Multi-stage precise ammonia spraying and denitration integrated system of cement kiln

Abstract

The utility model relates to a multi-stage precise ammonia spraying and denitration integrated system of a cement kiln. The multi-stage precise ammonia spraying and denitration integrated system comprises a rotary kiln head, a rotary kiln, a rotary kiln tail smoke chamber and a kiln tail decomposing furnace which are connected in sequence, the C5 preheating furnace is connected with a smoke chamber at the tail of the rotary kiln, the C5 preheating furnace is sequentially connected with a C4 preheating furnace, a C3 preheating furnace, a C2 preheating furnace and a C1 preheating furnace, a plurality of combustion temperature measuring points and carbon monoxide measuring points are arranged around the core position of nitrogen oxide generation and emission in the C5 preheating furnace, and a first ammonia spraying site is arranged at the position, close to a flue, of the upper half part of a furnace body of the C5 preheating furnace. And a second ammonia spraying site is arranged in an outlet flue of the C5 preheating furnace. According to the multi-stage ammonia spraying device, the spraying amount of a denitration reducing agent is flexibly adjusted according to flue gas conditions fed back by measuring points through the multi-stage ammonia spraying sites and the matched ammonia spraying adjusting device, so that the reaction is carried out in the most efficient interval, the denitration efficiency is improved, and the denitration operation cost is reduced. The utility model is particularly suitable for simply transforming the existing equipment to realize the best environment-friendly effect.

Description

Technical Field

[0001] The utility model relates to a multi-stage precise ammonia spraying and denitrification integrated system for a cement kiln, which is an environmental protection system and is an environmental protection system used for purifying flue gas in a cement kiln. Background Art

[0002] The existing low nitrogen burners in cement kilns have the following disadvantages:

[0003] 1. The problem of low-nitrogen burners being difficult to adapt to the complex operating conditions of cement kilns. As the country's environmental protection requirements are repeatedly raised, the cement industry, as the final application of the comprehensive utilization of various solid wastes, generally begins to blend solid pollutants. This makes the combustion conditions of cement kilns significantly different from before. Low-nitrogen burners are designed according to the equipment processing and combustion conditions when the cement kiln is designed. The low-nitrogen combustion effect will also fluctuate after blending.

[0004] 2. A more flexible denitrification ammonia injection system is very important.

[0005] 3. SCR denitrification technology greatly increases the operating cost of flue gas denitrification. As the core of SCR denitrification technology, once the denitrification catalyst is poisoned or blocked, the denitrification efficiency will be significantly reduced. A major feature of cement kiln denitrification flue gas is that the concentration of particulate matter in the flue gas is very high, much higher than that in the thermal power generation industry. Therefore, the loss of denitrification catalyst will seriously increase the cost of the denitrification reaction.

[0006] 4. Excessive injection of denitrification reducing agent will increase the ammonia escape at the outlet. In the existing denitrification reaction system combining low-nitrogen burner + SNCR + SCR, the front end of the SNCR system and the front end of the SCR system are usually sprayed with a 20% concentration of ammonia water. The spray gun is usually set with a higher flow rate, and the point source injection often causes uneven mixing of the reducing agent in the flue gas. In order to ensure the denitrification efficiency, cement kilns generally have the problem of excessive ammonia spraying.

[0007] 5. The lag of pollutant concentration in adjusting the front-end ammonia injection system. The flue gas system of cement kiln is a relatively complex system with a long process. Generally, the flue gas outlet of cement kiln preheating furnace is equipped with waste heat recovery system, high-temperature fan, drying circulating air system, circulating fan, dust removal system, tail exhaust fan, etc. The ammonia injection of denitrification system is generally set after C5 at the front end of the preheating furnace, which is very long from the final pollutant emission point. When the increase of nitrogen oxide concentration is detected at the emission chimney, there is a certain lag in returning to adjust the ammonia injection amount.

[0008] How to improve the efficiency of ammonia injection and achieve ultra-low emission indicators of flue gas NOx through simple modification of existing equipment is a problem that needs to be solved. Summary of the invention

[0009] In order to overcome the problems of the prior art, the utility model proposes a cement kiln multi-stage precise ammonia injection denitrification integrated system. The system achieves ultra-low emission of flue gas NOx by increasing the setting of ammonia injection points, intelligently detecting and interlocking kiln combustion conditions, and integrating multiple control systems such as denitrification outlet pollutant concentration feedback through nitrogen oxide emission detection.

[0010] The purpose of the utility model is achieved as follows: a multi-stage precise ammonia injection denitrification integrated system for a cement kiln, comprising: a rotary kiln head, a rotary kiln, a rotary kiln tail smoke chamber, and a kiln tail decomposition furnace connected in sequence; and a C5 preheating furnace connected to the rotary kiln tail smoke chamber, the C5 preheating furnace being connected in sequence to C4, C3, C2, and C1 preheating furnaces, a plurality of combustion temperature measurement points and carbon monoxide measurement points being arranged in the C5 preheating furnace around the core position of nitrogen oxide generation and emission, a first ammonia injection point being arranged at a position close to the flue in the upper half of the C5 preheating furnace body, and a second ammonia injection point being arranged in the C5 preheating furnace outlet flue.

[0011] Furthermore, the first ammonia injection site is provided with 3 to 4 denitrification spray guns, and the second ammonia injection site is provided with at least 4 denitrification spray guns.

[0012] Furthermore, the nozzle of the denitrification spray gun is installed in a direction opposite to the main rotation direction of the particulate material.

[0013] Furthermore, each of the denitrification spray guns is provided with its own matching ammonia regulating valve and flow meter.

[0014] Furthermore, the temperature detection points and carbon monoxide concentration detection points are arranged in the furnace body and the flue of the C5 preheating furnace.

[0015] Furthermore, each of the temperature measurement points and carbon monoxide measurement points is connected to an ammonia injection regulator, and the ammonia injection regulator is connected to the ammonia water regulating valve and the flow meter.

[0016] The advantages and beneficial effects of the utility model are as follows: the utility model can flexibly adjust the injection amount of the denitrification reducing agent according to the flue gas conditions fed back by the measuring points through the multi-level ammonia injection points and the supporting ammonia injection regulating device, so that the reaction is carried out in the most efficient range. Compared with the traditional SNCR denitrification technology, the reaction efficiency of the denitrification reducing agent and NOx is improved, the denitrification efficiency is improved, and there is no need to match the SCR denitrification system, thereby reducing the denitrification operation cost. The original large-flow spray gun and the rough ammonia feed pump frequency conversion adjustment feeding adjustment method are cancelled, and instead, multiple small-flow spray guns equipped with ammonia regulating devices are used to make the amount of ammonia injected more accurate, and at the same time, a more uniform and more fully contacted gas-liquid contact is formed in the furnace body, thereby improving the denitrification reaction efficiency and avoiding excessive injection of ammonia. The utility model is particularly suitable for simple modification of existing equipment, achieving the best environmental protection effect with the least capital investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The utility model is further described below in conjunction with the accompanying drawings and embodiments.

[0018] Figure 1 It is a structural schematic diagram of the system described in Embodiment 1 of the present utility model;

[0019] Figure 2 It is a spraying schematic diagram of the denitration spray gun described in the third embodiment of the utility model;

[0020] Figure 3 This is a block diagram of the detection principle described in Example 6 of the present utility model. DETAILED DESCRIPTION

[0021] Embodiment 1:

[0022] The present embodiment is an integrated system for multi-stage precision ammonia injection and denitrification in cement kilns. The present embodiment comprises: a rotary kiln head 1, a rotary kiln 2, a rotary kiln tail smoke chamber 3, and a kiln tail decomposition furnace 4 connected in sequence; and a C5 preheating furnace 5 connected to the rotary kiln tail smoke chamber, the C5 preheating furnace being sequentially connected to C4, C3, C2, and C1 preheating furnaces 6, 7, 8, and 9, a plurality of temperature measurement points 501 and carbon monoxide measurement points 502 are arranged around the core position of nitrogen oxide generation and emission in the C5 preheating furnace, a first ammonia injection point 503 is arranged at a position close to the flue in the upper part of the C5 preheating furnace body, and a second ammonia injection point 504 is arranged in the C5 preheating furnace outlet flue, as shown in FIG. Figure 1 shown.

[0023] Temperature measurement points, carbon monoxide measurement points, ammonia injection points, and ammonia injection adjustment devices are set up around the core positions of nitrogen oxide generation and emission (connected to the front end of the ammonia injection points) to achieve the purpose of multi-stage precise ammonia injection. It is known that low-nitrogen burners are usually installed at the kiln head combustion point of cement kilns. No modification is required here. The flue gas generated by the kiln head combustion goes along the direction of the rotary kiln to the kiln tail smoke chamber, and is mixed with the flue gas at the outlet of the decomposition furnace of the preheating furnace through the flue, and then enters the C5 furnace. After being fully connected with the material in the furnace, it enters the subsequent C4 to C1 furnaces from the flue. Therefore, the C5 furnace is the preheating furnace with the highest flue gas temperature.

[0024] The first is the setting of ammonia injection points: the C5 furnace is a furnace body with an upper cylindrical and lower conical bucket shape. Generally, when denitrification reducing agent is sprayed, 3 to 4 denitrification spray guns are set on the upper part of the cylindrical wall of the furnace body. In addition to the reducing agent spray gun set in the furnace body itself, this embodiment sets 4 denitrification spray guns at the flue of the furnace outlet to increase the number of spray guns and maximize the number of injection points within the adjustable range of ammonia water.

[0025] When installing the spray gun, in order to avoid clogging of the nozzle by a large amount of solid material, the nozzle needs to be installed in the opposite direction of the main rotation direction of the particulate material. When the concentration of nitrogen oxides is low and some denitrification spray guns stop spraying ammonia, a small amount of compressed air needs to continue to be introduced to avoid clogging of the nozzle.

[0026] The ammonia spray regulating device is a device for finely controlling the amount of ammonia injection. The core regulating equipment is the ammonia regulating valve and flow meter, and is equipped with accessories such as pressure gauges, filters, switch valves, and reflux pipes. The front end of each spray gun is equipped with an ammonia spray regulating device. Through the matching of regulating valves and reflux pipes, the amount of ammonia that finally enters the spray gun can be finely controlled to avoid the instability of the ammonia spray effect caused by the rough frequency conversion regulation of the ammonia delivery pump.

[0027] Secondly, the temperature measuring point and the carbon monoxide measuring point are also set on the C5 furnace body and the flue at the furnace outlet to detect the incoming flue gas temperature and the carbon monoxide concentration in the flue gas in real time. These two flue gas parameters can basically feedback the combustion conditions in the decomposition furnace of the preheating furnace and the kiln head of the rotary kiln. By drawing the curve, the range of the nitrogen oxide concentration in the flue gas can be determined. The DCS system controls the signals of the temperature and carbon monoxide measuring points, the relationship curve between the measuring points and the nitrogen oxide concentration, and the ammonia injection regulating device in a chain manner, so as to finely control and adjust the ammonia injection amount without hysteresis.

[0028] Finally, the pollutant emission parameters at the chimney outlet are connected to the DCS to form an integrated denitrification system with front-end signal control and back-end signal feedback, further achieving ultra-low emissions of pollutants.

[0029] Embodiment 2:

[0030] This embodiment is an improvement of the first embodiment, and is a refinement of the first ammonia injection point and the second ammonia injection point of the first embodiment. In this embodiment, the first ammonia injection point is provided with 3 to 4 denitrification spray guns, and the second ammonia injection point is provided with at least 4 denitrification spray guns.

[0031] In this embodiment, a plurality of small-flow denitrification spray guns are arranged at the ammonia spraying points, and the spray gun flow rate is between 0 and 200 kg / h. Accurate delivery of the reducing agent is achieved by increasing the number of spray gun points and refining the single-point flow rate.

[0032] Embodiment three:

[0033] This embodiment is an improvement of the above embodiment and is a refinement of the above embodiment regarding the denitration spray gun. The nozzle 505 of the denitration spray gun described in this embodiment is installed in a direction opposite to the main rotation direction 10 of the particulate material. Figure 2 shown.

[0034] Normally, the flue gas in the combustion furnace is rotating and rising, and the direction of rotation is determined by the furnace type during the preheating furnace design stage. Therefore, the installation direction of the denitrification spray gun nozzle should be set according to the direction of the flue gas cyclone. The main rotation direction of the back-facing particulate material refers to the direction of the nozzle following the direction of the flue gas cyclone, that is, the flue gas particles flow from the back of the nozzle to the nozzle's ejection direction, such as Figure 2 shown.

[0035] Embodiment 4:

[0036] This embodiment is an improvement of the above embodiment and a refinement of the above embodiment regarding the denitration spray gun. Each of the denitration spray guns described in this embodiment is provided with its own matching ammonia regulating valve and flow meter.

[0037] The ammonia regulating valve and flow meter form a small feedback system: the flow meter monitors the amount of ammonia sprayed, and the amount of ammonia sprayed is controlled by the ammonia spray regulator.

[0038] Embodiment five:

[0039] This embodiment is an improvement of the above embodiment, and is a refinement of the temperature detection points and carbon monoxide concentration detection points of the above embodiment. The temperature detection points and carbon monoxide concentration detection points described in this embodiment are set in the furnace body and flue of the C5 preheating furnace.

[0040] Several groups of temperature detection points and carbon monoxide concentration detection points can be set and installed in different parts of the preheating furnace. In this embodiment, the temperature detection points and carbon monoxide concentration detection points are divided into two groups, one group is installed in the furnace body of the preheating furnace, and the other group is installed in the flue of the preheating furnace. In this way, the ammonia injection regulator can determine the amount of ammonia injection according to the temperature and carbon monoxide concentration in the furnace body and the flue, forming a feedback control between the input and output.

[0041] Embodiment six:

[0042] This embodiment is an improvement of the above embodiment, and is a refinement of the temperature detection point and the carbon monoxide concentration detection point of the above embodiment. In this embodiment, each of the temperature measurement points and the carbon monoxide measurement points is connected to the ammonia injection regulator, and the ammonia injection regulator is connected to the ammonia water regulating valve and the flow meter. Figure 3 shown.

[0043] With the comprehensive utilization of solid waste in cement kiln fuel and the control of cement kiln production constants under environmental protection management, the flexibly adjustable denitrification system has become the focus of cement kiln denitrification. This embodiment uses multi-level ammonia injection points and a matching ammonia injection adjustment device to flexibly adjust the injection amount of the denitrification reducing agent according to the flue gas conditions fed back by the measuring points, so that the reaction can be carried out in the most efficient range.

[0044] This embodiment optimizes and upgrades the traditional SNCR denitrification technology through the combination of measurement point signal + fine adjustment of ammonia injection, maximizes the reaction efficiency of the denitrification reductant and NOx, improves the denitrification efficiency, eliminates the need for an SCR denitrification system, and reduces the denitrification operating cost.

[0045] This embodiment eliminates the original large-flow spray gun and the rough ammonia feeding pump frequency conversion regulation feeding regulation method, and instead uses multiple small-flow spray guns equipped with ammonia regulation devices to make the amount of ammonia sprayed more accurate, while forming a more uniform and more complete gas-liquid contact in the furnace body, thereby improving the denitrification reaction efficiency and avoiding excessive ammonia injection.

[0046] This embodiment optimizes the traditional regulation logic of outlet nitrogen oxide concentration and ammonia injection amount into the regulation logic of flue gas temperature, carbon monoxide measurement point signal and ammonia injection amount, and moves the signal for regulating the ammonia injection amount from the back end to the front end, thereby avoiding the lag in the regulation of ammonia water amount. At the same time, the detection signal of NOx concentration at the chimney outlet is integrated into the DCS, and the front-end control result is fed back to form an integrated multi-stage precise ammonia injection denitrification system.

[0047] Finally, it should be noted that the above is only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model has been described in detail with reference to the preferred arrangement scheme, ordinary technicians in this field should understand that the technical solution of the utility model (such as the form of the preheating furnace, the structure and form of the rotary kiln, etc.) can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the utility model.

Claims

1. A cement kiln multi-stage precision ammonia injection denitrification integrated system, comprising: Connected in sequence: rotary kiln head, rotary kiln, rotary kiln tail smoke chamber, kiln tail calciner; And a C5 preheating furnace connected to the rotary kiln tail smoke chamber, the C5 preheating furnace is connected to the C4, C3, C2, and C1 preheating furnaces in sequence, and is characterized in that a plurality of combustion temperature measurement points and carbon monoxide measurement points are arranged around the core position of nitrogen oxide generation and emission in the C5 preheating furnace, a first ammonia injection point is arranged at a position close to the flue in the upper part of the C5 preheating furnace body, and a second ammonia injection point is arranged in the C5 preheating furnace outlet flue.

2. The integrated system according to claim 1, characterized in that: The first ammonia injection site is provided with 3 to 4 denitrification spray guns, and the second ammonia injection site is provided with at least 4 denitrification spray guns.

3. The integrated system according to claim 2, characterized in that: The nozzle of the denitrification spray gun is installed in a direction opposite to the main rotation direction of the particulate material.

4. The integrated system according to claim 3, characterized in that: Each of the denitrification spray guns is provided with its own matching ammonia regulating valve and flow meter.

5. The integrated system according to claim 4, characterized in that: The temperature detection points and carbon monoxide concentration detection points are arranged in the furnace body and the flue of the C5 preheating furnace.

6. The integrated system according to claim 5, characterized in that: Each of the temperature measuring points and carbon monoxide measuring points is connected to an ammonia spray regulator, and the ammonia spray regulator is connected to the ammonia water regulating valve and the flow meter.

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