Method and device for purifying sulfur dioxide pollution in lost foam casting waste gas

Abstract

The present invention discloses a method and device for purifying sulfur dioxide pollution in lost foam casting waste gas. The method comprises: first oxidizing lost foam casting waste gas containing SO2 into a high-temperature SO3 gas flow in a high-temperature, high-force flow environment at a temperature of not less than 800°C; the flowing high-temperature SO3 gas flow passes through a pipe in a water mist absorption section to generate misted dilute sulfuric acid; the misted dilute sulfuric acid, driven by the air flow, enters a pipe in a cooling section for cooling; the cooled misted dilute sulfuric acid is deposited in a liquid state and enters a recovery tank; and the lost foam casting waste gas containing SO2 is purified. The present invention breaks the theoretical and current situation that SO3 is not suitable for water absorption, overcomes technical prejudice, and uses air flow to prevent acid mist from lingering during the absorption process and hindering subsequent reactions. The method also has a high absorption rate and a fast absorption rate. It not only purifies SO2 but also recovers dilute sulfuric acid for comprehensive utilization, achieving the dual purification effect of purifying benzene and sulfur dioxide. The device is low-cost, simple to operate, safe and reliable.

Description

Technical Field

[0001] The present invention relates to the field of SO2 purification in lost foam casting waste gas, and in particular to a method and device for purifying sulfur dioxide pollution in lost foam casting waste gas. Background Art

[0002] The waste gas from lost foam casting is a mixture of benzene, SO2, CO2 and other components, which is discharged from the exhaust pipe of the vacuum pump. Among them, benzene is insoluble in water, while the reaction of SO2 with water is reversible (SO2+H2O H2SO3), so using water to absorb SO2 is impractical and unfeasible. Oxidizing SO2 to SO3 and then absorbing it with water to produce sulfuric acid is an exothermic reaction. Due to the high temperature, the sulfuric acid forms a thick mist that stagnates in the absorption tower, hindering the reaction and significantly reducing the absorption rate and speed. Therefore, industrial production both domestically and internationally does not use water to absorb SO3, but instead uses 98% concentrated sulfuric acid. This method is both unrealistic and unsafe for the more than 5,000 and growing number of lost foam casting factories nationwide. Summary of the Invention

[0003] In response to the above situation, the present invention provides a method and device for purifying sulfur dioxide pollution in lost foam casting waste gas. This method has a high absorption rate and a fast absorption speed. It can not only purify SO2, but also recover dilute sulfuric acid for comprehensive utilization. The device is low in cost, simple and easy to operate, safe and reliable.

[0004] The technical solution for achieving the purpose of the present invention is:

[0005] A method for purifying sulfur dioxide pollution in lost foam casting waste gas comprises the following steps:

[0006] 1) First, the lost foam waste gas containing SO2 is oxidized into high-temperature SO3 gas flow in a high-temperature oxygen-rich and strong flow environment with a temperature not lower than 800℃;

[0007] 2) The flowing high-temperature SO3 gas flows through the pipes of the water mist absorption section to generate mist-like dilute sulfuric acid;

[0008] 3) The misted dilute sulfuric acid enters the cooling section pipeline under the push of airflow for cooling;

[0009] 4) The cooled mist-like dilute sulfuric acid is deposited in liquid form and enters the recovery pool;

[0010] The lost foam casting waste gas containing SO2 is purified.

[0011] Preferably, in step 1), SO2 in the exhaust gas is oxidized into SO3 in the combustion chamber of the oxygen-enriched enhanced burner of the high-temperature oxygen-enriched supernormal pressure enhanced combustion purification device.

[0012] Preferably, in step 2), the length of the pipe of the water mist absorption section is 3 to 5 m, and the inner diameter is Ø200-400 mm.

[0013] Preferably, in step 3), the pipe length of the cooling section is 20-30 m, and the inner diameter is Ø200-400 mm.

[0014] A device for purifying sulfur dioxide pollution in lost foam casting exhaust gas to implement the above method includes a high-temperature oxygen-rich supernormal pressure enhanced combustion purification device, a water mist absorption section, a cooling section, a recovery tank and a purification discharge port. The combustion chamber of the high-temperature oxygen-rich supernormal pressure enhanced combustion purification device, the water mist absorption section, and the cooling section are connected in sequence, and the outlet end of the cooling section is connected to the recovery tank and the purification discharge port.

[0015] Preferably, the high-temperature oxygen-enriched supernormal pressure enhanced combustion purification device adopts the high-temperature oxygen-enriched supernormal pressure enhanced combustion purification device disclosed in the authorization announcement number "CN109780563B" and named "High-temperature oxygen-enriched supernormal pressure enhanced combustion purification method for benzene-like harmful substances in industrial waste gas".

[0016] The exhaust gas collection and suction system of the high-temperature oxygen-rich supernormal pressure enhanced combustion purification device is connected to the vacuum pump exhaust pipe of the lost foam casting exhaust gas release source, so that the lost foam casting exhaust gas enters the combustion (oxidation) chamber of the oxygen-rich enhanced burner of the high-temperature oxygen-rich supernormal pressure enhanced combustion purification device.

[0017] Preferably, the pipe length of the water mist absorption section is 3 to 5 meters, and the inner diameter is Φ200-400 mm.

[0018] Preferably, the pipe length of the cooling section is 20-30 m, and the inner diameter is Ø200-400 mm.

[0019] The waste gas generated by the pyrolysis of EPS (Expanded polystyrene) in the casting mold is discharged through the vacuum pump exhaust pipe at a speed of 20 to 50 m 3 / min flow rate is powerfully ejected. The inner diameter of the vacuum pump exhaust pipe used by all lost foam casting plants in China is mostly 140-160mm. The exhaust gas is forcefully input into the combustion chamber of the high-temperature, oxygen-enriched, supernormal-pressure enhanced combustion purification device. Combustible substances such as benzene in the exhaust gas are converted into H2O and CO2, while SO2 is oxidized to form SO3. It then enters the pipe of the water mist absorption section with the high-temperature and high-pressure airflow, forming a mixed gas of dilute sulfuric acid mist and water mist that continues to flow forward and cannot remain in the pipe of the water mist absorption section. This promotes the efficient and rapid absorption of SO3 by the water mist in the water mist absorption section and continuously flows forward along the pipe of the cooling section. The dilute sulfuric acid mist is cooled and deposited in the recovery pool for recovery. The exhaust gas is purified and discharged from the purification outlet.

[0020] The present invention is a method for converting SO2 into SO3 and then absorbing it with flowing water mist to generate sulfuric acid for recycling. The method utilizes the characteristic that SO2 is easily oxidized into SO3 under high temperature and oxygen-rich conditions, and then uses a strong flowing water vapor flow to efficiently absorb SO3 to generate dilute sulfuric acid, which is then recycled or neutralized and purified for discharge, so that SO2-SO3 It can be purified efficiently. Under the action of strong airflow, even the most concentrated sulfuric acid mist will be taken away with it, so that the reaction of H2O+SO3→H2SO4 will not be affected in the water mist absorption section. The reaction section of the water mist absorption section completely eliminates the retention of acid mist, and the absorption reaction rate is very fast. The mist acid will be deposited as dilute sulfuric acid and recovered in the process of flowing with the airflow to the recovery pool and the purification discharge port in the direction of the discharge pipeline, so that purification and recovery can be achieved at one stroke; the temperature of SO3 flowing strongly from the combustion chamber to the water mist absorption section is often above 400℃. When the water mist is sprayed into this high-temperature section of the pipeline, it will be gasified at a very fast speed, which not only absorbs SO3 efficiently, but also quickly reduces the temperature of the air flow in the pipe to about 100℃, so it can be discharged quickly and greatly save water.

[0021] Advantages of the present invention:

[0022] 1. It breaks the theory and status quo that SO3 is not suitable for water absorption and overcomes technical prejudice. The air flow movement can completely avoid the phenomenon of acid mist staying in the absorption process and hindering subsequent reactions, and has a high absorption rate and fast absorption speed;

[0023] 2. It can not only purify SO2, but also recycle dilute sulfuric acid for comprehensive utilization;

[0024] 3. The high-temperature, oxygen-enriched, ultranormal-pressure enhanced combustion purification device described in the "High-Temperature, Oxygen-Enriched, Ultranormal-Pressure Enhanced Combustion Purification Method for Benzene-Related Harmful Substances in Industrial Waste Gases" (authorized publication number CN109780563B) for purifying benzene-related combustible waste gas achieves dual purification effects for benzene and sulfur dioxide. Lost foam casting waste gas is a mixture of various benzene-related aromatic hydrocarbons, sulfur dioxide, and other harmful substances. The "integrated" purification process for benzene and sulfur dioxide in the same process is unprecedented domestically and internationally, making it a novel approach.

[0025] 4. The device has low cost, is simple and easy to operate, safe and reliable, and can be used in all lost foam casting plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the structure of the device for purifying sulfur dioxide pollution in lost foam casting waste gas in an embodiment of the present invention.

[0027] In the figure, 1. Water mist absorption section 2. Cooling section 3. Recovery pool 4. Discharge port 5. Water source 6. Vacuum pump exhaust pipe 7. Combustion chamber 8. Oxygen source.

[0028] The arrows in the figure indicate the flow direction. DETAILED DESCRIPTION

[0029] The present invention is further described below with reference to the embodiments and accompanying drawings. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0030] Example:

[0031] A method for purifying sulfur dioxide pollution in lost foam casting waste gas comprises the following steps:

[0032] 1) First, the lost foam waste gas containing SO2 is oxidized into high-temperature SO3 gas flow in a high-temperature oxygen-rich and strong flow environment with a temperature not lower than 800℃;

[0033] 2) The flowing high-temperature SO3 gas flows through the pipes of the water mist absorption section to generate mist-like dilute sulfuric acid;

[0034] 3) The misted dilute sulfuric acid enters the cooling section pipeline under the push of airflow for cooling;

[0035] 4) The cooled mist-like dilute sulfuric acid is deposited in liquid form and enters the recovery pool;

[0036] The lost foam casting waste gas containing SO2 is purified.

[0037] Furthermore, in step 1), SO2 in the exhaust gas is oxidized into SO3 in the combustion chamber of the oxygen-enriched enhanced burner of the high-temperature oxygen-enriched supernormal pressure enhanced combustion purification device; in step 1), the temperature of the combustion chamber of the high-temperature oxygen-enriched supernormal pressure enhanced combustion purification device is greater than 1300°C.

[0038] Furthermore, in step 2), the length of the pipe of the water mist absorption section is 4m and the inner diameter is Ф300mm; in step 2), the temperature of the flowing high-temperature SO3 gas flow discharged from the combustion chamber above 1300°C of the high-temperature oxygen-enriched supernormal pressure enhanced combustion purification device is above 400°C.

[0039] Furthermore, in step 3), the pipe length of the cooling section is 25 m and the inner diameter is Ø300 mm.

[0040] like Figure 1As shown, a device for purifying sulfur dioxide pollution in lost foam casting exhaust gas by implementing the above method includes a high-temperature oxygen-rich supernormal pressure enhanced combustion purification device, a water mist absorption section 1, a cooling section 2 and a recovery pool 3. The combustion chamber 7 of the high-temperature oxygen-rich supernormal pressure enhanced combustion purification device, the water mist absorption section 1, and the cooling section 2 are connected in sequence, and the outlet end of the cooling section 2 is connected to the recovery pool 3 and the purification discharge port 4.

[0041] The high-temperature oxygen-enriched supernormal pressure enhanced combustion purification device adopts the high-temperature oxygen-enriched supernormal pressure enhanced combustion purification device in the method for high-temperature oxygen-enriched supernormal pressure enhanced combustion purification of benzene-type harmful substances in industrial waste gas disclosed in the authorization announcement number CN109780563B, with reference to the specification and drawings disclosed in CN109780563B.

[0042] The exhaust gas collection and suction system of the high-temperature oxygen-rich supernormal pressure enhanced combustion purification device is connected to the vacuum pump exhaust pipe 6 of the lost foam casting exhaust gas release source, and an oxygen source 8 is provided to be connected to the vacuum pump exhaust pipe 6 so that the lost foam casting exhaust gas enters the combustion chamber 7 of the oxygen-rich enhanced burner of the high-temperature oxygen-rich supernormal pressure enhanced combustion purification device.

[0043] The lost foam casting exhaust gas enters the combustion chamber 7 of the high-temperature oxygen-rich supernormal pressure enhanced combustion purification device, where SO2 is oxidized into SO3 in an environment of high temperature, oxygen-rich and supernormal pressure of not less than 800°C.

[0044] Furthermore, the pipe length of the water mist absorption section 1 is 4 meters and the inner diameter is Ø300 mm. A water mist nozzle connected to the water source 5 is provided in the water mist absorption section 1, so that the inner cavity of the water mist absorption section 1 is filled with water mist. The high-temperature SO3 flowing in step 1) evaporates the water mist into water vapor, and the high-temperature SO3 is efficiently absorbed in the strong flow of water vapor to generate mist-like dilute sulfuric acid.

[0045] Furthermore, the pipe length of the cooling section 2 is 25m and the inner diameter is Φ300mm.

[0046] The water vapor flow flows in the direction of organized emission in the water mist absorption section 1, completely eliminating the retention of acid mist in the water mist absorption section 1, and the absorption reaction rate is very fast.

[0047] The temperature of SO3 flowing forcefully from the combustion chamber 7 of the oxygen-enriched enhanced burner to the water mist absorption section 1 is usually above 300°C. When the water mist is sprayed into this high-temperature pipe section, it vaporizes at an extremely fast rate, effectively absorbing SO3 and rapidly reducing the temperature of the air flow in the pipe to around 100°C. This is because the heat absorbed by 1kg of room-temperature water turning into water vapor is equivalent to more than 5 times the heat required to heat 1kg of water from room temperature to 100°C. Therefore, it can quickly cool down and discharge, and save 5 times the amount of cooling water.

[0048] Experimental data and results:

[0049] The sulfur dioxide emission concentration of the present invention is tested to be in compliance with the national environmental protection limit standard.

[0050] The following are the measured data:

[0051] Testing time: 2019.11.21;

[0052] Monitoring unit: Guangxi Guilin Jingui Environmental Monitoring Co., Ltd., a nationally qualified professional environmental monitoring agency, issues Monitoring report of metrological certification mark;

[0053] Inspected unit: Guilin Zhongzhu Machinery Technology Co., Ltd. (lost foam casting workshop).

[0054] Monitoring results:

[0055] 1. The concentration of SO2 sampled from the vacuum pump exhaust pipe 6 is 3.33×10 3 mg / m 3 ;

[0056] 2. After purification, the concentration of the sample taken from the discharge pipe in the discharge port 4 is ND;

[0057] 3. According to national environmental protection regulations, the detection limit is 3mg / m 3 , the purification effect is at the international advanced level.

[0058] The above data is based on actual measurements with a combustion chamber temperature above 1300°C. Experiments have confirmed that a combustion chamber temperature of no less than 700°C effectively reduces sulfur dioxide emissions in exhaust gas. At a combustion chamber temperature of no less than 800°C, sulfur dioxide emission concentrations meet national environmental protection limits. At a combustion chamber temperature of no less than 1000°C, sulfur dioxide emission concentrations are significantly lower than national environmental protection limits.

[0059] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A device for purifying sulfur dioxide pollution in lost foam casting waste gas, characterized in that: It includes a high-temperature oxygen-enriched supernormal pressure enhanced combustion purification device, a water mist absorption section, a cooling section, a recovery pool and a purification discharge port. The combustion chamber of the high-temperature oxygen-enriched supernormal pressure enhanced combustion purification device, the water mist absorption section and the cooling section are connected in sequence. The outlet end of the cooling section is connected to the recovery pool and the purification discharge port. The water mist absorbing section is provided with a water mist nozzle connected to a water source; The pipe length of the water mist absorption section is 3 to 5 meters, and the inner diameter is Ф200-400mm; The cooling section has a pipe length of 20 to 30 m and an inner diameter of Ø200 to 400 mm; The method for purifying sulfur dioxide pollution in lost foam casting waste gas comprises the following steps: First, the SO2-containing lost foam waste gas is oxidized into a high-temperature SO3 gas flow in a high-temperature oxygen-rich and strong flow environment at a temperature not lower than 1300°C; The flowing high-temperature SO3 gas flows through the pipes of the water mist absorption section to generate mist-like dilute sulfuric acid; The mist of dilute sulfuric acid is driven by airflow into the pipes of the cooling section for cooling; The cooled mist-like dilute sulfuric acid is deposited in liquid form into the recovery pool; The lost foam casting waste gas containing SO2 is purified.

2. The device for purifying sulfur dioxide pollution in lost foam casting waste gas according to claim 1, characterized in that: The pipe length of the water mist absorption section is 4m and the inner diameter is Ф300mm.

3. The device for purifying sulfur dioxide pollution in lost foam casting waste gas according to claim 1, characterized in that: The pipe length of the cooling section is 25m and the inner diameter is Φ300mm.

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