Secondary combustion chamber and waste heat boiler combined pretreatment system for plasma furnace flue gas

Abstract

The invention discloses a secondary combustion chamber and waste heat boiler combined pretreatment system for plasma furnace flue gas. The system comprises a secondary combustion chamber and a waste heat utilization boiler. An inner cavity of the secondary combustion chamber is of a U-shaped structure, an air inlet elbow joint is arranged at the upper end of the left side of the secondary combustion chamber, an air outlet elbow joint is arranged at the upper end of the right side of the secondary combustion chamber, and the right end of the air outlet elbow joint is connected with a smoke inlet in the left side of the waste heat utilization boiler. A smoke outlet is formed in the right side of the waste heat utilization boiler. The device is scientific in principle and compact in structure, flue gas exhausted by the plasma furnace is heated, combustible gas and dioxin in the flue gas are treated, denitration is conducted at the same time, then heat exchange cooling treatment is conducted on the high-temperature flue gas through the waste heat utilization boiler, a foundation is laid for the follow-up desulfurization, desalination and spraying procedures, and the device is suitable for industrial production. And meanwhile, the generated high-temperature steam is used for the subsequent process of desalting fly ash in flue gas, so that multiple purposes are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of waste gas treatment, and in particular relates to a secondary combustion chamber and waste heat boiler combined pretreatment system for plasma furnace flue gas. Background Art

[0002] At present, the flue gas generated by the incineration of domestic waste in a plasma furnace (plasma arc furnace) 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. Therefore, the flue gas generated by the plasma furnace needs to be further treated. The current treatment method requires a large amount of water to fully wash the fly ash. The fly ash washing is to dissolve and extract the potassium, sodium and chlorine in the fly ash to make a secondary by-industrial product. 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 treatment method not only consumes a lot of water and energy, but also the resulting crystalline salt cannot be used due to too much debris. Summary of the invention

[0003] In order to solve the above technical problems existing in the prior art, the present invention provides a combined pretreatment system of a secondary combustion chamber and a waste heat boiler for plasma furnace flue gas, which consumes little energy and removes combustible gases, nitrates and dioxins in the flue gas first.

[0004] In order to solve the above technical problems, the present invention adopts the following technical scheme: a combined pretreatment system of a secondary combustion chamber and a waste heat boiler for plasma furnace flue gas, including a secondary combustion chamber and a waste heat utilization boiler; the inner cavity of the secondary combustion chamber is a U-shaped structure, an air inlet elbow joint is provided at the upper left end of the secondary combustion chamber, 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.

[0005] 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.

[0006] 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 end and the lower end of the internal membrane water-cooled wall are respectively connected to the top and the 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.

[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 dust 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 dust hopper.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] In summary, the present invention has a scientific principle and a compact structure. The flue gas discharged from the plasma furnace is first heated to treat the combustible gas and dioxin inside and denitrify at the same time. Then, the high-temperature flue gas is subjected to heat exchange and cooling treatment by utilizing the waste heat from the boiler, thereby 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 yes Figure 1 Enlarged view of the middle boiler drum. DETAILED DESCRIPTION

[0016] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings and examples.

[0017] like Figure 1 and Figure 2 As shown, the secondary combustion chamber and waste heat boiler combined pretreatment system of plasma furnace flue gas of the present invention includes a secondary combustion chamber 1 and a waste heat utilization boiler; the inner cavity of the secondary combustion chamber 1 is 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, a baffle heat exchange channel is provided inside the waste heat utilization boiler, and a flue gas outlet 5 is provided on the right side of the waste heat utilization boiler.

[0018] A burner mounting 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 mounting 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.

[0019] 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 outside 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.

[0020] The waste heat utilization boiler 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. 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. The internal membrane water-cooled wall 14 divides the furnace into a left heat exchange chamber 15 and a right heat exchange chamber 16. The lower part of the internal membrane water-cooled wall 14 is provided with a The through hole 17, the flue gas inlet 4 is arranged at the upper left part of the external membrane water-cooled wall 13, the flue gas outlet 5 is arranged at the upper right part of the external membrane water-cooled wall 13, and 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.

[0021] 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.

[0022] A dust hopper 31 is provided at the bottom of the left heat exchange chamber 15 and the right heat exchange chamber 16 , and a second valve is provided at the lower end of the dust hopper 31 .

[0023] The working process of the present invention is as follows: the flue gas generated by the incineration of garbage in a plasma furnace is connected to the air intake elbow joint 2 through a smoke exhaust pipe, and the flue gas enters the inner cavity of the secondary combustion chamber 1. The flame sprayed by the burner 7 raises the temperature in the secondary combustion chamber 1 to 1100°C, and 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 produce 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 pipe 11 for temporary storage, and the pre-treated flue gas enters the waste heat utilization boiler. 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, heating 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 drum 18 through the steam riser 19. After the water in the water vapor is separated into the 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 and used for the MVR evaporator of the subsequent flue gas desalination system to save energy. Normal temperature water is injected through the water supply pipe joint 27, and first sprayed on the water supply distribution orifice plate 29 through the water supply distribution pipe 28 to ensure that the water supply is evenly distributed in the drum 18. Figure 1 The single arrow in the middle points to the direction of flue gas flow. Figure 2 The single arrow indicates the direction of water flow, and the double arrow indicates the direction of steam flow.

[0024] 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. The secondary combustion chamber and waste heat boiler combined pretreatment system of plasma furnace flue gas is characterized by: It includes a secondary combustion chamber and a waste heat utilization boiler; 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, 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.

2. The plasma furnace flue gas secondary combustion chamber and waste heat boiler combined pretreatment system according to claim 1 is characterized in that: 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.

3. The plasma furnace flue gas secondary combustion chamber and waste heat boiler combined pretreatment system according to claim 2, characterized in that: 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.

4. The plasma furnace flue gas secondary combustion chamber and waste heat boiler combined pretreatment system according to claim 1, 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 end and the lower end of the internal membrane water-cooled wall are respectively connected to the top and the 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.

5. The plasma furnace flue gas secondary combustion chamber and waste heat boiler combined pretreatment system 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. The plasma furnace flue gas secondary combustion chamber and waste heat boiler combined pretreatment system according to claim 4 or 5, characterized in that: 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.

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