A cement burning system and method capable of achieving local full oxygen combustion carbon enrichment

Abstract

The present invention discloses a cement burning system and method capable of realizing partial full oxygen combustion carbon enrichment, which consists of a cement calcination main system and a full oxygen combustion subsystem. In the preheating and predecomposition link, the main system and the subsystem operate in parallel; in the rotary kiln, the calcined raw materials produced by the main system and the subsystem are simultaneously fed into the kiln to produce cement clinker; thus reducing the mutual interference between the main system and the subsystem. In the full oxygen combustion subsystem, the raw material decomposition process is divided into a primary combustion zone and a secondary combustion zone for series operation. Raw materials are not fed into the primary combustion zone, and the medium and low temperature circulating flue gas is heated to above 900°C. The secondary combustion zone is operated with materials, and the high temperature circulating flue gas is introduced into the secondary combustion zone for raw material decomposition, thereby realizing safe and stable ignition and combustion of pulverized coal under full oxygen combustion, fully decomposing the raw materials, and suppressing NOx from pulverized coal combustion. X Release; the oxy-fuel combustion subsystem takes circulating air in stages to ensure the safety of pulverized coal transportation while improving heat recovery, reducing energy consumption and achieving carbon enrichment.

Description

Technical Field

[0001] The present invention relates to the technical field of cement burning, in particular to a cement burning system and method capable of realizing carbon enrichment through local full oxygen combustion. Background Art

[0002] Oxyfuel combustion, based on existing industrial furnace systems, replaces combustion air with high-purity oxygen. Flue gas recirculation regulates the furnace's flow rate and heat transfer characteristics, resulting in flue gas with a CO2 concentration of up to 80% by volume. This allows for the permanent storage or resource utilization of CO2 at a relatively low cost after capture and purification, enabling large-scale industrial CO2 enrichment and emission reduction. Existing analysis shows that compared to other carbon capture methods, oxyfuel combustion technology offers advantages in terms of investment cost, operating cost, CO2 emission reduction costs, scalability, and compatibility with existing technologies.

[0003] Existing oxy-fuel burners are mostly used in float glass kilns, fiberglass kilns, steel rolling mill heating furnaces, forging furnaces, and heat treatment furnaces, primarily fueled by natural gas. Coal-fired oxy-fuel burners are rarely used in industry. Chinese Patent Publication No. CN101825278A proposes an oxygen-enriched burner, and U.S. Patent No. US20110126780A1 proposes a pulverized coal burner for oxy-fuel combustion boilers. These two patents primarily focus on oxy-fuel combustion in coal-fired power generation boilers. Cement industry kilns differ significantly from glass and thermal power kilns in production layout and reaction conditions, and require specialized design for coolers and system airflow. Currently, there are no actual cases of pure oxygen combustion technology being put into operation in the cement industry.

[0004] The cement production process produces a large amount of carbon dioxide. According to statistics, the production of 1 ton of cement will emit 0.6 to 0.7 tons of carbon dioxide. The carbon dioxide in cement kiln exhaust gas mainly comes from the following two aspects:

[0005] 1. Carbon dioxide generated in the flue gas from fuel combustion accounts for about 40%;

[0006] 2. Carbon dioxide produced by the decomposition of carbonates in the raw materials accounts for about 60%.

[0007] Carbon capture and storage technology is currently the most feasible new technology for reducing carbon dioxide emissions in the cement industry. Among these technologies, oxyfuel combustion technology has the best development prospects. Compared with air combustion, oxyfuel combustion has the following advantages:

[0008] 1) Compared with air combustion, about 79% of the nitrogen in the air no longer participates in combustion during the oxyfuel combustion process, which can increase the flame temperature;

[0009] 2) The nitrogen content in the flue gas is low, and the combustion products are triatomic products. The heat transfer effect of triatomic substances is higher than that of diatomic substances, which improves the heating efficiency;

[0010] 3) Nitrogen no longer participates in smoke exhaust, which can significantly reduce the amount of smoke and reduce heat loss from exhaust.

[0011] At present, full oxygen combustion technology is widely used in float glass and glass fiber kilns, and its application in the cement industry is still in the research and development stage. The cement industry mainly uses full oxygen combustion technology in decomposition furnaces and rotary kilns.

[0012] In high-oxygen-concentration oxy-combustion cement kilns, oxygen and recycled flue gas must be introduced into the kiln to replace air as combustion gases. However, how to inject oxygen and recycled flue gas into the kiln is a key technical challenge. In traditional oxy-combustion systems, oxygen and recycled flue gas are typically mixed, then transported through pipelines and injected into the kiln. However, in high-oxygen-concentration oxy-combustion systems, the continued use of a system that mixes oxygen and recycled flue gas before piping the mixture and injecting it into the kiln presents serious safety concerns. Even with bag filters to remove dust from the recycled flue gas, the flue gas still carries a small amount of fine carbonaceous particles. If high-concentration industrial oxygen (approximately 80% to 95% by volume) and recycled flue gas are directly mixed and transported using conventional methods, these small amounts of carbonaceous particles in the recycled flue gas can easily ignite and burn when exposed to pure oxygen. If this mixture ignites in the pipeline, it could result in a major safety incident, endangering not only the equipment but also the safety of operators. Chinese Patent Publication No. CN105650628A proposes a circulating fluidized bed oxygen-enriched combustion device and its air supply method for oxygen-enriched combustion. In this device, oxygen and circulating flue gas are not mixed before entering the furnace. Instead, they are transported separately through separate pipelines and supplied to multiple locations at different heights within the furnace, addressing safety issues during oxygen transportation and mixing. However, this patent's air supply method is specific to circulating fluidized beds and is not applicable to full oxygen combustion in cement kilns.

[0013] In addition, due to the coupling of fuel combustion and raw material decomposition in the cement decomposition furnace, the combustion temperature in the furnace of the decomposition furnace is relatively low, generally 900~1100℃. If the medium and low temperature circulating flue gas (generally below 400℃) from the firing system directly enters the decomposition furnace, the temperature of the combustion zone in the decomposition furnace will inevitably be difficult to maintain above the ignition temperature of the coal powder, which will cause the flame in the decomposition furnace to be unstable or even extinguished. Therefore, it is very necessary to heat up the oxygen and circulating flue gas before introducing them into the cement decomposition furnace. Under oxygen-rich and carbon-rich conditions, due to the significant increase in the theoretical combustion temperature of the fuel, the safety and pollutant emissions of the combustion device also face great challenges. The main problems are: 1) Deflagration, unstable combustion and furnace wall erosion are prone to occur in the combustion device; 2) When the flame temperature rises in the oxygen-rich state, it is easy to cause NO in the combustion process X Increased emissions increase the load on flue gas denitrification in the subsequent waste gas treatment system.

[0014] For cement production lines with an annual output of millions of tons, annual flue gas CO2 emissions can reach 600,000 to 700,000 tons. Given the relatively small CO2 consumption market, the production of full CO2 capture from cement production flue gas is prohibitively high, exceeding market demand. Therefore, developing a reliable, low-cost, and sustainable carbon capture technology for localized oxyfuel combustion flue gas in cement kilns is a more practical and feasible approach to reducing carbon emissions in the cement industry.

[0015] At present, the problems existing in the local oxyfuel combustion carbon enrichment cement burning system are as follows:

[0016] 1) The local oxyfuel combustion carbon enrichment subsystem has poor process compatibility with the main cement production system, and they interfere with each other;

[0017] 2) The mixed transportation method of medium-low temperature circulating flue gas and industrial oxygen causes internal residual carbon particles to ignite and burn, causing pipeline safety problems;

[0018] 3) The coupling of the heat absorption process of raw meal decomposition and the heat release process of combustion, and the direct entry of medium and low temperature circulating flue gas into the decomposition furnace, will make it difficult for the fuel to ignite, the flame unstable, and the combustion process prone to flameout;

[0019] 4) The medium and low temperature circulating flue gas directly enters the decomposition furnace. Due to the small working air volume, the raw material of the decomposition furnace is difficult to be lifted by the wind, which causes the problem of material collapse. Summary of the Invention

[0020] In order to solve the problems existing in the prior art, the present invention provides a cement burning system and method that can achieve local full oxygen combustion carbon enrichment. The system is mainly composed of a cement calcination main system and a full oxygen combustion subsystem. First, in the preheating and predecomposition link at the end of the firing kiln, the main system and the subsystem operate in parallel; in the rotary kiln, the calcined raw materials produced by the main system and the subsystem are fed into the kiln at the same time to produce cement clinker; and the mutual interference between the main system and the subsystem is reduced, such as mutual air leakage, pressure fluctuation interference, etc. Secondly, in the full oxygen combustion subsystem, the raw material decomposition is divided into a primary combustion zone and a secondary combustion zone that operate in series. The pulverized coal is transported through low-temperature circulating flue gas, and the primary combustion zone is not fed with raw material. The medium-temperature circulating flue gas is sent into the preheating furnace from the inlet of the cyclone chamber of the preheating furnace. The medium and low-temperature circulating flue gases are heated to above 900°C in the preheating furnace, so as to achieve a stable pulverized coal flame in the preheating furnace, no erosion of the preheating furnace wall, and low NO X The emission and complete combustion of pulverized coal can solve the problems of difficulty in ignition of fuel, unstable flame and easy flameout during combustion when medium and low temperature circulating flue gas is directly fed into the decomposition furnace, and avoid the safety problem of spontaneous combustion caused by mixed transportation; the secondary combustion zone is operated with material, and the high temperature circulating flue gas is introduced into the secondary combustion zone for raw material decomposition, and the material is supported by the set Venturi throat jet, which solves the problem of high temperature crusting on the furnace wall caused by raw material collapse and local explosion of pulverized coal, and suppresses the NOx of pulverized coal combustion. X Secondly, the oxy-fuel combustion subsystem draws circulating air in stages. Medium-temperature circulating air (150-400°C) is drawn from between the high-temperature blower and the cooler and fed directly into the preheating furnace. Low-temperature circulating air (less than 150°C) is drawn from after the dust collector and used as pulverized coal conveying air. This ensures safe pulverized coal transportation while improving heat recovery, reducing energy consumption, and achieving carbon enrichment.

[0021] The present invention is achieved by providing a cement burning system capable of achieving localized oxyfuel combustion carbon enrichment, comprising a cement calcining main system and an oxyfuel combustion subsystem, wherein the oxyfuel combustion subsystem comprises a sub-preheater unit, a self-enrichment furnace, a flue gas preheating unit, a venturi throat, a sub-high-temperature fan, a cooler, a sub-dust collector, a medium-temperature circulating fan, a medium-temperature circulating flue gas supply pipeline, a low-temperature circulating fan, a low-temperature circulating flue gas supply pipeline, a fuel supply pipeline, and an industrial oxygen supply pipeline;

[0022] The penultimate sub-cyclone discharge pipe of the sub-preheater unit is connected to the raw meal feeding pipe of the self-enrichment furnace, the last sub-cyclone discharge pipe of the sub-preheater unit is connected to the kiln tail smoke chamber of the cement calcination main system, and the sub-high-temperature fan, cooler and sub-dust collector are sequentially arranged on the top outlet air duct of the sub-preheater unit; the medium-temperature circulation fan is arranged on the medium-temperature circulation flue gas supply pipeline, one end of the medium-temperature circulation flue gas supply pipeline is connected to the pipeline between the sub-high-temperature fan and the cooler, and the other end is connected to the flue gas preheating unit; the low-temperature circulation fan is arranged on the low-temperature circulation flue gas supply pipeline, one end of the low-temperature circulation flue gas supply pipeline is connected to the pipeline of the sub-dust collector gas outlet, and the other end is connected to the fuel supply pipeline;

[0023] The flue gas preheating unit is used to preheat the low-temperature circulating flue gas and the medium-temperature circulating flue gas to above 900°C using fuel; the bottom flue gas outlet of the flue gas preheating unit is connected to the bottom inlet of the venturi throat, the top outlet of the venturi throat is connected to the bottom of the column of the self-enrichment furnace, and the top outlet of the self-enrichment furnace is connected to the inlet of the final sub-cyclone;

[0024] The fuel supply pipeline is connected to the flue gas preheating unit and the coal injection pipe on the upper part of the venturi throat respectively, and the industrial oxygen supply pipeline is connected to the flue gas preheating unit and the oxygen pipe on the lower part of the venturi throat respectively.

[0025] Preferably, the flue gas preheating unit includes a burner and a preheating furnace, wherein the burner is mounted on the top of the preheating furnace, with the head of the burner extending into the preheating furnace. The burner includes an oil pipe, an inner primary air pipe, a coal pipe, and an outer primary air pipe coaxially arranged from the inside to the outside, so that a central oil gun channel, an inner primary air channel, a pulverized coal channel, and an outer primary air channel are formed in sequence from the inside to the outside of the burner; the tail ends of the inner primary air pipe and the outer primary air pipe are both connected to the industrial oxygen supply pipeline, and the tail end of the coal pipe is connected to the fuel supply pipeline;

[0026] The head ports of the oil pipe, coal pipe, and outer primary air pipe are aligned to form the head of the burner; a distance H0 is left between the head of the inner primary air pipe and the head of the burner, so that the inner primary air channel and the pulverized coal channel form an air-coal premixing channel at the head of the burner; an air-coal premixing adjustment ring that can move forward and backward along the axial direction of the burner is provided between the inner primary air channel and the pulverized coal channel, so that the length of the air-coal premixing channel can be adjusted between 0 and H0;

[0027] The preheating furnace is composed of a cyclone chamber, a reducing section and a furnace from top to bottom. The cyclone chamber is a volute structure, so that the flue gas entering the cyclone chamber inlet enters in a volute tangential cyclone.

[0028] A fuel-rich zone located in the center of the furnace, an oxygen-rich zone located outside the fuel-rich zone, and a carbon-rich zone located between the oxygen-rich zone and the furnace wall are formed in the preheating furnace.

[0029] Further preferably, the air-coal premixing adjustment ring is arranged on the inner wall of the inner primary air duct.

[0030] Further preferably, cyclones are provided at the inlet of the inner primary air channel and the outlet of the outer primary air channel.

[0031] Further preferably, a refractory material layer is provided outside the external primary air channel.

[0032] Further preferably, flow controllers are respectively provided on the industrial oxygen supply pipelines connected to the inner primary air duct, the outer primary air duct, and the oxygen pipe at the lower part of the Venturi throat.

[0033] Further preferably, a burner mounting hole is provided at the center of the top cover of the swirl chamber, and the head of the burner extends into the swirl chamber through the burner mounting hole.

[0034] Further preferably, the inner diameter of the diameter-varying section gradually increases from top to bottom.

[0035] Preferably, a medium-temperature circulating air valve is provided on the medium-temperature circulating flue gas supply pipeline at the inlet of the medium-temperature circulating fan, and a low-temperature circulating air valve is provided on the low-temperature circulating flue gas supply pipeline at the inlet of the low-temperature circulating fan.

[0036] Preferably, the Venturi throat is divided into a lower contraction section, a throat high-speed section and an upper expansion section from bottom to top, the lower contraction section is inserted with the oxygen pipe, and the oxygen pipe is inserted downwardly at an angle close to the axial center of the Venturi throat, and the angle between the oxygen pipe and the horizontal direction is 30~60°, so that the industrial oxygen and the circulating flue gas are evenly mixed; the upper expansion section is inserted with the coal injection pipe, and the coal injection pipe is inserted close to the inner wall of the upper expansion section, so that the circulating flue gas and coal powder are mixed in the vortex low-pressure area formed outside the upper expansion section; the number of the oxygen pipe and the coal injection pipe are 2~4 respectively, and they are arranged symmetrically along the circumference.

[0037] Preferably, the raw meal feeding pipe is arranged at the bottom of the column of the self-enrichment furnace.

[0038] A cement burning method capable of achieving partial oxy-combustion carbon enrichment, wherein the cement burning method employs a cement calcination main system and an oxy-combustion subsystem operating in parallel. During the preheating and pre-decomposition phase, the raw meal flow paths are parallel and non-intersecting. During the clinker calcination phase, the two streams of raw meal decomposed by the cement calcination main system and the oxy-combustion subsystem are fed together into a rotary kiln for calcination to produce cement clinker.

[0039] In the oxyfuel combustion subsystem, the raw meal is fed into the sub-preheater unit, preheated in the sub-preheater unit, and then fed into the enrichment furnace for pre-decomposition, and then enters the rotary kiln for calcination; the flue gas from the enrichment furnace passes through the sub-preheater unit under the ventilation of the sub-high-temperature fan for heat exchange, and part of the flue gas returns to the preheating furnace as medium-temperature circulating flue gas; the remaining flue gas is cooled and dust-collected, and part of it is used as low-temperature circulating flue gas;

[0040] In the oxyfuel combustion subsystem, two oxyfuel combustions are carried out in series to carry out pulverized coal combustion and raw meal decomposition. The specific steps are as follows:

[0041] Step 1: Take low-temperature circulating flue gas from the pipeline at the gas outlet of the sub-dust collector. The low-temperature circulating flue gas carries pulverized coal into the flue gas preheating unit. Take medium-temperature circulating flue gas from the pipeline between the sub-high-temperature fan and the cooler and send it to the flue gas preheating unit. Industrial oxygen is introduced into the flue gas preheating unit. The heat from the pulverized coal combustion raises the temperature of the medium- and low-temperature circulating flue gases to above 900°C, and the CO2 concentration in the flue gas is greater than 60%.

[0042] Step 2: The high-temperature circulating flue gas above 900°C exiting the flue gas preheating unit moves upward in the reverse direction;

[0043] Step 3: The high-temperature circulating flue gas enters the Venturi throat, and industrial oxygen is sprayed into the inlet of the Venturi throat to increase the oxygen concentration in the central area to above 30%. Pulverized coal is sprayed into the outlet of the Venturi throat, and the outlet gas forms a jet. Under the action of the jet, a vortex low-pressure area is formed on the outer side of the upper part of the Venturi throat;

[0044] Step 4: The pulverized coal enters the self-enrichment furnace along with the circulating flue gas to burn and release heat. Raw meal is fed into the raw meal feeding pipe of the self-enrichment furnace, so that the raw meal is decomposed in the self-enrichment furnace and CO2 is released. The dry basis CO2 concentration of the flue gas from the enrichment furnace reaches more than 80%, and the temperature is 850~1000℃.

[0045] Preferably, in step 1, the specific process of preheating the medium and low temperature circulating flue gas by the flue gas preheating unit is as follows:

[0046] Low-temperature circulating flue gas is taken from the pipeline at the gas outlet of the sub-dust collector, and the low-temperature circulating flue gas carries the pulverized coal into the pulverized coal channel of the burner; industrial oxygen is divided into two streams and enters the inner primary air channel and the outer primary air channel of the burner respectively. The industrial oxygen in the inner primary air channel enters in a swirl flow, and the industrial oxygen in the outer primary air channel is ejected in a swirl flow. The amount of industrial oxygen supplied meets the oxygen amount required for the combustion of the pulverized coal in the preheating furnace, so that the pulverized coal burns stably in the preheating furnace after being ejected;

[0047] Medium-temperature circulating flue gas is taken from the pipeline between the sub-high-temperature fan and the cooler, and introduced into the swirl chamber of the preheating furnace in a tangential swirl flow, and moves downward along the wall under the centrifugal force of the top swirl chamber; after being ejected from the burner, the pulverized coal and industrial oxygen ignite and burn in the preheating furnace, so that the space in the preheating furnace forms a fuel-rich zone located in the center of the furnace, an oxygen-rich zone located outside the fuel-rich zone, and a carbon-rich zone located between the oxygen-rich zone and the furnace wall; the heat from the pulverized coal combustion raises the temperature of the medium and low-temperature circulating flue gases to above 900℃.

[0048] Further preferably, the coal powder fineness is controlled to have an 80um sieve residue of less than 20%; the oxygen concentration of the industrial oxygen is not less than 80%; the temperature of the low-temperature circulating flue gas is lower than 150°C, the CO2 concentration is higher than 60%, and the O2 concentration is lower than 10%; the temperature of the medium-temperature circulating flue gas is lower than 400°C, the CO2 concentration is higher than 60%, and the O2 concentration is lower than 10%.

[0049] Further preferably, according to the combustion characteristics of the coal powder, the length of the air-coal premixing channel is adjusted by adjusting the air-coal premixing adjustment ring, and / or the amount of industrial oxygen entering the inner primary air channel and the outer primary air channel is adjusted to enhance the ignition and flame stability of the coal powder, so that the coal powder burns stably in the preheating furnace after being sprayed out.

[0050] Preferably, in step three, the average cross-sectional wind speed of the high-speed section in the throat area of ​​the Venturi throat is 25~50m / s, the average cross-sectional wind speed of the outlet of the upper expansion section is 5~15m / s, and the wind speed of the high-speed section in the throat area is more than twice the wind speed at the outlet of the upper expansion section.

[0051] The advantages and positive effects of the present invention are:

[0052] 1. The present invention adopts parallel operation of the main system and subsystem in the preheating and predecomposition link at the end of the firing kiln. In the clinker calcination link, the calcined raw materials produced by the main system and the subsystem are simultaneously fed into the rotary kiln to produce cement clinker, thereby reducing the mutual interference between the main system and the subsystem. The oxyfuel combustion subsystem adopts graded circulating air. The medium-temperature circulating air (150-400°C) is taken from between the sub-high-temperature blower and the cooler and directly fed into the preheating furnace. The low-temperature circulating air (below 150°C) is taken from after the sub-dust collector and used as coal powder conveying air. While ensuring the safety of coal powder transportation, it improves heat recovery, reduces energy consumption, and achieves carbon enrichment.

[0053] 2. In the oxyfuel combustion subsystem of the present invention, the raw meal pre-decomposition is divided into a primary combustion zone and a secondary combustion zone which are operated in series. In the primary combustion zone where the burner and the preheating furnace are located, no raw meal is fed into the primary combustion zone. The pulverized coal is transported by low-temperature circulating flue gas. Industrial oxygen is divided into two streams and supplied to the inside and outside of the pulverized coal channel. The medium-temperature circulating flue gas is supplied to the wall of the cyclone chamber of the preheating furnace, so as to achieve stable pulverized coal flame in the preheating furnace, no ablation of the preheating furnace wall, and low NO XIn order to ensure the complete combustion of pulverized coal and the emission of raw materials, the medium and low temperature circulating flue gas is heated to above 900℃ in the preheating furnace; in the secondary combustion zone where the venturi throat and the self-enrichment furnace are located, the secondary combustion zone is operated with the material, and the high temperature circulating flue gas is introduced into the bottom of the secondary combustion zone, and industrial oxygen and pulverized coal are sprayed in to decompose the raw material. The jet is formed by the set venturi throat to support the material, which solves the problem of high temperature crusting on the furnace wall caused by raw material collapse and local explosion of pulverized coal, and suppresses the NOx emission from pulverized coal combustion. X Release, so that the flue gas temperature from the enrichment furnace is 850~1000℃, and the dry basis CO2 concentration is above 80%, so that the raw material is fully decomposed.

[0054] 3. In the burner provided by the present invention, industrial oxygen does not come into contact with pulverized coal or circulating flue gas during the transportation process, and the coal supply air for pulverized coal transportation adopts low-temperature circulating flue gas with a temperature of less than 150°C, thereby avoiding spontaneous combustion of unburned carbon particles in the circulating flue gas and solving the safety problem of spontaneous combustion caused by mixed transportation of industrial oxygen and pulverized coal in the full oxygen combustion subsystem.

[0055] 4. The burner provided by the present invention adds an air-coal premixing adjustment ring between the inner primary air channel and the coal powder channel, which can move back and forth along the axial direction of the burner. The length of the air-coal premixing channel can be flexibly adjusted, so that according to the combustion characteristics of the coal powder, it is possible to adjust whether industrial oxygen and coal powder are premixed in the burner, thereby avoiding the problem of flame instability or even flameout, and enhancing the ignition and flame stability of the coal; or avoiding the problem of the flame burning speed being too fast and the flame backfired to the premixing zone to burn the burner head, thereby preventing the coal powder from deflagration and backfire, and enhancing the ignition and flame stability of the coal powder without backfire.

[0056] 5. The burner provided by the present invention can also adjust the amount of industrial oxygen entering the inner primary air channel and the outer primary air channel according to the combustion characteristics of the coal powder, thereby preventing the coal powder from deflagration and backfire, and enhancing the ignition and flame stability of the coal powder; and the outer primary air is a high-speed swirling wind, which further enhances the flame stability.

[0057] 6. In the preheating furnace provided by the present invention, the medium-temperature circulating flue gas (150~400℃) enters from the cyclone chamber at the top of the preheating furnace, rotates and flows downward along the wall in the cyclone chamber. Since the temperature of the medium-temperature circulating flue gas is relatively low and the oxygen content is low, a low-temperature protective gas film is formed between the furnace wall and the flame, which effectively protects the refractory material on the preheating furnace wall and prevents it from being burned by the flame.

[0058] 7. In the Venturi throat provided by the present invention, the pulverized coal is located in the upper expansion area of ​​the Venturi throat, and industrial oxygen is introduced into the lower contraction area of ​​the Venturi throat. The industrial oxygen and the circulating flue gas are evenly mixed through the Venturi throat before coming into contact with the pulverized coal, thereby preventing the pulverized coal from deflagration due to the high local oxygen concentration in the self-enrichment furnace, which leads to crusting on the wall surface of the self-enrichment furnace; the gas at the outlet of the Venturi throat forms a jet, so that under the action of the jet, a vortex low-pressure area is formed on the outside of the upper expansion section, and the circulating flue gas and pulverized coal are back-mixed in this area. The oxygen concentration of the circulating flue gas on the outside is relatively low, which suppresses the NOx generated by the combustion of pulverized coal. X release. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the technical solutions of the specific embodiments of the present invention, the following is a brief introduction to the drawings required for use in the description of the specific embodiments. Obviously, the drawings described below are some specific embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0060] Figure 1 This is a process flow chart of a cement burning system capable of achieving partial oxy-combustion carbon enrichment provided by an embodiment of the present invention;

[0061] Figure 2 Schematic diagram of the structure of the flue gas preheating unit provided by an embodiment of the present invention;

[0062] Figure 3 1 is a schematic structural diagram of a preheating furnace provided in an embodiment of the present invention;

[0063] Figure 4 Schematic diagram of the structure of the cyclone chamber provided by an embodiment of the present invention;

[0064] Figure 5 This is a schematic diagram of the structure of the burner provided by the embodiment of the present invention. Figure 1 ;

[0065] Figure 6 yes Figure 5 Structural schematic diagram of the AA section;

[0066] Figure 7 This is a schematic diagram of the structure of the burner provided by the embodiment of the present invention. Figure 2 ;

[0067] Figure 8 yes Figure 7 Schematic diagram of the structure of the BB section;

[0068] Figure 9 Schematic diagram of the structure of the Venturi throat provided by an embodiment of the present invention;

[0069] Figure 101 is a top view of the Venturi throat provided in an embodiment of the present invention.

[0070] Where: g1-industrial oxygen; g2-medium temperature circulating flue gas; g3-low temperature circulating flue gas; F-coal powder; A-fuel-rich zone; B-oxygen-rich zone; C-carbon-rich zone; H-length of air-coal premixing zone; M-raw meal; K-cement clinker;

[0071] 1-Cement calcining main system; 101-First-stage main cyclone; 102-Second-stage main cyclone; 103-Third-stage main cyclone; 104-Fourth-stage main cyclone; 105-Fifth-stage main cyclone; 106-Main calciner; 107-Kiln tail smoke chamber; 108-Rotary kiln; 109-Cooler; 110-Kiln head burner; 111-Tertiary air duct; 112-Main high-temperature fan; 113-Main dust collector; 114-Main exhaust fan; 115-Chimney;

[0072] 2-Full oxygen combustion subsystem;

[0073] 201- first-stage sub-cyclone; 202- second-stage sub-cyclone; 203- third-stage sub-cyclone; 204- fourth-stage sub-cyclone; 205- fifth-stage sub-cyclone;

[0074] 206-self-enrichment furnace; 2061-raw meal feeding pipe;

[0075] 207-Venturi throat; 2071-lower contraction section; 2072-high-speed throat section; 2073-upper expansion section; 2074-oxygen pipe; 2075-coal injection pipe;

[0076] 208-preheating furnace; 2081-cyclone chamber; 2082-reducing section; 2083-furnace; 20811-cyclone chamber inlet; 20812-cyclone chamber top cover; 20813-burner mounting hole;

[0077] 209-burner; 2091-central oil gun channel; 2092-inner primary air cyclone; 2093-inner primary air channel; 2094-pulverized coal channel; 2095-outer primary air channel; 2096-outer primary air cyclone; 2097-air-coal premixing channel; 2098-air-coal premixing regulating ring; 2099-refractory layer;

[0078] 210-sub-high-temperature fan; 211-medium-temperature circulating fan; 212-medium-temperature circulating air valve; 213-cooler; 214-sub-dust collector; 215-sub-exhaust fan; 216-low-temperature circulating fan; 217-low-temperature circulating air valve; 218-coal powder silo; 219-internal primary air flow controller; 220-external primary air flow controller; 221-secondary air flow controller. DETAILED DESCRIPTION

[0079] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0080] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0081] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0082] Example

[0083] See also Figures 1 to 10 This embodiment provides a cement burning system that can achieve local full oxygen combustion carbon enrichment, which consists of a cement calcination main system 1 and a full oxygen combustion subsystem 2. The preheater units of the two systems can adopt two to seven-stage preheaters. This embodiment takes a five-stage preheater as an example for explanation.

[0084] The cement calcining main system 1 comprises a main preheater unit, a main decomposition furnace 106, a kiln tail smoke chamber 107, a rotary kiln 108, a cooler 109, a kiln head burner 110, a tertiary air duct 111, a main high-temperature fan 112, a main dust collector 113, a main exhaust fan 114, and a chimney 115. The main preheater unit is a five-stage cyclone preheater. The raw material entering the cement calcining main system 1 is fed through a pipeline into the outlet duct of the second-stage main cyclone 102 for gas-solid heat exchange. Driven by the airflow, the raw material enters the first-stage main cyclone 101. After gas-solid separation in the first-stage main cyclone 101, the material is fed from the discharge pipe of the first-stage main cyclone 101 into the outlet duct of the third-stage main cyclone 103. In this manner, the raw material enters the second-stage main cyclone 102, the third-stage main cyclone 103, and the fourth-stage main cyclone 104 in sequence. The raw meal after gas-solid separation in the fourth-stage main cyclone 104 enters the main calciner 106, where the raw meal decomposition is completed (calcium carbonate in the raw meal is decomposed into calcium oxide). The decomposed raw meal enters the fifth-stage main cyclone 105 with the air flow, and after gas-solid separation, the raw meal is fed into the kiln tail smoke chamber 107.

[0085] The oxyfuel combustion subsystem 2 is composed of a sub-preheater unit, a self-enrichment furnace 206, a flue gas preheating unit, a venturi throat 207, a sub-high-temperature fan 210, a cooler 213, a sub-dust collector 214, a medium-temperature circulating fan 211, a medium-temperature circulating flue gas supply pipeline, a low-temperature circulating fan 216, a low-temperature circulating flue gas supply pipeline, a fuel supply pipeline and an industrial oxygen supply pipeline. The sub-preheater unit is also a five-stage cyclone preheater. The discharge pipe of the fourth-stage sub-cyclone 204 of the sub-preheater unit is connected to the raw material feeding pipe 2061 of the self-enrichment furnace 206, the top outlet of the self-enrichment furnace 206 is connected to the inlet of the fifth-stage sub-cyclone 205, and the discharge pipe of the fifth-stage sub-cyclone 205 of the sub-preheater unit is connected to the kiln tail smoke chamber 107 of the cement calcination main system 1. The raw meal entering the oxy-fuel combustion subsystem 2 is fed through a pipeline into the outlet duct of the second-stage sub-cyclone 202 for gas-solid heat exchange. Driven by the airflow, it then enters the first-stage sub-cyclone 201. After undergoing gas-solid separation in the first-stage sub-cyclone 201, the raw meal is fed from the discharge pipe of the first-stage sub-cyclone 201 into the outlet duct of the third-stage sub-cyclone 203. In this manner, it sequentially enters the second-stage sub-cyclone 202, the third-stage sub-cyclone 203, and the fourth-stage sub-cyclone 204. After gas-solid separation in the fourth-stage sub-cyclone 204, the raw meal enters the self-enrichment furnace 206, where it is decomposed. The decomposed raw meal then enters the fifth-stage sub-cyclone 205 with the airflow. After gas-solid separation, the raw meal is fed into the kiln tail smoke chamber 107.

[0086] The raw meal of the cement calcining main system 1 and the raw meal of the oxyfuel combustion subsystem 2 enter the kiln tail smoke chamber 107 together, and are calcined into cement clinker in the rotary kiln 108. The high-temperature clinker is cooled in the cooler 109 and discharged from the cement burning system.

[0087] The sub-high-temperature fan 210, cooler 213, sub-dust collector 214 and sub-exhaust fan 215 are sequentially arranged on the top outlet air duct of the sub-preheater unit; the medium-temperature circulation fan 211 is arranged on the medium-temperature circulation flue gas supply pipeline, one end of the medium-temperature circulation flue gas supply pipeline is connected to the pipeline between the sub-high-temperature fan 210 and the cooler 213, and the other end is connected to the flue gas preheating unit, and a medium-temperature circulation air valve 212 is arranged on the medium-temperature circulation flue gas supply pipeline at the inlet of the medium-temperature circulation fan 211; the low-temperature circulation fan 216 is arranged on the low-temperature circulation flue gas supply pipeline, and one end of the low-temperature circulation flue gas supply pipeline is connected to the sub-collector The flue gas preheating unit is connected to the flue gas preheating unit 201 through the flue gas inlet. The flue gas preheating unit 201 through the flue gas inlet is connected to the flue gas preheating unit 201 through the flue gas inlet. The flue gas preheating unit 201 through the flue gas inlet is connected to the flue gas preheating unit 201 through the flue gas inlet. The flue gas preheating unit 201 through the flue gas inlet is connected to the flue gas preheating unit 201 through the flue gas inlet. The flue gas preheating unit 201 through the flue gas inlet is connected to the flue gas preheating unit 201 through the flue gas inlet. The flue gas preheating unit 201 through the flue gas inlet is connected to the flue gas preheating unit 201 through the flue gas inlet. The flue gas preheating unit 201 through the flue gas inlet is connected to the flue gas preheating unit 201 through the flue gas inlet. The flue gas preheating unit 201 through the flue gas inlet is connected to the flue gas preheating unit 201 through the flue gas inlet.

[0088] The temperature of the low-temperature circulating flue gas g3 is below 150°C, and its primary component is CO2, with a CO2 concentration (volume fraction) exceeding 60% and an O2 concentration below 10%. The temperature of the medium-temperature circulating flue gas g2 is below 400°C, and its primary component is CO2, with a CO2 concentration exceeding 60% and an O2 concentration below 10%. The fuel used is pulverized coal F, with a controlled fineness of less than 20% on an 80µm sieve. The oxidant used for combustion is industrial oxygen g1, with a concentration of no less than 80%.

[0089] See Figure 2 The flue gas preheating unit is used to preheat the low-temperature circulating flue gas g3 and the medium-temperature circulating flue gas g2 to above 900°C through fuel; the flue gas preheating unit includes a burner 209 and a preheating furnace 208. The burner 209 is installed on the top of the preheating furnace 208, and the head of the burner 209 extends into the preheating furnace 208. The preheating furnace 208 is used to heat the medium-temperature circulating flue gas g2 and the low-temperature circulating flue gas g3.

[0090] Burner 209 is a cylindrical structure. Figure 5The burner 209 comprises an oil pipe, an inner primary air pipe, a coal pipe, and an outer primary air pipe, which are coaxially arranged from inside to outside. Four channels are formed within the burner 209: a central oil gun channel 2091, an inner primary air channel 2093, a pulverized coal channel 2094, and an outer primary air channel 2095. The ends of the oil pipe, coal pipe, and outer primary air pipe are aligned to form the head of the burner 209. A distance H0 is left between the head of the inner primary air pipe and the head of the burner 209, so that the inner primary air channel 2093 and the pulverized coal channel 2094 form an air-coal premixing channel 2097 within the head of the burner 209. An air-coal premixing adjustment ring 2098 is disposed between the inner primary air channel 2093 and the pulverized coal channel 2094, movable forward and backward along the axis of the burner 209. This allows the length of the air-coal premixing channel 2097 to be adjusted between 0 and H0. In this embodiment, the air-coal premixing adjustment ring 2098 is disposed on the inner wall of the inner primary air pipe.

[0091] See Figure 3 and Figure 4 The preheating furnace 208 consists of a swirl chamber 2081, a reducing section 2082, and a furnace 2083 from top to bottom. The swirl chamber 2081 is a volute-type structure, so that the flue gas entering from the swirl chamber inlet 20811 enters in a volute-type tangential swirl. A burner mounting hole 20813 is provided in the center of the swirl chamber top cover 20812. The burner 209 is installed on the top of the preheating furnace 208 through the burner mounting hole 20813, and the head of the burner 209 extends into the swirl chamber 2081. A refractory material layer 2099 is provided on the outside of the external primary air channel 2095 of the burner 209 for heat insulation, to prevent the flame in the preheating furnace 208 from radiating heat to the burner 209, causing the internal temperature of the burner 209 to be too high, and to prevent the industrial oxygen g1 from oxidizing the wall steel during transportation in the burner 209. The cross-sectional circumference of the swirl chamber 2081 is smaller than that of the furnace 2083 , and the inner diameter of the reducing section 2082 gradually increases from top to bottom, thereby accelerating the full coverage of the circumferential direction of the furnace wall by the swirl of the circulating flue gas.

[0092] See Figure 1 、 Figure 9 and Figure 10The bottom outlet of the furnace 2083 is connected to the bottom of the venturi throat 207 through a pipeline, and the top of the venturi throat 207 is connected to the bottom of the column of the self-enrichment furnace 206; the raw material feeding pipe 2061 is set at the bottom of the column of the self-enrichment furnace 206. The Venturi throat 207 is divided into a lower contraction section 2071, a throat high-speed section 2072 and an upper expansion section 2073 from bottom to top. The lower contraction section 2071 is inserted into the oxygen pipe 2074, and the oxygen pipe 2074 is inserted downwardly inclined to the axial center of the Venturi throat 207. The angle between the oxygen pipe 2074 and the horizontal direction is 30-60 degrees, so that the industrial oxygen g1 is evenly mixed with the circulating flue gas. The insertion depth of this embodiment is 300-1000 mm; the upper expansion section 2073 is inserted into the coal injection pipe 2075, and the coal injection pipe 2075 is horizontally inserted to the inner wall of the upper expansion section 2073, so that the circulating flue gas and coal powder are mixed in the vortex low-pressure area formed outside the upper expansion section 2073. The insertion depth of this embodiment is 100-500 mm; the number of the oxygen pipe 2074 and the coal injection pipe 2075 are 2-4 respectively, and they are arranged symmetrically along the circumference. In this embodiment, two oxygen pipes 2074 and two coal injection pipes 2075 are provided, and the four pipes are evenly distributed in the circumferential direction.

[0093] In the oxyfuel combustion subsystem 2, the fuel supply pipeline is divided into two routes, connected to the coal pipe and the coal injection pipe 2075 above the venturi throat 207, respectively. The low-temperature circulating flue gas supply pipeline is connected to the fuel supply pipeline; the medium-temperature circulating flue gas supply pipeline is connected to the inlet of the cyclone chamber 2081. The industrial oxygen g1 supply pipeline is divided into three routes, connected to the external primary air duct, the internal primary air duct, and the oxygen pipe 2074 below the venturi throat 207, respectively. Flow controllers are installed on each of the industrial oxygen g1 supply pipelines connected to the external primary air duct, the internal primary air duct, and the oxygen pipe 2074 below the venturi throat 207. Pulverized coal F is introduced into the fuel supply pipeline, industrial oxygen g1 is introduced into the industrial oxygen g1 supply pipeline, low-temperature circulating flue gas g3 is introduced into the low-temperature circulating flue gas supply pipeline, and medium-temperature circulating flue gas g2 is introduced into the medium-temperature circulating flue gas supply pipeline.

[0094] Because the air-coal premixing adjustment ring 2098 can be moved forward and backward along the axis of the burner 209, the length of the air-coal premixing channel 2097 can be adjusted between 0 and H0. Assuming the distance between the head of the air-coal premixing adjustment ring 2098 and the head of the burner 209 is H, when H is greater than 0, the inner primary air (i.e., industrial oxygen g1) in the inner primary air channel 2093 and the coal-feeding air (i.e., low-temperature circulating flue gas g3) in the pulverized coal channel 2094 are premixed into one stream within the air-coal premixing channel 2097 (i.e., the premixing zone), passing through the air-coal premixing channel 2097 and exiting the burner 209. The longer the air-coal premixing channel 2097, the stronger the premixing, and the more uniform the contact between the pulverized coal F and the industrial oxygen g1.

[0095] See Figure 5 and Figure 6 When the fuel is a difficult-to-burn coal (such as anthracite), without the air-coal premixing channel 2097, the pulverized coal and industrial oxygen g1 are ejected independently from two channels of the burner 209. Since the coal-supplying air is low-temperature recycled flue gas g3, this can lead to insufficient oxygen supply during the pulverized coal combustion, causing flame instability or even flameout. By adjusting the air-coal premixing adjustment ring 2098, added between the inner primary air channel 2093 and the pulverized coal channel 2094, the industrial oxygen g1 and pulverized coal F are premixed within the burner 209. This allows the pulverized coal F to come into contact with the industrial oxygen g1 before being ejected, enhancing coal ignition and flame stability. The inner primary air enters the air-coal premixing channel 2097 in a swirling flow, while the pulverized coal channel 2094 is a straight flow. In the air-coal premixing channel 2097, the inner primary air, under the centrifugal force of the swirling flow, collides with the coal-supplying air, enhancing the premixing of the industrial oxygen g1 and pulverized coal F.

[0096] For coal with medium flammability, the length H of the premixing zone can be flexibly adjusted through the air-coal premixing adjustment ring 2098, thereby enhancing the ignition and flame stability of the coal without backfire.

[0097] See Figure 7 and Figure 8 For flammable coal, if the industrial oxygen g1 and pulverized coal F are premixed in advance in the burner 209, there will be a problem of the flame burning too fast, the flame flashing back to the premixing zone, and then burning the head of the burner 209. At this time, the flashback problem can be solved by adjusting the position of the air-coal premixing adjustment ring 2098. That is, the air-coal premixing adjustment ring 2098 is inserted to the depth of the burner 209 outlet so that the premixing zone disappears. The burner 209 outlet has four channels. The industrial oxygen g1 and pulverized coal are not premixed in the burner 209 and are ejected from their respective channels. Since the pulverized coal F and the industrial oxygen g1 are isolated from each other before being ejected, the flame cannot flash back to the burner 209 channel. This state is non-premixed mode combustion, which is suitable for coal that is easy to ignite and can prevent the burner 209 head from burning.

[0098] Furthermore, the flow rate of industrial oxygen in the internal primary air duct 2093 can be adjusted by the internal primary air flow controller 219. When the coal is highly flammable, the flow rate of industrial oxygen in the internal primary air duct 2093 is reduced, reducing the amount of industrial oxygen g1 premixed with the pulverized coal and lowering the oxygen concentration at the internal primary air outlet to prevent pulverized coal deflagration and flashback. When the coal is difficult to ignite, the flow rate of industrial oxygen g1 in the internal primary air duct 2093 is increased to enhance the flame stability of the pulverized coal ignition.

[0099] A cement burning method capable of achieving partial oxy-fuel combustion carbon enrichment, wherein the cement burning method adopts a cement calcination main system 1 and an oxy-fuel combustion subsystem 2 operating in parallel. In the preheating and pre-decomposition stage, the raw meal flow paths are parallel and non-crossing. In the clinker calcination stage, the two streams of raw meal decomposed by the cement calcination main system 1 and the oxy-fuel combustion subsystem 2 are jointly fed into a rotary kiln 108 for calcination to prepare cement clinker.

[0100] Among them, in the full oxygen combustion subsystem 2, the raw material is fed into the sub-preheater unit, and after being preheated by the sub-preheater unit, it is fed into the self-enrichment furnace 206 for pre-decomposition, and then enters the rotary kiln 108 for calcination; the flue gas from the enrichment furnace 206 passes through the sub-preheater unit for heat exchange under the exhaust of the sub-high-temperature fan 210, and part of the flue gas from the sub-preheater unit is returned to the preheating furnace 208 as the medium-temperature circulating flue gas g2, and the remaining flue gas is cooled by the cooler 213 and the dust is collected by the sub-dust collector 214, and a part of it is used as the low-temperature circulating flue gas g3, and the remaining part is the carbon dioxide-rich flue gas discharged from the cement burning system through the sub-exhaust fan 215.

[0101] In the oxyfuel combustion subsystem 2, two oxyfuel combustions are carried out in series to carry out pulverized coal combustion and raw material decomposition. The specific steps are as follows:

[0102] Step 1: Take low-temperature circulating flue gas g3 from the pipeline of the gas outlet of the sub-dust collector 214, and the low-temperature circulating flue gas g3 carries the coal powder F into the coal powder channel 2094 of the burner 209; the industrial oxygen g1 is divided into two streams and enters the inner primary air channel 2093 and the outer primary air channel 2095 of the burner 209 respectively. The industrial oxygen g1 in the inner primary air channel 2093 enters in a swirling flow, and the industrial oxygen g1 in the outer primary air channel 2095 is ejected in a swirling flow. The amount of industrial oxygen g1 supplied meets the oxygen amount required for the combustion of the coal powder in the preheating furnace 208, so that the coal powder can burn stably in the preheating furnace 208 after being ejected.

[0103] Step 2: Take the medium-temperature circulating flue gas g2 from the pipeline between the sub-high-temperature fan 210 and the cooler 213, and introduce the medium-temperature circulating flue gas g2 into the swirl chamber 2081 of the preheating furnace 208 in a tangential swirl flow, and move downward along the wall under the centrifugal force of the top swirl chamber 2081; the coal powder and industrial oxygen g1 are ejected from the burner 209 and ignite and burn in the preheating furnace 208, so that the space in the preheating furnace 208 forms a fuel-rich zone A located in the center of the furnace 2083, an oxygen-rich zone B located outside the fuel-rich zone, and a carbon-rich zone C located between the oxygen-rich zone and the furnace wall; the heat from the coal powder combustion raises the temperature of the medium and low-temperature circulating flue gases to above 900°C.

[0104] Step 3: The high-temperature circulating flue gas above 900° C. exiting the preheating furnace 208 moves upward in the reverse direction.

[0105] Step 4: The high-temperature circulating flue gas enters the Venturi throat 207, and industrial oxygen g1 is sprayed into the lower contraction section 2071 at the inlet of the Venturi throat 207, so that the oxygen concentration in the central area is increased to more than 30%; coal powder is sprayed into the upper expansion section 2073 at the outlet of the Venturi throat 207, and the outlet gas forms a jet, so that a vortex low-pressure area is formed on the outside of the upper expansion section 2073 under the action of the jet.

[0106] Step 5: The pulverized coal enters the self-enrichment furnace 206 along with the circulating flue gas to burn and release heat. Raw meal is fed into the raw meal feeding pipe 2061 at the bottom of the column of the self-enrichment furnace 206, so that the raw meal is completely decomposed in the self-enrichment furnace 206 and CO2 is released. The dry basis CO2 concentration of the flue gas from the enrichment furnace 206 reaches more than 80%, and the temperature is 850~1000℃.

[0107] During the entire cement calcining process, the raw cement meal is divided into two parts. The first part is fed into the main preheater unit of the cement calcining main system 1. After preheating, it enters the main calciner 106 for decomposition and then enters the rotary kiln 108 for calcination. The second part is fed into the sub-preheater unit of the oxyfuel combustion subsystem 2. After preheating, it is fed into the self-enrichment furnace 206 for decomposition and then enters the rotary kiln 108 for calcination. Pulverized coal is divided into three parts. The first part is fed into the rotary kiln 108 through the kiln head burner 110 to calcine the cement clinker. The second part is fed into the main calciner 106 for raw meal decomposition. The third part is further divided into two groups. One group is fed into the flue gas preheating unit of the oxyfuel combustion subsystem 2 for circulating flue gas heating, and the other group is fed into the self-enrichment furnace 206 of the oxyfuel combustion subsystem 2 for raw meal decomposition.

[0108] In the oxyfuel combustion subsystem 2, a central oil gun channel 2091 at the center of the burner 209 is used to ignite the preheating furnace 208. Industrial oxygen g1 is supplied through two channels, an inner primary air channel 2093 and an outer primary air channel 2095. The amount of industrial oxygen g1 supplied meets the oxygen requirements for pulverized coal combustion in the preheating furnace 208. An inner primary air cyclone 2092 is located at the inlet of the inner primary air channel 2093, causing the industrial oxygen g1 entering the channel to swirl downward under the action of the inner primary air cyclone 2092. The outer primary air channel 2095 is located outside the pulverized coal channel 2094, and an outer primary air cyclone 2096 is located at the outlet of the outer primary air channel 2095. This cyclone 2096 causes the industrial oxygen g1 in the outer primary air channel 2095 to be ejected in a high-speed swirling flow, enhancing the stability of the flame in the preheating furnace 208.

[0109] Drawing air from the outlet duct of the sub-high-temperature blower 210, medium-temperature circulating flue gas g2, at a temperature of 150-400°C, enters the cyclone chamber inlet 20811, swirling downward along the walls. Because industrial oxygen g1 is used as the oxidant, the oxygen content is significantly higher than in air, resulting in a relatively high flame temperature, reaching over 1300°C in the high-temperature range. When the flame contacts the sidewalls of the preheating furnace 208, it can easily burn the refractory materials on the furnace wall. However, the medium-temperature circulating flue gas g2 swirls into the preheating furnace 208. Due to its relatively low temperature and oxygen content, it effectively forms a low-temperature protective gas film between the furnace wall and the flame, effectively protecting the refractory materials on the preheating furnace 208 walls from flame erosion.

[0110] Air is taken from behind the sub-dust collector 214, and the low-temperature circulating flue gas g3 below 150°C is used as the air for conveying pulverized coal. The CO2 concentration of the low-temperature circulating flue gas is not less than 60%. The pulverized coal is fed into the pulverized coal channel 2094 of the burner 209 through the low-temperature circulating flue gas g3; the industrial oxygen g1 is divided into two streams and enters the burner 209, one of which swirls into the inner primary air channel 2093 of the burner 209, and the industrial oxygen flow is controlled by the inner primary air flow controller 219, and the other stream enters the outer primary air channel 2095 of the burner 209, and the industrial oxygen flow is controlled by the outer primary air flow controller 220. The amount of industrial oxygen g1 supplied meets the oxygen amount required for the combustion of pulverized coal in the preheating furnace 208, so that the pulverized coal is sprayed out and then The combustion in the preheating furnace 208 is stable; the medium-temperature circulating flue gas g2 enters the swirl chamber inlet 20811 of the preheating furnace 208 in a tangential swirl direction, and moves downward along the wall under the centrifugal force of the top swirl chamber 2081; the space in the preheating furnace 208 forms a fuel-rich zone A located in the center of the furnace 2083, an oxygen-rich zone B located outside the fuel-rich zone, and a carbon-rich zone C located between the oxygen-rich zone and the furnace wall; coal powder F and industrial oxygen g1 (oxygen concentration is not less than 80%) are ejected from the burner 209 and ignite and burn in the preheating furnace 208. This is a one-time combustion. By adjusting the coal feeding amount, the heat of the coal powder combustion causes the flue gas from the preheating furnace 208 to flow out from the bottom of the preheating furnace 208 with a temperature above 900°C and a CO2 concentration greater than 60%. The advantages of this air supply method are: 1) the pulverized coal F and the industrial oxygen g1 are not mixed during the transportation process, and the low-temperature circulating flue gas g3 is used to transport the pulverized coal, which solves the safety problem of spontaneous combustion caused by the mixed transportation of industrial oxygen g1 and pulverized coal F in the full oxygen combustion subsystem 2; 2) the medium-temperature circulating flue gas g2 directly enters the preheating furnace 208 and moves downward along the wall, playing the role of a protective air film between the pulverized coal combustion flame and the wall surface, which can prevent the high-temperature flame from burning the wall surface.

[0111] The flue gas preheating unit provided by the present invention uses a ventilation system in which low-temperature circulating flue gas g3 is used as the coal supply air to transport pulverized coal; medium-temperature circulating flue gas g2 is supplied from the cyclone chamber 2081 of the preheating furnace 208, along the wall. Two streams of industrial oxygen g1 are supplied as internal primary air inside the pulverized coal channel 2094, and are premixed with the pulverized coal based on the combustion characteristics of the pulverized coal before being ejected as external primary air in a high-speed swirl outside the pulverized coal channel 2094. This allows the creation of three zones within the preheating furnace 208: a fuel-rich zone A located at the center of the furnace 2083; an oxygen-rich zone B located outside the fuel-rich zone; and a carbon-rich zone C located between the fuel-rich zone and the furnace wall. The advantages of this zoned combustion method are: 1. The excess oxygen coefficient in the fuel-rich zone is less than 1, creating a reducing atmosphere that suppresses NOx generation; and 2. The carbon-rich zone, primarily composed of CO2, has a relatively low gas temperature, which protects the furnace wall and prevents flames from burning it.

[0112] After passing through the pipeline, the high-temperature circulating flue gas from the preheating furnace 208 changes its direction and moves vertically upward, entering the Venturi throat 207. Industrial oxygen g1 is injected into the lower contraction section 2071 at the inlet of the Venturi throat 207, raising the oxygen concentration in the central area to over 30%. The average wind speed in the cross-section of the high-speed section 2072 of the throat is 25-50 m / s, and the average wind speed in the cross-section at the outlet of the upper expansion section 2073 is 5-15 m / s. The wind speed in the high-speed section 2072 of the throat is more than twice the wind speed at the outlet of the upper expansion section 2073. The high-temperature circulating flue gas continues to move upward, forming a jet at the outlet of the Venturi throat 207. Pulverized coal is injected into the upper expansion section 2073 through the coal injection pipe 2075. Under the action of the jet, a vortex low-pressure area is formed on the outside of the upper expansion section 2073. The circulating flue gas and pulverized coal are back-mixed in this area. The oxygen concentration of the circulating flue gas outside is relatively low, which suppresses the NOx emission from the pulverized coal combustion. X release.

[0113] Pulverized coal injected from the coal injection pipe 2075 moves upward with the circulating flue gas and burns in the self-enrichment furnace 206, forming a secondary combustion process. Raw meal is fed from the bottom of the column of the self-enrichment furnace 206, with the raw meal feeding pipe 2061 located above the coal injection pipe 2075. This allows for thorough decomposition of the raw meal within the self-enrichment furnace 206, releasing CO2. The flue gas exiting the enrichment furnace 206 has a temperature of 850-1000°C and a dry-weight CO2 concentration exceeding 80%.

[0114] The flue gas from the enrichment furnace 206 is exhausted by the sub-high-temperature fan 210 and passes through the sub-preheater unit for heat exchange. Part of the flue gas returns to the preheating furnace 208 as the medium-temperature circulating flue gas g2; the remaining flue gas is cooled and dust-collected by the cooler 213, and part of it is used as the low-temperature circulating flue gas g3, and the rest is discharged from the cement burning system as carbon dioxide-rich flue gas.

[0115] In summary, the present invention firstly operates the main system and subsystem in parallel in the preheating and predecomposition link at the end of the firing kiln; in the rotary kiln 108, the calcined raw materials produced by the main system and the subsystem are fed into the kiln at the same time to produce cement clinker; and reduces the mutual interference between the main system and the subsystem, such as mutual air leakage, pressure fluctuation interference, etc. Secondly, in the full oxygen combustion subsystem 2, the raw material decomposition is divided into a primary combustion zone and a secondary combustion zone for series operation, and the pulverized coal F is transported by the low-temperature circulating flue gas g3. The primary combustion zone is not fed with raw materials, and the industrial oxygen g1 is divided into two streams for air supply inside and outside the pulverized coal channel 2094. The medium-temperature circulating flue gas g2 is fed into the preheating furnace 208 from the inlet 20811 of the preheating furnace swirl chamber. In the preheating furnace 208, the medium and low-temperature circulating flue gases are heated to above 900°C, so as to achieve the pulverized coal flame stability, no erosion of the preheating furnace wall, and low NO in the preheating furnace 208. XThe emission and complete combustion of pulverized coal can solve the problems of difficulty in ignition of fuel, unstable flame and easy flameout during the combustion process when the medium and low temperature circulating flue gas is directly fed into the decomposition furnace, and at the same time avoid the safety problem of spontaneous combustion caused by the mixed transportation of industrial oxygen g1 and circulating flue gas; the secondary combustion zone is operated with material, and the high temperature circulating flue gas is introduced into the secondary combustion zone, and industrial oxygen g1 and pulverized coal are sprayed to decompose the raw material, and the material is supported by the jet of the set Venturi throat 207, which solves the problem of high temperature crusting on the furnace wall caused by raw material collapse and local explosion of pulverized coal, and suppresses the NOx of pulverized coal combustion. X Release; the flue gas temperature from the enrichment furnace 206 is brought to 850-1000°C, with a dry basis CO2 concentration exceeding 80%, achieving full decomposition of the raw meal. Furthermore, the oxyfuel combustion subsystem 2 draws circulating air in stages. Intermediate-temperature circulating air (150-400°C) is drawn from between the high-temperature sub-blower 210 and the cooler 213 and fed directly into the preheating furnace 208. Low-temperature circulating air (below 150°C) is drawn from after the dust collector 214 and used as pulverized coal conveying air. This ensures safe pulverized coal transportation while improving heat recovery and reducing energy consumption.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cement burning system capable of achieving partial oxy-combustion carbon enrichment, characterized in that: It consists of a cement calcining main system and an oxyfuel combustion subsystem, wherein the oxyfuel combustion subsystem consists of a sub-preheater unit, a self-enrichment furnace, a flue gas preheating unit, a venturi throat, a sub-high-temperature fan, a cooler, a sub-dust collector, a medium-temperature circulating fan, a medium-temperature circulating flue gas supply pipeline, a low-temperature circulating fan, a low-temperature circulating flue gas supply pipeline, a fuel supply pipeline, and an industrial oxygen supply pipeline; The penultimate sub-cyclone discharge pipe of the sub-preheater unit is connected to the raw meal feeding pipe of the self-enrichment furnace, the last sub-cyclone discharge pipe of the sub-preheater unit is connected to the kiln tail smoke chamber of the cement calcination main system, and the sub-high-temperature fan, cooler and sub-dust collector are sequentially arranged on the top outlet air duct of the sub-preheater unit; the medium-temperature circulation fan is arranged on the medium-temperature circulation flue gas supply pipeline, one end of the medium-temperature circulation flue gas supply pipeline is connected to the pipeline between the sub-high-temperature fan and the cooler, and the other end is connected to the flue gas preheating unit; the low-temperature circulation fan is arranged on the low-temperature circulation flue gas supply pipeline, one end of the low-temperature circulation flue gas supply pipeline is connected to the pipeline of the sub-dust collector gas outlet, and the other end is connected to the fuel supply pipeline; The flue gas preheating unit is used to preheat the low-temperature circulating flue gas and the medium-temperature circulating flue gas to above 900°C using fuel; the bottom flue gas outlet of the flue gas preheating unit is connected to the bottom inlet of the venturi throat, the top outlet of the venturi throat is connected to the bottom of the column of the self-enrichment furnace, and the top outlet of the self-enrichment furnace is connected to the inlet of the final sub-cyclone; The fuel supply pipeline is connected to the flue gas preheating unit and the coal injection pipe at the upper part of the venturi throat, respectively; the industrial oxygen supply pipeline is connected to the flue gas preheating unit and the oxygen pipe at the lower part of the venturi throat, respectively; The flue gas preheating unit includes a burner and a preheating furnace. The burner is installed on the top of the preheating furnace, and the head of the burner extends into the preheating furnace. The burner includes an oil pipe, an inner primary air pipe, a coal pipe, and an outer primary air pipe coaxially arranged from the inside to the outside, so that a central oil gun channel, an inner primary air channel, a pulverized coal channel, and an outer primary air channel are formed in sequence from the inside to the outside of the burner. The tail ends of the inner primary air pipe and the outer primary air pipe are both connected to the industrial oxygen supply pipeline, and the tail end of the coal pipe is connected to the fuel supply pipeline. The preheating furnace is composed of a cyclone chamber, a reducing section and a furnace from top to bottom. The cyclone chamber is a volute structure, so that the flue gas entering the cyclone chamber inlet enters in a volute tangential cyclone. A fuel-rich zone located in the center of the furnace, an oxygen-rich zone located outside the fuel-rich zone, and a carbon-rich zone located between the oxygen-rich zone and the furnace wall are formed in the preheating furnace.

2. The cement burning system capable of achieving partial oxy-combustion carbon enrichment according to claim 1, characterized in that: The head ports of the oil pipe, coal pipe and outer primary air pipe are aligned to form the head of the burner; a distance H0 is left between the head of the inner primary air pipe and the head of the burner, so that the inner primary air channel and the pulverized coal channel form an air-coal premixing channel at the head of the burner; an air-coal premixing adjustment ring that can move back and forth along the axial direction of the burner is provided between the inner primary air channel and the pulverized coal channel, so that the length of the air-coal premixing channel can be adjusted between 0 and H0.

3. The cement burning system capable of achieving partial oxy-combustion carbon enrichment according to claim 2, characterized in that: The air-coal premixing regulating ring is arranged on the inner wall of the inner primary air duct.

4. The cement burning system capable of achieving partial oxy-combustion carbon enrichment according to claim 2, characterized in that: A cyclone is provided at the inlet of the inner primary air channel and the outlet of the outer primary air channel; and a refractory material layer is provided outside the outer primary air channel.

5. The cement burning system capable of achieving partial oxy-combustion carbon enrichment according to claim 2, characterized in that: Flow controllers are respectively provided on the industrial oxygen supply pipelines connected to the inner primary air duct, the outer primary air duct and the oxygen pipe at the lower part of the venturi throat.

6. The cement burning system capable of achieving partial oxy-combustion carbon enrichment according to claim 2, characterized in that: A burner mounting hole is provided at the center of the top cover of the swirl chamber, and the head of the burner extends into the swirl chamber through the burner mounting hole; the inner diameter of the diameter-reducing section gradually increases from top to bottom.

7. The cement burning system capable of achieving partial oxy-combustion carbon enrichment according to claim 1, characterized in that: A medium-temperature circulating air valve is provided on the medium-temperature circulating flue gas supply pipeline at the inlet of the medium-temperature circulating fan, and a low-temperature circulating air valve is provided on the low-temperature circulating flue gas supply pipeline at the inlet of the low-temperature circulating fan.

8. The cement burning system capable of achieving partial oxy-combustion carbon enrichment according to claim 1, characterized in that: The Venturi throat is divided into a lower contraction section, a throat high-speed section and an upper expansion section from bottom to top. The lower contraction section is inserted with the oxygen pipe, and the oxygen pipe is inserted downwardly at an angle close to the axial center of the Venturi throat. The angle between the oxygen pipe and the horizontal direction is 30-60 degrees, so that the industrial oxygen and the circulating flue gas are evenly mixed; the upper expansion section is inserted with the coal injection pipe, and the coal injection pipe is inserted close to the inner wall of the upper expansion section, so that the circulating flue gas and coal powder are mixed in the vortex low-pressure area formed outside the upper expansion section; the number of the oxygen pipe and the coal injection pipe are 2-4 respectively, and they are arranged symmetrically along the circumference.

9. The cement burning system capable of achieving partial oxy-combustion carbon enrichment according to claim 1, characterized in that: The raw material feeding pipe is arranged at the bottom of the column of the self-enrichment furnace.

10. A cement burning method capable of achieving partial oxy-combustion carbon enrichment based on the cement burning system according to any one of claims 1 to 9, characterized in that: The cement burning method adopts a cement calcination main system and an oxyfuel combustion subsystem to operate in parallel. In the preheating and pre-decomposition stage, the raw meal flow paths are parallel and non-crossing. In the clinker calcination stage, the two streams of raw meal decomposed by the cement calcination main system and the oxyfuel combustion subsystem are fed into a rotary kiln for calcination to produce cement clinker. In the oxyfuel combustion subsystem, the raw meal is fed into the sub-preheater unit, preheated in the sub-preheater unit, and then fed into the enrichment furnace for pre-decomposition, and then enters the rotary kiln for calcination; the flue gas from the enrichment furnace passes through the sub-preheater unit under the ventilation of the sub-high-temperature fan for heat exchange, and part of the flue gas returns to the preheating furnace as medium-temperature circulating flue gas; the remaining flue gas is cooled and dust-collected, and part of it is used as low-temperature circulating flue gas; In the oxyfuel combustion subsystem, two oxyfuel combustions are carried out in series to carry out pulverized coal combustion and raw material decomposition. The specific steps are as follows: Step 1: Take low-temperature circulating flue gas from the pipeline at the gas outlet of the sub-dust collector. The low-temperature circulating flue gas carries pulverized coal into the flue gas preheating unit. Take medium-temperature circulating flue gas from the pipeline between the sub-high-temperature fan and the cooler and send it to the flue gas preheating unit. Industrial oxygen is introduced into the flue gas preheating unit. The heat from the pulverized coal combustion raises the temperature of the medium- and low-temperature circulating flue gases to above 900°C, and the CO2 concentration in the flue gas is greater than 60%. Step 2: The high-temperature circulating flue gas above 900°C from the flue gas preheating unit moves upward in the reverse direction; Step 3: The high-temperature circulating flue gas enters the Venturi throat, and industrial oxygen is sprayed into the inlet of the Venturi throat to increase the oxygen concentration in the central area to above 30%. Pulverized coal is sprayed into the outlet of the Venturi throat, and the outlet gas forms a jet. Under the action of the jet, a vortex low-pressure area is formed on the outer side of the upper part of the Venturi throat; Step 4: The pulverized coal enters the self-enrichment furnace along with the circulating flue gas to burn and release heat. Raw meal is fed into the raw meal feeding pipe of the self-enrichment furnace, so that the raw meal is decomposed in the self-enrichment furnace and CO2 is released. The dry basis CO2 concentration of the flue gas from the enrichment furnace reaches more than 80%, and the temperature is 850~1000℃.

11. The cement burning method capable of achieving partial full oxygen combustion carbon enrichment according to claim 10, characterized in that: In step 1, the specific process of preheating the medium and low temperature circulating flue gas by the flue gas preheating unit is as follows: Low-temperature circulating flue gas is taken from the pipeline at the gas outlet of the sub-dust collector, and the low-temperature circulating flue gas carries the pulverized coal into the pulverized coal channel of the burner; industrial oxygen is divided into two streams and enters the inner primary air channel and the outer primary air channel of the burner respectively. The industrial oxygen in the inner primary air channel enters in a swirl flow, and the industrial oxygen in the outer primary air channel is ejected in a swirl flow. The amount of industrial oxygen supplied meets the oxygen amount required for the combustion of the pulverized coal in the preheating furnace, so that the pulverized coal burns stably in the preheating furnace after being ejected; Medium-temperature circulating flue gas is taken from the pipeline between the sub-high-temperature fan and the cooler, and introduced into the swirl chamber of the preheating furnace in a tangential swirl flow, and moves downward along the wall under the centrifugal force of the top swirl chamber; after being ejected from the burner, the pulverized coal and industrial oxygen ignite and burn in the preheating furnace, so that the space in the preheating furnace forms a fuel-rich zone located in the center of the furnace, an oxygen-rich zone located outside the fuel-rich zone, and a carbon-rich zone located between the oxygen-rich zone and the furnace wall; the heat from the pulverized coal combustion raises the temperature of the medium and low-temperature circulating flue gases to above 900℃.

12. The cement burning method capable of achieving partial full oxygen combustion carbon enrichment according to claim 10 or 11, characterized in that: The pulverized coal fineness is controlled to have an 80um sieve residue of less than 20%; the oxygen concentration of the industrial oxygen is not less than 80%; the temperature of the low-temperature circulating flue gas is lower than 150°C, the CO2 concentration is higher than 60%, and the O2 concentration is lower than 10%; the temperature of the medium-temperature circulating flue gas is lower than 400°C, the CO2 concentration is higher than 60%, and the O2 concentration is lower than 10%.

13. The cement burning method capable of achieving partial full oxygen combustion carbon enrichment according to claim 11, characterized in that: According to the combustion characteristics of the pulverized coal, the length of the air-coal premixing channel is adjusted by adjusting the air-coal premixing adjustment ring, and / or the amount of industrial oxygen entering the inner primary air channel and the outer primary air channel is adjusted to enhance the ignition and flame stability of the pulverized coal, so that the pulverized coal burns stably in the preheating furnace after being sprayed out.

14. The cement burning method capable of achieving partial full oxygen combustion carbon enrichment according to claim 10, characterized in that: In step three, the average cross-sectional wind speed of the high-speed section of the throat area of ​​the Venturi throat is 25~50m / s, the average cross-sectional wind speed of the outlet of the upper expansion section is 5~15m / s, and the wind speed of the high-speed section of the throat area is more than twice the wind speed of the outlet of the upper expansion section.

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