An apparatus and method for online measurement of sodium content in ammonia water

Abstract

The present invention discloses a device and method for online measuring the sodium content of ammonia water. The device comprises an online sodium meter, an online sodium meter flowmeter, a water inlet pipe, a dosing pump outlet flowmeter, a dosing pump, an air outlet pipe, a gas washing bottle and an air inlet pipe. The method adopts a dynamic online measurement mode, firstly measures the mass concentration of sodium ions in a pure water solvent, dilutes the ammonia water into a solution of a certain proportion with pure water, adds the ammonia solution into the pure water with a dosing pump, dilutes the ammonia solution, adjusts the output of the pump, dilutes the ammonia water concentration to a reasonable range, reduces the concentration of ammonium ions, and makes the influence of ammonium ions on the measurement of sodium ions negligible. The diluted ammonia solution enters the sodium meter flowmeter and the online sodium meter in turn to measure the mass concentration of sodium ions. The sodium content of ammonia water is determined according to the mass concentration of sodium ions in the diluted ammonia solution, the mass concentration of sodium ions in the pure water solvent, the flow value at the dosing pump outlet and the flow value at the online sodium meter. The method can quickly and accurately measure the sodium content of ammonia water, and has high use value and promotion value.

Description

Technical Field

[0001] The invention relates to the field of on-line chemical instrument measurement in power plants, and in particular to a device and method for on-line measuring the sodium content of ammonia water. Background Art

[0002] The alkalizer used to adjust the pH value of feed water in thermal power plants is generally ammonia (NH 3 ). The essence of feed water ammonia treatment is to use ammonia to neutralize the free carbon dioxide in the feed water and alkalize the medium, increase the pH value of the feed water to the specified value, and control the corrosion rate of steel and copper alloy materials in the feed water system within a lower range to ensure that the iron and copper content meet the specified standards. Feed water ammonia is added by ammonia water, and the sodium content of ammonia water must be strictly controlled to make the sodium content meet the standards specified in the national standard GB / T 631-2007 "Chemical Reagent Ammonia Water". If the sodium content in ammonia water exceeds the standard, it will cause the sodium content of the thermal system to exceed the standard, and sodium salt deposition may occur in the superheater and turbine. Therefore, quickly and accurately measuring the sodium content of ammonia water is of great significance to the safe and economical operation of the unit.

[0003] At present, the measurement of sodium in ammonia water mainly adopts the offline measurement method. Since the electrode response takes a certain amount of time, the measurement accuracy of sodium ions is very poor due to interferences such as potassium ions seeping from the reference electrode, the influence of dust in the air, and the dissolution of the sodium electrode under high pH measurement conditions. At the same time, because the sodium electrode is sensitive to ammonium ions (NH 4 + ) is selective for sodium ions (Na + ), and the ammonium ion concentration in ammonia water is extremely high. If the online sodium meter directly measures the sodium content of ammonia water, it will inevitably cause a huge measurement error. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention aims to provide a device and method for online measuring the sodium content of ammonia water, which adopts a dynamic online measurement mode; dilutes the concentration of ammonia water to a reasonable range, reduces the concentration of ammonium ions, makes the influence of ammonium ions on the measurement of sodium ions negligible, and can quickly and accurately measure the sodium content of ammonia water.

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

[0006] An online device for measuring the sodium content of ammonia water comprises an online sodium meter, a sodium meter flow meter, a dosing pump outlet flow meter, a dosing pump and a dosing bottle;

[0007] The water inlet of the online sodium meter is connected to the water outlet of the sodium meter flowmeter, the water inlet of the sodium meter flowmeter is respectively connected to the water source and the dosing pump outlet flowmeter, the dosing pump outlet flowmeter is connected to the dosing bottle through the dosing pump, the dosing bottle is connected to the purification device, and the dosing bottle is filled with ammonia solution.

[0008] Preferably, the purification device includes a gas washing bottle, and an air outlet pipe and an air inlet pipe are arranged at the mouth of the gas washing bottle, one end of the air inlet pipe is connected to the gas washing bottle, and the other end is located outside the gas washing bottle, one end of the air outlet pipe is connected to the gas washing bottle, and the other end of the air outlet pipe is connected to the dosing bottle.

[0009] Preferably, the gas washing bottle is filled with liquid, the end of the air inlet pipe extends into the liquid, and the end of the air outlet pipe is located above the water level of the liquid.

[0010] Preferably, the liquid is pure water.

[0011] Preferably, the mouths of the gas washing bottle and the dosing bottle are both provided with sealing structures, and both ends of the air outlet pipe and the air inlet pipe are connected with the gas washing bottle and the dosing bottle through the sealing structures.

[0012] Preferably, the water source is pure water, and the water inlet of the sodium flow meter is connected to a pure water machine.

[0013] Preferably, the purification device is an air filter.

[0014] A method for measuring the sodium content of ammonia water online comprises the following steps:

[0015] Step 1: Pass pure water into the online sodium meter to obtain the sodium mass concentration C of pure water 1 ;

[0016] Step 2: Take V 1 Volume of ammonia water, add to V 2 Prepare a certain proportion of ammonia solution in 100% pure water and pour it into the dosing bottle;

[0017] Step 3: Start the dosing pump to mix the ammonia solution in the dosing bottle with pure water to dilute the ammonia solution. The diluted ammonia solution passes through the sodium meter flow meter and the online sodium meter in turn to obtain the flow rate Q of the dosing pump outlet flow meter. 1 , the flow rate Q of the sodium flow meter 2 , and the sodium mass concentration C 2 ;

[0018] Step 4: According to the sodium mass concentration C of pure water 1 , sodium mass concentration C 2 And the flow rate Q of the dosing pump outlet flow meter 1 and the flow rate Q of the sodium flow meter 2 , determine the sodium mass fraction W of ammonia water.

[0019] Preferably, in step 2, ammonia water and pure water are mixed in a volume ratio of 1:(500-1000) to form an ammonia solution.

[0020] Preferably, the method for determining the sodium mass fraction W of the ammonia water in step 4 is as follows:

[0021]

[0022] Where ρ is the density of aqueous ammonia.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] The invention provides a device for online measuring the sodium content of ammonia water. The device adopts a dynamic online measurement mode. Potassium ions seeping out of a reference electrode will not interfere with the measurement. The sodium electrode will not dissolve under high pH measurement conditions and will not interfere with the measurement. Firstly, ammonia water is prepared into an ammonia solution of a certain proportion. A dosing pump is started and the ammonia solution is diluted with pure water. The concentration of ammonia water is diluted to a reasonable range, thereby reducing the concentration of ammonium ions and making the influence of ammonium ions on the measurement of sodium ions negligible. At the same time, dust in the air entering the dosing bottle is cleaned by a gas purification device to avoid the influence of sodium ions in the air dust and eliminate the sodium content of the pure water solvent. The measuring device can quickly and accurately measure the sodium content of ammonia water. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the structure of the device for measuring the sodium content of ammonia water according to the present invention.

[0026] In the figure: 1. Online sodium meter, 2. Sodium meter flowmeter, 3. Water inlet pipe, 4. Dosing pump outlet flowmeter, 5. Dosing pump, 6. Dosing bottle, 7. Air outlet pipe, 8. Washing bottle, 9. Air inlet pipe. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below in conjunction with the accompanying drawings, which are intended to explain the present invention rather than to limit it.

[0028] See also Figure 1 , a device for online measuring the sodium content of ammonia water, comprising an online sodium meter 1, a sodium meter flowmeter 2, a dosing pump outlet flowmeter 4, a dosing pump 5 and a dosing bottle 6.

[0029] Among them, the water inlet of the online sodium meter 1 is connected to the outlet of the sodium meter flowmeter 2, the inlet of the sodium meter flowmeter 2 is respectively connected to the water source and the dosing pump outlet flowmeter 4, the dosing pump outlet flowmeter 4 is connected to the dosing bottle 6 through the dosing pump 5, the dosing bottle 6 is connected to the purification device, and the dosing bottle 6 is filled with an ammonia solution.

[0030] The above-mentioned purification device includes a gas washing bottle 8, which is filled with pure water. An air outlet pipe 7 and an air inlet pipe 9 are arranged at the mouth of the gas washing bottle 8. One end of the air inlet pipe 9 extends into the pure water, and the other end is located outside the gas washing bottle 8. One end of the air outlet pipe 7 extends into the gas washing bottle 8 and is located above the water level line of the pure water. The other end of the air outlet pipe 7 is connected to the dosing bottle 6.

[0031] When the dosing pump is working, the ammonia solution in the dosing bottle 6 is sucked out by negative pressure. In order to prevent the unpurified air from outside from entering the dosing bottle 6, a sealing structure is set at the mouth of the dosing bottle, so that the air can only enter through the washing bottle and be purified by pure water. The purified air is sucked into the dosing bottle under the action of negative pressure, thus preventing the sodium ions in the air from dissolving in the ammonia solution and affecting the measurement results; secondly, in order to prevent the air from entering the air outlet pipe without passing through the pure water, a sealing structure is also set at the mouth of the washing bottle, so that the air can only enter the pure water through the air inlet pipe 9, thereby achieving air purification.

[0032] The sodium meter flowmeter is connected to the pure water machine through the water inlet pipe 3. The pure water produced by the pure water machine is input to the sodium meter flowmeter 2 and the online sodium meter 1, and is also used to dilute the ammonia solution.

[0033] Sealing structures are provided at the mouths of the gas washing bottle 8 and the dosing bottle 6, and both ends of the air outlet pipe 7 and the air inlet pipe 9 are connected to the gas washing bottle 8 and the dosing bottle 6 through the sealing structures, so that dust can be prevented from entering the dosing bottle, and the sodium ions in the dust can be prevented from affecting the measurement results, thereby improving the measurement accuracy.

[0034] The sealing structure is an elastic sealing plug made of rubber or silicone.

[0035] In another embodiment, a gas filter is used to filter the air, and the gas filter is connected to the dosing bottle 6 through a pipeline.

[0036] The following is a detailed description of a method for measuring the sodium content of ammonia water online provided by the present invention, comprising the following steps:

[0037] Step 1: Pass pure water into the online sodium meter, and after the measured value stabilizes, record the sodium mass concentration C of the pure water. 1 .

[0038] Step 2: Pour a certain amount of pure water into the washing bottle to clean the dust in the air entering the dosing bottle.

[0039] Step 3: Take V 1 Volume of ammonia water, add to V 2 A certain proportion of ammonia solution is prepared in 1 volume of pure water to dilute the ammonia water, and the ammonia solution is poured into the dosing bottle.

[0040] Ammonia water and pure water are mixed in a volume ratio of 1:(500-1000) to form an ammonia solution.

[0041] Step 4: Start the dosing pump to mix the ammonia solution in the dosing bottle with pure water to dilute the ammonia solution prepared in step 3. The diluted ammonia solution passes through the sodium meter flow meter 2 and the online sodium meter 1 in sequence, and the flow rate Q of the dosing pump outlet flow meter 4 is recorded. 1 and the flow rate Q of the sodium flow meter 2 After the online sodium meter measurement value stabilizes, record the sodium mass concentration C 2 .

[0042] Specifically, by controlling the flow rate of the water source and the power of the dosing pump, the flow rates of pure water and ammonia solution can be controlled, so that the pure water dilutes the ammonia solution prepared in step 3 to within a reasonable range and then passes through the sodium meter flowmeter 2 and the online sodium meter 1.

[0043] Step 5: According to the sodium mass concentration C of pure water 1 , sodium mass concentration C 2 And the flow rate Q of the dosing pump outlet flow meter 4 1 and the flow rate Q of the sodium flow meter 2 , determine the sodium mass fraction W of ammonia water, and calculate it according to the following formula:

[0044]

[0045] Where ρ is the density of aqueous ammonia.

[0046] This measurement method uses a dynamic online measurement method to pass pure water into the online sodium meter. After the measured value stabilizes, the sodium mass concentration C of the pure water is recorded. 1 , then take V 1 Volume of ammonia water, add to V 2 Ammonia solution is initially diluted in a volume of pure water to prepare a certain proportion of ammonia solution, which is poured into the dosing bottle. Then, a certain amount of pure water is poured into the gas washing bottle, and the power of the dosing pump is started and controlled. The ammonia solution is added to the pure water to dilute the ammonia solution so that the concentration of ammonia water is diluted to a reasonable range, thereby reducing the concentration of ammonium ions and making the influence of ammonium ions on the measurement of sodium ions negligible. The diluted ammonia solution passes through the sodium meter flowmeter 2 and the online sodium meter 1 in turn, and the outlet flow rate Q of the dosing pump is recorded. 1 and online sodium table flow Q 2 After the online sodium meter measurement value stabilizes, record the mass concentration C 2 When the dosing pump is working, air enters from the air inlet pipe and then passes through the pure water in the washing bottle. The dust in the air dissolves in the water, especially the sodium ions in the dust dissolve in the water, which filters the air. The filtered air enters the dosing bottle through the air outlet pipe, thus avoiding the influence of dust on the measurement results.

[0047] Step 3 V 1 Volume of ammonia water, add to V 2 A certain proportion of ammonia solution is prepared in pure water, and the sodium mass concentration of the ammonia solution is C 3 , the following relationship is satisfied within a certain time T:

[0048] C 3 Q 1 T=(C 2 -C 1 )Q 2 T (1)

[0049] Inferred:

[0050] C 3 Q 1 =(C 2 -C 1 )Q 2 (2)

[0051] Inferred:

[0052]

[0053] The sodium concentration of ammonia water is C 氨 The ammonia solution prepared in step 3 has the following relationship:

[0054] C 3 (V 1 +V 2 )=C 氨 V 1 +C 1 V 2 (4)

[0055] Inferred:

[0056]

[0057] Substituting (3) into (5), we can get the mass concentration of ammonia water C 氨 :

[0058]

[0059] The density of ammonia water is ρ, then the mass fraction of sodium in ammonia water W is:

[0060]

[0061] Substituting (6) into (7), we can obtain the mass fraction of sodium ammonia water W:

[0062]

[0063] Taking the measurement of analytical pure ammonia water as an example, the measurement results of this method are shown in Table 1.

[0064] Table 1 Measurement results

[0065]

[0066] The sodium index in the national standard GB / T 631-2007 "Chemical Reagent Ammonia Water" is: sodium mass fraction ≤ 0.0005%. The sodium content of analytical pure ammonia water was measured using this method, and the sodium mass fraction was less than 0.0005%.

[0067] The present invention adopts a dynamic online measurement method. The potassium ions seeping out of the reference electrode will not interfere with the measurement. The sodium electrode will not dissolve under high pH measurement conditions, so it will not interfere with the measurement. The dust in the air entering the dosing bottle is cleaned to eliminate the influence of air dust. The method dilutes the concentration of ammonia water to a reasonable range, reduces the concentration of ammonium ions, and makes the influence of ammonium ions on the measurement of sodium ions negligible. The diluted ammonia water enters the online sodium meter to measure the mass concentration of sodium ions. The sodium content of the ammonia water is calculated based on the mass concentration of sodium ions in the diluted ammonia water, the mass concentration of sodium ions in the pure water solvent, the flow value of the dosing pump outlet and the flow value of the online sodium meter. The method can quickly and accurately measure the sodium content of the ammonia water. The method also eliminates the sodium content of the pure water solvent, making the measurement more accurate. In this way, the measurement method can quickly and accurately measure the sodium content of the ammonia water, and the method is particularly suitable for use at the production site.

[0068] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for online measurement of sodium content in aqueous ammonia, characterized in that: The method is applied to a device for online measurement of sodium content in ammonia water, the device comprising an online sodium meter (1), a sodium meter flow meter (2), a dosing pump outlet flow meter (4), a dosing pump (5) and a dosing bottle (6); The water inlet of the online sodium meter (1) is connected to the water outlet of the sodium meter flow meter (2), the water inlet of the sodium meter flow meter (2) is respectively connected to a water source and a dosing pump outlet flow meter (4), the dosing pump outlet flow meter (4) is connected to a dosing bottle (6) via a dosing pump (5), the dosing bottle (6) is connected to a purification device, and the dosing bottle (6) is filled with an ammonia solution; The purification device comprises a gas washing bottle (8), an outlet pipe (7) and an inlet pipe (9) are arranged at the mouth of the gas washing bottle (8), one end of the inlet pipe (9) is connected to the gas washing bottle (8), and the other end is located outside the gas washing bottle (8), one end of the outlet pipe (7) is connected to the gas washing bottle (8), and the other end of the outlet pipe (7) is connected to the dosing bottle (6); The gas washing bottle (8) is filled with liquid, the end of the gas inlet pipe (9) extends into the liquid, and the end of the gas outlet pipe (7) is located above the water level of the liquid; The measuring method of the device for online measuring the sodium content of ammonia water comprises the following steps: Step 1, passing pure water into an online sodium meter to obtain the sodium mass concentration C1 of the pure water; Step 2: Take V1 volume of ammonia water, add it to V2 volume of pure water to make a certain proportion of ammonia solution, and pour it into the dosing bottle; Step 3, start the dosing pump to mix the ammonia solution and pure water in the dosing bottle to dilute the ammonia solution, and the diluted ammonia solution passes through the sodium meter flow meter (2) and the online sodium meter (1) in sequence to obtain the flow rate Q1 of the dosing pump outlet flow meter (4), the flow rate Q2 of the sodium meter flow meter, and the sodium mass concentration C2; Step 4, determining the sodium mass fraction W of the ammonia water according to the sodium mass concentration C1 and the sodium mass concentration C2 of the pure water, the flow rate Q1 of the dosing pump outlet flow meter (4), and the flow rate Q2 of the sodium meter flow meter; In step 3, ammonia solution with a volume of V1 is added to pure water with a volume of V2 to prepare an ammonia solution of a certain proportion, the sodium mass concentration of the ammonia solution is C3, and the following relationship is satisfied within a certain time T: The sodium concentration of ammonia water is C 氨 The ammonia solution prepared in step 3 has the following relationship: The ammonia mass concentration C 氨 : Then the sodium mass fraction W of ammonia water is: in, is the density of aqueous ammonia.

2. The method for online measuring sodium content of ammonia water according to claim 1, characterized in that: The mouths of the gas washing bottle and the medicine adding bottle are both provided with sealing structures, and both ends of the air outlet pipe and the air inlet pipe are connected with the gas washing bottle and the medicine adding bottle through the sealing structures.

3. The method for online measuring sodium content of ammonia water according to claim 1, characterized in that: The water source is pure water, and the water inlet of the sodium flow meter (2) is connected to a pure water machine.

4. The method for online measuring sodium content of ammonia water according to claim 1, characterized in that: The purification device is an air filter.

5. The method for online measuring sodium content of ammonia water according to claim 1, characterized in that: In step 2, ammonia water and pure water are mixed in a volume ratio of 1: (500-1000) to form an ammonia solution.

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