Sixty-nine questions and answers on carbon material production technology

In carbon production, there are many factors that affect the purity of screening, such as the amount of feed, the uniformity of feed, the shape of the screen, the movement of the screen, the shape of the particles and the water content of the material. If the feeding amount is too large, the sieve layer is too thick, which will reduce the purity, and the uneven feeding will make the purity unstable. Inertial vibrating screens with square meshes are widely used in carbon production. The reciprocating movement and up-and-down vibration of the screen surface is beneficial for the material particles to contact the screen holes, and the relative movement between the material block and the screen surface is relatively large, which is beneficial to the improvement of the screening purity.

1. Choose the type of carbon raw material;
2. Determine the ratio of different types of raw materials;
3. Determine the particle size composition of solid carbon raw materials;
4. Determine the softening point and dosage of the binder.

1. Carry out a comprehensive inspection before starting the sieve. All continuous fasteners must be reliable. Check whether the electrical components are invalid, the main shaft of the vibrating (sieve) device is flexible, and the bearing lubrication is good.
2. The start sequence of the sieve is: first start the dust-proof device, then start the sieve, wait until it runs normally, and then feed evenly, the stopping sequence is the opposite.
3. When the sieve is in motion, pay close attention to the bearing temperature and lubrication system.
4. Pay attention to whether the sieve has strong noise during operation, the vibration of the sieve should be balanced, and no abnormal swing is allowed. When the sieve swings, check whether the elasticity of the four support springs is consistent and whether there is any breakage.
5. During the operation of the vibrating screen, the wear condition should be checked regularly. If excessive wear parts are found, they should be replaced in time.
6. Frequently check whether the screen is loose and whether there is material leakage due to local abrasion of the screen. If found, stop and repair it immediately.

1. Vibrating screen;
2. Cylindrical screen;
3. Cabinet screen;
4. Shake the sieve.

1. The nature of the material;
2. Screen surface types and structural parameters;
3. Operating conditions.

Through the sieve, the material is divided into several granularity levels according to its size. This process is called sieving.

1. Before starting, check the flexibility of each component, the position of the clutch, and tighten the fasteners.
2. Frequently check the lubrication system, especially the lubrication of the main bearing and reduction box.
3. Stop the machine for inspection when abnormal noise occurs.
4. The clearance and contact area of the toothed gear should be adjusted appropriately.
5. When the liner is excessively worn or taken off, it should be replaced and filled in time.
6. It is necessary to select balls and add steel balls on a regular basis.
7. Pay special attention to the concentric alignment of the shaft heads at both ends.

1. The speed of the ball mill;
2. The amount of ball loaded;
3. The shape of the liner;
4. The diameter of the ball mill;
5. Operating conditions.

1. Start without load, and it is strictly forbidden to drive when there is material in the crushing cavity.
2. Regularly check the wear of the roller skin, and repair or replace it in time.
3. The feed material is evenly distributed, otherwise the roller skin will wear out quickly. At the same time, pay attention to the size of the feed material.
4. Pay attention to the lubrication of the machine and the temperature of the bearings.
5. When shutting down, stop feeding first, and then shut down after the material is emptied.

1. Screen area;
2. Vibration frequency and amplitude;
3. The inclination of the screen;
4. Feeding situation.

The amount of binder coal pitch depends on the surface of the carbon raw material particles and its adsorption capacity for pitch. Adding a certain amount of pitch according to the regulations can make the paste kneaded uniformly and have good plasticity. During the kneading process, when the amount of dry material is added too much , You can add bitumen for blending, but if the bitumen amount is too much, you can’t add dry material for adjustment. This is because the fluidity of the added dry material particles is not as good as that of liquid bitumen, and cannot be evenly distributed in the entire paste. Instead, the paste is partially aggregated, and the phenomenon of dry material inclusion results in uneven quality of the entire paste.

1. Temperature;
2. Time;
3. The nature of dry material;
4. Binder.

1. When the mixing temperature is low, the mixing time can be appropriately extended; when the mixing temperature is high, the mixing time can be appropriately shortened.
2. Using a binder with a lower softening point, the kneading time can be appropriately shortened at the same kneading temperature.
3. The more powdery small particles in the ingredients, the longer the kneading time should be properly extended.
4. When adding raw shreds, the kneading time should be extended appropriately.
5. If the machine stops for some reasons during kneading, keep warm and extend the kneading time.

1. Before starting the machine, check the oil quantity of the reducer and the lubrication of the bearings, and check whether all fasteners are loose.
2. After starting, always check the temperature, sound and vibration of the motor, reducer, bearing seat, the rotating parts of the kneading pot should be balanced during operation, no impact sound, no noise from gears, the temperature of each bearing does not exceed 70ºC, and the motor current is stable , Shut down immediately if there is any abnormality.
3. The blanking should be uniform to prevent debris from entering.
4. Stop feeding before stopping, and stop the machine after the material in standby is basically empty.

The most suitable mixing temperature of the paste depends on the softening point of the binder. Generally speaking, the mixing temperature should be 50～80ºC higher than the softening point of the binder. When using medium temperature asphalt, the mixing temperature should be kept at 115. Within ～～150ºC, 130ºC is the most appropriate. Using modified asphalt, the mixing temperature is increased to 160～180ºC.

During the kneading process, the kneading temperature is not allowed to be lowered below the specified level, otherwise the wettability of the binder to the aggregate particles and the fluidity of the paste will be reduced, making kneading difficult. Therefore, when the heating temperature is low, the kneading time should be extended, and the binder should be added after reaching the target. The kneading temperature also has a certain relationship with the climate. The temperature in winter is low, and the paste dissipates quickly after being out of the pot. Therefore, the kneading temperature in winter should be slightly higher than that in other seasons.

If the dry mixing temperature of the dry material is too low, the moisture that has been adsorbed on the surface of the solid carbon raw material particles cannot be removed. This water forms a very strong adsorption layer on the surface of the particles, which will significantly reduce the wetting effect of the asphalt on the solid carbon raw material particles. . If the temperature of the various dry material particles during dry mixing is lower than the temperature of the added liquid asphalt, when the asphalt is in contact with the dry material particles, the temperature of the asphalt will decrease, which will increase the viscosity of the asphalt and make the asphalt more sensitive to the dry material. The wetting and penetrating effects become worse, resulting in poor plasticity of the paste and lowering of the kneading quality of the paste. Therefore, to ensure that the dry mixing temperature of the dry material is close to the temperature of the liquid asphalt, the temperature of the dry material is generally 10ºC lower than the asphalt temperature.

The solid carbon raw material particles and powder together with the binder are stirred at a certain temperature and mixed to form a plastic paste. This production process is called kneading. Kneading plays a role in carbon production up to the following three aspects:

1. Make all kinds of raw materials uniformly mixed, and at the same time make all kinds of particles of different sizes uniformly mixed and filled to form a mixture with a higher degree of firmness.
2. It is convenient for the material and the binder to mix evenly, the liquid binder is evenly coated on the surface of the dry material particles, and all the particles are bonded to each other by the bonding force of the binder, giving the paste a plastic shape.
3. Partially infiltrate the binder into the pores of the dry material particles to further improve the binder properties and the compactness of the paste.

1. The binder composition of the product formula;
2. The nature of the material particles;
3. Molding method.

1. It has good wettability and adhesion to carbon materials, so as to ensure that the paste has good plasticity.
2. The binder should have a higher carbon content and coke reduction rate.
3. The binder should be a thermoplastic material, which is solid at room temperature, melted into a liquid when heated slightly, and hardened immediately after cooling.
4. Wide sources and low prices.

In order to ensure the stability of the particle size of the product ingredients, on the one hand, it is necessary to frequently sample from each storage hopper for screening analysis to check whether the purity of the ingredients fluctuates. If the fluctuation is too large, timely measures must be taken.

On the one hand, it is necessary to regularly take various granular materials from the storage hopper and perform screening analysis according to the percentage composition of the formula to check whether it meets the technical requirements. If it does not meet the requirements, immediately stop the ingredients, update and adjust the formula, or disqualify The batching can be continued until the required materials are discharged. The batching equipment must be checked regularly to maintain the accuracy of the batching to avoid batching errors. The weighing must be carried out in strict accordance with the batching list, and it must be fast and accurate. Can not exceed the specified error.

1) Power outages in the whole workshop

1. Turn off the gas valve immediately;
2. Adjust the negative pressure of the furnace;
3. Ask about the reason for the power outage and the length of the outage time;

2) Sudden power failure of the smoke exhauster

1. Close the gas valve;
2. Find an electrician to activate the spare smoke exhauster;
3. If the standby smoke evacuator fails to start, let the relevant personnel deal with the fault and report to the relevant leaders in time.

1. Stop the exhaust fan, stop the fire and close the butterfly valve at the inlet and outlet of the fan.
2. Find the fire source and extinguish the fire with steam injection or water.
3. After confirming that the fire is extinguished, carry out a test run and resume production.
4. Report to dispatchers and leaders.

1. The temperature of the total flue rises sharply,
2. The current of the smoke exhauster rises and fluctuates greatly, and the negative pressure of the total flue decreases and fluctuates greatly;
3. Exhaust gas cannot be discharged, black smoke is emitted from the furnace chamber, and black smoke is emitted from the chimney.

The process of roasting products is divided into:

1. Warm-up stage;
2. The mid-temperature stage of intensified changes;
3. High-temperature roasting stage;
4. Cooling stage.

The calcined product must ensure that the coal pitch produces the maximum coke precipitation. While producing the maximum coke precipitation, the entire green body is heated uniformly, the correct geometric shape, and no internal and external defects (that is, no internal and external cracks, no carbon in the cross section of the product Uneven degree, no bubbles, etc.).

In the process of pyrolysis and coking of binder coal tar pitch, the main changes with increasing temperature are decomposition and polymerization.

After the carbon product is roasted, the binder in the product is converted into coke, and a coke-carbon grid is formed between the carbon powder particles to connect them closely to form a whole with a fixed geometric shape, certain mechanical properties and physical and chemical indicators.

1. Eliminate volatile matter;
2. Reduce the resistivity to improve the electrical conductivity of the product;
3. Further shrink the volume and change its physical and chemical properties;
4. Create conditions for the graphitization process;
5. Coking the binder coal pitch.

The roasting of the formed raw product is an indirect heating treatment process in the roasting furnace using hot gas as fuel with a protective medium isolated from the air, and at a certain heating rate.

1. The carbon paste is thermoplastic and has a certain viscoelasticity. The ability to transmit pressure is not as good as that of liquids. The pressure in the paste shows a decreasing trend, resulting in uneven green density.
2. The friction between the paste and the mold wall and the friction between the paste particles result in pressure loss, resulting in uneven pressure distribution and uneven density.
3. There are differences in the orientation of the non-equiaxial particles in the paste on the surface and inside of the green body, which affects the uniformity of the green body density.

The green body produced by the new molding machine is made of plastic paste. It contains binder coal pitch to facilitate the viscous state. The shape and size of the green body are not stable. Therefore, the green body should be sprayed with water immediately after leaving the molding machine. Soak in cold water to cool down, so that the temperature of the green body drops below the softening point of the asphalt. The bitumen is cooled again and solidified into a solid state to stabilize the green body so that the green body will not bend and deform. The cooling water temperature should not be higher than 30ºC. Under normal circumstances, large-size blanks are soaked in cold water for 3 to 5 hours, and small and medium-sized blanks are soaked for 1 to 3 hours, and the blanks can be fully cooled. The green body pressed out in summer should be longer to cool down.

1. The filling material on the top of the product is too thin;
2. Some parts of the furnace body leak materials during the high-temperature roasting process. (Main reason)
3. The temperature is too high when it is out of the oven, and the product is too concentrated and cannot be dispersed in time.
4. The filled filler is wet, its volume shrinks after high temperature heating, the top material of the product is reduced, and the lower part causes the product to expose the filler.

1. The duration of the roasting process.
2. The speed of temperature rise;
3. The highest value of temperature;
4. Holding time at the highest temperature.

The purpose is to reduce the horizontal and vertical temperature difference, the inside and outside are heated evenly, and the quality of the roasted product is uniform in all parts.

1. Check the difference between the shift temperature and the physical and chemical temperature, and formulate the temperature rise curve of the shift.
2. Adjust the negative pressure of the flue, pipe, smoke exhauster and gas pressure according to the heating situation.
3. Strictly follow the baking curve control, if it exceeds the allowable fluctuation range, it must be adjusted within 20 minutes.
4. Strictly control the negative pressure, the negative pressure at the inlet of the smoke exhauster should be greater than 2500Pa, the negative pressure of the pipe should be greater than 1000Pa, and the negative pressure of the flue should be controlled in the temperature regulating furnace room, and the control should be 5-25Pa.
5. During the heating process, when the temperature drops due to the stop of oil or other reasons, it is allowed to recover to normal at three times the speed of this temperature range.
6. Pay attention to the temperature rise slowly during the heating process, and sudden rise and fall are strictly prohibited.
7. The smoke from the chimney should be white, and the temperature of the smoke exhauster should be controlled at 120～150ºC.

1. Before installing the furnace, clean the furnace bottom first, spread the saw powder 10-15mm, and put no less than 250mm filler on it.
2. The green body is installed neatly, the distance between the box wall and the product is not less than 60mm, and the thickness of the covering filler is not less than 60mm after the green body is installed, and then the second layer is installed, and the process is repeated until the last layer is installed, covering and filling The thickness of the material is more than 400mm, and the furnace is installed after the powder is covered by 250mm.

1. Draw up the curve according to the different chemical changes of the product at different temperature stages during the heating process.
2. Develop curves according to product types and specifications.
3. Formulate the curve according to the structure of the furnace type.
4. Formulate the curve according to the type of fuel and the type of filler.
5. According to the number of operating chambers of the ring chamber roaster, different curves can be formulated.
6. Different curves are made according to the different forming methods of the green body.
7. Draw up the curve according to the required product output.

1. It does not melt at the highest temperature of roasting;
2. It is not easy to chemically react with products and refractory materials;
3. It should have good thermal conductivity;
4. The volume of the particles should not change significantly when heated;
5. Have a certain granularity;
6. The resources are extensive, cheap, pollution-free, and easy to produce.

Temperature and pressure, filling material, furnace condition, furnace loading quality, nature of green body.

1. Prevent product oxidation;
2. Conduct heat to make the product evenly heated;
3. Fix the shape of the product to prevent deformation of the product;
4. Obstruct the smooth elimination of volatile matter, and at the same time derive the volatile matter.

If the filler is too large, it will easily cause the filler and the product to catch fire, and the oxidized carbon block will be deformed. If the particle size is too small, it is not conducive to product volatile matter discharge, the thermal conductivity is poor, and the filler is easy to agglomerate, and it takes a long time to reach the same temperature.

1. Excessive granularity of the filler can easily cause the filler product to ignite and oxidize, and the carbon block is deformed.
2. The particle size is too small, which is not conducive to the discharge of volatile components in the product, the thermal conductivity is poor, and the filler is easy to agglomerate. It takes a long time to reach the same temperature.

If a fire occurs, stop the smoke exhauster and cooling fan immediately, go to the furnace immediately, close the dead gas valve to cut off the fire source, and then open the connecting flue opening cover to find the fire position. After the fire position is found, use the crane to lift the pipe and use it. Steam or water for fire extinguishing treatment. After the fire goes out, report to the leader or dispatcher, find a maintenance worker, and resume production as soon as possible.

the reason:

1. Because there are too many combustibles accumulated in the smoke exhauster and the fire channel, it will catch fire when encountering an open flame.
2. In normal operation, sometimes the gas volume is opened too large, so that the gas cannot be fully burned in the fire channel, and it is pulled into the flue by the fire, causing a fire.
3. When adjusting the negative pressure, it is raised too much at a time, so that the fire from the volatile matter enters the flue, causing a fire accident.
4. If the flue temperature is too high and exceeds the specified range, it will also cause fire accidents.

Measures:

1. Clean up the remaining materials of the flue and smoke exhauster on a regular basis.
2. Don’t pull the fire during the operation process, make the volatile matter fully burn in the fire channel, and make the chimney emit white smoke or light yellow smoke.
3. The temperature of the fume extractor is controlled below 150ºC.
4. Don’t raise too much at one time when adjusting negative pressure, but strengthen the sense of responsibility.

The exhaust fan extracts the heat from the cooling furnace chamber, and the blower sends air into the furnace chamber. Its functions are different. The exhaust fan extracts the heat from the cooling furnace chamber in order to cool the product, and the blower sends the air. In the cooling furnace chamber, it plays a certain role in cooling down, and can also play the role of secondary air to help the high temperature furnace chamber. The blower is also called the air cooler and the secondary fan. It is set up in the cooling furnace room to blow cold air.

1. Lower the temperature of the furnace chamber after the roasting furnace;
2. Supply hot air after fuel combustion. The suction rack is behind the blower.

It is a medium way to connect the flue and the fire. The pipe has a flap at the connection with the fire, which plays the role of adjusting the negative pressure.

Ignition and starting the furnace is the opposite of stopping the furnace. First, close the butterfly valve of the main flue, start the smoke exhauster, install the burner frame, and all the equipment in place (temperature measurement frame), notify the gas station to send gas, check the gas pressure, and gas release. After everything is normal, adjust the negative pressure of each fire channel to increase the temperature.

The temperature rises too fast, so that quite a lot of hydrocarbons are too late to decompose and polymerize and volatilize away, taking away many carbon atoms that can be called coke, and the coke formation is low. On the other hand, increasing the temperature difference in the furnace chamber causes the product to undergo decomposition and polymerization at different stages, and the internal and external expansion and contraction are inconsistent, causing cracks in the product and affecting product quality. When the temperature rises slowly, the hydrocarbon molecules can have a sufficient time to decompose and polymerize. The amount of coking of the product is thus increased, which can improve the quality of the product.

According to the requirement, the temperature is lowered by 50ºC per hour to 80ºC. If the temperature drops too fast, the product will cause breaks, cracks, and waste products.

The product has high mechanical strength, good product quality, convenient temperature adjustment and control, high heat utilization rate and high output.

1. When moving the pipe, move quickly.
2. The furnace room must maintain a certain negative pressure.
3. Effective measures must be taken when the gas pressure is lower than the requirement.

Oxidation is related to the heat treatment temperature, impurity content, completeness of the lattice structure, porosity, gas pressure and other factors.

1. The upper insulation material of the product is too thin.
2. Material leakage in the furnace room and ventilation of the motor box.
3. The filling material has too much moisture, the blanking is not solid, and the product shrinks and sinks during baking to expose the product to oxidation.
4. The temperature is too high when it is out of the oven, and the product is not scattered in time at the cleaning site.

Generally speaking, due to the above process, the products often produce transverse cracks and internal cracks. However, due to the reasons of this process, the products are often caused to produce longitudinal rows. The causes of various cracks are as follows:

1. The material temperature is too low during molding, the pre-pressure is insufficient, and the molding pressure is insufficient.
2. The paste will be broken during the return stroke. Although the surface is smooth after pressing, the internal structure is not good.
3. The degree of calcination of the raw materials is not enough, or the ingredients are mixed into the raw meal block, and the secondary shrinkage occurs during roasting.
4. The plunger head of the press is coated with too much oil, and the joints of the two pot materials cannot be adhered, and cracks occur after baking.
5. The product has too little binder content and too much powder content.
6. The paste is not uniformly kneaded or there is water in the paste.
7. The heating rate is too fast.
8. The product is too close to the furnace wall when it is installed.
9. Part of the furnace wall leaks material and heats up too fast.
10. The upper layer is equipped with large specifications (above ¢400mm) and less ash products.

Longitudinal cracks, permanent cracks, internal cracks, delamination, impurities, shorts, deformation, bending, oxidation, damage, high resistivity and other waste products will be produced.

1. Stop the smoke exhaust machine, and the gas will accumulate into explosive gas.
2. Extinguish at low temperature, the temperature is too low, the flame is not extinguished, and the gas accumulates to form explosive gas.
3. The operation of low-temperature ignition is incorrect. In the case of sufficient air, ignition should be performed first, and then gas should be sent, otherwise there is a danger of explosion.

In order to ensure the stability of the particle size of the product ingredients, on the one hand, it is necessary to frequently sample from each storage hopper for screening analysis to check whether the particle size of the ingredients fluctuates. If the fluctuation is too large, timely measures must be taken.

On the other hand, it is necessary to collect various granular materials from the storage hopper regularly (after every few pots of materials are prepared according to the regulations). Perform screening analysis according to the percentage composition of the formula to check whether it meets the technical requirements. If it does not meet the requirements, immediately stop the batching, re-adjust the formula, or discharge the unqualified materials until it meets the requirements, and then continue the batching. The batching equipment should be checked regularly to maintain the accuracy of the batching to avoid batching errors. Weighing must be carried out in strict accordance with the ingredients list, and must be fast and accurate, and cannot exceed the specified error.

The furnace body of the retort furnace can generally be used for about 8 years. The main phenomenon of the early damage of the tank body is the formation of pores on the brick surface of the tank body, which gradually expand into karst caves, and even burn through the wall of the tank. Wear the same, in addition, there are often phenomena such as falling off of burner bricks in the fire channel and blockage of the fire channel by molten slag.

There are four reasons for the early failure of the retort furnace:

1. Masonry quality. Poor masonry quality is manifested by large brick joints, uneven width of brick joints and insufficient mortar. The special-shaped silica bricks are not pre-built or pre-built carelessly after the tank is built. Deviation of the size from the design requirements, uneven expansion joints, mud falling into the fire channel and not cleaned, the furnace body being wet, raining and freezing during masonry, etc., will affect the life of the furnace body.
2. The heating rate of the furnace is inappropriate, the furnace heating is too fast, the furnace body expansion is not well managed during the furnace process, and the various parts of the furnace body cause unbalanced stress, and the furnace body deforms or cracks after the furnace.
3. The quality of silica bricks, the loose structure of silica bricks, large porosity, low mechanical strength, substandard refractoriness, and brick deformation and size substandard quality defects will cause early damage to the tank.
4. Production operation: non-compliant operation during calcination will cause local temperature to be too high (especially when calcination of high volatile petroleum coke), local sintering of silica brick masonry, abnormal feeding and discharging, and fluctuation of material surface , The improper handling of the coking in the tank after blocking the furnace, or even the phenomenon of “fire”, will damage the tank body. Therefore, extending the life of the retort furnace requires strict control in terms of furnace design, material preparation, infrastructure construction, ovens and production operations. During the calcination process, the charging and discharging and the temperature of the furnace must be adjusted according to regulations to avoid local overheating. The phenomenon. It is necessary to take measures in time if the tank body is partially damaged, so as to extend the life of the furnace body.

The paste is off-white, with many small pieces and less large pieces. The divergent paste indicates that the amount of binder is small, the paste is dark and bright, there are many large pieces, and the small pieces are small, indicating that the amount of binder is large, and the size of the paste is half the size. . The bulk is 50～70mm, indicating that the amount of binder is moderate.

At the beginning of the cooling stage, the temperature of the product actually continues to rise. If the cooling rate is too fast, it will cause cracks, increase in waste, and slow cooling. It will also cause the internal and external shrinkage of the product to be inconsistent and cause the product to crack. The furnace body also has an adverse effect, so the cooling rate should be controlled within 40～50ºC per hour, down to 800ºC, and let it cool naturally. There are also actions based on daily output requirements and furnace cycle.