Coke reactivity
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To measure the reactivity of coke, granular or block samples are often used. The reactivity measured in this way is the bulk reactivity, which is usually expressed by the weight loss rate after the reaction. Influencing factors Under certain reaction conditions, coke reactivity is mainly affected by the properties of the coking coal, the coking process, the structure of the resulting coke, and the composition of the coke ash. (1) Properties of coking coal. It is the most important factor affecting the reactivity of coke. Coke reactivity is related to the coalification degree of the raw coal used. Coke made from coal with low coalification degree has high reactivity; as the degree of coalification deepens, the reactivity of the resulting coke gradually decreases. When the wet and ashless carbon content (C ratio) of the coal reaches 89-91%, the reactivity of the coke produced is the lowest. At this time, the flammable volatile matter (I: dar) of the coal is approximately equivalent to 18-28%. Coke made from coal with medium and high carbon content has a low reaction rate. Therefore, more low-volatile coal and medium-volatile coal should be used in coking raw coal, and less high-volatile coal should be used. This is the fundamental way to reduce the reactivity of coke. Gasified coke and ferroalloy coke require high reactivity and should be equipped with more high-volatile coal. Adding petroleum delayed coke to coal can increase the cracking carbon in the later stage of coking and block some tiny pores in the coke, which helps to reduce the reactivity of the coke. Under the condition that the coal has sufficient cohesiveness, adding delayed coke with a volatile content of 5 to 10% and a volatile content of 9 to 13% can reduce the reactivity of the resulting coke by approximately 10 to 20%. This measure is often used in the coal blending scheme for the production of foundry coke. (2) Coking process. Increasing the final coking temperature can reduce the reactivity of coke. Under the same raw coal conditions, the reactivity of coke with a final coking temperature of 1100°C is about 10% lower than that of coke with a final coking temperature of 1000°C. There is a period of temperature maintenance time at the end of coking, which can also slightly reduce the reactivity of coke. Increasing the bulk density of the furnace coal and adjusting the particle size composition of the furnace coal can make the coke pores evenly distributed and also have the effect of reducing the reactivity of the coke. Dry coke quenching avoids the impact of water vapor on coke pores 3V] The surface reaction reduces the activation points and helps to reduce the reactivity of coke. _ (3) Coke structure. Coke optical structure is directly related to reactivity. The order of reactivity of various optical tissues is basically: the reactivity of optically inactive inert tissue and isotropic tissue is higher than that of anisotropic tissue; in anisotropic tissue, mosaic tissue is higher than fluid tissue; in mosaic tissue, fine-grained mosaic tissue is higher than coarse-grained mosaic tissue. Figure 2 shows the relationship between the optical anisotropic structure content of coke and the reactivity of coke (expressed by mass loss after reaction). Another coke structural parameter that affects reactivity is the specific surface of the coke. (See coke pore structure) For pores smaller than 10 m, although the pore volume only accounts for 10% of the total pore volume of coke, its specific surface accounts for more than 95% of the total specific surface of coke. The reactivity of coke increases with the increase of pore specific surface, so pores less than 10 Qing in coke play an important role in reactivity. (4) Coke ash composition. The metal oxides in coke ash have a positive catalytic effect on the c-reactivity of coke, especially K and Na, which have a greater catalytic effect. (Figure 3) Generally, the KZo and Na content in coke is very small, only 0.1 to 0.3%; however, due to the alkali circulation in the blast furnace, the K and Na content adsorbed by the coke can reach more than 3%, which will cause damage to the coke. Since the reaction of coke with 02 and H20 has a similar law to the C reaction, most * * The reaction characteristics between coke and coZ are used to evaluate the reactivity of coke. A long time ago, some * * The oxidation reaction characteristics (or combustibility) of coke and air have been used to evaluate the reactivity of coke. (See Charcoal Combustibility) The reaction between coke and COZ is a gas-solid phase reaction, and its reaction rate depends not only on the chemical reaction speed, but also on diffusion factors. Therefore, coke reactivity is related to coke particle size, pore structure, optical structure, specific surface, ash composition and content, etc.; it is also changed by the conditions used in the measurement, such as reaction temperature, reaction gas composition, reaction gas flow rate and pressure. Therefore, to evaluate the reactivity of coke, tests must be conducted under specified conditions. (See lump coke reactivity index and post-reaction strength and Layan reactivity test) Characteristics of the reaction between coke and CoZ Block or granular coke is a porous body, and its reaction process with coke is affected by both temperature and the diffusion resistance of gas in the pore body. When the temperature is lower, the chemical reaction speed is slower, and the C molecules pass through the coke 3V0%199%12] During the process of diffusion from the surface to the inside of the pores, the C concentration does not change much and the diffusion resistance is very small. Therefore, the chemical reaction speed is the dominant factor in the reaction process; as the reaction temperature increases, the chemical reaction speed accelerates, and the stomata surface is quickly covered by the CO generated by the reaction, which increases the resistance of C molecules to diffuse into the pores. The coke block produces a large coZ concentration gradient from the surface to the inner layer. At this time, the entire reaction is mainly controlled by diffusion resistance; the reaction temperature continues to rise, and the reaction speed increases sharply. As soon as the coke molecules contact the coke, they react quickly on the surface and have no time to diffuse into the pores. At this time, the reaction is completely controlled by the mass transfer effect of the outer surface of the coke. The above characteristics indicate that the nature, state and reaction conditions of coke have an impact on the reaction rate. Determination method Since coke is a carbonaceous porous body containing ash, it is related to c. The Poisson reaction is not exactly the same as the reaction between elemental carbon and COZ. In order to explore the reaction kinetics of coke and Cq, the influence of gas diffusion should be eliminated, and fine-grained coke samples with particle sizes ranging from hundreds of microns to tens of microns need to be used. Usually, only a few milligrams of sample are used for measurement on a precision thermal balance, and the reaction temperature can be selected according to the purpose of the experiment. In order to eliminate the influence of ash, coke can also be deashed before measuring the reactivity. The reactivity of coke measured by a thermal balance is generally expressed in terms of the loss per unit mass of coke after reaction per unit time (called reaction rate). Industrially...
Thank you, sir, but can you send it as an attachment? I can’t see the picture.
The coke reactivity and post-reaction strength tester produced by Shangyu Hongxing Machinery Instrument Manufacturing Co., Ltd. does a good job in the constant temperature zone.
Shangyu Hongxing Machinery Instrument Manufacturing Co., Ltd. is the only one in China that has drafted and revised GB/T4000-2008 "Coke Reactivity and Post-Reaction Strength Test Method"* * The standard will be officially implemented on April 1, 2009! Coke reactivity and post-reaction strength test method 1. Method introduction: Weigh a certain mass of coke sample and place it in the reactor. After reacting with carbon dioxide for 2 hours at 1000±5°C, the coke reactivity (CRI %) is expressed as the percentage of coke mass loss. After the reaction of the coke, after the type 1 drum test, the coke with particle size greater than 10mm accounts for the mass percentage of the reaction coke. Represents post-reaction strength (CSR %). 2. Test instruments, equipment and materials 1. The structure of the electric furnace is shown in Figure 1. The inner diameter of the furnace is 140mm, the outer diameter is 160mm, and the height is 640mm (high aluminum outer wire tube). High-temperature iron-chromium-aluminum alloy resistance wire, with a maximum operating temperature of 1400 ℃. The diameter is 2.8mm. During installation, the upper mouth of the furnace is open, and casters are installed on the bottom plate in advance. Lay a layer of refractory bricks on the bottom, and place the outer wire tube wound around the electric furnace wire vertically in the center of the bottom plate. (cut from 3-inch lightweight high-aluminum bricks), fill the gap between the outer wire tube and the furnace shell with lightweight high-alumina brick prefabricated parts (standard-sized furnace wires are led from the upper and lower ends, and the lead-out parts are well protected with single-hole insulating tubes. A diameter is pre-drilled close to the furnace wire so that they cannot overlap each other, and are connected to the insulator fixed on the furnace shell. furnace wire to avoid short circuit. The 8mm hole in the insulation brick outside the outer wire tube has a depth of 350mm from top to bottom. Bury the thermoelectric corner casing, cover the upper cover, insert the temperature control corner, and connect the electric furnace with the temperature controller and power supply. After each electric furnace is installed, set the constant temperature zone so that the length of the 1100±5°C temperature zone in the furnace is greater than 150mm 2. The reactor structure is shown in Figure 2 and is made of high-temperature resistant alloy steel (GH23 or GH44). Type I drum: The device is shown in Figure 3. The rotation speed is 20±l.5r/min. 3. Post-reaction strength test equipment ① Type I drum: The device is shown in Figure 3, the rotation speed is 20±1.5r/min. a. drum body: It is processed from seamless steel pipes with a diameter of 140mm and a thickness of 5~6mm. b. reducer: Speed ratio 50 (WHT08 type) · c. motor: 0.75kw, 910r/min (Y905-6) ②Rotating drum controller: The total number of revolutions is 600r, and the time is 30minr. 4. Carbon dioxide supply system ① Carbon dioxide cylinder and oxygen pressure gauge. The carbon dioxide content in the cylinder is greater than 98%. ②Rotameter: 0.6m3。 ③Gas cleaning bottle: The volume is 500mL, containing concentrated sulfuric acid (p = 1.84g/mL). ④drying tower: Volume: 500mL, containing anhydrous calcium oxide. ⑤buffer bottle: Volume 6000mL. 5. Nitrogen supply system ① Nitrogen cylinder and oxygen pressure gauge. The nitrogen content in the cylinder is greater than 98%. ②Rotameter: 0.25m3/h。 ③Gas cleaning bottle: The volume is 500mL, containing an alkaline solution of pyrogallic acid. Preparation method: 59 Pyrogallic acid is dissolved in water, 489 potassium hydroxide is dissolved in 32mL of water, and the two are mixed. Pay attention to prevent air oxidation when preparing. ④Drying tower: The volume is 500mL, containing anhydrous calcium chloride block. ⑤ When using high-purity nitrogen (nitrogen content 99.99%), neither a gas scrubbing bottle nor a drying tower is required. 6. Temperature control range of precision temperature control device: 0～1600 ℃, accuracy ±5 ℃, without isolation transformer. 7. Gas analyzer A simple gas analyzer or other instrument for accurately measuring carbon dioxide content. 8. The round hole sieve has one each of 18mm, 15mm, 10mm, 5mm, 3mm and 1mm, and the screen frame diameter is 200mm. One each for 21mm and 25mm, the screen surface is 400mm×500mm, and it is manufactured according to the provisions of Article 4.2 of round hole screen in GB/T06. 9. The volume of the drying oven working room is not less than 0.07m3 10. The weighing on the pallet balance is 0.5~5009. 11. Infrared light bulb 220V, 250W 12. Platinum germanium-platinum thermoelectric corner 0.5mm in diameter and 700mm in length. High-aluminum thermocouple protection tube. High-aluminum double-hole insulating tube. High-aluminum single-hole insulating tube 13. , Sieve plate temperature 0 ~ 300 ℃. The material is high-temperature resistant alloy steel (GH23 or GH44), with a thickness of 3mm and a diameter of 79mm. Holes with a diameter of 3mm are drilled evenly on it with a spacing of 5mm. 14. The diameter of the high aluminum ball (corundum ball) is 20mm. 15. The bracket is shown in Figure 4. The material is Q235A, and the material of the three branch pipes is IGrl8Ni9Ti. Figure 4 Bracket 16, reactor bracket holds the reactor, the size and form are arbitrary. 3. Sample collection and preparation 1. According to the sampling method specified in GB1997, take 20kg of coke larger than 25mm in proportion, and discard the bubble coke and burner coke. Crush and mix evenly with a jaw crusher, reduce to 10kg, and then screen it with a 25mm or 21mm round hole screen. The coke larger than 25mm is crushed and screened again. Take out the 1mm sieve and remove the flake coke and strip coke. Divide the coke into Zkg and divide it into two times (1kg each time). Place it in an R-shaped drum and rotate it for 50r at a speed of 20r/min. , take it out and then sieve it with a 21mm round hole sieve, reduce the material on the sieve to 900g as a sample, use the quartering method to divide the sample into four parts, each part is not less than 220g. The coke of the test coke oven can be prepared with coke of 40mm-50mm particle size. 2. Put the prepared sample into a drying oven and dry it at 170~180°C for 2 hours. Take out the coke and cool it to room temperature. Weigh 2009±0.5g for later use. 4. Test steps The test process is shown in Figure 5. 1. Spread a layer of high-aluminum balls about 100mm high at the bottom of the reactor, and lay a sieve plate flat on top. Then load the prepared coke sample 2009 ±0.5g. Pay attention to the height of the high aluminum ball adjusted before loading the sample so that the coke layer in the reactor is within the constant temperature zone of the electric furnace. Insert the thermowell connected to the upper cover into the center of the material layer. Use screws to secure the cover to the reactor barrel. Place the reactor on a bracket on the top of the furnace and hang it in the electric furnace. Place an asbestos board between the bracket and the electric furnace cover for heat insulation. Place high-alumina lightweight bricks around the reactor flange (cut from standard-sized high-alumina bricks, of any size) to reduce heat dissipation. 2. Connect the reactor air inlet pipe and exhaust pipe to the gas supply system and exhaust system respectively. Insert the temperature measuring thermocouple into the reactor thermocouple sleeve (the thermocouple is protected by a high-aluminum double-hole insulating tube and a high-aluminum thermocouple protection tube). Check the air path to ensure it is tight. 3. Turn on the power and use a precision temperature control device to adjust the electric furnace heating. First use manual adjustment, and the current is gradually adjusted from small to large within a few minutes to the maximum value, and then set the button to the automatic position. The heating rate is 8~16℃/min. When the center temperature of the material layer reaches 400°C, nitrogen gas is passed at a flow rate of 08L/min to protect the coke and prevent it from burning. 4. When the center temperature of the material layer reaches 1050°C, turn on the infrared lamp and preheat the outlet of the carbon dioxide cylinder. When the center temperature of the material layer reaches 1100°C, cut off the nitrogen and switch to carbon dioxide. The flow rate is 5 minutes and the reaction is 2 hours. After passing carbon dioxide, the temperature of the material layer should return to 1100±5 ℃ within 5 to 10 minutes. 5 minutes after the reaction starts, take gas from the exhaust system for analysis, and then take it every half hour to analyze the carbon monoxide or carbon dioxide content in the gas after the reaction. 5. React for 2 hours and stop heating. Cut off the carbon dioxide gas line, switch to nitrogen gas, and control the flow rate at 2 minutes. Unplug the exhaust pipe. Quickly take out the reactor from the electric furnace, place it on the stand and continue to circulate nitrogen to cool the coke below 100°C. Stop flowing nitrogen, open the upper cover of the reactor, pour out the coke, screen, weigh and record. 6. Put all the reacted coke into the I-type drum and rotate it at a speed of 20r/min for 30 minutes. The total number of revolutions is 600r. Then take out the coke, screen it, weigh it, and record the quality of each screen grade. 7. The sieved composition obtained during the test, the gas composition after the reaction, and other observed phenomena should be recorded in detail according to the original record sheet and analyzed as a reference for a comprehensive investigation of the coke properties. 8. The original test data is recorded in the format shown in Table 1. 5. Calculate the coke reactivity index from the test results and express the lost coke mass as a percentage of the total mass of the coke sample before reaction· Coke reactivity CRI % according to (l)