Cement kiln system for coupling oxygen enrichment and staged combustion by using alternative fuel in large proportion

Abstract

The invention belongs to the technical field of energy conservation and environmental protection, and discloses a cement kiln system for coupling oxygen enrichment and staged combustion by using alternative fuel in a large proportion, which comprises a circulating fluidized bed system, a decomposing furnace, a rotary kiln and a grate cooler, the kiln tail of the rotary kiln is connected with the bottom of the decomposing furnace, a bottom gasified gas spraying pipe is arranged between a kiln tail smoke chamber of the cement kiln and a coal spraying pipe of the conical part, and an upper gasified gas spraying pipe is arranged on the upper portion of the middle section of the decomposing furnace; the bottom gasified gas spray pipe and the upper gasified gas spray pipe are both connected to a gasified gas outlet of the circulating fluidized bed system; and a semi-gasified gas spray pipe is arranged at the upper part of the lower section of the decomposing furnace and is connected to a semi-gasified gas outlet of the circulating fluidized bed system. The disposal amount of the alternative fuel can replace 50% of pulverized coal in the decomposing furnace, and the requirement for using the alternative fuel in a large proportion is met.

Description

Technical Field

[0001] The invention belongs to the technical field of energy conservation and environmental protection, and in particular relates to a cement kiln system that uses a large proportion of alternative fuels coupled with oxygen-enriched and staged combustion. Background Art

[0002] At present, the proportion of alternative fuels used in my country's cement industry is relatively low, basically maintained at a thermal substitution rate of about 5%. In addition to supply chain factors, the main constraints on system operation are that alternative fuels have a wide range of sources, complex ingredients, low calorific value, and high water content, alkali metal and chlorine content. Large-scale use will cause drastic fluctuations in kiln operating conditions and incomplete combustion of fuels, resulting in reduced clinker production, reduced use of alternative fuels, and excessive carbon monoxide, nitrogen oxides and sulfur dioxide in kiln tail flue gas emissions.

[0003] At present, the main practices and measures of cement kiln systems to deal with problems such as high pollutant emissions, unstable operating conditions, reduced clinker production, and reduced use of alternative fuels are, on the one hand, to adopt a decomposition furnace with a graded combustion technology effect. By creating a reducing atmosphere area with low oxygen concentration and high carbon monoxide concentration in the decomposition furnace, the nitrogen oxides generated by the intense combustion of coal powder in the rotary kiln can be reduced; on the other hand, the use of kiln head oxygen-enriched combustion technology can increase the oxygen concentration of the primary air, further supplement the convective heat transfer mode of coal powder combustion with the radiation heat transfer mode, improve the heat transfer efficiency, reduce unit coal consumption and increase clinker production.

[0004] Although these two technologies can effectively reduce pollutant emissions and increase production per unit, when a large amount of alternative fuels are added to the cement kiln, the incomplete combustion of the alternative fuels will destroy the staged combustion effect, causing the kiln's reducing area to expand and the combustion conditions to fluctuate more. Traditional cement kiln oxygen-enriched combustion is basically used at the kiln head, and its effect on the decomposition furnace is only to increase the tertiary air temperature and tertiary air volume, and it cannot directly play a significant role in improving the combustion conditions of the decomposition furnace that uses a large amount of alternative fuels. Conventional staged combustion and oxygen-enriched combustion technologies are not competent for the current situation of large-scale industrial use of alternative fuels. Summary of the invention

[0005] The purpose of the present invention is to provide a cement kiln system that uses a large proportion of alternative fuels coupled with oxygen-enriched and staged combustion, so as to solve the technical problems in the prior art that when the alternative fuels are added on a large scale, the combustion conditions in the decomposition furnace of the cement kiln system will be significantly deteriorated, and it is difficult to combine with oxygen-enriched combustion and staged combustion technology.

[0006] The cement kiln system that uses a large proportion of alternative fuels coupled with oxygen-enriched and staged combustion includes a circulating fluidized bed system, a decomposition furnace, a rotary kiln and a grate cooler. The circulating fluidized bed system is used to process the alternative fuel to form semi-gasified gas and gasified gas. The kiln tail of the rotary kiln is connected to the bottom of the decomposition furnace. The kiln head of the rotary kiln also transports tertiary air into the decomposition furnace through a tertiary air duct. The decomposition furnace is divided into three sections from top to bottom by a lower constriction and an upper constriction. The bottom of the decomposition furnace is provided with a cone. A bottom gasification gas nozzle is provided between the kiln tail smoke chamber of the cement kiln and the coal injection pipe of the cone, and an upper gasification gas nozzle is provided at the upper middle part of the decomposition furnace. The bottom gasification gas nozzle and the upper gasification gas nozzle are both connected to the gasification gas outlet of the circulating fluidized bed system for injecting gasification gas generated by alternative fuel; a semi-gasification gas nozzle is provided at the upper lower part of the decomposition furnace, and the semi-gasification gas nozzle is connected to the semi-gasification gas outlet of the circulating fluidized bed system for injecting semi-gasification gas generated by alternative fuel.

[0007] Preferably, the conical part of the decomposition furnace is sprayed with gasification gas through the bottom gasification gas nozzle, the middle section of the decomposition furnace is sprayed with gasification gas through the upper gasification gas nozzle, and the position where the semi-gasification gas nozzle sprays semi-gasification gas in the lower section of the decomposition furnace is located between the coal powder oxygen-enriched burner and the lower contraction, and the semi-gasification gas is sprayed in the intense combustion zone of the coke.

[0008] Preferably, the bottom gasification gas nozzle and the semi-gasification gas nozzle are arranged in a tangential circle form, which forms a corresponding gas supply plane in the horizontal direction, and a plurality of nozzles are arranged on the gas supply plane. The jetting direction of the nozzle is the tangent direction of the side wall of the furnace body on the gas supply plane, and the plurality of nozzles are arranged centrally symmetrically with the center of the furnace body of the decomposition furnace as the center; the upper gasification gas nozzle is radially arranged in the decomposition furnace, and there is an inclination angle between the nozzle and the axis of the furnace body in the vertical direction. The height of the material sprayed from the nozzle is higher than the gas supply plane where the nozzle is arranged, and at the same time, the horizontal rotation direction of the material sprayed from the nozzle is consistent with the rotation direction of the airflow in the furnace.

[0009] Preferably, the semi-gasified gas nozzle is a sleeve-type burner, comprising an inner tube portion and an outer tube portion sleeved outside the inner tube portion, the inner sleeve is used to spray out the semi-gasified gas, and the outer sleeve is used to spray out oxygen or oxygen-enriched air.

[0010] Preferably, corresponding oxygen injection pipes are provided at both the upper contraction and the lower contraction, namely the upper oxygen injection pipe and the lower oxygen injection pipe; the tertiary air duct is connected above the cone, and a tertiary air oxygen injection pipe is provided at the connection port between the tertiary air duct and the top of the cone for injecting oxygen into the cone through the connection port.

[0011] Preferably, a first flue gas analysis monitoring device is provided at the upper part of the upper section of the decomposition furnace, and a second flue gas analysis monitoring device is provided below the upper constriction, and both flue gas analysis monitoring devices are used to detect O2, CO and NO x When the CO concentration detected by the second flue gas analysis monitoring device is not less than the threshold value, it means that there is insufficient oxygen in the decomposition furnace. At the same time, the oxygen supply of the lower oxygen injection pipe and the upper oxygen injection pipe is increased to fully burn the unburned combustibles. When any flue gas analysis monitoring device detects NO x When the concentration is not less than the threshold, it indicates that a local high temperature zone appears in the combustion process of the decomposition furnace. At this time, the upper gasification gas nozzle injects gasification gas into this position to reduce NO x When the flue gas analysis and monitoring device 2 detects that the O2 concentration is not less than 5%, the oxygen supply of the lower oxygen injection pipe should also be reduced.

[0012] Preferably, the circulating fluidized bed system comprises a circulating fluidized bed, a primary cyclone separator, a secondary cyclone separator, a semi-gasified gas detection device and a gasified gas detection device, the circulating fluidized bed is provided with an alternative fuel feed inlet, a coal powder feed inlet, an alternative fuel bottom slag discharge channel and an air outlet channel located at the upper portion, the air outlet channel is connected to the primary cyclone separator, the exhaust channel at the upper portion of the primary cyclone separator is connected to the secondary cyclone separator, a semi-gasified gas outlet and a two-stage cyclone separator valve are provided on the exhaust channel, the two-stage cyclone separator valve is located between the semi-gasified gas outlet and the secondary cyclone separator, the semi-gasified gas detection device is provided at the semi-gasified gas outlet, the air outlet at the upper portion of the secondary cyclone separator is a gasified gas outlet and is provided with the gasified gas detection device; the bottom channel of the secondary cyclone separator is connected to the lower portion of the circulating fluidized bed via the bottom channel of the primary cyclone separator.

[0013] Preferably, a tertiary air branch pipe and an air inlet pipe are connected to the bottom of the circulating fluidized bed, the tertiary air branch pipe has a valve and an inlet connected to the tertiary air branch pipe, the air inlet pipe is provided with three air inlet branches, the three air inlet branches are respectively a dechlorination agent supply pipe, a water vapor supply pipe and an oxygen supply pipe, valves are provided on the three air inlet branches, and the oxygen supply pipe is connected to the oxygen blower.

[0014] Preferably, the semi-gasification gas detection equipment is used to detect the calorific value of the combustible gas, the components of the combustible gas, and the particle size of the unburned coke, and the gasification gas detection equipment is used to detect the calorific value of the combustible gas and the components of the combustible gas; the gasification efficiency is the ratio of the output gasification gas heat to the input alternative fuel heat, excluding the output coke heat; the process of supplying gas to the circulating fluidized bed is as follows: under normal circumstances, a part of the high-temperature tertiary air from the tertiary air duct is sent to the bottom of the circulating fluidized bed through the tertiary air branch pipe, and the oxygen-enriched air is supplied to the bottom of the circulating fluidized bed from the air inlet pipe. By adjusting the tertiary air volume and the oxygen-enriched air volume The proportion of air fed into the circulating fluidized bed, from an overall perspective, after the tertiary air and oxygen-enriched air are fully mixed, the oxygen concentration of the supplied gas is basically between 40% and 60%, and the excess air coefficient is between 0.2 and 0.5; when it is monitored that the calorific value of the gasified gas at the outlet of the circulating fluidized bed is lower than the threshold and the gasification efficiency is lower than the threshold, it indicates that the pyrolysis gasification condition of the circulating fluidized bed is not good. In this case, saturated steam in the drum of the cement kiln waste heat boiler is selected as the gasifier and supplied from the bottom of the circulating fluidized bed, thereby increasing the calorific value of the gasifier; when the calorific value of the gasified gas at the outlet is greater than the threshold and the gasification efficiency is higher than the threshold, the water vapor supply is stopped.

[0015] Preferably, the oxygen production device produces 80% oxygen and then passes it through the oxygen mixing device to form oxygen-enriched air with an oxygen concentration of about 35%, which is input into the rotary kiln at the kiln head to replace the kiln head primary air; the oxygen-enriched air is sent to the kiln head burner together with the coal powder to form oxygen-enriched combustion in the rotary kiln.

[0016] The present invention has the following advantages: the amount of alternative fuel disposal achieved by the circulating fluidized bed system can replace 50% of the coal powder in the decomposition furnace, meeting the demand for large-scale use of alternative fuels. Among them, the alternative fuel actually undergoes partial pyrolysis and gasification in an oxygen-rich atmosphere in the furnace, forming a gas-solid mixture product such as gasified gas and fixed carbon that is not completely pyrolyzed and gasified, called semi-gasified gas, and the circulating fluidized bed system will also discharge gasified gas without unburned coke. The cone of the decomposition furnace is sprayed with gasified gas through the bottom gasification gas nozzle, thereby strengthening the reducing property of the reduction zone in the graded combustion of the decomposition furnace, and together with the coal powder, a reduction zone composed of CO, H2, CH4, alkanes, etc. is formed in the cone area, thereby reducing and eliminating the high-concentration nitrogen oxides in the kiln tail smoke chamber. The middle section of the decomposition furnace is sprayed with gasified gas through the upper gasification gas nozzle, which can reduce NO in this area. xThe position where the semi-gasified gas nozzle sprays the semi-gasified gas in the lower section of the decomposition furnace is located between the pulverized coal oxygen-enriched burner and the lower constriction, which is the intense combustion zone of coke. Spraying the semi-gasified gas here can extend and expand the combustion space of the intense combustion zone, preventing the furnace body from overheating and clinker sintering. Since there will be solid coke in the semi-gasified gas, the combustion speed is slower than that of the gasified gas, and the travel in the decomposition furnace will also be lengthened. At the same time, since the coke in the pulverized coal also exists in this area, the intense combustion zone of the decomposition furnace will be further extended and expanded. In this way, the present invention monitors the gas components by means of the flue gas analysis and monitoring device 1 and the flue gas analysis and monitoring device 2, so as to achieve the matching of oxygen supply, gasification gas supply and the staged combustion requirements of the decomposition furnace, deepen the staged combustion effect, and achieve the effect of both reducing pollutants and increasing the disposal amount of alternative fuels. Through the circulating fluidized bed system provided by the present invention, the pyrolysis temperature of the circulating fluidized bed is controlled at 700-800°C. Within this temperature range, the pyrolysis reaction direction can be made to proceed in the direction of gasification, thereby reducing the generation of coke and increasing the generation of pyrolysis gas. At the same time, the high temperature can ensure the gasification speed and increase the processing capacity of alternative fuels. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic flow diagram of a cement kiln system that uses alternative fuels in large proportions coupled with oxygen-enriched and staged combustion according to the present invention.

[0018] Figure 2 for Figure 1 Schematic diagram of the structure of the decomposition furnace in the structure shown.

[0019] Figure 3 for Figure 1 Schematic diagram of the structure of the circulating fluidized bed system in the structure shown.

[0020] Figure 4 for Figure 2 A schematic diagram of the structure in which the semi-gasification gas nozzle and the bottom gasification gas nozzle are arranged in a tangential circle form.

[0021] Figure 5 for Figure 4 Structural schematic diagram of the three-dimensional arrangement of the structure shown.

[0022] In the drawings of the specification, O represents oxygen-enriched gas, g represents gasification gas, gh represents semi-gasification gas, F represents pulverized coal, and AF represents alternative fuel. The drawings include: 1. decomposition furnace, 101. upper constriction, 102. lower constriction, 103. cone, 104. semi-gasification gas nozzle, 105. bottom gasification gas nozzle, 106. upper gasification gas nozzle, 107. upper oxygen injection pipe, 108. lower oxygen injection pipe, 109. pulverized coal oxygen-enriched burner, 110. coal injection pipe, 111. furnace body feed port, 112. flue gas analysis and monitoring device 1, 113. flue gas analysis and monitoring device 2, 2. rotary kiln, 3. circulating flow fluidized bed system, 301, circulating fluidized bed, 302, primary cyclone separator, 303, secondary cyclone separator, 304, coal powder feed port, 305, alternative fuel feed port, 306, alternative fuel bottom slag discharge channel, 307, air outlet channel, 308, exhaust channel, 309, two-stage cyclone separator valve, 310, bottom channel, 311, semi-gasification gas detection equipment, 312, gasification gas detection equipment, 313, air inlet pipe, 314, oxygen fan, 4, tertiary air duct, 401, tertiary air oxygen injection pipe, 402, tertiary air branch pipe, 5, oxygen production device, 6, oxygen mixing device, 7, grate cooler. DETAILED DESCRIPTION

[0023] The specific implementation modes of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0024] like Figures 1 to 5 As shown, the present invention provides a cement kiln system that uses a large proportion of alternative fuels coupled with oxygen-enriched and staged combustion, including a circulating fluidized bed system 3, a decomposition furnace 1, a rotary kiln 2 and a grate cooler 7, wherein the circulating fluidized bed system 3 is used to process the alternative fuel to form semi-gasified gas and gasified gas, the kiln tail of the rotary kiln 2 is connected to the bottom of the decomposition furnace 1, and the kiln head of the rotary kiln 2 also transports tertiary air into the decomposition furnace 1 through a tertiary air duct 4, the decomposition furnace 1 is divided into three sections from top to bottom by a lower constriction 102 and an upper constriction 101, the bottom of the decomposition furnace 1 is provided with a cone 103, and the water A bottom gasification gas nozzle 105 is provided between the kiln tail smoke chamber of the mud kiln and the coal injection pipe 110 of the cone 103, and an upper gasification gas nozzle 106 is provided at the upper middle part of the decomposition furnace 1. The bottom gasification gas nozzle 105 and the upper gasification gas nozzle 106 are both connected to the gasification gas outlet of the circulating fluidized bed system 3 for injecting gasification gas generated by alternative fuel; a semi-gasification gas nozzle 104 is provided at the upper lower part of the decomposition furnace 1, and the semi-gasification gas nozzle 104 is connected to the semi-gasification gas outlet of the circulating fluidized bed system 3 for injecting semi-gasification gas generated by alternative fuel.

[0025] The circulating fluidized bed system 3 pre-treats the alternative fuel. The overall process is to introduce oxygen-enriched air with insufficient oxygen. The alternative fuel actually undergoes partial pyrolysis and gasification in an oxygen-enriched atmosphere in the furnace (the amount of oxygen supplied is lower than the amount of oxygen for complete combustion, but the overall oxygen concentration in the supplied gas is higher than 21% of air). In this way, the alternative fuel cannot be completely gasified into gasified gas in the circulating fluidized bed system 3. Finally, after the circulating fluidized bed system 3 pre-treats the alternative fuel, a gas-solid mixture product such as gasified gas and fixed carbon that is not completely pyrolyzed and gasified is formed, which is called semi-gasified gas, including alkanes, H2, CO, solid semi-coke (particle size ≤ 1mm), residual oxygen, CO2, H2O, etc. The circulating fluidized bed system 3 also discharges gasified gas without unburned coke, including H2, CO, CH4, alkane gas, etc.

[0026] Because of the oxygen-enriched combustion of rotary kiln 2, nitrogen oxides are generated violently in the flue gas in the kiln tail smoke chamber. The nitrogen oxides will increase from the conventional 500mg / Nm 3 -600mg / Nm 3 Up to 1500mg / Nm 3 -2000mg / Nm 3 The cone 103 of the decomposition furnace 1 is injected with gasification gas through the bottom gasification gas nozzle 105, the purpose of which is to strengthen the reducing property of the reduction zone in the staged combustion of the decomposition furnace 1, and form a reduction zone composed of CO, H2, CH4, alkanes, etc. in the cone 103 area together with the coal powder, so as to reduce and eliminate the high concentration of nitrogen oxides in the kiln tail smoke chamber. The middle section of the decomposition furnace 1 is injected with gasification gas through the upper gasification gas nozzle 106, which can reduce NO in this part. x The position where the semi-gasified gas nozzle 104 injects the semi-gasified gas in the lower section of the decomposition furnace 1 is located between the pulverized coal oxygen-enriched burner 109 (the position of the original cylindrical coal injection pipe 110, i.e., the coal injection point) and the lower constriction 102, which is the intense combustion zone of coke. The lower section of the decomposition furnace 1 is also provided with a furnace body feed port 111, where the injection of semi-gasified gas can extend and expand the combustion space of the intense combustion zone, preventing the furnace body from overheating and clinker sintering. Since solid coke will exist in the semi-gasified gas, the combustion speed is slower than that of the gasified gas, and the travel in the decomposition furnace 1 will also be lengthened. At the same time, since the coke in the pulverized coal also exists in this area, the intense combustion zone of the decomposition furnace 1 will be further extended and expanded.

[0027] The bottom gasification gas nozzle 105 and the semi-gasification gas nozzle 104 are arranged in a tangential circle form, which means that a corresponding gas supply plane is formed in the horizontal direction. A plurality of nozzles are arranged on the gas supply plane. The jetting direction of the nozzle is the tangent direction of the furnace body side wall (the horizontal cross section is circular) on the gas supply plane. The plurality of nozzles are arranged symmetrically with the furnace body center of the decomposition furnace 1 as the center. There are a plurality of pairs of upper gasification gas nozzles 106. The middle upper part of the decomposition furnace 1 is called the plurality of pairs of upper gasification gas nozzles 106 arranged axially symmetrically based on the furnace body axis of the decomposition furnace 1 as the axis. The upper gasification gas nozzles 106 are radially arranged in the decomposition furnace 1. There is an inclination angle between the nozzle and the axis of the furnace body in the vertical direction. The height of the material ejected by the nozzle is higher than the gas supply plane where the nozzle is arranged. At the same time, the horizontal rotation direction of the material ejected by the nozzle is consistent with the rotation direction of the airflow in the furnace.

[0028] The semi-gasified gas nozzle 104 is a sleeve-type burner, including an inner tube portion and an outer tube portion sleeved outside the inner tube portion. The inner sleeve is used to spray semi-gasified gas, and the outer sleeve is used to spray oxygen or oxygen-enriched air. In this way, oxygen can be supplied at the same time to intensify the combustion intensity of the corresponding area.

[0029] The upper constriction 101 and the lower constriction 102 are both provided with corresponding oxygen injection pipes, namely, the upper oxygen injection pipe 107 and the lower oxygen injection pipe 108. The tertiary air duct 4 is connected to the top of the cone 103, and the tertiary air injection pipe 401 is provided at the connection port between the tertiary air duct 4 and the top of the cone 103 for injecting oxygen into the cone 103 through the connection port. This scheme realizes multi-position oxygen supply, so that oxygen can be evenly distributed in the large space in the decomposition furnace 1. At the tertiary air duct 4, the oxygen-enriched air with an oxygen concentration of 80% produced in the oxygen production system is directly introduced into the tertiary air duct 4, so that the oxygen concentration of the tertiary air introduced into the decomposition furnace 1 is 25%-30%. Since 40℃-50℃ oxygen is supplied, the tertiary air temperature will be slightly reduced from 1100℃, and the temperature will be reduced to above 1000℃ when entering the decomposition furnace 1. After the overall oxygen concentration is increased, the combustion atmosphere in the intense combustion zone of the staged combustion of the decomposition furnace 1 presents an oxygen-enriched combustion state.

[0030] The cone 103 is supplemented with oxygen when receiving the tertiary wind. Under the stirring and swirling effects of the flow field of the cone 103, the injected oxygen can be fully and evenly distributed in the flow field, and the lower oxygen injection pipe 108 also forms an oxygen-enriched area in the area where the lower constriction 102 is located, that is, the oxygen concentration in this area is higher than that in the columnar part of the decomposition furnace 1. In this way, the coke can be fully stirred and burned violently by the airflow in the above-mentioned flow field and oxygen-enriched area, so that most of the coke in the decomposition furnace 1 can be burned, avoiding excessive expansion of the violent combustion area. In this way, this scheme ensures that the amount of oxygen in the violent combustion area is sufficient while controlling the expansion of the combustion space in the violent combustion area, and makes the combustion space within a reasonable range, that is, avoiding the elongation of the burning area of ​​the coke.

[0031] A flue gas analysis monitoring device 112 is provided at the upper part of the upper section of the decomposition furnace 1, and a flue gas analysis monitoring device 213 is provided below the upper constriction 101. Both flue gas analysis monitoring devices are used to detect O2, CO and NO x When the flue gas analysis monitoring device 113 detects that the CO concentration is ≥ 2000ppm, it means that there is insufficient oxygen in the decomposition furnace 1. At the same time, the oxygen supply of the lower oxygen injection pipe 108 and the upper oxygen injection pipe 107 is increased to fully burn the unburned combustibles. When NO x Concentration ≥500mg / Nm 3 When the temperature is 0.0400 W, it indicates that a local high temperature zone appears in the combustion process of the decomposition furnace 1. At this time, the upper gasification gas nozzle 106 injects gasification gas into this position to reduce NO x When the flue gas analysis monitoring device 113 detects that the O2 concentration is ≥ 5%, the oxygen supply of the lower oxygen injection pipe 108 should also be reduced. By monitoring the gas components by the flue gas analysis monitoring device 112 and the flue gas analysis monitoring device 2113, the oxygen supply and gasification gas supply can be matched with the staged combustion requirements of the decomposition furnace 1, the staged combustion effect can be deepened, and the effect of reducing pollutants and increasing the disposal amount of alternative fuels can be achieved.

[0032] The conventional column coal injection pipe 110 on the column of the decomposition furnace 1 is adjusted to a coal powder oxygen-enriched burner 109 in this solution. The structure is in the form of a sleeve. The inside of the sleeve is still the column coal injection pipe 110. The outside of the sleeve transports oxygen-enriched air with an oxygen concentration of 80%. After the coal powder is injected into the decomposition furnace 1, it is directly combined with the 80% oxygen concentration, which reduces the activation energy of coal powder combustion on the one hand, and increases the flame temperature on the other hand, further intensifying the combustion intensity of the intense combustion zone. At the same time, the high temperature in the intense combustion zone will be taken away by the tertiary air volume increased by the oxygen-enriched combustion of the rotary kiln 2, alleviating the risk of reduced refractory life and clinker sintering due to local high temperature.

[0033] The circulating fluidized bed system 3 includes a circulating fluidized bed 301, a primary cyclone separator 302, a secondary cyclone separator 303, a semi-gasified gas detection device 311 and a gasified gas detection device 312. The circulating fluidized bed 301 is provided with an alternative fuel feed port 305, a coal powder feed port 304, an alternative fuel bottom slag discharge channel 306 and an air outlet channel 307 located at the upper part, the air outlet channel 307 is connected to the primary cyclone separator 302, the exhaust channel 308 at the upper part of the primary cyclone separator 302 is connected to the secondary cyclone separator 303, and the exhaust channel 309 is connected to the secondary cyclone separator 303. The gas channel 308 is provided with a semi-gasified gas outlet and a two-stage cyclone separator valve 309. The two-stage cyclone separator valve 309 is located between the semi-gasified gas outlet and the secondary cyclone separator 303. The semi-gasified gas detection device 311 is provided at the semi-gasified gas outlet. The gas outlet at the upper part of the secondary cyclone separator 303 is a gasified gas outlet and is provided with the gasified gas detection device 312. The bottom channel 310 of the secondary cyclone separator 303 is connected to the lower part of the circulating fluidized bed 301 through the bottom channel 310 of the primary cyclone separator 302. This scheme adopts a circulating fluidized bed system 3 as a pre-decomposition furnace 1 for alternative fuels. The overall process is to create an oxygen-poor atmosphere in the furnace for alternative fuels by introducing air with an oxygen-rich concentration with insufficient oxygen, and perform oxygen-rich pyrolysis and gasification. After the alternative fuels are pyrolyzed and gasified, pyrolysis and gasification products are formed, which are sent to the corresponding parts of the decomposition furnace 1 for combustion, or to create a reducing atmosphere for the decomposition furnace 1. In this solution, the alternative fuel disposal amount achieved by the circulating fluidized bed system 3 can replace 50% of the coal powder in the decomposition furnace 1, meeting the demand for using a large proportion of alternative fuel.

[0034] The bottom of the circulating fluidized bed 301 is connected to a tertiary air branch pipe 402 and an air inlet pipe 313. The tertiary air branch pipe 402 has a valve and an inlet connected to the tertiary air pipe 4. The air inlet pipe 313 is provided with three air inlet branches, which are a dechlorination agent supply pipe, a water vapor supply pipe and an oxygen supply pipe, respectively. Valves are provided on the three air inlet branches, and the oxygen supply pipe is connected to the oxygen blower 314. Based on the circulating fluidized bed system 3, the process of supplying gas to the circulating fluidized bed 301 in this scheme is as follows: Under normal circumstances, one part is the high-temperature tertiary air (1100°C) from the tertiary air duct 4, which is sent to the bottom of the circulating fluidized bed 301 through the tertiary air branch pipe 402, and the other part is supplied through the oxygen blower 314, with oxygen-enriched air with an oxygen concentration of more than 80% prepared by the oxygen production system. The temperature of the oxygen-enriched air is slightly higher than the normal temperature (40-50°C). By adjusting the ratio of the tertiary air volume and the oxygen-enriched air volume sent to the circulating fluidized bed 301, from the overall point of view, after the tertiary air and the oxygen-enriched air are fully mixed, the oxygen concentration of the supplied gas is basically 40%-60%, and the excess air coefficient is 0.2-0.5. The use of this oxygen-rich and oxygen-poor gas supply method can not only strengthen the gasification process, accelerate gasification, and increase the amount of alternative fuels that can be handled by the circulating fluidized bed 301, but also reduce the total amount of gas supply and reduce the input of nitrogen in the traditional circulating fluidized bed 301 gas supply, thereby correspondingly reducing the heat loss of flue gas and increasing the calorific value of pyrolysis gas. The pyrolysis temperature of the circulating fluidized bed 301 is about 700-800°C. Within this temperature range, the pyrolysis reaction direction can be directed toward gasification, reducing the generation of coke and increasing the generation of pyrolysis gas. At the same time, the high temperature can ensure the gasification speed and increase the amount of alternative fuels handled.

[0035] In this solution, the semi-gasified gas detection device 311 is used to detect the calorific value of the combustible gas, the components of the combustible gas, and the particle size of the unburned coke, and the gasified gas detection device 312 is used to detect the calorific value of the combustible gas and the components of the combustible gas. When the calorific value of the gasified gas (including H2, CO, CH4, alkane gas, etc.) at the outlet of the circulating fluidized bed 301 is monitored to be lower than 1000 kcal / m 3 When the gasification efficiency is lower than 30% (gasification efficiency is defined as the ratio of the heat output of gasification gas to the heat input of alternative fuel, excluding the heat output of coke), it indicates that the pyrolysis gasification condition of the circulating fluidized bed 301 is not good. In this case, saturated steam from the drum of the cement kiln waste heat boiler is selected as the gasifier (0.3MPa, about 150℃) and is supplied from the bottom of the circulating fluidized bed 301. The water vapor can react with the coke that has not been pyrolyzed under high temperature and oxygen-deficient conditions: C+H2O→CO+H2, thereby increasing the calorific value of the gasifier. When the calorific value of the gasification gas at the outlet is greater than 1000kcal / m 3 When the gasification efficiency is higher than 30%, close the steam valve.

[0036] During the operation of the circulating fluidized bed system 3, the alternative fuel added to the circulating fluidized bed 301 is wrapped by circulating quartz sand. The main functions of the circulating quartz sand are: heat storage in the furnace body; ensuring the fluidity of the alternative fuel material in the circulating fluidized bed 301. The bed layer and the material are violently stirred and flowed by bottom aeration, the temperature distribution in the furnace is uniform, the gas flow rate is fast, and the convection heat transfer intensity is high. Therefore, the requirements for the moisture content, calorific value, fixed carbon, and volatile matter of the alternative fuel material are not high, and the tolerance for particle size is relatively good. Alternative fuels not exceeding 10 cm can be added, and the material only needs to be subjected to primary crushing treatment.

[0037] The alternative fuel is added to the furnace through the alternative fuel feed port 305. Under normal circumstances, the water vapor and dechlorinating agent valves at the bottom of the furnace are closed, and only tertiary air and oxygen with a concentration of more than 80% are supplied. The oxygen blower 314 supplies oxygen at a pressure of more than 50kPa to ensure that the materials in the furnace are in a circulating fluidized state. Oxygen and tertiary air are both input through independent pipelines to achieve that the two are not mixed in the gas supply pipeline. The main reason for mixing in the furnace is to ensure that after the oxygen with a pressure of 50kPa is supplied, it will not flow back to the tertiary air duct 4 through the tertiary air branch pipe 402. After the oxygen and tertiary air are mixed in the furnace, the overall oxygen concentration supplied is controlled at 40%-60%, so that the oxygen-rich gas can be used as a pyrolysis gasification agent. Compared with the conventional use of air as a gasification agent, on the one hand, the amount of gas supplied is reduced, and the exhaust heat loss is reduced. On the other hand, the high oxygen concentration can improve the pyrolysis gasification efficiency and accelerate the conversion of alternative fuels into coke and gasification gas.

[0038] Since high-temperature tertiary air and pure oxygen are supplied from the bottom of the circulating fluidized bed 301, the gasification temperature in the furnace is relatively high, and the alternative fuel undergoes a partial combustion reaction. When the low calorific value of the alternative fuel (waste textile, RDF, domestic garbage, sludge, biomass, etc.) is ≥1000kcal / kg, the furnace temperature can be basically maintained at 700-800℃ through the heat release of the combustion of the alternative fuel. When the low calorific value of the alternative fuel is <800kcal / kg and the furnace temperature is significantly lower than 800℃, the pulverized coal channel is opened, and the pulverized coal supply is calculated to determine the pulverized coal flow rate according to the gap between the actual calorific value of the alternative fuel and 1000kcal / kg, which is used to maintain the furnace temperature.

[0039] The gas-solid mixture of pyrolysis gas and incompletely pyrolyzed fixed carbon discharged from the primary cyclone separator 302 is called semi-gasified gas. c Smaller than bed material particle size d 床料 , critical particle size d c The gasified alternative fuel passes through the primary cyclone separator 302, where solid materials with different solid phase particle sizes are separated, and the solid phase particle size is less than or equal to the critical particle size d cThe solid phase particle size is larger than the critical particle size d c The recovered gas is sent back to the circulating fluidized bed 301 through the corresponding bottom channel 310. After the first-stage separation, the semi-gasified gas discharged from the first-stage cyclone separator 302 is an incompletely gasified semi-gasified gas. The semi-gasified gas is actually a gas-solid mixture of gasified gas and incompletely pyrolyzed fixed carbon, including alkanes, H2, CO, solid semi-coke (particle size ≤ 1 mm), residual oxygen, CO2, H2O, etc.

[0040] The separation effect of the secondary cyclone separator 303 is better than that of the primary cyclone separator 302. The separation effect of the secondary cyclone separator 303 can achieve the emission of gasified gas without unburned coke, that is, the solid materials originally in the semi-gasified gas are also recovered. This part of the particles separated by the secondary cyclone separator 303 has a corresponding lower channel, which is sent to the lower channel of the primary cyclone separator 302 and returns to the circulating fluidized bed 301 for circulation.

[0041] The final detection of clinker quality is used to determine whether to add dechlorinating agent and the amount of dechlorinating agent to be added. The dechlorinating agent generally uses CaO, that is, the clinker produced by cement production as the dechlorinating agent. After adding the dechlorinating agent, the free chlorine precipitated by the alternative fuel at high temperature will combine with CaO to form CaCl2, which will be fixed by combining with the bed material and will not be brought into the gasification gas, thereby alleviating the impact of the chlorine element in the alternative fuel on the system. The control standard for the amount of dechlorinating agent is generally that the chlorine content of the clinker increases significantly after the use of the alternative fuel, and when the chlorine content in the clinker is 0.03%-0.04% (because the detection of clinker is delayed, when the chlorine content in the clinker does not reach the national standard of 0.06%, the dechlorinating agent should be added to prevent the chlorine content in the clinker from exceeding the standard).

[0042] A sand sorting device is provided in the bed layer above the bottom air inlet of the circulating fluidized bed 301. The incombustibles in the alternative fuel will be combined with the sand and ash for melting and the volume will increase. The sand sorting device is used to separate the incombustibles with increased volume and discharge them through the alternative fuel slag discharge channel.

[0043] In this scheme, the oxygen generator 5 produces 80% oxygen and then passes through the oxygen mixing device 6 to form oxygen-enriched air with an oxygen concentration of about 35%, which is input into the rotary kiln 2 at the kiln head to replace the kiln head primary air. The oxygen-enriched air is sent to the kiln head burner together with the coal powder to form oxygen-enriched combustion in the rotary kiln 2, so that the temperature of the clinker falling into the grate cooler 7 will be increased, and the temperature of the tertiary air formed will also be increased from the conventional 1000℃ to 1100℃.

[0044] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the inventive concept and technical solution of the present invention, or the inventive concept and technical solution are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A cement kiln system that uses a large proportion of alternative fuels coupled with oxygen-enriched and staged combustion, characterized by: The invention comprises a circulating fluidized bed system (3), a decomposition furnace (1), a rotary kiln (2) and a grate cooler (7), wherein the circulating fluidized bed system (3) is used to process alternative fuels to form semi-gasified gas and gasified gas, the kiln tail of the rotary kiln (2) is connected to the bottom of the decomposition furnace (1), the kiln head of the rotary kiln (2) also transports tertiary air into the decomposition furnace (1) through a tertiary air duct (4), the decomposition furnace (1) is divided into three sections from top to bottom by a lower constriction (102) and an upper constriction (101), the bottom of the decomposition furnace (1) is provided with a cone (103), and the kiln tail smoke chamber of the cement kiln to the cone (103) is connected to the cement kiln. 03), a bottom gasification gas nozzle (105) is provided between the coal injection pipes (110), an upper gasification gas nozzle (106) is provided at the upper middle section of the decomposition furnace (1), the bottom gasification gas nozzle (105) and the upper gasification gas nozzle (106) are both connected to the gasification gas outlet of the circulating fluidized bed system (3) for injecting gasification gas generated by alternative fuel; a semi-gasification gas nozzle (104) is provided at the upper lower section of the decomposition furnace (1), the semi-gasification gas nozzle (104) is connected to the semi-gasification gas outlet of the circulating fluidized bed system (3) for injecting semi-gasification gas generated by alternative fuel.

2. The cement kiln system of using alternative fuels in large proportion coupled with oxygen-enriched and staged combustion according to claim 1, characterized in that: The conical portion (103) of the decomposition furnace (1) is sprayed with gasification gas through the bottom gasification gas nozzle (105), the middle section of the decomposition furnace (1) is sprayed with gasification gas through the upper gasification gas nozzle (106), and the position where the semi-gasification gas nozzle (104) sprays semi-gasification gas in the lower section of the decomposition furnace (1) is located between the coal injection point and the lower constriction (102), and the semi-gasification gas is sprayed in the intense combustion zone of the coke.

3. The cement kiln system of claim 1 that uses a large proportion of alternative fuels coupled with oxygen-enriched and staged combustion, characterized in that: The bottom gasification gas nozzle (105) and the semi-gasification gas nozzle (104) are arranged in a tangential circle form, which forms a corresponding gas supply plane in the horizontal direction. A plurality of nozzles are arranged on the gas supply plane. The jetting direction of the nozzles is the tangent direction of the furnace body side wall on the gas supply plane. The plurality of nozzles are arranged symmetrically with the furnace body center of the decomposition furnace (1) as the center. The upper gasification gas nozzle (106) is radially arranged in the decomposition furnace (1). There is an inclination angle between the nozzle and the axis of the furnace body in the vertical direction. The height of the material sprayed by the nozzle is higher than the gas supply plane where the nozzle is arranged. At the same time, the rotation direction of the material sprayed by the nozzle in the horizontal direction is consistent with the rotation direction of the airflow in the furnace.

4. The cement kiln system of claim 1 that uses alternative fuels in large proportions coupled with oxygen-enriched and staged combustion, characterized in that: The semi-gasified gas nozzle (104) is a sleeve-type burner, comprising an inner tube portion and an outer tube portion sleeved outside the inner tube portion, the inner sleeve being used to spray out the semi-gasified gas, and the outer sleeve being used to spray out oxygen or oxygen-enriched air.

5. The cement kiln system of claim 1 that uses a large proportion of alternative fuels coupled with oxygen-enriched and staged combustion, characterized in that: The upper constriction (101) and the lower constriction (102) are both provided with corresponding oxygen injection pipes, namely an upper oxygen injection pipe (107) and a lower oxygen injection pipe (108); the tertiary air duct (4) is connected to the top of the cone (103); a tertiary air injection pipe (401) is provided at the connection between the tertiary air duct (4) and the top of the cone (103) for injecting oxygen into the cone (103) through the connection.

6. The cement kiln system of claim 1 that uses alternative fuels in large proportions coupled with oxygen-enriched and staged combustion, characterized in that: The upper part of the upper section of the decomposition furnace (1) is provided with a first flue gas analysis monitoring device (112), and a second flue gas analysis monitoring device (113) is provided below the upper constriction (101). Both flue gas analysis monitoring devices are used to detect O2, CO and NO x concentration; when the flue gas analysis monitoring device 2 (113) detects that the CO concentration is not less than the threshold value, it indicates that there is insufficient oxygen in the decomposition furnace (1), and at the same time, the oxygen supply of the lower oxygen injection pipe (108) and the upper oxygen injection pipe (107) is increased to fully burn the unburned combustibles; when any flue gas analysis monitoring device detects NO x When the concentration is not less than the threshold value, it indicates that a local high temperature zone appears in the combustion process of the decomposition furnace (1). At this time, the upper gasification gas nozzle (106) injects gasification gas into this position to reduce NO x When the flue gas analysis monitoring device II (113) detects that the O2 concentration is not less than 5%, the oxygen supply of the lower oxygen injection pipe (108) should also be reduced.

7. A cement kiln system using alternative fuels in large proportions coupled with oxygen-enriched and staged combustion according to any one of claims 1 to 6, characterized in that: The circulating fluidized bed system (3) comprises a circulating fluidized bed (301), a primary cyclone separator (302), a secondary cyclone separator (303), a semi-gasified gas detection device (311) and a gasified gas detection device (312); the circulating fluidized bed (301) is provided with an alternative fuel feed port (305), a coal powder feed port (304), an alternative fuel bottom slag discharge channel (306) and an air outlet channel (307) located at the top; the air outlet channel (307) is connected to the primary cyclone separator (302); and the exhaust channel (308) at the top of the primary cyclone separator (302) is connected to the secondary cyclone separator (303). The exhaust passage (308) is provided with a semi-gasified gas outlet and a two-stage cyclone separator valve (309), the two-stage cyclone separator valve (309) is located between the semi-gasified gas outlet and the secondary cyclone separator (303), the semi-gasified gas detection device (311) is arranged at the semi-gasified gas outlet, the gas outlet at the top of the secondary cyclone separator (303) is a gasified gas outlet and is provided with the gasified gas detection device (312); the bottom channel (310) of the secondary cyclone separator (303) is connected to the lower part of the circulating fluidized bed (301) through the bottom channel (310) of the primary cyclone separator (302).

8. The cement kiln system of claim 7, which uses alternative fuels in large proportions and couples oxygen-enriched and staged combustion, is characterized in that: The bottom of the circulating fluidized bed (301) is connected to a tertiary air branch pipe (402) and an air inlet pipe (313). The tertiary air branch pipe (402) has a valve and an inlet connected to the tertiary air pipe (4). The air inlet pipe (313) is provided with three air inlet branches, which are respectively a dechlorinating agent supply pipe, a water vapor supply pipe and an oxygen supply pipe. The three air inlet branches are all provided with valves. The oxygen supply pipe is connected to an oxygen blower (314).

9. The cement kiln system of claim 8, characterized in that: The semi-gasified gas detection device (311) is used to detect the calorific value of the combustible gas, the components of the combustible gas, and the particle size of the unburned coke, and the gasified gas detection device (312) is used to detect the calorific value of the combustible gas and the components of the combustible gas; the gasification efficiency is the ratio of the output gasification gas heat to the input alternative fuel heat, excluding the output coke heat; the process of supplying gas to the circulating fluidized bed (301) is as follows: under normal circumstances, a part of the high-temperature tertiary air from the tertiary air duct (4) is sent to the bottom of the circulating fluidized bed (301) through the tertiary air branch pipe (402), and oxygen-enriched air is supplied to the bottom of the circulating fluidized bed (301) from the air inlet pipe (313). By adjusting the tertiary air volume and the ratio of the amount of oxygen-enriched air fed into the circulating fluidized bed (301). Overall, after the tertiary air and the oxygen-enriched air are fully mixed, the oxygen concentration of the supplied gas is basically between 40% and 60%, and the excess air coefficient is between 0.2 and 0.

5. When it is monitored that the calorific value of the gasified gas at the outlet of the circulating fluidized bed (301) is lower than the threshold value and the gasification efficiency is lower than the threshold value, it indicates that the pyrolysis gasification condition of the circulating fluidized bed (301) is not good. In this case, saturated steam in the drum of the cement kiln waste heat boiler is selected as the gasifying agent and fed from the bottom of the circulating fluidized bed (301), thereby increasing the calorific value of the gasifying agent. When the calorific value of the gasified gas at the outlet is greater than the threshold value and the gasification efficiency is higher than the threshold value, the water vapor supply is stopped.

10. The cement kiln system of claim 1 that uses alternative fuels in large proportions coupled with oxygen-enriched and staged combustion, characterized in that: The oxygen production device (5) produces oxygen with a concentration of 80%, and then passes through the oxygen mixing device (6) to form oxygen-enriched air with an oxygen concentration of about 35%, which is then input into the rotary kiln (2) at the kiln head to replace the primary air at the kiln head; the oxygen-enriched air is sent to the kiln head burner together with the pulverized coal to form oxygen-enriched combustion in the rotary kiln (2).

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