed port of the jet feeder.

8. The urea gas stream dynamic fluidized bed regenerative pyrolysis system of claim 7, wherein: A stirrer is installed in the urea dosing bin.

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