A system and method for treating dust-laden furnace gas from a light ash calciner

Abstract

The invention discloses a light ash calcining furnace dust-containing furnace gas treatment system and treatment method, relates to the chemical industry furnace gas treatment technical field, and adopts a hot lye tower to replace a high energy consumption electric dust collector, which not only effectively improves the alkali dust removal efficiency, and can significantly reduce the production cost. The application of the hot lye tower also changes the operation logic and process of the subsequent process, and the surplus hot lye in the hot lye tower is sent to the heavy alkali process as filter washing water, compared with the washing liquid in the prior art, the ammonia content in the hot lye is low, which can effectively solve the problem of ammonia gas escape pollution. At the same time, the washing liquid originally used as filter washing water is transported to the ammonia evaporation system for ammonia recovery, the alkali dust content in the washing liquid is low, which can effectively avoid the problem of pipeline blockage. The treatment system and treatment method are logical, the overall dust removal efficiency can be as high as 99.75%, the ammonia recovery efficiency is high, the pollution is low, the environment is friendly, and the treatment system and treatment method have better practical value.

Description

Technical Field

[0001] This invention relates to the field of chemical furnace gas treatment technology, and more specifically, to a treatment system and method for dust-laden furnace gas from a light ash calcining furnace. Background Technology

[0002] Soda ash, also known as sodium carbonate, is an important basic chemical raw material. The light ash calcination process is the final step in the production of light soda ash. Wet heavy soda ash from the filtration process is heated and decomposed in a calcining furnace to produce qualified light soda ash. Heavy soda ash (NaHCO3) decomposes in the calcining furnace, generating a large amount of furnace gas at a temperature of 100-130℃. Its main components (mol%) are: NH3 (2.6%), CO2 (23.4%), H2O (72.1%), AIR (2%), and Na2CO3 dust (200-300 g / Nm³). 3 ).

[0003] Existing furnace gas treatment equipment such as Figure 1 As shown, high-temperature furnace gas is typically exported through a furnace gas system. After passing through a cyclone separator 110 and an electrostatic precipitator 120 to remove entrained alkaline dust, the furnace gas is then output to a furnace gas condenser 130 for condensation. During condensation, water vapor in the furnace gas condenses, along with some ammonia, carbon dioxide, and residual alkaline dust, forming a condensate. This condensate is directly sent to an ammonia stripping system to recover ammonia. The condensed furnace gas is then further sent to a furnace gas scrubbing tower 140 for further processing. In the furnace gas scrubbing tower 140, the scrubbing liquid washes away the remaining ammonia in the furnace gas. The scrubbing liquid containing dissolved ammonia is then sent to the heavy alkali process for use as filter wash water.

[0004] The following problems exist in this process:

[0005] 1. Electrostatic precipitators consume a lot of energy, have low dust removal efficiency, and bring a large amount of alkaline dust into the subsequent system, causing problems such as blockage of the furnace gas condenser and low heat exchange efficiency.

[0006] 2. The condensate output from the furnace gas condenser contains a large amount of residual alkaline dust (Na2CO3), which blocks the equipment and pipelines of the ammonia stripping system and affects the stable operation of the ammonia stripping system;

[0007] 3. The washing liquid output from the furnace gas scrubbing tower contains a large amount of ammonia. When it is sent to the heavy alkali process as filter washing water, the ammonia escape leads to a harsh operating environment and causes environmental pollution. Summary of the Invention

[0008] The purpose of this invention is to provide a treatment system and method for dust-laden furnace gas from a light ash calcining furnace, which can effectively remove alkaline dust from the furnace gas and overcome the problems of equipment blockage and environmental pollution in the prior art.

[0009] The embodiments of the present invention are implemented as follows:

[0010] A system for treating dust-laden furnace gas from a light ash calcining furnace, comprising:

[0011] Cyclone separator, the inlet end of which is connected to the furnace gas outlet of the calcining furnace;

[0012] The hot alkali solution tower has its lower air inlet connected to the air outlet of the cyclone separator. The bottom of the hot alkali solution tower is filled with hot alkali solution, which is pumped to the upper middle part of the tower by a hot alkali solution pump to circulate and scrub the furnace gas. Excess hot alkali solution is pumped to the heavy alkali process by a hot alkali solution pump.

[0013] The furnace gas condenser has its inlet end connected to the outlet end at the top of the hot alkali tower.

[0014] The furnace gas scrubbing tower has its lower inlet connected to the lower outlet of the furnace gas condenser. The bottom of the furnace gas scrubbing tower is filled with scrubbing liquid, which is pumped to the middle of the furnace gas scrubbing tower by a scrubbing liquid pump for circulating and scrubbing the furnace gas. Excess scrubbing liquid is pumped to the ammonia stripping system by a scrubbing liquid pump.

[0015] Furthermore, in other preferred embodiments of the present invention, the drain end at the bottom of the furnace gas condenser is connected to the lower part of the hot alkali tower via a condensate pump.

[0016] Furthermore, in other preferred embodiments of the present invention, a furnace gas separator is also included, wherein the inlet end of the furnace gas separator is connected to the outlet end at the top of the furnace gas scrubbing tower, and the drain end at the bottom of the furnace gas separator is connected to the top of the furnace gas scrubbing tower.

[0017] Furthermore, in other preferred embodiments of the present invention, the cyclone separator includes a primary cyclone separator and a secondary cyclone separator arranged in series; the inlet end of the primary cyclone separator is connected to the furnace gas outlet of the calcining furnace, and the outlet end of the secondary cyclone separator is connected to the inlet end of the hot alkali tower.

[0018] Furthermore, in other preferred embodiments of the present invention, the ammonia stripping system includes an ammonia stripping tower and an ammonia recovery tower. The liquid inlet at the top of the ammonia stripping tower is connected to the washing liquid pump, and a low-pressure steam inlet pipe is provided at the bottom of the ammonia stripping tower to introduce low-pressure steam. An ammonia separator is provided at the top of the ammonia stripping tower and is connected to the ammonia stripping tower. The gas outlet at the top of the ammonia separator is connected to the gas inlet at the bottom of the ammonia recovery tower, and the gas outlet at the top of the ammonia recovery tower is connected to the gas inlet at the furnace gas scrubbing tower.

[0019] Furthermore, in other preferred embodiments of the present invention, the drain end at the bottom of the ammonia stripping tower is connected to the hot side inlet of the feed preheater via a waste desalination pump, and the hot side outlet of the feed preheater is connected to the top of the furnace gas scrubbing tower; the cold side inlet of the feed preheater is connected to the scrubbing liquid pump, and the cold side outlet is connected to the liquid inlet at the top of the ammonia stripping tower.

[0020] A method for treating dust-laden furnace gas from a light ash calcining furnace, comprising the above-mentioned treatment system, including:

[0021] The furnace gas containing alkali dust generated from calcining heavy alkali is transported to a cyclone separator for preliminary separation. The separated furnace gas is then transported to the lower part of the hot alkali liquid tower, and the alkali dust is recovered through the bottom of the cyclone separator.

[0022] The furnace gas enters from the bottom of the hot alkali solution tower and comes into countercurrent contact with the hot alkali solution entering from the top of the hot alkali solution tower, allowing the alkali dust carried in the furnace gas to be further transferred into the hot alkali solution; the excess hot alkali solution is transported to the heavy alkali process and used as filter washing water; the furnace gas output from the top of the hot alkali solution tower is transported to the furnace gas condenser.

[0023] The furnace gas condenser condenses most of the water vapor in the furnace gas and sends it back to the bottom of the hot alkali tower as a supplement to the washing water of the hot alkali tower; the condensed furnace gas is then sent to the bottom of the furnace gas scrubbing tower.

[0024] The furnace gas enters from the bottom of the furnace gas scrubbing tower and comes into countercurrent contact with the scrubbing liquid entering from the middle of the furnace gas scrubbing tower to scrub the ammonia in the furnace gas. After scrubbing, the furnace gas is sent to the furnace gas compression process by an induced draft fan. The excess scrubbing liquid is sent to the ammonia stripping process to recover the ammonia.

[0025] Furthermore, in other preferred embodiments of the present invention, the temperature of the excess hot alkali solution output from the hot alkali solution tower is controlled at 85~90°C, and the ammonia content is <2000mg / L. After cooling it to 30~40°C, it is sent to the heavy alkali process for use as filter washing water; the temperature of the furnace gas output from the hot alkali solution tower is controlled at 85~90°C.

[0026] Furthermore, in other preferred embodiments of the present invention, the furnace gas condenser cools the input furnace gas to 35~40°C.

[0027] Furthermore, in other preferred embodiments of the present invention, the temperature of the furnace gas output from the furnace gas scrubbing tower is controlled at 35~40°C and the ammonia content is <0.6%; the temperature of the excess scrubbing liquid output from the furnace gas scrubbing tower is controlled at 35~40°C and the ammonia concentration is 1.5%~2%. After being heated to 80~85°C, it is sent to the ammonia stripping process to recover the ammonia gas therein.

[0028] The beneficial effects of the embodiments of the present invention are:

[0029] This invention provides a system and method for treating dust-laden furnace gas from a light ash calcining furnace. It replaces the energy-intensive electrostatic precipitator with a hot alkali tower, effectively improving dust removal efficiency and significantly reducing production costs. The application of the hot alkali tower further alters the operational logic and flow of subsequent processes. Excess hot alkali solution from the tower is sent to the heavy alkali process for use as filtration washing water. Compared to the washing liquid used in existing technologies, the hot alkali solution has a lower ammonia content, effectively solving the problem of ammonia escape and environmental pollution. Simultaneously, the washing liquid, originally used as filtration washing water, is sent to the ammonia stripping system for ammonia recovery. The low alkali dust content in the washing liquid effectively avoids pipeline blockage. This treatment system and method are logically sound, achieving an overall dust removal efficiency of up to 99.75%, high ammonia recovery efficiency, low pollution, and environmental friendliness, demonstrating significant practical value. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of a dust-laden gas treatment system for a light ash calcining furnace in the prior art;

[0032] Figure 2 This is a schematic diagram of the dust-laden gas treatment system for a light ash calcining furnace provided in Embodiment 1 of the present invention;

[0033] Figure 3 This is a schematic diagram of the dust-laden gas treatment system for a light ash calcining furnace provided in Embodiment 2 of the present invention.

[0034] Icons: 110-Cyclone separator; 111-First-stage cyclone separator; 112-Second-stage cyclone separator; 120-Electrostatic precipitator; 130-Furnace gas condenser; 131-Condensate pump; 140-Furnace gas scrubbing tower; 141-Scrubbing liquid pump; 210-Hot alkali solution tower; 211-Hot alkali solution pump; 212-Hot alkali solution cooler; 220-Furnace gas separator; 221-Induced draft fan; 230-Ammonia stripping tower; 231-Ammonia fractionator; 232-Waste desalination pump; 240-Ammonia recovery tower; 250-Feed preheater; 251-Waste desalination cooler. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0038] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0040] Example 1

[0041] This embodiment provides a system for treating dust-laden furnace gas from a light ash calcining furnace, referring to... Figure 2 As shown, it includes a cyclone separator 110, a hot alkali tower 210, a furnace gas condenser 130, and a furnace gas scrubbing tower 140.

[0042] The cyclone separator 110 has its inlet connected to the furnace gas outlet of the calcining furnace. The furnace gas temperature is 100~130℃, and its main components (mol%) are: NH3 (2.6%), CO2 (23.4%), H2O (72.1%), AIR (2%), and Na2CO3 dust (200~300g / Nm³). 3 In the cyclone separator 110, 90% to 95% of the alkaline dust can be separated, and this part of the alkaline dust can be recycled and reused.

[0043] Furthermore, such as Figure 2 As shown, to improve separation efficiency, the cyclone separator 110 includes a primary cyclone separator 111 and a secondary cyclone separator 112 connected in series. The inlet of the primary cyclone separator 111 is connected to the furnace gas outlet of the calcining furnace, and the outlet of the secondary cyclone separator 112 is connected to the inlet of the hot alkali tower 210. After two-stage cyclone separation, it can be ensured that 95% of the alkali dust in the furnace gas is removed.

[0044] The air inlet at the bottom of the hot alkali solution tower 210 is connected to the air outlet of the cyclone separator 110; the furnace gas separated by the cyclone further removes alkali dust in the hot alkali solution tower 210. The bottom of the hot alkali solution tower 210 is filled with hot alkali solution, which is pumped by the hot alkali solution pump 211 to the upper middle part of the tower for circulating and rinsing the furnace gas. Optionally, the hot alkali solution pump 211 pressurizes the hot alkali solution to 0.5 MPa and divides it into four streams, which enter the middle and upper parts of the hot alkali solution tower 210 for spraying, thereby increasing the contact area between the hot alkali solution and the furnace gas. During the rinsing process, alkali dust is further transferred to the hot alkali solution. After sufficient alkali dust is absorbed, the excess hot alkali solution can be controlled by a valve to be pumped by the hot alkali solution pump 211 to the hot alkali solution cooler 212 for cooling, and then sent to the heavy alkali process for use as filter wash water. After cyclone separation and hot alkaline scrubbing, more than 99% of the alkaline dust in the furnace gas can be removed, thus effectively avoiding the impact of alkaline dust on subsequent processes.

[0045] like Figure 2 As shown, the inlet end of the furnace gas condenser 130 is connected to the outlet end of the hot alkali tower 210. The furnace gas, after being scrubbed with hot alkali, enters the furnace gas condenser 130 and indirectly exchanges heat with the circulating cooling water. The furnace gas is condensed to 40°C, condensing most of the water vapor while dissolving some ammonia, carbon dioxide, and a small amount of residual alkali dust to form condensate. Furthermore, the drain end at the bottom of the furnace gas condenser 130 is connected to the lower part of the hot alkali tower 210 via a condensate pump 131. The condensate is drawn from the bottom of the furnace gas condenser 130, pressurized to 0.5 MPa by the condensate pump 131, and then sent to the lower part of the hot alkali tower 210 as a supplement to the scrubbing water in the hot alkali tower 210.

[0046] The inlet of the furnace gas scrubbing tower 140 is connected to the outlet of the furnace gas condenser 130. The condensed furnace gas undergoes further scrubbing in the furnace gas scrubbing tower 140 to remove ammonia and trace amounts of alkaline dust. The bottom of the furnace gas scrubbing tower 140 contains scrubbing liquid, which is pumped by scrubbing liquid pump 141 to the middle of the tower for circulating and rinsing the furnace gas. Excess scrubbing liquid is pumped by scrubbing liquid pump 141 to the ammonia stripping system.

[0047] Furthermore, such as Figure 3 As shown, the treatment system also includes a furnace gas separator 220. The inlet of the furnace gas separator 220 is connected to the outlet at the top of the furnace gas scrubbing tower 140, and the drain at the bottom of the furnace gas separator 220 is connected to the top of the furnace gas scrubbing tower 140. The furnace gas separator 220 can separate the liquid droplets entrained in the furnace gas and then transport the liquid phase back to the furnace gas scrubbing tower 140 for reuse. The scrubbed furnace gas is then sent to the furnace gas compression process by the induced draft fan 221. To overcome the resistance of the entire system, the static pressure at the inlet of the induced draft fan 221 is >8 kPa.

[0048] Optionally, such as Figure 3 As shown, the ammonia stripping system includes an ammonia stripping tower 230 and an ammonia recovery tower 240. The liquid inlet at the top of the ammonia stripping tower 230 is connected to a washing liquid pump 141, and a low-pressure steam inlet pipe is installed at the bottom of the ammonia stripping tower 230 to introduce low-pressure steam. The washing liquid that has absorbed ammonia, delivered from the furnace gas scrubbing tower 140, is pumped by the washing liquid pump 141 into the upper part of the ammonia stripping tower 230, where it comes into countercurrent contact with 0.3~0.4MPa low-pressure steam from outside the interface on the tower plate, undergoing mass and heat transfer, so that the ammonia in the washing liquid is stripped out by steam.

[0049] The top of the ammonia stripping tower 230 is equipped with an ammonia separator 231 that is connected to the ammonia stripping tower 230. The gas outlet at the top of the ammonia separator 231 is connected to the gas inlet at the bottom of the ammonia recovery tower 240. The gas outlet at the top of the ammonia recovery tower 240 is connected to the gas inlet of the furnace gas scrubbing tower 140. The stripped ammonia gas undergoes indirect heat exchange with circulating cooling water in ammonia fractionator 231, cooling the ammonia gas to 60°C. Most of the water vapor is condensed, resulting in an ammonia concentration of 70-80%. The condensate flows back to the first tray by gravity. The concentrated ammonia gas enters ammonia recovery tower 240, where it comes into countercurrent contact with the mother liquor from the ammonia absorption unit in the packing layer, undergoing mass and heat transfer. The diluted ammonia mother liquor, having absorbed all the ammonia, is sent back to the ammonia absorption unit to recover the ammonia. The unabsorbed non-condensable gases, mainly CO2, air, and a small amount of NH3, are introduced into the inlet of the furnace gas scrubbing tower 140 via pipeline. This further scrubs the ammonia while providing a certain negative pressure to the ammonia stripping system. By controlling the opening of the pressure regulating valve, the pressure at the top of the ammonia stripping tower 230 is kept below -5 kPa to reduce the operating pressure and temperature of the ammonia stripping system and decrease steam consumption.

[0050] Furthermore, such as Figure 3 As shown, the drain end at the bottom of the ammonia stripping tower 230 is connected to the hot side inlet of the feed preheater 250 via the waste desalination pump 232, and the hot side outlet of the feed preheater 250 is connected to the top of the furnace gas scrubbing tower 140. The cold side inlet of the feed preheater 250 is connected to the scrubbing liquid pump 141, and the cold side outlet is connected to the liquid inlet at the top of the ammonia stripping tower 230. The dilute ammonia wastewater drawn from the bottom of the ammonia stripping tower 230 has a temperature of 100~110℃ and an ammonia content of <20mg / L. After being pressurized to 0.5MPa by the waste desalination pump 232, it enters the feed preheater 250. While heating the feed, its own temperature is reduced to 60℃. Then, after exchanging heat with the circulating cooling water in the waste desalination cooler 251 to 35~40℃, it enters the top of the furnace gas scrubbing tower 140 for reuse as the ammonia scrubbing water of the furnace gas scrubbing tower 140.

[0051] Example 2

[0052] This embodiment provides a method for treating dust-laden furnace gas from a light ash calcining furnace, which employs the aforementioned treatment system, including:

[0053] S1. The furnace gas (approximately 100~130℃) containing alkali dust generated from calcining heavy alkali is transported to the cyclone separator 110 for preliminary separation. The separated furnace gas is transported to the lower part of the hot alkali tower 210, and the alkali dust is recovered through the bottom of the cyclone separator 110.

[0054] S2. The furnace gas enters from the lower part of the hot alkali tower 210 and comes into countercurrent contact with the hot alkali liquid entering from the upper part of the hot alkali tower 210, allowing the alkali dust carried in the furnace gas to be further transferred to the hot alkali liquid; the excess hot alkali liquid is transported to the heavy alkali process for use as filter washing water; the furnace gas output from the top of the hot alkali tower 210 is transported to the furnace gas condenser 130; the temperature of the excess hot alkali liquid output from the hot alkali tower 210 is controlled at 85~90℃ and the ammonia content is <2000mg / L. After being cooled to 30~40℃ by the hot alkali liquid cooler 212, it is transported to the heavy alkali process for use as filter washing water.

[0055] S3. The furnace gas temperature output from the hot alkali tower 210 is controlled at 85~90℃ and is sent to the furnace gas condenser 130. The furnace gas condenser 130 cools the input furnace gas to 35~40℃. Most of the water vapor in the furnace gas is condensed and sent back to the lower part of the hot alkali tower 210 as a supplement to the washing water of the hot alkali tower 210. The condensed furnace gas is sent to the bottom of the furnace gas scrubbing tower 140.

[0056] S4. The furnace gas enters from the lower part of the furnace gas scrubbing tower 140. The scrubbing liquid at the bottom of the tower is pressurized to 0.5MPa by the scrubbing liquid pump 141 and then enters the middle part of the furnace gas scrubbing tower 140. The scrubbing liquid comes into countercurrent contact with the furnace gas to scrub the ammonia in the furnace gas. The temperature of the furnace gas output from the furnace gas scrubbing tower 140 is controlled at 35~40℃ and the ammonia content is <0.6%. It enters the furnace gas separator 220, where the liquid droplets entrained in the furnace gas are separated. Then, it is sent to the furnace gas compression process by the induced draft fan 221. To overcome the resistance of the entire system, the static pressure at the inlet of the induced draft fan 221 is >8KPa. The temperature of the excess scrubbing liquid output from the furnace gas scrubbing tower 140 is controlled at 35~40℃ and the ammonia concentration is 1.5%~2%. It is heated to 80~85℃ and then sent to the ammonia stripping process to recover the ammonia.

[0057] S5. The circulating washing liquid, after absorbing ammonia, is at a temperature of 40℃ and an ammonia concentration of 1.5%~2%. It is drawn from the outlet of the washing liquid pump 141 and exchanges heat with the waste dilute liquid at 100~110℃ in the bottom of the ammonia stripping tower 230 through the feed preheater 250. After being heated to 80~85℃, the washing liquid enters the upper part of the ammonia stripping tower 230, where it comes into countercurrent contact with low-pressure steam (0.3~0.4MPa) from outside the interface on the tower plate. Mass and heat transfer occur, and the ammonia gas in the washing liquid is stripped out at a temperature of about 90~95℃. Then, it enters the ammonia fractionator 231 and exchanges heat indirectly with the circulating cooling water. The ammonia gas is cooled to 60℃, and most of the water vapor is condensed. The ammonia concentration can reach 70-80%. The condensate flows back to the first tray by gravity. The concentrated ammonia enters the ammonia recovery tower 240 and comes into countercurrent contact with the mother liquor from the ammonia absorption unit in the packing layer. Mass and heat transfer occur. The dilute ammonia mother liquor that has absorbed the ammonia is sent back to the ammonia absorption unit to recover the ammonia. The unabsorbed non-condensable gases are mainly CO2, air and a small amount of NH3. They are introduced into the inlet of the furnace gas scrubbing tower 140 through pipelines to further scrub the ammonia while providing a certain negative pressure to the ammonia stripping system. By controlling the opening of the pressure regulating valve, the pressure at the top of the ammonia stripping tower 230 is kept below -5 kPa to reduce the operating pressure and temperature of the ammonia stripping system and reduce steam consumption.

[0058] S6. The dilute ammonia wastewater drawn from the bottom of the ammonia stripping tower 230, with a temperature of 100~110℃ and an ammonia content of <20mg / L, is pressurized to 0.5MPa by the waste dilute liquid pump 232 and then enters the feed preheater 250. While heating the feed, its own temperature is reduced to 60℃. Then, it exchanges heat with the circulating cooling water in the waste dilute liquid cooler 251 to 35~40℃ before entering the top of the furnace gas scrubbing tower 140 as the ammonia washing water of the furnace gas scrubbing tower 140.

[0059] In summary, this invention provides a system and method for treating dust-laden furnace gas from a light ash calcining furnace. It replaces the energy-intensive electrostatic precipitator 120 with a hot alkali tower 210, effectively improving dust removal efficiency and significantly reducing production costs. The application of the hot alkali tower 210 further alters the operational logic and process of subsequent steps. Excess hot alkali solution from the tower is sent to the heavy alkali process as filtration washing water. Compared to the washing liquid used in existing technologies, the hot alkali solution has a lower ammonia content, effectively solving the problem of ammonia escape and environmental pollution. Simultaneously, the washing liquid, originally used as filtration washing water, is sent to the ammonia stripping system for ammonia recovery. The low alkali dust content in the washing liquid effectively avoids pipeline blockage. This treatment system and method are logically sound, achieving an overall dust removal efficiency of up to 99.75%, high ammonia recovery efficiency, low pollution, and environmental friendliness, demonstrating significant practical value.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A system for treating dust-laden furnace gas from a light ash calcining furnace, characterized in that, include; A cyclone separator, wherein the inlet end of the cyclone separator is connected to the furnace gas outlet of the calcining furnace; A hot alkali solution tower, wherein the air inlet end of the lower part of the hot alkali solution tower is connected to the air outlet end of the cyclone separator; the bottom of the hot alkali solution tower is filled with hot alkali solution, which is pumped to the middle and upper part of the hot alkali solution tower by a hot alkali solution pump for circulating and rinsing the furnace gas; the excess hot alkali solution is pumped to the heavy alkali process by the hot alkali solution pump. A furnace gas condenser, wherein the inlet end of the furnace gas condenser is connected to the outlet end of the hot alkali tower. A furnace gas scrubbing tower, wherein the air inlet at the bottom of the furnace gas scrubbing tower is connected to the air outlet at the bottom of the furnace gas condenser; the bottom of the furnace gas scrubbing tower is filled with scrubbing liquid, which is pumped to the middle of the furnace gas scrubbing tower by a scrubbing liquid pump for circulating and scrubbing the furnace gas, and excess scrubbing liquid is pumped to the ammonia stripping system by the scrubbing liquid pump. The ammonia stripping system includes an ammonia stripping tower and an ammonia recovery tower. The liquid inlet at the top of the ammonia stripping tower is connected to the washing liquid pump. A low-pressure steam inlet pipe is provided at the bottom of the ammonia stripping tower to introduce low-pressure steam. An ammonia separator is provided at the top of the ammonia stripping tower and is connected to the ammonia separator. The gas outlet at the top of the ammonia separator is connected to the gas inlet at the bottom of the ammonia recovery tower. The gas outlet at the top of the ammonia recovery tower is connected to the gas inlet at the furnace gas scrubbing tower. The drain end at the bottom of the ammonia stripping tower is connected to the hot side inlet of the feed preheater via a waste desalination pump, and the hot side outlet of the feed preheater is connected to the top of the furnace gas scrubbing tower; the cold side inlet of the feed preheater is connected to the scrubbing liquid pump, and the cold side outlet is connected to the liquid inlet at the top of the ammonia stripping tower.

2. The dust-laden gas treatment system for a light ash calcining furnace according to claim 1, characterized in that, The drain end at the bottom of the furnace gas condenser is connected to the lower part of the hot alkali tower via a condensate pump.

3. The dust-laden gas treatment system for a light ash calcining furnace according to claim 2, characterized in that, It also includes a furnace gas separator, the inlet of which is connected to the outlet at the top of the furnace gas scrubbing tower, and the drain at the bottom of which is connected to the top of the furnace gas scrubbing tower.

4. The dust-laden gas treatment system for a light ash calcining furnace according to claim 3, characterized in that, The cyclone separator includes a primary cyclone separator and a secondary cyclone separator connected in series; the inlet of the primary cyclone separator is connected to the furnace gas outlet of the calcining furnace, and the outlet of the secondary cyclone separator is connected to the inlet of the hot alkali tower.

5. A method for treating dust-laden furnace gas from a light ash calcining furnace, characterized in that, The governance system described in any one of claims 1 to 4 includes: The furnace gas containing alkali dust generated from calcining heavy alkali is conveyed to the cyclone separator for preliminary separation. The separated furnace gas is conveyed to the lower part of the hot alkali liquid tower, and the alkali dust is recovered through the bottom of the cyclone separator. The furnace gas enters from the bottom of the hot alkali solution tower and comes into countercurrent contact with the hot alkali solution entering from the top of the hot alkali solution tower, allowing the alkali dust carried in the furnace gas to be further transferred into the hot alkali solution; the excess hot alkali solution is transported to the heavy alkali process and used as filter washing water; the furnace gas output from the top of the hot alkali solution tower is transported to the furnace gas condenser. The furnace gas condenser condenses most of the water vapor in the furnace gas and sends it back to the bottom of the hot alkali tower as a supplement to the washing water of the hot alkali tower; the condensed furnace gas is then sent to the bottom of the furnace gas scrubbing tower. The furnace gas enters from the bottom of the furnace gas scrubbing tower and comes into countercurrent contact with the scrubbing liquid entering from the middle of the furnace gas scrubbing tower to scrub the ammonia in the furnace gas. The scrubbed furnace gas is then sent to the furnace gas compression process by an induced draft fan. The excess scrubbing liquid is transported to the ammonia stripping process to recover the ammonia.

6. The method for treating dust-laden furnace gas from a light ash calcining furnace according to claim 5, characterized in that, The excess hot alkali solution output from the hot alkali solution tower is controlled at a temperature of 85~90℃ and an ammonia content of <2000mg / L. After being cooled to 30~40℃, it is sent to the heavy alkali process for use as filter washing water. The furnace gas output from the hot alkali solution tower is controlled at a temperature of 85~90℃.

7. The method for treating dust-laden furnace gas from a light ash calcining furnace according to claim 5, characterized in that, The furnace gas condenser cools the input furnace gas to 35~40°C.

8. The method for treating dust-laden furnace gas from a light ash calcining furnace according to claim 5, characterized in that, The furnace gas temperature output from the furnace gas scrubbing tower is controlled at 35~40℃, and the ammonia content is <0.6%; the temperature of the excess scrubbing liquid output from the furnace gas scrubbing tower is controlled at 35~40℃, and the ammonia concentration is 1.5%~2%. After being heated to 80~85℃, it is sent to the ammonia stripping process to recover the ammonia gas.

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