Acid-alkali waste liquid treatment system and treatment process

Abstract

The acid-alkali waste liquid treatment system comprises an incinerator, an electric dust removal device and a cloth bag dust removal device which are sequentially communicated in the flue gas direction, an induced draft fan is arranged on an outlet pipe of the cloth bag dust removal device and used for guiding flue gas to a chimney, and a low-temperature denitration catalyst unit is fixedly arranged in an internal air flue of the induced draft fan. The catalyst unit is arranged perpendicular to the flowing direction of flue gas, and the induced draft fan is configured to realize a flue gas conveying function and a catalytic reaction function at the same time; a denitration device is arranged between the bag dust removal device and the induced draft fan, an air inlet of the denitration device is in sealed connection with an outlet pipe of the bag dust removal device, and an air outlet of the denitration device is in sealed connection with an air inlet of the induced draft fan. The low-temperature denitration device has the beneficial effects that the low-temperature denitration catalyst unit is embedded in the induced draft fan, and a traditional independent denitration device and power equipment are combined into a whole, so that a system pipeline is simplified, and the occupied space is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical industry, in particular to an acid-alkali waste liquid treatment system and treatment process. BACKGROUND

[0002] The waste liquid which needs to be disposed of in the current zero-emission park covers more than ten kinds of high-risk media such as alkyl ketone residual liquid, polyol rectification heavy component, caprolactam ammonium sulfate mother liquor, etc. The core challenge lies in the mutual exclusion of components and the volatility of heat value. Acidic and alkaline waste liquid will have a violent neutralization reaction in the mixing tank, releasing a large amount of heat and generating crystalline salt such as sodium sulfate, causing pipeline blockage and tank corrosion; sodium salt, potassium salt and organic salt coexist in the waste liquid, and when incinerated, the molten salt forms a eutectic mixture in the furnace, which aggravates the coking of the furnace wall and the corrosion of the refractory material.

[0003] The core challenge of the chemical waste liquid disposal system comes from the extreme complexity of the waste liquid composition, which not only reflects the coexistence of multiple substances, but also the violent reactions that can occur between different substances. When the alkyl ketone residual liquid, acidic hydrogen peroxide concentrate and methylamine alkaline waste liquid discharged by the device flow into the temporary storage tank, the acid-base neutralization reaction will start spontaneously without human intervention - this process is like installing an out-of-control chemical engine inside a closed container, and a large amount of heat accumulates rapidly. The high-temperature environment will further promote the crystallization of sodium salt and potassium salt in the waste liquid, and the needle-shaped sodium sulfate crystals will grow along the pipe wall, gradually forming a dense blockage. Operators frequently face alerts of abnormal stoppage of feed pumps and have to interrupt the incineration process to open the high-pressure water gun to forcibly unblock the pipeline. Even so, there are still fine salt particles that break through the filtration system and enter the incinerator.

[0004] The mixed heat value of the waste liquid itself also causes control difficulties for the incineration system. For example, polyol rectification residual liquid can release heat energy equivalent to that of fine coal, while catalyst washing water is close to non-combustible liquid. If the two types of waste liquid are not balanced, the incineration temperature will fluctuate dramatically. Operators often face ECG-like changes in the temperature curve of the combustion zone on the instrument panel. When the furnace temperature suddenly drops to 800℃, the incomplete pyrolysis of chlorine-containing organic matter will generate toxic dioxins; when the temperature rises sharply above 1200℃, the molten salt behaves like magma and wraps the refractory material - the surface of the refractory brick is constantly generating holes and cracks under the dual action of high temperature and salt corrosion, and the originally designed three-year furnace lining is often eroded and penetrated within a few months, and maintenance personnel can always disassemble the brick from the furnace body. The stability of the coke-like brick is out of control, which puts both safe operation and environmental emission at risk. SUMMARY

[0005] The present application realizes line simplification, less occupied space, multi-stage utilization of heat energy and controlled incineration process, and waste liquid with different acid and alkaline properties can be incinerated accordingly. An acid-base waste liquid treatment system is provided, comprising a incinerator, an electric dust removal device and a bag dust removal device which are sequentially communicated in the flue gas direction, an induced draft fan is arranged at the outlet pipe of the bag dust removal device to guide the flue gas to the chimney, a low-temperature denitration catalyst unit is fixedly arranged in the internal air duct of the induced draft fan, the catalyst unit is arranged vertically to the flue gas flow direction, and the induced draft fan is configured to simultaneously realize the flue gas conveying function and the catalytic reaction function; a denitration device is arranged between the bag dust removal device and the induced draft fan, the gas inlet of the denitration device is sealingly connected with the outlet pipe of the bag dust removal device, and the gas outlet is sealingly connected with the gas inlet of the induced draft fan.

[0006] As a preferred solution, a desulfurization tower is arranged between the induced draft fan and the chimney to eliminate sulfur dioxide in the flue gas, the gas inlet end of the desulfurization tower is connected with the outlet pipe of the induced draft fan through a flange, and the gas outlet end is connected with the chimney through an expansion joint.

[0007] As a preferred solution, a coal economizer is arranged between the incinerator and the electric dust removal device for heat exchange, the shell inlet of the coal economizer is communicated with the flue gas outlet of the incinerator, and the shell outlet is communicated with the inlet of the electric dust removal device.

[0008] As a preferred solution, an air preheater is arranged at the flue gas outlet of the incinerator, the inlet pipe of the air preheater is communicated with the air blower, and the outlet pipe is communicated with the incinerator.

[0009] As a preferred solution, a tertiary air pipe is arranged to communicate with a tertiary air blower, a slag cooler is arranged at the bottom of the incinerator, the slag outlet at the bottom of the incinerator is connected with the feed hopper of the slag cooler, and the slag discharge outlet of the slag cooler is arranged obliquely downward.

[0010] As a preferred solution, a scraper is arranged below the slag discharge outlet of the slag cooler, at the bottom of the ash hopper of the electric dust removal device and at the bottom of the ash hopper of the bag dust removal device, and the conveying directions of the scrapers are directed to the same ash collecting bin.

[0011] As a preferred solution, a cyclone is arranged at the flue gas outlet of the incinerator, the tangential gas inlet of the cyclone is fixedly welded with the flue gas outlet of the incinerator, and the axial gas outlet is communicated with the downstream flue.

[0012] As a preferred solution, a steam drum is arranged at the top of the incinerator, and the steam drum forms a closed circulation loop with the water-cooled wall pipe screen of the incinerator through a downcomer and an upcomer.

[0013] An acid-base waste liquid treatment process comprises the following steps: incinerated waste liquid is divided into acidic waste liquid and alkaline waste liquid according to the pH value, the mixing ratio of the acidic liquid and the alkaline liquid in the waste liquid added to the incinerator is controlled to be 1:3 to 1:5, the PH value of the mixed waste liquid entering the furnace is controlled to be between 5 and 9, and the middle part temperature of the hearth of the incinerator is controlled to be 650±30℃. When the incinerator hearth temperature drops, increase the acidic wastewater, reduce the fuel gas main pipe pressure, increase the desulfurization tower gas ammonia addition amount, control the PH value of the absorption liquid between 5.5 and 7.5; when the hearth temperature rises, adjust the fuel gas adjusting valve, reduce the fuel gas amount, and keep the incinerator external transmission data consistent with the design value.

[0014] The application has the advantages that: The application embeds a low-temperature denitration catalyst unit in the induced draft fan, when the flue gas passes through the high-speed rotating impeller, strong turbulence is generated, which forces the gas to fully contact and react with the surface of the catalyst. This integrated structure combines the traditional independent denitration device and the power equipment, which simplifies the system pipeline and reduces the occupied space. The temperature window required for the catalytic reaction is naturally maintained by the 35-55℃ temperature rise generated by the fan operation, without the need for an external heat source, which significantly reduces the operating energy consumption.

[0015] In the process control aspect, the application forms an intrinsically safe mechanism by accurately blending the acidic wastewater and the alkaline waste liquid. After the proportionally mixed waste liquid is fed into the furnace, in-situ acid-base neutralization reaction occurs in the medium-temperature incineration zone, which greatly reduces the high-temperature corrosion of chlorine ions to the furnace body. The heavy metal components generated in the incineration process are converted into stable oxides at a controllable temperature, and after being discharged with the slag, they are quickly cooled and solidified by the slag cooler, effectively blocking the dioxin synthesis path.

[0016] The application adopts a three-stage coupling design, high-temperature flue gas first separates large particle ash through a cyclone, then combusts air is heated through an air preheater, and finally enters a coal economizer to heat boiler feed water. The waste heat is utilized in stages, making the comprehensive heat recovery efficiency break through 75%, and the water-cooled wall tube panel and the steam drum form a steam self-circulation system, which basically meets the device's own steam demand. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to make the content of the application easier to be clearly understood, the application will be further described in detail below according to specific embodiments and in conjunction with the drawings, in which Figure 1 The figure is a structural schematic diagram of the application.

[0018] In the drawings, the reference signs are: 1. incinerator; 2. electric dust removal device; 3. bag dust removal device; 4. induced draft fan; 5. chimney; 6. denitration device; 7. desulfurization tower; 8. coal economizer; 9. air preheater; 10. air supply fan; 11. tertiary air fan; 12. slag cooler; 13. scraper; 14. cyclone; 15. steam drum. DETAILED DESCRIPTION

[0019] In order to illustrate the characteristics of the application, the application will be further described below in conjunction with the drawings and examples.

[0020] Example 1: Please refer to Figure 1 The embodiment provides an acid-base waste liquid collaborative treatment system integrating catalysis and waste heat recovery. A double-channel incinerator 1 is used to treat PH3 acidic waste liquid and PH12 alkaline waste liquid. Proportional control valves are used to control the mixing of the acidic liquid and the alkaline liquid at a ratio of 1:4, so that the PH of the waste liquid entering the incinerator is stabilized between 5 and 9. A K-type thermocouple is arranged in the middle of the furnace to monitor the temperature and maintain 650±10℃. A steam drum 15 is connected to the water-cooled wall of the furnace through a Φ219×8mm downpipe to form a closed loop steam-water circulation. The incineration flue gas is tangentially separated from large particle ash by a cyclone 14 at the outlet, and then enters the shell side of a horizontal economizer 8 to exchange heat with the counter-flow desalted water, so that the flue gas is cooled to 280℃ and the desalted water is heated to 105℃. After heat exchange, the flue gas tangentially enters the 400mm electrode plate spacing electric field area of the electric dust removal device 2.

[0021] The flue gas after electric dust removal then enters the long-bag low-pressure pulse cloth bag dust removal device 3 to capture dust with a particle size of >0.5μm. The dust removal flue gas is mixed with 5% concentration ammonia gas sprayed by the ammonia grid in the denitration device 6, and then enters the specially designed induced draft fan 4: the fan impeller diameter is 2.4m, and the honeycomb low-temperature denitration catalyst with a hole density of 300cpsi is embedded between the blades to complete the catalytic reduction reaction under the working condition of 240±5℃. After denitration, the flue gas is connected by flanges into the desulfurization tower 7. Three layers of spray layers in the tower spray PH7.0 limestone slurry at a flow rate of 12m³ / h to eliminate SO2. After expansion joint, the flue gas is discharged through an 80m high chimney 5, and the SO2 content of the outlet flue gas is ≤35mg / Nm³.

[0022] The Φ1.2m slag cooler 12 at the bottom of the incinerator processes 650℃ hot slag at a speed of 3r / min, and the three-stage air pipe of the furnace passes in 800℃ hot air at a wind speed of 15m / s to strengthen combustion. The solid waste treatment system is equipped with three BW800 type scraper conveyors 13: the scraper conveyor below the slag discharge port of the slag cooler horizontally conveys large slag, the scraper conveyors of the electric dust removal ash hopper and the cloth bag dust removal ash hopper convey fly ash at an inclination angle of 30°, and the three routes of ash and slag finally converge into the underground ash collection bin for chelation and solidification.

[0023] In this embodiment, the low-temperature denitration catalyst unit is embedded in the induced draft fan. When the flue gas passes through the high-speed rotating impeller, strong turbulence is generated, forcing the gas to fully contact and react with the surface of the catalyst. This integrated structure combines the traditional independent denitration device and the power equipment into one, which simplifies the system pipeline and reduces the occupied space. The temperature window required for catalytic reaction is naturally maintained by the 35-55℃ temperature rise generated by the fan operation, without the need for external heat source, which significantly reduces the operating energy consumption.

[0024] In addition, the embodiment adopts a three-stage coupling design, high-temperature flue gas is first separated from large particle ash by a cyclone, then combustion air is heated by an air preheater, and finally boiler feed water is heated by a coal economizer. The step-by-step utilization of waste heat breaks through the comprehensive recovery efficiency of thermal energy of 75%, and the water-cooled wall tube panel and the steam drum form a steam self-circulation system, which basically meets the steam demand of the device itself.

[0025] Embodiment 2: The embodiment proposes an acid-base waste liquid treatment process based on the device of embodiment 1, including the following steps: the incinerated waste liquid is divided into acidic waste water and alkaline waste water according to the pH value, the mixing ratio of the acidic liquid and the alkaline liquid in the waste liquid added to the incinerator is controlled to be 1:3 to 1:5, so that the pH value of the mixed waste liquid entering the furnace is between 5 and 9, and the temperature in the middle part of the furnace of the incinerator is controlled to be 650±30℃; When the temperature of the incinerator drops, increase the acidic waste water, reduce the pressure of the gas main pipe, increase the amount of ammonia added to the desulfurization tower, and control the pH value of the absorption liquid to be between 5.5 and 7.5; when the temperature of the furnace rises, adjust the gas regulating valve, reduce the amount of gas, and keep the external transmission data of the incinerator consistent with the design value.

[0026] The embodiment forms an intrinsically safe mechanism by precisely adjusting the acidic waste water and the alkaline waste liquid. After the mixed waste liquid enters the furnace, in-situ acid-base neutralization reaction occurs in the medium-temperature incineration zone, which greatly reduces the high-temperature corrosion of chloride ions on the furnace body. The heavy metal components generated during the incineration process are converted into stable oxides at a controllable temperature, and are quickly cooled and solidified by the slag cooler after being discharged with the slag, effectively blocking the dioxin synthesis path.

[0027] The above embodiments and drawings are only used to illustrate the technical solutions of the present application, and are not limited to the present application. The preferred embodiments of the present application are described in detail, and those skilled in the art should understand that the changes, modifications, additions or replacements made by those skilled in the art within the essential scope of the present application do not deviate from the purpose of the present application, and should also belong to the protection scope of the claims of the present application. Other related technical structures not disclosed in detail in the present application are the existing technologies in the art.

Claims

1. A system for treating acid and alkali waste liquid, comprising an incinerator (1), an electrostatic precipitator (2), and a bag dust removal device (3) connected in sequence along the direction of flue gas, wherein an induced draft fan (4) is provided at the outlet pipe of the bag dust removal device (3) to guide the flue gas to a chimney (5), characterized in that: A low-temperature denitration catalyst unit is fixedly arranged in the internal air duct of the induced draft fan (4), and the catalyst unit is arranged perpendicular to the flow direction of the flue gas. The induced draft fan (4) is configured to simultaneously realize the flue gas transportation function and the catalytic reaction function; a denitration device (6) is arranged between the bag dust removal device (3) and the induced draft fan (4), and the air inlet of the denitration device (6) is sealedly connected to the outlet pipe of the bag dust removal device (3), and the air outlet is sealedly connected to the air inlet of the induced draft fan (4).

2. The acid and alkali waste liquid treatment system according to claim 1, characterized in that: A desulfurization tower (7) is provided between the induced draft fan (4) and the chimney (5) to eliminate sulfur dioxide in the flue gas. The air inlet end of the desulfurization tower (7) is connected to the outlet pipe of the induced draft fan (4) through a flange, and the air outlet end is connected to the chimney (5) through an expansion joint.

3. The acid and alkali waste liquid treatment system according to claim 2, characterized in that: An economizer (8) is provided between the incinerator (1) and the electrostatic precipitator (2) for heat exchange, the shell side inlet of the economizer (8) is connected to the smoke outlet of the incinerator (1), and the shell side outlet is connected to the inlet of the electrostatic precipitator (2).

4. The acid and alkali waste liquid treatment system according to claim 2, characterized in that: An air preheater (9) is provided at the smoke outlet of the incinerator (1); an inlet pipe of the air preheater (9) is connected to a blower (10), and an outlet pipe is connected to the incinerator (1).

5. The acid and alkali waste liquid treatment system according to claim 1, characterized in that: The incinerator (1) is provided with a tertiary air duct connected to a tertiary fan (11), a slag cooler (12) is provided at the bottom of the incinerator (1), a slag outlet at the bottom of the incinerator (1) is connected to a feed hopper of the slag cooler (12), and a slag outlet of the slag cooler (12) is arranged tilted downward.

6. The acid and alkali waste liquid treatment system according to claim 1, characterized in that: Scrapers (13) are provided below the slag discharge port of the slag cooler (12), at the bottom of the ash hopper of the electrostatic precipitator (2), and at the bottom of the ash hopper of the bag dust removal device (3), and the conveying direction of each scraper (13) points to the same ash collection bin.

7. The acid and alkali waste liquid treatment system according to claim 1, characterized in that: A cyclone (14) is provided at the smoke outlet of the incinerator (1); the tangential air inlet of the cyclone (14) is welded and fixed to the smoke outlet of the incinerator (1); and the axial air outlet is communicated with the downstream flue.

8. The acid and alkali waste liquid treatment system according to claim 1, characterized in that: A steam drum (15) is provided on the top of the incinerator (1), and the steam drum (15) forms a closed circulation loop with the water-cooled wall tube panel of the incinerator (1) through the downcomer and the upcomer.

9. A process for treating acid and alkali waste liquid, characterized in that: The following steps are involved: The incinerated wastewater is divided into acidic wastewater and alkaline wastewater according to the pH value. The mixing ratio of the acidic liquid and the alkaline liquid added to the wastewater in the incinerator is controlled to be 1:3 to 1:5, so that the pH value of the mixed wastewater entering the furnace is between 5 and 9. The temperature in the middle of the incinerator furnace is controlled to 650±30℃; When the incinerator temperature drops, add acidic wastewater, reduce the gas main pressure, increase the amount of ammonia added to the desulfurization tower gas, and control the pH value of the absorption liquid between 5.5 and 7.5; when the furnace temperature rises, adjust the gas regulating valve, reduce the gas volume, and keep the incinerator's external transmission data in line with the design value.

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