Method for treating exhaust gases from the production of vae emulsions

Abstract

The present application aims to provide a VAE emulsion production waste gas treatment method, which realizes a new safe, economic and reliable organic waste gas treatment process; in order to achieve the above-mentioned purpose, the solving method of the present application is to provide a VAE emulsion production waste gas treatment method, waste gas from different waste gas sources is collected in the pressure equalization water seal tank and then enters the gas cabinet, and by reasonably determining the working pressure of the gas cabinet, the waste gas from the gas cabinet directly enters the TO furnace, the waste gas from the TO furnace is cooled by the waste heat recovery boiler system and by-product superheated steam is produced, the cooled waste gas is denitrated by the denitrating device, and the denitrated waste gas is further cooled by the heat recovery device and then introduced into the chimney for external discharge.

Description

Technical Field

[0001] This invention relates to the field of waste gas treatment, and more particularly to a method for treating waste gas from VAE emulsion production. Background Technology

[0002] VAE emulsion is a copolymer of vinyl acetate and ethylene, possessing excellent adhesion, flexibility, weather resistance, acid and alkali resistance, and film-forming properties. Since its introduction to the market, VAE emulsion has undergone nearly half a century of development. International research on high-solids-content, low-viscosity, and environmentally friendly VAE emulsions has been extensive and in-depth, resulting in the development of many new varieties. However, the scale and variety of VAE emulsion production in China lag significantly behind that of foreign countries.

[0003] However, the demand for VAE emulsions in my country is growing rapidly. In particular, with the increasing environmental awareness and improved application technologies in recent years, the application of VAE emulsions in some emerging industrial fields is constantly expanding. The extensive use of VAE emulsions in building waterproofing is a major characteristic of the Chinese VAE emulsion industry, as it is rarely used in waterproof coatings globally. Domestically, leading waterproofing company Oriental Yuhong utilizes the water resistance, alkali resistance, aging resistance, foaming resistance, softness, and elasticity of VAE emulsion-formed paint films, widely applying them in the preparation of various building waterproof coatings, such as interior and exterior wall coatings, roof waterproof coatings, bathroom waterproof coatings, fireproof coatings, and rust-preventive coatings. VAE emulsion coatings can be applied to concrete, mortar, brick, asbestos, gypsum, wood, etc., and can also be used to prepare matte and thick-film coatings.

[0004] Currently, the waterproofing industry primarily purchases VAE emulsions from foreign-invested enterprises that bring their technology to China to establish factories. As waterproofing companies increase their coating production capacity, the demand for VAE emulsions continues to rise, gradually becoming a bottleneck in their coating production. Therefore, waterproofing companies are looking to the future, developing their own VAE emulsion production technologies, and embarking on the construction of VAE emulsion factories. This invention presents a safe, economical, and reliable new process for treating production waste gas during the development of VAE emulsion production technology.

[0005] Therefore, providing a targeted method for treating waste gas from VAE emulsion production is an urgent technical problem to be solved in the field of waste gas treatment. Summary of the Invention

[0006] The purpose of this invention is to provide a method for treating waste gas from VAE emulsion production, achieving a safe, economical, and reliable new process for treating organic waste gas.

[0007] To achieve the above objectives, the present invention provides a method for treating waste gas from VAE emulsion production. Waste gas from different sources is collected in a pressure equalization water seal tank and then enters a gas holder. By reasonably determining the working pressure of the gas holder, the waste gas exiting the gas holder is directly fed into the TO furnace. The waste gas exiting the TO furnace is cooled by a waste heat recovery boiler system, producing superheated steam as a byproduct. The cooled waste gas is denitrified by a denitrification device. The denitrified waste gas is further cooled by a heat recovery device and then discharged through a chimney. Preferably, the gas holder is a wet direct-lift gas holder. By adjusting the working pressure of the gas holder system, the waste gas exiting the gas holder is directly fed into the TO furnace combustion system, reducing the need for gas conveying equipment between the gas holder and the TO furnace.

[0008] Furthermore, there are several sources of exhaust gas, and the exhaust gas sources include at least one of the following: exhaust gas from the degassing tank, exhaust gas from the ethylene compressor, and exhaust gas from the vinyl acetate storage tank.

[0009] Furthermore, the TO furnace is equipped with a heat storage baffle wall inside, allowing the waste gas to be treated to fully contact the oxygen in the furnace chamber within the heat storage wall, significantly improving the efficiency of waste gas oxidation and decomposition. A portion of the tail-end waste gas is introduced into the front end of the TO furnace to control the furnace temperature at 900-1000℃, preventing NOx generation. Preferably, the front end of the furnace chamber has a feed inlet, and the rear end has an exhaust outlet. The feed inlet is connected to a gas holder. The upper end of the furnace chamber has a first air inlet for introducing oxygen, and the lower end of the furnace chamber has a second air inlet for introducing circulating waste gas to regulate the internal temperature of the furnace chamber. Compared to conventional TO furnaces, this TO furnace lowers the furnace chamber temperature, increases the furnace volume, and increases the residence time of waste gas in the furnace by 20%.

[0010] Furthermore, the TO furnace is equipped with a low-NOx burner to prevent backfire at the feed inlet.

[0011] Furthermore, the pressure equalization water seal tank is equipped with an oxygen content detector. When the oxygen content of the exhaust gas in the pressure equalization water seal tank is greater than 3%, the exhaust gas is prohibited from entering the gas holder. Preferably, depending on the gas pressure of the exhaust gas source, the depth to which the exhaust gas source is inserted below the water surface in the water seal tank varies, with the greater the gas pressure, the greater the depth. Preferably, for the exhaust gas produced by the degassing tank, because its flow rate is large and its flow rate fluctuates greatly, a multi-hole pipe head is designed at the pipe outlet below the water surface to ensure that the exhaust gas enters the pressure equalization water seal tank smoothly.

[0012] Furthermore, the waste heat recovery boiler system includes: a boiler unit, a steam drum, and a superheater. The exhaust gas generated by the TO furnace enters the boiler unit for cooling and then enters the superheater for heat exchange and further cooling. The boiler unit generates steam after heat exchange. The steam drum receives steam from the boiler and the heat recovery unit. The steam in the steam drum enters the superheater for heat exchange and is then discharged. Preferably, the steam generated by the waste heat recovery boiler system is used for VAE emulsion spray drying, and the steam is superheated steam at 1.0 MPaG and 240°C.

[0013] Furthermore, the boiler device is either a fire-tube boiler or a water-tube boiler. When the exhaust gas volume fluctuates greatly, a fire-tube boiler is selected, and when the exhaust gas volume fluctuates little and is relatively stable, a water-tube boiler is selected.

[0014] Furthermore, the exhaust gas discharged from the superheater enters a denitrification device, which is an SCR denitrification system or an SNCR denitrification system.

[0015] Furthermore, the heat recovery device includes an economizer and a deaerator. The exhaust gas discharged from the denitrification device enters the economizer for further cooling and then enters the flue before being discharged. The deaerator receives a portion of the steam from the superheater. Soft water is introduced into the deaerator and heated by steam to remove the oxygen from the soft water, thereby reducing the corrosiveness of the soft water to the economizer. After the soft water is deoxygenated by the deaerator, it enters the economizer for heat exchange and then enters the steam drum.

[0016] Furthermore, a soft water heater or a water cooler is provided between the economizer and the chimney. The soft water heater is used to cool the exhaust gas at the economizer outlet and heat the soft water. If the final exhaust gas temperature is ≤75℃, a soft water heater is selected. If there is no temperature requirement, a soft water heater can be omitted or a water cooler can be used. Preferably, an induced draft fan is provided between the economizer and the chimney.

[0017] Advantages of this invention:

[0018] 1. All organic waste gases generated during normal production are collected in a gas holder and then disposed of in a direct-fired incinerator.

[0019] The (TO furnace) efficiently oxidizes and decomposes all organic waste gas. The heat generated by the oxidation and decomposition of organic waste gas is recovered and utilized through by-product superheated steam. An economizer and soft water heater are set up to fully recover the waste heat. The flue gas after oxidation and decomposition is discharged in a denitrification process to meet the emission standards. The entire process of waste gas collection, treatment, by-product superheated steam, full utilization of waste heat, and compliance with emission standards (environmental impact assessment and energy assessment) is completed.

[0020] 2. A water seal tank is installed at the front end of the gas holder to collect three different types of waste gas with different pressures and compositions, and to eliminate the safety hazard of excessive oxygen content at the front end of the gas holder, thus preventing the generation of large-scale safety hazards.

[0021] 3. The gas holder design pressure is considered based on the gas pressure requirements of the TO furnace. No gas conveying equipment is installed between the gas holder and the TO furnace, which can save operating costs.

[0022] 4. TO Furnace System: A) Install a low-NOx burner to prevent backfire; B) Draw part of the tail flue gas to the TO furnace combustion system and furnace cooling system; C) Appropriately reduce the furnace temperature (compared to conventional TO furnaces), appropriately increase the furnace volume, and increase the residence time of exhaust gas in the furnace by 20%; D) Install a regenerator baffle wall on the rear gas passage of the TO furnace, applying the principle of regenerative combustion furnace (RTO furnace) to the direct combustion furnace (TO furnace).

[0023] 5. Select a fire-tube boiler to recover the waste heat from the VAE emulsion production process and generate 240℃ superheated steam for the production of VAEP rubber powder. Attached Figure Description

[0024] Figure 1 This is a flowchart of a method for treating waste gas from VAE emulsion production provided by the present invention;

[0025] Figure 2 This is a schematic diagram of the TO furnace provided by the present invention; Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0027] like Figure 1 As shown, a method for treating waste gas from VAE emulsion production involves collecting waste gas from different sources in a pressure equalization water seal tank before entering a gas holder. There are three waste gas sources: waste gas from the degassing tank, ethylene compressor purging waste gas, and vinyl acetate storage tank exhaust. By rationally determining the working pressure of the gas holder, the waste gas exiting the gas holder is directly fed into the TO furnace. The waste gas from the TO furnace is cooled by a waste heat recovery boiler system, producing superheated steam as a byproduct. The cooled waste gas undergoes denitrification through a denitrification device, and the denitrified waste gas is further cooled by a heat recovery device before being discharged through a chimney. The gas holder is a wet-type direct-lift gas holder. By adjusting the working pressure of the gas holder system, the waste gas exiting the gas holder is directly fed into the TO furnace combustion system. The pressure of the waste gas discharged from the gas holder is 4000 Pa, reducing the need for gas transport equipment between the gas holder and the TO furnace.

[0028] The equalizing water seal tank is equipped with an oxygen content detector. When the oxygen content of the exhaust gas in the equalizing water seal tank is greater than 3%, the exhaust gas is prohibited from entering the gas holder. Depending on the gas pressure of the exhaust gas source, the depth to which the exhaust gas source is inserted below the water surface in the water seal tank varies, with higher gas pressure resulting in greater depth. For the exhaust gas produced by the degassing tank, due to its large flow rate and significant flow fluctuations, a multi-hole pipe head is designed at the outlet of the pipe below the water surface to ensure a smooth flow of exhaust gas into the equalizing water seal tank. An oxygen content detector is installed on each exhaust gas source pipeline. The oxygen content detector in the equalizing water seal tank is connected to the SIS system to strictly control the oxygen content of the exhaust gas entering the gas holder to be less than 3%, thus preventing the oxygen content of the exhaust gas in the gas holder from reaching the limit for the formation of an explosive gas.

[0029] like Figure 2 As shown, the TO furnace is equipped with a heat storage baffle wall inside. The exhaust gas from the tail end of the TO furnace enters the front end of the TO furnace to control the furnace temperature at 900-1000℃ and prevent NOx generation. The front end of the furnace chamber is equipped with a feed inlet, and the rear end of the furnace chamber is equipped with an exhaust outlet. The feed inlet is connected to the gas holder. The upper end of the furnace chamber is equipped with a first air inlet for introducing oxygen, and the lower end of the furnace chamber is equipped with a second air inlet for introducing circulating exhaust gas to regulate the internal temperature of the furnace chamber. The feed inlet of the TO furnace is equipped with a low-NOx burner to prevent backfire.

[0030] The waste heat recovery boiler system includes a boiler unit, a steam drum, and a superheater. The exhaust gas from the TO furnace enters the boiler unit for cooling and then enters the superheater for further cooling. Steam is generated after heat exchange in the boiler unit. The steam drum receives steam from the boiler and the heat recovery unit. The steam in the steam drum enters the superheater for further heat exchange and is then discharged. The steam generated by the waste heat recovery boiler system is used for VAE emulsion spray drying. The steam is 1.0 MPaG, 240°C superheated steam. 85% of the steam is used for VAE emulsion spray drying, and 15% of the steam enters the deaerator. The boiler is a fire-tube boiler, and the exhaust gas temperature is 350℃. The exhaust gas from the superheater enters the denitrification device, and the exhaust gas temperature from the superheater is 305℃. The denitrification device is an SCR denitrification system. The NOx content of the gas coming out of the TO boiler is about 100mg / m3, which still cannot meet the emission requirements. Therefore, an SCR denitrification system is designed in the 300-350℃ range, with a NOx removal rate of not less than 60%. The SCR denitrification system is connected to the urea pyrolysis system, and the exhaust gas temperature from the denitrification device is 300℃.

[0031] The heat recovery device includes an economizer and a deaerator. The exhaust gas from the denitrification device enters the economizer for further cooling before entering the chimney and being discharged. The deaerator receives a portion of the steam from the superheater. Soft water at 30°C is introduced into the deaerator, and the soft water is heated by steam to remove the oxygen, reducing the corrosiveness of the soft water to the economizer. After deoxygenating the soft water, it enters the economizer for heat exchange and then enters the steam drum. A soft water heater and an induced draft fan are sequentially installed between the economizer and the chimney. The soft water heater is used to cool the exhaust gas at the economizer outlet and heat the soft water. The exhaust gas temperature from the economizer is 150°C, and the exhaust gas temperature from the soft water heater is 75°C.

[0032] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for treating waste gas from VAE emulsion production, characterized in that, Waste gases from different sources are collected in a pressure equalization water seal tank and then enter the gas holder. By reasonably determining the working pressure of the gas holder, the waste gas from the gas holder is directly fed into the TO furnace. The waste gas from the TO furnace is cooled by the waste heat recovery boiler system and superheated steam is produced as a by-product. The cooled waste gas is denitrified by the denitrification device. The denitrified waste gas is further cooled by the heat recovery device and then discharged after being led to the chimney. The TO furnace is equipped with a heat storage baffle wall inside, so that the waste gas to be treated and the oxygen in the furnace can fully contact each other in the heat storage wall, which greatly improves the efficiency of waste gas oxidation and decomposition. The TO furnace introduces some tail waste gas into the front end of the TO furnace to control the furnace temperature at 900-1000℃ and prevent NOx generation. The TO furnace is equipped with a backfire-proof low-NOx burner at the feed inlet; The pressure equalization water seal tank is equipped with an oxygen content detector. When the oxygen content of the exhaust gas in the pressure equalization water seal tank is greater than 3%, the exhaust gas is prohibited from entering the gas holder. The waste heat recovery boiler system includes: boiler unit, steam drum and superheater; The heat recovery device includes an economizer and a deaerator.

2. The method for treating waste gas from VAE emulsion production according to claim 1, characterized in that, There are several sources of exhaust gas, and the exhaust gas sources include at least one of the following: exhaust gas from the degassing tank, exhaust gas from the ethylene compressor, and exhaust gas from the vinyl acetate storage tank.

3. The method for treating waste gas from VAE emulsion production according to claim 2, characterized in that, The exhaust gas generated by the TO furnace enters the boiler unit for cooling and then enters the superheater for further cooling. After heat exchange, the boiler unit generates steam. The steam drum receives steam from the boiler and the heat recovery device. The steam in the steam drum enters the superheater for heat exchange and is then discharged.

4. The method for treating waste gas from VAE emulsion production according to claim 3, characterized in that, The boiler unit is a fire-tube boiler or a water-tube boiler.

5. The method for treating waste gas from VAE emulsion production according to claim 4, characterized in that, The exhaust gas discharged from the superheater enters the denitrification device, which is an SCR denitrification system or an SNCR denitrification system.

6. The method for treating waste gas from VAE emulsion production according to claim 5, characterized in that, The exhaust gas discharged from the denitrification device enters the economizer for further cooling and then enters the flue before being discharged. The deaerator receives a portion of the steam from the superheater. Soft water is introduced into the deaerator, and after the soft water is deoxygenated, it enters the economizer for heat exchange and then enters the steam drum.

7. The method for treating waste gas from VAE emulsion production according to claim 6, characterized in that, A soft water heater or water cooler is provided between the economizer and the chimney. The soft water heater is used to cool the exhaust gas at the economizer outlet and heat the soft water.

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