KR20030079666A - NOx reduction apparatus at cement plants using selective non-catalytic reduction and method thereof - Google Patents

Abstract

PURPOSE: Provided are an apparatus and a process for the reduction of NOx in a cement plant using selective non-catalytic reduction(SNCR), which can maximize the NOx removal efficiency economically. CONSTITUTION: The apparatus for the reduction of NOx in a cement plant using a SNCR method comprises: a sprayer for spraying urea prill or urea water at the opening of a rotary kiln(8) into which a cement material is introduced to reduce the NOx generated therein; at least one sprayers for spraying urea prill, disposed at the circumference of the upper sidewall of a final calciner(C5) maintained at the inside temperature of 850-1100 deg.C to reduce the NOx introduced and generated therein; and a controller(7) for controlling the spraying amount and position of urea at the rotary kiln(8), the calciner(C5) and the final cyclone(K4) by detecting the inside temperature, load, generated NOx amount and fuel properties therein.

Description

NOx reduction apparatus at cement plants using selective non-catalytic reduction and method

The present invention relates to a device and a method for reducing nitrogen oxides in cement plants using selective non-catalytic reduction (SNCR), wherein ammonia and urea, particularly urea, are used as reducing agents depending on the type of cement plant. The injection position is adjusted within the appropriate combustion temperature range in the plant, and the injection amount is varied according to the generation amount of nitrogen oxide. When the powder reducing agent is injected and used, it is automatically controlled whether to be injected directly or in an aqueous solution.

While using the SNCR method, the effects and methods for reducing nitrogen oxides through reducing agents are already well known. U.S. Patent Application No. 3,900,554, entitled "Method for Reducing Nitrogen Monoxide Concentrations in Combustion Emissions Using Ammonia, filed March 16, 1973 by Exxon Research and Engineering Company. the reduction of the concentration of NO in combusion effluents using ammonia), by spraying ammonia, a precursor of ammonia or an aqueous solution thereof to a combustion gas containing sufficient oxygen and optionally with nitrogen monoxide at a temperature of 870-1,100 ° C. It is noted that, in contact with ammonia, the combustion gas must be within the above temperature range for efficient reaction to reduce nitrogen oxides. U.S. Patent No. 4,208,386, entitled "Urea reduction of NOx in combustion, filed by Electric Power Research Institute, Inc. on March 3, 1976. effluents "and U.S. Patent No. 4,325,924, entitled" Urea reduction of NOx in fuel rich combustion effluents, "filed Oct. 25, 1977, filed by the same applicant. While it is known that it can be reduced by using urea or its aqueous solution in the high temperature range of 700 to 1,100 ℃ contained in the combustion gas using excess air fuel, while ammonia or urea of Injection through spraying is important for selective reduction and economical operation and overcomes the problem of eliminating atmospheric emissions and inhibitors of ammonia. The.

U.S. Patent No. 4,992.249, entitled "Reduction of Nitrogen and Carbon Contaminants Using Urea Aqueous Application, filed by Fuel Tech, Inc., filed August 27, 1987. Nitrogen- and Carbon-based pollutants through the use of urea solution ", when the urea solution increases in water size and decreases in urea concentration, the removal of contaminants from high-temperature, high-oxygen exhaust gases Although it is known that it can be achieved more effectively, there is a problem that must be thoroughly sprayed in the temperature range required by the rotary kiln, which is part of the cement plant, rather than the importance of the aqueous solution to control the size and concentration of water droplets.

U.S. Pat. No. 4,842,834, entitled "Process for reducing the concentration of pollutants in an effluent," filed by Pueltec Incorporated on February 2, 1987, is a The atomizer adopted to improve the size can facilitate the addition of additives to the urea solution, but the particle size distribution when injecting a two-phase mixture of air and a reducing solution of nitrogen oxide (NOx) at the speed of sound through a nozzle It can achieve the effect of improving the but does not effectively utilize the unique properties of the additive.

Even in the above-mentioned improvement measures, when the SNCR method is adopted in the rotary kiln of a cement plant, additives for reducing nitrogen oxides are mainly injected in aqueous solution, which cannot suppress the problem of vaporization before reaching the optimum temperature range. Nor can we maintain momentum to provide a complete response within the rotary kiln.

SUMMARY OF THE INVENTION The present invention was created to overcome the above-mentioned problems, and includes nitrogen oxides (NOx) in a construction facility using rotary kilns of cement plants and recycled fuels using fuels and wastes such as preheaters and calciners. In particular, it relates to the effective use of the selective non-catalytic reduction method (SNCR) to reduce emissions.

In order to reduce the environmental pollution due to nitrogen oxides generated during the cement production process in rotary kilns, SNCR is used to treat gaseous substances. Especially in rotary kilns, limestone, clay and silica compounds are more than 1,500 ℃. The production of nitrogen oxides at high temperatures during the production by heating is further increased mainly due to the formation of free radicals of oxygen and nitrogen and the chemical bonding between them. In addition, the fuel contains nitrogen compounds, which are converted to nitrogen oxides during the combustion process and injected into a chemical to be used as a reducing agent such as ammonia or urea to react with the nitrogen oxides to reduce the nitrogen oxides and remove them from the exhaust gas. Or convert to other releaseable materials. To this end, the reduction reaction takes place in the gas phase in the temperature range of 900 to 1,100 ℃, the concentration of the nitrogen oxide discharged is maintained at 200 to 1,500ppmv. Furthermore, the stoichiometrically required amount of ammonia or urea is adjusted to 1 to 3 times, but the SNCR reaction requires more accurate temperature in the gas phase and at the same time requires the exchange of reactants in dilution.

The fuel mix introduced into the preheater is a large cylindrical equipment with a diameter of 2 to 6m and a length of 40 to 100m or more, and is introduced into a kiln that rotates at a speed of 2 to 4rpm with a slope of 3 to 5 °. The rotary kiln's geometry, which continuously heats to the outlet and rises to 1,450 ° C to produce clinkers, is characterized by a temperature range for reducing nitrogen oxides at a distance of 5 to 50 m from the raw material inlet, for example 900 to 1,100. ℃ is generally maintained. Additives for the reduction of nitrogen oxides, preferably urea, will be oxidized to deplete the nitrogen oxides when they are brought into contact with hot gases in the hot zone of the kiln (rotary kiln). Accordingly, the technical requirement is to use an aqueous solution dissolved in water to protect the additive in the high temperature range, which makes it difficult to inject chemicals into the point having an appropriate temperature range in the kiln. In other words, depending on the type of equipment of the cement plant, the position of the reducing agent is replaced, the combustion temperature changes according to the characteristics of the fuel used, and the amount of nitrogen oxide is automatically controlled to set the injection position of the reducing agent. The present invention provides a method and apparatus for economic application technology and injection location of SNCR, which can significantly reduce the labor in a more economical and optimal mode of operation by determining which phase of the aqueous solution is to be injected.

It describes the injection position and control method of the above-described reducing agent for the method of reducing nitrogen oxide in the cement manufacturing process using the selective non-catalytic reduction method according to the present invention.

The first embodiment according to the present invention is a method for reducing nitrogen oxides in a calciner and kiln according to the SP (Spension Preheater) process, particularly in the cement manufacturing plant.

The injection position must be set to inject the urea prill into the calcination furnace at an appropriate temperature range, preferably at least one sprayer that sprays the urea prill into the calcination at a rate of 15-30 m / s or more. And a sprayer positioned at the inlet of the kiln, which is disposed at a point in the temperature range of 900 to 1,100 ° C, and which has a sufficient momentum to mix and react with the combustion gases and propel the air through the air. Detecting the amount of nitrogen oxides generated in the kiln and the calcination furnace according to the change of the properties of the fuel, for example, waste fuel such as waste tires or coal fuel, and one arranged in the calcination furnace to control the control Injecting the reducing agent through the nebulizer according to the generation amount of nitrogen oxide in the nebulizer and the nebulizer of the kiln And it is adapted to automatically controllable element having a spray amount.

The second embodiment according to the present invention is a method for reducing nitrogen oxides in calcination furnace, cyclone and kiln according to NSP (New Suspension Preheater) process, especially in cement plant equipment.

It is the same as the method of reducing in the calcination furnace and the kiln described above with the first embodiment described above, as well as reducing the same effect, ie nitrogen oxide, by placing one or more atomizers in the cyclone added to the process equipment. More specifically, the preheater, one of the core parts of the cement manufacturing process, consists of a multistage cyclone and a multistage calciner, where the raw material mix is preheated and fed into the kiln. Fuel used for preheating and firing the raw material mix includes bituminous coal, heavy oil, or other recycled fuels, and detects the amount of nitrogen oxides generated by the change in the characteristics of the fuel used in the final cyclone and the final calcination furnace. In other words, ureaprile is sprayed at a speed of preferably 15 to 30 m / s or more through one or more sprayers disposed on the upper side wall having a combustion temperature range of 850 to 1,100 ° C., which can easily cause chemical reactions. It is sprayed through the air supplied to the blower so as to be able to diffuse completely into the combustion gas to have sufficient momentum. Detecting the amount of nitrogen oxides generated in the kiln, the calcination furnace and the cyclone and controlling one or more atomizers and the atomizers of the kiln in the calcination furnace and cyclone according to the amount of nitrogen oxide Injecting a reducing agent through the urea spray amount is automatically controlled.

In a kiln, for example a rotary kiln, the position and control method of the nebulizer are the same in the first and second embodiments described above. The urea frill can propel the urea frill at a speed of 25 to 120 m / s or more, preferably within the opening of the rotary kiln, so that the reaction can occur in the temperature range of 900 to 1,100 ° C., providing sufficient momentum to provide combustion gas and It is possible to mix urea frills through the air supplied to the blower to be mixed or to spray urea water in the form of urea in which urea is dissolved in water. It can be used at a high temperature of 1,000 to 1,200 ° C. to control and push the spray amount of the urea according to the property of the product.

As such, the reduction of urea (CO (NH ₂ ) ₂ ) and nitrogen oxides (NOx) produces nitrogen (N ₂ ), moisture (H ₂ O), and carbon dioxide (CO ₂ ) that do not affect the environment. Thus, the purified exhaust gas can be controlled to suppress environmental pollution.

1 is a schematic diagram of a first embodiment according to the present invention;

2 is a schematic diagram of a second embodiment according to the present invention;

3 is a flowchart illustrating a control method of reducing nitrogen oxides according to the present invention.

The features of the present invention will now be described in more detail with reference to the accompanying drawings.

1 is a view showing a first embodiment based on the SP (Spension Preheater) process of the cement manufacturing process according to the present invention.

The present invention relates to an atomizer capable of spraying urea used to reduce nitrogen oxides to a preheater and a kiln, and a control method for spraying an appropriate amount of urea through the atomizer. Urea is mainly used as a reducing agent used to reduce nitrogen oxides. The urea prill to be sprayed in the final calcination furnace (C5) and the kiln (8) of each component is stored in a dry state in the urea storage tank (1), through which the air discharged from the blower (9) is passed through the dryer. By supplying the air in the dry state to the urea storage tank (1) can be stored dry contents. The urea supply module (2) for smoothly supplying the urea to be used for the reduction of nitrogen oxides in the loading place in the cement manufacturing process provides a path to receive the urea from the urea storage tank (1) to supply a variety of components. The urea prill stored in the urea storage tank (1) is generally in the form of powder, but when the calcination furnace (8) is required to supply selectively in water droplets, the interface applied to the urea prill in the urea supply module (2) The urea is supplied to the urea water supply unit 2 by removing a polymer such as an activator. The urea water may be prepared by mixing and dissolving urea and water supplied to the urea water supply unit 2 to provide the calcination furnace 8 under the jurisdiction of the controller 7. Since the above facilities are already well known to those skilled in the art, further techniques are avoided in order to exclude unnecessary ambiguity.

The cement raw material is fed to one or more multistage calcination furnaces (C2, C3, C4, C5; calciner). These calcination furnaces (C2, C3, C4, C5) generally act as a preheater to dry the moisture in the raw material mix and preheat the raw material mix at high temperature to cause decarbonation reaction of the raw material mix introduced into the kiln (8). The effect of increasing the calcination rate (decarbonate rate) is achieved. The raw material mix reaching the final calcination furnace (C5) discharges nitrogen oxides through internal combustion, and the urea frill is discharged from the urea supply module (2) to the upper side wall of the final calcination furnace (C5) to reduce the nitrogen oxides. Supplied via one or more nebulizers 5 arranged. Positioning of the atomizer 5 to be disposed in the calcination furnace (C5) is provided with one or more around the circumference of the calcination furnace (C5), the internal temperature of the calcination furnace (C5) is 900 to 1,100 ℃ point, preferably 3 to Equipped with six sprayers (5).

In particular, the nebulizer 5 propels the urea frill through air in order to more effectively diffuse the urea frill in the form of powder into the combustion gas.

The raw material mix, which is sufficiently calcined in the calcining furnaces C2, C3, C4 and C5, is injected into the elongated cylindrical kiln 8, such as a rotary kiln. A burner is mounted at the opposite outlet corresponding to the opening of the kiln 8 so that the flame is directed toward the inside of the kiln 8. The temperature of the outlet of the kiln 8 is maintained at a high temperature of 1,500 ° C. or more under the influence of the burner, but the opening in which the cement raw material is injected into the kiln 8 is relatively low. Nitrogen oxides, which are the main culprit of environmental pollution due to combustion, are also discharged in the kiln 8, so that elements are introduced into the kiln 8 to reduce them. The temperature at the 10-20 m point inside the kiln 8 is maintained at about 1,100 ° C. In general, since the linear flow velocity of the combustion gas in the kiln 8 is in the range of about 3 to 25 m / s, diffusion for the fine particles The atomizer 4 located in the opening for injecting the cement raw material in consideration of the obstacle phenomenon allows the urea ripple to be propelled at a speed of 25 to 120 m / s through the air by a controlled amount, or the urea water supply unit 3 The urea water supplied from is sprayed.

In addition, the urea sprayed through the sprayer 4 into the kiln 8 is preferably in the form of urea prills in powder form, but optionally spraying urea water dissolved in water and in the water droplets through the sprayer 4. There is a case. In this case, the urea water in the water droplet state supplied from the urea water supply unit 3 can be sprayed into the calcination furnace 8 by determining the amount of urea water according to the state of the calcination furnace 8 through the controller 7. .

Figure 2 is a view showing a second embodiment based on the NSP (New Suspension Preheater) process of the cement manufacturing process according to the present invention. The first embodiment and the second embodiment will be described at the same time in order to avoid clarity of description of the same equipment and the same control method and to emphasize clarity.

Of the multistage cyclones K2, K3 and K4 added by the NSP process, the final cyclone K4 is the same as the calcination furnace C5 described in the first embodiment, which is disposed on the upper side wall of the cyclone K4. The urea frill is supplied through the above atomizer 6. The location of the nebulizer 6 arranged in the cyclone K4 has one or more around the circumference of the cyclone K4 at an internal temperature of 850-1,100 ° C., preferably 3-6 nebulizers 6 It is provided.

Like the atomizer 4 already described above, the atomizer 6 allows the urea ripple to be pushed through the air in order to more effectively diffuse the urea frill, which is in powder form, into the combustion gas, and its propulsion rate is 15 to 30 m /. It is more than s.

3 is a flowchart illustrating a control method for reducing nitrogen oxides according to the SNCR method of the present invention, in which the urea supply module is used to adjust the controller 7 to store the urea stored in the urea frill storage tank 1 in a dry state. (2) through the improvement, quantification and supply of urea frill can be supplied to each step (100, 200, 300) urea frill or urea water.

In particular, the internal temperature transmitted to the sensor (not shown) mounted adjacent to each atomizer 4, 5, 6, and the generation amount or inflow amount of nitrogen oxides are sensed, and this is transferred to each atomizer through the urea supply module 2. And steps to determine the amount of urea to be ejected. In step 100, the amount of urea frill or urea water to be sprayed is determined in consideration of the amount of nitrogen oxide generated in the kiln 8, the internal temperature and the load of the kiln 8, and then sprayed into the atomizer 4. Step 200 is the urea prill to be sprayed in consideration of the nitrogen oxide generated in the calcination furnace (K5) and the amount of nitrogen oxide generated in the calcination furnace (8) and introduced into the calcination furnace (C5) and the internal temperature and load of the calcination furnace (C5) Determine the amount of nebulizer (5). Step 300 determines the amount of urea to be sprayed to the atomizer 6 in consideration of the amount of nitrogen oxide introduced into the cyclone (K4), the internal temperature and the load of the cyclone (K4). In general, the amount of urea is added to the molar number (mole) of the nitrogen oxide generated stoichiometrically, 0.5 to 3 times, preferably 1 to 2 times the urea.

All of these steps (100, 200, 300) detect the internal temperature according to the loads of the components collected from the components (8, C5, K4) equipped with the atomizers (4, 5, 6) and the changes in the properties of the fuel used. Atomizers 4, 5 and 6 disposed in suitable components 8, C5 and K4 as controllers 7 in order to maximize the effect of reduction of nitrogen oxides received from the urea supply module 2 due to Spray through.

As described above, according to the present invention, the internal temperature of the kiln, the calcining furnace and the cyclone and the generation or inflow of nitrogen oxides are sensed to control the amount of the reducing agent in the nebulizer suitable for improving the nitrogen oxide reduction effect through the controller. It is possible to minimize the amount of nitrogen oxides released into the atmosphere, which is the main cause of pollution, thereby increasing the labor and economic effects.

Claims (8)

In cement plants using selective non-catalytic reduction method (SNCR) to reduce nitrogen oxides, A sprayer (4) for spraying urea frill or urea water to reduce nitrogen oxides generated therein at an opening through which cement raw materials of a kiln (rotary kiln) are introduced; At least one arranged around its circumference to spray ureapriles to reduce nitrogen oxides entering and generated at the upper side wall point of the final calciner (C5; calciner) with an internal temperature preferably maintained between 850 and 1100 ° C. A nebulizer 5 and; By detecting the internal temperature and load of the firing furnace (8), the final calcining furnace (C5) and the final cyclone (K4), the generation amount of nitrogen oxide and the appearance of the fuel used, the components (8, C5, K4) And a controller (7) for controlling the amount of the element to be sprayed and the spraying position thereof. The circumference of the circumference of claim 1, wherein the circumference of the urea prill is sprayed to reduce the nitrogen oxides introduced at the point of the upper side wall of the final cyclone (K4) maintaining an internal temperature of preferably between 900 and 1100 ° C. A device for reducing nitrogen oxides in a cement plant having at least one sprayer (6). 3. The cement plant according to claim 1 or 2, wherein the cement plant has a fixed quantity of urea frills or urea water in the firing furnace (8), the final calcination furnace (C5) and the atomizers (4, 5, 6) of the final cyclone (K4). Nitrogen oxide reduction device in a cement plant having a urea supply module (2) for supplying a sprayable. 3. The sprayer (4) according to any one of the preceding claims, wherein the sprayer (4) can spray ureaprile or urea water at a rate of 25 to 120 m / s or more, and the sprayers (5,6) have a speed of 15 to 30 m / s or more. Reduction device of nitrogen oxide in cement plant spraying urea frill with furnace. 3. A device for reducing nitrogen oxides in a cement plant according to claim 1 or 2, wherein the atomizer (4, 5, 6) is capable of spraying urea prills more effectively through air. In cement plants using selective non-catalytic reduction method (SNCR) to reduce nitrogen oxides, Sensing the internal temperature and load of the kiln 8, the final calcination furnace C5 and the final cyclone K4, and the amount of nitrogen oxides generated; Providing urea frills or urea water from the urea supply module (2) to the firing furnace (8), the final calcining furnace (C5) and the final cyclone (K4); Spraying urea frill or urea water by a sprayer (4) located in the opening of the kiln (8; rotary kiln) (100); Spraying urea frill (200) by the sprayer (5) located on the upper side wall of the final calciner (C5; calciner); Controlling the urea spraying amount according to the concentration of the nitrogen oxides through the controller (7); Reduction method of nitrogen oxides in the cement plant using a selective non-catalytic reduction method. 7. A method according to claim 6, further comprising the step (300) of the sprayer (6) located on the upper side wall of the final cyclone (K4) spraying urea prills. 7. The method according to claim 6, further comprising the step of selecting urea frills or urea water to be sprayed into the kiln (8).