A low-carbon preparation system and method for calcined coal gangue composite clinker based on a cement production line

Abstract

The application discloses a kind of calcined coal gangue composite clinker low-carbon preparation system and preparation method based on cement production line, including cooling machine, vertical cylinder preheater, cyclone separator, prehydroxyl removal device, condenser and oil-water separator;The application proposes to use prehydroxyl removal device, combined with cooling machine to prepare composite clinker by calcining coal gangue, and the removed water does not enter the cement kiln firing system, and the prehydroxyl removal high-temperature coal gangue is calcined and activated in the cooling machine, the method is simple, has little effect on the cement kiln firing system, and the prepared calcined coal gangue active material has good quality and low cost, the coal gangue disposal amount is large, the heat value utilization rate is high, can reduce the energy consumption and carbon emission of cement industry, and has good economic benefit and social benefit.

Description

Technical Field

[0001] This invention relates to a low-carbon preparation system and method for calcined coal gangue composite clinker based on a cement production line, belonging to the field of coal gangue solid waste resource utilization. Background Technology

[0002] Coal gangue is a waste product generated during coal mining, producing 0.15-0.2 tons of gangue for every ton of raw coal produced. my country's cumulative coal gangue stockpiles have reached 4.5 billion tons, and are increasing by approximately 150-500 million tons annually. This massive stockpiling not only occupies vast amounts of land but also poses significant risks of geological disasters and land degradation.

[0003] A large portion of coal gangue is kaolin-type gangue, which, after proper calcination, can produce high-quality metakaolin with excellent pozzolanic activity. Coal gangue also possesses a certain calorific value, allowing it to save fuel in cement and clinker production. Even after calcination, coal gangue can still maintain good later-stage strength development when replacing cement clinker. This allows for a significant replacement of clinker and cement while ensuring the later-stage strength of concrete, thereby achieving energy conservation, emission reduction, and low-carbon development in the cement industry.

[0004] Currently, coal gangue is used as a raw material in cement clinker production. However, this process is prone to problems such as premature combustion of coal gangue in the kiln tail preheater system, preheater blockage, abnormal operation of the calcination system, and low effective utilization of calorific value. Furthermore, the significant fluctuations in the composition of coal gangue can easily affect the quality of cement clinker. In addition, due to its composition, the proportion of coal gangue in the raw material mix is ​​generally less than 10%. Therefore, the technological promotion of using coal gangue in cement production has been relatively slow.

[0005] The separate calcination of coal gangue generally suffers from several insurmountable drawbacks, including concentrated calcination flames, uneven heating and reaction of materials, high system energy consumption (heat and electricity), system scaling and blockage, excessive flue gas emissions, unstable product quality, and low pozzolanic activity. These shortcomings fail to meet the technical and economic requirements of coal gangue calcination, becoming a bottleneck restricting its production development and technological progress. Therefore, designing a simple, low-carbon, efficient, and safe reaction system is urgently needed to improve the efficiency and stability of coal gangue calcination systems, increase calorific value utilization, enhance pozzolanic activity, and reduce operating costs.

[0006] The cement kiln system cooler has significant advantages such as stable high-temperature operating conditions, sufficient oxygen, efficient cooling and heat recovery of hot materials, high-temperature hot air entering the rotary kiln and decomposition furnace, and medium-temperature hot air entering the waste heat boiler to recover heat for power generation. It can be fully utilized to solve the problem of coal gangue activation and calcination, while improving the calorific value utilization efficiency of coal gangue, and has good development prospects. Summary of the Invention

[0007] Purpose of the invention: The first purpose of this invention is to provide a low-carbon preparation system for calcined coal gangue composite clinker based on a cement production line. The second purpose of this invention is to use the low-carbon preparation system based on a cement production line to prepare a method for calcined coal gangue composite clinker.

[0008] Technical Solution: The present invention discloses a low-carbon preparation system for calcined coal gangue composite clinker based on a cement production line, comprising a cooler, wherein the cooler is equipped with a first exhaust air duct. The system further comprises a vertical preheater, a cyclone separator, a pre-dehydroxylation unit, a condenser, and an oil-water separator; the pre-dehydroxylation unit contains a first heat exchanger, the cooler is connected to the first heat exchanger via a third exhaust air duct, the lower air inlet of the vertical preheater is connected to the first heat exchanger via a pipe, and the air inlet of the cyclone separator is connected to... The air outlet of the vertical cylinder preheater is connected to the pipeline. The discharge port of the vertical cylinder preheater and the discharge port of the cyclone separator are both connected to the pre-dehydroxyl unit via pipelines. The discharge port of the pre-dehydroxyl unit is connected to the cooler via pipelines. The air outlet of the pre-dehydroxyl unit is connected to the condenser via pipelines. The drain port of the condenser is connected to the oil-water separator via pipelines. The air outlet of the condenser and the overflow port of the oil-water separator are both connected to the cooler via pipelines. The middle air inlet of the vertical cylinder preheater is connected to the cooler via a second excess air duct.

[0009] Furthermore, a second heat exchanger is provided inside the condenser.

[0010] Furthermore, the air outlet of the cyclone separator and the cooler are connected to the outside world through the first residual air duct.

[0011] Furthermore, the second excess air duct is equipped with a first valve, and the third excess air duct is equipped with a second valve.

[0012] Furthermore, a first airlock valve is provided on the pipe between the outlet of the vertical preheater and the pre-dehydroxylator, and a second airlock valve is provided on the pipe between the outlet of the cyclone separator and the pre-dehydroxylator.

[0013] Furthermore, a fan is provided at the inlet of the second heat exchanger.

[0014] Furthermore, a third valve is provided on the connecting pipe between the air outlet of the condenser and the cooler, a fourth valve is provided on the connecting pipe between the overflow port of the oil-water separator and the cooler, and a fifth valve is provided on the drain pipe at the bottom of the oil-water separator.

[0015] Furthermore, the cooler is provided with a feeding area, the outlet of the pre-dehydroxylator is connected to the feeding area through a pipe, and the outlet pipe of the pre-dehydroxylator is provided with a third airlock valve.

[0016] A method for preparing calcined coal gangue composite clinker using the low-carbon preparation system for calcined coal gangue composite clinker based on a cement production line as described in this invention includes the following steps:

[0017] A. Coal gangue enters the vertical preheater and undergoes a two-step gas-solid countercurrent heat exchange with hot air from the second exhaust air duct and hot air from the first heat exchanger. The hot air exiting the vertical preheater undergoes gas-solid separation in the cyclone separator and then flows into the first exhaust air duct. The preheated coal gangue in the vertical preheater and the coal gangue separated by the cyclone separator enter the pre-dehydroxylation unit together.

[0018] B. In the pre-dehydroxylation unit, the coal gangue passes through the first heat exchanger and exchanges heat between the gas and solid walls with the hot air from the third exhaust duct to complete the preheating and pre-dehydroxylation reaction. The pre-dehydroxylated coal gangue enters the cooler and reacts fully with the high-temperature air in the cooler to complete the combustion and calcination activation of the combustible material. The resulting calcined coal gangue active material and cement clinker are cooled in the cooler to obtain calcined coal gangue composite clinker.

[0019] C. The water vapor and a small amount of hydrocarbon-containing substances generated by the dehydroxylation of coal gangue in the pre-dehydroxylator enter the condenser through the air outlet pipe, where they are cooled by gas-solid heat exchange between the condenser and the cooling air, condensing into condensate. A small amount of gaseous hydrocarbons enter the cooler for high-temperature combustion, and the condensate enters the oil-water separator. A small amount of liquid hydrocarbons on the upper layer of the condensate enter the cooler for high-temperature combustion, and the condensate is discharged outside the boundary.

[0020] Furthermore, the gas temperature inside the second residual air duct is 450-500℃.

[0021] Furthermore, the gas temperature inside the third residual air duct is 600-550℃.

[0022] Coal gangue exhibits significant fluctuations in composition and unstable calorific value. Conventionally used as a raw material in cement production to prepare cement clinker, the ground coal gangue enters the calcination system along with the raw meal. This process suffers from problems such as scaling and blockage in the preheater system, affecting clinker quality and resulting in low coal gangue content and low calorific value utilization. This invention proposes using a pre-dehydroxylation unit combined with a cooler to calcine coal gangue to prepare composite clinker. The process is simple, low-cost, allows for large-scale coal gangue processing, and achieves high calorific value utilization. It can reduce energy consumption and carbon emissions in the cement industry, demonstrating significant economic and social benefits.

[0023] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages.

[0024] (1) Coal gangue undergoes a dehydroxylation reaction in an external pre-dehydroxylation device. The removed water does not enter the cement kiln firing system and does not affect the firing system.

[0025] (2) Coal gangue does not participate in clinker batching and has no impact on clinker quality.

[0026] (3) The combustible matter of coal gangue reacts with the hot air entering the kiln, which is equivalent to the pre-combustion of fuel with the same calorific value in the calcination system in the cooler. This does not increase the amount of exhaust gas in the cement kiln system, and at the same time, it can increase the temperature of the secondary and tertiary air entering the kiln, which is beneficial to the combustion of fuel in the calcination system. The calorific value of coal gangue is fully utilized, and it plays the role of a substitute fuel.

[0027] (4) The flue gas from the combustion enters the calcination system and does not require separate treatment, thus meeting the environmental emission requirements.

[0028] (5) The pre-dehydroxylated high-temperature coal gangue is calcined and activated in a cooler. The temperature field inside the cooler is uniform, the high-temperature air is in full contact with the material, the gas oxygen content is high, and the material residence time is long, which is conducive to the combustion of low-calorific-value fuels. The calcined coal gangue active material prepared is of good quality. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the low-carbon preparation system for calcined coal gangue composite clinker based on a cement production line according to the present invention. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0031] Example 1

[0032] like Figure 1 As shown, the low-carbon preparation system for calcined coal gangue composite clinker based on a cement production line according to the present invention includes a cooler 1, a vertical preheater 8, a cyclone separator 9, a pre-dehydroxylation device 12, a condenser 14, and an oil-water separator 18. The cooler 1 is equipped with a first waste air duct 3, a second waste air duct 4, and a third waste air duct 5. The pre-dehydroxylation unit 12 contains a first heat exchanger 13. The cooler 1 is connected to the first heat exchanger 13 via the third waste air duct 5. The outlet of the vertical preheater 8 is connected to the cyclone separator 9 via a pipe. The lower air inlet of the vertical preheater 8 is connected to the first heat exchanger 13 via a pipe. The discharge outlets of the vertical preheater 8 and the cyclone separator 9 are both connected to the pre-dehydroxylation unit 12 via pipes. The discharge outlet of the pre-dehydroxylation unit 12 is connected to the cooler 1 via a pipe. The air outlet of the pre-dehydroxylation unit 12 is connected to the condenser 14 via a pipe. The drain pipe of the condenser 14 is connected to the oil-water separator 18. The air outlet of the condenser 14 is connected to the cooler 1 via a pipe. The second waste air duct 4 connects to the middle air inlet of the vertical preheater 8 and the cooler 1. The cooler 1 and the cyclone separator 9 are connected to the outside via the first waste air duct 3. The overflow port of the oil-water separator 18 is connected to the cooler 1 through a pipe, and the drain port of the oil-water separator 18 is connected to the outside.

[0033] The cooler 1 and the first waste air duct 3 are existing technologies in cement production lines. The second waste air duct 4 is equipped with a first valve 6 to control the airflow and prevent excessive airflow that could cause low-temperature waste air to enter the vertical preheater 8. The third waste air duct 5 is equipped with a second valve 7 to control the airflow and prevent excessive airflow that could cause low-temperature waste air to enter the first heat exchanger 13. The lower part of the vertical preheater 8 receives hot air from the first heat exchanger 13, with a temperature of 450-500℃. The middle part receives hot air from the second waste air duct 4, with a temperature of 350-400℃. The raw materials fed in from the top undergo counter-current heat exchange with the high-temperature air, thus preheating the materials. A first airlock valve 10 is installed on the pipe between the outlet of the vertical preheater 8 and the pre-dehydroxylation unit 12 to stabilize the material discharge and also to lock the airflow, preventing air leakage between the vertical preheater 8 and the pre-dehydroxylation unit 12. Cyclone separator 9 serves to separate the gas and solid components of the material. A second airlock valve 11 is installed on the pipe between the outlet of cyclone separator 9 and pre-dehydroxylation unit 12 to stabilize the material discharge and also to lock the airflow between the cyclone separator 9 and the pre-dehydroxylation unit 12. The pre-dehydroxylation unit 12 contains a first heat exchanger 13, with hot air supplied from the third exhaust air duct 5 at a temperature of 600-650℃, enabling the coal gangue to complete the dehydroxylation reaction. A third airlock valve 21 is installed on the pipe between the outlet of the pre-dehydroxylation unit 12 and the cooler 1 to stabilize the material discharge and also to lock the airflow between the pre-dehydroxylation unit 12 and the cooler 1. The outlet of the pre-dehydroxylator 12 is connected to the feeding zone 2 of the cooler 1 via a pipeline. The gas temperature in the feeding zone 2 is 850-900℃. The high-temperature air comes into full contact with the pre-dehydroxylated coal gangue, resulting in a high oxygen content and a long material residence time, ensuring complete combustion of the combustibles in the coal gangue. The stable air supply from the cooler also ensures that the coal gangue does not overheat and reduce its activity quality. A second heat exchanger 15 is installed inside the condenser 14. A fan 16 is installed at the inlet of the second heat exchanger 15 to supply cooling air for cooling the gas produced by the decomposition of the pre-dehydroxylator 12. A third valve 17 is installed on the connecting pipeline between the outlet of the condenser 14 and the cooler 1, used to introduce a small amount of gaseous hydrocarbons from the condenser 14 into the cooler 1 for high-temperature combustion. A fourth valve 19 is installed on the connecting pipeline between the overflow port of the oil-water separator 18 and the cooler 1, used to introduce a small amount of liquid hydrocarbons from the upper layer of the condensate into the cooler 1 for high-temperature combustion. The drain pipe at the bottom of the oil-water separator 18 is equipped with a fifth valve 20, which is used to drain the condensate.

[0034] A low-carbon preparation method for calcined coal gangue composite clinker based on a cement production line, the specific working process of which includes:

[0035] A. Coal gangue enters the vertical preheater 8, where it undergoes a two-step countercurrent gas-solid heat exchange with 350-400℃ hot air from the second exhaust air duct 4 and 450-500℃ hot air from the first heat exchanger 13, preheating it to 450-500℃. The hot air exiting the vertical preheater 8 undergoes gas-solid separation in the cyclone separator 9 and then flows into the first exhaust air duct 3 for discharge outside the boundary. The preheated coal gangue from the outlet of the vertical preheater 8 and the coal gangue separated by the cyclone separator 9 together enter the pre-dehydroxylation unit 12.

[0036] B. In the pre-dehydroxylation unit 12, the coal gangue passes through the first heat exchanger 13 and undergoes gas-solid heat exchange with the 600-650℃ hot air from the third exhaust air duct 5 to complete the preheating and pre-dehydroxylation reaction. The pre-dehydroxylated coal gangue enters the feeding zone 2 of the cooler 1 and reacts fully with the high-temperature air at 850-900℃ in the feeding zone 2 to complete the combustion and calcination activation of the combustible material. The calcined coal gangue active material is then cooled with cement clinker in the cooler 1 to obtain calcined coal gangue composite clinker.

[0037] C. The water vapor and a small amount of hydrocarbon-containing substances generated by the dehydroxylation of coal gangue in the pre-dehydroxylator 12 at about 450-500℃ enter the condenser 14 through the air outlet pipe. They are cooled to 90℃ by gas-solid heat exchange with the cooling air through the second heat exchanger 15 and condense into liquid to become condensate. A small amount of gaseous hydrocarbons enter the cooler 1 for high-temperature combustion. The condensate enters the oil-water separator 18. A small amount of liquid hydrocarbons on the upper layer of the condensate enters the cooler 1 for high-temperature combustion. The condensate is discharged outside the boundary.

[0038] For cement clinker production lines, coal gangue does not participate in clinker batching and has no impact on clinker quality. The coal gangue undergoes a dehydroxylation reaction within an external pre-dehydroxylation unit 12. The removed moisture does not enter the cement kiln calcination system and has no impact on the calcination system. The combustible matter of the coal gangue reacts with the hot air entering the kiln, equivalent to the pre-combustion of fuel with the same calorific value in the calcination system within the cooler 1. This does not increase the exhaust gas volume of the cement kiln system and simultaneously increases the temperature of the secondary and tertiary air entering the kiln, which is beneficial for fuel combustion in the calcination system. The calorific value of the coal gangue is fully utilized, serving as a substitute fuel. The combustion flue gas enters the calcination system and does not require separate treatment, meeting environmental emission requirements.

Claims

1. A low-carbon preparation system for calcined coal gangue composite clinker based on a cement production line, comprising a cooler (1), wherein the cooler (1) is provided with a first exhaust air duct (3), characterized in that, The system also includes a vertical preheater (8), a cyclone separator (9), a pre-dehydroxylator (12), a condenser (14), and an oil-water separator (18); the pre-dehydroxylator (12) is equipped with a first heat exchanger (13), the cooler (1) is connected to the first heat exchanger (13) through a third exhaust air duct (5), the lower air inlet of the vertical preheater (8) is connected to the first heat exchanger (13) through a pipe, the air inlet of the cyclone separator (9) is connected to the air outlet of the vertical preheater (8) through a pipe, and the discharge port of the vertical preheater (8) and the cyclone separator (9) are connected to the cyclone separator (9) through a pipe. The discharge port of the separator (9) is connected to the pre-dehydroxylator (12) through a pipe. The discharge port of the pre-dehydroxylator (12) is connected to the cooler (1) through a pipe. The air outlet of the pre-dehydroxylator (12) is connected to the condenser (14) through a pipe. The drain port of the condenser (14) is connected to the oil-water separator (18) through a pipe. The air outlet of the condenser (14) and the overflow port of the oil-water separator (18) are both connected to the cooler (1) through pipes. The middle air inlet of the vertical cylinder preheater (8) is connected to the cooler (1) through the second excess air duct (4).

2. The low-carbon preparation system for calcined coal gangue composite clinker based on a cement production line according to claim 1, characterized in that, The condenser (14) is equipped with a second heat exchanger (15).

3. The low-carbon preparation system for calcined coal gangue composite clinker based on a cement production line according to claim 1, characterized in that, The air outlet of the cyclone separator (9) and the cooler (1) are connected to the outside world through the first residual air duct (3).

4. The low-carbon preparation system for calcined coal gangue composite clinker based on a cement production line according to claim 1, characterized in that, The second residual air duct (4) is equipped with a first valve (6), and the third residual air duct (5) is equipped with a second valve (7).

5. The low-carbon preparation system for calcined coal gangue composite clinker based on a cement production line according to claim 1, characterized in that, A first airlock valve (10) is provided on the pipe between the outlet of the vertical preheater (8) and the pre-dehydroxylizer (12), and a second airlock valve (11) is provided on the pipe between the outlet of the cyclone separator (9) and the pre-dehydroxylizer (12).

6. The low-carbon preparation system for calcined coal gangue composite clinker based on a cement production line according to claim 2, characterized in that, The second heat exchanger (15) is equipped with a fan (16) at its inlet.

7. The low-carbon preparation system for calcined coal gangue composite clinker based on a cement production line according to claim 1, characterized in that, A third valve (17) is provided on the connecting pipe between the air outlet of the condenser (14) and the cooler (1), a fourth valve (19) is provided on the connecting pipe between the overflow port of the oil-water separator (18) and the cooler (1), and a fifth valve (20) is provided on the drain pipe at the bottom of the oil-water separator (18).

8. The low-carbon preparation system for calcined coal gangue composite clinker based on a cement production line according to claim 1, characterized in that, The cooler (1) is provided with a feeding area (2), and the outlet of the pre-dehydroxylator (12) is connected to the feeding area (2) through a pipe. The outlet pipe of the pre-dehydroxylator (12) is provided with a third airlock valve (21).

9. A method for preparing calcined coal gangue composite clinker using the calcined coal gangue composite clinker low-carbon preparation system based on a cement production line as described in claim 1, comprising the following steps: A. Coal gangue enters the vertical preheater (8) and undergoes two-step gas-solid countercurrent heat exchange with hot air from the second exhaust air duct (4) and hot air from the first heat exchanger (13). The hot air exiting the vertical preheater (8) undergoes gas-solid separation through the cyclone separator (9) and then flows into the first exhaust air duct (3) to be discharged outside the boundary. The coal gangue preheated in the vertical preheater (8) and the coal gangue separated by the cyclone separator (9) enter the pre-dehydroxylation unit (12) together. B. In the pre-dehydroxylator (12), the coal gangue passes through the first heat exchanger (13) and exchanges heat between the gas and solid walls with the hot air from the third exhaust air duct (5) to complete the pre-dehydroxyl reaction. The pre-dehydroxylated coal gangue enters the cooler (1) and reacts fully with the high-temperature air in the cooler (1) to complete the combustion and calcination activation of the combustible. The calcined coal gangue active material and cement clinker are cooled in the cooler (1) to obtain calcined coal gangue composite clinker. C. The water vapor and a small amount of hydrocarbon-containing substances generated by the dehydroxylation of coal gangue in the pre-dehydroxylator (12) enter the condenser (14) through the air outlet pipe, and are cooled by gas-solid heat exchange with the cooling air, condensing into condensate. A small amount of gaseous hydrocarbons enter the cooler (1) for high-temperature combustion, and the condensate enters the oil-water separator (18). A small amount of liquid hydrocarbons on the upper layer of the condensate enter the cooler (1) for high-temperature combustion, and the condensate is discharged outside the boundary.

10. The method according to claim 9, characterized in that, The gas temperature in the second residual air duct (4) is 450-500℃, and the gas temperature in the third residual air duct (5) is 600-550℃.

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