Device for continuously and circularly adsorbing and desorbing VOCs waste gas in CEC tail gas

Abstract

The utility model relates to the technical field of waste gas treatment, in particular to a device for continuously and circularly adsorbing and desorbing VOCs waste gas in CEC tail gas. The device comprises a condensation separation unit and an adsorption and desorption unit which are sequentially communicated, the condensation separation unit comprises a condenser and a gas-liquid separator which are sequentially communicated through a pipeline; a discharge port of the condenser is connected to an upper feed port of the gas-liquid separator, and an upper gas outlet of the gas-liquid separator is connected to the adsorption and desorption unit; the adsorption and desorption unit comprises a fluidized bed adsorption tower and a desorption tower, and a discharge port in the bottom of the fluidized bed adsorption tower is connected to an adsorbent feed port in the bottom of the desorption tower; an adsorbent discharge port in the top of the desorption tower is connected to an upper feed port of the fluidized bed adsorption tower; and an upper gas outlet of the gas-liquid separator is connected to a gas inlet of the fluidized bed adsorption tower. According to the device disclosed by the utility model, the continuous cycle operation can be realized in the adsorption and desorption processes, the regeneration temperature and pressure of the adsorbent are adjustable and controllable, the adsorption efficiency is high, and the efficient removal of VOCs impurities can be ensured.

Description

Technical Field

[0001] The utility model relates to the technical field of waste gas treatment, in particular to a device for treating VOCs waste gas in CEC tail gas through continuous cycle adsorption and desorption. Background Art

[0002] In the production of hydrogen chloride (HCl) and chlorine (Cl2) from CEC (chloroethylene carbonate) offgas, the gas contains a variety of volatile organic compounds (VOCs) such as chloroform, carbon tetrachloride, pentachloroethane, hexachloroethane, trichloroacetaldehyde, dichloroacetaldehyde, and other halogenated alkanes, as well as trace amounts of water, ferric chloride, CEC, and dichloroethylene carbonate (DCEC). These VOCs impurities result in low product purity, necessitating their separation. Existing processes typically use condensation to remove VOC impurities from CEC offgas by adsorption. A major challenge with this process is that, due to the volatile nature of VOC impurities, simple condensation equipment is unable to remove all of them. Some VOC impurities are carried over into downstream equipment and pipelines, causing serious coking. Therefore, the development of new, energy-efficient and efficient VOC removal processes is urgently needed.

[0003] Adsorption methods offer advantages such as wide applicability, low energy consumption, and minimal operational and management requirements. Existing VOC adsorption methods are primarily categorized into three types based on the type of adsorber: fixed-bed adsorbers, zeolite rotors, and fluidized-bed adsorbers. Fixed-bed adsorbers are mature, but present numerous challenges in practical application. For example, they require at least two towers to be used in rotation, resulting in a large adsorption tower footprint and high equipment investment costs. Furthermore, airflow through fixed-bed adsorbers creates significant resistance, which can increase energy consumption and potentially affect treatment efficiency. Furthermore, fixed-bed adsorbers suffer from long adsorbent regeneration times and difficulty replacing the adsorbent, making them difficult to meet the requirements for continuous treatment of large volumes of VOCs. Zeolite rotors, which utilize zeolite adsorbent material in a honeycomb structure, offer advantages such as low pressure drop and high adsorption and desorption efficiency, and have become widely used. However, zeolite rotors have relatively strict requirements for exhaust gas conditions (composition, temperature, humidity, concentration, etc.). Furthermore, they require stringent sealing requirements, and the modular honeycomb adsorbent material results in relatively high maintenance costs. Zeolite rotors may have certain limitations in their treatment capacity and efficiency due to their design and operating principle. For example, when treating high-volume, low-concentration exhaust gases, multiple rotors may be required in parallel, increasing equipment complexity and footprint. Fluidized bed adsorbers utilize the movement of the airflow to ensure full contact between the adsorbent and pollutant molecules in a fluidized state, thereby improving adsorption efficiency and making them more suitable for treating high-volume, low-concentration pollutants. Furthermore, fluidized bed adsorbers offer advantages such as uniform bed temperature, low pressure drop resistance, rapid mass and heat transfer, and ease of design and scale-up. Utility Model Content

[0004] In view of the problems and shortcomings in the prior art, the purpose of the present invention is to provide a device for continuously cyclically absorbing and desorbing VOCs waste gas in CEC tail gas.

[0005] Based on the above purpose, the present invention adopts the following technical solutions:

[0006] The utility model provides a device for treating VOCs waste gas in CEC tail gas by continuous cycle adsorption and desorption, which comprises a condensation separation unit and an adsorption and desorption unit which are connected in sequence.

[0007] Furthermore, the condensation separation unit includes a condenser and a gas-liquid separator connected in sequence through a pipeline; the discharge port of the condenser is connected to the upper feed port of the gas-liquid separator, and the upper gas outlet of the gas-liquid separator is connected to the adsorption and desorption unit.

[0008] Furthermore, the adsorption and desorption unit includes a fluidized bed adsorption tower and a desorption tower, the discharge port at the bottom of the fluidized bed adsorption tower is connected to the adsorbent feed port at the bottom of the desorption tower, and the top air outlet of the fluidized bed adsorption tower is connected to the subsequent gas purification process; the adsorbent discharge port at the top of the desorption tower is connected to the upper feed port of the fluidized bed adsorption tower; the upper air outlet of the gas-liquid separator is connected to the air inlet of the fluidized bed adsorption tower; and the air outlet at the top of the desorption tower is connected to a vacuum pump.

[0009] Furthermore, an adsorbent discharge buffer tank is provided between the discharge port at the bottom of the fluidized bed adsorption tower and the adsorbent feed port at the bottom of the desorption tower.

[0010] Furthermore, an adsorbent feed buffer tank is provided between the adsorbent discharge port at the top of the desorption tower and the upper feed port of the fluidized bed adsorption tower.

[0011] Furthermore, the fluidized bed adsorption tower is provided with 2 to 10 layers of inclined plates, which are inclined downward by 0 to 45 degrees. Filter holes are evenly distributed on the inclined plates, and the filter hole diameter φ is less than 0.5 mm.

[0012] Furthermore, a filter baffle is provided at the upper end of the fluidized bed adsorption tower; the filter baffle is higher than the adsorbent inlet of the fluidized bed adsorption tower and lower than the gas outlet.

[0013] Furthermore, a demister is provided at the lower end of the fluidized bed adsorption tower, and the demister is higher than the gas inlet of the fluidized bed adsorption tower and lower than the adsorbent discharge port.

[0014] Furthermore, the VOCs discharged from the gas outlet at the top of the desorption tower are transported to the VOCs treatment process through a vacuum pump.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] (1) The utility model device can efficiently remove VOCs and other trace impurities in CEC tail gas, greatly alleviating the coking problem of equipment such as fans. At the same time, the utility model device significantly reduces the organic impurities in the products of hydrochloric acid and sodium hypochlorite, and has low operating energy consumption.

[0017] (2) A demister is also installed at the bottom of the fluidized bed adsorption tower, which can effectively remove tiny droplets entrained in the gas, especially droplets with a diameter of 3-5 μm, with a capture efficiency of 98%-99.8%. This is of great significance for protecting subsequent equipment from liquid corrosion and reducing material loss. At the same time, by removing droplets in the gas, the operating conditions in the fluidized bed adsorption tower can be improved, the gas humidity can be reduced, and the adsorption efficiency and stability of the adsorbent can be improved.

[0018] (3) A filter baffle is also provided at the upper end of the fluidized bed adsorption tower. When the fluidization velocity is very high, the solid particles may be discharged under the action of the rising force of the gas phase. The filter baffle can prevent the solid particles from being carried out by the gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a diagram of the device of the present utility model;

[0020] Figure 2 This is a diagram of the fluidized bed adsorption tower device of the utility model.

[0021] In the figure: 1-condenser, 2-gas-liquid separator, 3-fluidized bed adsorption tower, 4-adsorbent feed buffer tank, 5-adsorbent discharge buffer tank, 6-desorption tower, 31-filter baffle, 32-inclined plate, 33-demister. DETAILED DESCRIPTION

[0022] The following is a detailed description of the present invention, clearly and completely describing the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] Example 1

[0024] A device for continuously circulating adsorption and desorption to treat VOCs waste gas in CEC tail gas, the structure of which is as follows Figure 1 As shown, it includes a condensation separation unit and an adsorption desorption unit connected in sequence.

[0025] The condensation separation unit includes a condenser 1 and a gas-liquid separator 2 which are sequentially connected through a pipeline; the discharge port of the condenser 1 is connected to the upper feed port of the gas-liquid separator 2, and the upper gas outlet of the gas-liquid separator 2 is connected to the adsorption and desorption unit.

[0026] The adsorption and desorption unit includes a fluidized bed adsorption tower 3 and a desorption tower 6. The discharge port at the bottom of the fluidized bed adsorption tower 3 is connected to the adsorbent feed port at the bottom of the desorption tower 6, and the top air outlet of the fluidized bed adsorption tower 3 is connected to the subsequent gas purification process; the adsorbent discharge port at the top of the desorption tower 6 is connected to the upper feed port of the fluidized bed adsorption tower 3; the upper air outlet of the gas-liquid separator 2 is connected to the air inlet of the fluidized bed adsorption tower 3; and the air outlet at the top of the desorption tower 6 is connected to a vacuum pump.

[0027] An adsorbent discharge buffer tank 5 is provided between the bottom discharge port of the fluidized bed adsorption tower 3 and the adsorbent feed port at the bottom of the desorption tower 6; an adsorbent feed buffer tank 4 is provided between the adsorbent discharge port at the top of the desorption tower 6 and the upper feed port of the fluidized bed adsorption tower 3.

[0028] The CEC tail gas first passes through the condenser 1 and the gas-liquid separator 2 to perform preliminary separation of easily condensable impurities (VOCs, etc.) and product gas (HCl and Cl2). The gas then enters the fluidized bed adsorption tower 3. The structure of the fluidized bed adsorption tower 3 is as follows: Figure 2 As shown, an inclined plate tower structure is employed, with the adsorbent within the tower dynamically circulating for adsorption. The gas mass flow rate within the tower is 500-2000 kg / hr. The number of inclined plates 32 in the fluidized bed adsorption tower 3 ranges from 2 to 10, with a downward inclination angle of 0-45°. Filter holes with a diameter of φ less than 0.5 mm are evenly distributed on the inclined plates 32. The adsorbent within the fluidized bed adsorption tower 3 is a combination of one or more of resin, molecular sieve, activated carbon, silica gel, and metal-organic frameworks (MOFs). Under the influence of airflow and gravity, the adsorbent boils and fluidizes, fully contacting the gas and effectively adsorbing VOC impurities. The adsorbed gas is discharged from the top of the fluidized bed adsorption tower 3 and enters the subsequent gas purification process to produce high-purity HCl and Cl2. The saturated adsorbent descends layer by layer, ultimately passing through the adsorbent discharge port of the fluidized bed adsorption tower into the adsorbent discharge buffer tank 5, and then into the desorption tower 6 for desorption and regeneration. The adsorbent is desorbed and regenerated under the high temperature and negative pressure within desorption tower 6. Simultaneously, the regenerated adsorbent is lifted by the spiral and enters the adsorbent feed buffer tank 4, ultimately being fed into the fluidized bed adsorption tower for recycling. High-concentration VOCs in desorption tower 6 are extracted by a vacuum pump and sent to subsequent treatment processes for discharge after meeting standards.

[0029] The fluidized bed adsorption tower 3 is also equipped with a filter baffle 31 at its upper end, positioned above the adsorbent inlet and below the gas outlet. A demister 33 is also provided at its lower end, positioned above the gas inlet and below the adsorbent outlet. VOCs discharged from the top outlet of the desorption tower are transported to the VOC treatment process via a vacuum pump.

Claims

1. A device for continuously cyclically adsorbing and desorbing VOCs waste gas in CEC tail gas, characterized in that: It includes a condensation separation unit and an adsorption desorption unit connected in sequence; The condensation separation unit includes a condenser and a gas-liquid separator connected in sequence through a pipeline; the discharge port of the condenser is connected to the upper feed port of the gas-liquid separator, and the upper gas outlet of the gas-liquid separator is connected to the adsorption and desorption unit; The adsorption and desorption unit includes a fluidized bed adsorption tower and a desorption tower. The discharge port at the bottom of the fluidized bed adsorption tower is connected to the adsorbent feed port at the bottom of the desorption tower, and the top air outlet of the fluidized bed adsorption tower is connected to the subsequent gas purification process; the adsorbent discharge port at the top of the desorption tower is connected to the upper feed port of the fluidized bed adsorption tower; the upper air outlet of the gas-liquid separator is connected to the air inlet of the fluidized bed adsorption tower; and the air outlet at the top of the desorption tower is connected to a vacuum pump.

2. The device for treating VOCs waste gas in CEC tail gas by continuous cycle adsorption and desorption according to claim 1, characterized in that: An adsorbent discharge buffer tank is provided between the discharge port at the bottom of the fluidized bed adsorption tower and the adsorbent feed port at the bottom of the desorption tower.

3. The device for treating VOCs waste gas in CEC tail gas by continuous cycle adsorption and desorption according to claim 1 or 2, characterized in that: An adsorbent feed buffer tank is provided between the adsorbent discharge port at the top of the desorption tower and the upper feed port of the fluidized bed adsorption tower.

4. The device for treating VOCs waste gas in CEC tail gas by continuous cycle adsorption and desorption according to claim 1, characterized in that: The fluidized bed adsorption tower is provided with 2 to 10 layers of inclined plates, which are inclined downward by 0 to 45 degrees. Filter holes are evenly distributed on the inclined plates, and the diameter of the filter holes is φ less than 0.5 mm.

5. The device for treating VOCs waste gas in CEC tail gas by continuous cycle adsorption and desorption according to claim 4, characterized in that: A filter baffle is further provided at the upper end of the fluidized bed adsorption tower; the filter baffle is higher than the adsorbent inlet of the fluidized bed adsorption tower and lower than the gas outlet.

6. The device for treating VOCs waste gas in CEC tail gas by continuous cycle adsorption and desorption according to claim 4 or 5, characterized in that: The lower end of the fluidized bed adsorption tower is further provided with a demister, which is higher than the gas inlet of the fluidized bed adsorption tower and lower than the adsorbent discharge port.

7. The device for treating VOCs waste gas in CEC tail gas by continuous cycle adsorption and desorption according to claim 6, characterized in that: The VOCs discharged from the gas outlet at the top of the desorption tower are transported to the VOCs treatment process through a vacuum pump.

Images