Energy-saving and environment-friendly pulverized coal preparation, graded collection and conveying system and method for cement kiln

Abstract

The invention provides an energy-saving and environment-friendly pulverized coal preparation, graded collection and conveying system and method for a cement kiln. A coal mill, a cyclone and a dust collector are sequentially communicated; a discharge port of the cyclone cylinder is communicated with a feed port of the coarse powder screw conveyor, and the coarse powder screw conveyor, the coarse powder rotary feeder and the kiln tail pulverized coal pneumatic conveying pump are communicated in sequence; a discharge port of the dust collector is communicated with a feed port of the fine powder screw conveyor, and the fine powder screw conveyor, the fine powder rotary feeder and the kiln head pulverized coal pneumatic conveying pump are sequentially communicated. Coarse powder is fed into the kiln tail, the combustion time of the pulverized coal is properly prolonged, and the phenomenon that the kiln tail is skinned and blocked due to too high local temperature caused by rapid combustion of the pulverized coal is avoided; meanwhile, by combining the self-denitration design of the original system, the retention time of the pulverized coal in the reduction area of the decomposing furnace is prolonged, the CO generation amount is increased, the reaction time of CO and NOx is prolonged, and the NOx concentration is effectively reduced; feeding the fine powder into a kiln head to accelerate the combustion of the pulverized coal; the proportion of coarse powder and fine powder can be adjusted, and combustion performance is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of coal powder preparation, and in particular relates to a system and method for preparing, grading, collecting and conveying energy-saving and environment-friendly coal powder for cement kilns. Background Art

[0002] Coal powder preparation plays a vital role in the metallurgical, building materials and other industries. Raw coal is generally ground to a certain fineness by a ball mill or a vertical roller mill. Depending on the quality of the coal, the general coal powder preparation system needs to grind the coal powder to about 2-15% of the 80μm sieve residue. After the coal powder is selected by the classifier, the coarse powder returns to the mill for further grinding. The fine powder enters the dust collector with the air flow and is collected by the dust collector, stored in the coal powder bin, and then transported to the corresponding section for incineration to provide the heat required by the system.

[0003] The fineness of coal powder has a significant impact on its combustion efficiency. Finer coal powder particles are more likely to be suspended in the airflow during the combustion process and are not easy to deposit and accumulate, providing a larger surface area, thereby increasing the contact area with oxygen, fully reacting with oxygen, reducing the possibility of incomplete combustion, and thus reducing the generation of harmful substances such as carbon monoxide (CO) and volatile organic compounds (VOCs). At the same time, it promotes the combustion reaction and increases the combustion rate. However, the finer the coal powder is ground, the higher the system power consumption.

[0004] In the prior art, the coal powder preparation system usually does not distinguish between the coarseness and fineness of the coal powder, and uniformly transports the coal powder to the boiler for combustion. However, for cement kilns, the requirements for the fineness of coal powder at the kiln tail and kiln head are not exactly the same. The kiln head needs finer coal powder to increase the combustion speed, burnout rate, and flame temperature, while improving the thermal efficiency of the system and reducing coal consumption; while the kiln tail needs slightly coarser coal powder. On the one hand, it can extend the combustion time of the coal powder and avoid the rapid combustion of the coal powder causing excessive local temperature and causing crusting and blockage at the kiln tail. On the other hand, it can extend the residence time of the coal powder in the reduction zone of the decomposition furnace. At the same time, combined with the self-denitrification design of the original system, it can increase the generation of CO, extend the reaction time of CO and NOx, and effectively reduce the NOx concentration. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention aims to propose a system and method for energy-saving and environmentally friendly coal powder preparation, graded collection and transportation for cement kilns. The system and method for energy-saving and environmentally friendly coal powder preparation, graded collection and transportation solves the problem that the coal powder preparation system in the prior art usually does not distinguish between the coarseness and fineness of coal powder, and uniformly transports the coal powder to the boiler for combustion. The coal powder is graded into coarse powder and fine powder to meet the combustion requirements of the kiln tail and kiln head respectively, thereby reducing the coal consumption of the cement kiln, improving the stability of the system, and reducing the generation of NOx.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] An energy-saving and environment-friendly coal powder preparation, classification collection and transportation system for cement kilns, comprising a coal powder preparation system, a coarse powder collection system and a fine powder collection system;

[0008] The coal powder preparation system comprises a coal mill, a cyclone and a dust collector, and the coal mill, the cyclone and the dust collector are connected in sequence to form a coal powder preparation pipeline;

[0009] The coarse powder collection system includes a coarse powder screw conveyor, a coarse powder rotary feeder and a kiln tail coal powder pneumatic conveying pump, the discharge port of the cyclone is connected with the feed port of the coarse powder screw conveyor, and the discharge port of the coarse powder screw conveyor, the coarse powder rotary feeder and the kiln tail coal powder pneumatic conveying pump are connected in sequence to form a coarse powder collection and conveying pipeline;

[0010] The fine powder collection system includes a fine powder screw conveyor, a fine powder rotary feeder and a kiln head coal powder pneumatic conveying pump, the discharge port of the dust collector is connected to the feed port of the fine powder screw conveyor, and the discharge port of the fine powder screw conveyor, the fine powder rotary feeder and the kiln head coal powder pneumatic conveying pump are connected in sequence to form a fine powder collection and conveying pipeline;

[0011] The air inlet of the coal powder pneumatic conveying pump at the kiln tail and the air inlet of the coal powder pneumatic conveying pump at the kiln head are respectively connected to the Roots blower.

[0012] Furthermore, the fineness of the coarse powder collected by the cyclone is 15-20% of the 80 μm sieve residue, and the fineness of the fine powder collected by the dust collector is less than 4% of the 80 μm sieve residue.

[0013] Furthermore, the powder selection efficiency of the cyclone is 60%.

[0014] Furthermore, the feed port of the kiln tail coal powder pneumatic conveying pump is provided with a coarse powder sampler for measuring the fineness of the coal powder entering the kiln tail coal powder pneumatic conveying pump, and the feed port of the kiln head coal powder pneumatic conveying pump is provided with a fine powder sampler for measuring the fineness of the coal powder entering the kiln head coal powder pneumatic conveying pump.

[0015] Furthermore, the second discharge port of the coarse powder screw conveyor is connected to the feed port of the coal powder pneumatic conveying pump at the kiln head through the coarse powder valve, and the second discharge port of the fine powder screw conveyor is connected to the feed port of the coal powder pneumatic conveying pump at the kiln tail through the fine powder valve.

[0016] Furthermore, the kiln tail coal powder pneumatic conveying pump is connected to the kiln tail coal powder bin and the kiln head coal powder bin respectively through a switching valve 1;

[0017] The kiln head coal powder pneumatic conveying pump is respectively connected with the kiln head coal powder bin and the kiln tail coal powder bin through the switching valve 2.

[0018] Furthermore, it also includes an inert gas fire extinguishing system, which is respectively connected to the raw coal bin, coal mill, cyclone, and dust collector. The discharge port of the raw coal bin is connected to the feed port of the coal mill through a quantitative feeder.

[0019] Furthermore, the air outlet of the dust collector is connected to the air inlet of the exhaust fan, and the air outlet of the exhaust fan is connected to the chimney and the air inlet of the coal mill respectively.

[0020] A method for preparing, collecting and conveying energy-saving and environment-friendly coal powder for cement kiln, comprising:

[0021] S1, the raw coal enters the coal mill for grinding, and the ground coal powder enters the cyclone along with the gas out of the mill;

[0022] S2, the coarse powder collected in the cyclone enters the coarse powder screw conveyor, the fine powder out of the cyclone enters the dust collector with the air flow, and the fine powder collected by the dust collector enters the fine powder screw conveyor;

[0023] The coarse powder in the coarse powder screw conveyor passes through the coarse powder rotary feeder and then enters the coal powder pneumatic conveying pump at the kiln tail;

[0024] The fine powder in the fine powder screw conveyor passes through the fine powder rotary feeder and then enters the kiln head coal powder pneumatic conveying pump;

[0025] S3. The pulverized coal entering the pneumatic conveying pump at the kiln tail and the pneumatic conveying pump at the kiln head are respectively powered by Roots blowers and pumped to the pulverized coal bin at the kiln tail and the pulverized coal bin at the kiln head to provide coal for combustion to the kiln tail and the kiln head.

[0026] Furthermore, in step S2, the fineness of the coal powder entering the kiln tail coal powder pneumatic conveying pump is measured by a coarse powder sampler, and according to the measured fineness, the operating parameters of the coal mill, the rotation speed of the coarse powder rotary feeder, and the opening and closing degree of the fine powder valve are adjusted to control the ratio of coarse powder and fine powder entering the kiln tail coal powder pneumatic conveying pump; when the rotation speed of the coarse powder rotary feeder and the opening and closing degree of the fine powder valve are adjusted, the coarse powder in the coarse powder screw conveyor passes through the coarse powder rotary feeder and is mixed with the fine powder in the fine powder screw conveyor controlled by the fine powder valve, and after mixing, it enters the kiln tail coal powder pneumatic conveying pump.

[0027] Furthermore, in step S2, the fineness of the coal powder entering the kiln head coal powder pneumatic conveying pump is measured by a fine powder sampler, and the operating parameters of the coal mill, the rotation speed of the fine powder rotary feeder, and the opening and closing degree of the coarse powder valve are adjusted according to the measured fineness to control the ratio of coarse powder and fine powder entering the kiln head coal powder pneumatic conveying pump; when the rotation speed of the fine powder rotary feeder and the opening and closing degree of the coarse powder valve are adjusted, the fine powder in the fine powder screw conveyor passes through the fine powder rotary feeder and is mixed with the coarse powder in the coarse powder screw conveyor controlled by the coarse powder valve, and after mixing, enters the kiln head coal powder pneumatic conveying pump.

[0028] Furthermore, in step S2, after the gas exiting the dust collector is discharged through the exhaust fan, a portion of the gas is returned to the coal mill for recycling as circulating air, and the rest of the gas is discharged through the chimney.

[0029] Compared with the prior art, the system and method for preparing, grading, collecting and conveying energy-saving and environmentally friendly pulverized coal for cement kilns according to the present invention have the following advantages:

[0030] (1) The energy-saving and environment-friendly pulverized coal preparation, graded collection and transportation system for cement kilns described in the present invention is provided with a cyclone and a dust collector, and utilizes the huge difference in the sensitivity of the cyclone and the dust collector to dust fineness to collect coarse powder and fine powder respectively, thereby effectively realizing the graded collection of pulverized coal; and the cyclone is provided between the coal mill and the dust collector. After the coarse powder is collected by the cyclone, the dust concentration entering the dust collector is greatly reduced, the operating load of the dust collector is reduced, the dust collection effect of the dust collector can be improved, and the life of the filter bag is increased.

[0031] (2) The energy-saving and environment-friendly pulverized coal preparation, graded collection and transportation system for cement kilns described in the present invention only requires a 60% cyclone efficiency to meet the demand for pulverized coal at the kiln tail, and the cyclone resistance can be reduced to 200-300 Pa. At the same time, since the dust concentration entering the dust collector is reduced by 60%, the resistance of the dust collector is also reduced to 600-800 Pa, and the overall resistance of the whole system is also reduced, making the system more energy-efficient.

[0032] (3) The energy-saving and environment-friendly coal powder preparation, classification collection and transportation system for cement kilns described in the present invention is provided with two sets of samplers to measure the fineness of the coal powder entering the pneumatic conveying pump of the coal powder at the end of the kiln and the pneumatic conveying pump of the coal powder at the head of the kiln respectively. According to the measured fineness and production requirements, the rotation speed of the coarse powder rotary feeder and the fine powder rotary feeder can be adjusted to achieve a flexible and adjustable ratio of coarse powder to fine powder, thereby providing more refined guidance for the operation and operation of the entire system.

[0033] (4) The method for preparing, grading, collecting and conveying energy-saving and environmentally friendly coal powder for cement kiln described in the present invention is to grade the coal powder into coarse and fine grades, and convey the coarse powder into the kiln tail, appropriately prolong the coal powder combustion time, and avoid the rapid combustion of the coal powder leading to excessive local temperature and causing the kiln tail to be blocked by crusting. At the same time, combined with the self-denitrification design of the original system, the residence time of the coal powder in the reduction zone of the decomposition furnace is prolonged, the generation of CO is increased, the reaction time of CO and NOx is prolonged, and the NOx concentration is effectively reduced; the fine powder is conveyed into the kiln head, the coal powder combustion is accelerated, the flame temperature, thermal strength and thermal efficiency are increased, the system heat consumption is reduced, and the clinker quality is improved; at the same time, the free combination of coarse powder and fine powder, as well as the flexible switching of the coarse powder and fine powder conveying paths can be realized, the coal powder fineness and particle size distribution can be reasonably adjusted, and the combustion performance can be improved. The application of the present invention to actual production will bring huge economic benefits and has good promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0035] Figure 1 A schematic diagram of the overall structure provided for an embodiment of the present invention.

[0036] Description of reference numerals:

[0037] 1. Raw coal bunker; 2. Quantitative feeder; 3. Coal mill; 31. Water spray port; 32. Dust-proof port; 4. Cyclone; 5. Dust collector; 6. Exhaust fan; 7. Coarse powder screw conveyor; 8. Fine powder screw conveyor; 9. Coarse powder rotary feeder; 10. Fine powder rotary feeder; 11. Coarse powder valve; 12. Fine powder valve; 131. Coarse powder sampler; 132. Fine powder sampler; 14. Pneumatic conveying pump for coal powder at the end of kiln; 15. Pneumatic conveying pump for coal powder at the head of kiln; 161. Roots blower 1; 162. Roots blower 2; 163. Roots blower 3; 171. Switching valve 1; 172. Switching valve 2; 18. Explosion-proof valve; 19. Pneumatic stop valve; 20. Inert gas fire extinguishing system. DETAILED DESCRIPTION

[0038] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0039] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0040] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0041] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0042] like Figure 1 , an energy-saving and environmentally friendly pulverized coal preparation, classification collection and transportation system for cement kilns, including a pulverized coal preparation system, a coarse powder collection system and a fine powder collection system;

[0043] The pulverized coal preparation system comprises a raw coal bunker 1, a quantitative feeder 2, a coal mill 3, a cyclone 4 and a dust collector 5, wherein the raw coal bunker 1, the quantitative feeder 2, the coal mill 3, the cyclone 4 and the dust collector 5 are sequentially connected to form a pulverized coal preparation pipeline;

[0044] The coarse powder collection system includes a coarse powder screw conveyor 7, a coarse powder rotary feeder 9 and a kiln tail coal powder pneumatic conveying pump 14, the discharge port of the cyclone 4 is connected with the feed port of the coarse powder screw conveyor 7, and the discharge port of the coarse powder screw conveyor 7, the coarse powder rotary feeder 9, and the kiln tail coal powder pneumatic conveying pump 14 are connected in sequence to form a coarse powder collection and conveying pipeline;

[0045] The fine powder collection system includes a fine powder screw conveyor 8, a fine powder rotary feeder 10 and a kiln head coal powder pneumatic conveying pump 15, the discharge port of the dust collector 5 is connected with the feed port of the fine powder screw conveyor 8, and the discharge port 1 of the fine powder screw conveyor 8, the fine powder rotary feeder 10, and the kiln head coal powder pneumatic conveying pump 15 are connected in sequence to form a fine powder collection and conveying pipeline;

[0046] The air inlet of the coal powder pneumatic conveying pump 14 at the kiln tail and the air inlet of the coal powder pneumatic conveying pump 15 at the kiln head are connected to the Roots blower 16 respectively.

[0047] In a preferred embodiment of the present invention, the fineness of the coarse powder collected by the cyclone 4 is 15-20% of the 80 μm sieve residue, and the fineness of the fine powder collected by the dust collector 5 is less than 4% of the 80 μm sieve residue.

[0048] In actual use, the cyclone 4 and the dust collector 5 collect coarse powder and fine powder respectively, with the fineness of 80μm sieve residue 15-20% and 80μm sieve residue less than 4%, respectively. The separation process ensures that coal powder of different particle sizes can be effectively classified to meet the different requirements of coal powder particle size in different parts of the cement kiln. Coarse powder releases energy slowly during combustion due to its large particle size, and is suitable for use at the tail of the kiln to extend the combustion time and reduce the risk of local overheating. Fine powder has a smaller particle size and a fast combustion speed, and is suitable for use at the head of the kiln, where it can quickly release energy and improve combustion efficiency and thermal efficiency. Through the coordinated use of the cyclone 4 and the dust collector 5, the graded collection of coal powder is achieved, and the utilization efficiency of coal powder and the combustion performance of the cement kiln are optimized.

[0049] In a preferred embodiment of the present invention, the powder selection efficiency of the cyclone 4 is 60%.

[0050] In actual use, the powder selection efficiency of the cyclone 4 is 60%, which meets the coal powder demand at the kiln tail and is less than the 90% powder selection efficiency of the conventional cyclone. Therefore, the equipment resistance in this embodiment can be as low as 200-300Pa. At the same time, the dust collector 5 has a 60% reduction in the inlet dust concentration, and the equipment resistance can be as low as 600-800Pa. Therefore, the total resistance of the cyclone 4 and the dust collector 5 is lower than that of a single dust collector in a conventional coal powder preparation system, the exhaust fan 6 has a lower pressure, and the whole system is more energy-efficient.

[0051] In a preferred embodiment of the present invention, the coarse powder rotary feeder 9 and the fine powder rotary feeder 10 are both driven by variable frequency speed regulating motors.

[0052] In actual use, the coarse powder rotary feeder 9 adopts a variable frequency speed regulating motor, which can control the amount of coarse powder entering the coal powder pneumatic conveying pump 14 at the kiln tail, and the remaining part enters the coal powder pneumatic conveying pump 15 at the kiln head; the fine powder rotary feeder 9 adopts a variable frequency speed regulating motor, which can control the amount of fine powder entering the coal powder pneumatic conveying pump 15 at the kiln head, and the remaining part enters the coal powder pneumatic conveying pump 14 at the kiln tail.

[0053] In a preferred embodiment of the present invention, the feed inlet of the kiln tail coal powder pneumatic conveying pump 14 is provided with a coarse powder sampler 131 for measuring the fineness of the coal powder entering the kiln tail coal powder pneumatic conveying pump 14, and the feed inlet of the kiln head coal powder pneumatic conveying pump 15 is provided with a fine powder sampler 132 for measuring the fineness of the coal powder entering the kiln head coal powder pneumatic conveying pump.

[0054] In actual use, there are two sets of samplers, which are divided into a coarse powder sampler 131 and a fine powder sampler 132, which are respectively arranged at the feed inlets of the kiln tail coal powder pneumatic conveying pump 14 and the kiln head coal powder pneumatic conveying pump 15, to measure the fineness of the coal powder entering the kiln tail coal powder pneumatic conveying pump and the kiln head coal powder pneumatic conveying pump respectively. According to the measured fineness and production needs, in addition to normally adjusting the operating parameters of the mill 3 to adjust the ratio of coarse powder and fine powder, the ratio of coarse powder and fine powder can also be adjusted by adjusting the rotational speed of the coarse powder rotary feeder 9 and the fine powder rotary feeder 10, thereby adjusting the fineness of the coal powder entering the kiln tail coal powder pneumatic conveying pump and the kiln head coal powder pneumatic conveying pump.

[0055] In a preferred embodiment of the present invention, the second discharge port of the coarse powder screw conveyor 7 is connected to the feed port of the kiln head coal powder pneumatic conveying pump 15 through the coarse powder valve 11, and the second discharge port of the fine powder screw conveyor 8 is connected to the feed port of the kiln tail coal powder pneumatic conveying pump 14 through the fine powder valve 12.

[0056] In actual use, the coarse powder valve 11 and the fine powder valve 12 are pneumatic gate valves. The coarse powder from the second discharge port of the coarse powder screw conveyor 7 and the fine powder from the discharge port of the fine powder rotary feeder 10 are mixed and then enter the kiln head coal powder pneumatic conveying pump 15. By adjusting the rotation speed of the fine powder rotary feeder 10 and the opening and closing degree of the coarse powder valve 11, the ratio of coarse powder and fine powder entering the kiln head coal powder pneumatic conveying pump 15 is controlled, thereby adjusting the fineness of the coal powder entering the kiln head coal powder pneumatic conveying pump 15.

[0057] The fine powder from the discharge port 2 of the fine powder screw conveyor 8 is mixed with the coarse powder from the discharge port of the coarse powder rotary feeder 9 and then enters the kiln tail coal powder pneumatic conveying pump 14. The rotation speed of the coarse powder rotary feeder 9 and the opening and closing degree of the fine powder valve 12 are adjusted to control the ratio of coarse powder and fine powder entering the kiln tail coal powder pneumatic conveying pump 14, thereby adjusting the fineness of the coal powder entering the kiln tail coal powder pneumatic conveying pump 14.

[0058] In a preferred embodiment of the present invention, the number of Roots blowers is three, including Roots blower 1 161, Roots blower 2 162 and Roots blower 3 163. The Roots blower 1 161 is connected to the kiln tail coal powder pneumatic conveying pump 14 through a pneumatic plate valve, the Roots blower 2 162 is connected to the kiln head coal powder pneumatic conveying pump 15 through a pneumatic plate valve, and the Roots blower 3 163 is respectively connected to the kiln tail coal powder pneumatic conveying pump 14 and the kiln head coal powder pneumatic conveying pump 15.

[0059] In actual use, the Roots blower provides the necessary power for the coal powder pneumatic conveying pump, so that the coal powder can be transported from the coal mill to the coal powder bins at the kiln tail and kiln head by pneumatic conveying. There are multiple pneumatic plate valves between the Roots blower 3 163 and the coal powder pneumatic conveying pump 14 at the kiln tail and the coal powder pneumatic conveying pump 15 at the kiln head. The Roots blower 3 163 is used as a backup and can be immediately activated when other blowers need maintenance or fail to function, ensuring the continuity of coal powder conveying and the reliability of the system.

[0060] In a preferred embodiment of the present invention, the kiln tail coal powder pneumatic conveying pump 14 is connected to the kiln tail coal powder bin and the kiln head coal powder bin respectively through a switching valve 171.

[0061] The kiln head coal powder pneumatic conveying pump 15 is connected to the kiln tail coal powder bin and the kiln head coal powder bin respectively through the switching valve 2 172.

[0062] In actual use, two sets of switching valves are set up to realize the delivery of coal powder from the coal powder pneumatic conveying pump 14 at the kiln tail to the coal powder bin at the kiln head, and to realize the delivery of coal powder from the coal powder pneumatic conveying pump 15 at the kiln head to the coal powder bin at the kiln tail. When a pneumatic conveying pump or Roots blower fails, the coal powder conveying path can be switched at any time without affecting the normal operation of the subsequent system.

[0063] In a preferred embodiment of the present invention, an inert gas fire extinguishing system 20 is further included, and the inert gas fire extinguishing system 20 is connected to the raw coal bunker 1, the coal mill 3, the cyclone 4, and the dust collector 5 respectively.

[0064] A pneumatic stop valve 19 and an explosion-proof valve 18 are provided between the air outlet of the coal mill 3 and the air inlet of the cyclone 4 . A water spray port 31 is provided on the coal mill 3 . The dustproof port 32 above the coal mill 3 is connected to the dust collector 5 .

[0065] An explosion-proof valve 18 and a pneumatic stop valve 19 are provided in sequence between the air outlet of the cyclone 4 and the air inlet of the dust collector 5 .

[0066] The air outlet of the dust collector 5 is connected to the air inlet of the exhaust fan 6 through a pneumatic stop valve 19, and the air outlet of the exhaust fan 6 is connected to the air inlet of the chimney and the coal mill 3 respectively. The dust collector 5 is provided with an explosion-proof valve.

[0067] In actual use, an explosion-proof valve 18, a pneumatic stop valve 19, and an inert gas fire extinguishing system 20 are provided for safe explosion-proofing of the system.

[0068] A method for preparing, collecting and conveying energy-saving and environment-friendly coal powder for cement kiln, comprising:

[0069] S1, the raw coal in the raw coal bunker 1 passes through the quantitative feeder 2 and enters the coal mill 3 for grinding. The ground coal powder enters the cyclone 4 together with the outgoing gas;

[0070] S2, the coarse powder collected in the cyclone 4 enters the coarse powder screw conveyor 7, the fine powder out of the cyclone 4 enters the dust collector 5 with the air flow, and the fine powder collected by the dust collector 5 enters the fine powder screw conveyor 8;

[0071] The coarse powder in the coarse powder screw conveyor 7 passes through the coarse powder rotary feeder 9 and enters the coal powder pneumatic conveying pump 14 at the kiln tail;

[0072] The fine powder in the fine powder screw conveyor 8 passes through the fine powder rotary feeder 10 and enters the kiln head coal powder pneumatic conveying pump 15;

[0073] S3. The pulverized coal entering the pneumatic conveying pump 14 at the kiln tail and the pulverized coal entering the pneumatic conveying pump 15 at the kiln head are respectively powered by the Roots blower 16 and pumped to the pulverized coal bin at the kiln tail and the pulverized coal bin at the kiln head to provide coal for combustion to the kiln tail and the kiln head.

[0074] In actual use, the kiln head coal powder bin and kiln tail coal powder bin of most cement plants are under the large dust collector of the coal mill, while the kiln tail coal powder bin in this embodiment is arranged in the kiln tail tower, and the kiln head coal powder bin is arranged in the kiln head factory building.

[0075] In a preferred embodiment of the present invention, in step S2, the fineness of the coal powder entering the kiln tail coal powder pneumatic conveying pump 14 is measured by a coarse powder sampler 131, and according to the measured fineness, the operating parameters of the coal mill 3, the rotation speed of the coarse powder rotary feeder 9, and the opening and closing degree of the fine powder valve 12 are adjusted to control the ratio of coarse powder and fine powder entering the kiln tail coal powder pneumatic conveying pump 14; when the rotation speed of the coarse powder rotary feeder 9 and the opening and closing degree of the fine powder valve 12 are adjusted, the coarse powder in the coarse powder screw conveyor 7 passes through the coarse powder rotary feeder 9 and is mixed with the fine powder in the fine powder screw conveyor 8 controlled by the fine powder valve 12, and then enters the kiln tail coal powder pneumatic conveying pump 14.

[0076] In actual use, the ratio of coarse powder and fine powder entering the kiln tail coal powder pneumatic conveying pump 14 can be controlled by adjusting the operating parameters of the coal mill 3, or by adjusting the rotation speed of the coarse powder rotary feeder 9 and the opening degree of the fine powder valve 12 to control the ratio of coarse powder and fine powder entering the kiln tail coal powder pneumatic conveying pump 14.

[0077] In a preferred embodiment of the present invention, in step S2, the fineness of the coal powder entering the kiln head coal powder pneumatic conveying pump 15 is measured by the fine powder sampler 132, and according to the measured fineness, the operating parameters of the coal mill 3, the rotation speed of the fine powder rotary feeder 10, and the opening and closing degree of the coarse powder valve 11 are adjusted to control the ratio of coarse powder and fine powder entering the kiln head coal powder pneumatic conveying pump 15; when the rotation speed of the fine powder rotary feeder 10 and the opening and closing degree of the coarse powder valve 11 are adjusted, the fine powder in the fine powder screw conveyor 8 passes through the fine powder rotary feeder 10 and is mixed with the coarse powder in the coarse powder screw conveyor 7 controlled by the coarse powder valve 11, and the mixed powder enters the kiln head coal powder pneumatic conveying pump 15.

[0078] In actual use, the ratio of coarse powder and fine powder entering the kiln head coal powder pneumatic conveying pump 15 can be controlled by adjusting the operating parameters of the coal mill 3; the ratio of coarse powder and fine powder entering the kiln head coal powder pneumatic conveying pump 15 can also be controlled by adjusting the rotation speed of the fine powder rotary feeder 10 and the opening and closing degree of the coarse powder valve 11.

[0079] In a preferred embodiment of the present invention, in step S2, after the gas exiting the dust collector 5 is discharged through the exhaust fan 6, a portion of the gas is returned to the coal mill 3 as circulating air for recycling, and the rest of the gas is discharged through the chimney.

[0080] At present, conventional coal powder preparation, storage and transportation systems only collect coal powder through dust collectors or cyclones, and cannot achieve good separation of coarse powder and fine powder. Although some are equipped with two-stage cyclones, the efficiency of the second-stage cyclone is extremely low because the cyclone is less sensitive to fine powder. The two-stage cyclone only improves the separation efficiency of coal powder and gas, but cannot improve the classification rate of coarse powder and fine powder.

[0081] The present invention firstly arranges a set of cyclones between the coal mill and the dust collector to collect the coarse powder, and then uses the dust collector to collect the fine powder, so as to realize the graded collection of the coal powder and meet the functional requirements of the coarse powder entering the kiln tail and the fine powder entering the kiln head; at the same time, a variable frequency speed regulating rotary feeder is arranged at the discharge port of the screw conveyor, and the rotation speed of the coarse powder rotary feeder is adjusted and controlled to adjust the amount of the coarse powder entering the pneumatic conveying pump at the kiln tail, and the rotation speed of the fine powder rotary feeder is adjusted and controlled to adjust the amount of the fine powder entering the pneumatic conveying pump at the kiln head, so that the fineness of the coal powder at the kiln tail and the kiln head can be freely adjusted according to the combustion requirements of the system; in addition, a dividing valve is arranged at the outlet of the pneumatic conveying pump to realize the flexible switching of the coal powder conveying path. Through the above system and method, the combustion speed, burnout rate and flame temperature of the coal powder at the kiln head are improved, which helps to improve the thermal efficiency of the system and reduce coal consumption; avoid the crusting caused by the local temperature at the kiln tail being too high, and at the same time extend the combustion time and residence time of the coal powder. Combined with the self-denitrification design of the original system itself, the reaction time of CO and NOx is extended, the concentration of NOx is reduced, the self-denitrification effect of the system is enhanced, and the energy saving and environmental protection of the system are effectively improved.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A system for preparing, collecting and conveying energy-saving and environmentally friendly coal powder for cement kilns, characterized in that: It includes coal powder preparation system, coarse powder collection system and fine powder collection system; The coal powder preparation system comprises a coal mill (3), a cyclone (4) and a dust collector (5), wherein the coal mill (3), the cyclone (4) and the dust collector (5) are connected in sequence to form a coal powder preparation pipeline; The coarse powder collection system comprises a coarse powder screw conveyor (7), a coarse powder rotary feeder (9) and a kiln tail coal powder pneumatic conveying pump (14); the discharge port of the cyclone (4) is connected to the feed port of the coarse powder screw conveyor (7); the discharge port of the coarse powder screw conveyor (7), the coarse powder rotary feeder (9) and the kiln tail coal powder pneumatic conveying pump (14) are connected in sequence to form a coarse powder collection and conveying pipeline; The fine powder collection system comprises a fine powder screw conveyor (8), a fine powder rotary feeder (10) and a kiln-head coal powder pneumatic conveying pump (15); the discharge port of the dust collector (5) is connected to the feed port of the fine powder screw conveyor (8); the discharge port of the fine powder screw conveyor (8), the fine powder rotary feeder (10) and the kiln-head coal powder pneumatic conveying pump (15) are connected in sequence to form a fine powder collection and conveying pipeline; The air inlet of the coal powder pneumatic conveying pump (14) at the kiln tail and the air inlet of the coal powder pneumatic conveying pump (15) at the kiln head are respectively connected to Roots blowers.

2. The energy-saving and environment-friendly coal powder preparation, classification collection and transportation system for cement kilns according to claim 1 is characterized in that: The fineness of the coarse powder collected by the cyclone (4) is 15-20% of the 80 μm sieve residue, and the fineness of the fine powder collected by the dust collector (5) is less than 4% of the 80 μm sieve residue.

3. The energy-saving and environment-friendly coal powder preparation, classification collection and transportation system for cement kilns according to claim 1 is characterized in that: The powder selection efficiency of the cyclone (4) is 60%.

4. The energy-saving and environment-friendly pulverized coal preparation, classification collection and transportation system for cement kilns according to claim 1 is characterized in that: The feed inlet of the kiln tail coal powder pneumatic conveying pump (14) is provided with a coarse powder sampler (131) for measuring the fineness of the coal powder entering the kiln tail coal powder pneumatic conveying pump (14), and the feed inlet of the kiln head coal powder pneumatic conveying pump (15) is provided with a fine powder sampler (132) for measuring the fineness of the coal powder entering the kiln head coal powder pneumatic conveying pump (15).

5. The energy-saving and environment-friendly coal powder preparation, classification collection and transportation system for cement kiln according to claim 1 is characterized in that: The second discharge port of the coarse powder screw conveyor (7) is connected to the feed port of the kiln head coal powder pneumatic conveying pump (15) through the coarse powder valve (11), and the second discharge port of the fine powder screw conveyor (8) is connected to the feed port of the kiln tail coal powder pneumatic conveying pump (14) through the fine powder valve (12).

6. The energy-saving and environment-friendly coal powder preparation, classification collection and transportation system for cement kilns according to claim 1 is characterized in that: The kiln tail coal powder pneumatic conveying pump (14) is connected to the kiln tail coal powder bin and the kiln head coal powder bin respectively through a switching valve 1 (171); The kiln head coal powder pneumatic conveying pump (15) is respectively connected to the kiln head coal powder bin and the kiln tail coal powder bin via a second switching valve (172).

7. The energy-saving and environment-friendly coal powder preparation, classification collection and transportation system for cement kilns according to claim 1 is characterized in that: It also includes an inert gas fire extinguishing system (20), which is respectively connected to the raw coal bin (1), the coal mill (3), the cyclone (4), and the dust collector (5), and the discharge port of the raw coal bin (1) is connected to the feed port of the coal mill (3) via a quantitative feeder (2).

8. The energy-saving and environment-friendly coal powder preparation, classification collection and transportation system for cement kilns according to claim 1 is characterized in that: The air outlet of the dust collector (5) is connected to the air inlet of the exhaust fan (6), and the air outlet of the exhaust fan (6) is respectively connected to the chimney and the air inlet of the coal mill (3).

9. A method for preparing, collecting and conveying energy-saving and environment-friendly coal powder for cement kilns, characterized in that: include S1, the raw coal enters the coal mill (3) for pulverization, and the pulverized coal enters the cyclone (4) along with the gas discharged from the mill; S2, the coarse powder collected in the cyclone (4) enters the coarse powder screw conveyor (7), the fine powder out of the cyclone (4) enters the dust collector (5) along with the air flow, and the fine powder collected by the dust collector (5) enters the fine powder screw conveyor (8); The coarse powder in the coarse powder screw conveyor (7) passes through the coarse powder rotary feeder (9) and enters the coal powder pneumatic conveying pump (14) at the kiln tail end; the fine powder in the fine powder screw conveyor (8) passes through the fine powder rotary feeder (10) and enters the coal powder pneumatic conveying pump (15) at the kiln head end; S3. The pulverized coal entering the pneumatic conveying pump at the kiln tail and the pneumatic conveying pump at the kiln head are respectively powered by Roots blowers and pumped to the pulverized coal bin at the kiln tail and the pulverized coal bin at the kiln head to provide coal for combustion to the kiln tail and the kiln head.

10. The method for preparing, collecting and conveying energy-saving and environment-friendly pulverized coal for cement kiln according to claim 9, characterized in that: In step S2, the fineness of the coal powder entering the kiln tail coal powder pneumatic conveying pump (14) is measured by a coarse powder sampler (131), and the operating parameters of the coal mill (3), the rotation speed of the coarse powder rotary feeder (9), and the opening and closing degree of the fine powder valve (12) are adjusted according to the measured fineness to control the ratio of coarse powder to fine powder entering the kiln tail coal powder pneumatic conveying pump (14); When the rotation speed of the coarse powder rotary feeder (9) and the opening and closing degree of the fine powder valve (12) are adjusted, the coarse powder in the coarse powder screw conveyor (7) passes through the coarse powder rotary feeder (9) and is mixed with the fine powder in the fine powder screw conveyor (8) whose conveyance is controlled by the fine powder valve (12), and then enters the kiln tail coal powder pneumatic conveying pump (14) after mixing.

11. The method for preparing, collecting and conveying energy-saving and environment-friendly coal powder for cement kiln according to claim 9, characterized in that: In step S2, the fineness of the coal powder entering the kiln head coal powder pneumatic conveying pump (15) is measured by a fine powder sampler (132), and the operating parameters of the coal mill (3), the rotation speed of the fine powder rotary feeder (10), and the opening and closing degree of the coarse powder valve (11) are adjusted according to the measured fineness to control the ratio of coarse powder to fine powder entering the kiln head coal powder pneumatic conveying pump (15); When the rotation speed of the fine powder rotary feeder (10) and the opening and closing degree of the coarse powder valve (11) are adjusted, the fine powder in the fine powder screw conveyor (8) passes through the fine powder rotary feeder (10) and is mixed with the coarse powder in the coarse powder screw conveyor (7) whose conveyance is controlled by the coarse powder valve (11), and after being mixed, enters the kiln head coal powder pneumatic conveying pump (15).

12. The method for preparing, collecting and conveying energy-saving and environment-friendly pulverized coal for cement kiln according to claim 9, characterized in that: In step S2, after the gas exiting the dust collector (5) is discharged through the exhaust fan (6), a portion of the gas is returned to the coal mill (3) as circulating air for recycling, and the rest of the gas is discharged through the chimney.

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