Pulverized coal preparation method

Abstract

The invention relates to the technical field of pulverized coal preparation, and discloses a pulverized coal preparation method which comprises the following steps: S1, crushing raw coal in a coal mill, mixing the obtained pulverized coal with hot carrier gas, and filtering the hot carrier gas carrying the pulverized coal in a pulverized coal collector to obtain hot waste carrier gas and pulverized coal; s2, the hot waste carrier gas and cold nitrogen are subjected to heat exchange in a winding type pipeline heater, and condensate, cooled waste carrier gas and hot nitrogen are obtained; s3, one part of the cooled waste carrier gas enters a hot blast stove to be heated and then enters a coal mill to serve as hot carrier gas to be recycled, and the other part of the cooled waste carrier gas enters the coal mill to serve as sealing gas to be utilized; and S4, conveying the pulverized coal into a gasification powder bin through hot nitrogen. According to the invention, the whole process flow of the pulverized coal is optimized, the heat of the hot waste carrier gas and the waste carrier gas are recycled, the condensate which can be used for the second time is also generated, and meanwhile, the steam consumption and the low-pressure nitrogen consumption of chemical enterprises are reduced, so that the environmental pollution can be effectively reduced, and the energy consumption is reduced.

Description

Technical Field

[0001] This invention relates to the field of coal powder preparation technology, and specifically to a method for preparing coal powder. Background Technology

[0002] Currently, the coal powder grinding and drying unit in dry coal gasification technology generally adopts a "one-stage coal grinding and drying and one-stage coal powder separation and collection" approach. Coal powder drying, as an indispensable part of coal processing, plays a crucial role in the efficient utilization of coal and the sustainable development of enterprises. In the current coal powder preparation process, the raw coal is first finely pulverized through a mill to form fine coal powder. Then, the hot waste gas carrying the coal powder is filtered through a coal powder collector. The collected coal powder is then transported to a conveying system, where a hot nitrogen carrier delivers the coal powder into the gasification silo. The filter bags in the coal powder collector play a key role, effectively filtering out impurities in the hot gas to ensure that the coal powder meets the required quality standards.

[0003] However, in this process, after the hot carrier gas passes through the filter bag, a portion is drawn into the circulating fan through the outlet pipe, pressurized by the fan, and sent back to the hot blast furnace, achieving the recycling of the carrier gas; while the other portion (about 20-30%) is directly vented into the air. This vented gas contains a large amount of water vapor, heat, and inert gases. If this waste hot carrier gas is directly discharged on-site, it will not only lead to a large waste of heat and water resources, but also increase the burden on the environment and have adverse effects. Therefore, how to maximize the utilization of resources (flow rate and heat) in the waste gas while ensuring production efficiency and mitigating the environmental impact has become an urgent problem to be solved in current pulverized coal preparation processes. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem that the existing technology cannot fully recover and utilize the waste heat carrier gas, resulting in resource waste and increased environmental burden, and to provide an energy-saving and environmentally friendly method for preparing pulverized coal. This method has a simple process, high system medium recovery rate, and is easy to operate. While meeting the requirements of energy conservation and environmental protection, it can reduce operating and maintenance costs.

[0005] To achieve the above objectives, the present invention provides a method for preparing pulverized coal, the method comprising the following steps:

[0006] S1. Raw coal is crushed in a coal mill, and the resulting coal powder is mixed with hot carrier gas. The hot carrier gas carrying the coal powder enters the coal powder collector for filtration to obtain hot waste carrier gas and coal powder.

[0007] S2. The hot waste carrier gas and cold nitrogen enter the wound pipe heater for heat exchange to obtain condensate, cooled waste carrier gas and hot nitrogen.

[0008] S3. Part of the cooled waste carrier gas is heated in a hot blast stove and then enters the coal mill as hot carrier gas for recycling. The other part enters the coal mill as sealing gas.

[0009] S4. The pulverized coal from step S1 is transported to the gasification pulverizer via hot nitrogen.

[0010] Preferably, the wound pipe heater includes a housing, in which a wound pipe is disposed, the wound pipe having a cold nitrogen inlet and a hot nitrogen outlet, and the housing having a hot waste gas inlet, a cold waste gas outlet and a condensate outlet.

[0011] Preferably, the inner diameter of the shell is 1.5 to 2.6 meters, and the inner diameter of the spiral pipe is 15 to 25 centimeters.

[0012] Preferably, the spiral-wound pipe extends along the axial direction of the housing and spirals around the axis of the housing.

[0013] Preferably, the nitrogen content is 80-90% based on the total molar amount of the waste heat carrier gas.

[0014] Preferably, the moisture content of the waste heat carrier gas is 35-45%.

[0015] Preferably, in step S2, the temperature of the hot waste carrier gas is 115-125°C, and the temperature of the cooled waste carrier gas obtained after heat exchange is 60-70°C.

[0016] Preferably, in step S2, the temperature of the cold nitrogen gas is 20-30°C, and the temperature of the hot nitrogen gas obtained after heat exchange is 90-100°C.

[0017] Preferably, in step S2, the flow rate ratio of the hot waste carrier gas to the cold nitrogen gas is 35 to 35:1.

[0018] Preferably, in step S3, 70-80% of the cooled waste carrier gas is heated in a hot blast stove and then returned to the coal mill as hot carrier gas for recycling.

[0019] In the technical solution provided by this invention, the hot waste carrier gas after pulverized coal drying is transported to a wound-type pipe heater for heat exchange with cold nitrogen. This fully utilizes the heat of the hot waste carrier gas to heat the nitrogen. The resulting hot nitrogen is used to send the pulverized coal in the conveying system into the gasification silo. This eliminates the need for a low-pressure steam heater used to heat the cold nitrogen in the original preparation process, saving energy. Part of the cooled waste carrier gas is returned to the coal mill for recycling, while the other part is used as the sealing gas for the coal mill, replacing the cold nitrogen used in the original coal mill sealing system. Therefore, the pulverized coal preparation method of this invention, through optimization of the overall pulverized coal process, recycles and reuses the heat of the hot waste carrier gas and the waste carrier gas itself, and also produces reusable condensate. Simultaneously, it reduces the amount of steam and low-pressure nitrogen consumed by chemical enterprises, thereby effectively reducing environmental pollution, lowering energy consumption, and promoting sustainable resource utilization. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of one embodiment of a coal powder preparation system for implementing the coal powder preparation method of the present invention;

[0021] Figure 2 yes Figure 1 A schematic diagram of the structure of the spiral pipe heater.

[0022] Explanation of reference numerals in the attached figures

[0023] 1-Raw coal bunker; 2-Weighing coal feeder; 3-Coal mill; 4-Pulverized coal collector; 5-Wound pipe heater; 6-Circulating fan; 7-Clotted liquid drainer; 8-Hydraulic coupler; 9-Hot blast furnace;

[0024] 51-Shell; 52-Wound pipe. Detailed Implementation

[0025] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] In the current coal powder preparation process, the coal powder drying technology has the following defects: (1) During the coal powder preparation process, about 20-30% of the hot waste carrier gas is directly discharged into the atmosphere. The heat energy and other valuable components in the waste carrier gas are difficult to be effectively utilized, which reduces the energy efficiency of the entire production system; (2) There are many inert gases with high calorific value, which are difficult to recover and utilize: The waste carrier gas in coal powder preparation also contains a large amount of inert gases (such as nitrogen). Although these gases do not have direct combustion value, their presence makes the overall calorific value of the waste carrier gas high. However, due to technical limitations, the existing waste carrier gas system is difficult to efficiently separate and effectively utilize these heat energies and inert gases, resulting in a large amount of energy being wasted; (3) Direct discharge on site is uneconomical and environmentally unfriendly: The discharge of hot carrier gas carrying a large amount of water vapor will cause the water vapor to react with acidic gases in the air, thereby causing irreversible damage to nearby equipment and facilities, and indirectly increasing the maintenance costs of the equipment and facilities.

[0028] In view of this, the present invention provides a method for preparing pulverized coal, the method comprising the following steps:

[0029] S1. Raw coal is crushed in coal mill 3. The resulting coal powder is mixed with hot carrier gas. The hot carrier gas carrying the coal powder enters coal powder collector 4 for filtration to obtain hot waste carrier gas and coal powder.

[0030] S2. The hot waste carrier gas and cold nitrogen enter the wound pipe heater 5 for heat exchange to obtain condensate, cooled waste carrier gas and hot nitrogen.

[0031] S3. Part of the cooled waste carrier gas enters the hot air furnace 9 for heating and then enters the coal mill 3 as hot carrier gas for recycling. The other part enters the coal mill 3 as sealing gas.

[0032] S4. The pulverized coal from step S1 is transported to the gasification silo via the hot nitrogen from step S2.

[0033] Current pulverized coal preparation processes require a large amount of hot nitrogen (approximately 4500 Nm³ per line, which is then heated by a specially designed low-pressure steam heater). 3 The coal powder in the conveying system is sent to the gasifier in the gasification silo using nitrogen heated to approximately 100°C at room temperature. Simultaneously, due to its structural design, the coal mill 3 must use a portion of cold nitrogen (inert gas) as a sealing gas for the rotating equipment during the pulverizing process. Therefore, traditional coal powder preparation processes not only require the additional use of cold nitrogen as a sealing gas but also a dedicated heater to heat the nitrogen as the conveying gas, resulting in high energy consumption and significant pollution. This invention optimizes and upgrades the traditional coal powder preparation process in terms of environmental protection and energy conservation, not only fully meeting the downstream coal powder product specifications but also improving process optimization, investment reduction, and energy efficiency.

[0034] The coal powder preparation method of this invention adds a wound-type pipe heater 5 to the original process flow. Cold nitrogen gas and hot waste carrier gas from the coal powder collector 4 exchange heat in the wound-type pipe heater 5. The hot nitrogen gas after heat exchange can send the coal powder in the conveying system into the gasification silo, eliminating the need for a low-pressure steam heater used to heat the cold nitrogen gas in the original process and saving energy. A portion of the cooled waste carrier gas enters the coal mill 3 as sealing gas, replacing the original approximately 6000 Nm³ of gas. 3 The amount of cold nitrogen used is [amount] / h, with a portion returned to the coal mill 3 as a recycle heat carrier gas. The condensate obtained during the heat exchange process can be reused, reducing the company's reliance on external water resources. Therefore, the coal powder preparation method described in this invention is complete, highly integrated, environmentally friendly in its design, and highly operable. It not only significantly improves the secondary closed-loop utilization of heat and resources but also effectively reduces environmental pollution, fully utilizes heat, and reduces energy consumption, providing strong technical support for achieving green and sustainable development.

[0035] For ease of description, the cooled waste carrier gas may also be referred to as cold carrier gas in this article.

[0036] In this invention, the coal powder preparation method is implemented in a coal powder preparation system, please refer to the following: Figure 1 In some embodiments, the pulverized coal preparation system includes: a raw coal bunker 1, a weighing feeder 2, a coal mill 3, a pulverized coal collector 4, a wound-type pipe heater 5, a circulating fan 6, a condensate drain bag 7, a hydraulic coupler 8, a hot air furnace 9, a sending system (not shown in the figure), and a gasification pulverized coal bunker (not shown in the figure), wherein the raw coal bunker 1, the weighing feeder 2, the coal mill 3, the pulverized coal collector 4, and the wound-type pipe heater 5 are connected in sequence.

[0037] Please refer to the following: Figure 2 In a preferred embodiment, the wound-type pipe heater 5 includes a housing 51, within which a wound-type pipe 52 is disposed. The wound-type pipe 52 has a cold nitrogen inlet and a hot nitrogen outlet, while the housing 51 has a hot waste gas inlet, a cold waste gas outlet, and a condensate outlet. Specifically, cold nitrogen enters the wound-type pipe 52 through the cold nitrogen inlet, and hot waste gas enters the housing 51 through the hot waste gas inlet. The cold nitrogen and hot waste gas exchange heat internally through indirect contact. The heated nitrogen is then output from the hot nitrogen outlet, the cooled waste gas is output from the cold waste gas outlet, and the condensate from the cooled hot waste gas is output from the condensate outlet.

[0038] In one specific embodiment, the condensate outlet is connected to the condensate collection bag 7, so that the condensate from the spiral pipe heater 5 enters the condensate collection bag 7 for collection and can then enter the plant's condensate system for use in other equipment systems, thereby reducing the use of external water resources in the plant area.

[0039] In a preferred embodiment, the inner diameter of the shell 51 is 1.5 to 2.6 meters, and the inner diameter of the spiral pipe is 15 to 25 centimeters. Within the above size range, the heat exchange effect of cold nitrogen and hot waste carrier gas is better.

[0040] More preferably, the inner diameter of the housing 51 is 1.52 to 2.54 meters (60 to 100 inches), and the inner diameter of the spiral pipe is 15.24 to 20.32 centimeters (6 to 8 inches).

[0041] In order to increase the contact area between cold nitrogen and hot waste carrier gas, in a preferred embodiment, the spiral pipe 52 extends in the axial direction of the housing 51 and spirals around the axis of the housing 51.

[0042] More preferably, the spiral pipe 52 is spirally wrapped around the axis of the housing 51 and fits against the inner wall of the housing 51.

[0043] In the method described in this invention, the main components of the waste heat carrier gas are nitrogen and water vapor.

[0044] In some embodiments, the nitrogen (N2) content is 80-90% based on the total molar amount of the waste heat carrier gas.

[0045] In some embodiments, the carbon dioxide (CO2) content is 5-6% based on the total molar amount of the waste heat carrier gas.

[0046] In one specific embodiment, based on the total molar amount of the hot waste carrier gas, the content of nitrogen (N2) is 80-90%, the content of carbon dioxide (CO2) is 5-6%, the total content of oxygen (O2) and argon (Ar) is 5-7%, and the content of hydrogen (H2) is less than 0.01%.

[0047] In some embodiments, the moisture content of the waste heat carrier gas is 35-45%.

[0048] In some embodiments, in step S2, the temperature of the cold nitrogen gas is 20-30°C, and the temperature of the hot nitrogen gas obtained after heat exchange is 90-100°C. In this way, the hot nitrogen gas meets the temperature requirements for conveying pulverized coal to the gasification silo, and the conveying effect is good, and the pulverized coal is not easy to stick together.

[0049] In some embodiments, in step S2, the flow rate ratio of the hot waste carrier gas to the cold nitrogen is 25-35:1. Within this flow rate range, the hot nitrogen obtained after heat exchange can be guaranteed to meet the requirements for conveying pulverized coal to the gasification coal bunker. Specifically, the flow rate ratio of the hot waste carrier gas delivered to the shell 51 of the wound-wound pipe heater 5 to the flow rate of the cold nitrogen delivered to the wound-wound pipe in the wound-wound pipe heater 5 is 25-35:1.

[0050] In the most preferred embodiment, in step S2, the flow rate ratio of the hot waste carrier gas to the cold nitrogen gas is 30:1.

[0051] In a specific implementation, the inlet of the circulating fan 6 is connected to the outlet of the cold carrier gas, and the outlet of the circulating fan 6 is connected to the hot blast stove 9 and the coal mill 3 respectively.

[0052] In a specific implementation, the circulating fan 6 is powered by a hydraulic coupler 8.

[0053] In a specific implementation, step S3 includes: the cooled waste carrier gas enters the circulating fan 6, a portion of which enters the hot air furnace 9 for heating and then returns to the coal mill 3 as hot carrier gas for recycling, and another portion enters the coal mill 3 as sealing gas for use.

[0054] In a preferred embodiment, in step S3, 70-80% of the cooled waste carrier gas is heated in the hot blast stove 9 and then returned to the coal mill 3 as hot carrier gas for recycling.

[0055] In some implementations, step S4 specifically includes: the coal powder collected in step S1 enters the conveying system, and the hot nitrogen obtained in step S2 transports the coal powder in the conveying system to the gasification pulverizer for use in the gasifier.

[0056] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available products.

[0057] Example

[0058] This embodiment uses a pulverized coal preparation system (see reference). Figure 1 The coal powder preparation system includes a raw coal bunker 1, a weighing feeder 2, a coal mill 3, a coal powder collector 4, and a wound-type pipe heater 5 connected in sequence. The coal mill 3 has a sealed gas inlet and a hot carrier gas inlet.

[0059] The wound pipe heater 5 (refer to) Figure 2The device includes a housing 51, within which a spiral-wound pipe 52 is installed. The spiral-wound pipe 52 extends along the axial direction of the housing 51 and spirally wraps around the axis of the housing 51. The spiral-wound pipe 52 has a cold nitrogen inlet and a hot nitrogen outlet. The housing 51 has a hot waste gas inlet, a condensate outlet, and a cold waste gas outlet. The hot nitrogen outlet is connected to a conveying system for conveying pulverized coal in the conveying system to the gasification pulverizer. The condensate outlet is connected to a condensate drain bag 7. The cold waste gas outlet is connected to the inlet of a circulating fan 6. The outlet of the circulating fan 6 is connected to a hot air furnace 9 and a coal mill 3, respectively. The circulating fan 6 is powered by a hydraulic coupler 8. In the spiral-wound pipe heater 5, the inner diameter of the housing 51 is 2.24 meters, and the inner diameter of the spiral-wound pipe is 15.24 centimeters.

[0060] In this embodiment, the composition of the waste heat carrier gas is shown in Table 1 below:

[0061] Table 1

[0062] <![CDATA[H2,%(mol / mol)]]> <![CDATA[CO2,%(mol / mol)]]> <![CDATA[O2+Ar,%(mol / mol)]]> <![CDATA[N2,%(mol / mol)]]> Moisture content, % ＜0.01 5.58 6.79 87.61 39.4

[0063] The method for preparing pulverized coal includes the following steps:

[0064] S1. The raw coal in the raw coal bunker 1 is transported to the coal mill 3 by the weighing coal feeder 2. The raw coal is crushed in the coal mill 3 to obtain coal powder. The hot carrier gas enters the coal mill 3 through the hot carrier gas inlet for drying and carrying the coal powder. The hot carrier gas carrying the coal powder is sent to the coal powder collector 4 through the pipeline for filtration to obtain hot waste carrier gas (composition as shown in Table 1) at a temperature of 115-125℃ and coal powder. The coal powder enters the conveying system.

[0065] S2. The hot waste carrier gas (115-125°C) obtained from the filtration in step S1 enters the shell 51 of the wound-type pipe heater 5 through the hot waste carrier gas inlet. Cold nitrogen gas (20-30°C) enters the wound-type pipe 52 of the wound-type pipe heater 5 through the cold nitrogen inlet, allowing indirect heat exchange between the cold nitrogen gas and the hot waste carrier gas inside. After heat exchange, hot nitrogen gas (90-100°C), cold carrier gas (cooled waste carrier gas) (60-70°C), and condensate are obtained. The flow rate of the hot waste carrier gas entering the wound-type pipe heater 5 is approximately 135,000 Nm³. 3 The flow rate of cold nitrogen entering the wound-type pipe heater 5 is approximately 4500 Nm³ / h. 3 / h;

[0066] S3. The cold carrier gas obtained in step S2 enters the circulating fan 6. 70-80% of the cold carrier gas in the circulating fan 6 is sent to the hot blast stove 9 and heated to 310-320℃. After being heated, it re-enters the coal mill 3 through the hot carrier gas inlet as hot carrier gas, and this cycle continues. 20-30% of the cold carrier gas in the circulating fan 6 is sent into the coal mill 3 through the sealing machine as sealing gas (replacing the original approximately 6000 Nm³).3 / h cold nitrogen dosage);

[0067] S4. The hot nitrogen gas (90-100℃) obtained in step S2 enters the sending system and serves as the carrier of the pulverized coal sending system, sending the pulverized coal in the sending system into the gasification silo for use in the gasifier.

[0068] S5. The condensate obtained in step S2 enters the condensate drain bag 7 through the condensate outlet, and then enters the condensate system, which can be used for water supply in other device systems.

[0069] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing pulverized coal, characterized in that, The method includes the following steps: S1. The raw coal is crushed in the coal mill (3), and the resulting coal powder is mixed with the hot carrier gas. The hot carrier gas carrying the coal powder enters the coal powder collector (4) for filtration to obtain hot waste carrier gas and coal powder. S2. The hot waste carrier gas and cold nitrogen enter the wound pipe heater (5) for heat exchange to obtain condensate, cooled waste carrier gas and hot nitrogen. S3. Part of the cooled waste carrier gas enters the hot air furnace (9) for heating and then enters the coal mill as hot carrier gas for recycling, and the other part enters the coal mill (3) as sealing gas. S4. The pulverized coal from step S1 is transported to the gasification pulverizer via hot nitrogen.

2. The method according to claim 1, characterized in that, The wound pipe heater (5) includes a housing, and a wound pipe (52) is provided inside the housing (51). The wound pipe (52) has a cold nitrogen inlet and a hot nitrogen outlet. The housing (51) has a hot waste gas inlet, a cold gas outlet and a condensate outlet.

3. The method according to claim 2, characterized in that, The inner diameter of the shell (51) is 1.5 to 2.6 meters, and the inner diameter of the spiral pipe (52) is 15 to 25 centimeters.

4. The method according to claim 2 or 3, characterized in that, The spiral pipe (52) extends along the axial direction of the housing (51) and spirals around the axis of the housing (51).

5. The method according to any one of claims 1-4, characterized in that, Based on the total molar amount of the aforementioned waste heat carrier gas, the nitrogen content is 80-90%.

6. The method according to claim 1 or 5, characterized in that, The moisture content of the waste heat carrier gas is 35-45%.

7. The method according to any one of claims 1-6, characterized in that, In step S2, the temperature of the hot waste carrier gas is 115-125°C, and the temperature of the cooled waste carrier gas obtained after heat exchange is 60-70°C.

8. The method according to claim 1 or 7, characterized in that, In step S2, the temperature of the cold nitrogen gas is 20-30°C, and the temperature of the hot nitrogen gas obtained after heat exchange is 90-100°C.

9. The method according to any one of claims 1-8, characterized in that, In step S2, the flow rate ratio of the hot waste carrier gas to the cold nitrogen gas is 35 to 35:

1.

10. The method according to any one of claims 1-9, characterized in that, In step S3, 70-80% of the cooled waste carrier gas enters the hot blast stove (9) for heating and then returns to the coal mill (3) as hot carrier gas for recycling.

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