Intelligent lime shaft kiln system

Abstract

The utility model discloses an intelligent lime shaft kiln system which comprises a shaft kiln body and an intelligent control system, the kiln body is divided into four functional zones including a preheating zone, a calcining zone I, a calcining zone II and a cooling zone, and a circle of surrounding air pipe is fixedly arranged outside the kiln body of each functional zone; a plurality of sub-air pipes are uniformly arranged on each layer of surrounding air pipe at intervals, each sub-air pipe is communicated with the interior of the kiln body, and a thermocouple is arranged at the position, corresponding to each sub-air pipe, of the kiln body; an air compressor and a gas storage tank are arranged on the smoke exhaust pipeline, an outlet of the gas storage tank is communicated with a smoke return pipeline, and the smoke return pipeline is respectively communicated with the four layers of surrounding air pipes through four smoke electric valves; an air supplement fan is further arranged outside the kiln body, an air outlet of the air supplement fan is connected with an air supplement pipeline, and the air supplement pipeline is communicated with the four layers of surrounding air pipes through four air supplement electric valves respectively. According to the utility model, the kiln condition adjusting capability and efficiency are improved.

Description

Technical Field

[0001] The utility model specifically relates to an intelligent lime shaft kiln system, belonging to the technical field of lime kilns. Background Art

[0002] The existing mixed-burning lime shaft kiln still mainly relies on manual on-site experience to judge the kiln condition and operate the kiln, which has large errors and high labor intensity. In addition, the reaction temperature in the lime kiln is high, various factors on site are complex, and the automation of the kiln is also in a local condition and low-level equipment stage. Secondly, it takes about 24 hours or even longer from the time the stone enters the kiln to the time it is calcined into lime and discharged from the kiln, which has a strong lag. Therefore, the kiln condition can only be adjusted based on the indicators after the lime is burned and discharged, but it is too late to adjust at this time. The lime kiln system is a large and complex system. Its production has highly nonlinear, multi-link, and strong coupling of multiple operating variables. Its calcination process is affected by multiple factors such as the performance of raw materials and fuel, temperature, pressure, air supply, and weather in the kiln. It has strong uncertainty in system dynamics and high dependence on control performance. It is necessary to adjust the kiln conditions in time. The existing adjustment methods mostly use the method of adjusting the combustion-supporting air and coal ratio, but this method has limited adjustment capacity. Common kiln condition fluctuations include the upward movement of the calcination zone, the downward movement of the calcination zone, the elongation of the calcination zone, the kiln bias, etc. The adjustment of the combustion-supporting air and coal ratio alone cannot meet the process production requirements. Summary of the invention

[0003] In view of the problems existing in the prior art, the utility model provides an intelligent vertical lime kiln system so as to give a rapid intelligent response to the fluctuation of the kiln condition of the lime kiln.

[0004] The technical solution of the utility model is as follows:

[0005] An intelligent vertical lime kiln system comprises a vertical kiln furnace body and an intelligent control system. The furnace body is divided into four functional zones from top to bottom, namely, a preheating zone, a calcining zone I, a calcining zone II and a cooling zone. The bottom of the furnace body is connected to a combustion-supporting fan through a combustion-supporting air duct. A flue gas duct is arranged on the top of the furnace body. The flue gas duct is connected to an exhaust gas treatment system through a smoke exhaust duct. A circle of surrounding air ducts is fixedly arranged outside the furnace body of each functional zone. There are four layers of surrounding air ducts in total. Multiple sub-air ducts are evenly spaced on each layer of surrounding air ducts. Each sub-air duct is connected to the inside of the furnace body. A thermocouple is arranged at the kiln body corresponding to each sub-air duct; an air compressor and a gas storage tank are arranged on the smoke exhaust duct, the outlet of the gas storage tank is connected with the smoke return duct, and the smoke return duct is connected with the four-layer surrounding air duct through four smoke electric valves; an air supply fan is also arranged outside the kiln body, and an air supply duct is connected to the air outlet of the air supply fan, and the air supply duct is connected with the four-layer surrounding air duct through four air supply electric valves; the thermocouple, smoke electric valve, air supply electric valve, air compressor, combustion-supporting fan and air supply fan are all electrically connected to the intelligent control system.

[0006] Furthermore, the number of thermocouples in each functional zone of the kiln body is 8, which are evenly spaced around the circumference of the kiln body.

[0007] Furthermore, two thermocouples are arranged on the top of the kiln body, two thermocouples are arranged on the flue gas duct, a thermocouple is arranged at the ash outlet at the bottom of the kiln body, and a thermocouple is arranged on the combustion-supporting air duct, and these thermocouples are electrically connected to the intelligent control system.

[0008] Furthermore, a pressure sensor is arranged on the top of the kiln body, and a wind pressure sensor and a flow sensor are arranged at the air outlet of the combustion-supporting fan. The pressure sensor, wind pressure sensor and flow sensor are all electrically connected to the intelligent control system.

[0009] Furthermore, an air inlet electric valve is provided on each sub-air duct, and the air inlet electric valve is electrically connected to the intelligent control system.

[0010] Furthermore, the intelligent control system includes a data acquisition system and a central processing system, and the central processing system includes a PLC and an industrial computer.

[0011] Beneficial effects: The utility model collects the temperature, pressure, flow and other parameters of the kiln through the data acquisition system to comprehensively judge the operating condition of the kiln, and the central processing system gives corresponding countermeasures. The smoke generated by the kiln can supply air to each layer of the surrounding air duct after passing through the air compressor to suppress the combustion of the corresponding functional area. The air supply fan can also supply air to each layer of the surrounding air duct to enhance combustion, and the two methods can be used at the same time, in conjunction with the frequency conversion control of the air compressor and the fan, the air volume adjustment, the opening adjustment of the electric valve, etc., which greatly improves the ability and efficiency of kiln condition adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the structure of the lime shaft kiln system.

[0013] Figure 2 for Figure 1 A partial enlargement of the middle part.

[0014] Figure 3 This is the structural block diagram of the intelligent control system.

[0015] Markings in the figure: 1 vertical kiln body, 2 flue gas duct, 3 exhaust gas duct, 4 pulse dust removal device, 5 chimney, 6 supply air fan, 7 combustion-supporting fan, 11 surround air duct, 12 tuyere brick, 13 air inlet electric valve, 14 thermocouple, 15 sub-air duct, 31 air compressor, 32 gas storage tank, 33 smoke return duct, 34 flue gas electric valve, 61 supply air duct, 62 supply air electric valve, 71 combustion-supporting air duct. DETAILED DESCRIPTION

[0016] The utility model is clearly and completely described below in conjunction with the accompanying drawings.

[0017] like Figure 1-3 As shown, an intelligent mixed-burning lime shaft kiln system for calcining lime includes a shaft kiln furnace body 1, a combustion-supporting fan 7, an air supply fan 6, an air compressor 31, a gas storage tank 32, an exhaust gas treatment system, a frequency converter and an intelligent control system, etc. The exhaust gas treatment system includes a pulse dust removal device 4 and a chimney 5, and the intelligent control system includes a data acquisition system and a central processing system, and the central processing system includes a PLC and an industrial computer, etc.

[0018] In the mixed-burning lime kiln, the kiln body 1 is divided into the preheating zone, calcination zone I, calcination zone II and cooling zone from top to bottom according to the functions, represented by A, B, C and D respectively in the figure. The data acquisition system is responsible for detecting the calcination status of the kiln. The data acquisition system includes temperature acquisition, pressure acquisition and flow acquisition.

[0019] 1. Temperature collection:

[0020] (1) Corresponding to the preheating zone, calcination zone I, calcination zone II and cooling zone, the kiln body is scientifically divided into four layers: A, B, C, and D (layer A is located in the preheating zone, layer B is located in the calcination zone I, layer C is located in the calcination zone II, and layer D is located in the cooling zone). Each layer is divided into 8 points in the circumferential direction (for example, layer A is divided into A East, A West, A South, A North, A Southeast, A Northwest, A Southwest, and A Northeast). The angle between each point is 45 degrees. A total of 32 K-type thermocouples 14 are set up on the four layers to measure the temperature, and the temperature of each point on each layer of the kiln body is collected in all directions;

[0021] (2) There are 4 K-type thermocouples for measuring the kiln roof temperature (2 points) and the flue gas temperature (2 points) to collect the kiln roof and flue gas temperatures;

[0022] (3) There are 3 PT100 type thermal resistance temperature measurement points, including 2 points for ash discharge temperature and 1 point for combustion air temperature, to accurately collect the finished lime temperature and combustion air temperature.

[0023] 2. Capacitive pressure transmitter is used to collect the kiln top pressure, which ensures the micro-negative pressure calcination in the furnace, saves fuel and improves the sealing effect of the furnace top.

[0024] 3. The pressure of the combustion-supporting fan is collected by a capacitive pressure transmitter. The pressure of the combustion-supporting fan reflects the resistance of the combustion-supporting air through the materials in the furnace and whether the calcining zone moves downward, etc. The combustion-supporting fan 4 adopts a Roots blower.

[0025] 4. The flow rate of the combustion-supporting fan is collected by using an orifice flow meter and a differential pressure transmitter, which are used in conjunction with the combustion-supporting fan frequency converter to accurately control the volume of the combustion-supporting air entering the furnace.

[0026] All temperature, pressure, flow and other parameters enter the central processing system, which is composed of Siemens 1200 series PLC, Advantech industrial computer, and WINCC software. The PLC analyzes and processes the temperature, pressure, and flow signals received from the site, and records the data in the WINCC software of the industrial computer to generate data curves, providing basic data for the adjustment of kiln conditions.

[0027] In the preheating zone, calcining zone I, calcining zone II and cooling zone of the kiln, a circle of surrounding air ducts 11 are arranged around the outer shell of the four zones of the kiln, which are respectively called the preheating zone air duct, the calcining zone I air duct, the calcining zone II air duct and the cooling zone air duct. Each layer of air duct is provided with 8 sub-air ducts 15 (the position corresponds to the position of the thermocouple 14) connected to the tuyere bricks 12 of the refractory part of the kiln. The tuyere bricks are connected with the materials in the kiln, and the outside wind can enter the kiln through the surrounding air ducts and tuyere bricks. The kiln is equipped with an air compressor 31, an air storage tank 32 and an air supply fan 6. The air supply fan is a centrifugal fan. The air compressor 31 is connected to the kiln roof exhaust duct 3, and can extract the kiln roof smoke and send it to the gas storage tank after pressurization. The gas tank outlet duct, i.e., the smoke return duct 33, is connected to the four-layer surrounding air duct 11, and each layer of the duct is equipped with a flue gas electric valve 34 with an adjustable opening of ￠200; the air supply fan outlet duct, i.e., the air supply duct 61, is also connected to the four-layer surrounding air duct, and each layer of the duct is also equipped with a air supply electric valve 62 with an adjustable opening of ￠200. By switching the electric valve, it can be switched whether the surrounding air ducts on each layer are fed with compressed kiln roof smoke or air drawn by the air supply fan. At the same time, the connecting pipes between each layer of surrounding air duct and tuyere bricks, i.e., the sub-air ducts, are equipped with electric air inlet valves 13 with an adjustable opening of ￠80. The amount of smoke (or air) entering the kiln top in this direction can be adjusted through the electric air inlet valves 13 with an opening of ￠80.

[0028] The combustion-supporting blower 7, i.e., the Roots blower, is responsible for supplying air from the bottom of the kiln body to the kiln through the combustion-supporting air duct 71, providing the oxygen required for the combustion of the limestone calcining fuel. The oxygen in the air is consumed during calcination, and the main components of the kiln top flue gas are the nitrogen remaining in the air after the oxygen is consumed, as well as the CO2 produced by the decomposition of limestone and the CO2 produced by the combustion of coal. Both nitrogen and CO2 have the effect of inhibiting combustion. Recycling the kiln top flue gas and injecting it back into the kiln has the effect of inhibiting fuel and reducing the temperature. This device uses an air compressor to extract the kiln top flue gas. The air compressor is frequency-controlled, and the amount of air extracted is adjustable. At the same time, the air compressor has a pressurizing effect, which can increase the pressure of the extracted kiln top flue gas. Re-injecting the pressurized flue gas into the kiln can quickly inhibit fuel combustion and play a cooling role, which is better than using an induced draft fan to extract flue gas.

[0029] When the kiln condition shows that the calcining zone is elongated and moved upward, and the preheating zone is reduced, the system automatically controls to open the ￠200 flue gas electric valve 34 of the A layer preheating zone surround air duct connected to the air compressor gas tank, and also opens the ￠80 air intake electric valves 13 in 8 directions of the A layer. The air compressor starts and flue gas is injected into the preheating zone in the kiln to suppress the combustion of the A layer and reduce the temperature of the preheating zone. At the same time, the temperature change detected by the thermocouple of the A layer adjusts the amount of flue gas injected into the kiln, shortens the length of the calcining zone, and solves the process problem of the calcining zone being elongated and moved upward.

[0030] Uneven burning is a common phenomenon in the process of calcining lime in lime kilns. It is also the most harmful to quality and difficult to adjust. When uneven burning occurs, this system first collects calcination data through the data acquisition system, enters the central processing system to analyze and obtain the direction of uneven burning, and compares the same layers. Taking layer B (corresponding to calcination zone I) as an example, assuming that the temperature in the south and southeast of layer B is lower than that in the other 6 directions, the system automatically opens the ￠200 electric valve on the air supply fan outlet duct and the calcination zone I air duct to allow the air drawn by the air supply fan to enter the surrounding air duct of layer B. At the same time, the ￠80 electric valves in the south and southeast of layer B are opened to supply air to the kiln separately. The air volume in these two directions increases, which is equivalent to the increase of oxygen, and the temperature of the direction will rise. By adjusting the opening of each electric valve, the temperature of the 8 directions of layer B can be uniform.

[0031] Assuming that the temperature in the south and southeast of layer B is higher than that in the other 6 directions, the system will automatically control the opening of the ￠200 flue gas electric valve on the pipeline between the air compressor gas storage tank and the calcination I zone air duct, so that the flue gas extracted by the air compressor can enter the surrounding air duct of layer B, and at the same time open the ￠80 electric valves in the south and southeast of layer B, and inject flue gas into the kiln from the south and southeast of layer B to suppress the combustion in that direction and reduce the temperature of layer B. The temperature of that direction will drop, and the temperature of the 8 directions of layer B can be uniformly achieved by adjusting the opening of each electric valve. This kind of biased kiln adjustment method can use flue gas to suppress the combustion in a certain direction and reduce the temperature in that direction, and can also use the air supply fan to supply air to a certain direction in the kiln to increase the temperature in that direction. Moreover, the two methods can be applied simultaneously, and the frequency conversion control of the air compressor and the air supply fan, the air volume adjustment, and the opening adjustment of the electric valve can greatly improve the ability and efficiency of kiln condition adjustment. The automatic adjustment methods of the kiln conditions of other A, C, and D layers are the same.

Claims

1. An intelligent lime shaft kiln system, comprising a shaft kiln body, the kiln body is divided into four functional zones from top to bottom according to function, namely, a preheating zone, a calcining zone I, a calcining zone II, and a cooling zone, characterized in that: A circle of surrounding air ducts is fixedly arranged outside the kiln body of each functional zone, with a total of four layers of surrounding air ducts. A plurality of sub-air ducts are evenly spaced on each layer of surrounding air ducts, and an air inlet electric valve is arranged on each sub-air duct. Each sub-air duct is communicated with the inside of the kiln body, and a thermocouple is arranged at the kiln body corresponding to each sub-air duct; an air compressor and a gas storage tank are arranged on the smoke exhaust duct of the kiln body, and the outlet of the gas storage tank is communicated with the smoke return duct, which is respectively communicated with the four layers of surrounding air ducts through four smoke electric valves.

2. The intelligent lime shaft kiln system according to claim 1, characterized in that: An air supply fan is also arranged outside the kiln body, and an air supply duct is connected to the air outlet of the air supply fan. The air supply duct is connected to the four layers of surrounding air ducts through four air supply electric valves.

3. The intelligent lime shaft kiln system according to claim 2, characterized in that: The vertical kiln system also includes an intelligent control system, and the thermocouple, flue gas electric valve, air supply electric valve, air inlet electric valve, air compressor, and air supply fan are all electrically connected to the intelligent control system.

4. The intelligent lime shaft kiln system according to claim 1, characterized in that: The number of thermocouples in each functional zone of the kiln body is 8, which are evenly spaced around the circumference of the kiln body.

5. The intelligent lime shaft kiln system according to claim 3, characterized in that: Two thermocouples are arranged on the top of the kiln body, two thermocouples are arranged on the flue gas duct at the top of the kiln body, a thermocouple is arranged at the ash outlet at the bottom of the kiln body, and a thermocouple is arranged on the combustion-supporting air duct at the bottom of the kiln. These thermocouples are electrically connected to the intelligent control system.

6. The intelligent lime shaft kiln system according to claim 3, characterized in that: A pressure sensor is arranged on the top of the kiln body, and a wind pressure sensor and a flow sensor are arranged at the air outlet of the combustion-supporting fan. The pressure sensor, the wind pressure sensor and the flow sensor are all electrically connected to the intelligent control system.

7. The intelligent lime shaft kiln system according to claim 3, characterized in that: The intelligent control system includes a data acquisition system and a central processing system, and the central processing system includes a PLC and an industrial computer.

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