阅读说明：本技术 多级悬浮预热水泥窑炉系统及其控制方法 (Multistage suspension preheating cement kiln system and control method thereof ) 是由 任强强 蔡军 吕清刚 于 2019-03-12 设计创作，主要内容包括：本发明涉及多级悬浮预热水泥窑炉系统,包括：回转窑,具有回转窑烟室；分解炉,与回转窑烟室连通；用于预热水泥生料的多级悬浮预热器,多级悬浮预热器至少包括末级旋风筒、次末级旋风筒及两者之间的换热管道,其中：来自分解炉的烟气通入末级旋风筒,且在多级悬浮预热器的上下两级旋风筒之间,下级旋风筒的出口烟气通过换热管道通入上级旋风筒；水泥生料输送管道,与多级悬浮预热器相通；和给煤装置,用于向系统供给煤粉,其中：至少一个换热管道上设有预热器给煤点；所述给煤装置适于通过所述预热器给煤点向多级悬浮预热器供给煤粉。本发明还涉及多级悬浮预热水泥窑炉系统的控制方法。(The invention relates to a multistage suspension preheating cement kiln system, which comprises: a rotary kiln having a rotary kiln smoke chamber; the decomposing furnace is communicated with the smoke chamber of the rotary kiln; multistage suspension preheater for preheating cement raw meal, multistage suspension preheater includes at least last stage cyclone, inferior last stage cyclone and the heat transfer pipeline between the two, wherein: the flue gas from the decomposing furnace is introduced into the last-stage cyclone, and between the upper and lower two-stage cyclones of the multi-stage suspension preheater, the outlet flue gas of the lower-stage cyclone is introduced into the upper-stage cyclone through a heat exchange pipeline; the cement raw material conveying pipeline is communicated with the multistage suspension preheater; and a coal feeding device for feeding pulverized coal to the system, wherein: a preheater coal feeding point is arranged on at least one heat exchange pipeline; the coal feeding device is suitable for feeding coal powder to the multistage suspension preheater through the preheater coal feeding point. The invention also relates to a control method of the multistage suspension preheating cement kiln system.)

1. A multi-stage suspension pre-heated cement kiln system, comprising:

a rotary kiln having a rotary kiln smoke chamber;

the decomposing furnace is communicated with the smoke chamber of the rotary kiln;

multistage suspension preheater for preheating cement raw meal, multistage suspension preheater includes at least last stage cyclone, inferior last stage cyclone and the heat transfer pipeline between the two, wherein: the flue gas from the decomposing furnace is introduced into the last-stage cyclone, and between the upper and lower two-stage cyclones of the multi-stage suspension preheater, the outlet flue gas of the lower-stage cyclone is introduced into the upper-stage cyclone through a heat exchange pipeline;

the cement raw material conveying pipeline is communicated with the multistage suspension preheater; and

the coal feeding device is used for supplying coal powder to the system;

wherein:

a preheater coal feeding point is arranged on at least one heat exchange pipeline;

the coal feeding device is suitable for feeding coal powder to the multistage suspension preheater through the preheater coal feeding point.

2. The cement kiln system according to claim 1, wherein:

the coal feeding device is also suitable for feeding coal powder to the decomposing furnace.

3. The cement kiln system according to claim 1, wherein:

the coal feeding point of the preheater is adjacent to the smoke outlet of the corresponding lower stage cyclone.

4. The cement kiln system according to claim 1, wherein:

the coal feeding point of the preheater is arranged on the heat exchange pipeline between the last-stage cyclone cylinder and the next-last-stage cyclone cylinder.

5. The cement kiln system according to claim 2, wherein:

the coal feeding amount added through the coal feeding point of the preheater is 5-50% of the total coal feeding amount added to the decomposing furnace and the heat exchange pipeline by the coal feeding device.

6. The cement kiln system according to claim 5, wherein:

the coal feeding amount added through the coal feeding point of the preheater is 20-30% of the total coal feeding amount added to the decomposing furnace and the heat exchange pipeline by the coal feeding device.

7. The cement kiln system according to claim 1, further comprising:

and the afterburning air supply device is used for supplying afterburning air to an outlet flue of the upper-level cyclone cylinder connected with the heat exchange pipeline provided with the preheater coal feeding point.

8. The cement kiln system according to any one of claims 1-7, further comprising:

and the cement raw material temperature adjusting pipeline is communicated with a corresponding heat exchange pipeline provided with a preheater coal feeding point.

9. The cement kiln system according to claim 8, wherein:

the cement raw material temperature adjusting pipeline is provided with a feeding adjusting device.

10. A control method of a multistage suspension preheating cement kiln system, the cement kiln system comprises the following steps: a rotary kiln having a rotary kiln smoke chamber; the decomposing furnace is communicated with the smoke chamber of the rotary kiln; multistage suspension preheater for preheating cement raw meal, the multistage suspension preheater at least comprises last stage cyclone and penultimate stage cyclone and heat exchange pipeline between the last stage cyclone and the penultimate stage cyclone, wherein: the flue gas from the decomposing furnace is introduced into the last-stage cyclone cylinder, and between the upper and lower two-stage cyclone cylinders of the multi-stage suspension preheater, the outlet flue gas of the lower stage cyclone cylinder is communicated to the upper stage cyclone cylinder through a heat exchange pipeline,

the method comprises the following steps:

and supplying coal powder to at least one heat exchange pipeline, wherein the coal powder entering the heat exchange pipeline is pyrolyzed or gasified in the heat exchange pipeline to form coal coke and coal gas.

11. The method of claim 10, wherein:

the supply of pulverized coal to at least one heat exchange tube comprises the steps of: and supplying pulverized coal to a heat exchange pipeline between the last-stage cyclone cylinder and the next last-stage cyclone cylinder.

12. The method of claim 10, wherein:

the coal feeding amount to the heat exchange pipeline is 5-50% of the total coal feeding amount added to the decomposing furnace and the heat exchange pipeline.

13. The method of claim 12, wherein:

the coal feeding amount to the heat exchange pipeline is 20-30% of the total coal feeding amount added to the decomposing furnace and the heat exchange pipeline.

14. The method of claim 10, further comprising the step of:

and supplying afterburning air to an outlet flue of an upper-level cyclone cylinder connected with a heat exchange pipeline for feeding coal.

15. The method according to any one of claims 10-14, further comprising the step of:

and introducing cement raw materials into the heat exchange pipeline of the coal supply to adjust the temperature change caused by the coal powder supply.

16. A control method of a multistage suspension preheating cement kiln system, the cement kiln system comprises the following steps: a rotary kiln having a rotary kiln smoke chamber; the decomposing furnace is communicated with the smoke chamber of the rotary kiln; multistage suspension preheater for preheating cement raw meal, multistage suspension preheater includes at least last stage cyclone, inferior last stage cyclone and the heat transfer pipeline between the two, wherein: the flue gas from the decomposing furnace is introduced into the last-stage cyclone cylinder, and between the upper and lower two-stage cyclone cylinders of the multi-stage suspension preheater, the outlet flue gas of the lower stage cyclone cylinder is communicated to the upper stage cyclone cylinder through a heat exchange pipeline,

the method comprises the following steps:

and supplying coal powder to at least one heat exchange pipeline to enable the upper-level cyclone cylinder corresponding to the heat exchange pipeline to be in reducing atmosphere.

Technical Field

The embodiment of the invention relates to the field of emission control of nitrogen oxides in cement industry, in particular to a multistage suspension preheating cement kiln system and a control method thereof.

Background

At present, the cement production process generally adopted at home and abroad is a novel dry cement production process, wherein a rotary kiln and a decomposing furnace are main equipment in the process link.

The rotary kiln is a cement clinker final firing device, and the gas-solid accumulation type heat transfer is adopted in the kiln, so that the heat transfer effect is achievedPoor results, the temperature of the calcining gas at the kiln head is as high as 1800 ℃ in order to obtain high-quality cement clinker, which causes the thermal NO of the rotary kiln_xThe emission is extremely high, and the fuel occupies all thermal NO_xMore than 80% of the discharge. Furthermore, in view of the characteristics of the high-temperature calcination process of the rotary kiln, the partial thermal NO_xThe generation of (a) cannot be avoided.

The decomposing furnace is a cement raw material decomposing device, the cement raw material is decomposed in the decomposing furnace and needs to absorb a large amount of heat, and the heat is provided by the combustion of pulverized coal, so that the coal supply amount required by the combustion in the decomposing furnace is higher than that required by the combustion of the rotary kiln (accounting for about 60 percent of all the coal supply amount), and the fuel type NO in the decomposing furnace is enabled to be_xThe discharge is high.

The rotary kiln and the decomposing furnace are the prior novel dry cement production process NO_xTwo major sources of emissions contribute to the overall NO of the cement kiln_xThe emissions are at a higher level, the original emissions exceeding 1000mg/Nm³. Statistical data show that NO in 2017 years in cement industry_xThe emission accounts for national NO_x10-12% of the total emission is one of the important causes of haze weather in China, and the atmospheric environment and human health are seriously harmed. Therefore, the low NO of the cement kiln is realized_xThe emission has important strategic significance for the atmospheric pollution control.

NO for cement industry of China_xEmission Standard (GB4915-2013) stipulated, NO in important areas_xEmission control level not higher than 320mg/Nm³In general, the concentration of the carbon dioxide is not higher than 400mg/Nm³Some local provinces and cities even put forward higher emission standards. For example, Jiangsu province regulates NO in cement industry 6 months and 1 day before 2019_xThe discharge cannot be higher than 100mg/Nm³(ii) a Before 2018 and 10 months of Henan province, the modified cement enterprises have NO under the condition that the reference oxygen content is 10%_xConcentration not higher than 150mg/Nm³。

In order to meet increasingly stringent emission standards, most cement enterprises have to adopt selective non-catalytic reduction (SNCR) denitration technology at the tail part of a decomposing furnace at present, namely ammonia water is used as a reducing agent to reduce NO_xThis not only adds additional cost to the cement, but also has ammonia slipTherefore, new environmental pollution problems are brought about.

In addition to SNCR technology, the fuel/air staged combustion technology of the decomposing furnace has been regarded by cement companies. The staged combustion technology is to distribute pulverized coal fuel or air for fuel combustion for a decomposing furnace in a staged and multi-point manner, so as to create a reducing atmosphere region as much as possible under the condition of ensuring the fuel combustion efficiency, and reduce NO on one hand_xOn the other hand, NO from the kiln tail gas chamber_xReduction to N₂To achieve NO_xAnd (4) the purpose of emission reduction.

However, since different cement decomposing furnaces have great differences in structure, the adopted staged combustion scheme is often uniform and does not change or adjust correspondingly according to the furnace type, and the inherent defects of the existing staged combustion technology result in that the staged combustion concept has been proposed for many years, but in the cement production, the actual NO is_xThe emission reduction effect is not ideal, and sometimes the effect is not even achieved.

Staged combustion is the more economical NO for dry cement production processes_xThe method for reducing emission, but the traditional fuel/air staged combustion technical concept is still limited to a decomposing furnace body (an upper cone, a middle cone or a lower cone) and a connecting smoke chamber or a flue space between the decomposing furnace body and a rotary kiln, and the NO is realized by constructing a reducing atmosphere by creating an anoxic combustion area_xAnd (4) reducing.

The traditional fuel/air staged combustion technology mainly has the following technical defects from the technical characteristics:

(1) the fuels are classified downwards (in a kiln tail smoke chamber), although the reduction time can be prolonged, the risk that coal dust is deposited and falls into the tail part of the rotary kiln together with cement raw materials exists, the falling coal dust is combusted in the rotary kiln, so that the local temperature is overhigh, the cement raw materials are skinned and bonded, the quality of cement clinker is reduced, even the rotary kiln is out of order, and huge production stop loss is caused.

(2) The fuel is graded upwards (the upper part of the decomposing furnace), although the reducing area can be built for many times, the pulverized coal is easy to be burnt incompletely because the retention time of the pulverized coal is not enough, and the combustion efficiency is influenced, thereby increasing the heat consumption of the whole cement production process system. In addition, unburned coal dust particles are most likely to be collected by the outlet cyclone of the decomposing furnace and enter the tail part of the rotary kiln, so that the problems of high-temperature skinning and bonding of cement raw materials and even kiln shutdown are caused.

Disclosure of Invention

The present invention has been made to mitigate or solve at least one aspect or at least one point of the above-mentioned problems.

According to an aspect of an embodiment of the present invention, there is provided a multistage suspension preheating cement kiln system, including:

a rotary kiln having a rotary kiln smoke chamber;

the decomposing furnace is communicated with the smoke chamber of the rotary kiln;

multistage suspension preheater for preheating cement raw meal, multistage suspension preheater includes at least last stage cyclone, inferior last stage cyclone and the heat transfer pipeline between the two, wherein: the flue gas from the decomposing furnace is introduced into the last-stage cyclone, and between the upper and lower two-stage cyclones of the multi-stage suspension preheater, the outlet flue gas of the lower-stage cyclone is introduced into the upper-stage cyclone through a heat exchange pipeline;

the cement raw material conveying pipeline is communicated with the multistage suspension preheater; and

the coal feeding device is used for supplying coal powder to the system;

wherein:

a preheater coal feeding point is arranged on at least one heat exchange pipeline;

the coal feeding device is suitable for feeding coal powder to the multistage suspension preheater through the preheater coal feeding point.

Optionally, the coal feeding device is further adapted to feed pulverized coal to the decomposing furnace.

Optionally, the coal feeding point of the preheater is adjacent to the flue gas outlet of the lower stage cyclone.

Optionally, the preheater coal feeding point is arranged on the heat exchange pipeline between the last stage cyclone and the next last stage cyclone.

Optionally, the coal feeding amount added through the coal feeding point of the preheater is 5% -50% of the total coal feeding amount added to the decomposing furnace and the heat exchange pipeline by the coal feeding device;

optionally, the coal feeding amount added through the coal feeding point of the preheater is 20% -30% of the total coal feeding amount added to the decomposing furnace and the heat exchange pipeline by the coal feeding device.

Optionally, the cement kiln system further comprises a post-combustion air supply device for supplying post-combustion air to an outlet flue of a corresponding upper-stage cyclone connected to the heat exchange pipeline provided with the preheater coal feeding point. The afterburning air is used for burning out coal gas generated by pyrolysis or gasification of coal powder in the cyclone cylinder communicating pipeline, so that the coal consumption of the system is reduced.

Optionally, the cement kiln system further comprises a cement raw material temperature adjusting pipeline communicated with a corresponding heat exchange pipeline provided with a preheater coal feeding point. Further optionally, the cement raw material temperature adjusting pipeline is provided with a feeding adjusting device.

The embodiment of the invention also relates to a control method of the multistage suspension preheating cement kiln system,

the cement kiln system comprises: a rotary kiln having a rotary kiln smoke chamber; the decomposing furnace is communicated with the smoke chamber of the rotary kiln; multistage suspension preheater for preheating cement raw meal, the multistage suspension preheater at least comprises last stage cyclone and penultimate stage cyclone and heat exchange pipeline between the last stage cyclone and the penultimate stage cyclone, wherein: the flue gas from the decomposing furnace is introduced into the last-stage cyclone cylinder, and between the upper and lower two-stage cyclone cylinders of the multi-stage suspension preheater, the outlet flue gas of the lower stage cyclone cylinder is communicated to the upper stage cyclone cylinder through a heat exchange pipeline,

the method comprises the following steps:

and supplying coal powder to at least one heat exchange pipeline, wherein the coal powder entering the heat exchange pipeline is pyrolyzed or gasified in the heat exchange pipeline to form coal coke and coal gas.

Optionally, the supplying of pulverized coal to the at least one heat exchange tube comprises the steps of: and supplying pulverized coal to a heat exchange pipeline between the last-stage cyclone cylinder and the next last-stage cyclone cylinder.

Optionally, the coal feeding amount to the heat exchange pipeline is 5% -50% of the total coal feeding amount added to the decomposing furnace and the heat exchange pipeline;

optionally, the coal feeding amount to the heat exchange pipeline is 20% -30% of the total coal feeding amount added to the decomposing furnace and the heat exchange pipeline.

Optionally, the method further comprises the steps of: and supplying afterburning air to an outlet flue of the corresponding upper-level cyclone cylinder connected with the heat exchange pipeline for feeding coal. The afterburning air is used for burning out coal gas generated by pyrolysis or gasification of coal powder in the cyclone cylinder communicating pipeline, so that the coal consumption of the system is reduced. Further, the method further comprises the steps of: and introducing cement raw materials into the heat exchange pipeline of the coal supply to adjust the temperature change caused by the coal powder supply.

The embodiment of the invention also relates to a control method of the multistage suspension preheating cement kiln system,

the cement kiln system comprises: a rotary kiln having a rotary kiln smoke chamber; the decomposing furnace is communicated with the smoke chamber of the rotary kiln; multistage suspension preheater for preheating cement raw meal, multistage suspension preheater includes at least last stage cyclone, inferior last stage cyclone and the heat transfer pipeline between the two, wherein: the flue gas from the decomposing furnace is introduced into the last-stage cyclone cylinder, and between the upper and lower two-stage cyclone cylinders of the multi-stage suspension preheater, the outlet flue gas of the lower stage cyclone cylinder is communicated to the upper stage cyclone cylinder through a heat exchange pipeline,

the method comprises the following steps:

and supplying coal powder to at least one heat exchange pipeline to enable the upper-level cyclone cylinder corresponding to the heat exchange pipeline to be in reducing atmosphere.

Drawings

Fig. 1 is a schematic view of a multistage suspension preheated cement kiln system according to an exemplary embodiment of the present invention.

Fig. 2 is a schematic view of a multistage suspension preheated cement kiln system according to another exemplary embodiment of the present invention.

Detailed Description

The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the general inventive concept of the present invention and should not be construed as limiting the invention.

Fig. 1 is a schematic view of a multistage suspension preheated cement kiln system according to an exemplary embodiment of the present invention. As shown in fig. 1, a multistage suspension preheating cement kiln system includes:

a rotary kiln 10 having a rotary kiln smoke chamber 20;

a decomposing furnace 30 communicated with the rotary kiln smoke chamber 20;

a multistage suspension preheater for preheating cement raw meal, comprising at least a last stage cyclone 41, a penultimate stage cyclone 42 and a heat exchange duct L1 therebetween. The example of FIG. 1 includes 5 stages of cyclones 41-45, with two primary cyclones 45. The flue gas from the decomposing furnace 30 is introduced into the last stage cyclone 41 (five stage cyclone), and the outlet flue gas is introduced into the second last stage cyclone 42 (four stage cyclone) through a heat exchange pipeline L1; the outlet flue gas discharged from the top of the cyclone cylinder 42 is introduced into the 3 rd stage cyclone cylinder 43 through a heat exchange pipeline L2, and the preheated raw meal discharged from the cyclone cylinder 43 is introduced into the L1 through a discharge pipe; the outlet flue gas of the cyclone 43 is introduced into the cyclone 44 through L3, and the discharge pipe of the cyclone 44 is communicated with L2, and the other same is true. The cement raw material conveying pipe L6 is connected to the primary cyclone 45.

At least one heat exchange pipeline is provided with a preheater coal feeding point (such as a preheater coal feeding point 411 in the figure), and the coal feeding device 50 feeds coal powder to the multi-stage cyclone preheater through the preheater coal feeding point.

Optionally, the coal feeder 50 also feeds pulverized coal to the decomposition furnace through a coal feeding point on the decomposition furnace 31.

In the present invention, the cyclone that enters first from the cement raw material conveying pipe is the primary cyclone. The number of the primary cyclones can be one or a plurality of the primary cyclones arranged in parallel.

In the invention, the upper stage and the lower stage of the cyclone cylinder in the multistage suspension preheater are opposite to the flow direction of flue gas: the downstream of the smoke flowing direction is an upper stage cyclone, the upstream is a lower stage cyclone, the most upstream cyclone in the smoke flowing direction is a last stage cyclone, and the downstream cyclone in the last stage cyclone is a next last stage cyclone.

Preferably, the specific location of the coal feed point of the preheater on the specific heat exchange duct is adjacent to the flue gas outlet of the corresponding lower stage cyclone, and relatively far away from the inlet of the upper stage cyclone, such as the coal feed point 411 of the preheater shown in fig. 1 adjacent to the flue gas outlet of the cyclone 41 and far away from the cyclone 42. Therefore, the coal powder stays in the heat exchange pipeline for a longer time, and the preheating is more sufficient.

In the example shown in FIG. 1, the preheater coal feed point 411 is located on the heat exchange duct L1 between the last stage cyclone 41 and the next to last stage cyclone 42. It should be noted that the coal feeding point of the preheater is not limited to be arranged on the flue gas outlet heat exchange pipeline of the last stage cyclone, and the coal feeding point of the preheater may be arranged on the outlet heat exchange pipeline of the second stage cyclone 44, the third stage cyclone 43 or the fourth stage cyclone (the second last stage cyclone) 42 as long as the temperature is proper. In addition, under the condition of temperature allowance, the coal feeding point of the preheater is not limited to single-point coal feeding, and a plurality of coal feeding points of the preheater can be simultaneously arranged on the heat exchange pipeline (except the primary cyclone 45) at the flue gas outlet of each stage of cyclone to form combined high-position coal feeding and multistage reinforced NO_xAnd (4) reducing.

Optionally, the coal feeding amount of the coal feeding device to the heat exchange pipeline is 5% to 50% of the total coal feeding amount of the coal feeding device to the decomposing furnace and the heat exchange pipeline, for example, 5%, 15%, 35%, 50%; in a further embodiment, the coal feeding device feeds coal to the heat exchange pipeline in an amount of 20% to 30%, for example 20%, 25% or 30%, of the total coal feeding amount of the coal feeding device to the decomposing furnace and the heat exchange pipeline.

As shown in fig. 1, the cement kiln system may further include a post-combustion air introduction port 421 disposed at an outlet of the cyclone 42 for supplying post-combustion air to an outlet heat exchange duct of a corresponding upper stage cyclone 42 connected to a coal feeding heat exchange duct L1. The afterburning air is used for burning out coal gas generated by pyrolysis or gasification of coal dust in the heat exchange pipeline L1, so that the coal consumption of the system is reduced.

As can be appreciated by those skilled in the art, in the event of a change in the point of feed to the heat exchange tubes, the location of the post-combustion air is changed accordingly.

Referring now to FIG. 1, a detailed description of NO reduction in a multi-stage suspension preheated cement kiln system according to an embodiment of the present invention is provided_xAnd (5) carrying out discharging.

The coal feeding of the whole system except the rotary kiln is divided into two parts, one part is fed from a coal feeding point 31 of the decomposing furnace on a cone at the bottom of the decomposing furnace, and the other part is fed from a coal feeding point 411 of a preheater on an outlet heat exchange pipeline L1 of a five-stage cyclone (a last-stage cyclone) 41. The tertiary air is fed from a tertiary air port 32 and a tertiary air port 33 on the decomposing furnace to ensure the burnout of the coal feeding of the decomposing furnace, wherein the tertiary air port 32 is positioned above the coal feeding point 31 of the decomposing furnace and on a straight barrel section of the decomposing furnace, and the tertiary air port 33 is positioned near the upper part of a spouting shrinkage port in the decomposing furnace so as to strengthen gas-solid mixing through a spouting effect. High NO from rotary kiln 10_xThe concentration kiln gas enters the bottom of the decomposing furnace 30 through the smoke chamber 20, the smoke and the coal dust particles are fully mixed through the spouting effect generated by the bottom necking, the coal dust particles are simultaneously preheated to form high-temperature coke and coal gas with the reducing effect, the area between the bottom of the decomposing furnace and the tertiary air port 32 is a strong reducing area, and NO in the kiln gas_xIs reduced. The region between the tertiary tuyere 32 and the tertiary tuyere 33 is a weakly reducing region, NO_xThe reduction strength of (a) is weakened. The region above the tertiary tuyere 33 is an oxidizing region, NO_xThe reduction is eliminated, and the flue gas still contains a large amount of NO which is not reduced and/or generated by combustion of the decomposing furnace_x. After the flue gas comes out of the five-stage cyclone 41, the flue gas still has high temperature of about 850 ℃, for example, the pulverized coal fed by the coal feeding point 411 of the preheater is preheated, and coke and coal gas formed by pulverized coal pyrolysis or gasification form strong reducing atmosphere in the heat exchange pipeline L1 and the inner area of the four-stage cyclone 42, so that NO in the flue gas is treated_xAnd carrying out reduction again. The four-stage cyclone cylinder 42 can prolong the contact time of the flue gas and the reducing coke/coal gas, thereby greatly improving NO_xAnd (4) reducing efficiency. Coal gas which does not participate in the reduction reaction flows out from the outlet of the four-stage cyclone cylinder 42 along with the flue gas, a post-combustion air inlet position 421 is arranged on the heat exchange pipeline at the outlet of the four-stage cyclone cylinder 42, and the residual coal gas is combusted at the position. The high-temperature coal coke is separated by the four-stage cyclone cylinder 42 and returns to the decomposing furnace together with the cement raw meal to be combusted, thereby providing heat for the endothermic decomposition reaction of the cement raw meal.

Based on the above, in an alternative embodiment, as shown in fig. 1, the lower outlet of the penultimate cyclone 42 communicates with the decomposing furnace 30; and the lower outlet of the last stage cyclone 41 communicates with the rotary kiln 10.

It should be noted that the position of the coal feeding point 31 of the decomposing furnace can be adjusted, and is not limited to single-point coal feeding, and the tertiary air is not limited to single-point air distribution, and the distribution point number and position of the tertiary air can be adjusted accordingly according to the number and position of the specific coal feeding points of the decomposing furnace, so as to ensure the fuel burn-out and reduce the coal consumption of the system.

Based on the above, in an alternative embodiment, the cement kiln system according to the present invention may further include: a tertiary tuyere arranged on the decomposing furnace; and a tertiary air supply control device adapted to control the amount of tertiary air to form a reducing atmosphere below the tertiary air port and a non-reducing atmosphere above the tertiary air port. Further, the tertiary air ports comprise a first tertiary air port and a second tertiary air port which are arranged on the decomposing furnace at intervals in the vertical direction; and the tertiary air supply control device is suitable for controlling the air quantity of tertiary air so as to form a first reducing atmosphere between the bottom of the decomposing furnace and the first tertiary air port, form a second reducing atmosphere which is weaker than the first reducing atmosphere between the first tertiary air port and the second tertiary air port, and form a non-reducing atmosphere above the second tertiary air port.

Based on the above, the embodiment of the present invention also provides a control method of the above multistage suspension preheating cement kiln system, including the steps of: and supplying coal powder to at least one heat exchange pipeline, wherein the coal powder entering the heat exchange pipeline is pyrolyzed or gasified in the heat exchange pipeline to form coal coke and coal gas.

Optionally, the supplying of pulverized coal to the at least one heat exchange tube comprises the steps of: and supplying coal powder to a coal supply point of the heat exchange pipeline corresponding to the smoke outlet of the lower stage cyclone cylinder.

Optionally, the supplying of pulverized coal to the at least one heat exchange tube comprises the steps of: and supplying pulverized coal to a heat exchange pipeline between the last-stage cyclone cylinder and the next last-stage cyclone cylinder.

Optionally, the coal supply amount to the heat exchange pipeline is 5% -50% of the total coal supply amount to the decomposing furnace and the heat exchange pipeline; in a further embodiment, the amount of coal fed to the heat exchange tubes is 20-30% of the total amount of coal fed to the decomposition furnace and the heat exchange tubes.

Optionally, the method further comprises the steps of: and supplying afterburning air to an outlet flue of an upper-level cyclone connected with a heat exchange pipeline of the fed coal.

Embodiments of the present invention also relate to a method for controlling a multistage suspension pre-heating cement kiln system, the cement kiln system comprising: a rotary kiln; the decomposing furnace is communicated with the smoke chamber of the rotary kiln; multistage suspension preheater for preheating cement raw meal, multistage suspension preheater includes at least last stage cyclone, inferior last stage cyclone and the heat transfer pipeline between the two, wherein: the flue gas from the decomposing furnace is introduced into a last-stage cyclone, and the flue gas at the outlet of a lower-stage cyclone is introduced into an upper-stage cyclone through a heat exchange pipeline between an upper-stage cyclone and a lower-stage cyclone of a multi-stage suspension preheater, wherein the method comprises the following steps: and supplying coal powder to at least one heat exchange pipeline to enable the upper-level cyclone cylinder corresponding to the heat exchange pipeline to be in reducing atmosphere.

Fig. 2 is a schematic diagram of an exemplary embodiment of a multistage suspension preheating cement kiln system with temperature regulation according to the present invention. As shown in fig. 2, a multistage suspension preheated cement kiln system with temperature regulation, in addition to having the features of the embodiment shown in fig. 1, further comprises:

a three-way pipe 71 for distributing cement raw material, the three-way pipe 71 having a first outlet and a second outlet;

a cement raw material temperature adjusting pipeline L5 for transporting cement raw material participating in temperature adjustment, one end of which is communicated with the first outlet and the other end of which is connected to a heat exchange pipeline L1 after the coal feeding point of the preheater at the outlet of the last stage cyclone 41, and the cement raw material temperature adjusting pipeline L5 is provided with a gate valve 72 for controlling the flow rate of cement raw material participating in temperature adjustment and an air lock valve 73 for sealing the system; and

the cement raw material conveying pipeline L6, in an alternative embodiment, has one end connected to the second outlet of the pipeline tee 71 and the other end connected to the preheated flue gas communication pipeline L4 at the outlet of the secondary cyclone 44.

Because the pipeline L1 is in a negative pressure state, the pipeline L5 needs to be prevented from entering air, and the air locking valve is a valve which can be automatically opened after a certain weight is reached and closed when the weight is less than the certain weight, so that the sealing of the system is ensured. The airlock feeding is microscopically intermittent, but macroscopically can be considered continuous (step feeding with short time intervals). Besides the air lock valve, other sealing devices for maintaining the negative pressure state can be adopted, and the invention is within the protection scope of the invention.

In fig. 2, the gate valve 72 and the latch valve 73 are provided separately, but they may be provided integrally.

The connection point of the cement raw material temperature adjusting pipeline L5 and the heat exchange pipeline L1 at the outlet of the last stage cyclone 41 is after the coal feeding point 411 of the preheater (downstream determined by the flow direction of flue gas) and is closer to the upper stage cyclone than the coal feeding point of the preheater.

Based on the above, the embodiment of the invention also provides a temperature control method of a multistage suspension preheating cement kiln system, which comprises the following steps: supplying coal powder to at least one heat exchange pipeline, wherein the coal powder entering the heat exchange pipeline is pyrolyzed or gasified in the heat exchange pipeline to form coal coke and coal gas; and (3) introducing cement raw materials into the coal coke and the coal gas formed by pyrolysis or gasification to participate in temperature control.

A temperature control method of the multistage suspension preheating cement kiln system according to an embodiment of the present invention will be described in detail with reference to fig. 2. In the example shown in fig. 2, the three-way pipe 71 divides the normal temperature cement raw meal conveyed by the elevator into two paths, one path of the cement raw meal enters the outlet heat exchange pipe L4 of the cyclone separator 44 through the cement raw meal conveying pipe L6, and is heated by the flue gas and then carried into the cyclone separator 45; the other path of cement raw meal passes through the gate valve 72 and the airlock valve 73 in sequence through a cement raw meal temperature adjusting pipeline L5, and enters an outlet heat exchange pipeline L1 of the cyclone 41, and the specific feeding position is downstream of the coal feeding point 411 of the preheater. Since the heat exchange pipeline L1 is in a negative pressure state, the air lock valve 73 is arranged on the cement raw material temperature adjusting pipeline L5, and air leakage is prevented from entering the heat exchange pipeline L1. In the actual cement process, the flue gas at the outlet of the cyclone 41 contains certain oxygen, and after the coal powder is fed from the coal feeding point 411 of the preheater, part of the coal powder is combusted, so that the temperature of the flue gas rises, and after normal-temperature cement raw materials are fed, the temperature of the flue gas can be effectively reduced, and the phenomenon that the preheating system is skinned due to over-temperature (generally, the skinning phenomenon easily occurs when the temperature of the cement raw materials exceeds 1000 ℃) is avoided. The flow of cement raw materials participating in temperature regulation can be adjusted by controlling the opening degree of the gate valve 72, so that the temperature of the flue gas can be reasonably regulated and controlled. The cement raw materials participating in the temperature adjustment are merged with the cement raw materials collected by the cyclone 43, and then enter the cyclone 42, and finally enter the decomposing furnace 30.

It is to be noted that, although the expression coal feeding device is used in the present invention, as can be understood by those skilled in the art, the coal feeding device may feed other fuels capable of achieving the technical purpose, such as biomass fuel, which are within the protection scope of the present invention.

In the invention, the NO is reduced by arranging a preheater coal feeding point on the flue gas outlet pipeline of the cyclone_xThe method has the advantages of simple discharge principle, easy implementation, small influence on the existing cement production process and low modification cost.

In the invention, the concept of high-level fuel classification is adopted, the traditional fuel classification combustion technology is replaced by a method of feeding coal in a smoke chamber, and the risk that pulverized coal particles fall into the tail part of the rotary kiln to cause over-temperature skinning in the local area of the rotary kiln is avoided.

In addition, in the invention, the pulverized coal fed into the multistage suspension preheater can finally return to the decomposing furnace for combustion, so that heat is provided for the decomposition of cement raw meal, and the problem of incomplete combustion of the pulverized coal caused by upward grading of fuel is avoided. Therefore, the invention realizes NO in the flue gas_xWhile the efficient reduction is carried out, the coal consumption (heat consumption) of the system is not obviously increased, and the operation cost is effectively controlled.

Although embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments and combinations of elements without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.