CN103472061A - Device and method for detecting sulfur trioxide in flue gas on line - Google Patents

Abstract

The invention discloses an online detection device and method for sulfur trioxide in flue gas. The device includes a flue gas collection unit; a gas-liquid separator for condensing _SO3 in the flue gas from the flue gas sampling unit into sulfuric acid liquid drop to separate from the gas phase; a gas phase detection unit for metering the gas phase flow from the gas-liquid separator; a first solution tank for providing absorption liquid in the gas-liquid separator to mix the sulfuric acid droplets to form Mixed liquid; liquid-phase detection unit, for measuring the quality of the converted _SO in the mixed liquid from said gas-liquid separator; digital control unit, for detecting the result according to said gas-phase detection unit and liquid-phase detection unit Calculate the concentration of SO ₃ in the flue gas. The invention realizes the on-line measurement of SO ₃ in the flue gas, samples the SO ₃ in the flue gas, and analyzes the content of SO ₃ , which is convenient for coal-fired power plants to take corresponding measures to control the SO ₃ content in the flue gas and reduce the impact on the flue gas. Corrosion of the pipeline and its equipment, while minimizing the heat loss of the boiler exhaust.

Description

An online detection device and method for sulfur trioxide in flue gas

technical field

The invention relates to the technical field of flue gas treatment, in particular to an online detection device and method for sulfur trioxide in flue gas.

Background technique

Although SO ₃ emissions from thermal power plants are very small, SO ₃ is easily combined with water vapor in the flue gas to form sulfuric acid vapor, which condenses on the heating surface whose wall temperature is lower than the acid dew point, causing acid dew point corrosion. The more SO ₃ in the flue gas, the higher the acid dew point temperature, and the wider and more serious the corrosion range. In recent years, more and more power plants in China have installed wet flue gas desulfurization. Due to the high humidity of the net flue gas after wet desulfurization, the residual SO ₃ in the flue gas is easily and quickly converted into sulfuric acid droplets, which is harmful to the flue and Severe corrosion of downstream equipment. _SO concentrations as low as 5-10 ppm in the flue gas produce white, purple or black plumes as the hot flue gas cools in cooler air in the atmosphere.

Selective catalytic reduction reaction (selective catalytic reactor, SCR) is a measure adopted in power plants to control NO _x emissions. In the case of adding NH ₃ , SCR reduces NO _x to N ₂ , but also causes a small amount of SO ₂ conversion For SO ₃ , although SO ₃ is not present in high concentrations, it emits a highly visible secondary plume.

In order to solve the problem of acid dew point corrosion, power plants need to know the concentration of SO ₃ in the flue gas. So far, no flue gas analyzer has been found to have the function of measuring SO ₃ content. This is mainly because SO ₃ In the form of sulfuric acid vapor or sulfuric acid mist, it will condense or adhere to the transmission pipeline, resulting in sampling errors and strong corrosion of the instrument.

The measurement of solid particulate matter in flue gas was proposed in "Determination of Particulate Matter in Exhaust from Stationary Pollution Sources and Sampling Method of Gaseous Pollutants", without considering the measurement of liquid particulate matter such as SO ₃ . In fact, the emission concentration of SO ₃ in the flue gas can reach more than 10 mg/m ³ , and the concentration of SO ₃ after SCR denitrification can reach 30-80 mg/m ³ , which has become the main problem of fine particle pollution in coal-fired power plants.

Various techniques for measuring _SO3 concentration in flue gas have been developed in the art. The new utility patent with the patent number of 200620163937.1 discloses a sampling device for _SO3 in flue gas, including a dust removal mechanism, a sampling pipe, a spiral collection pipe and a suction mechanism, wherein the dust removal mechanism is installed at the inlet end of the sampling pipe, and the sampling pipe The outlet end of the spiral collection pipe is connected with the inlet of the spiral collection pipe through a pipeline, the inlet and outlet of the spiral collection pipe are located at the upper end of the spiral shape, and the outlet communicates with the suction mechanism through a silicone hose. There is no measurement part in the patent, and online measurement cannot be realized.

Patent No. 20091021169.1 discloses a method and device for detecting, measuring and controlling SO ₃ and other condensables in flue gas. It can measure the concentration of various condensables. The requirements are high, and online continuous measurement cannot be realized. In the United States, Patent No. 2011/0097809 discloses a SO ₃ measurement method with high precision, but the device is inconvenient to carry and is suitable for laboratory operation.

Contents of the invention

The invention provides an on-line detection device and method for sulfur trioxide in flue gas to analyze the content of _SO3 in the flue gas, realize the on-line measurement of _SO3 in the flue gas, and has the characteristics of simple structure and portability.

An on-line detection device for sulfur trioxide in flue gas, including a flue gas sampling unit, also includes:

A gas-liquid separator for condensing _SO3 in the flue gas from the flue gas sampling unit into sulfuric acid droplets for separation from the gas phase;

a gas phase detection unit, used to measure the gas phase flow from the gas-liquid separator;

The first solution tank is used to provide absorption liquid to the gas-liquid separator to mix the sulfuric acid droplets to form a mixed liquid;

A liquid phase detection unit for measuring the _converted SO in the mixed liquid from the gas-liquid separator Quality;

The digital control unit is used to calculate the concentration of SO ₃ in the flue gas according to the detection results of the gas phase detection unit and the liquid phase detection unit.

The gas-liquid separator can be implemented in a variety of ways. In the present invention, as a preference,

The gas-liquid separator is a plurality of serpentine condensers connected in parallel, the inlet of the serpentine condenser communicates with the flue gas sampling unit and the first solution tank through corresponding pipes and valves, the serpentine condenser The outlet of the outlet communicates with the gas phase detection unit and the liquid phase detection unit through corresponding pipes and valves.

In order to facilitate the separation of the gas phase, it is further preferred that an air pump is provided between the gas phase detection unit and the outlet of the corresponding serpentine condenser for pumping the gas in the serpentine condenser into the gas phase detection unit. The negative pressure generated by the air pump separates the gas in the corresponding serpentine condenser tube and measures it through the gas phase detection unit.

The serpentine condensing pipe, the first solution tank, the gas phase detection unit, the corresponding valve and the liquid phase detection unit constitute the _SO3 detection unit. The flue gas sampling unit continuously collects the flue gas to be tested, and then enters the serpentine condensing pipe. Due to the temperature in the condensing pipe Below the dew point of sulfuric acid, sulfuric acid droplets are formed in the serpentine tube to separate SO ₃ from the flue gas. After sampling, absorbing liquid is added to the serpentine tube to form sulfuric acid droplets (SO ₄ ^2- ), serpentine The solution in the tube is sent to the liquid phase detection unit for detection, first add barium salt solution, and form a precipitate after stirring, the SO ₄ ^2- concentration is detected by the optical system, and the SO ₃ detection unit sends the gas-liquid two-phase detection information to the digital control unit , is received and calculated by the digital control unit to calculate the content of SO ₃ in the flue gas to be tested.

Further preferably, a thermostatic chamber for installing the serpentine condensing pipe is also provided. The temperature of the thermostatic chamber is controlled to be 60-80°C.

Further preferably, the diameter of the serpentine condenser is 8-15cm.

In the SO ₃ detection unit, the serpentine condensing pipe in the thermostatic chamber condenses the flue gas from the flue gas sampling unit to separate SO ₃ in the flue gas, and the flue gas flow rate is detected by the gas phase detection unit.

The gas-liquid separator can be several serpentine condenser tubes connected in parallel, and the serpentine condenser tubes work alternately. As a preferred technical solution of the present invention, the gas-liquid separator is two parallel-connected Serpentine condenser.

The device is provided with control valves corresponding to the two serpentine condensers, which are used to replace one serpentine condenser after sampling. After the collection of one of the serpentine condenser tubes is completed, the absorption liquid is added to the serpentine tube, and the SO ₃ in the flue gas to be measured will eventually form SO ₄ ^2- which exists in the liquid phase mixture, and the SO ₄ ² is detected by the liquid phase detection unit ^- the amount.

The gas phase detection unit includes a flowmeter, a thermometer and a barometer, and simultaneously records the temperature and pressure information of the gas phase.

The liquid phase detection unit is used to detect _SO in the flue gas Content, a kind of preferred technical scheme, described liquid phase detection unit comprises:

A reactor communicated with the outlet of the serpentine condenser;

A second air pump connected to the inlet of the serpentine condenser, used to hydraulically inject the mixture in the serpentine condenser into the reactor;

a light source for emitting detection light to the reactor;

A photometer for receiving transmitted light through the reactor, the photometer being communicatively connected to the digital control unit.

Further preferably, there is also a second solution tank connected to the reactor through a liquid pump, and the reactor is provided with a magnetic stirrer.

The solution tank is filled with substances that can react with SO ₄ ^2- and generate colored ions or precipitates, for example, barium salts, and the liquid phase from the gas-liquid separator reacts with the substances in the reactor, and then The detection light is emitted into the reactor, and is received by the photometer after passing through the liquid in the reactor. The photometer sends the received information to the digital control unit, and the digital control unit calculates the amount of SO ₃ .

Preferably, the barium salt in the solution tank of the liquid phase detection unit is barium chloride, barium chlorate or barium perchlorate.

The flue gas sampling unit is used to continuously collect the flue gas containing SO ₃ and send it into the SO ₃ detection unit. As far as the sampling unit itself is concerned, it can be an existing sampling mechanism. In the present invention, as a preferred technical solution, The flue gas sampling unit includes a flue gas sampling gun head, a filter chamber and a flue gas sampling pipe connected in sequence, the tail end of the flue gas sampling pipe communicates with the gas-liquid separator, and the filter chamber is provided with a filter device.

In order to ensure the temperature of the flue gas to be measured, _all the SO in the flue gas exists in a gaseous state, preferably, the outside of the flue gas sampling pipe is provided with a heating device for maintaining the temperature in the flue gas sampling pipe, and the outside of the heating device is Has an insulating outer layer.

The heating device is preferably an electric heating device wound outside the flue gas sampling pipe to heat the flue gas to be measured in the flue gas sampling pipe.

The flue gas sampling pipe is a steel pipe made of anti-rust material. An electric heating device is installed outside the steel pipe to heat the temperature of the steel pipe so that the temperature of the flue gas inside the steel pipe is kept at 300-400°C. Insulating outer layer made of material.

In order to facilitate the collection and control of the flue gas temperature, preferably, a temperature acquisition device is provided outside the flue gas sampling pipe, and the temperature acquisition device is connected to the digital control unit by communication.

Preferably, the digital control unit includes a housing and a central processing unit located in the housing, and the housing is provided with control buttons and a display screen.

The shell is used to place the control button and the display screen, the control button is used to control the relevant parameters of the whole sampling process, and the display screen is used to display the smoke related parameters and test results.

The central processing unit is used to receive, control and store the data returned by each measuring device, and at the same time automatically calculate the concentration of SO ₃ in the flue gas. The central processing unit can preferably adopt a PLC controller.

The present invention also provides an online monitoring method for sulfur trioxide in flue gas, comprising:

(1) Continuously collect the flue gas to be tested through the flue gas sampling unit, and raise the temperature of the flue gas;

(2) After the temperature of the flue gas to be tested rises to 300-400°C, the air pump provides negative pressure to make the flue gas enter the serpentine condenser tube, and the SO ₃ in the flue gas in the serpentine condenser tube condenses into sulfuric acid droplets to remove SO ₃ The final flue gas enters the gas phase detection unit to record the gas phase flow rate;

(3) After the condensation is completed, the absorption liquid is passed into the serpentine condenser tube, and mixed with the sulfuric acid droplets to form a liquid-phase mixed liquid, which enters the liquid-phase detection unit and reacts with the barium salt solution to detect The mass of _SO3 that has been converted in the liquid phase;

(4) Receive the detection results of the gas phase detection unit and the liquid phase detection unit through the digital control unit, and calculate the concentration of SO ₃ in the flue gas.

Preferably, the temperature of the serpentine condenser is 60-80°C. This temperature is lower than the sulfuric acid dew point, and the _SO3 in the flue gas condenses into sulfuric acid droplets, which are separated from the flue gas.

Preferably, the absorption liquid is an aqueous solution of isopropanol or water.

Beneficial effects of the present invention:

The present invention realizes the on-line measurement of _SO3 in the flue gas, and has the characteristics of simple structure and portability. It can sample the _SO3 in the flue gas and analyze the content of _SO3 , which is convenient for coal-fired power plants to take corresponding measures. Control the SO ₃ content in the flue gas, reduce the corrosion of the flue and its equipment, and at the same time minimize the heat loss of the boiler exhaust, with the advantages of short measurement time and full process automation.

Description of drawings

Fig. 1 is the overall structural representation of the present invention;

Fig. 2 is a schematic structural diagram of the flue gas collection unit of the present invention;

Fig. 3 is the schematic diagram of _SO detection unit of the present invention;

Fig. 4 is the structural representation of digital control unit of the present invention;

Fig. 5 is a schematic diagram of the installation of the detection device of the present invention in the flue gas treatment system.

Detailed ways

Below in conjunction with accompanying drawing and embodiment the present invention will be further described:

As shown in Figure 1, 100 in the figure is the flue gas collection unit, 200 is the SO ₃ detection unit, 300 is the digital control unit, and the system is composed of these three parts.

As shown in FIG. 2 , the smoke collection unit 100 includes a smoke sampling gun head 105 , a filter chamber 101 and a sampling gun connected in sequence.

The sampling gun has an inner and outer double-layer structure, and the inner layer is a flue gas sampling pipe 102, which is a steel pipe made of antirust material. A heating device 103 is arranged outside the flue gas sampling pipe 102. In this embodiment, the heating device is a winding The electric heating device outside the flue gas sampling pipe 102 is provided with a thermal insulation outer layer 104 outside the heating device, and the thermal insulation outer layer 104 is made of thermal insulation material. The heating device 103 and the thermal insulation outer layer 104 work together to keep the flue gas temperature in the flue gas sampling pipe 102 at 300-400°C. The tail of the flue gas sampling pipe 102 communicates with the SO ₃ detection unit.

The flue gas sampling pipe 102 is threadedly connected to the filter chamber 101 and is detachable. The filter chamber is filled with quartz wool, which is replaceable and is used to filter the dust particles in the flue gas.

A temperature acquisition device, such as a temperature sensor, is provided at the outlet of the flue gas sampling pipe 102 to detect the temperature of the flue gas at the outlet and transmit it to the digital control unit.

As shown in Figure 3, _the flue gas collection unit 100 is connected with the _SO detection unit 200 through a pipeline, and the gas-liquid separator in the SO detection unit 200 of the present embodiment is two parallel serpentine condensation pipes (the first snake Condenser pipe 202 and second serpentine condenser pipe 201), the two serpentine condenser pipes are installed in the thermostatic chamber 215, the entrances of the two serpentine condenser pipes pass through the three-way pipe and the corresponding valve and the tail of the flue gas sampling pipe 102 The outlet is connected to the first solution tank 212, and the outlets of the two serpentine condensing pipes are connected to the gas phase pipeline and the liquid phase pipeline with the corresponding valve through the tee pipe. When the serpentine condensing pipe is used as the gas-liquid separator, the serpentine condensing pipe The outlet of the condenser tube is both a gas phase outlet and a liquid phase outlet, controlled by corresponding valves.

For the first serpentine condenser pipe 202, the connection between the inlet and the flue gas sampling pipe 102 and the first solution tank 212 is controlled by the valve V6 and the valve V3, and the connection between the outlet and the gas phase line and the liquid phase line is controlled by the valve V8 and the valve V9 For the second serpentine condenser tube 201, the connection between the inlet and the flue gas sampling pipe 102 and the first solution tank 212 is controlled by the valve V5 and the valve V4, and the outlet and the gas phase pipeline are controlled by the valve V11 and the valve V10 and liquid line connections.

A pipeline is also connected in parallel between the gas phase pipeline and the flue gas sampling pipe 102 , and a valve V7 is arranged on the pipeline for pumping and testing the gas phase pipeline before sampling.

In order to facilitate the elimination of the liquid phase in the serpentine condensing tube, a second air pump 214 is also provided, and the second air pump 214 is connected to the inlets of the two serpentine condensing tubes respectively through a three-way pipe and a valve, wherein the second air pump is controlled by the valve V1 214 is connected to the inlet of the first serpentine condenser 202 , and the valve V2 controls the connection between the second air pump 214 and the second serpentine condenser 201 .

A first gas pump 203, a control valve V13, and a gas phase detection unit 204 are sequentially arranged along the gas phase pipeline, and the gas phase detection unit 204 includes a flowmeter, a thermometer and a barometer; a reactor 206 is connected to the outlet of the liquid phase pipeline, and the reactor 206 also has a The inlet is connected to the liquid pump 210 and the second solution tank 211 in turn. The bottom of the reactor 206 is a magnetic stirrer 207. There is a stirrer 208 in the reactor 206. A light source 205 is arranged on one side of the reactor 206, and a light source 205 is installed on the other side of the reactor. A photometer 209 is provided, by which light transmitted through the reactor 206 is absorbed and sent to the digital control unit 300 . A discharge pipeline is provided at the bottom of the reactor 206, and a valve V12 is provided on the discharge pipeline.

SO _Detecting unit 200 also includes a first solution tank 212, the first solution tank 212 is connected with the inlet to a serpentine condenser through a three-way pipeline and a valve, between the first solution tank 212 and the corresponding serpentine condenser A water pump 213 is set on the pipeline, and the water pump 213 pumps the absorption liquid in the first solution tank 212 into the corresponding serpentine condenser; the pipeline corresponding to the serpentine condenser and the first solution tank 212 is provided with a second air pump 214 and its corresponding control valve.

All the above components are connected by pipelines.

As shown in FIG. 4 , the digital control unit 300 is composed of a housing and a central processing unit 304 , and the housing includes a display screen 302 , control buttons 303 and an outer box 301 . Wherein the display screen 302 is used to display the results of measuring SO ₃ , the control button 303 is used to control the start and end of the measurement and some parameters; the central processing unit 304 is used to control the switches of the liquid pump, two air pumps and a series of valves, accept For the parameters of the collection device, the central processing unit 304 is connected with each device (temperature collection device; flowmeter, thermometer and barometer in the gas phase detection unit; photometer; and various valves) by line communication. The central processing unit 304 receives the gas flow and the SO ₄ ^2- signal in the liquid, and obtains the SO ₃ reading in the flue gas through processing, and displays it on the digital display.

The working process of the device of the present invention is as follows:

All valves were closed before sampling. When sampling starts, open the valve V7, and the heating device of the sampling gun starts to heat. After the temperature is heated to 300-400°C, close the valve V7, open the valves V6 and V8, and keep the flue gas temperature in the sampling gun during the collection process. The temperature is 300-400°C, and the flue gas to be tested enters the flue gas sampling pipe 102 after being filtered by the filter chamber 101 .

After the flue gas comes out of the flue gas sampling pipe, it enters the first serpentine condenser pipe 202 in the constant temperature chamber (the temperature of the constant temperature chamber is 60-80° C.), and the SO ₃ in the flue gas is condensed into sulfuric acid droplets. The first air pump 203 behind the first serpentine condensing tube 202 is used to provide negative pressure, so that the gas is extracted from the first serpentine condensing tube 202, and the control valve V13 is used to control the gas flow, which is used for the flow meter in the gas phase detection unit 204 For measuring the gas flow, the flow meter feeds back the measured flow information to the digital control unit 300 for calculation of the SO ₃ content in the flue gas.

Generally, the sampling time of a serpentine tube is 5 minutes, the sampling time must be more than 3 minutes, and the flow rate is 1-3L/min. After the sampling of the first serpentine condenser tube 202 is completed, the valve V6 and the valve V8 are closed, and the valve V5 and the valve V11 are closed at the same time. Open and switch to the second serpentine condenser 201 , at this time the reading of the flowmeter is fed back to the digital control unit 300 . The work of the second serpentine condenser 201 and the pipeline behind it is the same as that of the first serpentine condenser 202, and the serpentine condenser starts sampling.

After switching to the second serpentine condenser pipe 201, the valve V3 and valve V9 are opened, and the water pump 213 pumps the absorption liquid in the first solution tank 212 into the first serpentine condenser pipe 202. The flow rate of the water pump 213 can be set, generally 1- 2ml/s, the water pump 213 is turned on for 30s, the liquid added to the first serpentine condenser 202 can be controlled, and the flow is fed back to the digital control unit for calculation of the _SO3 concentration.

After the opening time of the liquid pump is closed, the valve V1 is opened, the second air pump 214 starts to work, and all the liquid in the first serpentine condenser 202 is pressed into the reactor 206 in the liquid phase detection device by high-pressure air, and the second air pump 214 is turned on The time is generally 30s. After the end, the valve V1 and the valve V9 are closed, and the liquid pump 210 starts to work, and the liquid in the second solution tank 211 is pressed into the reactor 206. The flow rate of the liquid pump 210 can be set, generally 1-2ml/s, The opening time of the liquid pump 210 is 30s, and the liquid added to the reactor 206 can be controlled, and the flow rate is fed back to the digital control unit for calculating the SO ₃ concentration.

When the liquid pump 210 starts to work, the magnetic stirrer starts to stir, and the stirring time is 40s. After the stirring is completed, the light source 205 emits a light wave with a light wave of 500-600nm. The light intensity is received and measured, and fed back to the digital control unit 300 . After obtaining the light intensity signal, the valve V12 at the bottom of the reactor 206 is opened to discharge the waste liquid, and the valve V12 is opened for 10 seconds and then closed.

The central processing unit 304 of the digital control unit 300 receives the parameters of the liquid pump 210, the water pump 213, the photometer 209, and the flow meter, obtains the reading of SO ₃ in the flue gas through processing, and displays it on the digital display.

This is the end of one measurement, and the next measurement is that after the sampling time of the second serpentine condenser 201 ends, the valve V5 and valve V11 are closed, the valve V6 and valve V8 are opened, and the sampling is switched to the first serpentine condenser 202, and the second serpentine condenser The measurement method of sulfuric acid droplets in the serpentine condenser tube 201 is the same as that of the first serpentine condenser tube 202, except that the control valves are different, and the corresponding valves are valve V2, valve V4 and valve V10.

The operating principle of the device of the present invention is as follows:

After the dust is removed from the filter chamber 101, the flue gas passes through the flue gas sampling pipe 102 and enters the corresponding serpentine condenser pipe. The temperature of the serpentine condenser is 60-80°C, which is lower than the dew point of sulfuric acid, so it condenses in the serpentine condenser. The sulfuric acid droplets in the serpentine condensing tube are mixed with the absorption liquid delivered by the water pump 213 and then enter the reactor. After the liquid enters the reactor, it reacts with the reactants in the second solution tank to generate precipitates or colored ions, and the precipitates or colored ions are equal to or proportional to the concentration of sulfate ions, that is, the concentration of sulfur trioxide Concentrations are equal or proportional, then measure the ion concentration, you can measure the SO ₃ content. Colored ions have specific absorption peaks of light waves (such as chloranic acid ions can absorb light waves with a wavelength of 535nm), and the ion concentration can be measured by optical methods to obtain the concentration of sulfur trioxide in the sampled flue gas.

Example 1

The _SO3 concentration in the flue gas before denitrification of a certain power plant is detected by using the device and measuring method of the present invention. The arrangement of measuring points for the denitrification SCR system of a certain power plant is shown in Figure 5. The measuring points for the entrance of the SCR system are arranged on the horizontal flue (position 401) at the entrance of the economizer 400, and the measuring holes are evenly distributed. Before the test, replace the quartz wool in the filter chamber 101, fill the first solution tank 212 with an aqueous solution with an isopropanol concentration of 80%, fill the second solution tank ₂₁₁ with thorium reagent and BaCl solution, and the wavelength of the light source is 530nm. The average concentration of SO ₃ in this position of the power plant is detected to be 14.6mg/m ³ under this working condition, and the concentration of SO ₃ in the flue gas is 14.4 mg/m 3 measured by the method in "Performance Test Method for Coal-fired Flue Gas Desulfurization Equipment—GB/T21508-2008" mg/m ³ .

Example 2

The _SO3 concentration in the flue gas after denitrification of a power plant is detected by using the device and the measuring method of the present invention. The arrangement of measuring points for the denitrification SCR system of a certain power plant is shown in Figure 5. The measuring points at the outlet of the SCR system are arranged on the horizontal flue at the outlet of the economizer 400 (position 402), and the measuring holes are evenly distributed. Before the test, replace the quartz wool in the filter chamber 101. In the first solution tank 212, it is the aqueous solution of 80% that isopropanol concentration is loaded into, and the solution of thorium reagent and _BaCl is loaded into the second solution tank 211, and the wavelength of the light source is 530nm, and it is detected that this position of the power plant SO ₃ This working condition The lower average concentration is 42.1mg/m ³ , and the SO ₃ concentration in the flue gas is 42.2mg/m ³ measured by the method in "Performance Test Method for Coal-fired Flue Gas Desulfurization Equipment—GB/T21508-2008".

Claims (10)

1. An online detection device for sulfur trioxide in flue gas, comprising a flue gas sampling unit, characterized in that it also includes: A gas-liquid separator for condensing _SO3 in the flue gas from the flue gas sampling unit into sulfuric acid droplets for separation from the gas phase; a gas phase detection unit, used to measure the gas phase flow from the gas-liquid separator; The first solution tank is used to provide absorption liquid to the gas-liquid separator to mix the sulfuric acid droplets to form a mixed liquid; A liquid phase detection unit for measuring the _converted SO in the mixed liquid from the gas-liquid separator Quality; The digital control unit is used to calculate the concentration of SO ₃ in the flue gas according to the detection results of the gas phase detection unit and the liquid phase detection unit. 2. The on-line detection device of sulfur trioxide in the flue gas according to claim 1, characterized in that, the gas-liquid separator is a plurality of serpentine condensation pipes connected in parallel, and the entrance of the serpentine condensation pipe passes through the corresponding The pipes and valves are connected with the flue gas sampling unit and the first solution tank, and the outlet of the serpentine condenser is connected with the gas phase detection unit and the liquid phase detection unit through corresponding pipes and valves. 3. The on-line detection device for sulfur trioxide in flue gas according to claim 2, characterized in that an air pump is provided between the gas phase detection unit and the outlet of the corresponding serpentine condensation pipe for condensing the serpentine The gas in the tube is pumped into the gas phase detection unit. 4. according to the online detection device of sulfur trioxide in the described flue gas of claim 3, it is characterized in that, described liquid phase detection unit comprises: A reactor communicated with the outlet of the serpentine condenser; A second air pump connected to the inlet of the serpentine condenser, used to hydraulically inject the mixture in the serpentine condenser into the reactor; a light source for emitting detection light to the reactor; A photometer for receiving transmitted light through the reactor, the photometer being communicatively connected to the digital control unit. 5. according to the online detection device of sulfur trioxide in the described flue gas of claim 4, it is characterized in that, also be provided with the second solution tank that communicates with described reactor by liquid pump, described reactor has magnetic stirring device. 6. The on-line detection device for sulfur trioxide in the flue gas according to any one of claims 1 to 5, wherein the flue gas sampling unit comprises a flue gas sampling gun head, a filter chamber and a flue gas sampling unit connected in sequence. A sampling pipe, the tail end of the flue gas sampling pipe communicates with the gas-liquid separator, and a filtering device is arranged in the filtering chamber. 7. The on-line detection device for sulfur trioxide in the flue gas according to claim 6, characterized in that, the flue gas sampling pipe is provided with a heating device for maintaining the temperature in the flue gas sampling pipe, and the heating device is provided with a Insulated outer layer. 8 . The on-line detection device for sulfur trioxide in flue gas according to claim 6 , wherein a temperature acquisition device is provided outside the flue gas sampling pipe, and the temperature acquisition device is connected to the digital control unit by communication. 9. An online monitoring method for sulfur trioxide in flue gas, characterized in that, comprising: (1) Continuously collect the flue gas to be tested through the flue gas sampling unit, and raise the temperature of the flue gas; (2) After the temperature of the flue gas to be tested rises to 300-400°C, the air pump provides negative pressure to make the flue gas enter the serpentine condenser tube, and the SO ₃ in the flue gas in the serpentine condenser tube condenses into sulfuric acid droplets to remove SO ₃ The final flue gas enters the gas phase detection unit to record the gas phase flow rate; (3) After the condensation is completed, the absorption liquid is passed into the serpentine condenser tube, and mixed with the sulfuric acid droplets to form a liquid-phase mixed liquid, which enters the liquid-phase detection unit and reacts with the barium salt solution to detect The mass of _SO3 that has been converted in the liquid phase; (4) Receive the detection results of the gas phase detection unit and the liquid phase detection unit through the digital control unit, and calculate the concentration of SO ₃ in the flue gas. 10. The method according to claim 9, characterized in that the temperature of the serpentine condenser is 60-80°C.

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