☆ Common faults and troubleshooting

【1】 The airtightness of the pneumatic circuit decreases:

The flow meter indication should be between 0.8 and 1.2. If the airtightness decreases, the following components should be inspected: air pump, flow meter, glass tube, rubber tube, and air circuit connection.

【2】 Electrolytic cell

1. The leakage of the electrolytic cell leads to a decrease in the airtightness of the gas path.

2. The four electrode plates in the electrolytic cell should be cleaned if there is dirt on them

3. The four electrodes in the electrolytic cell should be reliably connected to the controller.

【3】 Mixer:

The weakening of the magnetic force of the stirring rod is a common cause of mixing loss and should be replaced.

【4】 Temperature control section

1. A. The temperature remains displayed at 1999 ℃, indicating that the thermocouple circuit is not connected or there is an internal open circuit.

B. If the temperature does not increase but there is heating current, it indicates that the thermocouple is connected in reverse.

C. If the temperature keeps showing room temperature, it indicates a short circuit in the thermocouple wiring.

2. If the temperature value is lower than the set furnace temperature, there should be a heating furnace flow. If the furnace current is displayed as 0.0A, it indicates that the fuse tube is damaged, and the silicon carbon tube itself has an internal open circuit or the connection is not connected.

3. The large temperature fluctuation is generally caused by silicon carbon tubes. The resistance value should be 7~8 Ω, and it is recommended to purchase our company's original accessories.

【5】 Sample sending institution

To cooperate with the fault diagnosis of the prototype, the instrument motherboard provides four indicator lights, and the specific fault location can be determined based on the condition of the indicator lights.

◎◎◎◎◎

1 2 3 4

1: When the motor is moving forward, this indicator light should be on.

2: When the motor is in reverse, this indicator light should be on.

3: When the sample sending institution stays at 500 ℃ or 1050 ℃, the indicator light should light up.

4: When the sample sending mechanism is in its original position, the indicator light should be on.

• Reagents and materials

• Tungsten trioxide (HG10-1129)

• Color changing silicone: industrial product

Potassium iodide (GB/T1272)

Potassium bromide (GB/T649)

Ice acetic acid (GB/T676)

• Distilled water

☆ Regarding the preparation of electrolyte:

Weigh 5 grams of potassium iodide and 5 grams of potassium bromide, dissolve them in 250 milliliters of distilled water, and then add 10 milliliters of glacial acetic acid. The electrolyte can be reused, and the duration of use depends on the number of repeated uses and the sulfur content of the sample. When the pH value of the electrolyte is 1-3, it can be used, but when the pH value is less than 1, the electrolyte should be reconfigured.

☆ Regarding the preparation of coal samples:

Before weighing the sample, the sample in the sample bottle should be mixed as evenly as possible. It is best to hold the sample bottle with a lid by hand, and make circular movements of the wrist from top to bottom. Do not shake the sample bottle up or down. Or open the bottle cap and stir the sample with a weighing spoon. Adequate mixing of the samples is crucial to ensuring the accuracy and precision of the results.

☆ Maintenance of instruments:

1. After the electrolysis phenomenon occurs in the electrolytic cell, the electrolytic cell should be opened and the electrode should be wiped with ethanol or acetone to make it appear bright silver white. If it is heavily contaminated, it can be carefully treated with fine sandpaper or a small knife to remove any attachments on the electrode, and then cleaned with ethanol or acetone. Be careful not to use organic solvents to wipe the organic glass cylinder wall of the electrolytic cell to prevent possible shell cracking.

When there is black sediment on the glass melting plate and pipeline, it should be cleaned in a timely manner. The cleaning method is as follows:

Remove the electrolytic cell (open the top cover) and first add some water to the electrolytic cell to avoid submerging the melting plate. Tilt the electrolytic cell and use a dropper to inject the prepared washing solution (5 grams of potassium dichromate and 10 milliliters of water, heat, melt and cool, and slowly add 100 milliliters of concentrated sulfuric acid) into the branch of the melting plate. After the washing solution flows clean, repeat 1-2 times to remove the black precipitates in the melting plate and branch. Then rinse the electrolytic cell with tap water and use ear wash balls to draw water from the molten plate until no residual cleaning solution is left. The molten plate should be as white as before. Use filter paper strips to dry the glass melting plate and its branches, and then add electrolyte for use.

The rubber pipes connecting the air circuit should be checked regularly, as their joints are most prone to aging and air leakage.

The small porcelain boat containing 4 coal samples should be stored in a clean container, and the new porcelain boat should undergo high-temperature treatment before being used for the first time. A porcelain boat that has been weighed and contains coal samples should be especially careful not to be contaminated by hands or tables with coal stuck on them. It is best to have a white porcelain boat specifically placed for the porcelain boat.

Regularly use standard sample validation instruments to verify if the instrument is working properly. If there is any rupture of the reducer, if the electrolyte electrode is contaminated, and if the gas path is leaking or blocked.

The instrument should be protected from dust and corrosive gases and used in a dry environment. If not used for a long time, it should be covered and regularly removed and powered on to dry the moisture inside the instrument. If the electrolytic cell is not used for a long time, the connecting hose should be removed to prevent aging and adhesion.

☆ Fault phenomena, causes, and handling methods:

1. Air purification device: including a flow meter, two glass tubes, an air pump, and connecting rubber hoses.

(1) Flowmeter: Due to its connection to the drying tube, its inlet and outlet may be blocked by silica gel particles inside the drying tube, resulting in unstable gas flow or inability to adjust to the specified flow rate; If it enters the liquid or combines with dust and moisture inside, it will cause great resistance to the small float, and also cause unstable flow or inability to adjust; Its inherent damage, such as inadequate sealing of the internal air circuit and needle valves, can also cause the flow rate to be uncontrollable or unstable.

(2) Glass tube: The lower two ends should be filled with de ester cotton. Mask the upper and lower air holes separately to prevent their contents from being sucked into the connecting pipeline and blocking the air path. If there are small cracks on it, special glue can be used to seal it. Once the silicone gel changes color completely, it should be replaced in a timely manner.

(3) Air pump: Its principle is to drive two leather cups to move back and forth internally by electromagnetic force, generating aerodynamic force. Its malfunction is generally caused by the rupture of two leather cups. If the leather bowl ruptures, the suction force decreases, which is manifested as the float of the flow meter continuously falling down and the flow rate unstable, similar to the performance of 1 and 2.

(4) Rubber hose: prone to aging, causing system leakage and unstable flow rate.

The performance of the above faults is the same, and the leak detection work that needs to be carried out every time is aimed at them (including the electrolytic cell), which is reflected in the sample results, making the measurement results unstable, fluctuating high and low.

2 electrolytic cells

(1) The top cover of the electrolytic cell needs to be tightened, the sealing ring is aging, and glue is opened at each inlet and outlet hole, which are all reasons for air leakage.

(2) There are four electrode plates in the electrolytic cell, one group of two small ones, which is the indicator electrode and the other group of two large ones, which is the electrolytic electrode. The indicator electrode plays a role in sensing the titration of the electrolyte and controlling the titration of the electrolytic electrode. If any electrode malfunctions, it will cause the experiment to be unable to proceed. So it is necessary to ensure the cleanliness of the four electrode surfaces, and the sealing area must not crack.

If the indicator electrode is disconnected from its lead (such as when the sealing glue cracks), it will cause continuous electrolysis of the electrolytic electrode and cannot be stopped. The electrolyte turns red, and the screen quickly counts (even if the coal sample is not placed), and the surface is also dirty. If the electrolytic electrode electrode and its lead are disconnected, it will cause the electrolyte to become whiter and whiter during sample making, but the screen will never count, which is equivalent to the electrolytic switch being closed. The surface fouling is manifested as electrolysis delay, that is, electrolysis suddenly opens when the liquid is very white, and the measurement results are seriously low and unstable.

Solution: For surfaces that are sticky or dirty, they can be cleaned. If the adhesive causes disconnection, the residual adhesive can be removed, the plastic tube connected to the electrode can be removed, its inner wall cleaned, the corroded lead part replaced, re welded, and sealed. The crack cannot be sealed because electrolyte may have accumulated inside, the lead has been corroded, and it is not conductive to the electrode.

(3) The fault phenomenon caused by oxidation and loosening of the lead wire plug of the electrolytic cell and the socket on the machine over time is similar to that caused by contamination or open circuit of the electrode. The plug can be coated with a thin layer of solder to remove its oxide layer and increase the tightness between the plug and the socket. The lead wire can also be directly soldered to the corresponding point inside the machine.

3 Stirrer: Its principle is to use a rotating magnetic field to drive the magnetic stirring rod in the electrolytic cell to rotate. If the magnetic field of the mixer weakens or its motor speed slows down, it will correspondingly cause a slowdown in the stirring speed. The weakening of the magnetic force of the stirring rod is a common cause of mixing loss, and it can be replaced or magnetized. The faster the stirring speed, the more conducive it is to the uniform titration of SO2 hydrates. A low stirring speed is also a reason for the unsatisfactory measurement results. If the stirrer stops rotating in the experiment, it means that electrolysis occurs.

4. Combustion furnace section:

(1) The correct installation of the thermocouple is crucial, as it should be inserted downwards and retracted after touching the silicon carbon tube

2mm The further away it is, the lower the displayed value of the instrument will be compared to the actual furnace temperature and will not rise to the set temperature (the actual furnace temperature has already been reached), or the control accuracy will be poor when it rises to the set ℃, with fluctuations of several tens or even hundreds of degrees above the temperature control point. If the thermocouple touches the silicon carbon tube, when it rises to high temperature, there will be leakage current flowing into the machine from the silicon carbon tube, causing significant temperature fluctuations on the display, Falling in a straight line may even result in negative temperature (distinguishing it from the temperature drop caused by thermocouple return), severely damaging the temperature part of the instrument's circuit. The phenomenon of abnormal temperature control and high furnace temperature (much higher than 1050 ℃) is that when viewed inside the furnace, it is no longer a normal red light, but has turned white, often causing adhesion between the quartz boat and the reducer. In severe cases, there is bending of the reducer and adhesion between the reducer and the silicon carbon pipe. If coal samples are sent in and out, it will be found that the coal ash has melted on the porcelain boat and cannot be scraped off. The thermocouple position or set temperature can be adjusted according to the actual situation. If the thermocouple is not properly connected or has an internal open circuit, the instrument will display 1, indicating out of range. If the thermocouple is short circuited, the instrument will always display room temperature.

(2) The reducer is a closed combustion chamber of the sample, ensuring that all SO2 gas generated during combustion enters the electrolytic cell under the action of the gas pump. If there are cracks or fractures, it will cause the escape of sulfur-containing gas, resulting in severely low and unstable measurement results. The reducer is at high temperature and hidden inside the furnace, so the fracture is relatively hidden. If you feel abnormal, you can loosen the fastening screw at the furnace mouth and remove it for inspection.

(3) When debugging silicon carbon tubes, use 10 Ω as the * * * value. If its resistance value is too large or too small, it will cause a decrease in the heating current of * * *. After natural aging, the resistance value will increase. Manifested as prolonged heating time or inability to reach the set temperature: At this time, the furnace flow simulation display light cannot reach the 9 or 10 light on position. The general solution is to replace it, and the resistance value can be measured during judgment.

Permissible deviation for total sulfur determination (GB214-83)