A method and apparatus for conveying high-temperature pulverized coke for boiler power generation.

Abstract

This invention provides a method and apparatus for conveying high-temperature pulverized coke for boiler power generation. The method includes: determining a safety boundary for hot pulverized coke conveying; using a conveying medium formed by mixing hot and cold primary air from the air preheater outlet to achieve a first temperature; pyrolyzing pulverized coal in a pyrolysis unit and then separating it in a separation unit to obtain pulverized coke at a second temperature; cooling the pulverized coke in a pulverized coke bin, reducing it from the second temperature to a third temperature; wherein the third temperature is higher than the first temperature; and, within the safety boundary, conveying the pulverized coke at the third temperature to the boiler using the conveying medium at the first temperature for power generation. One technical advantage of this invention is that it not only achieves the safe conveying of hot pulverized coke but also enables the clean combustion of high-temperature pulverized coke in large pulverized coal boilers.

Description

Technical Field

[0001] This invention belongs to the field of boiler power generation technology, specifically relating to a method and apparatus for conveying high-temperature pulverized coke for boiler power generation. Background Technology

[0002] The clean combustion of high-temperature pulverized coke in pulverized coal boilers in power plants is expected to be a feasible way to solve the overcapacity of pulverized coke, which is of great significance to the sustainable development of energy. Due to the advantages of high calorific value, low ash and sulfur content, pulverized coke has good environmental performance when used in power plant boilers. At the same time, the utilization of high-quality pulverized coke and the sensible heat it carries can effectively reduce coal consumption in thermal power plants.

[0003] Because the erosion and abrasion index of pulverized coke is significantly higher than that of ordinary coal, it has a considerable impact on the grinding components of the pulverizing system and the pulverized coal conveying system, posing a challenge to the application of pulverized coke in existing units. However, directly feeding high-temperature pulverized coke into the boiler for combustion without pulverization requires consideration of the safety of pulverized coke hot transportation. Furthermore, pulverized coke has a low volatile content and its combustion performance is worse than that of pulverized coal. Burning it in a boiler may lead to problems such as delayed combustion, unstable ignition at low loads, and decreased combustion efficiency. Therefore, it is necessary to consider suitable high-temperature transportation conditions and measures to enhance ignition and stabilize combustion. However, measures to enhance ignition and measures to alleviate slagging in the furnace are contradictory. Therefore, boiler design for burning high-temperature pulverized coke must coordinate the relationship between combustion stability, combustion economy, and safety.

[0004] Therefore, there is an urgent need for a method and device for conveying high-temperature pulverized coke for boiler power generation, so as to achieve the clean combustion of high-temperature pulverized coke in large pulverized coal boilers. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a new technical solution for a method and apparatus for conveying high-temperature pulverized coke for boiler power generation.

[0006] According to a first aspect of the present invention, a method for conveying high-temperature pulverized coke for boiler power generation is provided, comprising:

[0007] Determine the safety boundaries for hot coke transport;

[0008] The hot primary air and cold primary air generated at the air preheater outlet are mixed to form the conveying medium at the first temperature;

[0009] After pyrolysis in the pyrolysis unit, pulverized coal is separated in the separation unit to obtain coke at a second temperature; the coke is cooled in the coke bin and its temperature is reduced from the second temperature to a third temperature; wherein the third temperature is higher than the first temperature;

[0010] Under the aforementioned safety boundary, coke powder at a third temperature is transported to the boiler using a conveying medium at a first temperature for power generation.

[0011] Optionally, the safety boundary is to use air with a temperature not higher than 268°C to transport high-temperature coke with a temperature not higher than 325°C.

[0012] Optionally, the primary air is heated in the air preheater by the flue gas at the tail of the boiler to form hot primary air.

[0013] Optionally, the temperature of the hot primary air is 350°C to 400°C, and the first temperature is 268°C.

[0014] Optionally, the second temperature is 500℃~600℃, and the third temperature is 325℃.

[0015] Optionally, determining the safety boundaries for hot coke transport includes:

[0016] A small experimental platform was used to determine the safety boundaries of the conveying medium temperature and coke temperature under air atmosphere. Specifically, the mass of coke before and after reaction, the O2 concentration and CO concentration at the outlet were measured at different gas temperatures and coke temperatures using the small experimental platform. The coke loss growth rate and CO weight loss growth rate were calculated. The safety boundaries of hot coke conveying were determined by analyzing the coke loss growth rate and CO weight loss growth rate.

[0017] Optionally, the small experimental platform includes an air compressor, a gas distribution cabinet, a flow control system, a first tubular furnace, and a second tubular furnace. Gas is supplied to the first tubular furnace through the cooperation of the air compressor, the gas distribution cabinet, and the flow control system. The built-in coil of the first tubular furnace is used to heat the gas, and the second tubular furnace is used to heat the coke powder. The heated gas atmosphere comes into contact with the high-temperature coke powder in the second tubular furnace. Safety is determined by observing the state of the coke powder, the oxygen content at the outlet of the second tubular furnace, and the CO concentration.

[0018] Optionally, a fan can be used to output cold primary air.

[0019] According to a second aspect of the present invention, a high-temperature pulverized coke conveying device for boiler power generation is provided, which conveys pulverized coke using the conveying method described in the first aspect, comprising:

[0020] The system includes a pyrolysis unit, a separation unit, and a coke powder bin. The input end of the separation unit is connected to the pyrolysis unit, and the output end is connected to the coke powder bin.

[0021] An air preheater, a blower, a first pipeline, and a boiler are provided. The output end of the air preheater and the output end of the blower are respectively connected to the first end of the first pipeline, and the second end of the first pipeline is connected to the boiler.

[0022] The second pipe has a first end connected to the coke silo and a second end connected to the middle of the first pipe.

[0023] Optionally, the high-temperature pulverized coke conveying device for boiler power generation also includes a coal mill;

[0024] The output end of the coal mill is connected to the pyrolysis unit;

[0025] The tail end of the boiler is connected to the air preheater, and the flue gas output from the tail end of the boiler serves as the heat source for the primary air in the air preheater.

[0026] One technical advantage of this invention is that:

[0027] In this embodiment, firstly, a safety boundary for hot coke conveying is determined; secondly, hot primary air from the air preheater outlet is mixed with cold primary air to form a conveying medium at a first temperature; thirdly, pulverized coal is pyrolyzed in the pyrolysis unit and separated in the separation unit to obtain coke at a second temperature; the coke is cooled in the coke bin, decreasing from the second temperature to a third temperature; finally, within the safety boundary, the coke at the third temperature is conveyed to the boiler for power generation using the conveying medium at the first temperature. This high-temperature coke conveying method for boiler power generation not only achieves safe conveying of hot coke but also effectively ensures the relationship between the combustion stability, combustion economy, and safety of the coke, thereby realizing the clean combustion of high-temperature coke in large pulverized coal boilers. Attached Figure Description

[0028] Figure 1 This is a schematic flowchart of a high-temperature pulverized coke conveying method for boiler power generation according to an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the structure of a small experimental platform according to an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of a high-temperature pulverized coke conveying method for boiler power generation according to an embodiment of the present invention.

[0031] In the diagram: 1. Air compressor; 2. Gas distribution cabinet; 3. Flow control system; 4. First tubular furnace; 5. Second tubular furnace; 6. Gas analyzer; 7. Pyrolysis unit; 8. Separation unit; 9. Powdered coke bin; 10. Air preheater; 11. Blower; 12. First pipeline; 13. Boiler; 14. Second pipeline; 15. Coal mill. Detailed Implementation

[0032] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0033] The embodiments of this application will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0034] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0035] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0036] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0037] According to a first aspect of the invention, see Figure 1 A method for conveying high-temperature pulverized coke for boiler power generation is provided, comprising:

[0038] Step S100: Determine the safety boundary for hot coke conveying;

[0039] Step S200: The hot primary air and cold primary air generated at the air preheater outlet are mixed to form a conveying medium at the first temperature;

[0040] In step S300, after pyrolysis in the pyrolysis unit, pulverized coal is separated in the separation unit to obtain coke at a second temperature; the coke is cooled in the coke bin and its temperature is reduced from the second temperature to a third temperature; wherein the third temperature is higher than the first temperature.

[0041] In step S400, within the safety boundary, coke powder at a third temperature is transported to the boiler using a transport medium at a first temperature for power generation. The transport method is continuous transport.

[0042] In the embodiments of this application, the high-temperature pulverized coke conveying method for boiler power generation not only achieves safe conveying of hot pulverized coke, but also better ensures the relationship between the combustion stability, combustion economy and safety of pulverized coke, thereby realizing the clean combustion of high-temperature pulverized coke in large pulverized coal boilers.

[0043] Optionally, the safety boundary involves using air at a temperature not exceeding 268°C to transport high-temperature pulverized coke at a temperature not exceeding 325°C. This helps ensure the safety of hot transport of high-temperature pulverized coke, and also helps ensure the combustion stability, combustion economy, and safety of the high-temperature pulverized coke.

[0044] Optionally, the primary air is heated by the flue gas at the boiler tail end within the air preheater to form hot primary air. This fully utilizes the heat from the flue gas at the boiler tail end to heat the primary air, resulting in better energy savings.

[0045] Optionally, the temperature of the hot primary air is 350℃~400℃, and the first temperature is 268℃. The temperature design of the hot primary air is relatively reasonable. By mixing the hot and cold primary air, it helps to quickly obtain the conveying medium with a first temperature of 268℃.

[0046] Optionally, the second temperature is 500℃~600℃, and the third temperature is 325℃. The high-temperature pulverized coke at the outlet of the pyrolysis unit, which is 500℃~600℃, is initially cooled to 325℃. The hot primary air (350℃~400℃) at the outlet of the air preheater is mixed with the cold primary air and its temperature is adjusted to the safe air temperature boundary of 268℃. The primary air is used as a conveying medium and mixed with the high-temperature pulverized coke. After being sent to the furnace of the boiler for combustion through the first pipeline and the burner nozzle of the boiler.

[0047] Optionally, determining the safety boundaries for hot coke transport includes:

[0048] A small experimental platform was used to determine the safety boundaries of the conveying medium temperature and coke temperature under air atmosphere. Specifically, the mass of coke before and after reaction, the O2 concentration and CO concentration at the outlet were measured at different gas temperatures and coke temperatures using the small experimental platform. The coke loss growth rate and CO weight loss growth rate were calculated. The safety boundaries of hot coke conveying were determined by analyzing the coke loss growth rate and CO weight loss growth rate.

[0049] In the above embodiments, the method of determining the safety boundary of hot coke conveying is relatively reasonable and helps to ensure the safety of hot coke conveying at high temperature.

[0050] Optionally, see Figure 2 The small experimental platform includes an air compressor 1, a gas distribution cabinet 2, a flow control system 3, a first tubular furnace 4, and a second tubular furnace 5. The air compressor 1, the gas distribution cabinet 2, and the flow control system 3 work together to supply gas to the first tubular furnace 4. The built-in coil of the first tubular furnace 4 is used to heat the gas. The second tubular furnace 5 is used to heat the coke powder. The heated gas atmosphere comes into contact with the high-temperature coke powder in the second tubular furnace 5. The safety is determined by observing the state of the coke powder (whether there are sparks or fire), the oxygen content at the outlet of the second tubular furnace, and the CO concentration.

[0051] In the above embodiments, the small experimental platform is reasonably set up, and safety can be accurately determined by observing the state of the coke powder, the oxygen content at the outlet of the second tube furnace, and the CO concentration.

[0052] As a specific implementation method, during the experiment, CO concentration monitoring and coke weight loss rate testing were conducted by real-time monitoring of the contact between high-temperature gas and coke until the outlet oxygen content and CO concentration stabilized using a gas analyzer 6. The stabilization time of the outlet concentration was generally over 30 minutes. This small-scale test bench discussed the maximum values ​​of CO concentration and coke weight loss rate after the contact between hot air and hot coke stabilized. The safety range was mainly limited based on the maximum CO concentration after stabilization during the experiment. Combined with the analysis of coke weight loss rate, the design time for coke gas to enter the boiler was less than 30 minutes. The CO concentration and coke weight loss rate during the transportation process were less than the values ​​simulated in the small-scale test. Therefore, the safety boundaries determined by this small-scale test bench are safe and applicable for dynamic transportation of large equipment.

[0053] It should be noted that the effect of air temperature on the safe transport of high-temperature pulverized coke is shown in Table 1. The influence of heating atmosphere temperature changes on the safety of high-temperature pulverized coke was explored. Observations show that with increasing gas temperature, CO concentration and pulverized coke weight loss show an increasing trend. Thermogravimetric analysis data shows that under normal air temperature, the initial reaction temperature corresponding to the first combustion peak of pulverized coke is 337℃. Table 1 shows that when the pulverized coke temperature is around 300℃, the CO concentration ranges from 818ppm to 1590ppm during a 43℃ temperature increase, indicating that the transport air temperature has little effect on CO concentration. When the pulverized coke temperature rises to 325℃, the transport air temperature has a significant impact on CO concentration. During a 50℃ temperature increase, the CO concentration rises from 1973ppm to 6727ppm, an increase more than six times that at 300℃. Analysis shows that increasing the temperature of the transport medium lowers the ignition point of pulverized coke, especially significantly impacting the safety of high-temperature pulverized coke. Therefore, using high-temperature gases to transport high-temperature pulverized coke is not recommended.

[0054] Table 1

[0055]

[0056] Furthermore, the impact of coke temperature on the safe transport of high-temperature coke is shown in Table 2, which explores the influence of coke temperature changes on the safety of high-temperature coke. Table 2 shows that when the gas temperature is around 230℃, the CO concentration ranges from 554ppm to 3369ppm during a 27℃ temperature increase, with an average growth rate of 104.26ppm / ℃. When the gas temperature is around 250℃, the CO concentration ranges from 901ppm to 6507ppm during a 54℃ temperature increase, with an average growth rate of 103.81ppm / ℃. Combined with the above analysis of the impact of air temperature on the safe transport of high-temperature coke, it can be seen that at lower air temperatures, the air temperature has little effect on the CO concentration growth rate. Therefore, coke temperature has a significant impact on the ignition point of coke and the CO concentration; as the coke temperature increases, the CO concentration rises relatively steadily and continuously.

[0057] Table 2

[0058]

[0059] In summary, the above analysis examined the impact of air temperature and coke temperature on the safety of hot coke conveying. To further determine the appropriate safety boundary for coke conveying, multiple experiments were conducted on a small-scale test bench. The mass of coke before and after reaction, the O2 concentration at the outlet, and the CO concentration were measured at different gas temperatures and coke temperatures. The coke weight loss rate, CO growth rate, and coke weight loss growth rate were calculated. When the CO concentration increased rapidly and the coke lost weight rapidly, the system safety was poor. Therefore, the safety boundary was determined by analyzing the growth rates of CO and coke weight loss. Observations showed that when the coke temperature was below 325℃ and the gas temperature was below 268℃, the system CO concentration was below 3000ppm, and both the CO growth rate and the coke weight loss growth rate were slow, indicating a high overall system safety. As the coke and gas temperatures further increased, the CO growth rate and the coke weight loss rate increased rapidly, and the safety of the system for conveying coke with high-temperature gas significantly deteriorated. When the temperature of the conveying gas increases to 294℃, the coke at 324℃ shows significant weight loss and sparks can be observed. This is different from the initial combustion temperature of 337℃ for the first combustion peak of coke under normal air temperature, as determined by thermogravimetric analysis. Therefore, it is not recommended to use air with a temperature higher than 268℃ to convey high-temperature coke with a temperature higher than 325℃. For specific data on safe conveying of coke under air atmosphere, please refer to Table 3.

[0060] Table 3

[0061]

[0062] Optionally, a fan can be used to output cooled primary air. This helps to quickly mix cooled and heated primary air.

[0063] For example, at the outlet of the pyrolysis unit, the high-temperature pulverized coke at 500℃~600℃ is initially cooled to 325℃ through the pulverized coal bunker. The hot primary air (350℃~400℃) from the air preheater outlet is mixed with the cold primary air from the primary air fan bypass and its temperature adjusted to the safe air temperature boundary of 268℃. The primary air, as the conveying medium, is mixed with the high-temperature pulverized coke and then sent to the boiler furnace for combustion through the first pipeline and the boiler burner nozzle. To ensure the matching between the pyrolysis unit and the power generation system, and considering the contradiction between the stable operation requirements of the pyrolysis unit and the volatility of the power generation system, the load of the high-temperature pulverized coke power generation is kept constant. When the unit load fluctuates, the coal combustion system is adjusted first.

[0064] According to a second aspect of the invention, see Figure 3 A high-temperature pulverized coke conveying device for boiler power generation is provided, which conveys pulverized coke using the conveying method described in the first aspect, comprising:

[0065] The pyrolysis unit 7, the separation unit 8, and the coke powder bin 9 are provided. The input end of the separation unit 8 is connected to the pyrolysis unit 7, and the output end is connected to the coke powder bin 9.

[0066] The air preheater 10, the blower 11, the first pipeline 12 and the boiler 13 are connected to the first end of the first pipeline 12, respectively, and the second end of the first pipeline 12 is connected to the boiler 13.

[0067] The second pipe 14 has its first end connected to the coke silo 9 and its other end connected to the middle of the first pipe 12.

[0068] In the above embodiments, the high-temperature pulverized coke conveying device for boiler power generation is reasonably designed, which can not only ensure the safety of hot conveying of high-temperature pulverized coke, but also ensure the economy, stability and safety of high-temperature pulverized coke combustion.

[0069] Optionally, the high-temperature pulverized coke conveying device for boiler power generation also includes a coal mill 15;

[0070] The output end of the coal mill 15 is connected to the pyrolysis unit 7;

[0071] The tail end of the boiler 13 is connected to the air preheater 10. The flue gas output from the tail end of the boiler 13 serves as the heat source for the primary air in the air preheater 10. This fully utilizes the heat of the flue gas output from the tail end of the boiler 13 and improves energy efficiency.

[0072] In the above embodiment, the coal mill 15 is used to grind the raw coal in order to obtain pulverized coal with uniform fineness, thereby helping to achieve full pyrolysis of the pulverized coal in the pyrolysis unit 7.

[0073] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for conveying high-temperature pulverized coke for boiler power generation, characterized in that, include: Determine the safety boundary for hot coke conveying; the safety boundary is the use of air with a temperature not exceeding 268°C to convey high-temperature coke with a temperature not exceeding 325°C; The hot primary air and cold primary air generated at the air preheater outlet are mixed to form the conveying medium at the first temperature; After pyrolysis in the pyrolysis unit, pulverized coal is separated in the separation unit to obtain coke at a second temperature; the coke is cooled in the coke bin and its temperature is reduced from the second temperature to a third temperature; wherein the third temperature is higher than the first temperature; Under the aforementioned safety boundary, coke powder at a third temperature is transported to the boiler using a conveying medium at a first temperature for power generation.

2. The method for conveying high-temperature pulverized coke for boiler power generation according to claim 1, characterized in that, The primary air is heated by the flue gas at the tail of the boiler within the air preheater to form hot primary air.

3. The method for conveying high-temperature pulverized coke for boiler power generation according to claim 2, characterized in that, The temperature of the hot primary air is 350℃~400℃, and the first temperature is 268℃.

4. The method for conveying high-temperature pulverized coke for boiler power generation according to claim 3, characterized in that, The second temperature is 500℃~600℃, and the third temperature is 325℃.

5. The method for conveying high-temperature pulverized coke for boiler power generation according to claim 4, characterized in that, Determine the safety boundaries for hot coke transport, including: A small experimental platform was used to determine the safety boundaries of the conveying medium temperature and coke temperature under air atmosphere. Specifically, the mass of coke before and after reaction, the O2 concentration and CO concentration at the outlet were measured at different gas temperatures and coke temperatures using the small experimental platform. The coke loss growth rate and CO weight loss growth rate were calculated. The safety boundaries of hot coke conveying were determined by analyzing the coke loss growth rate and CO weight loss growth rate.

6. The method for conveying high-temperature pulverized coke for boiler power generation according to claim 5, characterized in that, The small experimental platform includes an air compressor, a gas distribution cabinet, a flow control system, a first tubular furnace, and a second tubular furnace. Gas is supplied to the first tubular furnace through the cooperation of the air compressor, gas distribution cabinet, and flow control system. The built-in coil of the first tubular furnace is used to heat the gas. The second tubular furnace is used to heat the coke powder. The heated gas atmosphere comes into contact with the high-temperature coke powder in the second tubular furnace. Safety is determined by observing the state of the coke powder, the oxygen content at the outlet of the second tubular furnace, and the CO concentration.

7. The method for conveying high-temperature pulverized coke for boiler power generation according to claim 6, characterized in that, A fan is used to output cold primary air.

8. A high-temperature pulverized coke conveying device for boiler power generation, characterized in that, The method for conveying coke powder as described in claim 7 includes: The system includes a pyrolysis unit, a separation unit, and a coke powder bin. The input end of the separation unit is connected to the pyrolysis unit, and the output end is connected to the coke powder bin. An air preheater, a blower, a first pipeline, and a boiler are provided. The output end of the air preheater and the output end of the blower are respectively connected to the first end of the first pipeline, and the second end of the first pipeline is connected to the boiler. The second pipe has a first end connected to the coke silo and a second end connected to the middle of the first pipe.

9. The high-temperature pulverized coke conveying device for boiler power generation according to claim 8, characterized in that, This also includes coal mills; The output end of the coal mill is connected to the pyrolysis unit; The tail end of the boiler is connected to the air preheater, and the flue gas output from the tail end of the boiler serves as the heat source for the primary air in the air preheater.

Images