A system for generating elemental mercury and divalent mercury standard gas and a working method thereof

Abstract

The present invention discloses an elemental mercury and divalent mercury standard gas generation system and a working method thereof, belonging to the technical field of gaseous mercury monitoring and analysis. The first inlet of the siphon type three-way joint is connected to the low temperature end of the gradient evaporation chamber, and the high temperature end of the gradient evaporation chamber is connected to the three-way joint through the carrier gas pipeline, and the three-way joint is also connected to the second inlet and the preheater respectively; the preheater is connected to the flow valve, the flow valve is connected to the filter, and the filter is connected to the nitrogen gas storage device; the outlet is connected to two branches, the reduction reactor and the elemental mercury standard gas control valve are arranged on one branch, and the divalent mercury standard gas control valve is arranged on the other branch; the heating module is arranged outside the gradient evaporation chamber, the gradient evaporation chamber is connected to the liquid inlet device, the liquid inlet device is connected to the stop valve, the stop valve is connected to the pump, and the pump is connected to the mercuric chloride standard liquid storage device. The structural design is reasonable, and the stable output of the concentration of mercury standard gas of different valence states is realized, and the accuracy of the calibration of mercury and its compound detection equipment and related scientific experiments is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of gaseous mercury monitoring and analysis, and in particular relates to an elemental mercury and divalent mercury standard gas generation system and a working method thereof. Background Art

[0002] Mercury is a toxic heavy metal element. Its elemental state can migrate and transform globally. It stays in the atmosphere for 0.5 to 2 years, causing serious pollution to the ecological environment such as water, air and soil. In order to reduce mercury pollution and protect human health, people have carried out a lot of research on the emission, migration, transformation, sedimentation and control of mercury and its compounds.

[0003] In the laboratory research on mercury and its compounds, elemental mercury standard gas is generally produced by mercury permeation tubes. Although a constant temperature water bath is used to ensure the stability of elemental mercury release, there is still a 50% fluctuation in mercury mass concentration. In addition, mercury permeation tubes are expensive and there is a risk of leakage of highly toxic substances. At present, there are no permeation tubes that can generate divalent mercury standard gas at home and abroad. Some literature and patents have proposed methods of evaporating mercuric chloride solution to produce only divalent mercury vapor, but the related devices have the problem of silting of evaporated divalent mercury, resulting in a large fluctuation in the concentration of the generated divalent mercury vapor, and the evaporation of mercuric chloride solution can only produce one type of divalent mercury gas. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide an elemental mercury and divalent mercury standard gas generation system and a working method thereof, which has a reasonable structural design and is easy to operate, can achieve stable output of different valence mercury standard gas concentrations, has simple equipment, complete functions, is safe and reliable, and has good application prospects.

[0005] The present invention is achieved through the following technical solutions:

[0006] The invention discloses an elemental mercury and divalent mercury standard gas generation system, comprising a nitrogen gas storage device, a filter, a flow valve, a preheater, a tee, a siphon type tee joint, a gradient evaporation chamber, a heating module, a liquid inlet device, a mercuric chloride standard liquid storage device, a pump, a stop valve, a reduction reactor, an elemental mercury standard gas control valve and a divalent mercury standard gas control valve;

[0007] The siphon type three-way joint comprises a first inlet, a second inlet and an outlet; the first inlet is connected to the low temperature end of the gradient evaporation chamber, the high temperature end of the gradient evaporation chamber is connected to the three-way joint through a carrier gas pipeline, and the three-way joint is also connected to the second inlet and the preheater respectively; the preheater is connected to the flow valve, the flow valve is connected to the filter, and the filter is connected to the nitrogen gas storage device; the outlet is connected to two branches, the reduction reactor and the elemental mercury standard gas control valve are arranged on one branch, and the divalent mercury standard gas control valve is arranged on the other branch;

[0008] The heating module is arranged outside the gradient evaporation chamber, the liquid inlet device is arranged at the upper part of the low temperature end of the gradient evaporation chamber and is connected with the interior of the gradient evaporation chamber, the liquid inlet device is connected with the stop valve, the stop valve is connected with the pump, and the pump is connected with the mercuric chloride standard solution storage device.

[0009] Preferably, a Venturi tube structure is provided between the second inlet and the outlet of the siphon type three-way joint.

[0010] Preferably, the interior of the filter is filled with modified activated carbon.

[0011] Preferably, the siphon type three-way joint is a polytetrafluoroethylene joint.

[0012] Preferably, the inner cavity of the gradient evaporation chamber is arc-shaped.

[0013] Preferably, the heating module comprises several groups of ceramic heating plates, and each group of ceramic heating plates is respectively connected to a temperature control device.

[0014] Preferably, the liquid inlet device is a syringe pump.

[0015] Preferably, the pump is a peristaltic pump.

[0016] Preferably, the top of the reduction reactor is dome-shaped.

[0017] The working method of the elemental mercury and divalent mercury standard gas generation system disclosed in the present invention comprises:

[0018] Add mercuric chloride standard solution to the mercuric chloride standard solution storage device, and add stannous chloride solution to the reduction reactor; set the temperature of the heating module so that there is a temperature gradient between the high temperature end and the low temperature end of the gradient evaporation chamber; set the opening of the flow valve and the temperature of the preheater, and open the nitrogen gas storage device to purge the entire system;

[0019] Open the stop valve, start the pump and set the opening, and the mercuric chloride standard liquid enters the gradient evaporation chamber from the liquid inlet device and vaporizes to generate divalent mercury vapor; the nitrogen in the nitrogen storage device is purified by the filter, enters the preheater through the flow valve for preheating, and then enters the gradient evaporation chamber from the high-temperature end of the gradient evaporation chamber to be heated again, so that a temperature gradient is generated in the gradient evaporation chamber, and the divalent mercury vapor enters the siphon type three-way joint through the first inlet;

[0020] Another nitrogen gas enters the siphon type three-way joint from the second inlet, forming a negative pressure at the first inlet, so that a pressure gradient is generated in the gradient evaporation chamber; the divalent mercury vapor generated in the gradient evaporation chamber outputs divalent mercury standard gas from the outlet under the action of the temperature gradient and the pressure gradient; the divalent mercury standard gas control valve is opened, the elemental mercury standard gas control valve is closed, and the divalent mercury standard gas is output to the system;

[0021] Close the divalent mercury standard gas control valve, open the elemental mercury standard gas control valve, and the divalent mercury standard gas enters the reduction reactor to generate elemental mercury standard gas and then is output to the system.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] The present invention discloses a system for generating elemental mercury and divalent mercury standard gas. A mercuric chloride standard liquid generates divalent mercury vapor in a gradient evaporation chamber, and enters a siphon-type three-way joint under the action of a temperature gradient in the gradient evaporation chamber. The temperature gradient in the gradient evaporation chamber can prevent the divalent mercury vapor from accumulating and flowing back. After entering the siphon-type three-way joint, the divalent mercury vapor is output under the action of a pressure gradient. The pressure gradient can also prevent the divalent mercury vapor from accumulating and flowing back, and achieves continuous and stable output. Nitrogen is purified by a filter to prevent impurity gas from affecting the concentration of divalent mercury vapor; nitrogen is preheated by a preheater before entering the gradient evaporation chamber, which can prevent excessively low temperature from destroying the temperature gradient in the gradient evaporation chamber and affecting the continuous and stable output of divalent mercury vapor; the liquid inlet device is located on the sample gas output side to ensure the release rate of the mercury standard gas after gasification. The system has a reasonable structural design and complete functions. It can switch functions according to actual needs, and is safe and reliable, ensuring the accuracy of calibration of mercury and its compound detection equipment and related scientific experiments.

[0024] Furthermore, a Venturi tube structure is used between the second inlet and the outlet of the siphon type three-way joint, which produces a good pressure gradient effect and has a simple structure and is easy to install and maintain.

[0025] Furthermore, the interior of the filter is filled with modified activated carbon, which has a good nitrogen purification effect and low cost.

[0026] Furthermore, the siphon type three-way joint adopts a polytetrafluoroethylene joint to prevent the mercury standard gas from adhering and affecting the accuracy of the mercury standard gas.

[0027] Furthermore, the inner cavity of the gradient evaporation chamber is arc-shaped, which can make the divalent mercury vapor inside flow smoothly and prevent the divalent mercury vapor from accumulating in dead corners.

[0028] Furthermore, the heating module includes several groups of ceramic heating plates, which have good heating effect and long service life; each group of ceramic heating plates is respectively connected to a temperature control device, so as to independently control the temperature gradient inside the device.

[0029] Furthermore, the liquid inlet device adopts a syringe pump, which can achieve high-precision, smooth and pulsation-free transmission, making it easy to control the generation speed of the system.

[0030] Furthermore, the pump adopts a peristaltic pump, which has good sealing performance, is safe and pollution-free, has good stability, high precision, and is simple to install and maintain.

[0031] Furthermore, the top of the reduction reactor is arched to ensure the stability and continuity of the output of the mercury standard gas.

[0032] The working method of the elemental mercury and divalent mercury standard gas generation system disclosed in the present invention is simple to operate, safe and reliable, has low operation and maintenance costs, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0034] Figure 2 It is a structural schematic diagram of a siphon type three-way joint.

[0035] In the figure: 1 is a nitrogen gas storage device, 2 is a filter, 3 is a flow valve, 4 is a preheater, 5 is a tee, 6 is a siphon type tee joint, 6-1 is a first inlet, 6-2 is a second inlet, 6-3 is an outlet, 7 is a carrier gas pipeline, 8 is a gradient evaporation chamber, 9 is a heating module, 10 is a liquid inlet device, 11 is a mercuric chloride standard solution storage device, 12 is a pump, 13 is a stop valve, 14 is a reduction reactor, 15 is an elemental mercury standard gas control valve, and 16 is a divalent mercury standard gas control valve. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with the accompanying drawings, the contents of which are intended to explain the present invention rather than to limit it:

[0037] like Figure 1 , which is an elemental mercury and divalent mercury standard gas generation system of the present invention, includes a nitrogen gas storage device 1, a filter 2, a flow valve 3, a preheater 4, a tee 5, a siphon type tee joint 6, a gradient evaporation chamber 8, a heating module 9, a liquid inlet device 10, a mercuric chloride standard solution storage device 11, a pump 12, a stop valve 13, a reduction reactor 14, an elemental mercury standard gas control valve 15 and a divalent mercury standard gas control valve 16.

[0038] like Figure 2 The siphon type three-way joint 6 is made of polytetrafluoroethylene, and includes a first inlet 6-1, a second inlet 6-2 and an outlet 6-3. Preferably, a venturi tube structure is provided between the second inlet 6-2 and the outlet 6-3 of the siphon type three-way joint 6.

[0039] The gradient evaporation chamber 8 adopts a cylindrical structure, with spherical heads at both ends, and the inner cavity is an arc with no dead angle. The first inlet 6-1 is connected to the low-temperature end of the gradient evaporation chamber 8, and the high-temperature end of the gradient evaporation chamber 8 is connected to the tee 5 through the carrier gas pipeline 7, and the tee 5 is also connected to the second inlet 6-2 and the preheater 4 respectively; the preheater 4 is connected to the flow valve 3, the flow valve 3 is connected to the filter 2, the filter 2 is filled with modified activated carbon, and the filter 2 is connected to the nitrogen gas storage device 1; the outlet 6-3 is connected to two branches, the reduction reactor 14 and the elemental mercury standard gas control valve 15 are arranged on one branch, and the divalent mercury standard gas control valve 16 is arranged on the other branch. Preferably, the top of the reduction reactor 14 adopts an arch design.

[0040] The heating module 9 is arranged outside the gradient evaporation chamber 8. Preferably, the heating module 9 includes several groups of ceramic heating plates, each group of ceramic heating plates is respectively connected to a temperature control device, and can be independently temperature controlled. The gradient evaporation chamber 8 is connected to a liquid inlet device 10, and the liquid inlet device 10 preferably adopts a syringe pump. The liquid inlet device 10 is connected to a stop valve 13, and the stop valve 13 is connected to a pump 12. The pump 12 preferably adopts a peristaltic pump, and the pump 12 is connected to a mercuric chloride standard solution storage device 11.

[0041] The working method of the above-mentioned elemental mercury and divalent mercury standard gas generation system comprises:

[0042] Add mercuric chloride standard solution to the mercuric chloride standard solution storage device 11, and add stannous chloride solution to the reduction reactor 14; set the temperature of the heating module 9 so that there is a temperature gradient between the high temperature end and the low temperature end of the gradient evaporation chamber 8; set the opening of the flow valve 3 and the temperature of the preheater 4, and open the nitrogen gas storage device 1 to purge the entire system;

[0043] Open the stop valve 13, start the pump 12 and set the opening, the mercuric chloride standard liquid enters the gradient evaporation chamber 8 through the liquid inlet device 10, and vaporizes to generate divalent mercury vapor; the nitrogen in the nitrogen storage device 1 is purified by the filter 2, enters the preheater 4 through the flow valve 3 for preheating, and then enters the gradient evaporation chamber 8 from the high-temperature end of the gradient evaporation chamber 8 to be heated again, so that a temperature gradient is generated in the gradient evaporation chamber 8, and the divalent mercury vapor enters the siphon type three-way joint 6 through the first inlet 6-1;

[0044] Another nitrogen gas enters the siphon type three-way joint 6 from the second inlet 6-2, forming a negative pressure at the first inlet 6-1, so that a pressure gradient is generated in the gradient evaporation chamber 8; the divalent mercury vapor generated in the gradient evaporation chamber 8 outputs the divalent mercury standard gas from the outlet 6-3 under the action of the temperature gradient and the pressure gradient; the divalent mercury standard gas control valve 16 is opened, the elemental mercury standard gas control valve 15 is closed, and the divalent mercury standard gas is output to the system;

[0045] The divalent mercury standard gas control valve 16 is closed, and the elemental mercury standard gas control valve 15 is opened. The divalent mercury standard gas enters the reduction reactor 14 to generate elemental mercury standard gas and then is output to the system.

[0046] The present invention will be further explained below with specific embodiments:

[0047] Example 1

[0048] Step 1: Adding a standard mercuric chloride solution diluted with deionized water to the mercuric chloride standard solution storage device 11, wherein the concentration is M1, the stop valve 13 is in a closed state, and the elemental mercury control valve 15 is in a closed state;

[0049] Step 2: Set the temperature on the left side of the heating module 9 (on the carrier gas pipeline 7 side) to 180°C and the temperature on the right side of the heating module 9 to 160°C;

[0050] Step 3: Open the divalent mercury standard gas control valve 16, set the flow value V1 of the flow valve 3, set the temperature of the preheater 4 to 160°C, open the nitrogen gas storage device 1, and purge the system for 120 seconds;

[0051] Step 4: Turn on the pump 12, set the flow rate Q1, and the mercuric chloride standard solution enters the gradient evaporation chamber 8 through the liquid inlet device 10, and vaporizes to generate divalent mercury vapor;

[0052] Step 5: The nitrogen in the carrier gas pipeline 7 enters the gradient evaporation chamber 8 and is heated again, so that a temperature gradient is generated in the gradient evaporation chamber 8 to prevent the divalent mercury vapor from accumulating and flowing back. The divalent mercury vapor enters the siphon type three-way joint 6 through the first inlet 6-1;

[0053] Step 6: Another nitrogen gas enters the siphon type three-way joint 6 from the second inlet 6-2. As the passage in the siphon type three-way joint 6 becomes smaller, the nitrogen gas flow rate increases, and a negative pressure is formed at the steam inlet. The siphon effect generates a pressure gradient in the gradient evaporation chamber 8;

[0054] Step 7: The mercury vapor generated by the gradient evaporation chamber 8 outputs a divalent mercury standard gas of stable concentration from the outlet 6-3 under the action of the temperature gradient and the pressure gradient. The concentration of the mercury standard gas is M1*Q1 / V1. The flow rates of the pump 12 and the flow valve 3 can also be preset according to the required concentration of the divalent mercury standard gas.

[0055] Example 2

[0056] Step 1: add a standard mercuric chloride solution diluted with deionized water to the mercuric chloride standard solution storage device 11, the concentration of which is M2, add a reducing agent 10% stannous chloride solution to the reduction reactor 14, the stop valve 13 is closed, and the divalent mercury standard gas control valve 16 is closed;

[0057] Step 2: Set the temperature on the left side of the heating module 9 (on the carrier gas pipeline 7 side) to 180°C and the temperature on the right side of the heating module 9 to 160°C;

[0058] Step 3: Open the elemental mercury control valve 15, set the flow value V2 of the flow valve 3, set the temperature of the preheater 4 to 160°C, open the nitrogen gas storage device 1, and purge the system for 120 seconds;

[0059] Step 4: Turn on the pump 12, set the flow rate Q2, and the mercuric chloride standard solution enters the gradient evaporation chamber 8 through the liquid inlet device 10, and vaporizes to generate divalent mercury vapor;

[0060] Step 5: The nitrogen in the carrier gas pipeline 7 enters the gradient evaporation chamber 8 and is heated again, so that a temperature gradient is generated in the gradient evaporation chamber 8 to prevent the divalent mercury vapor from accumulating and flowing back. The divalent mercury vapor passes through the gradient evaporation chamber 8 and enters the siphon three-way joint 6;

[0061] Step 6: Another nitrogen gas enters the siphon type three-way joint 6 from the second inlet 6-2. As the passage in the siphon type three-way joint 6 becomes smaller, the nitrogen gas flow rate increases, and a negative pressure is formed at the steam inlet. The siphon effect generates a pressure gradient in the gradient evaporation chamber 8;

[0062] Step 7: The mercury vapor generated in the gradient evaporation chamber 8 outputs a stable concentration of divalent mercury standard gas from the outlet 6-3 under the action of the temperature gradient and the pressure gradient. After the divalent mercury standard gas enters the reduction reactor 14, it undergoes an oxidation-reduction reaction with the stannous chloride solution to generate elemental mercury, Hg 2+ +Sn 2+ =Hg↑+Sn 4+ , the elemental mercury standard gas is output from the top of the reduction reactor 14. The concentration of the mercury standard gas is M2*Q2 / V2. The pump 12 and the flow valve 3 can also be preset according to the required elemental mercury standard gas concentration.

[0063] The above is only part of the embodiments of the present invention. Although some terms are used in the present invention, the possibility of using other terms is not excluded. The use of these terms is only for the convenience of describing and explaining the essence of the present invention. It is contrary to the spirit of the present invention to interpret them as any additional restrictions. The above is only to further illustrate the content of the present invention with examples for easier understanding, but it does not mean that the embodiments of the present invention are limited to this. Any technical extension or re-creation made according to the present invention is protected by the present invention.

Claims

1. A system for generating elemental mercury and divalent mercury standard gas, characterized in that: It comprises a nitrogen gas storage device (1), a filter (2), a flow valve (3), a preheater (4), a tee (5), a siphon type tee joint (6), a gradient evaporation chamber (8), a heating module (9), a liquid inlet device (10), a mercuric chloride standard liquid storage device (11), a pump (12), a stop valve (13), a reduction reactor (14), an elemental mercury standard gas control valve (15) and a divalent mercury standard gas control valve (16); The siphon type three-way joint (6) comprises a first inlet (6-1), a second inlet (6-2) and an outlet (6-3), wherein a venturi tube structure is provided between the second inlet (6-2) and the outlet (6-3) of the siphon type three-way joint (6); the first inlet (6-1) is connected to the low temperature end of the gradient evaporation chamber (8), the high temperature end of the gradient evaporation chamber (8) is connected to the three-way joint (5) through a carrier gas pipeline (7), and the three-way joint (5) is also connected to the second inlet (6-2) and the preheater (4) respectively; the preheater (4) is connected to the flow valve (3), the flow valve (3) is connected to the filter (2), the filter (2) is filled with modified activated carbon, and the filter (2) is connected to the nitrogen gas storage device (1); the outlet (6-3) is connected to two branches, the reduction reactor (14) and the elemental mercury standard gas control valve (15) are arranged on one branch, and the divalent mercury standard gas control valve (16) is arranged on the other branch; The heating module (9) is arranged outside the gradient evaporation chamber (8), the liquid inlet device (10) is arranged at the upper part of the low temperature end of the gradient evaporation chamber (8) and is communicated with the interior of the gradient evaporation chamber (8), the liquid inlet device (10) is connected to a stop valve (13), the stop valve (13) is connected to a pump (12), and the pump (12) is connected to a mercuric chloride standard solution storage device (11).

2. The elemental mercury and divalent mercury standard gas generation system according to claim 1, characterized in that: The siphon type three-way joint (6) is a polytetrafluoroethylene joint.

3. The elemental mercury and divalent mercury standard gas generation system according to claim 1, characterized in that: The inner cavity of the gradient evaporation chamber (8) is arc-shaped.

4. The elemental mercury and divalent mercury standard gas generation system according to claim 1, characterized in that: The heating module (9) comprises a plurality of groups of ceramic heating plates, and each group of ceramic heating plates is respectively connected to a temperature control device.

5. The elemental mercury and divalent mercury standard gas generation system according to claim 1, characterized in that: The liquid inlet device (10) is a syringe pump.

6. The elemental mercury and divalent mercury standard gas generation system according to claim 1, characterized in that: The pump (12) is a peristaltic pump.

7. The elemental mercury and divalent mercury standard gas generation system according to claim 1, characterized in that: The top of the reduction reactor (14) is arched.

8. The working method of the elemental mercury and divalent mercury standard gas generation system according to any one of claims 1 to 7, characterized in that: include: Adding a mercuric chloride standard solution to a mercuric chloride standard solution storage device (11), and adding a stannous chloride solution to a reduction reactor (14); The temperature of the heating module (9) is set so that a temperature gradient exists between the high temperature end and the low temperature end of the gradient evaporation chamber (8); the opening of the flow valve (3) and the temperature of the preheater (4) are set, and the nitrogen gas storage device (1) is opened to purge the entire system; The stop valve (13) is opened, the pump (12) is turned on and the opening is set, and the mercuric chloride standard liquid enters the gradient evaporation chamber (8) through the liquid inlet device (10) and vaporizes to generate divalent mercury vapor; the nitrogen in the nitrogen storage device (1) is purified by the filter (2), enters the preheater (4) through the flow valve (3) for preheating, and then enters the gradient evaporation chamber (8) from the high-temperature end of the gradient evaporation chamber (8) to be heated again, so that a temperature gradient is generated in the gradient evaporation chamber (8), and the divalent mercury vapor enters the siphon type three-way joint (6) through the first inlet (6-1); Another nitrogen gas enters the siphon type three-way joint (6) from the second inlet (6-2), forms a negative pressure at the first inlet (6-1), and generates a pressure gradient in the gradient evaporation chamber (8); the divalent mercury vapor generated in the gradient evaporation chamber (8) is output as divalent mercury standard gas from the outlet (6-3) under the action of the temperature gradient and the pressure gradient; The divalent mercury standard gas control valve (16) is opened, the elemental mercury standard gas control valve (15) is closed, and the divalent mercury standard gas is output to the system; The divalent mercury standard gas control valve (16) is closed, and the elemental mercury standard gas control valve (15) is opened, and the divalent mercury standard gas enters the reduction reactor (14) to generate elemental mercury standard gas and then is output to the system.

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