CN103076215B - Bubbling type ultrasonic atomized mercury valence transformation device and method - Google Patents

Abstract

The invention discloses a bubbling ultrasonic atomization mercury valence conversion device and a conversion method, which efficiently convert oxidized mercury that is difficult to measure in coal-fired smoke into elemental mercury that is easy to measure. The device of the present invention uses a bubbling reactor to process the flue gas extracted on site to generate a large number of micron-scale air bubbles; at the same time, it uses ultrasonic atomization technology to process the stannous chloride hydrochloric acid solution to form a large number of micron-scale droplets . The combination of the two can greatly increase the contact area between the sample gas and the tin protochloride hydrochloric acid solution. At the same time, a baffle is set to prolong the interaction time between the sample gas and the stannous chloride hydrochloric acid solution. The invention can maximize the efficiency of stannous chloride wet chemical method to convert oxidized mercury into elemental mercury, and realize the online continuous conversion of oxidized mercury into reduced mercury under laboratory and actual flue gas conditions. Real-time, comprehensive and accurate measurement of mercury speciation in the mode.

Description

Device and method for bubbling ultrasonic atomization mercury valence conversion

technical field

The invention belongs to the field of heavy metal mercury measurement, and relates to a device and method for efficiently converting oxidized mercury which is difficult to measure in coal-fired flue gas into easy-to-measure elemental mercury.

Background technique

Mercury and its compounds are receiving widespread attention as a class of toxic and harmful substances due to their high volatility, atmospheric migration, bioaccumulation, and nerve damage. With the increasing consumption of coal resources in the world, coal-fired power plants have become the world's largest single source of anthropogenic mercury emissions. The United States, Canada, China, etc. have formulated relevant laws, regulations or industry standards for mercury emissions from coal-fired power plants, and research on various technologies to control mercury emissions from coal-fired power plants, such as adding removers to coal, activated carbon adsorbent tail flue injection, The use of existing desulfurization, denitrification and dust removal devices is also in full swing.

Whether it is to establish a relatively accurate mercury emission inventory or evaluate the efficiency of various mercury capture technologies, the realization of comprehensive and accurate mercury measurement is undoubtedly an important prerequisite and basis. Mercury and its compounds involved in coal-fired power plants mainly include three forms: gaseous elemental mercury, gaseous oxidized mercury, and particulate mercury. Particulate mercury includes mercury in bottom slag and fly ash, which can generally be sampled in accordance with strict standard methods for laboratory analysis. The measurement of gaseous mercury in flue gas is divided into two categories. One is to conduct on-site sampling and analysis in accordance with the standard method Ontario-HydroMethod (OHM) recommended by the US Environmental Protection Agency and the Department of Energy, which can effectively collect and analyze coal-fired mercury. Different forms of mercury and its compounds in flue gas; the second is based on online analysis technology, using the principle of cold vapor atomic absorption method (CVAAS) or cold vapor atomic fluorescence method (CVAFS) to detect the concentration of mercury in flue gas online in real time. However, the current on-line analysis and detection technologies for mercury concentration are all based on the method of detecting elemental mercury, that is, only elemental mercury can be detected but oxidized mercury cannot be detected. Therefore, in order to detect oxidized mercury, the conversion of oxidized mercury to elemental mercury must be carried out first. The usual practice is to install a mercury valence conversion device in front of the detection instrument to convert the oxidized mercury into elemental mercury and then detect the total mercury content in the flue gas, and finally obtain it indirectly through the difference between the total mercury content and the elemental mercury content Oxidized mercury content.

Due to the unique advantages of simple measurement process and real-time reflection of measurement results, the on-line detection and analysis technology of mercury in coal-fired flue gas has become a research hotspot in this field all over the world. Among them, the valence conversion device with high conversion efficiency has become the core component to realize the simultaneous real-time online monitoring of gaseous elemental mercury and gaseous oxidized mercury. At present, there are mainly two kinds of valence conversion devices for mercury. One is to use stannous chloride solution for wet chemical conversion to reduce oxidized mercury to elemental mercury; the other is to convert various oxidized mercury into elemental mercury at high temperature. The compound is thermally decomposed and converted into elemental total mercury. The conversion efficiency of the high-temperature heating method depends on the choice of temperature and the purge of inert gas. Recently, the conversion temperature has been controversial, and the additional energy loss and the use of inert gas have also increased the complexity and cost of its use. The stannous chloride wet chemical method can be carried out at room temperature, but the limitation of its utilization lies in the low conversion efficiency. How to achieve the required conversion efficiency within a limited time and space has become the key to the application of this method in industrial devices.

Contents of the invention

Technical problem: In view of the low conversion efficiency of oxidized mercury to elemental mercury in the stannous chloride wet chemical method, the present invention provides a method that can significantly improve the conversion efficiency of oxidized mercury to elemental mercury and simultaneously detect in real time A bubbling ultrasonic atomization mercury valence conversion device for elemental mercury and oxidized mercury. The invention also provides a method for utilizing the device to efficiently convert mercury valence states.

Technical solution: The bubbling ultrasonic atomization mercury valence conversion device of the present invention includes an air inlet chamber, an air distribution plate, a bubbling reaction section, an atomization reaction section, a cooling water jacket, and The extension reaction and solution recovery section and the external air guide pipeline, the side of the air inlet chamber is equipped with an air inlet, the ultrasonic atomization sheet is embedded in the air distribution plate, and the cooling heat exchange tube is installed in the bubbling reaction section, and the cooling heat exchange tube The cooling water jacket is connected with the cooling water jacket through the pipeline. The cooling water jacket is provided with a cooling water inlet and a cooling water outlet. In the extension reaction and solution recovery section, 4~6 baffles are arranged in a staggered order from bottom to top. A quartz fiber water filter core impregnated with sodium hydroxide solution is arranged in the air pipeline.

In the device of the present invention, the air inlet chamber, the main body of each reaction section, the cooling water jacket and the external air guide pipeline are all made of polytetrafluoroethylene material that does not absorb mercury, and the cooling heat exchange tube and the connecting pipeline between the cooling water jacket High borosilicate glass material that does not absorb mercury is used.

The air distribution plate in the device of the present invention is made of quartz material that does not absorb mercury, and is densely covered with small holes with an aperture ranging from 1 to 10 microns. A large number of micron-sized holes densely covered on it can allow the sample gas to enter the bubbling reaction section smoothly from the air inlet chamber, and at the same time ensure that the contained stannous chloride hydrochloric acid solution will not leak.

The present invention utilizes the above-mentioned bubbling type ultrasonic atomization mercury valence conversion device to carry out the method for mercury valence conversion, comprising the following steps:

1) The sample gas mixed with elemental mercury and oxidized mercury is passed into the air inlet chamber through the air inlet, and evenly enters the bubbling reaction section after passing through the air distribution plate to react with the stannous chloride hydrochloric acid solution;

2) A large number of stannous chloride hydrochloric acid droplets generated by the vibration of the ultrasonic atomization sheet flood the entire atomization reaction section, and the sample gas further fully contacts with the stannous chloride hydrochloric acid droplets to undergo a reduction reaction;

3) After the two-step reaction, the sample gas enters the extension reaction and solution recovery section through the central hole of the cooling water jacket, and blocks the channel formed in the extension reaction and solution recovery section along the baffle. The sample gas and stannous chloride The hydrochloric acid droplets continue to interact, and the stannous chloride hydrochloric acid droplets gradually condense and reunite on the surface of the baffle plate along the sample gas flow and fall back into the bubbling reaction section;

4) The fully reduced sample gas and a very small amount of stannous chloride hydrochloric acid droplets are discharged into the external gas-conducting pipeline, flow through the quartz fiber water filter element impregnated with sodium hydroxide solution, and are discharged from the exhaust port to enter the elemental state Mercury analyzer for analysis and measurement.

The principle of enhancing the conversion efficiency of oxidized mercury to elemental mercury is: the bubble reactor processes the sample gas to generate a large number of micron-sized bubbles, which greatly increases the contact area between the sample gas and the stannous chloride hydrochloric acid solution; Ultrasonic atomization technology treats the stannous chloride hydrochloric acid solution to form a large number of micron-sized droplets, which further increases the contact area between the sample gas and the stannous chloride hydrochloric acid droplets; in addition, the diversion and disturbance of the baffle It can also prolong the interaction time between sample gas and stannous chloride hydrochloric acid droplets. Therefore, the conversion efficiency of oxidized mercury to elemental mercury is greatly improved.

Beneficial effects: A bubbling ultrasonic atomization mercury valence conversion device proposed by the present invention has the following characteristics and advantages:

(1) Using the principle of the bubble reactor, the contact area between the sample gas and the stannous chloride hydrochloric acid solution is increased, which is conducive to improving the conversion efficiency of oxidized mercury to elemental mercury;

(2) Using ultrasonic atomization technology, the contact area between sample gas and stannous chloride hydrochloric acid droplets is increased, which is conducive to improving the conversion efficiency of oxidized mercury to elemental mercury;

(3) The baffle structure prolongs the interaction time between the sample gas and the stannous chloride hydrochloric acid solution, and at the same time recovers the unreacted stannous chloride hydrochloric acid solution, which is conducive to improving the conversion efficiency of oxidized mercury to elemental mercury Also improve the utilization efficiency of stannous chloride hydrochloric acid solution simultaneously;

(4) The above-mentioned three are skillfully and properly connected to form a practical and efficient whole, and under the premise of ensuring efficient mercury conversion, the usage of stannous chloride hydrochloric acid solution is minimized and the energy consumption of the device is minimized;

(5) The bubbling ultrasonic atomization mercury valence conversion device of the present invention can be used in combination with various elemental mercury analyzers to detect elemental mercury and oxidized mercury in the sample gas under laboratory conditions; A sub-module of the on-site monitoring equipment for coal power stations converts oxidized mercury to elemental mercury to achieve comprehensive analysis and measurement of mercury valence.

The device of the present invention combines the principle of a bubbling chemical reactor and ultrasonic atomization technology to pretreat the mixed gas containing elemental mercury and oxidized mercury, which can significantly improve the conversion efficiency of oxidized mercury to elemental mercury. Simultaneous real-time online monitoring of elemental and oxidized mercury provides feasibility.

In the device of the present invention, the ultrasonic atomizing sheet forms stannous chloride hydrochloric acid droplets of about 50 microns in the atomizing reaction section.

The invention combines the principle of bubbling bed reaction and ultrasonic atomization technology to increase the contact area and reaction time between the sample gas and the reaction solution, and improve the conversion efficiency of oxidized mercury to elemental mercury.

Description of drawings

Figure 1 is a structural system diagram of the patented bubbling ultrasonic atomization mercury valence conversion device of the present invention.

In the figure there are: 1 air intake chamber, 2 air distribution plate, 3 bubbling reaction section, 4 atomization reaction section, 5 cooling water jacket, 6 extension reaction and solution recovery section, 7 external air guide pipeline, 1-1 Air inlet, 2-1 ultrasonic atomizing sheet, 3-1 cooling heat exchange tube, 5-1 cooling water inlet, 5-2 cooling water outlet, 6-1 baffle plate, 7-1 quartz fiber water filter element, 7 -2 exhaust ports.

Detailed ways

The technical solution of the present invention will be described in detail below in conjunction with the drawings and examples in the description.

The bubbling ultrasonic atomization mercury valence conversion device of the present invention comprises an air inlet chamber 1, an air distribution plate 2, a bubbling reaction section 3, an atomization reaction section 4, and a cooling water jacket which are sequentially connected from bottom to top 5. The extension reaction and solution recovery section 6 and the external air guide line 7, the air inlet chamber 1 side is provided with an air inlet 1-1, the air distribution plate 2 is embedded with an ultrasonic atomizing sheet 2-1, and the bubbling reaction section 3 is provided with a cooling heat exchange tube 3-1, the cooling heat exchange tube 3-1 is connected to the cooling water jacket 5 through a pipeline, and the cooling water jacket 5 is provided with a cooling water inlet 5-1 and a cooling water outlet 5- 2. There are two independent hollow water storage chambers inside the cooling water jacket 5, which are separated by partitions. One water storage chamber is connected to the cooling water inlet 5-1, and the bottom is connected to the inlet pipe of the cooling heat exchange tube 3-1. A water storage chamber communicates with the cooling water outlet 5-2, and the bottom is connected to the outlet pipeline of the cooling heat exchange tube 3-1 to form a cooling water flow path. The extended reaction and solution recovery section 6 is provided with staggered arrangements from bottom to top. There are 6 baffles 6-1, and a quartz fiber water filter element 7-1 impregnated with sodium hydroxide solution is arranged in the external air guiding pipeline 7. In the device of the present invention, the intake air chamber 1, the main body of each reaction section, the cooling water jacket 5 and the external air guide pipeline 7 are all made of polytetrafluoroethylene material that does not absorb mercury, and the cooling heat exchange tube 3-1 and its connection with the cooling The connecting pipes between the 5 water jackets are made of high borosilicate glass material that does not absorb mercury. The air distribution plate 2 in the device of the present invention is made of quartz material that does not absorb mercury, and is densely covered with small holes with an aperture ranging from 1 to 10 microns. A large number of micron-sized holes densely covered on it can allow the sample gas to enter the bubbling reaction section 3 smoothly from the air inlet chamber 1, and at the same time ensure that the contained stannous chloride hydrochloric acid solution does not leak.

Before using the device of the present invention alone or in combination with an elemental mercury analyzer, it is necessary to pre-soak the part of the device that touches the sample gas with nitric acid with a mass fraction of 10% for 12 to 24 hours, and then rinse it with deionized water to ensure the measurement There is no adsorption loss effect on mercury in the process.

Prepare a 10% mass fraction of stannous chloride hydrochloric acid solution: dissolve 100 grams of stannous chloride in a volume fraction of 100 ml of 10% hydrochloric acid, and dilute to 1000 ml with a volume fraction of 10% hydrochloric acid.

Slowly inject the prepared stannous chloride hydrochloric acid solution into the bubbling reaction section 3 of the device. The dosage depends on the volume flow rate of the sample gas and the estimated mercury concentration in the sample gas. No more than 10 cm. Start the ultrasonic atomizing sheet 2-1, which is driven by a 12 volt DC voltage. After the atomization reaction section 4 is filled with stannous chloride hydrochloric acid droplets, the required measurement sample gas can be connected to convert and measure the mercury valence state.

The sample gas mixed with elemental mercury and oxidized mercury enters the air intake chamber 1 from the air inlet 1-1. Since the air distribution plate 2 is a densely porous plate, the pressure drop is large, and the gas distribution after the sample gas passes through the air distribution plate 2 relatively uniform.

The air distribution plate 2 is made of sintered quartz material that does not absorb mercury, with a pore size of 1-10 microns, allowing the sample gas to enter the bubbling reaction section 3 from the air inlet chamber 1 . The micron-sized dense holes can make the sample gas generate a large number of micron-sized dense bubbles when passing through, so that the contact area between the sample gas and the stannous chloride hydrochloric acid solution can be greatly increased, and at the same time, the stannous chloride contained can be guaranteed Hydrochloric acid solution will not leak. A certain number of ultrasonic atomizing sheets 2-1 are embedded on the air distribution plate 2 depending on the specific mercury load. Since the stannous chloride hydrochloric acid solution is highly corrosive, the upper surface of the ultrasonic atomizing sheet 2-1 and the air distribution plate The joints of board 2 are all coated with a thin anti-corrosion layer.

The mercury-loaded sample gas entering the bubbling reaction section 3 passes through the air distribution plate 2 to generate a large number of bubbles, fully contacts with the stannous chloride hydrochloric acid solution on the air distribution plate 2, and a reduction reaction occurs, and the initially converted sample gas escapes from the solution , into the atomization reaction section 4. A large number of stannous chloride hydrochloric acid mist droplets generated by ultrasonic vibration flood the entire atomization reaction section 4, and the diameter of the mist droplets is about 50 microns. The sample gas is further fully contacted with the stannous chloride hydrochloric acid droplets to continue the reduction reaction, and the further converted sample gas enters the extension reaction and solution recovery section 6 through the central hole of the cooling water jacket 5 .

Since the ultrasonic vibration atomization will generate a lot of heat, the cooling water system is designed for the cooling of the stannous chloride hydrochloric acid solution to ensure that the temperature of the stannous chloride hydrochloric acid solution maintains the normal reaction temperature. The cooling water system is composed of a cooling water jacket 5, a cooling water inlet 5-1, a cooling water outlet 5-2, and cooling heat exchange tubes 3-1. The interior of the cooling water jacket 5 is designed as two independent hollow water storage chambers, separated by a partition in the middle, and the cooling water with a certain flow rate enters the first water storage chamber from the cooling water inlet 5-1, and flows through the cooling heat exchange chamber. Pipe 3-1 enters another water storage cavity, and finally gets rid of by cooling water outlet 5-2. The cooling water jacket 5 and the atomization reaction section 4 and the extension reaction and solution recovery section 6 can be threaded or flanged to ensure airtightness.

The sample gas entering the extended reaction and solution recovery section 6 continues to interact with a small amount of rising stannous chloride hydrochloric acid droplets, and under the diversion and disturbance of the baffle plate 6-1, the two continue to undergo a reduction reaction, and at the same time The stannous chloride hydrochloric acid droplets gradually condense and reunite on the surface of the baffle plate 6-1, and after reaching a certain level, fall back along the baffle plate 6-1 into the bubbling reaction section 3, and the cycle repeats.

The fully reduced sample gas and a very small amount of stannous chloride hydrochloric acid mist are discharged and enter the external air guide line 7. Some elemental mercury analysis instruments have requirements for the moisture content of the analyzed sample gas, so the external air guide tube is designed A quartz fiber water filter element 7-1 is added to the road 7, which can ensure the dehumidification effect under the condition of no mercury adsorption loss. The quartz fiber water filter element 7-1 can be impregnated with sodium hydroxide solution in advance to remove possible volatilized hydrogen chloride gas. Finally, the dry and completely reduced sample gas is discharged from the exhaust port 7-2, and enters the elemental mercury analyzer for analysis and measurement.

After using the device of the present invention for each measurement, the residual stannous chloride hydrochloric acid solution needs to be disposed of in time, and the air inlet 1-1, each reaction section and the external air guiding pipeline 7 should be moistened and washed with deionized water.

Claims (4)

1. a bubble type ultrasonic atomization mercury valence transformation device, it is characterized in that, this device comprises the air inlet air compartment (1) connecting setting from bottom to up successively, air distribution plate (2), blistering reaction section (3), atomization conversion zone (4), cooling water jecket (5), extension and solution exhausting section (6) and external gas-guide pipeline (7), described air inlet air compartment (1) side is provided with air inlet (1-1), the upper embedded ultrasonic atomization sheet (2-1) of described air distribution plate (2), cooling heat transferring pipe (3-1) is provided with in described blistering reaction section (3), described cooling heat transferring pipe (3-1) is connected with cooling water jecket (5) by pipeline, described cooling water jecket (5) is provided with cooling water inlet (5-1) and coolant outlet (5-2), in described extension and solution exhausting section (6), 4 ~ 6 baffles (6-1) be staggeredly arranged successively are from bottom to up set, the quartz fibre drainage core (7-1) of dipping sodium hydroxide solution is provided with in described external gas-guide pipeline (7), blistering reaction section (3) is contained with tin chloride solution.

2. bubble type ultrasonic atomization mercury valence transformation device according to claim 1, it is characterized in that, described air inlet air compartment (1), each conversion zone main body, cooling water jecket (5) and external gas-guide pipeline (7) all adopt the polytetrafluoroethylmaterial material of not Adsorption of Mercury, described cooling heat transferring pipe (3-1) and and cooling water jecket (5) between connecting line adopt the high-boron-silicon glass material of not Adsorption of Mercury.

3. bubble type ultrasonic atomization mercury valence transformation device according to claim 1, is characterized in that: described air distribution plate (2) adopts the quartz material of not Adsorption of Mercury, and densely covered pore diameter range is the aperture of 1 ~ 10 micron.

4. utilize bubble type ultrasonic atomization mercury valence transformation device described in claim 1 to carry out a method for mercury valence state conversion, it is characterized in that, the method comprises the steps:

1) the sample gas being mixed with elemental mercury and oxidation state mercury is passed into air inlet air compartment (1) by air inlet (1-1), after air distribution plate (2), evenly enter blistering reaction section (3) react with tin chloride solution;

2) shake by ultrasonic atomization sheet (2-1) a large amount of stannous chloride hydrochloric acid droplets produced and be full of whole atomization conversion zone (4), sample gas fully contacts with stannous chloride hydrochloric acid droplet further, and reduction reaction occurs;

3) sample gas enters extension and solution exhausting section (6) by the center pit of cooling water jecket (5) after this two-step reaction, in extension and solution exhausting section (6), the passage formed is intercepted along baffle (6-1), sample gas and stannous chloride hydrochloric acid droplet continue to interact, and stannous chloride hydrochloric acid droplet progressively condenses along sample air-flow journey simultaneously and reunites on baffle (6-1) surface and fall after rise in blistering reaction section (3);

4) obtain fully the sample gas of reduction and the stannous chloride hydrochloric acid droplet of minute quantity to discharge and enter external gas-guide pipeline (7), flow through sodium hydroxide solution impregnated quartz fibre drainage core (7-1), discharged by exhausr port (7-2), enter elemental mercury analyser and carry out analyzing and measuring.