Process system for reducing nitrogen oxide emission of sleeve lime kiln

Abstract

The invention provides a process system for reducing nitrogen oxide emission of a sleeve lime kiln. The process system comprises a reducing agent production system, a process water treatment system and an SCR (Selective Catalytic Reduction) denitration system, urea is used for producing a reducing agent for treating nitric oxide, urea is used as a raw material for preparing reducing agent ammonia gas, the characteristics of energy conservation, emission reduction and good economic benefits are achieved, and urea is solid, is convenient to transport and store and is not limited; compared with the process of preparing ammonia by using ammonia water or liquid ammonia as a reducing agent, the process of preparing ammonia by hydrolyzing urea has higher safety; the urea hydrolysis catalyst is environment-friendly, so that the emission of harmful substances is reduced, and the environment is protected; by adding a process water treatment link, generated wastewater can be treated and utilized, and pollution to the environment is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of nitrogen oxide emission treatment of a sleeve lime kiln, and in particular to a process system for reducing nitrogen oxide emission from a sleeve lime kiln. Background Art

[0002] Lime kilns produce a lot of flue gas and wastewater during the production process. Flue gas often contains harmful substances such as nitrogen oxides and smoke. If these flue gases are directly discharged into the atmosphere, they will have a serious impact on human health and the environment. Therefore, the state has very strict requirements on the flue gas emissions of lime kilns. At the same time, the wastewater generated must also be properly treated to reduce pollution to the environment.

[0003] According to national regulations, lime kilns must be equipped with corresponding fume and waste liquid treatment facilities to ensure that harmful substances are effectively treated. At the same time, for newly built lime kilns, clean production technology and equipment must be used to reduce the generation of harmful fume from the source. For existing lime kilns, the state requires that technical transformation be completed within the specified time to meet environmental protection requirements.

[0004] It is very important to treat nitrogen oxides in flue gas, and reducing nitrogen oxide emissions can reduce environmental pollution. At the same time, the reasonable treatment of wastewater is also very important to reduce environmental pollution. Summary of the invention

[0005] In view of this, the present invention proposes a process system for reducing nitrogen oxide emissions from a sleeve lime kiln, comprising: A reducing agent production system, comprising a dissolving tank, a storage tank and a hydrolyzer, wherein the dissolving tank is connected to the storage tank, and the storage tank is connected to the hydrolyzer, wherein urea is dissolved in the dissolving tank and is sent to the storage tank for standby after being completely dissolved, and a preset amount of urea solution is sent to the hydrolyzer for hydrolysis reaction to generate ammonia; A process water treatment system, comprising a drain tank, a pump body and a steam generator, wherein the drain tank is connected to the pump body and the steam generator respectively, and the condensed water and impurity solution generated in the lime kiln production process can be transported to the drain tank for treatment, and the treated waste water and waste liquid are discharged by the pump body, and part of the process water is treated by the steam generator and then transported to the hydrolyzer in the form of steam for secondary use; The SCR denitration system comprises a heating furnace, an SCR reactor, a hot air collection system and a mixer. The mixer is connected to the hydrolyzer, the hot air collection system and the SCR reactor respectively. The ammonia generated in the hydrolyzer and the hot air generated by the hot air collection system can be mixed in the mixer and then transported from the mixer to the SCR reactor. The flue gas to be treated can enter the SCR reactor after being heated in the heating furnace. In the SCR reactor, the hot air, the ammonia mixture and the heated flue gas are mixed, and the nitrogen oxides in the flue gas react chemically with the ammonia.

[0006] Furthermore, the hot air collection system includes a heater and a dilution fan. The air is first heated to a preset temperature by the heater, and then diluted by the dilution fan and sent to the mixer.

[0007] Furthermore, the SCR denitration system is provided with two groups, each receiving ammonia produced by the reductant production system as the reductant, and two flues are provided for the two groups of the SCR denitration system.

[0008] Furthermore, the temperature of the flue gas rises to 170-180° C. when entering the SCR reactor.

[0009] Furthermore, the hydrolyzer is an adiabatic hydrolysis reactor.

[0010] Furthermore, the reducing agent production system also includes a metering device and a distribution device. The urea solution is metered by the metering device and then distributed by the distribution device before entering the hydrolyzer to undergo a hydrolysis reaction.

[0011] Furthermore, an ammonia injection grid is provided between the mixer and the SCR reactor, which can inject the mixed gas of ammonia and air in the mixer into the SCR reactor.

[0012] Furthermore, the flue gas is subjected to dust removal treatment by a dust removal high-temperature filter bag before entering the SCR reactor. After the dust removal treatment, whether to perform heating in the heating furnace is determined according to the temperature of the flue gas.

[0013] Furthermore, during the reaction of nitrogen oxides and ammonia in the SCR reactor, a catalyst is added to control the reaction result and reaction progress.

[0014] The process system for reducing nitrogen oxide emissions from a sleeve lime kiln provided by the present invention has the following advantages: using urea as a raw material to prepare reducing agent ammonia has the characteristics of energy saving, emission reduction and good economic benefits. Urea is solid and is easy to transport and store without restrictions. The process of preparing ammonia by urea hydrolysis has higher safety than using ammonia water or liquid ammonia as a reducing agent. The urea hydrolysis catalyst is environmentally friendly and helps to reduce the emission of harmful substances and protect the environment. By adding a process water treatment link, the generated wastewater can be treated and utilized to reduce pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings: Figure 1 A schematic diagram of the structure of a process system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0016] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to be able to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0017] See also Figure 1As shown, it is a process system for reducing nitrogen oxide emissions from a sleeve lime kiln provided by an embodiment of the present invention, including a reducing agent production system, a process water treatment system and an SCR denitrification system; the reducing agent production system includes a dissolving tank, a storage tank and a hydrolyzer, the dissolving tank is connected to the storage tank, the storage tank is connected to the hydrolyzer, urea is dissolved in the dissolving tank, and after complete dissolution, it is sent to the storage tank for standby, a preset amount of urea solution is transported to the hydrolyzer and then hydrolyzed to generate ammonia. In this embodiment, the hydrolyzer is an adiabatic hydrolysis reactor; the process water treatment system includes a drain tank, a pump body and a steam generator, the drain tank is connected to the pump body and the steam generator respectively, and the condensed water and impurity solution generated during the lime kiln production process can be transported to the drain tank The treated wastewater and waste liquid are discharged by the pump body after treatment. Part of the process water is treated by the steam generator and then sent to the hydrolyzer for secondary utilization in the form of steam; the SCR denitrification system includes a heating furnace, an SCR reactor, a hot air collection system and a mixer. The mixer is connected with the hydrolyzer, the hot air collection system and the SCR reactor respectively. The ammonia generated in the hydrolyzer and the hot air generated by the hot air collection system can be mixed in the mixer and then transported from the mixer to the SCR reactor. The flue gas to be treated can be heated in the heating furnace and then enter the SCR reactor. In the SCR reactor, the hot air, the ammonia mixture and the heated flue gas are mixed, and the nitrogen oxides in the flue gas react chemically with the ammonia.

[0018] Continue to refer to Figure 1 As shown, the hot air collection system includes a heater and a dilution fan. The air is first heated to a preset temperature by the heater, and then diluted by the dilution fan and sent to the mixer.

[0019] In this embodiment, the SCR denitration system is provided with two groups, referring to Figure 1 As shown, ammonia produced by the reducing agent production system is respectively accepted as the reducing agent, and two flues are equipped for the two groups of SCR denitrification systems.

[0020] In this embodiment, the temperature of the flue gas rises to 170-180° C. when entering the SCR reactor.

[0021] In this embodiment, the reducing agent production system further includes a metering device and a distribution device. The urea solution is metered by the metering device and then distributed by the distribution device to enter the hydrolyzer for hydrolysis reaction.

[0022] In this embodiment, an ammonia injection grid is further provided between the mixer and the SCR reactor, which can inject the mixed gas of ammonia and air in the mixer into the SCR reactor.

[0023] In this embodiment, the flue gas is further subjected to dust removal treatment by a dust removal high-temperature filter bag before entering the SCR reactor. After the dust removal treatment, whether to perform heating in the heating furnace is determined according to the temperature of the flue gas.

[0024] In this embodiment, during the reaction of nitrogen oxides and ammonia in the SCR reactor, a catalyst is added to control the reaction result and reaction progress.

[0025] The present invention provides a specific SCR denitrification construction scheme for a process system for reducing nitrogen oxide emissions from a sleeve lime kiln: (1) The denitrification project uses urea as a reducing agent. The urea solution is pumped from the urea dissolution tank area to the urea hydrolysis reactor. After hydrolysis, the ammonia gas is connected to the denitrification device. The steam source is provided by the construction unit and transported to the denitrification device through the steam pipeline network. The steam is connected by connecting the denitrification steam pipeline network with the external steam pipeline network; (2) The original flue gas is also provided by the construction unit. The dust removal high-temperature filter bag is modified. The flue gas temperature rises to 170-180℃ before entering the SCR reactor. If the flue gas temperature cannot reach the expected temperature, it needs to be raised again through a hot air furnace. An ammonia spray grid is installed in the reactor inlet flue. (3) Urea solution enters the adiabatic hydrolysis reactor through the supply device, metering and distribution device, catalyst decomposition tank, etc. The air provided by the dilution fan enters the heat exchange device for heating and then enters the ammonia collection area at the outlet of the hydrolysis chamber. Urea droplets decompose in the adiabatic urea decomposition reactor to generate the reducing agent NH3 required by the SCR denitrification system. The decomposition products enter the flue gas denitrification system through the ammonia injection system (AIG); (4) Urea is sprayed into the urea hydrolysis reactor through a urea spray gun from a urea metering pump. At the same time, the dilution air is heated to 170-180°C through an air preheater. The hot air is diluted with ammonia in the urea hydrolysis reactor; ammonia and air are evenly mixed in the urea hydrolysis reactor. The mixed ammonia / air is sprayed into the inlet flue of the SCR reactor through an ammonia spray grid; the heat source for urea hydrolysis is the steam generated by a steam generator for heating; (5) The ammonia / air mixture enters the SCR reactor. The NOx in the flue gas undergoes a reduction reaction with ammonia in the SCR reactor under the action of a catalyst and is converted into nitrogen and water, thereby achieving the purpose of removing NOx.

[0026] A process system for reducing nitrogen oxide emissions from a sleeve lime kiln disclosed in an embodiment of the present invention has the following beneficial technical effects: using urea as a raw material to prepare ammonia gas as a reducing agent has the characteristics of energy saving, emission reduction and good economic benefits, and urea is solid, which is convenient to transport and store without restrictions; the process of preparing ammonia by urea hydrolysis has higher safety than using ammonia water or liquid ammonia as a reducing agent; the urea hydrolysis catalyst is environmentally friendly, helps to reduce the emission of harmful substances and protect the environment; and by adding a process water treatment link, the generated wastewater can be treated and utilized to reduce pollution to the environment.

[0027] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0028] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A process system for reducing nitrogen oxide emissions from a sleeve lime kiln, characterized in that: include: A reducing agent production system, comprising a dissolving tank, a storage tank and a hydrolyzer, wherein the dissolving tank is connected to the storage tank, and the storage tank is connected to the hydrolyzer, wherein urea is dissolved in the dissolving tank and is sent to the storage tank for standby after being completely dissolved, and a preset amount of urea solution is sent to the hydrolyzer for hydrolysis reaction to generate ammonia; A process water treatment system, comprising a drain tank, a pump body and a steam generator, wherein the drain tank is connected to the pump body and the steam generator respectively, and the condensed water and impurity solution generated in the lime kiln production process can be transported to the drain tank for treatment, and the treated waste water and waste liquid are discharged by the pump body, and part of the process water is treated by the steam generator and then transported to the hydrolyzer in the form of steam for secondary use; The SCR denitration system comprises a heating furnace, an SCR reactor, a hot air collection system and a mixer. The mixer is connected to the hydrolyzer, the hot air collection system and the SCR reactor respectively. The ammonia generated in the hydrolyzer and the hot air generated by the hot air collection system can be mixed in the mixer and then transported from the mixer to the SCR reactor. The flue gas to be treated can enter the SCR reactor after being heated in the heating furnace. In the SCR reactor, the hot air, the ammonia mixture and the heated flue gas are mixed, and the nitrogen oxides in the flue gas react chemically with the ammonia.

2. The process system for reducing nitrogen oxide emissions from a sleeve lime kiln according to claim 1 is characterized in that: The hot air collection system includes a heater and a dilution fan. The air is first heated to a preset temperature by the heater, and then diluted by the dilution fan and sent to the mixer.

3. The process system for reducing nitrogen oxide emissions from a sleeve lime kiln according to claim 1, characterized in that: The SCR denitration system is provided with two groups, each receiving ammonia produced by the reductant production system as a reductant, and two flues are provided for the two groups of the SCR denitration system.

4. The process system for reducing nitrogen oxide emissions from a sleeve lime kiln according to claim 1, characterized in that: The temperature of the flue gas rises to 170-180°C when entering the SCR reactor.

5. The process system for reducing nitrogen oxide emissions from a sleeve lime kiln according to claim 1, characterized in that: The hydrolyzer is an adiabatic hydrolysis reactor.

6. The process system for reducing nitrogen oxide emissions from a sleeve lime kiln according to claim 1, characterized in that: The reducing agent production system further comprises a metering device and a distributing device. The urea solution is metered by the metering device and then distributed by the distributing device before entering the hydrolyzer to undergo a hydrolysis reaction.

7. The process system for reducing nitrogen oxide emissions from a sleeve lime kiln according to claim 1, characterized in that: An ammonia injection grid is also provided between the mixer and the SCR reactor, which can inject the mixed gas of ammonia and air in the mixer into the SCR reactor.

8. The process system for reducing nitrogen oxide emissions from a sleeve lime kiln according to claim 1, characterized in that: The flue gas is also subjected to dust removal treatment by a dust removal high temperature filter bag before entering the SCR reactor. After the dust removal treatment, whether to perform heating in the heating furnace is determined according to the temperature of the flue gas.

9. The process system for reducing nitrogen oxide emissions from a sleeve lime kiln according to any one of claims 1 to 8, characterized in that: During the reaction of nitrogen oxides and ammonia in the SCR reactor, a catalyst is added to control the reaction result and reaction progress.

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