KR20230091756A - SNCR-SCR Hybrid NOx Reduction System - Google Patents

Abstract

The SNCR-SCR hybrid nitrogen oxide reduction system according to the present invention is (1) through computational fluid dynamics (CFD), the dust is not biased and comes down constantly, and the temperature is uniform. NHx-based reducing agent sprayed A nozzle is installed to increase the efficiency of the selective non-catalytic reduction (SNCR) and achieve a _NOx reduction rate of 40 to 50% through leveling control, and as a reducing agent for NOx in the selective catalytic reduction (SCR) at the rear. SNCR facility for controlling (CONTROL) the degree of unreacted NH ₃ slip generation to be used as; and (2) an SCR facility installed at the rear end of the SNCR facility based on exhaust gas and performing selective catalytic reduction (SCR) on the catalyst while using unreacted NH ₃ slip generated in the SNCR facility as a NOx reducing agent.
Through the SNCR-SCR hybrid nitrogen oxide reduction system according to the present invention, the NO _X removal efficiency according to the construction of the SNCR-SCR hybrid integrated system is more than 80, the residual NOx is 80 ~ 82ppm, and the SCR due to high SNCR efficiency and SCR load reduction Installation costs (catalyst usage reduction and SCR facility miniaturization, etc.) can be drastically reduced.

Description

SNCR-SCR Hybrid NOx Reduction System {SNCR-SCR Hybrid NOx Reduction System}

The present invention relates to a SNCR-SCR hybrid nitrogen oxide reduction system having a SNCR facility and an SCR facility. Through the SNCR-SCR hybrid nitrogen oxide reduction system according to the present invention, the NO _X removal efficiency according to the construction of the SNCR-SCR hybrid integrated system is more than 80%, the residual NOx is 80 ~ 82ppm, and the high SNCR efficiency and SCR load reduction SCR installation costs (catalyst usage reduction and SCR facility miniaturization, etc.) can be drastically reduced.

In addition, the SNCR-SCR hybrid nitrogen oxide reduction system according to the present invention can be applied and designed as an innovative technology for reducing fine dust in the cement industry.

Despite various efforts, such as enactment of the National Air Quality Conservation Act, energy consumption is rapidly increasing due to the improvement of living standards, resulting in the generation and serious emission of numerous air pollutants. Among them, nitrogen oxides from fuel combustion in energy-consuming industries generate secondary pollutants through photochemical reactions and are one of the main air pollutants. As nitrogen oxide emission regulations are strengthened worldwide, it must be treated according to the emission control concentration regulation and total amount management reinforcement policy before being discharged into the atmosphere from major emission facilities such as power plants, incinerators, and combustion facilities in the cement process. As the need to essentially reduce nitrogen oxides increases, methods for reducing nitrogen oxides at emission sources are being actively developed.

BACKGROUND OF THE INVENTION Much of the electricity used in homes and industries throughout the world is generated by boilers and power plants that burn fossil fuels (coal, oil, LNG) and biomass. The high-temperature flue gas (combustion gas) produced runs a gas turbine or boils water to generate steam, which runs a steam turbine, which together with a generator produces electric power. The flue gas vapor then passes through an air preheater, for example a rotary wheel heat exchanger which transfers the heat from the flue gas to the incoming air vapor, before passing to the combustor. Partially cooled combustion gases pass from the air preheater to the exhaust stack.

When fossil fuels and biomass are used as the main fuel sources, the combustion gases contain pollutants such as sulfur oxides, nitrogen oxides, carbon monoxide and soot particulates. Air emissions of all of these pollutants are subject to federal and local laws that significantly limit the levels of these flue gas components.

Flue gas discharged from municipal and private incinerators that incinerate waste contains trace elements such as fly ash, hydrogen chloride (HCl), sulfur oxides (SOx), nitrogen oxides (NOx), heavy metals including mercury, or dioxins. are doing These harmful components must be removed for environmental protection.

On the other hand, the cement industry is an industry that builds the foundation of the country along with the steel and petrochemical industries, and consumes a large amount of resources and energy. In terms of environment, negative aspects such as dust, CO ₂ and nitrogen oxide (NOx) are generated. A lot of this has come to the fore. In addition, interest in recycling industrial by-products into 'cement raw materials' or 'fuel' is increasing. Since high-temperature monochlorination firing is essential for maintaining and improving the production process and quality, the cement industry inevitably has process conditions in which NOx is generated, and harmful substances including carbon monoxide and dust are emitted. are being added.

Nitrogen oxides expressed as NOx include nitrogen monoxide (NO) and nitrogen dioxide (NO ₂ ), as well as N ₂ O, N ₂ O ₃ , N ₂ O ₄ , N ₂ O ₅ , and NO ₃ . Only NO ₂ is targeted.

The NOx emission factors in power plants, incinerators, and cement production processes are 1) high-temperature oxidation of nitrogen molecules present in combustion air (thermal NOx), 2) oxidation of nitrogen compounds in fuel (fuel NOx), and 3) nitrogen contained in raw materials. 4) oxidation of fuel CH radicals and nitrogen compounds (prompt NOx).

NOx reduction technologies applicable to power plants, incinerators, and cement processes can be largely divided into two methods. One is a method of reducing NOx generation by controlling combustion conditions, and the other is a method of removing NOx generated in a combustion process.

The generation of thermal NOx in power plants, incinerators, and combustion facilities in cement processing is affected by flame temperature and oxygen concentration. Therefore, in order to reduce the generation of thermal NOx, it is important to reduce the factors that can change the flame temperature and oxygen concentration. The production of Fuel NOx and Feed NOx is not as well known as Thermal NOx, but it is generally known that the higher the nitrogen content of the fuel or raw material, the more it is generated. Therefore, in order to reduce fuel NOx and feed NOx, it is desirable to use fuel or raw materials with low nitrogen content. The type of kiln also affects NOx emissions. In the case of a kiln with high solid-gas heat transfer efficiency, NOx generation can be reduced because energy efficiency is high.

NOx produced by combustion is reduced to nitrogen through reducing agents. These reducing agents include CO, H ₂ , and reducing agents capable of generating NHx, such as ammonia and urea. Since CO and H ₂ also reduce oxygen in the exhaust gas, a large amount of the reducing agent is consumed, but the reducing agent capable of generating NHx can selectively reduce only NOx. These selective reduction methods include a selective catalytic reduction (SCR) using a catalyst and a selective non-catalytic reduction (SNCR) method without a catalyst.

Selective catalytic reduction (SCR) is a NOx removal method that is widely applied and effectively used in boilers, gas turbines, and internal combustion engines using fossil fuels. The principle of this method is to reduce NOx by injecting ammonia gas diluted with air or steam into the exhaust gas and supplying it to the catalyst layer.

Selective non-catalytic reduction (SNCR) is a method of decomposing NOx by directly injecting a reducing agent into high-temperature exhaust gas without using a catalyst, and the main reaction formula is as follows.

[Scheme 1]

4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O

SNCR has a low initial installation cost compared to other NOx reduction technologies, and is simple to apply to existing facilities, so it does not require a separate installation space, so it has excellent applicability, but its efficiency is somewhat low. In the reaction temperature range of 850 ~ 1,100 ℃, the NOx reduction efficiency shows a denitrification efficiency of 30 ~ 50%, but in the temperature range above the reaction temperature range, NOx generation increases due to the oxidation reaction of the supplied reducing agent (urea solution, ammonia water), In the low temperature range, the reducing agent does not react efficiently and ammonia slip occurs.

Reducing agents used in SNCR include various reducing agents containing NHx components such as ammonia (or ammonia water), urea (or urea water), ammonium carbamate, pyridine, ammonium acetate, cyanuric acid, and ammonium carbonate (hereinafter referred to as 'NHx-based reducing agents'). '), but urea water is used in most SNCR processes in terms of drug price, safety, supply stability, and by-product production. In the case of ammonia, the selectivity for NO is excellent compared to other types of reducing agents. SCR is operated at less than 400℃ due to the nature of the process, and this is a low-temperature process condition in terms of vaporization energy of urea water, so ammonia is mainly used in the SCR process. Since there is a possibility of contamination of city groundwater, it must be stored in a double-walled storage tank or made on a protected ground.

When using ammonia water as a reducing agent in a thermal power plant or industrial incinerator, it is advantageous to use urea water because ammonia itself is a toxic substance, and various regulations are severe in addition to the problem of having a harmful effect on the human body. Currently, in thermal power plants or industrial incinerator denitrification (SCR) facilities, denitrification facilities that apply urea water as a reducing agent are increasing in consideration of stable operation and environmental aspects.

A urea water spray device is a main accessory of SCR or SNCR, which is a denitrification device for reducing nitrogen oxides (NOx), an air pollutant, and is used to generate ammonia by thermally decomposing urea water.

Selective Catalytic Reduction (SCR) is a technology that uses ammonia as a reducing agent to convert NOx, one of air pollutants, into harmless N ₂ and H ₂ O. It shows high denitrification efficiency and has several advantages such as easy operation and maintenance As a result, it is the most representative technology for reducing NOx among the technologies developed so far, and it has already been commercialized worldwide and is in operation in various plants. It is widely used in Japan to remove more than 90% of NOx from boilers using fossil fuels, and is used in gas turbines and internal combustion engines in the United States. The principle of this method is to directly inject ammonia, and after injecting ammonia gas diluted with air or steam into the exhaust gas, supply it to the catalyst layer to reduce NOx, and the reduction reaction proceeds as follows. this reaction Since most of NOx is NO, Reaction Formula 1 becomes the main reaction.

[Scheme 1]

4NH ₃ + 4NO + O ₂ → 4N ₂ + 6H ₂ O

SCR is a process in which NH ₃ in ammonia or urea water selectively reacts with NOx on a catalyst to convert it into N ₂ , and is used to remove NOx emitted from gas turbines, diesel engines, and thermal power plants. The NOx reduction efficiency by SCR can be up to 90% or more, and it also contributes to the removal of VOCs, dioxins/furans and mercury.

In the case of ammonia, it has excellent selectivity for NO compared to other types of reducing agents and is mainly used in the SCR process. It must be stored in a heavy-walled storage tank or built on a protective ground, and in the event of a leakage accident, it is difficult to quickly respond to it due to difficulty in accessing the accident site, so there is a risk of expanding large-scale accidents. In addition, a large amount of anhydrous ammonia and ammonia water are required to cover SCR facilities of current power generation and incineration facilities.

Domestic cement companies have been installing and operating SNCR (Selective Non-catalytic Reduction) facilities since 2004 to reduce nitrogen oxides. As efficiency is influenced by various factors such as changes in exhaust gas composition due to combustion, there are limits to meeting current emission standards. Therefore, a highly efficient nitrogen oxide reduction technology capable of coping with various variables is required to solve this problem. It is installed between the preheater and the firing furnace, and the reaction temperature range is about 850 ~ 1,050 ℃, but the NOx reduction efficiency of SNCR is only 10 ~ 40%. Therefore, it is difficult to meet the recent standards in which emission standards are being strengthened.

In the cement industry, for the first time in the world, SCR equipment was applied at the Solnhofen cement plant in Germany. At the Solnhofen Cement Plant in Germany, using the pilot plant research results, SCR facilities were installed in the front of the dust collection facility (High Dust) in 2000, and catalysts were installed in three places of the 6-stage reactor. SCR inlet NOx concentration of 1,050 mg/Nm ³ and outlet 200 mg/Nm ³ were achieved, and SCR facilities are being built and operated in the cement manufacturing process.

There are three major types of SCR applied to overseas cement manufacturing processes, which are classified into 1) High Dust SCR, 2) Tail End SCR, and 3) Semi-Dust SCR.

As described above, the domestic cement industry is installing and operating SNCR facilities to reduce nitrogen oxides, but as the efficiency is influenced by the state of the cement manufacturing process, there is a limit to satisfying the currently strengthening emission standards. Accordingly, the cement manufacturing process requires the application of SCR technology, which is attracting attention due to the recently tightened NOx emission regulations worldwide. In addition, if the existing SNCR efficiency is around 30 ~ 50%, when linked with SCR, the nitrogen oxide reduction efficiency is over 90%, so along with the utilization of the SNCR system, the SCR system suitable for the domestic cement manufacturing process is essential. What needs to be done is the reality.

The present invention intends to design a SNCR-SCR hybrid nitrogen oxide reduction system equipped with a SNCR facility and an SCR facility to innovatively reduce the SCR installation cost due to high SNCR efficiency and consequent reduction in SCR load, while satisfying NOx regulations.

In addition, the present invention is to provide an innovative technology for reducing fine dust in the cement industry through a SNCR-SCR hybrid nitrogen oxide reduction system.

The first aspect of the present invention is (1) through computational fluid dynamics (CFD), an NHx-based reducing agent injection nozzle is installed at a point (s) where the temperature is uniform while the dust is not biased and comes down constantly, and the selective ratio Unreacted NH to be used as a reducing agent for NOx in the selective catalytic reduction (SCR) at the rear while demonstrating a _NOx reduction rate of 40 to 50% through increased catalytic reduction reaction (SNCR) efficiency and leveling control ₃ SNCR equipment that controls the degree of slip occurrence; and (2) an SCR facility installed at the rear of the SNCR facility based on exhaust gas and performing selective catalytic reduction (SCR) on the catalyst while using unreacted NH ₃ slip generated in the SNCR facility as a reducing agent for NOx SNCR including an SCR facility -SCR hybrid nitrogen oxide reduction system is provided.

For example, in the SNCR-SCR hybrid nitrogen oxide reduction system of the present invention, the _NOx removal efficiency according to the integrated system construction is 80% or more, the residual NOx is 80 ~ 82ppm, and / or the high SNCR efficiency and SCR load reduction SCR installation cost can be reduced.

A second aspect of the present invention is a method for treating NOx-containing combustion gas using the SNCR-SCR hybrid nitrogen oxide reduction system of the first aspect, wherein urea water sprayed from a two-fluid spray nozzle in a SNCR facility performs a urea decomposition reaction A first step of controlling (CONTROL) the degree of unreacted NH ₃ slip generation while performing a NOx reduction reaction of the NOx-containing combustion gas by the ammonia generated by the urea decomposition reaction of urea water and generating ammonia; Alternatively, a first step of controlling (CONTROL) a degree of unreacted NH ₃ slip generation while performing a NOx reduction reaction of NOx-containing combustion gas by an NHx-based reducing agent injected from a two-fluid spray nozzle in a SNCR facility; and a second step of performing a selective catalytic reduction (SCR) process in an SCR facility while using unreacted NH ₃ slip generated in the SNCR facility as a reducing agent for NOx.

A third aspect of the present invention provides a cement manufacturing method characterized by treating NOx-containing combustion gas generated from a combustion furnace and/or preheater during the cement manufacturing process with the SNCR-SCR hybrid nitrogen oxide reduction system of the first aspect. do.

At this time, the cement manufacturing method may be to perform the NOx-containing combustion gas treatment method of the second aspect.

Hereinafter, the present invention will be described.

In the present specification, 'NHx-based reducing agent' refers to a reducing agent that contains an NHx component and can generate NHx that can selectively reduce only NOx. urea), ammonium carbamate, pyridine, ammonium acetate, cyanuric acid, and ammonium carbonate.

As illustrated in FIG. 1, the present invention designs a SNCR-SCR hybrid nitrogen oxide reduction system to maximize the effect of increasing treatment efficiency, reducing construction costs, and reducing maintenance costs when NO _X is simultaneously dispersed and removed from the SNCR facility and the SCR facility It is characterized by

[ Selective non-catalytic reduction (SNCR) efficiency increase and leveling control ]

The present invention is a computational fluid analysis (CFD) of a _SNCR facility as illustrated in FIGS. It is characterized by selecting the point (s) where the NHx-based reducing agent injection nozzle is installed using .

For example, when urea water is thermally decomposed to produce ammonia at a temperature of 850 to 1,050 ° C, preferably 900 to 1,000 ° C inside the combustion furnace and / or preheater, denitrification efficiency is usually 30 to 50%.

In addition, in order to increase the efficiency of the selective non-catalytic reduction (SNCR) and control the leveling, the present invention sprays the NHx-based reducing agent to the point (s) where the dust is not concentrated and the temperature is uniform through computational fluid analysis (CFD) of the SNCR facility It is characterized by the installation of a nozzle.

At points where the dust is biased, does not come down uniformly, or the temperature is not uniform, the NHx-based reducing agent droplets sprayed from the NHx-based reducing agent injection nozzle are hydrodynamically disturbed, so it is impossible to control the leveling of NOx removal efficiency in the NHx-based reducing agent droplets. This is because the NOx efficiency may decrease.

In this specification, “the point(s) where the NHx-based reducing agent injection nozzle is installed” refers to the point where the NHx-based reducing agent injection nozzle is installed through the computational fluid analysis (CFD) of the SNCR facility. During the residence time of the NHx-based reducing agent droplets sprayed from the reducing agent injection nozzle, the temperature may be uniform within a range within which the NHx-based reducing agent droplets can reach.

In this specification, “the point (s) where the NHx-based reducing agent injection nozzle is installed and the dust is uniformly descended without bias” is the point where the NHx-based reducing agent injection nozzle is installed through computational fluid analysis (CFD) of the SNCR facility Based on , dust in the exhaust gas may not be biased within a range where the NHx-based reducing agent droplets can reach during the residence time of the NHx-based reducing agent droplets sprayed from the NHx-based reducing agent injection nozzle.

[Using unreacted NH ₃ slip generated in SNCR facility as NOx reducing agent in SCR facility ]

The present invention is characterized in that the unreacted NH ₃ slip generated in the SNCR facility is used as a NOx reducing agent in the selective catalytic reduction (SCR) at the later stage.

In the selective non-catalytic reduction (SNCR), the optimal temperature of the reducing agent is 870 to 1,000 °C for ammonia and 900 to 1,030 °C for urea solution. Normally, SNCR facilities show denitrification efficiency of 30 to 50% in NOx reduction efficiency in the reaction temperature range of 850 ~ 1,030 ℃, but in the low temperature range, the reducing agent does not react efficiently and ammonia slip occurs. am.

Factors affecting the NOx removal rate in SNCR are the reaction temperature (850 ~ 1030 ℃), the shape and location of the nozzle, the residence time of the combustion gas, and the standard stoichiometric ratio of the reducing agent (NSR, [NH ₃ ] _{reducing agent} / [NOx ]), etc., the main process variables affect the NOx reduction efficiency.

Therefore, the present invention can increase the amount of NHx-based reducing agent injected by greatly adjusting the droplet particle size through the two-fluid spray nozzle so that unreacted ammonia (ammonia slip) is generated in the SNCR facility.

That is, in the present invention, in order to control the degree of unreacted NH ₃ slip generation in a SNCR facility, the droplet particle size is adjusted through a two-fluid spray nozzle to control the amount of NHx-based reducing agent injection and thus the degree of unreacted NH ₃ slip generation. there is.

In addition, in SNCR, the reaction temperature is important, and if the reaction temperature is low, the NOx reduction reaction rate is slow, so that unreacted ammonia (ammonia slip) is generated. The temperature of the droplets of the NHx-based reducing agent sprayed through can be adjusted to a low level.

To this end, the NHx-based reducing agent injection nozzle used in the SNCR facility is concentrically arranged outside the NHx-based reducing agent injection pipe and the compressed air injection pipe, and extends to the nozzle tip, but the cooling fluid flowing in the inner space is sprayed through the nozzle cap It may be a two-fluid spray nozzle additionally equipped with a cooling fluid injection pipe for nozzle protection.

In this case, as illustrated in FIG. 4 , when the cooling fluid is injected from the cooling fluid injection pipe for nozzle protection near the nozzle tip, a shield that blocks the flow of dust flowing into the vicinity of the nozzle tip due to the expansion of the injected cooling fluid An insulating shield layer may be formed that retards the heating of NHx-based reducing agent droplets sprayed through the layer and/or nozzle cap.

In general, the residence time of the reducing agent droplet in the SNCR facility is appropriate for 1 second or more, and the NSR is 0.5 to 1.5 in the region where ammonia slip does not occur. Therefore, the present invention can adjust NSR to 1.5 or more so that ammonia slip occurs.

[ SNCR Facility ]

In the present invention, a combustion furnace and/or a pre-heater in which NOx-containing combustion gas is generated by a combustion reaction during the cement manufacturing process may have a kiln-type reactor as illustrated in FIGS. 1 and 3 .

There are four types of kiln used in the cement manufacturing process: wet kiln, dry kiln, preheater kiln, and precalciner kiln. While wet and dry kilns have one fuel firing zone, preheater and precalciner kilns have two firing zones, a firing zone and a secondary firing zone. Since the general temperatures in the two firing zones are different, the factors affecting NOx generation are also different.

The generation of thermal NOx in the kiln firing zone depends on the temperature of the firing zone, the gas residence time, and the oxygen concentration in the high-temperature firing zone. The temperature of the firing zone is affected by the type of fuel being burned. In general, the flame temperature affecting the firing zone temperature is stronger for gas burners than for coal burners. Since the nitrogen content of coal is higher than that of gas, the amount of Fuel NOx generated from the coal burner is high, but since the flame temperature of the gas burner is high, the generation of Thermal NOx is higher, and as a result, the amount of NOx generated from the gas burner is higher. Flame shape and theoretical flame temperature are important factors for thermal NOx formation. A long, slow-flowing flame produces less NO than a short, strong flame. The shape of the flame is determined by the air ratio as well as the fuel.

Since the production of NOx is promoted when the oxygen concentration is high, the production of NOx is affected by the amount of excess air and the concentration of oxygen. When the amount of excess air increases, the amount of NOx produced increases to some extent, but when it exceeds that amount, the flame temperature decreases as the supply of secondary air increases, so it does not have a large effect. The oxygen concentration in the firing zone depends not only on the total excess air, but also on the ratio of primary to secondary air. In the direct firing system, a large amount of air is burned together with the fuel. This combustion method is characterized by high oxygen concentration or low fuel combustion. and/or pre-heater There is a contradictory effect between the side that generates a lot of NOx and the side that generates less NOx because the flame temperature is low. On the other hand, in the indirect firing system, since a small amount of air is used for combustion, less primary air is used, so the amount of NOx generated is lower than that of the direct combustion system. The lower the temperature of the secondary air and the higher the dust content in the secondary air, the lower the NOx formation in the kiln firing zone. NOx production can be reduced by blowing moist primary air and cement kiln dust (CKD) into the firing zone.

Process conditions such as temperature stability, plasticity of raw materials, alkali and sulfur control also affect NOx formation. Temperature stability is important to maintain clinker quality and achieve stable flame conditions and energy efficiency. The clinker formation reaction requires a flame temperature of 2,600 ° C or higher and an oxidizing atmosphere. Excess air used for combustion has a significant impact on NOx emissions. An oxygen concentration of 4 to 5% in exhaust gas means that NOx emissions will increase, and an oxygen concentration of 0.5 to 1.5% means that NOx emissions will decrease. Because of this, the amount of NOx emitted from the kiln is affected by the excess oxygen required to maintain the quality of the clinker produced.

The calorific value of the fuel can also affect NOx formation. Fuels with high calorific value, such as petroleum coke, require less combustion air and therefore produce less NOx per unit of clinker produced.

Different raw material components require different firing conditions to maintain the proper quality of the clinker produced. For this reason, even in the same type of kiln, the NOx emission level differs depending on the raw material composition, and the alkali content of the raw material can also affect NOx production.

The temperature range of the secondary firing zone of the preheater and calciner is 820~1030℃. Some of the nitrogen contained in the fuel reduces NO in the kiln flue gas to eliminate NO, and some reacts with oxygen to form NO.

If there is a lot of volatile matter in the middle of the solid fuel, when the temperature of the second firing zone is increased, the actual production of NO is lowered. When calcination is performed using tertiary air, generally only 40 to 50% of the fuel is burned in the kiln, so the amount of combustion gas discharged from the high-temperature kiln is reduced in proportion to the amount of NOx produced. In addition, since the thermal efficiency is improved when the calciner is installed, the amount of fuel used is reduced and the total amount of NOx produced is also reduced.

Since the formation of NOx is directly related to the combustion of fuel, the emission of NOx per unit cement production can be reduced if the amount of fuel used per unit cement production is reduced. To increase the energy efficiency of the cement manufacturing process, avoid excessive clinker firing and use waste heat to preheat combustion air, coal and fuel. In addition, when heat transfer between hot gas and solid is increased, thermal efficiency also increases. The preheater and precalciner kiln were developed for this purpose. Most recent cement factories produce cement using this kiln.

Meanwhile, in the present invention, the NOx reduction reaction of the NOx-containing combustion gas by ammonia generated by the urea decomposition reaction of the urea water droplets injected through the NHx-based reducing agent injection nozzle may be a selective non-catalytic reduction (SNCR) method.

Urea is colorless, odorless, and has little toxicity, so it is easy to store. In this case, secondary contamination by unreacted ammonia can be reduced. In addition, since urea is a colorless, odorless crystal that dissolves well in water, it can be used as a reducing agent in place of highly toxic ammonia.

Urea (NH ₂ ) ₂ CO) is decomposed into ammonia in the following process.

Urea → Biuret + Ammonia (One)

Urea → Cyanuric + Ammonia (2)

Biuret → Cyanuric + Ammonia (3)

Biuret → Cyanuric + Amminia (4)

In order to actually use urea solution as a reducing agent for nitrogen oxide reduction, urea ((NH ₂ ) ₂ CO) dissolved in water is subjected to the following thermal decomposition reaction and thermal hydrolysis under a temperature environment of 300 ° C or higher. Accompanied by the reaction, it is converted to ammonia and reacts with nitrogen oxides.

NH ₂ CONH ₂ + H ₂ O → NH ₄ COONH ₂

NH ₄ COONH ₂ + H ₂ O → 2NH ₃ + CO ₂ + H ₂ O

The DeNOx reaction of urea can be expressed as follows.

2 NH ₂ CONH ₂ + 4 NO +O ₂ → 4 N ₂ + 4 H ₂ O + 2 CO ₂

4 NH ₂ CONH ₂ + 6 NO +O ₂ → 7 N ₂ + 8 H ₂ O + 4 CO ₂

As for urea, the NOx removal efficiency is greatly affected by the process conditions, and the factor affecting the NOx removal rate in SNCR is the residence time, and the residence time is preferably 1 second or more.

The urea decomposition reaction of urea water may include a thermal hydrolysis reaction represented by Scheme 2 and/or a thermal decomposition reaction represented by Scheme 3.

[Scheme 2]

NH ₂ CONH ₂ + H ₂ O + heat + time → NH ₄ COONH ₂ + H ₂ O → 2NH ₃ + CO ₂ + H ₂ O

[Scheme 3]

NH ₂ CONH ₂ + Heat + Time → NH ₃ + HNCO

Therefore, it is preferable that the temperature of the region where the urea water droplets are directly injected from the urea water injection nozzle is equal to or higher than the temperature at which the urea water can be thermally decomposed.

The temperature of the region where the urea water droplets injected from the urea water spray nozzle or the urea decomposition reaction of the urea water occurs may be 850 to 1030 °C.

In order for the NOx reduction reaction to occur simultaneously by the selective noncatalytic reduction method (SNCR), the temperature of the region where the urea water droplets injected from the urea water injection nozzle or the urea decomposition reaction within the urea water droplets occurs is 900 to 1030 ° C. In this case, ammonia may be generated by thermal decomposition of urea water by directly spraying the urea water into a high-temperature reaction region capable of thermally decomposing urea water through the two-fluid spray nozzle for spraying urea water of the present invention.

In general, urea water spray nozzles are mainly used as two-fluid spray nozzles that spray liquid with the power of compressed air by mixing liquid and gas inside or outside, respectively. The Air Atomizing Nozzle creates a fine spray form by externally mixing gas and liquid. The types of nozzles that can be used as urea water injection nozzles vary according to the mixing method of urea water and compressed air and the structure and shape of the nozzle.

The urea water injection nozzle may be installed through the combustion furnace and/or the wall of the preheater. In this case, the urea decomposition reaction of the urea water injected from the urea water injection nozzle in the furnace and/or the preheater and the NOx reduction reaction occur simultaneously by the selective non-catalytic reduction (SNCR). That is, while NOx-containing combustion gas is generated or supplied by a combustion reaction in a combustion furnace and/or a preheater, a NOx reduction reaction by selective non-catalytic reduction (SNCR) occurs.

In the SNCR facility, one or more urea water injection nozzles may be provided. For example, in the SNCR process, since the mixing of the reducing agent and combustion exhaust gas has a great effect on the NOx reduction efficiency, it is desirable that urea, the reducing agent, be sprayed evenly throughout the reaction section. Thus, the number of nozzles can be limited.

In order to maintain the residence time of the urea water droplets injected from the urea water injection nozzle in the SNCR facility according to the present invention at least 1 second and/or to control the generation of unreacted ammonia (ammonia slip), a two-fluid for urea water injection It is preferable to adjust the size of droplets of urea solution through the spray nozzle to be 100 μm or more, preferably 300 μm or more.

Unlike existing nozzles, the urea solution spray nozzle, which can be developed and used specifically for the cement manufacturing process, sprays droplets with a droplet size of 100㎛ or more, preferably 300㎛ or more, and due to the characteristics of cement manufacturing facilities, the flow rate is typical for general facilities (3-15m / sec), it is preferable to make the size of the droplet particles of urea water very large to match the characteristics of the very fast flow rate (20-30 m.sec).

The droplet particle size can be greatly controlled by increasing the amount of urea water sprayed through the two-fluid spray nozzle. The two-fluid nozzle used as a urea water spray nozzle sprays urea water, which is a reducing agent, together with compressed air to atomize urea water and sprays the urea water. Specifically, in the two-fluid fine spray nozzle, the liquid is sprayed while pulverizing the diluted urea solution liquid stream sprayed from the liquid nozzle cap at the center of the nozzle while the gas is sprayed from the gas nozzle cap disposed at a slight angle.

The two-fluid nozzle injects compressed air together with the liquid to make the particle size of the liquid droplet more than 100 μm and sprays it, so that fine particles penetrate the target gas layer to help mixing with the gas layer and improve reactivity.

The urea water spray nozzle is a rear mixing type nozzle that mixes and sprays compressed air and urea water inside the nozzle; and for atomization of urea water, compressed air and urea water are injected along each pipe and mixed at the outlet of the nozzle. There is a front mixing type nozzle that is sprayed by spraying.

As illustrated in FIG. 4, the rear mixing type nozzle that mixes and sprays compressed air and urea water inside the nozzle has a simple internal structure and sprays with the size of the discharge port and the spray pressure suitable for the injection amount of urea water.

In the case of the shear mixing type two-fluid spray nozzle for spraying urea water, a nozzle tip (b) equipped with a nozzle cap for gas and a nozzle cap for liquid is attached to the front of the nozzle body (a) to adjust the flow rate of gas and liquid and spray shape can be adjusted. The liquid flow rate, the gas flow rate, and the spraying shape can be ultimately controlled by a combination of various gas nozzle caps and liquid nozzle caps. The liquid flow rate and the gas flow rate can be individually adjusted.

For example, according to the present invention, a two-fluid spray nozzle for spraying urea water installed in a combustion furnace and/or a preheater generating NOx-containing combustion gas by a combustion reaction

(a1) a urea solution injection pipe for providing urea solution to a nozzle cap;

(a2) a compressed air injection pipe that is concentrically inserted into or outside the urea water injection pipe and provides compressed air fluid to the nozzle cap; and

(a3) A cooling fluid injection pipe for nozzle protection that is concentrically arranged outside the urea water injection pipe and the compressed air injection pipe and extends to the nozzle tip, but the cooling fluid flowing in the inner space is not injected through the nozzle cap.

A nozzle body (a) having a; and

A nozzle tip (b) having a nozzle cap and providing a discharge port to adjust the shape of the sprayed urea water droplets;

may be provided.

At this time, the path of the urea water fluid flowing in the inner space of the urea water injection pipe (a1), the path of the compressed air fluid flowing in the inner space of the compressed air injection pipe (a2), and the cooling fluid injection pipe (a3) for nozzle protection in the inner space The paths of the flowing cooling fluid are parallel to each other.

As illustrated in FIG. 4, in the case of a rear mixing type nozzle in which compressed air and urea water are mixed and injected inside the nozzle, the present invention provides a urea water injection pipe (a1) for providing urea water fluid and compressed air fluid Among the compressed air injection pipes (a2), the injection pipe concentrically located on the outside extends and is connected to the nozzle cap, and the injection pipe located on the inside concentrically does not extend to the nozzle cap, and the injection pipe located on the outside Provided in, the urea water fluid and the compressed air fluid are mixed in the injection pipe located outside to the nozzle cap and provided to the discharge port of the nozzle cap.

In the two-fluid spray nozzle for spraying urea water, urea water is sprayed in the form of a liquid stream from the outlet of the nozzle cap, and the urea water liquid stream is pulverized and sprayed by the expansion of compressed air sprayed from the outlet of the nozzle cap.

The compressed air supplied to the nozzle cap through the compressed air injection pipe may preferably be compressed cooling gas. The compressed air injected through the nozzle cap not only serves as a carrier gas for the sprayed urea solution droplets, but also the cooling gas flowing through the compressed air injection pipe serves to cool the nozzle.

The cooling fluid flowing in the inner space of the cooling fluid injection pipe for protecting the nozzle may be a gas (eg, cooling air) or a liquid. An example of a cooling fluid for nozzle protection is cooling air.

Compressed air and / or (diluted) urea water can be supplied to the compressed air injection pipe and the urea water injection pipe, respectively, by sufficiently pressurizing it with a pump or the like. The pressurized urea solution fluid may reach the urea solution nozzle cap through the urea solution injection pipe by pump pressure.

If necessary, the cooling fluid may be sufficiently pressurized by a pump or the like and supplied to the cooling fluid injection pipe for nozzle protection, and the cooling rate may be adjusted by adjusting the flow rate. Heat insulation that slows down the heating of urea water droplets injected through the nozzle cap by the expansion of the injected cooling fluid when the cooling fluid under pressure is injected from the cooling fluid injection tube for nozzle protection near the nozzle tip, even though it is not injected from the discharge port of the nozzle cap. The shield layer can be thickened.

In some cases, while the cooling fluid injection pipe for nozzle protection is separated from the two-fluid spray nozzle for urea water spray and mounted on the wall of the combustion furnace and/or the preheater, the remaining two-fluid spray nozzle for urea water spray is for nozzle protection. It may be inserted or detached concentrically into the cooling fluid injection pipe.

For example, the two-fluid spray nozzle for spraying urea water described in Korean Patent Application No. 10-2021-0158486 can be used, and the contents described in Korean Patent Application No. 10-2021-0158486 are incorporated herein.

In one embodiment of the present invention, in the two-fluid spray nozzle for spraying urea water, a cooling fluid injection pipe for protecting the nozzle may be installed by penetrating the wall of the combustion furnace and/or the preheater to extend in the longitudinal direction. As illustrated in FIG. 4, outside the combustion furnace and/or the preheater, the two-fluid spray nozzle for urea water injection is disposed closest to the nozzle tip (b) of the cooling fluid injection port of the cooling fluid injection pipe for nozzle protection, , thereafter, a urea water inlet or a compressed air inlet is disposed. The urea water inlet and the compressed air inlet are the same as the existing two-fluid nozzle that sprays the necessary chemicals by injecting liquid and air into the nozzle.

The cement manufacturing process has a dust content of 60 to 100 g/Nm ³ , which is 10,000 times higher than that of general facilities (10 mg/Nm ³ ). It is preferable to use two-fluid spray nozzles for spraying urea water, which are concentrically arranged and extend to the nozzle tip, but are additionally provided with a cooling fluid injection pipe for nozzle protection in which the cooling fluid flowing in the inner space is not sprayed through the nozzle cap. do.

This structure of the cooling fluid injection pipe for nozzle protection serves as a shield to protect the nozzle tip from dust, thereby minimizing clogging caused by a large amount of dust. For example, an end of a cooling fluid injection pipe for nozzle protection is protruded from the front of the nozzle tip and can serve as a shield that can minimize clogging of the nozzle tip by dust. Alternatively, as illustrated in FIG. 4 , when cooling fluid is sprayed from a cooling fluid injection tube for nozzle protection near the nozzle tip, the flow of dust flowing into the vicinity of the nozzle tip may be hindered by the sprayed cooling fluid. In this case, the cooling fluid injection pipe for protecting the nozzle may serve as a shield to protect the nozzle tip from dust even when the cooling fluid injected does not extend to the end of the nozzle tip.

According to one embodiment of the present invention, in the cooling fluid injection pipe for nozzle protection disposed concentrically outside the urea water injection pipe and the compressed air injection pipe and extending to the nozzle tip, the cooling fluid flowing in the internal space is injected through the nozzle. When the temperature of the water droplets is controlled to be low and/or the cooling fluid is injected from the cooling fluid injection tube for nozzle protection near the nozzle tip as illustrated in FIG. 4, the urea water injected through the nozzle cap by the injected cooling fluid By suppressing the heating of the droplets, the urea solution droplets within the residence time can be controlled so that they are in the temperature window showing the optimal efficiency in SNCR.

In particular, the urea water and compressed air may be cooled to a temperature lower than the wall temperature so that the urea water injection pipe and the compressed air injection pipe are not heated while penetrating the wall of the furnace and/or the preheater.

By adjusting the temperature of the injected urea water droplets to be low, the present invention is carried out at a low temperature so that ammonia is produced by urea decomposition reaction of urea water and NOx reduction reaction of NOx-containing combustion gas occurs by ammonia by diffusion farther within the residence time. It may be to adjust the size of the urea solution droplets as large as 100 μm or more, preferably 300 μm or more.

The inner diameter of the urea water injection pipe may be 10 mm or less, and the inner diameter of the outlet of the compressed air nozzle cap may be 1 mm or more. In this case, when spraying a large amount of urea water of 500 kg/hr or more, the size of the urea water spray droplets can be controlled to 100 μm or more, preferably 300 μm or more. At this time, it is effective to set the injection pressure of the compressed air to 2 to 4 bar or more.

During the cement manufacturing process, the amount of dust in the combustion furnace and/or the pre-heater where NOx-containing combustion gas is generated by the combustion reaction is 1g/Nm ³ or more, 10,000 times the normal facility (10mg/Nm ³ ), 10g/Nm ³ or more, For example, it is 60-100 g/Nm ^<3> .

The above-described cooling fluid flowing in the inner space of the cooling fluid injection pipe for protecting the nozzle is connected to the nozzle tip by a double pipe from the cooling fluid (eg, cooling air) injection port to achieve the main purpose of preventing the nozzle tip from deteriorating and protecting it from excessive dust. And the purpose of protecting the nozzle base can also be achieved.

Therefore, a combustion furnace and/or a preheater in which NOx-containing combustion gas is generated by a combustion reaction during the cement manufacturing process, to which the above-described two-fluid spray nozzle for spraying urea water is installed, can use industrial by-products as cement raw materials and/or fuel. can

[ Computational fluid analysis (CFD) ]

The present invention is a NOx reducing agent in the selective catalytic reduction (SCR) at the rear, while exhibiting a _NOx reduction rate of 40 to 50% through selective non-catalytic reduction (SNCR) efficiency increase and leveling control. In order to design a SNCR facility that controls (CONTROL) the degree of unreacted NH ₃ slip generation to be used, the point(s) where the temperature is uniform while the dust descends uniformly without being biased through computational fluid dynamics (CFD) ) is characterized by installing an NHx-based reducing agent spray nozzle.

Computational Fluid Dynamics (CFD) is a method of analyzing and reviewing the field of environmental facilities as a theoretical study instead of experimental research due to physical limitations. Through CFD review, it is possible to simulate the current state of existing facilities, derive problems, and verify the effect after improvement, and minimize trial and error in the pre-design stage and enable efficient operation.

In the present invention, the gas composition of each inlet and outlet (NO _X , O ₂ , CO, Temp.), PREHEATER outlet gas composition (NO _X , O ₂ , Co, Temp, SO _X , Dust), temperature, amount of dust, and particle size of dust are identified to collect basic data, and then computational fluid analysis is performed for each KILN TYPE as illustrated in FIG. 2 through 3D work. Through this, the direction and temperature range of the fluid can be confirmed.

In order to select the expected nozzle location that provides an ideal method for reducing fine dust including NOx in a SNCR facility, through the above-described computational fluid analysis, NHx-based reducing agent and to provide spray nozzle installation point(s) (Example 1).

Similarly, as illustrated in FIG. 6, the SCR facility can also perform CFD analysis (flow rate/temperature/concentration).

In the SCR facility to be described later through CFD analysis, ammonia spray nozzle design (e.g. nozzle shape, quantity and spray method selection, spray pressure selection (spraying, cooling air spray amount and supply pressure selection)), temperature/exhaust gas/dust characteristics SCR catalyst selection and catalyst tower design can be performed. Furthermore, it is possible to design catalysts and catalyst towers according to flow conditions.

[ Cyclone ( Cyclone )]

In order to reduce the risk of abrasion and damage of the catalyst when reducing nitrogen oxides under high dust conditions, extend its lifespan, and prevent dust from depositing on the catalyst and degrading the catalyst's activity, the exhaust gas is used at the rear end of the SNCR facility and the SCR facility Cyclones can be installed between the shears.

According to one embodiment of the present invention, a cyclone is installed at the front of the SCR facility that reduces nitrogen oxides generated in the cement manufacturing process to prevent a rise in differential pressure of the catalyst and abrasion of the catalyst through reduction of dust attached and deposited on the SCR catalyst This can prolong the life of the catalyst. Through this, more efficient nitrogen oxide reduction in SCR facilities is possible.

In order to selectively collect/remove dust particles from the dust and ammonia slip-containing mixed gas discharged from the SNCR facility, the dust particles are primarily collected by gravity fall in a cyclone device without a separate cooling process and, if necessary, a filter Dust can be collected secondarily through a filter bag.

A cyclone device for collecting/removing dust particles discharged from a SNCR facility may include an inlet, a cyclone tank body, a dust discharge hopper, and a discharge port extending from the center of the cyclone tank body to the outside of the cyclone tank. .

A cyclone gives a swirling flow (vortex) to the fluid in which particles are suspended, so the particles are separated from the flow by the centrifugal force and gravity that accelerate the particles, collide with the inner wall of the body (body) and fall down, and the fluid is caused by the vortex effect. It uses the principle of being discharged by rising in reverse flow from the center (FIG. 10).

The structure of the main body of the cyclone tank is designed to collect dust fine particles by applying the gravity fall method.

A cyclone is simple, with no moving parts, just a room to create swirling flow in the fluid. High-temperature gas and high-concentration gas treatment are also possible, and the range of use can be broadened by connecting in series or parallel without being greatly restricted in the installation place.

When the mixed gas containing dust fine particles discharged from the SNCR facility is supplied to the main body of the cyclone tank as a swirling flow through the inlet, the fine dust particles are separated from the flow by the accelerated centrifugal force and gravity, collide with the inner wall, and fall down through the discharge hopper. The collected fluid from which some of the dust particles have been removed may be discharged through the discharge port by rising in reverse flow from the center by the swirling flow effect.

The inlet is designed so that the mixed gas containing particulate matter can be supplied in a vortex.

The tank body is designed to have sufficient residence time for the incoming gas, and is preferably made of STS304 material to prevent deformation or twisting during operation.

[ NOx reducing agent for SCR facilities ]

As described above, the present invention is characterized in that unreacted NH ₃ slip generated in the SNCR facility is used as a reducing agent for NOx in the selective catalytic reduction (SCR) at the later stage.

The present invention aims to reduce costs while unifying the dualized reducing agent supply facility in the SNCR-SCR hybrid nitrogen oxide reduction system by using the same reducing agent as the SNCR facility in the SCR facility, and also considering the characteristics of the number of elements that require vaporization energy, SNCR It is characterized by controlling and supplying the amount of NH ₃ reducing agent required in the SCR facility by installing a urea water injection nozzle in an appropriate temperature range (450℃∼550℃) within the facility.

In addition, the present invention relates to a reducing agent for reducing nitrogen oxides in an SCR facility (1) an unreacted ammonia slip contained in NOx-containing exhaust gas discharged after reducing nitrogen oxides by an NHx-based reducing agent supplied from a SNCR facility at the front and necessary Case (2) It is characterized in that the reducing agent can be supplied in one or two ways in the SNCR-SCR hybrid nitrogen oxide reduction system through the injection of ammonia water in the SCR facility.

SCR decomposes NOx into harmless N ₂ and H ₂ O through a reducing agent. Reducing agents used in the SCR reaction can be classified into HC-SCR using hydrocarbon, H ₂ -SCR using hydrogen, and NH ₃ -SCR using ammonia.

Ammonia (NH ₃ ) is a reducing agent mainly used in the currently commercialized catalytic reduction process (SCR) because its selectivity for NO is superior to other types of reducing agents (hydrocarbons and carbon monoxide). However, NH ₃ has disadvantages in that it is highly toxic, corrodes various equipment, and requires high costs for storage and transportation. In order to solve this problem, the present invention controls the amount of reducing agent required in SCR by installing a SNCR nozzle in a section where the temperature is appropriate (450 ° C to 550 ° C) in the preheater in consideration of the characteristics of the number of elements requiring vaporization energy can supply

[ SCR Catalyst ]

In the SCR facility according to one embodiment of the present invention, the catalyst layers may be vertically spaced stacked in multiple stages as illustrated in FIG. 8 .

Metals used for metal oxide catalysts include V, Fe, W, Cu, Mo, Mn, Ce, Ni, Sn, and the like in order of frequency of use. Also, the reactivity between metals or their compounds and nitrogen oxides is Pt, MeO ₂ , CuO, Fe ₂ O ₃ , Cr ₂ O ₃ , Co ₂ O 3 , MoO ₃ , NiO, _{WO 3 ,} Ag ₂ O, ZrO ₂ , Al Reactivity decreases in the order of ₂ O ₃ , SiO ₂ , and PhO. Metal oxide catalysts use a mixture of two or more metals or compounds that are highly reactive with nitrogen oxides. Examples of frequently used catalysts include V ₂ O ₅ -Al ₂ O ₃ catalyst, V ₂ O ₅ -SiO ₂ -TiO ₂ catalyst, Pt catalyst, WO ₃ -TiO ₂ catalyst, Fe ₂ O ₃ -TiO ₂ catalyst, CuO-TiO ₂ catalyst, and CuO-Al ₂ O ₃ catalyst. The most commonly used catalysts for SCR are the V ₂ O ₅ -Al ₂ O ₃ catalyst and the V ₂ O ₅ -TiO ₂ catalyst.

NH ₃ -SCR is a technology that can remove more than 90% of NOx emitted from stationary sources, and is the best available control technology (BACT) among NOx control technologies to date in terms of price competitiveness and stability of catalytic activity. is in commercialization.

Catalysts used in NH ₃ -SCR can be largely classified into noble metal catalysts, metal oxides, and zeolites in which Cu or Fe is ion-exchanged. An NH ₃ -SCR catalyst containing a noble metal element as an active component shows excellent NOx removal efficiency at a low temperature of 250 °C or less. Among the zeolite catalysts, the most representative types used for NH ₃ -SCR include Cu-ZSM5 and Fe-ZSM5 catalysts in which Cu or Fe is ion-exchanged. Cu-ZSM5 exhibits excellent activity at 200-300 °C, and Fe-ZSM5 exhibits relatively good activity at high temperatures of 500 °C or higher. However, zeolite catalysts have problems such as deterioration of activity due to moisture, deterioration of activity due to SO ₂ , and deterioration of activity due to hydrocarbons present in exhaust gas. The metal oxide catalyst used in NH ₃ -SCR includes manganese oxides, cerium oxides, tungsten oxides, and vanadium oxides as active components, TiO ₂ and Al ₂ O as supports. There are catalysts prepared by being supported on ₃ , etc. A catalyst using manganese oxide and cerium oxide shows superior catalytic activity at a low temperature of 250 ° C or less than a VOx/TiO ₂ catalyst using vanadium oxide as an active component, and this is called a low-temperature SCR catalyst (LTC). It is known that these catalysts have a very large deactivation effect by SO ₂ compared to their excellent activity at low temperatures, and that the catalyst activity of catalysts containing manganese oxide as an active component is greatly reduced by moisture contained in exhaust gas. On the other hand, the VOx/TiO ₂ catalyst in which vanadium oxide is added as an active component to TiO ₂ as a support exhibits excellent NOx removal efficiency at a temperature of 250-400 ° C, and is different from other catalysts in terms of activity reduction due to moisture and durability against SO ₂ It shows very good performance compared to catalysts. For this reason, VOx/TiO ₂ -based catalysts are widely used for commercial purposes.

The SCR process can obtain a removal efficiency of more than 90% in the temperature range of 300 ~ 450 ℃ when using the Pt-V ₂ O ₅ /TiO ₂ catalyst. However, in the SNCR-SCR hybrid nitrogen oxide reduction system according to the present invention, a catalyst capable of catalytic activity in a temperature range of 200 to 250 ° C. lower than the above temperature conditions can be selected and used. This is because if a removal efficiency of 45% to 50% or more can be obtained in an SCR facility, it is possible to comply with domestic environmental regulations. In addition, in the SNCR-SCR hybrid nitrogen oxide reduction system according to the present invention, it is possible to derive and apply optimal conditions for selecting a catalyst amount.

SCR catalysts are classified into pellet-type catalysts, plate-type catalysts, corrugate-type catalysts, and monolith extrusion catalysts according to their shape and manufacturing method (FIG. 7).

Pellet-type catalysts can be applied when miniaturizing SCR reactors, and are applicable to special conditions due to their excellent applicability/manufacturability of SCR reactors. Due to the use of a pellet-type catalyst, the size of the SCR facility can be reduced. However, it is vulnerable to maintenance, and there is a problem of clogging by dust / high cost.

In the plate-type catalyst, after coating a catalytically active material on a metal mesh support, a plate-shaped catalyst cartridge with a bent surface is manufactured, and each cartridge is fitted to form a catalyst block. Since the exhaust gas flows through the gap between the plate catalysts, the reaction area per unit volume is low, and it is a catalyst that requires a very large installation area due to the increase in catalyst volume. However, since the catalyst has excellent thermal and mechanical durability and low pressure loss due to the catalyst, it is mainly used in coal-fired power plants with a lot of particulate matter in exhaust gas.

Corrugate-type catalysts are prepared by preparing a corrugated carrier made of ceramic or glass fibers and then coating the carrier with a slurry containing a catalytically active material. It has the advantages of a short catalyst production period, light weight, and a large reaction area per unit volume, but has low mechanical strength and durability, making it difficult to apply it as a pollutant emission source with a large amount of fly-ash in exhaust gas.

Plate-type catalysts and corrugate-type catalysts can operate at low differential pressure, are resistant to clogging by dust, have low cost, but have a large amount of catalyst and are vulnerable to abrasion due to their small surface area. This is a much needed catalyst.

The honeycomb type monolith extruded catalyst is an integral structure, and the inside and outside of the catalyst are made of the same material, so the composition is the same in any part, and the opening of the catalyst can be manufactured in various geometric shapes. In addition, it has excellent performance, strong abrasion resistance, stability, good reproducibility, small equipment size, and lower cost than pellet-type catalysts. It shows the highest reaction area per unit volume among the three catalyst shapes, and has the advantage of easy catalyst regeneration, but the catalyst production period is long, and its durability is intermediate between plate and corrugate catalysts.

In general, the catalyst used in SCR is a honeycomb type and is more economical because of its large geometric surface area. The basic raw material for maintaining the shape of the catalyst is titanium dioxide (TiO ₂ ), and vanadium pentoxide (V ₂ O ₅ ) and tungsten trioxide (WO ₃ ) are added.

[ Installation of soot blower to remove dust in SCR facility ]

Gas turbines and thermal power plants produce dust of up to 10 g/Nm ³ , but the cement manufacturing process generates dust of up to 120 g/Nm ³ , making it difficult to reduce nitrogen oxides with a simple SCR system due to excessive dust. there is.

The volume of the SCR catalyst can be designed considering the amount of exhaust gas and dust during the cement manufacturing process.

As illustrated in FIGS. 6, 8, and 9, the SCR facility of the present invention installs a hopper at the bottom of the SCR reactor together with the application of a soot blower, and the reaction product of dust and SO ₃ is discharged through the soot blower to the catalyst layer. It can be collected by designing the process so that it does not adhere to the exhaust gas flow and falls off the flue-gas flow.

For example, the SCR facility performs selective catalytic reduction (SCR) on dust and NOx-containing exhaust gas and ammonia gas, but for the exhaust gas flow continuously flowing through the fixed catalyst layer, a soot blower installed before and/or after the fixed catalyst layer By intermittently spraying compressed air through a soot blower to provide forward and / or reverse disturbance (FIG. 8),

(1) while suppressing the attachment or deposition of dust in the exhaust gas to the fixed catalyst layer,

(2) Oxygen gas, which is a reactant, is supplied as far as possible by intermittently injected compressed air, and reacts in the direction of removing or weakening the longitudinal reaction gas gradient in each fixed catalyst layer through intermittent forward and/or reverse disturbance. Mixing of the gases can be designed to increase the overall nitrogen oxide removal efficiency of the SCR reactor.

The SCR facility may be one in which two or more fixed catalyst layers are vertically spaced apart from the exhaust gas flow, and a plurality of soot blowers spraying compressed air at regular intervals from the catalyst layer are vertically disposed.

For example, in an SCR facility, catalyst layers are vertically spaced apart in multiple stages, and exhaust gas flow flows from the vertical bottom to the top of the catalyst layer,

The soot blower blows compressed air (1) in the same direction as the exhaust gas flow at the bottom of each catalyst layer or (2) in the same direction as the exhaust gas flow at the bottom of each catalyst layer and in the opposite direction to the exhaust gas flow at the top of each catalyst layer;

The soot blower may inject compressed air (1) in the same direction as the exhaust gas flow at the top of each catalyst layer or (2) in the same direction as the exhaust gas flow at the top of each catalyst layer and in the opposite direction to the exhaust gas flow at the bottom of each catalyst layer.

The soot blower injects compressed air for 10 to 30 seconds at intervals of 1 to 3 minutes for each catalyst layer arranged in multiple stages, and changes the time and/or differential pressure of the compressed air from the first catalyst layer to the last layer in the direction of exhaust gas flow. According to the system, automatic valves installed in each line can be sequentially injected under program control.

The pressure of the compressed air injected from the soot blower may be 5 to 9 kg _f / cm ² .

In particular, even if exhaust gas with a high air volume of 450,000 Nm ³ /hr or more containing 120 g/Nm ³ or more of dust generated in the cement manufacturing process passes through the SCR facility, compressed air is intermittently supplied through the soot blower. It may be designed to suppress wear of the SCR catalyst by dust by spraying forward and/or reverse. In addition, the soot blower can be continuously and repeatedly operated at the same time as the cement manufacturing process starts.

For example, in the present invention, when exhaust gas with a high air volume of 450,000 Nm ³ /hr or more containing 120 g/Nm ³ or more of dust generated in a cement manufacturing process passes through an SCR facility, a soot blower and/or a sonic horn Hone) through which dust-containing exhaust gas passes, and unpassed dust can be collected and discharged through a separate outlet.

In addition, the SCR facility may be installed before or after a cyclone, electric precipitation, or bag filter for dust removal.

[ SNCR-SCR Hybrid Nitrogen Oxide Reduction System ]

A method for treating NOx-containing combustion gas using the above-mentioned SNCR-SCR hybrid nitrogen oxide reduction system according to the present invention

In the SNCR facility, ammonia is generated by performing urea decomposition reaction of urea water injected from a two-fluid spray nozzle, and NOx reduction reaction of NOx-containing combustion gas is performed by ammonia generated by urea decomposition reaction of urea water. A first step of controlling (CONTROL) the degree of reactive NH ₃ slip generation; or

A first step of controlling (CONTROL) the degree of unreacted NH ₃ slip generation while performing a NOx reduction reaction of NOx-containing combustion gas by an NHx-based reducing agent injected from a two-fluid spray nozzle in a SNCR facility; and

The second step of performing selective catalytic reduction (SCR) in the SCR facility while using the unreacted NH ₃ slip generated in the SNCR facility as a reducing agent for NOx

includes

At this time, in the SNCR facility, it is preferable that the size of the NHx-based reducing agent spray droplet is 100 μm or more when spraying the NHx-based reducing agent.

The _NOx removal efficiency according to the integrated system construction is 80% or more, the residual NOx is 80~82ppm, and/or the SCR installation cost can be reduced due to high SNCR efficiency and reduced SCR load. Due to the above-described SNCR efficiency increase and leveling control, the SCR facility can minimize the amount of catalyst and use a low-temperature catalyst between 200 ° C and 300 ° C.

According to the present invention, when the above-mentioned SNCR-SCR hybrid nitrogen oxide reduction system is used, the exhaust gas generated during the cement manufacturing process is treated to reduce nitrogen oxides by a selective non-catalytic reduction method, and then the nitrogen oxides are reduced by a selective catalytic reduction method. NOx-containing combustion gas generated from the combustion furnace and/or pre-heater during the cement manufacturing process can be efficiently treated. In particular, even in a cement manufacturing process in which industrial by-products are used as cement raw materials or fuel, NOx-containing combustion gases can be efficiently treated.

As illustrated in FIG. 9, the SNCR-SCR hybrid nitrogen oxide reduction system equipped with 1) High Dust SCR, 2) Tail End SCR, and 3) Semi-Dust SCR can be designed with the following operating conditions and process sequence. there is.

1) High Dust SCRs

(i) Catalyst for 80 ~ 100g/Nm ³ (6um) dust

(ii) Catalysts for the temperature range between 200 °C and 350 °C

(iii) Process sequence: kiln → preheating room → SCR → raw material grinder (if the raw material grinder is not operated, the cooler passes through) → bag filter → manned blower

2) Semi Dust SCR

(i) Catalyst for 30~60g/Nm ³ (6um) dust

(ii) Catalysts for the temperature range between 200 °C and 350 °C

(iii) Design of Dust Collector

(iv) Kiln → Preheating room → Dust Collector → SCR → Raw material grinder (If the raw material grinder is not operated, the cooler passes through) → Bag filter → Manned blower

3) Low Dust (Tail End) SCR

(i) Catalyst for the temperature range between 200 ℃ and 250 ℃

(i) Auxiliary heat source for catalytic reaction (Steam or LNG)

(iii) Process sequence: kiln → preheating room → raw material grinder (when the raw material grinder is not operated, the cooler passes through) → bag filter → SCR → manned blower

The SNCR-SCR hybrid nitrogen oxide reduction system according to the present invention has an effect of increasing treatment efficiency, reducing construction costs, and reducing maintenance costs when _NOx removal efficiency is simultaneously dispersed and removed from SNCR and SCR. For example, through the SNCR-SCR hybrid nitrogen oxide reduction system according to the present invention, the _NOx removal efficiency according to the construction of the SNCR-SCR hybrid integrated system is more than 80%, that is, the treatment efficiency of about 50% in SNCR and about 50% in SCR NOx is 80~82ppm by maintaining the efficiency of 80 ~ 82ppm, and the SCR installation cost (catalyst usage reduction and SCR facility miniaturization, etc.) can be innovatively reduced due to high SNCR efficiency and SCR load reduction. In addition, by using the same reducing agent as the SNCR facility in the SCR facility, SNCR is used in the preheater (450℃∼550℃) section for the purpose of reducing costs while unifying the dual supply facilities and considering the characteristics of the number of elements that require vaporization energy. By installing a nozzle to supply urea water and supplying ammonia using thermal decomposition energy at the injection position to the SCR facility, the amount of reducing agent required in SCR can be controlled and supplied.

Also, although the location of SCR is different depending on 1) High Dust SCR, 2) Tail End SCR, and 3) Semi-Dust, the same applies to SCR-SCR hybrid.

1 is a schematic process diagram of a SNCR-SCR hybrid nitrogen oxide reduction system according to an embodiment of the present invention.
2 illustrates computational fluid analysis in a SNCR facility according to an embodiment of the present invention.
Figure 3 illustrates the installation position of the urea water injection nozzle selected through the computational fluid analysis of Figure 2.
4 is a conceptual diagram showing an operating principle through fluid flow of a urea water spray nozzle equipped with a cooling means that can be used in a SNCR facility according to one embodiment of the present invention.
5 is a flow chart (FLOW CHART) of a SNCR-SCR hybrid nitrogen oxide reduction system according to an embodiment of the present invention.
6 illustrates computational fluid analysis in an SCR facility according to an embodiment of the present invention.
7 illustrates pellet-type catalysts, plate-type catalysts, corrugate-type catalysts, and monolith extrusion catalysts.
8 shows a flow of spraying compressed air by applying a soot blower to the bottom and top of the SCR catalyst of the present invention, so that the flow of spraying compressed air is in the same direction as the exhaust gas flow according to the direction of the exhaust gas flow, so that each SCR catalyst Bottom, on top of each SCR catalyst in the direction opposite to the flue-gas flow (left view) and on top of each SCR catalyst in the same direction as the flue-gas flow, below each SCR catalyst in the opposite direction of the flue-gas flow (right view) A cross-sectional view showing an SCR reactor with a blower installed.
9 is a process conceptual diagram of a SNCR-SCR hybrid nitrogen oxide reduction system having 1) High Dust SCR, 2) Tail End SCR, and 3) Semi-Dust SCR according to one embodiment of the present invention.
10 is a conceptual diagram of a general cyclone.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are only intended to clearly illustrate the technical features of the present invention, but do not limit the protection scope of the present invention.

Example 1: SNCR-SCR Hybrid Nitrogen Oxide Reduction System

(1) Through computational fluid dynamics (CFD), urea water injection nozzles are installed at point(s) where the temperature is uniform while the dust is not concentrated and falls uniformly to increase the efficiency of the selective non-catalytic reduction reaction (SNCR) and a SNCR facility for controlling (CONTROL) the degree of slip generation of unreacted NH ₃ so as to be used as a reducing agent for NOx in a selective catalytic reduction (SCR) at a later stage while exhibiting a NO _X removal efficiency of 40 to 50% through leveling control; and (2) a selective catalytic reduction method (SCR) on a low-temperature catalyst between 200℃ and 300℃, installed at the rear end of the SNCR facility based on exhaust gas and using unreacted NH ₃ slip generated in the SNCR facility as a reducing agent for NOx. Using a SNCR-SCR hybrid system equipped with an SCR facility to perform, the results performed according to the process conceptual diagram of FIG. 1 and the work flow chart of FIG. 5 were compared and analyzed in Table 1 below along with Comparative Examples 1 to 3.

In the work flow chart of FIG. 5 , NH ₃ SLIP by stack NOx is not discharged as N ₂ + H ₂ O and is released into the atmosphere as NH ₃ when the reducing agent is excessively supplied and the amount of the reducing agent is large compared to the NOx treatment efficiency. There is an excessive supply, but when SNCR does not find an appropriate reducing area and sprays _, it is unreacted and released to the atmosphere. NH ₃ is released into the atmosphere according to the supply amount of the reducing agent.

division existing
(Comparative Example 1) SNCR Facility
(Comparative Example 2) SCR facility
(Comparative Example 3) SNCR-SCR HYBRID
(Example 1) NOx Reduction Rate (%) - 30 to 50 60-70 over 80 Residual NOx (ppm) 250 to 300 175 to 210 80-82 80-82 Necessary equipment - SNCR Facility Factor Water Supply Facility SCR facility
Ammonia supply facility SNCR Facility
SCR facility
Urea water supply facility installation cost - I go middle note Application of High Pressure Gas Safety Management Act for high safety facility related costs
Subject to the Chemical Substances Control Act
hazardous chemical target NOx cannot be removed with only SNCR
Separate urea solution supply facility required Excessive catalyst installation cost when using only SCR
Separate ammonia supply facility required Innovative reduction of SCR installation cost due to high SNCR efficiency and reduced SCR load
Satisfaction of NOx regulations by building an integrated system

When NSR=2.4 at 896,000 Nm ³ /h when SNCR facility was applied, NOx Reduction Ratio was 45.8% (192 → 104 ppm).

SNCR facilities usually have a NOx reduction ratio of 20 to 25%, but through computational fluid analysis (CFD), the nozzle location can be selected in the section with the highest NOx removal efficiency of 40 to 50%. Through computational fluid analysis (CFD), it was confirmed that the NOx removal efficiency was 40 to 50% when the urea water injection nozzle was installed at the point(s) where the temperature was uniform while the dust was uniformly descended without being biased.

Example 2 : SNCR-SCR Hybrid Nitrogen Oxide Reduction System for Treating NOx-containing Combustion Gas Generated During Cement Manufacturing Process

NOx-containing combustion gas according to an embodiment of the present invention using urea water as a reducing agent, referring to FIG. Describe the processing method.

At this time, exhaust gas generated during the cement manufacturing process is treated to reduce nitrogen oxides by a selective non-catalytic reduction method, and then nitrogen oxides are reduced by a selective catalytic reduction method.

In the cement manufacturing process, the SNCR reduction efficiency varies greatly depending on the process status, and the urea water input point in the SNCR facility has a relatively low reduction efficiency because gas and raw materials are mixed.

In order to solve this problem, it is preferable that urea water as a reducing agent can be evenly sprayed throughout the reaction section in the SNCR process of a combustion furnace/preheater in which NOx-containing combustion gas is generated by a combustion reaction during the cement manufacturing process. The larger the number of nozzles, the better, but the number of nozzles may be limited in consideration of economic feasibility. also, Particle size can be increased so that the raw material can be pushed against the mixture of gas and raw material, which prevents the reducing agent from reaching the gas layer and hindering the reaction. As a result, the reaction efficiency can be maximized .

In the SNCR reactor, the flow rate (Nm ³ /min) of combustion gas is kept constant, and the NOx concentration contained in the generated combustion gas is measured. As shown in FIGS. 3 and 4, the number of urea at an appropriate concentration so that ammonia can be supplied in an optimum amount according to the change in the concentration of NOx in the generated combustion gas is combusted using a two-fluid spray nozzle for spraying urea. Spray directly into the duct through which the gas flows. When urea water is injected through a two-fluid spray nozzle for urea water spray, the chemical standard stoichiometry ratio of urea can be changed by maintaining a constant spray amount of urea water and changing the urea concentration of urea water. . By maintaining a constant spray amount of urea water, it is possible to maintain a constant hydrodynamic effect on the denitrification reaction by maintaining a constant droplet size, spray distance, and spray angle of the sprayed urea water. Heat resistant and insulated castables can be installed on the outside of the duct. In the longitudinal direction of the duct, a K-Type thermocouple to measure the temperature of the combustion gas and a sampling port to measure the concentration of NO, CO, O ₂ , NH ₃ in the combustion gas can be installed every 50 to 100 cm. The concentrations of NO, CO, and O ₂ can be measured by the NDIR method, and the concentration of NH ₃ can be measured by the neutralization titration method using H ₃ BO ₃ as an absorption liquid.

In the SNCR facility of FIG. 1, the NO removal reaction is almost completed before the residence time of the sprayed urea solution reaches 0.5 seconds, and even if the residence time increases to 0.5 seconds or more, the NO reduction efficiency can be maintained almost constant.

For example, NO reduction efficiency increases as the injection temperature of atomized urea water, which is a reducing agent, increases from 840 ^° C, reaching a maximum value around 960 ~ 980 ° C, and decreases when the reducing agent injection temperature is further increased. Temperature of SNCR reaction dependence appears. This temperature dependence of the SNCR reaction suggests that at the optimal injection temperature of the sprayed urea water droplets, the reduction reaction between ammonia and NO, a reducing agent generated by thermal decomposition of urea water, occurs at a rapid rate and NO is reduced to N ₂ to reach the maximum NO reduction efficiency. can At this time, when the temperature of the sprayed urea water droplets is cooled so that the temperature does not rise, the NO removal reaction rate of the reducing agent ammonia generated by the thermal decomposition of the urea water is slowed down so that ammonia is discharged in an unreacted state, and the selective catalytic reduction reaction (SCR) at the rear can generate unreacted NH ₃ slip to be used as a reducing agent for NOx in

In addition, the SNCR nozzle was installed in the preheater where the temperature was appropriate (450 ° C to 550 ° C) to control and supply the amount of ammonia reducing agent required in the SCR.

In the SNCR reactor in which urea water is used as a reducing agent, major process variables such as the injection temperature of the reducing agent, the normalized stoichiometric ratio (NSR) of the reducing agent, and the combustion gas residence time affect the NO reduction efficiency and the degree of slip generation of unreacted NH ₃ crazy

In the SNCR facility, the temperature inside the combustion furnace and/or preheater is 850 ~ 1030 ℃, and through computational fluid analysis (CFD), the urea water injection nozzle is installed, and when urea water is sprayed with a droplet size of 300㎛ or more through a two-fluid spray nozzle for urea water spray, the nozzle tip is not clogged by dust and urea water is thermally decomposed to generate ammonia, and ammonia slip occurs and Together, this resulted in a denitrification efficiency of ~45%.

Subsequently, through the SCR facility installed at the rear end of the SNCR facility and using the unreacted NH ₃ slip generated in the SNCR facility as a reducing agent for NOx and performing a selective catalytic reduction reaction (SCR) on the catalyst, NOx emissions are regulated in the cement manufacturing process was able to satisfy

1: SCR reactor
2: Catalyst
3: soot blower

Claims (18)

(1) Through computational fluid dynamics (CFD), NHx-based reducing agent injection nozzles are installed at point(s) where the temperature is uniform while the dust is not concentrated and falls uniformly, and the selective non-catalytic reduction reaction (SNCR) efficiency Controlling the degree of slip generation of unreacted NH ₃ so that it is used as a reducing agent for NOx in the selective catalytic reduction (SCR) at the later stage while exhibiting a _NOx reduction rate of 40 to 50% through augmentation and leveling control ( CONTROL) SNCR facility; and
(2) An SCR facility installed at the rear of the SNCR facility based on exhaust gas and performing selective catalytic reduction (SCR) on the catalyst while using unreacted NH ₃ slip generated in the SNCR facility as a reducing agent for NOx.
SNCR-SCR hybrid nitrogen oxide reduction system comprising a. The method of claim 1, wherein _NOx removal efficiency according to the integrated system construction is 80% or more, residual NOx is 80 ~ 82ppm, and / or SCR installation cost is reduced due to high SNCR efficiency and SCR load reduction. SNCR-SCR Hybrid Nitrogen Oxide Reduction System. The SNCR-SCR hybrid nitrogen oxide reduction system according to claim 1, wherein the SCR facility performs selective catalytic reduction (SCR) on a low temperature catalyst between 200 ° C and 300 ° C. The method of claim 1, wherein the SCR facility uses the same reducing agent as the SNCR facility to unify the dual reducing agent supply facility, and considering the characteristics of the NHx-based reducing agent that requires vaporization energy NHx in the low temperature section where ammonia slip is formed in the SNCR facility A SNCR-SCR hybrid nitrogen oxide reduction system characterized by controlling and supplying the amount of reducing agent required by the SCR facility by installing a reducing agent injection nozzle on the base. The SNCR-SCR hybrid nitrogen oxide reduction system according to claim 1, which is designed to use an NHx-based reducing agent as a NOx reducing agent in the SNCR facility and use ammonia slip generated in the SNCR facility as a NOx reducing agent in the SCR facility,
The SNCR facility is a SNCR-SCR hybrid nitrogen oxide reduction system characterized by increasing the amount of NHx-based reducing agent injected by greatly adjusting the droplet particle size through a two-fluid spray nozzle to generate unreacted ammonia. The SNCR-SCR hybrid nitrogen oxide reduction system according to claim 1, which is designed to use an NHx-based reducing agent as a NOx reducing agent in the SNCR facility and use ammonia slip generated in the SNCR facility as a NOx reducing agent in the SCR facility,
The NHx-based reducing agent injection nozzle is concentrically arranged outside the NHx-based reducing agent injection pipe and the compressed air injection pipe, and extends to the nozzle tip, but a cooling fluid injection pipe for nozzle protection in which the cooling fluid flowing in the internal space is not injected through the nozzle cap. A two-fluid spray nozzle further provided with,
When cooling fluid is sprayed from the cooling fluid injection tube for nozzle protection near the nozzle tip, NHx is injected through the nozzle cap and/or the shield layer that blocks the flow of dust near the nozzle tip due to the expansion of the sprayed cooling fluid. A SNCR-SCR hybrid nitrogen oxide reduction system characterized by forming an insulating shield layer that slows down the heating of the base reducing agent droplets. The SNCR-SCR hybrid nitrogen oxide reduction system according to claim 1, which is designed to use an NHx-based reducing agent as a NOx reducing agent in the SNCR facility and use ammonia slip generated in the SNCR facility as a NOx reducing agent in the SCR facility,
A SNCR-SCR hybrid nitrogen oxide reduction system characterized by a standard stoichiometric ratio (NSR, [NH ₃ ] _{reducing agent} / [NOx]) of 1.5 or more so that ammonia slip occurs in the SNCR facility. The method of claim 1, wherein the SCR facility performs selective catalytic reduction (SCR) on ammonia gas and exhaust gas containing dust and NOx,
For the exhaust gas flow continuously flowing through the fixed catalyst layer, compressed air is intermittently injected through a soot blower installed at the front and / or the rear of the fixed catalyst layer to provide forward and / or reverse disturbance,
(1) while suppressing the attachment or deposition of dust in the exhaust gas to the fixed catalyst layer,
(2) Oxygen gas, which is a reactant, is supplied as far as possible by intermittently injected compressed air, and reacts in the direction of removing or weakening the longitudinal reaction gas gradient in each fixed catalyst layer through intermittent forward and/or reverse disturbance. A SNCR-SCR hybrid NOx reduction system designed to increase the overall NOx removal efficiency of the SCR reactor by mixing gases. The method of claim 8, wherein the SCR facility has two or more fixed catalyst layers vertically spaced apart from the exhaust gas flow,
A SNCR-SCR hybrid nitrogen oxide reduction system characterized by a vertical arrangement of multiple soot blowers spraying compressed air at regular intervals from the catalyst layer. The method of claim 8, wherein the catalyst layer is stacked vertically spaced apart in multiple stages, and the exhaust gas flow flows from the vertical bottom to the top of the catalyst layer,
The soot blower blows compressed air (1) in the same direction as the exhaust gas flow at the bottom of each catalyst layer or (2) in the same direction as the exhaust gas flow at the bottom of each catalyst layer and in the opposite direction to the exhaust gas flow at the top of each catalyst layer;
The soot blower blows compressed air in (1) the same direction as the exhaust gas flow at the top of each catalyst layer or (2) the same direction as the exhaust gas flow at the top of each catalyst layer and the opposite direction to the exhaust gas flow at the bottom of each catalyst layer. SCR Hybrid Nitrogen Oxide Reduction System. The method of claim 8, wherein the soot blower injects compressed air for 10 seconds to 30 seconds at intervals of 1 minute to 3 minutes for each catalyst layer spaced apart in multiple stages, and blows compressed air from the first catalyst layer to the last layer in the direction of exhaust gas flow. A SNCR-SCR hybrid nitrogen oxide reduction system characterized by sequential injection by program control through automatic valves installed in each line according to time and/or differential pressure changes. According to claim 1, when exhaust gas with a high air volume of 450,000 Nm ³ /hr or more containing 120 g / Nm ³ or more of dust generated in the cement manufacturing process passes through the SCR facility, a soot blower and / or a sonic horn ( SNCR-SCR Hybrid Nitrogen Oxide Reduction System characterized by passing dust-containing exhaust gas through a Sonic Hone, collecting unpassed dust and discharging it through a separate outlet. The SNCR-SCR hybrid nitrogen oxide reduction system according to claim 1, further characterized in that the ammonia injection nozzle is located in front of the first catalyst layer in the exhaust gas flow direction. A method of treating NOx-containing combustion gas using the SNCR-SCR hybrid nitrogen oxide reduction system according to any one of claims 1 to 13,
In the SNCR facility, ammonia is generated by performing urea decomposition reaction of urea water injected from a two-fluid spray nozzle, and NOx reduction reaction of NOx-containing combustion gas is performed by ammonia generated by urea decomposition reaction of urea water. A first step of controlling (CONTROL) the degree of reactive NH ₃ slip generation; or
A first step of controlling (CONTROL) the degree of unreacted NH ₃ slip generation while performing a NOx reduction reaction of NOx-containing combustion gas by an NHx-based reducing agent injected from a two-fluid spray nozzle in a SNCR facility; and
The second step of performing selective catalytic reduction (SCR) in the SCR facility while using the unreacted NH ₃ slip generated in the SNCR facility as a reducing agent for NOx
A method for treating NOx-containing combustion gas, characterized in that it comprises a. 15. The method of claim 14, wherein the two-fluid spray nozzle for spraying the NHx-based reducing agent in the SNCR facility injects the size of the NHx-based reducing agent spray droplet when the NHx-based reducing agent is sprayed with a size of 100 μm or more. A method for treating NOx-containing combustion gas. The method for treating NOx-containing combustion gases according to claim 14, characterized in that NOx-containing combustion gases generated from a combustion furnace and/or a pre-heater during the cement manufacturing process are treated. A cement manufacturing method characterized by treating NOx-containing combustion gas generated from a combustion furnace and/or a preheater during the cement manufacturing process with the SNCR-SCR hybrid nitrogen oxide reduction system according to any one of claims 1 to 13 . The cement manufacturing method according to claim 17, wherein the cement manufacturing process uses industrial by-products as cement raw materials or fuel.

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