A pretreatment system for on-line analysis of CO2 concentration in tail gas of combined soda calcination furnace

Abstract

The utility model discloses a kind of pretreatment systems for combined soda calcination furnace tail gas CO2 concentration on-line analysis, including the heat tracing sampling unit, water washing tank, compression refrigerator, desulfurization tank, first drying tank, air pump, second drying tank, fine filter tank, sample gas rotor flowmeter and on-line analyzer sequentially connected along sample gas flow direction.Heat tracing sampling unit prevents sample gas dew blockage;Water washing tank quenching washing removes ammonia and alkali dust, equipped with glass tube liquid level meter and water inlet, sewage rotor flowmeter realizes liquid level monitoring and quantitative control;Compression refrigerator condensation dehumidification;Desulfurization tank and double-stage drying tank adsorb sulfide and moisture;Air pump pressurized delivery clean gas;Bipolar peristaltic pump handles condensate and waste water, through the innovative process of 'purification before delivery', solve the crystallization blockage under normal operating condition, equipment corrosion and data distortion etc., significantly improve system operation reliability, analysis accuracy, real-time and automation level, reduce maintenance cost.

Description

Technical Field

[0001] This utility model relates to the field of industrial gas analysis technology, and more specifically, to a pretreatment system for online analysis of CO2 concentration in tail gas from a soda ash calciner. Background Technology

[0002] In the combined alkali production process, the tail gas produced by the calcination and decomposition of heavy alkali (NaHCO3) is rich in CO2 (≥75%). This tail gas is the core raw material gas for carbon recovery and utilization. The accurate and continuous online monitoring of its CO2 concentration is directly related to the calculation of carbon utilization rate, monitoring of calciner operation status, optimization of energy consumption and improvement of production economic benefits.

[0003] However, under normal operating conditions, the exhaust gas from the calcining furnace has four high characteristics: high CO2 (≥75 vol%), high water vapor (relative humidity ≥90%, close to saturation), high alkaline dust (≥150 mg / m³, mainly Na2CO3, NaHCO3, etc.), and high NH3 (≥0.8 vol%). In addition, the operating temperature is 50-70℃ and the system negative pressure is ≥-3KPa, which poses a challenge to the suction capacity of the sampling system. At the same time, NH3 and CO2 easily react to form ammonium carbonate / ammonium bicarbonate crystals in a low-temperature and water-containing environment, and ammonia water can also cause strong corrosion to metal parts.

[0004] The traditional pretreatment process currently used in the industry, such as Figure 2 As shown, the process of "sampling of calcining furnace tail gas main → extraction pump → cyclone cooler → separator → drying tank → rotor flow meter → analytical instrument" has the following defects when applied to this operating condition:

[0005] 1. Extremely poor reliability: High temperature and high humidity gas samples are only treated briefly before entering the air pump. Water vapor condenses and combines with alkaline dust and ammonia, which can easily lead to pump body corrosion and jamming, filter element pipeline blockage, and the system cannot operate stably for a long period of time.

[0006] 2. Severely distorted analytical data: NH3 was not preferentially removed and reacted with CO2 in subsequent processes, consuming the analyte and causing the analyzer's measured values ​​to be severely low, thus losing their guiding significance.

[0007] 3. Huge maintenance workload: Frequent blockages and corrosion lead to high maintenance costs, extremely low instrument uptime, and high equipment failure and damage rates.

[0008] Therefore, developing a dedicated preprocessing system that can specifically address the above problems and ensure analytical accuracy, long-term system stability and reliability, and low maintenance is a technological breakthrough urgently needed in this field. Utility Model Content

[0009] This utility model provides a pretreatment system for online analysis of CO2 concentration in the tail gas of a soda ash calciner. The problem it addresses is the technical pain points of existing pretreatment systems under normal operating conditions, such as poor operational reliability, distorted CO2 concentration analysis data, high maintenance workload, and susceptibility to crystallization blockage and equipment corrosion. This system offers an optimized process, precise control, and highly efficient purification capability, enabling stable sampling and deep purification of the sample gas (removal of NH3, alkali dust, water vapor, and sulfides). This ensures long-term stable operation of the online analyzer, while improving the accuracy and timeliness of monitoring data and reducing maintenance costs.

[0010] To achieve the above objectives, this utility model provides the following technical solution:

[0011] A pretreatment system for online analysis of CO2 concentration in the tail gas of a soda ash calciner includes a series of corrosion-resistant pipelines connected sequentially along the sample gas flow direction.

[0012] A heated sampling unit is used to prevent condensation and blockage of the sample gas before it enters the pretreatment system;

[0013] The water washing tank rapidly cools and washes the sample gas to remove ammonia and alkaline dust.

[0014] A compressor refrigeration unit is used to condense and dehumidify saturated moisture after it has been washed with water.

[0015] Desulfurization tanks are filled with desulfurizing agents to remove sulfides;

[0016] The first drying tank is used to absorb residual moisture and achieve initial drying.

[0017] A vacuum pump is used to extract, pressurize, and transport processed gas.

[0018] The second drying tank is used for the final drying of the treated gas;

[0019] Fine filter canisters are used to filter treated gases.

[0020] Sample gas rotor flow meter, used to display and adjust gas flow rate;

[0021] The online analyzer is used to receive sample gas for online CO2 concentration analysis and transmit the analysis results to the DCS system.

[0022] Through an innovative process layout of "heated sampling - water washing and impurity removal - refrigeration and dehumidification - desulfurization and drying - power transmission - terminal fine treatment", the air extraction pump is placed after the purification unit, and works with a bipolar peristaltic pump to simultaneously treat condensate and wastewater. This fundamentally solves the problems of crystallization blockage and equipment corrosion under normal operating conditions, greatly improves the reliability of long-term system operation, ensures the authenticity and validity of CO2 concentration analysis data, and provides accurate central control data support for production operation.

[0023] Furthermore, the heat-traced sampling unit includes a sampling probe and a heat-traced pipeline. The heat-traced pipeline is an electric heat-traced pipeline, and the temperature control value of the heat-traced sampling unit is ≥120℃. This effectively avoids condensation of the sample gas due to a sudden drop in temperature during the sampling stage, prevents alkaline dust from combining with condensate to form blockages, ensures the representativeness and continuity of the sampling, and lays the foundation for subsequent purification treatment.

[0024] Furthermore, a glass tube level gauge is installed on the side wall of the washing tank. The glass tube level gauge is used to observe the liquid level and water quality changes, promptly detect abnormal liquid levels and water quality deterioration, provide a visual basis for operators to accurately adjust parameters, reduce the difficulty of operation, and ensure stable water washing and purification effects.

[0025] Furthermore, the water inlet of the washing tank is connected to a water supply rotor flow meter, and the drain outlet of the washing tank is connected to a drain rotor flow meter. The water supply rotor flow meter and the drain rotor flow meter respectively control the water supply and drain of the washing tank. The water supply rotor flow meter and the drain rotor flow meter respectively achieve precise control of the water supply volume and the liquid discharge volume, ensuring that the liquid level of the washing tank is maintained at the optimal washing height and dynamically balanced. This ensures the removal efficiency of NH3 and alkaline dust, avoids the accumulation of impurities, and extends the service life of the washing tank.

[0026] Furthermore, it also includes a bipolar peristaltic pump. The bottom condensate outlet of the compressor and the drain outlet of the water washing tank are both connected to the bipolar peristaltic pump. The bipolar peristaltic pump simultaneously processes the condensate of the compressor and the wastewater of the water washing tank, realizing automatic, continuous, and leak-free drainage, avoiding crystallization blockage or pipeline corrosion caused by the accumulation of condensate and wastewater, improving the system's automation level, and reducing the frequency of manual intervention.

[0027] Furthermore, the compressor cooler is a semiconductor cooler or a mechanical compression cooler with a temperature control range of 2 to 5°C. It can efficiently precipitate most of the water vapor, significantly reduce the dew point of the sample gas, reduce the load on the subsequent drying unit, and prevent high-humidity gas from entering the online analyzer, affecting the detection accuracy, or even causing the online analyzer to malfunction or be damaged.

[0028] Furthermore, the air pump adopts a corrosion-resistant diaphragm pump or vortex pump, which effectively avoids pump body corrosion and wear, extends the service life of the air pump, and ensures the stability of power transmission.

[0029] Furthermore, the fine filter tank contains a removable and replaceable filter element with a filtration accuracy of ≥0.1μm, ensuring that the sample gas entering the online analyzer meets the cleanliness standards, preventing tiny impurities from wearing down or contaminating the core components of the analyzer, and extending the analyzer's service life.

[0030] Furthermore, the washing tank is either a bubbling type or a spray type, which increases the contact area and contact time between the sample gas and the washing liquid, improves the rapid cooling and washing effect, and can more efficiently and thoroughly remove NH3 and alkaline dust from the sample gas, eliminating subsequent crystallization and corrosion problems from the source.

[0031] Furthermore, both the first and second drying tanks are filled with desiccant, which is color-changing silica gel or molecular sieve, with large adsorption capacity and fast adsorption speed, effectively adsorbing residual moisture in the sample gas.

[0032] The beneficial effects of this utility model are as follows:

[0033] 1. Significantly improved operational reliability: Following the principle of "thorough purification first, then power delivery", the air pump is placed after water washing, cooling and drying, so that it can process clean gas. This solves the core pain points of crystallization, blockage and corrosion in traditional systems and extends the continuous operation cycle of the system.

[0034] 2. High accuracy of monitoring data: The water washing tank prioritizes and efficiently removes NH3, preventing the consumption of CO2. After deep dehumidification, two-stage drying and high-precision filtration, the treated sample gas is highly consistent with the laboratory chromatographic analysis results, providing reliable data support for production operations.

[0035] 3. Significantly reduced operation and maintenance costs: Visual monitoring and quantitative water replenishment and drainage control of the water washing tank, combined with automatic drainage by a bipolar peristaltic pump, enable automated system operation. Maintenance only requires periodic checks of the desiccant and desulfurizer, reducing maintenance workload and lowering labor and consumable costs. Attached Figure Description

[0036] The present invention will be further described below with reference to the accompanying drawings:

[0037] Figure 1 This is a schematic diagram of the pretreatment system for online analysis of CO2 concentration in tail gas from a combined alkali calciner according to the present invention.

[0038] Figure 2 This is a flowchart illustrating the prior art of this utility model; Detailed Implementation

[0039] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0040] like Figure 1 As shown, this utility model discloses a pretreatment system for online analysis of CO2 concentration in tail gas from a combined alkali calciner. The system includes a heated sampling unit connected sequentially along the gas flow direction via corrosion-resistant pipes to prevent condensation and blockage of the sample gas before it enters the pretreatment system; a water washing tank for rapid cooling and washing of the sample gas to remove ammonia and alkali dust; a compressor / refrigerator for condensing and dehumidifying the saturated wet gas after water washing; a desulfurization tank filled with desulfurizing agent to remove sulfides; a first drying tank for adsorbing residual moisture and achieving initial drying; a vacuum pump for extracting and transporting the treated gas; a second drying tank for final drying of the treated gas; a fine filter tank for filtering the treated gas; a sample gas rotor flow meter for displaying and adjusting the gas flow rate; and an online analyzer for receiving the pretreated sample gas for online CO2 concentration analysis and transmitting the analysis results to the DCS system in real time via a 4-20mA DC-DC signal.

[0041] In this embodiment, the sample gas rotor flow meter can be equipped with a bypass rotor flow meter to ensure the flow rate, thereby ensuring the real-time nature of the analysis data.

[0042] Through an innovative process layout of "heated sampling - water washing to remove impurities - refrigeration and dehumidification - desulfurization and drying - power transmission - terminal fine treatment", the air extraction pump is placed after the purification unit, and works with a bipolar peristaltic pump to simultaneously treat condensate and wastewater. This fundamentally solves the problems of crystallization blockage and equipment corrosion under normal operating conditions, greatly improves the reliability of long-term system operation, ensures the authenticity and validity of CO2 concentration analysis data, and provides accurate central control data support for production operation.

[0043] The heat-traced sampling unit includes a sampling probe and a heat-traced pipeline. The heat-traced pipeline is an electric heat-traced pipeline, and the temperature control value of the heat-traced sampling unit is ≥120℃. This effectively avoids condensation of the sample gas due to a sudden drop in temperature during the sampling stage, prevents alkaline dust from combining with condensate to form blockages, ensures the representativeness and continuity of the sampling, and lays the foundation for subsequent purification treatment.

[0044] The innovative design of the water washing tank, as the core of primary treatment, lies in:

[0045] Visual monitoring: A glass tube level gauge is installed on the side wall of the washing tank. The glass tube level gauge is used to observe the liquid level and water quality changes, and to detect abnormal liquid levels and water quality deterioration in a timely manner. It provides a visual basis for operators to accurately adjust parameters, reduces the difficulty of operation, and ensures stable water washing and purification effects.

[0046] Quantitative control: The water inlet of the washing tank is connected to a water supply rotor flow meter, and the drain outlet of the washing tank is connected to a drain rotor flow meter. The water supply rotor flow meter and the drain rotor flow meter respectively control the water supply and drain of the washing tank. The water supply rotor flow meter and the drain rotor flow meter respectively achieve precise control of the water supply volume and the liquid discharge volume, ensuring that the liquid level of the washing tank is maintained at the optimal washing height and dynamically balanced. This ensures the removal efficiency of NH3 and alkaline dust, avoids the accumulation of impurities, and extends the service life of the washing tank.

[0047] The water washing tank is used to rapidly cool and wash the sample gas, effectively removing most of the alkaline dust and key interfering substances such as NH3.

[0048] The condensate outlet at the bottom of the compressor and the drain outlet of the water washing tank are both connected to a bipolar peristaltic pump. The bipolar peristaltic pump simultaneously processes the condensate from the compressor and the wastewater from the water washing tank, achieving automatic, continuous, and leak-free drainage. This avoids crystallization blockage or pipeline corrosion caused by the accumulation of condensate and wastewater, improves the system's automation level, and reduces the frequency of manual intervention.

[0049] The compressor cooler, whether a semiconductor cooler or a mechanical compressor cooler, is connected to the outlet of the water washing tank and serves as the core of the secondary dehumidification process. It deeply condenses the sample gas to 2–5°C, efficiently releasing most of the water vapor and significantly reducing the dew point of the sample gas. This reduces the load on the subsequent drying unit and prevents high-humidity gas from entering the online analyzer, affecting the detection accuracy, or even causing the online analyzer to malfunction or be damaged.

[0050] The air pump uses a corrosion-resistant diaphragm pump or vortex pump, which effectively avoids pump body corrosion and wear, extends the service life of the air pump, and ensures the stability of power transmission. The air pump is critically located after the above-mentioned purification unit to process clean and dry gas, fundamentally avoiding damage.

[0051] The fine filter canister is equipped with a removable filter element with a filtration accuracy of ≥0.1μm, ensuring that the sample gas entering the online analyzer meets the cleanliness standards, preventing tiny impurities from wearing or contaminating the core components of the analyzer, and extending the service life of the analyzer.

[0052] The washing tank is either a bubbling type or a spray type, which increases the contact area and contact time between the sample gas and the washing liquid, improves the rapid cooling and washing effect, and can more efficiently and thoroughly remove NH3 and alkaline dust from the sample gas, eliminating subsequent crystallization and corrosion problems from the source.

[0053] Both the first and second drying tanks are filled with desiccant, which is color-changing silica gel or molecular sieve. It has a large adsorption capacity and fast adsorption speed, which can effectively adsorb residual moisture in the sample gas and is easy to maintain and replace.

[0054] The following is an illustration through a specific embodiment:

[0055] Calcination furnace exhaust gas parameters (vol%): CO2~76%, NH3~1.0%, water vapor~23%, temperature~60℃, pressure~-2.8kPa, alkali dust~180mg / m³.

[0056] This system is in accordance with Figure 1 The installation connections shown are all made of PTFE or 316L stainless steel.

[0057] The heat tracing sampling unit uses electric heat tracing, and the temperature is set to 120 degrees Celsius.

[0058] The washing tank adopts a bubbling type, and the glass tube level gauge clearly displays that the liquid level is maintained at 2 / 3 of the tank height. The water supply is controlled at 60 mL / min by adjusting the valve of the water supply rotor flow meter. The discharge flow rate is controlled at 60 mL / min by the combined action of the valve of the sewage discharge rotor flow meter and the bipolar peristaltic pump, thus achieving dynamic balance.

[0059] The compressor refrigeration unit uses Peltier refrigeration and has a temperature control of (4.0±0.5)℃. The condensate is continuously discharged by a bipolar peristaltic pump.

[0060] The desulfurization tank is filled with room temperature iron oxide desulfurizing agent.

[0061] The first and second drying tanks are filled with color-changing silica gel or molecular sieves.

[0062] The air pump uses a corrosion-resistant diaphragm pump.

[0063] The fine filter canister is fitted with a 0.1μm PTFE filter element.

[0064] The speed of the bipolar peristaltic pump is adjusted to match the inlet and outlet flow rates.

[0065] After the system was put into operation, the treated sample gas achieved the following: atmospheric pressure, dew point < -25℃, dust content < 0.1μm, no NH3, and no sulfides. The CO2 analyzer 10 operated stably, displaying a value of approximately 75.8%, which highly matched the laboratory chromatographic analysis results (76.1%). The system ran continuously for over 120 days, requiring only periodic checks of the desiccant and desulfurizer, without any blockages or corrosion failures, reducing maintenance workload by more than 90%.

[0066] A pretreatment method for online analysis of CO2 concentration in the tail gas of a soda ash calciner includes:

[0067] S1. Sample gas is extracted under heat preservation conditions through the heat-traced sampling unit;

[0068] S2. The sample gas is introduced into the water washing tank for rapid cooling and washing to remove most of the ammonia and alkaline dust; the liquid level is monitored by the glass tube level gauge, and the water supply and drainage are quantitatively controlled by adjusting the water supply rotor flow meter and the sewage discharge rotor flow meter to maintain the dynamic balance of the liquid level in the water washing tank.

[0069] S3. The saturated humid gas after water washing is introduced into the compressor refrigeration unit for deep condensation and dehumidification, and the condensate produced is continuously discharged by the bipolar peristaltic pump.

[0070] S4. The dehumidified gas is passed sequentially through the desulfurization tank and the first drying tank for desulfurization and primary drying.

[0071] S5. Use an air pump to extract and transport the treated gas;

[0072] S6. The gas is sequentially passed through the second drying tank and the fine filter tank for final drying and filtration.

[0073] S7. Use a sample gas rotor flow meter to adjust the gas flow rate and send the qualified sample gas into the online analyzer for CO2 concentration analysis;

[0074] S8. Wastewater generated by the washing tank is continuously discharged by a bipolar peristaltic pump.

[0075] The above embodiments only illustrate several implementation methods of this utility model, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this utility model patent. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model.

Claims

1. A pretreatment system for online analysis of CO2 concentration in tail gas from a soda ash calciner, characterized in that: The system includes a heat-traced sampling unit connected sequentially along the sample gas flow direction via corrosion-resistant pipelines to prevent condensation and blockage of the sample gas before it enters the pretreatment system; a water washing tank for rapid cooling and washing of the sample gas to remove ammonia and alkaline dust; a compressor cooler for condensing and dehumidifying the saturated humid gas after water washing; a desulfurization tank filled with desulfurizing agent to remove sulfides; a first drying tank for adsorbing residual moisture to achieve initial drying; and a vacuum pump for extracting, pressurizing, and transporting the treated gas. The second drying tank is used for the final drying of the treated gas; A fine filter canister is used to filter the treated gas; a sample gas rotor flow meter is used to display and adjust the gas flow rate. The online analyzer is used to receive sample gas for online CO2 concentration analysis and transmit the analysis results to the DCS system.

2. The pretreatment system for online analysis of CO2 concentration in tail gas from a soda ash calciner according to claim 1, characterized in that: The heat tracing sampling unit includes a sampling probe and a heat tracing pipeline. The heat tracing pipeline is an electric heat tracing pipeline, and the temperature control value of the heat tracing sampling unit is ≥120℃.

3. The pretreatment system for online analysis of CO2 concentration in tail gas from a soda ash calciner according to claim 1, characterized in that: A glass tube level gauge is installed on the side wall of the washing tank. The glass tube level gauge is used to observe the liquid level and water quality changes.

4. The pretreatment system for online analysis of CO2 concentration in tail gas from a soda ash calciner according to claim 1, characterized in that: The water inlet of the washing tank is connected to a water supply rotor flow meter, and the sewage outlet of the washing tank is connected to a sewage discharge rotor flow meter. The water supply rotor flow meter and the sewage discharge rotor flow meter respectively realize the measurement and control of water supply and sewage discharge of the washing tank.

5. The pretreatment system for online analysis of CO2 concentration in tail gas from a soda ash calciner according to claim 1, characterized in that: It also includes a bipolar peristaltic pump, with the bottom condensate outlet of the compressor and the drain outlet of the water washing tank both connected to the bipolar peristaltic pump.

6. The pretreatment system for online analysis of CO2 concentration in tail gas from a soda ash calciner according to claim 1, characterized in that: The compression cooler is a semiconductor cooler or a mechanical compression cooler, with a temperature control range of 2 to 5°C.

7. The pretreatment system for online analysis of CO2 concentration in tail gas from a soda ash calciner according to claim 1, characterized in that: The air pump is a corrosion-resistant diaphragm pump or a vortex pump.

8. The pretreatment system for online analysis of CO2 concentration in tail gas from a soda ash calciner according to claim 1, characterized in that: The fine filter canister is equipped with a removable and replaceable filter element, and the filter element has a filtration accuracy of ≥0.1μm.

9. The pretreatment system for online analysis of CO2 concentration in tail gas from a soda ash calciner according to claim 1, characterized in that: The washing tank is either a bubbling type or a spray type.

10. The pretreatment system for online analysis of CO2 concentration in tail gas from a soda ash calciner according to claim 1, characterized in that: Both the first and second drying containers are filled with a desiccant, which is color-changing silica gel or molecular sieve.

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