Household garbage power plant fly ash salt treatment and separation system and method

Abstract

The invention discloses a household garbage power plant fly ash salt treatment and separation system and method. Comprising a plasma electric arc furnace, a secondary combustion chamber, a waste heat utilization boiler, a primary desulfurization and desalination water scrubber, a secondary desulfurization and desalination water scrubber, a neutralization desulfurization treatment device, a pressed cake separation device, a cooling tower, a membrane treatment device, a sodium chloride crystallization device, a sodium salt centrifugation device, a sodium salt drying device, a sodium salt packaging device, a potassium chloride crystallization device and a potassium salt centrifugation device. A potassium salt drying device, a potassium salt packaging device, a mother liquor drying device and a carnallite packaging device. According to the method, the salt is separated from the fly ash, so that the purity of the collected crystallized salt is high, the water consumption is greatly reduced, the energy consumption and the environmental pollution are reduced by adopting a spray cooling salt dissolving mode, the salt of the fly ash can be fully washed, and the water consumption is reduced. And the salt separated from the flue gas is crystallized after being neutralized, flocculated and subjected to reverse osmosis, and is separated into high-purity potassium chloride and sodium chloride industrial salt.

Description

Technical Field

[0001] The invention belongs to the technical field of waste gas treatment, and in particular relates to a system and method for treating and separating salt content in fly ash from a domestic waste power plant. Background Art

[0002] At present, the flue gas generated by garbage power generation contains a lot of fly ash, and the flue gas composition is relatively complex. The flue gas contains a large amount of salt, a small amount of combustible gas (CO, H2, CH4, VOC, NOx gas, etc.), trace amounts of dioxins and heavy metals, etc. In resource utilization, a large amount of water is often needed to fully wash the fly ash. Fly ash washing is to dissolve and extract potassium, sodium and chlorine in the fly ash to make secondary by-industrial products. The washed fly ash (also known as dechlorinated fly ash) is sent to the cement kiln for high-temperature calcination, and the high temperature of the cement kiln is used to solidify and decompose heavy metals and dioxins. This fly ash washing treatment method has the following problems: First, the amount of water used is huge, resulting in waste of water resources, high energy consumption, large subsequent sewage treatment volume, and great pollution to the environment; second, after the water dissolves the salt in the fly ash, it will also dissolve other harmful substances into the water. If the salt is further evaporated and crystallized, there will be a large amount of debris in the crystallized salt, and these crystallized salts cannot be used due to too many debris. Summary of the invention

[0003] In order to solve the above technical problems existing in the prior art, the present invention provides a system and method for treating and separating salt in fly ash from a domestic waste power plant with low water consumption, low energy consumption, no pollution and high salt crystal purity.

[0004] In order to solve the above technical problems, the present invention adopts the following technical scheme: a fly ash salt treatment and separation system for a domestic waste power plant, comprising a plasma arc furnace, a secondary combustion chamber, a waste heat utilization boiler, a primary desulfurization and desalting water washing tower, a secondary desulfurization and desalting water washing tower, a neutralization and desulfurization treatment device, a cake separation device, a cooling tower, a membrane treatment device, a sodium chloride crystallization device, a sodium salt centrifugal device, a sodium salt drying device, a sodium salt packaging device, a potassium chloride crystallization device, a potassium salt centrifugal device, a potassium salt drying device, a potassium salt packaging device, a mother liquor drying device and a miscellaneous salt packaging device; The smoke exhaust port of the plasma arc furnace is connected to the smoke inlet of the secondary combustion chamber, the smoke exhaust port of the secondary combustion chamber is connected to the smoke inlet of the waste heat utilization boiler, the smoke outlet of the waste heat utilization boiler is connected to the smoke inlet of the primary desulfurization and desalting water washing tower, the smoke exhaust port of the primary desulfurization and desalting water washing tower is connected to the smoke inlet of the secondary desulfurization and desalting water washing tower, and the smoke exhaust port of the secondary desulfurization and desalting water washing tower is connected to the flue gas purification system; The water outlets of the primary desulfurization and desalting water washing tower and the secondary desulfurization and desalting water washing tower are connected to the water inlet of the neutralization and desulfurization treatment device, the precipitated sludge outlet of the neutralization and desulfurization treatment device is connected to the inlet of the cake pressing separation device, the liquid in the neutralization and desulfurization treatment device is circulated and cooled through a cooling tower, the liquid outlet of the neutralization and desulfurization treatment device is connected to the liquid inlet of the membrane treatment device, the concentrated liquid outlet of the membrane treatment device is connected to the liquid inlet of the sodium chloride crystallization device, the discharge port of the sodium chloride crystallization device is connected to the sodium salt centrifugal device, the sodium salt drying device and the sodium salt packaging device in sequence, the liquid outlet of the sodium chloride crystallization device is connected to the liquid inlet of the potassium chloride crystallization device, the discharge port of the potassium chloride crystallization device is connected to the potassium salt centrifugal device, the potassium salt drying device and the potassium salt packaging device in sequence, the liquid outlet of the potassium chloride crystallization device is connected to the liquid inlet of the mother liquor drying device, and the discharge port of the mother liquor drying device is connected to the miscellaneous salt packaging device.

[0005] The steam outlet of the waste heat utilization boiler is connected to the steam inlet of the sodium chloride crystallization device; the clean water outlet of the membrane treatment device is respectively connected to the first-level spraying device in the first-level desulfurization and desalting water washing tower and the second-level spraying device in the second-level desulfurization and desalting water washing tower. The second-level desulfurization and desalting water washing tower is also equipped with a third-level spraying device, and the water source of the third-level spraying device adopts tap water.

[0006] The inner cavity of the secondary combustion chamber is in a U-shaped structure. An air inlet elbow joint is provided at the upper left end of the secondary combustion chamber, and an air outlet elbow joint is provided at the upper right end of the secondary combustion chamber. The right end of the air outlet elbow joint is connected to the flue gas inlet on the left side of the waste heat utilization boiler. A baffle heat exchange channel is provided inside the waste heat utilization boiler, and a flue gas outlet is provided on the right side of the waste heat utilization boiler. A burner installation port is provided at the upper left side of the secondary combustion chamber, and a natural gas burner is provided in the burner installation port. A first SNCR spray gun for horizontally spraying urea solution to the right is provided at the lower left side of the secondary combustion chamber, and the spraying direction of the first SNCR spray gun is along the horizontal center line of the bottom of the U-shaped inner cavity. A second SNCR spray gun for vertically spraying urea solution upward is provided at the lower right side of the secondary combustion chamber, and the spraying direction of the second SNCR spray gun is along the vertical center line of the right side of the U-shaped inner cavity. A first bracket is provided at the bottom of the secondary combustion chamber, a refractory castable layer is provided on the inner wall of the inner cavity of the secondary combustion chamber, a rock wool insulation layer is wrapped outside the secondary combustion chamber, an ash dropping pipe is provided in the middle position of the U-shaped structure at the bottom of the secondary combustion chamber, and a first valve is provided at the lower end of the ash dropping pipe.

[0007] The waste heat utilization boiler includes a second bracket, on which a furnace surrounded by an external membrane water-cooled wall is provided, an internal membrane water-cooled wall is provided in the middle of the furnace, the upper and lower ends of the internal membrane water-cooled wall are respectively connected to the top and bottom of the external membrane water-cooled wall, the internal membrane water-cooled wall divides the furnace into a left heat exchange chamber and a right heat exchange chamber, a through hole connecting the left heat exchange chamber and the right heat exchange chamber is provided at the lower part of the internal membrane water-cooled wall, the flue gas inlet is arranged at the upper left part of the external membrane water-cooled wall, the flue gas outlet is arranged at the upper right part of the external membrane water-cooled wall, a boiler drum is provided above the external membrane water-cooled wall, and the boiler drum is connected to the top of the external membrane water-cooled wall through a steam riser and a cold water downflow pipe; the flue gas inlet, the left heat exchange chamber, the through hole, the right heat exchange chamber and the flue gas outlet form a through baffle heat exchange channel; an ash hopper is provided at the bottom of the left heat exchange chamber and the right heat exchange chamber, and a second valve is provided at the lower end of the ash hopper.

[0008] The center line of the boiler drum is arranged horizontally along the left and right directions, a liquid level gauge is arranged at the left end of the boiler drum, a sewage pipe joint is arranged at the lower right end of the boiler drum, a steam outlet, a safety valve interface, a safety valve spare interface and a pressure gauge interface are arranged on the top of the boiler drum, a water supply pipe joint is arranged at the upper front part of the boiler drum, a water supply distribution pipe connected to the port in the water supply pipe joint is arranged inside the boiler drum, a water supply distribution orifice plate located below the water supply distribution pipe is arranged inside the boiler drum, and a steam-water separator connected to the steam outlet is arranged at the upper part of the boiler drum.

[0009] A method for treating and separating salt from fly ash in a domestic waste power plant is carried out using a fly ash and salt treatment and separation system in a domestic waste power plant, and comprises the following steps: (1) Domestic waste is first melted in a plasma arc furnace to remove dioxins from fly ash; (2) The flue gas discharged from the plasma arc furnace is introduced into the secondary combustion chamber to fully burn the combustible gas in the flue gas, completely decompose the undecomposed dioxins, and denitrify the flue gas at the same time; (3) The high-temperature flue gas discharged from the secondary combustion chamber after denitration is passed through the waste heat utilization boiler for cooling; (4) The flue gas discharged from the waste heat utilization boiler is sequentially passed into the primary desulfurization and desalination water washing tower and the secondary desulfurization and desalination water washing tower, and is rapidly cooled and desalted by three-stage water spraying to remove the salt and SO2 in the flue gas; the flue gas after desulfurization and desalination is further treated by the flue gas purification system and discharged into the air; (5) The brine settled in the primary desulfurization and desalting water washing tower and the secondary desulfurization and desalting water washing tower is discharged into the neutralization and desulfurization treatment device, and then discharged into the membrane treatment device for treatment; (6) The high-concentration brine is discharged into the sodium chloride crystallization device to separate the sodium salt first, and then discharged into the potassium chloride crystallization device to separate the potassium salt and, finally, the mother liquor drying device is used to separate the impurities.

[0010] The specific process of step (2) is as follows: the flue gas generated by the incineration of garbage in the plasma arc furnace is connected to the air intake elbow joint through the exhaust pipe, and the flue gas enters the inner cavity of the secondary combustion chamber. The flame ejected by the burner raises the temperature in the secondary combustion chamber to 1100°C. The combustible gas and dioxin in the flue gas are burned and decomposed at high temperature. When the flue gas passes through the lower part of the U-shaped inner cavity, the first SNCR spray gun sprays atomized urea to the right, and the second SNCR spray gun sprays atomized urea upward. The urea fully reacts with NOx in the flue gas to undergo the following chemical reaction: 4CO(NH2)2+5NO+302→4CO2+4H20+5N2, thereby removing NOx in the flue gas and achieving the purpose of synchronous denitrification; the dust in the flue gas falls into the ash falling pipe for temporary storage.

[0011] The specific process of step (3) is as follows: the pre-treated flue gas enters the waste heat utilization boiler, and the high-temperature flue gas passes through the flue gas inlet, the left heat exchange chamber, the through hole, the right heat exchange chamber and the flue gas outlet in sequence to form a through-flow heat exchange channel, and heats the water inside the external membrane water-cooled wall and the internal membrane water-cooled wall. The heated water forms water vapor and enters the boiler drum through the steam riser. After the water in the water vapor is separated into the boiler drum by the steam-water separator, the high-temperature steam that basically does not contain water is discharged through the steam outlet to provide high-temperature steam to the sodium chloride crystallization device to save energy; normal temperature water is injected through the water supply pipe joint, and first passes through the water supply distribution pipe 28 to be sprayed on the water supply distribution orifice plate to ensure that the water supply is evenly distributed in the boiler drum.

[0012] The specific process of step (4) is as follows: the 800°C flue gas discharged from the waste heat utilization boiler is passed into the primary desulfurization and desalting water washing tower, the primary spraying device arranged in the primary desulfurization and desalting water washing tower rapidly reduces the flue gas temperature to 81°C-82°C, and then the flue gas enters the secondary desulfurization and desalting water washing tower, the secondary spraying device and the tertiary spraying device arranged in the secondary desulfurization and desalting water washing tower continuously spray the flue gas, the spraying water volume of the first-stage spraying device and the second-stage spraying device are both 15t / h, and the spraying water volume of the third-stage spraying device is 2.75t / h. The water content of the flue gas after the tertiary water spraying is in an oversaturated state, the moisture content of the flue gas is 48.34%, the spraying water fully absorbs and dissolves the salt and SO2 in the flue gas, and the desalination efficiency is greater than 90%.

[0013] The specific process of step (5) is as follows: the salt water settled in the primary desulfurization and desalting water washing tower and the secondary desulfurization and desalting water washing tower first enters the desulfurization treatment device, the desulfurization treatment device includes a regulating tank and a reaction tank, the salt solution first enters the regulating tank to adjust the water volume and uniform water quality, the effluent from the regulating tank is transferred to the reaction tank, heavy metals and total hardness of calcium and magnesium are removed by adding liquid alkali or soda ash, the sludge after flocculation and precipitation enters the cake pressing separation device, the cake pressing separation device presses the sludge into a mud cake, the clear liquid on the top of the reaction tank enters the membrane treatment device, the membrane treatment device removes slag and purifies, and then enters the sodium chloride crystallization device.

[0014] The specific process of step (6) is as follows: the brine evaporates water in the MVR salt crystallizer of the sodium chloride crystallization device to concentrate the solute, and the sodium chloride first reaches saturation and precipitates. The salt slurry is transferred to the sodium chloride thickener through a discharge pump to increase the solid-liquid ratio and then enters the sodium salt centrifugal device. The wet sodium salt after centrifugal dehydration is dried by the sodium salt drying device to obtain dry sodium chloride, and then packaged by the sodium salt packaging device and temporarily stored; The brine after separation of sodium chloride enters the potassium chloride crystallization device. The MVR salt evaporator of the potassium chloride crystallization device controls the concentration of potassium chloride so that potassium chloride does not precipitate in the evaporator; the salt mother liquor is discharged from the crystallizer and sent to the primary vacuum crystallizer and the secondary vacuum crystallizer in turn, and potassium chloride is precipitated by vacuum cooling and crystallization. The potassium chloride slurry is transferred to the potassium chloride thickener through a discharge pump to increase the solid-liquid ratio and then enters the potassium salt centrifugal device. The wet potassium salt after centrifugal dehydration is dried by the potassium salt drying device to obtain dry potassium chloride, and then temporarily stored after being packaged by the potassium salt packaging device; in order to improve the recovery rate of sodium chloride and potassium chloride, the cooled mother liquor of the sodium chloride crystallization device is returned to the primary desulfurization and desalting water washing tower and the secondary desulfurization and desalting water washing tower as spray water for continuous recycling, and the evaporated mother liquor is discharged to the mother liquor drying device for drying treatment to obtain impurities.

[0015] By adopting the above technical solution, compared with the prior art, the present invention has the following technical effects: 1) The steam riser is close to the steam outlet (rising steam is easier to enter the drum), and the cold water downflow pipe is far from the steam outlet. A steam-water separator is set on the top of the drum, which separates steam and water by orifice plates and baffles. The water content of high-temperature steam does not exceed 3%, ensuring the steam quality. The water distribution pipe and water distribution orifice plate can ensure that the water is evenly distributed in the drum, so that the temperature deviation of each part in the drum is within 3°C, improving the efficiency of steam production.

[0016] 2) The secondary combustion in the secondary combustion chamber increases the flue gas temperature, which can fully burn out the combustible gases such as H2 and CO in the flue gas, and at the same time reduce the NOx in the flue gas to harmless gases such as N2 and CO2, and dioxins are also decomposed. The secondary combustion chamber adopts a U-shaped inner cavity structure, which has the following advantages: it is conducive to the balance of flue gas temperature; it can ensure that the flue gas and urea solution are fully mixed, and improve the SNCR denitrification efficiency; it is conducive to the full decomposition of dioxins and combustible gases in the flue gas; the U-shaped inner cavity wall is not easy to accumulate ash, and an ash drop pipe is set at the bottom to facilitate the discharge of sediments.

[0017] 3) The flue gas enters the waste heat utilization boiler for heat exchange, and the heat of the flue gas is utilized. The high-temperature steam generated is used for the subsequent fly ash desalination process in the flue gas. At the same time, the temperature of the high-temperature flue gas is reduced after passing through the waste heat utilization boiler, providing initial cooling for the subsequent desulfurization and desalination spraying.

[0018] 4) The furnace of the waste heat utilization boiler adopts a vertical structure, which is not easy to accumulate dust and salt inside, and is also convenient for maintenance and cleaning after long-term operation; the external membrane water-cooled wall structure is compact, saving steel and reducing a large amount of sealing castables and insulation materials; an ash hopper is set at the bottom to facilitate the cleaning of ash accumulated during long-term operation.

[0019] 5) The present invention first heats up the flue gas discharged from the plasma arc furnace to treat the combustible gas and dioxin inside, and denitrifies at the same time, and then uses the waste heat to perform heat exchange and cooling treatment on the high-temperature flue gas in the boiler, laying the foundation for the subsequent desulfurization and desalination spraying process. At the same time, the high-temperature steam generated is used for the fly ash desalination process in the subsequent flue gas, achieving multiple goals at one stroke.

[0020] In summary, the present invention adopts the principle of spraying water mist (three-stage spraying device in the primary desulfurization and desalting water washing tower and the secondary desulfurization and desalting water washing tower) to cool the gaseous salt into liquid salt and then dissolve it in the water mist. The salt is first separated from the fly ash, which can ensure that the purity of the crystallized salt after collection is high. The spray cooling and salt dissolving method greatly reduces the water consumption, energy consumption and environmental pollution, and the salt in the fly ash can be fully washed with water. The salt separated from the flue gas is crystallized into high-purity salt after neutralization, flocculation and reverse osmosis. As industrial salt, the salt contains sodium chloride and potassium chloride, which are further separated and utilized. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the planar layout structure of the present invention; Figure 2 yes Figure 1 Schematic diagram of the structure of the secondary combustion chamber and the heat utilization boiler; Figure 3 yes Figure 2 Enlarged view of the middle boiler drum. DETAILED DESCRIPTION

[0022] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings and examples.

[0023] like Figure 1 , Figure 2 and Figure 3 As shown, a fly ash salt treatment and separation system for a domestic waste power plant of the present invention comprises a plasma arc furnace 32, a secondary combustion chamber 1, a waste heat utilization boiler 33, a primary desulfurization and desalting water washing tower 34, a secondary desulfurization and desalting water washing tower 35, a neutralization and desulfurization treatment device 36, a cake separation device 37, a cooling tower 38, a membrane treatment device 39, a sodium chloride crystallization device 40, a sodium salt centrifugal device 41, a sodium salt drying device 42, a sodium salt packaging device 43, a potassium chloride crystallization device 44, a potassium salt centrifugal device 45, a potassium salt drying device 46, a potassium salt packaging device 47, a mother liquor drying device 48 and a miscellaneous salt packaging device 49; The smoke exhaust port of the plasma arc furnace 32 is connected to the smoke inlet of the secondary combustion chamber 1, the smoke exhaust port of the secondary combustion chamber 1 is connected to the smoke inlet of the waste heat utilization boiler 33, the smoke outlet of the waste heat utilization boiler 33 is connected to the smoke inlet of the primary desulfurization and desalting water washing tower 34, the smoke exhaust port of the primary desulfurization and desalting water washing tower 34 is connected to the smoke inlet of the secondary desulfurization and desalting water washing tower 35, and the smoke exhaust port of the secondary desulfurization and desalting water washing tower 35 is connected to the smoke purification system; The water outlets of the primary desulfurization and desalting water washing tower 34 and the secondary desulfurization and desalting water washing tower 35 are connected to the water inlet of the neutralization and desulfurization treatment device 36, the precipitated sludge outlet of the neutralization and desulfurization treatment device 36 is connected to the inlet of the cake separation device 37, the liquid in the neutralization and desulfurization treatment device 36 is circulated and cooled through the cooling tower 38, the liquid outlet of the neutralization and desulfurization treatment device 36 is connected to the liquid inlet of the membrane treatment device 39, the concentrated liquid outlet of the membrane treatment device 39 is connected to the liquid inlet of the sodium chloride crystallization device 40, and the sodium chloride crystallization device 40 is connected to the sodium chloride crystallization device 40. The discharge port of the device 40 is connected to the sodium salt centrifugal device 41, the sodium salt drying device 42 and the sodium salt packaging device 43 in sequence, the liquid outlet of the sodium chloride crystallization device 40 is connected to the liquid inlet of the potassium chloride crystallization device 44, the discharge port of the potassium chloride crystallization device 44 is connected to the potassium salt centrifugal device 45, the potassium salt drying device 46 and the potassium salt packaging device 47 in sequence, the liquid outlet of the potassium chloride crystallization device 44 is connected to the liquid inlet of the mother liquor drying device 48, and the discharge port of the mother liquor drying device 48 is connected to the impurity salt packaging device 49.

[0024] The steam outlet of the waste heat utilization boiler 33 is connected to the steam inlet of the sodium chloride crystallization device 40; the clean water outlet of the membrane treatment device 39 is respectively connected to the first-level spraying device 50 in the first-level desulfurization and desalting water washing tower 34 and the second-level spraying device 51 in the second-level desulfurization and desalting water washing tower 35. The second-level desulfurization and desalting water washing tower 35 is also provided with a third-level spraying device 52, and the water source of the third-level spraying device 52 adopts tap water.

[0025] The inner cavity of the secondary combustion chamber 1 is in a U-shaped structure, an air inlet elbow joint 2 is provided at the upper left end of the secondary combustion chamber 1, an air outlet elbow joint 3 is provided at the upper right end of the secondary combustion chamber 1, the right end of the air outlet elbow joint 3 is connected to the flue gas inlet 4 on the left side of the waste heat utilization boiler 33, a baffle heat exchange channel is provided inside the waste heat utilization boiler 33, and a flue gas outlet 5 is provided on the right side of the waste heat utilization boiler 33; A burner installation port 6 is provided at the upper left side of the secondary combustion chamber 1, and a natural gas burner 7 is provided in the burner installation port 6. A first SNCR spray gun 8 for horizontally spraying urea solution to the right is provided at the lower left side of the secondary combustion chamber 1, and the spraying direction of the first SNCR spray gun 8 is along the horizontal center line of the bottom of the U-shaped inner cavity. A second SNCR spray gun 9 for vertically spraying urea solution upward is provided at the lower right side of the secondary combustion chamber 1, and the spraying direction of the second SNCR spray gun 9 is along the vertical center line of the right side of the U-shaped inner cavity. A first bracket 10 is provided at the bottom of the secondary combustion chamber 1, a refractory castable layer is provided on the inner wall of the inner cavity of the secondary combustion chamber 1, a rock wool insulation layer is wrapped on the outside of the secondary combustion chamber 1, an ash dropping pipe 11 is provided in the middle position of the U-shaped structure at the bottom of the secondary combustion chamber 1, and a first valve is provided at the lower end of the ash dropping pipe 11.

[0026] The waste heat utilization boiler 33 includes a second support 12, on which a furnace surrounded by an external membrane water-cooled wall 13 is provided, and an internal membrane water-cooled wall 14 is provided in the middle of the furnace, and the upper and lower ends of the internal membrane water-cooled wall 14 are respectively connected to the top and bottom of the external membrane water-cooled wall 13, and the internal membrane water-cooled wall 14 divides the furnace into a left heat exchange chamber 15 and a right heat exchange chamber 16, and a through hole 17 connecting the left heat exchange chamber 15 and the right heat exchange chamber 16 is provided at the lower part of the internal membrane water-cooled wall 14, and the flue gas inlet 4 is provided at the external membrane water-cooled wall 13. The flue gas outlet 5 is arranged at the upper left side of the water-cooled wall 13, and the flue gas outlet 5 is arranged at the upper right side of the external membrane water-cooled wall 13. A boiler drum 18 is arranged above the external membrane water-cooled wall 13, and the boiler drum 18 is connected to the top of the external membrane water-cooled wall 13 through a steam riser 19 and a cold water downflow pipe 20; the flue gas inlet 4, the left heat exchange chamber 15, the through hole 17, the right heat exchange chamber 16 and the flue gas outlet 5 form a through baffle heat exchange channel; an ash hopper 31 is arranged at the bottom of the left heat exchange chamber 15 and the right heat exchange chamber 16, and a second valve is arranged at the lower end of the ash hopper 31.

[0027] The center line of the boiler drum 18 is arranged horizontally along the left-right direction, a liquid level gauge 21 is arranged at the left end of the boiler drum 18, a sewage pipe joint 22 is arranged at the lower right end of the boiler drum 18, a steam outlet 23, a safety valve interface 24, a safety valve spare interface 25 and a pressure gauge interface 26 are arranged at the top of the boiler drum 18, a water supply pipe joint 27 is arranged at the upper front side of the boiler drum 18, a water supply distribution pipe 28 connected to the inner port of the water supply pipe joint 27 is arranged inside the boiler drum 18, a water supply distribution orifice plate 29 located below the water supply distribution pipe 28 is arranged inside the boiler drum 18, and a steam-water separator 30 connected to the steam outlet 23 is arranged at the upper inner part of the boiler drum 18.

[0028] A method for treating and separating salt from fly ash in a domestic waste power plant is carried out using a fly ash and salt treatment and separation system in a domestic waste power plant, and comprises the following steps: (1) The domestic waste is first melted in a plasma arc furnace 32 to remove dioxins from the fly ash; (2) The flue gas discharged from the plasma arc furnace 32 is introduced into the secondary combustion chamber 1, where the combustible gas in the flue gas is fully burned, the undecomposed dioxins are completely decomposed, and the flue gas is denitrated at the same time; (3) The high-temperature flue gas discharged from the secondary combustion chamber 1 after denitration is passed into the waste heat utilization boiler 33 for cooling; (4) The flue gas discharged from the waste heat utilization boiler 33 is sequentially passed into the primary desulfurization and desalination water washing tower 34 and the secondary desulfurization and desalination water washing tower 35 to be rapidly cooled and desalted by three-stage water spraying; the flue gas after desulfurization and desalination is further processed by the flue gas purification system and discharged into the air; (5) The salt water settled in the primary desulfurization and desalting water washing tower and the secondary desulfurization and desalting water washing tower 35 is discharged into the neutralization and desulfurization treatment device 36, and then discharged into the membrane treatment device 39 for treatment; (6) The high-concentration brine is discharged into the sodium chloride crystallization device 40 to separate the sodium salt first, and then discharged into the potassium chloride crystallization device 44 to separate the potassium salt and, finally, the mother liquor drying device 48 is used to separate the impurity salt.

[0029] The specific process of step (2) is as follows: the flue gas generated by the incineration of garbage in the plasma arc furnace 32 is connected to the air intake elbow joint 2 through the exhaust pipe, and the flue gas enters the inner cavity of the secondary combustion chamber 1. The flame ejected by the burner 7 raises the temperature in the secondary combustion chamber 1 to 1100°C. The combustible gas and dioxin in the flue gas are burned and decomposed at high temperature. When the flue gas passes through the lower part of the U-shaped inner cavity, the first SNCR spray gun 8 sprays atomized urea to the right, and the second SNCR spray gun 9 sprays atomized urea upward. The urea fully reacts with NOx in the flue gas to undergo the following chemical reaction: 4CO(NH2)2+5NO+302→4CO2+4H20+5N2, thereby removing NOx in the flue gas and achieving the purpose of synchronous denitrification; the dust in the flue gas falls into the ash falling pipe 11 for temporary storage.

[0030] The specific process of step (3) is as follows: the pre-treated flue gas enters the waste heat utilization boiler 33, and the high-temperature flue gas passes through the flue gas inlet 4, the left heat exchange chamber 15, the through hole 17, the right heat exchange chamber 16 and the flue gas outlet 5 in sequence to form a through-flow heat exchange channel, and heats the water inside the external membrane water-cooled wall 13 and the internal membrane water-cooled wall 14. The heated water forms water vapor and enters the boiler drum 18 through the steam riser 19. After the water in the water vapor is separated into the boiler drum 18 by the steam-water separator 30, the high-temperature steam that basically does not contain water is discharged through the steam outlet 23 to provide high-temperature steam to the sodium chloride crystallization device 40 to save energy; normal temperature water is injected through the water supply pipe joint 27, and first passes through the water supply distribution pipe 2828 to be sprayed on the water supply distribution orifice plate 29 to ensure that the water supply is evenly distributed in the boiler drum 18.

[0031] The specific process of step (4) is as follows: the waste heat utilization boiler 33 discharges 800°C flue gas into the primary desulfurization and desalting water washing tower 34, the primary spraying device 50 arranged in the primary desulfurization and desalting water washing tower 34 rapidly reduces the flue gas temperature to 81°C-82°C, and then the flue gas enters the secondary desulfurization and desalting water washing tower 35, the secondary spraying device 51 and the tertiary spraying device 52 arranged in the secondary desulfurization and desalting water washing tower 35 continuously spray the flue gas, the spraying water volume of the first-stage spraying device 50 and the spraying water volume of the second-stage spraying device 51 are both 15t / h, and the spraying water volume of the third-stage spraying device 52 is 2.75t / h. The water content of the flue gas after the tertiary water spraying is in an oversaturated state, the moisture content of the flue gas is 48.34%, the spraying water fully absorbs and dissolves the salt and SO2 in the flue gas, and the desalination efficiency is greater than 90%.

[0032] The specific process of step (5) is as follows: the salt water precipitated from the primary desulfurization and desalting water washing tower 34 and the secondary desulfurization and desalting water washing tower 35 first enters the desulfurization treatment device, the desulfurization treatment device includes a regulating tank and a reaction tank, the salt solution first enters the regulating tank to adjust the water volume and uniform water quality, the effluent from the regulating tank is transferred to the reaction tank, heavy metals and total hardness of calcium and magnesium are removed by adding liquid alkali or soda ash, the sludge after flocculation and precipitation enters the cake pressing separation device 37, the cake pressing separation device 37 presses the sludge into a mud cake, the clear liquid on the top of the reaction tank enters the membrane treatment device 39, the membrane treatment device 39 removes slag and purifies, and then enters the sodium chloride crystallization device 40.

[0033] The specific process of step (6) is as follows: the brine evaporates water in the MVR salt crystallizer of the sodium chloride crystallization device 40 to concentrate the solute, and the sodium chloride first reaches saturation and precipitates. The salt slurry is transferred to the sodium chloride thickener through a discharge pump to increase the solid-liquid ratio and then enters the sodium salt centrifugal device 41. The wet sodium salt after centrifugal dehydration is dried by the sodium salt drying device 42 to obtain dry sodium chloride, and then packaged by the sodium salt packaging device 43 and temporarily stored; The salt water after separation of sodium chloride enters the potassium chloride crystallizer 44. The MVR salt evaporator of the potassium chloride crystallizer 44 controls the concentration of potassium chloride so that potassium chloride does not precipitate in the evaporator. The salt mother liquor is discharged from the crystallizer and sent to the primary vacuum crystallizer and the secondary vacuum crystallizer in sequence. Potassium chloride is crystallized and precipitated by vacuum cooling. The potassium chloride slurry is transferred to the potassium chloride thickener through a discharge pump to increase the solid-liquid ratio and then enters the potassium salt centrifugal device 45. The wet potassium salt after centrifugal dehydration is dried by the potassium salt drying device 46 to obtain dry potassium chloride, and then temporarily stored after being packaged by the potassium salt packaging device 47. In order to improve the recovery rate of sodium chloride and potassium chloride, the cooled mother liquor of the sodium chloride crystallizer 40 is returned to the primary desulfurization and desalting water washing tower 34 and the secondary desulfurization and desalting water washing tower 35 as spray water for continuous circulation, and the evaporated mother liquor is discharged to the mother liquor drying device 48 for drying treatment to obtain impure salt. Figure 2 The single arrow in the middle points to the direction of flue gas flow. Figure 3The single arrow indicates the direction of water flow, and the double arrow indicates the direction of steam flow.

[0034] The above embodiments illustrate the basic principles and features of the present invention, but the above only illustrates the preferred embodiments of the present invention and is not limited to the embodiments. Under the inspiration of this patent, a person skilled in the art can make many forms of deformation and improvement without departing from the scope of protection of the present invention and the claims, which are all within the protection scope of the present invention. Therefore, the patent and protection scope of the present invention shall be subject to the attached claims.

Claims

1. A fly ash salt treatment and separation system for a domestic waste power plant, characterized by: It includes a plasma arc furnace, a secondary combustion chamber, a waste heat utilization boiler, a primary desulfurization and desalting water washing tower, a secondary desulfurization and desalting water washing tower, a neutralization and desulfurization treatment device, a cake separation device, a cooling tower, a membrane treatment device, a sodium chloride crystallization device, a sodium salt centrifugal device, a sodium salt drying device, a sodium salt packaging device, a potassium chloride crystallization device, a potassium salt centrifugal device, a potassium salt drying device, a potassium salt packaging device, a mother liquor drying device and a miscellaneous salt packaging device; The smoke exhaust port of the plasma arc furnace is connected to the smoke inlet of the secondary combustion chamber, the smoke exhaust port of the secondary combustion chamber is connected to the smoke inlet of the waste heat utilization boiler, the smoke outlet of the waste heat utilization boiler is connected to the smoke inlet of the primary desulfurization and desalting water washing tower, the smoke exhaust port of the primary desulfurization and desalting water washing tower is connected to the smoke inlet of the secondary desulfurization and desalting water washing tower, and the smoke exhaust port of the secondary desulfurization and desalting water washing tower is connected to the flue gas purification system; The water outlets of the primary desulfurization and desalting water washing tower and the secondary desulfurization and desalting water washing tower are connected to the water inlet of the neutralization and desulfurization treatment device, the precipitated sludge outlet of the neutralization and desulfurization treatment device is connected to the inlet of the cake pressing separation device, the liquid in the neutralization and desulfurization treatment device is circulated and cooled through a cooling tower, the liquid outlet of the neutralization and desulfurization treatment device is connected to the liquid inlet of the membrane treatment device, the concentrated liquid outlet of the membrane treatment device is connected to the liquid inlet of the sodium chloride crystallization device, the discharge port of the sodium chloride crystallization device is connected to the sodium salt centrifugal device, the sodium salt drying device and the sodium salt packaging device in sequence, the liquid outlet of the sodium chloride crystallization device is connected to the liquid inlet of the potassium chloride crystallization device, the discharge port of the potassium chloride crystallization device is connected to the potassium salt centrifugal device, the potassium salt drying device and the potassium salt packaging device in sequence, the liquid outlet of the potassium chloride crystallization device is connected to the liquid inlet of the mother liquor drying device, and the discharge port of the mother liquor drying device is connected to the miscellaneous salt packaging device.

2. A fly ash salt treatment and separation system for a domestic waste power plant according to claim 1, characterized in that: The steam outlet of the waste heat utilization boiler is connected to the steam inlet of the sodium chloride crystallization device; the clean water outlet of the membrane treatment device is respectively connected to the first-level spraying device in the first-level desulfurization and desalting water washing tower and the second-level spraying device in the second-level desulfurization and desalting water washing tower. The second-level desulfurization and desalting water washing tower is also equipped with a third-level spraying device, and the water source of the third-level spraying device adopts tap water.

3. A fly ash salt treatment and separation system for a domestic waste power plant according to claim 3, characterized in that: The inner cavity of the secondary combustion chamber is in a U-shaped structure. An air inlet elbow joint is provided at the upper left end of the secondary combustion chamber, and an air outlet elbow joint is provided at the upper right end of the secondary combustion chamber. The right end of the air outlet elbow joint is connected to the flue gas inlet on the left side of the waste heat utilization boiler. A baffle heat exchange channel is provided inside the waste heat utilization boiler, and a flue gas outlet is provided on the right side of the waste heat utilization boiler. A burner installation port is provided at the upper left side of the secondary combustion chamber, and a natural gas burner is provided in the burner installation port. A first SNCR spray gun for horizontally spraying urea solution to the right is provided at the lower left side of the secondary combustion chamber, and the spraying direction of the first SNCR spray gun is along the horizontal center line of the bottom of the U-shaped inner cavity. A second SNCR spray gun for vertically spraying urea solution upward is provided at the lower right side of the secondary combustion chamber, and the spraying direction of the second SNCR spray gun is along the vertical center line of the right side of the U-shaped inner cavity.

4. A fly ash salt treatment and separation system for a domestic waste power plant according to claim 3, characterized in that: The waste heat utilization boiler includes a second bracket, on which a furnace surrounded by an external membrane water-cooled wall is provided, an internal membrane water-cooled wall is provided in the middle of the furnace, the upper and lower ends of the internal membrane water-cooled wall are respectively connected to the top and bottom of the external membrane water-cooled wall, the internal membrane water-cooled wall divides the furnace into a left heat exchange chamber and a right heat exchange chamber, a through hole connecting the left heat exchange chamber and the right heat exchange chamber is provided at the lower part of the internal membrane water-cooled wall, the flue gas inlet is arranged at the upper left part of the external membrane water-cooled wall, the flue gas outlet is arranged at the upper right part of the external membrane water-cooled wall, a boiler drum is provided above the external membrane water-cooled wall, and the boiler drum is connected to the top of the external membrane water-cooled wall through a steam riser and a cold water downflow pipe; the flue gas inlet, the left heat exchange chamber, the through hole, the right heat exchange chamber and the flue gas outlet form a through baffle heat exchange channel; an ash hopper is provided at the bottom of the left heat exchange chamber and the right heat exchange chamber, and a second valve is provided at the lower end of the ash hopper.

5. A fly ash salt treatment and separation system for a domestic waste power plant according to claim 4, characterized in that: The center line of the boiler drum is arranged horizontally along the left and right directions, a liquid level gauge is arranged at the left end of the boiler drum, a sewage pipe joint is arranged at the lower right end of the boiler drum, a steam outlet, a safety valve interface, a safety valve spare interface and a pressure gauge interface are arranged on the top of the boiler drum, a water supply pipe joint is arranged at the upper front part of the boiler drum, a water supply distribution pipe connected to the port in the water supply pipe joint is arranged inside the boiler drum, a water supply distribution orifice plate located below the water supply distribution pipe is arranged inside the boiler drum, and a steam-water separator connected to the steam outlet is arranged at the upper part of the boiler drum.

6. A method for treating and separating salts from fly ash in a domestic waste power plant, using the system for treating and separating salts from fly ash in a domestic waste power plant as claimed in claim 5, characterized in that: The following steps are involved: (1) Domestic waste is first melted in a plasma arc furnace to remove dioxins from fly ash; (2) The flue gas discharged from the plasma arc furnace is introduced into the secondary combustion chamber to fully burn the combustible gas in the flue gas, completely decompose the undecomposed dioxins, and denitrify the flue gas at the same time; (3) The high-temperature flue gas discharged from the secondary combustion chamber after denitration is passed through the waste heat utilization boiler for cooling; (4) The flue gas discharged from the waste heat utilization boiler is sequentially passed into the primary desulfurization and desalination water washing tower and the secondary desulfurization and desalination water washing tower, and is rapidly cooled and desalted by three-stage water spraying to remove the salt and SO2 in the flue gas; the flue gas after desulfurization and desalination is further treated by the flue gas purification system and discharged into the air; (5) The brine settled in the primary desulfurization and desalting water washing tower and the secondary desulfurization and desalting water washing tower is discharged into the neutralization and desulfurization treatment device, and then discharged into the membrane treatment device for treatment; (6) The high-concentration brine is discharged into the sodium chloride crystallization device to separate the sodium salt first, and then discharged into the potassium chloride crystallization device to separate the potassium salt and, finally, the mother liquor drying device is used to separate the impurities.

7. A method for treating and separating salts from fly ash in a domestic waste power plant according to claim 6, characterized in that: The specific process of step (2) is as follows: the flue gas generated by the incineration of garbage in the plasma arc furnace is connected to the air intake elbow joint through the exhaust pipe, and the flue gas enters the inner cavity of the secondary combustion chamber. The flame ejected by the burner raises the temperature in the secondary combustion chamber to 1100°C. The combustible gas and dioxin in the flue gas are burned and decomposed at high temperature. When the flue gas passes through the lower part of the U-shaped inner cavity, the first SNCR spray gun sprays atomized urea to the right, and the second SNCR spray gun sprays atomized urea upward. The urea fully reacts with NOx in the flue gas to undergo the following chemical reaction: 4CO(NH2)2+5NO+302→4CO2+4H20+5N2, thereby removing NOx in the flue gas and achieving the purpose of synchronous denitrification; the dust in the flue gas falls into the ash falling pipe for temporary storage; The specific process of step (3) is as follows: the pre-treated flue gas enters the waste heat utilization boiler, and the high-temperature flue gas passes through the flue gas inlet, the left heat exchange chamber, the through hole, the right heat exchange chamber and the flue gas outlet in sequence to form a through-flow heat exchange channel, and heats the water inside the external membrane water-cooled wall and the internal membrane water-cooled wall. The heated water forms water vapor and enters the boiler drum through the steam riser. After the water in the water vapor is separated into the boiler drum by the steam-water separator, the high-temperature steam that basically does not contain water is discharged through the steam outlet to provide high-temperature steam to the sodium chloride crystallization device to save energy; normal temperature water is injected through the water supply pipe joint, and first sprayed onto the water supply distribution orifice plate through the water supply distribution pipe to ensure that the water supply is evenly distributed in the boiler drum.

8. A method for treating and separating salt in fly ash from a domestic waste power plant according to claim 7, characterized in that: The specific process of step (4) is as follows: the 800°C flue gas discharged from the waste heat utilization boiler is passed into the primary desulfurization and desalting water washing tower, the primary spraying device arranged in the primary desulfurization and desalting water washing tower rapidly reduces the flue gas temperature to 81°C-82°C, and then the flue gas enters the secondary desulfurization and desalting water washing tower, the secondary spraying device and the tertiary spraying device arranged in the secondary desulfurization and desalting water washing tower continuously spray the flue gas, the spraying water volume of the first-stage spraying device and the second-stage spraying device are both 15t / h, and the spraying water volume of the third-stage spraying device is 2.75t / h. The water content of the flue gas after the tertiary water spraying is in an oversaturated state, the moisture content of the flue gas is 48.34%, the spraying water fully absorbs and dissolves the salt and SO2 in the flue gas, and the desalination efficiency is greater than 90%.

9. A method for treating and separating salts from fly ash in a domestic waste power plant according to claim 8, characterized in that: The specific process of step (5) is as follows: the salt water settled in the primary desulfurization and desalting water washing tower and the secondary desulfurization and desalting water washing tower first enters the desulfurization treatment device, the desulfurization treatment device includes a regulating tank and a reaction tank, the salt solution first enters the regulating tank to adjust the water volume and uniform water quality, the effluent from the regulating tank is transferred to the reaction tank, heavy metals and total hardness of calcium and magnesium are removed by adding liquid alkali or soda ash, the sludge after flocculation and precipitation enters the cake pressing separation device, the cake pressing separation device presses the sludge into a mud cake, the clear liquid on the top of the reaction tank enters the membrane treatment device, the membrane treatment device removes slag and purifies, and then enters the sodium chloride crystallization device.

10. A method for treating and separating salt in fly ash from a domestic waste power plant according to claim 9, characterized in that: The specific process of step (6) is as follows: the brine evaporates water in the MVR salt crystallizer of the sodium chloride crystallization device to concentrate the solute, and the sodium chloride first reaches saturation and precipitates. The salt slurry is transferred to the sodium chloride thickener through a discharge pump to increase the solid-liquid ratio and then enters the sodium salt centrifugal device. The wet sodium salt after centrifugal dehydration is dried by the sodium salt drying device to obtain dry sodium chloride, and then packaged by the sodium salt packaging device and temporarily stored; The brine after separation of sodium chloride enters the potassium chloride crystallization device. The MVR salt evaporator of the potassium chloride crystallization device controls the concentration of potassium chloride so that potassium chloride does not precipitate in the evaporator; the salt mother liquor is discharged from the crystallizer and sent to the primary vacuum crystallizer and the secondary vacuum crystallizer in turn, and potassium chloride is precipitated by vacuum cooling and crystallization. The potassium chloride slurry is transferred to the potassium chloride thickener through a discharge pump to increase the solid-liquid ratio and then enters the potassium salt centrifugal device. The wet potassium salt after centrifugal dehydration is dried by the potassium salt drying device to obtain dry potassium chloride, and then temporarily stored after being packaged by the potassium salt packaging device; in order to improve the recovery rate of sodium chloride and potassium chloride, the cooled mother liquor of the sodium chloride crystallization device is returned to the primary desulfurization and desalting water washing tower and the secondary desulfurization and desalting water washing tower as spray water for continuous recycling, and the evaporated mother liquor is discharged to the mother liquor drying device for drying treatment to obtain impurities.

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