Thread Content
Heating Furnace Technology Questions and Answers Question 1: What are the three forms of heat transfer? Explain each of these three different forms of heat transfer. answer: The three basic forms of heat transfer are conductive heat transfer, convective heat transfer and radiation heat transfer. conduction heat transfer: Heat is transferred from a high-temperature part of an object to a low-temperature part, or from a high-temperature object to a low-temperature object between two objects in direct contact ； This process continues until the temperature of all parts of the object or contacting objects is completely uniform, a process called heat conduction. Convection heat transfer: The heat transfer method that uses the movement of fluid (liquid and gas) particles to transfer heat from one part of the space it occupies to another is called convection heat transfer. radiation heat transfer: The process in which the heat of an object is transferred in the form of radiant energy without passing through any medium is called radiative heat transfer. Question 2: What are the chemical reactions of combustion? answer: The combustion reaction formula of carbon is: C＋O₂→CO₂ ； The combustion reaction formula of 2C＋O₂→2CO hydrogen is:: The combustion reaction equation of sulfur in 2H₂＋O₂→2H₂O fuel is:: S＋O₂→SO₂Question 3: What components does the flue gas discharged from the heating furnace chimney consist of? Why is there so much nitrogen and oxygen in it? answer: The composition of flue gas includes carbon dioxide, water vapor, sulfur dioxide, oxygen, nitrogen, as well as carbon monoxide and hydrogen produced when combustion is incomplete. Reasons why flue gas contains large amounts of nitrogen and oxygen: Nitrogen is brought in by the air required for combustion and does not participate in the reaction ； Oxygen comes from excess air. Question 4: What is the combustion process? answer: The combustion process of fuel is a process in which carbon and hydrogen in the fuel react with oxygen in the air to generate carbon dioxide and water and release heat. Question 5: What are the three elements of combustion? answer: The three elements of combustion are a certain temperature, air (oxygen) and combustible materials. Question 6: What is high calorific value? What is low calorific value? answer: Low calorific value refers to the heat released when the water produced is in gaseous state after complete combustion of unit mass of fuel. ； High calorific value refers to the heat released when the water produced is in a liquid state after complete combustion of unit mass of fuel. Question 7: What is heat load? answer: The effective heat transferred to the heated medium per unit time is called heat load. Question 8: What is the thermal efficiency of a furnace? answer: The fuel consumption index of the heating furnace is expressed by the thermal efficiency of the whole furnace, that is, the ratio of the effective heat load of the whole furnace to the total calorific value of the fuel. The higher the thermal efficiency, the higher the effective utilization of fuel and the lower the combustion consumption. If the air supply is insufficient, fuel combustion will be incomplete and some unburned fuel will leave the furnace. ； If the excess air coefficient is too large (that is, too much air volume), the heat taken away by the flue gas will increase, which will lead to a reduction in the thermal efficiency of the furnace. Question 10: What is the working principle of the heating furnace? answer: Gas or fuel oil burns in the furnace and releases heat. The radiant chamber mainly transfers heat through radiation, and the convection chamber mainly transfers heat to the furnace tube through flue gas convection. ； The furnace tube then transfers heat to the materials in the tube through conduction and convection. Question 11: What is excess air coefficient? How does it relate to the thermal efficiency of the heating furnace? answer: The ratio of actual air volume to theoretical air volume is called excess air coefficient. The excess air coefficient reflects the actual amount of air entering the furnace: When its value is too large, although it can ensure complete combustion of the fuel, it will increase the heat taken away by the flue gas and reduce the thermal efficiency of the heating furnace. ； If the value is too small, there will be insufficient oxygen supply for fuel combustion, which may lead to incomplete combustion and the production of carbon monoxide, which will increase fuel consumption. Therefore, controlling the appropriate excess air coefficient is crucial to ensuring the thermal efficiency of the heating furnace. Question 12: How is the heat load of the heating furnace distributed? In what way is heat transferred? answer: The heat load (effective heat transfer amount) of the heating furnace is usually 70%-80% of the total heat load of the furnace, borne by the radiation chamber, 20%-30% by the convection chamber, and the radiation chamber is the main heat transfer area. The radiation chamber uses radiation heat transfer as the main method, and the convection chamber uses convection heat transfer as the main method. Question 13: What components does the structure of the heating furnace consist of? answer: The structural components of the heating furnace include chimneys, flue baffles, convection tubes, return elbows, explosion-proof doors (balls), radiant tubes, furnaces, shells, furnace walls, oil and gas combined burners and bases. Question 14: How is the heating furnace divided into upper, middle and lower parts? What are the main components of each part? answer: The heating furnace is generally divided into three parts: upper, middle and lower. The lower part is the radiation chamber, the middle part is the convection chamber, and the upper part is the chimney. The radiant chamber is usually also called the furnace, with radiant furnace tubes arranged inside and a certain number of burners distributed at the bottom or sides. ； The convection chamber is located in the upper part of the radiation chamber and generally consists of convection tubes, air preheaters, etc. The convection chamber of the heating furnace usually does not have a separate waste heat boiler. Its structure is often composed of the superheating section, evaporation section and economizer of the waste heat boiler. The chimney is located above the convection chamber and consists of a flue baffle and a chimney body. Question 15: Why does a heating furnace need to be equipped with an explosion-proof door? answer: When flammable gas or incompletely burned gas accumulates in the furnace, the volume will suddenly expand when encountering a fire source, causing the pressure in the furnace to increase. ； Or the pressure in the furnace increases due to overload operation of the furnace. The explosion-proof door can automatically open to release pressure when the pressure exceeds the threshold to avoid damage to the furnace body and ensure the safety of the equipment. Therefore, an explosion-proof door needs to be installed. Question 16: What is the principle of chimney draft? answer: The chimney suction force is due to the high temperature and low density of the flue gas inside the chimney, while the air outside the chimney is low in temperature and high in density. The two form a pressure difference - that is, the external air pressure at the bottom of the chimney is higher than the flue gas pressure at the same level in the chimney. This pressure difference provides a driving force for air to enter the furnace and for flue gas to be discharged. Theoretical derivation shows that the chimney suction force is equal to the product of the chimney height and the density difference between air and smoke. When the height of the chimney is fixed, the suction force will fluctuate significantly due to atmospheric temperature and seasonal changes. Therefore, a flue baffle is usually installed at the entrance of the chimney to adjust the smoke exhaust capacity and keep the suction force stable. For example, in winter, the temperature is low and the pumping force is large. ； In summer, the temperature is high and the pumping force is small. Therefore, the process conditions are not file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps1.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps2.jpg变时，夏季应将烟道挡板开大，冬季则适当关小。第17题：加热炉负压的产生机制及负压操作的原因是什么？答：炉内烟气与空气因密度差异，借助高大烟囱形成抽力，在此抽力作用下炉内产生负压。 The size of negative pressure has a significant impact on operation: When the negative pressure is too large, too much air enters the furnace, and the oxygen content of the flue gas increases, which not only reduces the thermal efficiency of the furnace, but also accelerates the oxidation of the furnace tube. ； If the negative pressure is too small, the amount of air entering the furnace will be insufficient, resulting in incomplete fuel combustion and also reducing thermal efficiency. Therefore, the heating furnace needs to operate under appropriate negative pressure conditions. Generally, it is more appropriate to control the negative pressure of the heating furnace within the range of -20 to -40 Pa (i.e. 2 to 4 mmH₂O). Question 18: What requirements should a reasonable heating furnace design meet? answer: (1) The heat intensity on the surface of the radiant tube must meet the optimal design value ； (2) The furnace volume should be compact and reasonable ； (3) The heat transfer distribution ratio between the radiation chamber and the convection chamber must be appropriate. ； (4) The structure inside the furnace must be simple and practical ； (5) The size, wall thickness and material of the furnace tube must be selected scientifically and rationally. Question 19: Why does a new heating furnace need to be baked before it is put into use? answer: The refractory material of the newly built heating furnace has a high water content. If the temperature suddenly rises when it is put into use, the moisture in the refractory material will rapidly vaporize and expand in volume, which may cause the refractory lining and refractory bricks to crack and fall off, affecting the start-up period and normal production. Therefore, the moisture in the refractory material must be gradually evaporated and dried through the oven process. Question 20: What are the oven steps for building a new heating oven? answer: The oven needs to follow the principle of slow heating, and the daily heating rate of the oven should not exceed 150-200°C. When the furnace temperature reaches 130°C, keep the temperature constant for two days to remove surface water ； When the temperature rises to 320°C, keep the temperature constant for one day to remove the crystal water in the refractory material. ； When the temperature reaches 500°C, the temperature is kept constant for one day to complete the sintering of the refractory bricks and clay. When the furnace temperature rises to 400-500°C, in order to avoid dry burning damage to the furnace tube, fluid (such as steam, nitrogen) needs to be introduced into the furnace tube, and the fluid flow rate is determined according to the tube wall temperature. Question 21: How many stages does the oven have? What are the temperature control and time requirements for each stage? answer: The oven is divided into four stages: natural ventilation maintenance, heating, heating, dehydration and sintering, and stewing. The specific requirements are as follows: (1) First open the flue baffle, fire hole, air door and entrance hole, and allow natural ventilation for 2-3 days ； Then close the inlet, fire hole and damper, and adjust the flue baffle opening to 1/3 ； (2) Pass the steam heater through the furnace tube for 1-2 days (for the steam oven method) ； (3) During the heating stage, the heating rate is controlled to 5°C/h ； (4) When the furnace temperature reaches 130℃, keep the temperature constant for 2 days to remove surface water ； (5) Heating to 320 at a speed of 7℃/h℃ ； (6) Keep the temperature at 320°C for one day to remove crystal water ； (7) Heating to 500 at a speed of 10℃/h℃ ； (8) Maintain constant temperature at 500℃ for one day to complete sintering ； (9) Then cool down to 250℃ at a speed of 15℃/h, turn off the heat and simmer in the oven ； (10) When the furnace temperature drops to 100°C, open the damper and flue baffle for natural ventilation and cooling. The entire oven process takes about 10 days. Question 22: What are the principles and requirements for heating furnace operation? answer: (1) Use the combustion method of multiple burners, short flames, and all flames to ensure that the flame does not directly attack the furnace tube and prevent local overheating. ； (2) Strictly control the furnace outlet temperature in accordance with the process indicators. Frequent inspection, detailed analysis, and steady adjustment should be carried out during operation. ； (3) The number of burners and valve position opening should be adjusted in time according to the furnace load to ensure that the pressure behind the gas valve is greater than 0.07MPa to prevent backfire or automatic interlocking of the furnace. ⑷ The furnace should maintain an appropriate negative pressure while maintaining a clear and bright flame with normal flame conditions. ⑸ If black smoke or weak flame occurs when burning oil, you should turn on the atomized steam appropriately. ； If the flame is suddenly large and small, you can open a larger oil valve or reduce the amount of atomized steam. ⑹ When burning gas, if the flame is weak and swinging, and the color is dark red, it is necessary to increase the opening of the flue baffle or damper. ； If the flame is too long, you can increase the damper opening or close the flue baffle appropriately. ⑺ Check whether the furnace tubes and elbow boxes are deformed, and whether the colors of the furnace walls, pipe racks, and pipe hooks are basically the same. ； If local redness occurs, it is a sign of local overheating. Question 23: What does the "three doors and one plate" of the heating furnace mean? What impact does the flue baffle and air door opening of the heating furnace have on the operation? answer: The "three doors and one plate" of the heating furnace refer to the throttle (including fuel gas valve), steam valve, damper and flue baffle. The opening of the heating furnace flue baffle and air door will affect the flue gas flow in the furnace and the suction force in the furnace. When the opening is large, the suction force increases, the amount of heat taken away increases, the heat loss increases, and the efficiency of the heating furnace decreases. ； At the same time, the amount of excess air increases, and excessive air entering the furnace will cause the furnace tube to oxidize and peel, shortening the service life of the furnace tube. If the baffle opening is too small, the fuel combustion will be incomplete, smoke will appear in the furnace, and even positive pressure flashback will occur. If the damper opening is too small, the amount of air entering the furnace will be insufficient, the flame will be soft and scattered, the combustion will be incomplete, the carbon monoxide content in the flue gas will increase, the fuel consumption will increase, and the thermal efficiency of the furnace will decrease. Therefore, in actual operation, it is necessary to closely coordinate the adjustment of the damper and flue baffle to ensure that the furnace has a certain suction force and control a reasonable excess air coefficient to improve thermal efficiency and extend the service life of the heating furnace tube. In actual operation, operators should comprehensively judge the adjustment direction of the damper and flue baffle by observing parameters such as flame color, furnace pressure, and flue gas oxygen content to ensure that combustion is in the best state. Question 24: Under what circumstances should the flue baffle and burner damper be adjusted? answer: ⑴ When the flame combustion condition is not good and the furnace is dark, the flue baffle and damper should be opened appropriately. ⑵ When the furnace is abnormally bright and white and the flue temperature is low, it indicates that the excess air coefficient is too large, heat is lost from the chimney, and the furnace tube is prone to oxidation and peeling. At this time, the flue baffle and damper need to be closed. ⑶ When the flame attacks the furnace, fluctuates, burns incompletely, flashes white or sparks, the burner damper should be adjusted appropriately. ； When strong winds blow, the damper and flue baffle need to be properly closed. Question 25: What should you pay attention to when operating ignition? How to avoid backfire and hurt people? answer: ⑴ The flue baffle must be installed correctly and maintained at 1/3 opening. ⑵ Before igniting, steam should be blown into the furnace for 10-15 minutes until steam comes out of the chimney. ⑶ When using diesel to ignite the ignition rod, the operator must stand on the upwind side, with the body sideways towards the burner, and the face must not be facing the burner to prevent backfire and injury. ⑷ The permanent lamp should be lit first, and then the main burner ； The furnace needs to maintain a certain negative pressure during ignition. ⑸ If the flame goes out and needs to be re-ignited, the burner gas valve should be closed immediately, blow steam into the furnace for 5-10 minutes and then re-ignite. ⑹ After ignition, make sure the burner burns normally before leaving. Question 26: What are the causes of tempering in heating furnaces? answer: ⑴ Backfire during ignition is usually caused by the presence of flammable gas in the furnace, loose sealing of the gas valve, failure of the flue baffle to open or insufficient opening, or excessive force when opening the gas valve. ⑵ When igniting or closing a gas fire, excessive opening of the primary air damper can easily cause backfire, and abnormal gas pressure may also cause backfire. ⑶ The furnace is overloaded and the flue gas cannot be discharged in time, resulting in positive pressure operation. file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps3.pngfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps4.jpg。⑷ A large amount of fuel oil is sprayed into the furnace, or the gas or liquid hydrocarbons are seriously contaminated with oil. Question 27: How to prevent backfire in heating furnace? answer: ⑴ It is strictly forbidden to use gas with serious oil content. ⑵ Be clear about the position of the flue baffle and be careful not to close it to a small opening when adjusting. ⑶ Do not overload operation, ensure normal combustion, bright furnace, and maintain negative pressure operation in the furnace. ⑷ Strengthen equipment inspection and maintenance, and promptly replace or repair gas valves with loose seals ； Check the temperer regularly and repair or replace it in time if it is found to be malfunctioning. ⑸ Inspection is required before starting the furnace and igniting. The furnace must be purged with steam for 10-15 minutes until steam comes out of the chimney. ； After the flame goes out, the furnace must be purged with steam before re-igniting. Question 28: Why does the furnace have positive pressure and what is the reason? answer: ⑴ When the furnace is filled with oil and gas, ignition will cause the oil and gas to accumulate and expand, resulting in positive pressure and backfire. ⑵ Under normal circumstances, the furnace negative pressure is -20~-40Pa. If combustion is poor and the flue gas cannot be discharged in time, the furnace negative pressure will gradually turn to positive pressure, causing air to not enter normally, thus interrupting the combustion process. ⑶The furnace is overloaded. ⑷Gas carries oil or fuel oil flow suddenly increases. ⑸The flue baffle or damper opening is insufficient, resulting in insufficient suction power. Question 29: What does inspection and maintenance include during normal operation of the heating furnace? answer: ⑴Check the combustion status of the burner in the furnace and whether the color of the flame, furnace and furnace tube is normal. ⑵Check whether the temperature of each measuring point of the furnace is stable and within the index range. ⑶Check the deoiling and dehydration of the gas tank. ⑷Check whether the gas tank pressure and the pressure behind the furnace gas valve are stable. ⑸Check whether the instrument indication is accurate and whether the control valve is flexible and reliable. ⑹Check whether the stove and its components and accessories are in good condition. ⑺Carry out maintenance work on furnaces, fuel tanks, pipeline valves and other equipment to ensure smooth operation ； Fill in operation records and shift handover logs promptly and accurately ； Keep the equipment and surrounding area sanitary. Question 30: In what range is the excess air coefficient usually controlled when the heating furnace is operating? What effect does the excess air coefficient have on the heating furnace? answer: When the heating furnace is operating, the excess air coefficient when burning gas is generally controlled between 1.1 and 1.25, and when burning fuel oil, the excess air coefficient is controlled between 1.2 and 1.5. If the excess air coefficient is too small, it will lead to incomplete fuel combustion and cause fuel waste. ； If the excess air coefficient is too large, there will be too much air entering the furnace, which will cause the temperature of the furnace to drop, reduce the heat transfer efficiency, increase the heat taken away by the flue gas, and the furnace tube is prone to oxidation and peeling. When the excess air coefficient is too large, the flue baffle and damper can be appropriately closed ； If the excess air coefficient is too small, the flue baffle and damper can be opened appropriately. Question 31: How do changes in air volume and climate affect furnace operation? (The flame state, thermal efficiency, and furnace tube oxidation need to be considered) Answer: Climate change directly affects the air volume and heat dissipation of the furnace. When it's windy or rainy, the air volume increases, the flame turns white, and the furnace outlet temperature drops. ； If the furnace outlet temperature is kept constant, the flue temperature will rise, the heat dissipation of the furnace body will increase, the thermal efficiency of the furnace will decrease, and the furnace tube will be easily oxidized and peeled. Therefore, excessive air volume will affect furnace operation. If the air volume is too small, the flame will burn incompletely, the flame will turn red, and the furnace will become dark. ； If the furnace outlet temperature is maintained unchanged, the furnace temperature will rise and the thermal efficiency will decrease. file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps5.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps6.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps7.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps8.png第32题：如何判断加热炉燃烧状况是否良好？答：燃烧完全的表现为：炉膛明亮，燃烧燃料气时火焰呈蓝白色，燃烧燃料油时火焰呈黄白色；各火嘴火焰大小均匀，互不干扰，实现多火嘴、短火焰、齐火苗；火焰不扑炉管，烟囱排烟无色；仪表盘显示的炉出口温度记录曲线近似直线，波动范围为±1℃；炉子运行时发出均匀的轰鸣声。出现上述现象，表明加热炉燃烧状况良好。第33题：提高加热炉热效率的措施有哪些？答：⑴确保燃料完全燃烧。⑵在保证完全燃烧的前提下，降低过剩空气系数，合理调节“三门一板”（油门、汽门、风门、烟道挡板）。⑶优化烟气余热回收设施的操作，如空气预热器、余热锅炉等。⑷加强设备管理，保证炉体严密，避免炉壁耐火层出现裂缝、塌陷等缺陷，保持其完整性；减少下回弯头箱、人孔、看火窗等处的空气泄漏，降低热损失；对炉体裸露部分（包括对流转辐射段及下部回弯头段）加强保温，防止热损失过大。⑸防止炉管结焦。⑹对于燃烧燃料油的加热炉，应加强对流室吹灰；辐射室在大检修时需进行烧焦及盐垢清洗，以提高传热效率。 Question 34: What is the role of measuring flue gas temperature and flue pressure? answer: ⑴It can understand how much heat is taken away by the flue gas, which provides a basis for saving fuel, reducing heat loss, and preventing oxidation and peeling of the furnace tube. ⑵It can judge the flame combustion state and detect whether there is secondary combustion phenomenon in time. ⑶It can predict whether the furnace tube is coked and whether the convection chamber is dusty. Question 35: How to control the heating furnace outlet temperature? answer: ⑴Ensure stable pressure of fuel oil, gas and atomized steam. ⑵Keep the feed amount and feed temperature stable. ⑶Regularly perform water cutting operations on high-pressure gas tanks and low-pressure gas tanks. ⑷When adjusting the flame, the principle of "small adjustment, slow adjustment, and frequent observation" should be followed to avoid flame interference with each other, ensure normal combustion of the flame, and uniform heating in the furnace. ⑸Reasonably control instrument parameters to ensure frequent adjustment and timely and accurate response. ⑹During thunderstorms, you need to pay attention to changes in operating conditions and make timely adjustments. Question 36: What are the causes of temperature fluctuations in heating furnaces? answer: Reasons include: ⑴Fuel gas (or fuel oil and atomized steam) pressure fluctuations, composition changes and fuel gas liquid. ⑵The feed amount, feed temperature, and fuel properties change, and the feed oil contains water. ⑶Air and climate change. ⑷The instrument displays abnormally, the parameter settings are unreasonable, or the instrument fails. ⑸Burner nozzle is scorched causing the flame to go out file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps9.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps10.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps11.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps12.jpg灭。处理措施：保持燃料压力与雾化蒸汽压力稳定，调整燃料用量，加强燃料气罐脱液操作，确保平稳运行，维持工艺参数稳定。根据气候变化及时调整加热炉操作，联系仪表维修人员检修仪表并调整仪表参数，清理火嘴后重新点燃。 Question 37: What impact do changes in feed volume and feed temperature have on the operation of the heating furnace? answer: During normal production, if the feed amount suddenly increases, the furnace outlet temperature will immediately drop. ； The feed amount decreases and the furnace outlet temperature increases. file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps13.png升；进料温度上升，炉出口温度随之上升；进料温度下降，炉出口温度亦下降（进料量及进料温度变化直接影响炉膛温度与炉出口温度）。第38题：瓦斯切水不净会产生哪些现象？答：瓦斯切水不净会引发缩火、回火、闪火，加热炉各点温度（尤其是炉膛与出口温度）急剧下降，火焰发红，带水过多时火焰会熄灭。 Question 39: Why can’t you bring oil when burning gas? How to prevent gas from carrying oil? answer: Oil in the gas will directly affect the temperature of the furnace and outlet. In severe cases, the heating furnace will smoke a lot, produce positive pressure backfire, and even oil leakage from the bottom of the furnace will catch fire. Preventive measures: Regularly check the liquid level of the gas tank and cut off the water, and supply steam to the heating pipe of the gas tank. Question 40: How to switch between burning gas and burning fuel oil? answer: When switching from burning gas to burning fuel oil, you need to turn on the fuel oil heating line first. After cutting the water in the fuel oil tank, lead the fuel oil to the front of the furnace, and at the same time lead the atomized steam to the front of the furnace. ； Switch the furnace outlet temperature control from automatic to manual, and switch the temperature control switch from fuel gas to fuel oil ； Then turn on a small amount of atomized steam, slowly close the gas valve, and then slowly open the fuel oil valve to keep the furnace outlet temperature stable until the gas valve is completely closed. Finally, switch the main regulator of the instrument from manual to automatic control. When switching from burning fuel oil to burning fuel gas, it is necessary to switch the furnace outlet temperature control from automatic to manual ； Lead the gas to the front of the furnace to ensure that the oxygen content of the gas is less than 1% ； Then slowly close the fuel oil and atomization steam valves, and at the same time slowly open the fuel gas valve to keep the furnace outlet temperature stable. ； Switch the temperature control switch to the fuel gas position until the fuel oil and atomization steam valves are completely closed, and finally change the instrument to cascade control. Question 41: Briefly describe the normal shutdown steps? answer: ⑴According to the process requirements, the temperature is cooled at a prescribed rate. During the cooling process, the number of burners is gradually reduced until all flames are extinguished. ⑵After the heating furnace is turned off, open the large damper to cool down naturally. If necessary, open the flue baffle to speed up the cooling. ⑶Process fuel oil valves and gas lines according to process requirements: The fuel oil system is purged to the fuel tank with steam, the gas system closes the main valve, discharges the residual pressure to the flare, and finally purges it clean with steam. Question 42: How to deal with heating furnace feeding interruption? answer: ⑴Immediately turn down the fuel valve and control the small flame. ⑵Strengthen monitoring of furnace and furnace outlet temperatures to prevent furnace overheating. ⑶Resume feeding as soon as possible and keep process media flowing when conditions permit. ⑷After the feed is restored, the temperature is raised to the process index according to the normal heating rate. Question 43: How to deal with insufficient or interrupted heating furnace fuel gas? answer: ⑴Contact production dispatch to restore system fuel gas pipeline network pressure stability as soon as possible. ⑵Adjust the amount of self-produced fuel gas and increase the output of self-produced fuel gas as much as possible. If necessary, adjust process operations to increase the amount of self-produced fuel gas. ⑶If the heating furnace has stalled, it is necessary to close each burner valve, purge the furnace with steam and then re-ignite. Question 44: Furnace load file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps14.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps15.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps16.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps17.jpg变化如何调节？答：在保证炉出口温度稳定的前提下，炉膛四角温度需随负荷变化保持均匀，严禁file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps18.png急剧波动。降负荷时，根据降量幅度逐步关小火嘴，当关至极限时，为防止缩火需停掉多余火嘴，同时及时调节风门与烟道挡板。提负荷时，根据提量幅度逐步开大火嘴或增加火嘴数量，同步调节风门与烟道挡板以满足提量需求。 Question 45: Why is it stipulated that the furnace temperature of the heating furnace should not exceed 800°C? answer: Because when the furnace temperature exceeds 800°C, the heat transfer and thermal intensity of the radiant tube will increase, and the oil in the tube will easily coke. ； In addition, the temperature resistance of the furnace tube material does not exceed 800°C, otherwise the furnace tube is prone to damage. Question 46: What should be done when the furnace negative pressure is too large or positive pressure appears? Answer: The excessive negative pressure in the furnace is due to the excessive opening of the flue baffle, which results in excessively high negative pressure in the furnace, causing a large amount of air to leak into the furnace. This not only reduces the thermal efficiency, but also easily causes oxidation and peeling of the furnace tube, thereby shortening the service life of the furnace tube. It is necessary to close the flue baffle in time and maintain the furnace negative pressure at 2-4mm water column. The occurrence of positive pressure in the furnace is mostly caused by the small opening of the flue baffle or the overload operation of the furnace. At this time, the stove is likely to cause safety hazards. The flue baffle should be opened in time to make the negative pressure value reach the standard. In addition, if the convection chamber has not been cleaned for a long time and the dust and scaling are serious, it will easily lead to positive pressure in the furnace. Soot blowing measures need to be taken to reduce the resistance of the convection chamber. Question 47: How to deal with excessive pressure drop in the convection chamber? answer: Excessive pressure drop in the convection chamber is mainly caused by serious dust accumulation in the convection tube, so soot blowing operations need to be carried out in time. ； For heating furnaces without fixed soot blowing devices, soot can be blown into the convection chamber through temporary steam pipes to reduce the pressure drop in the convection chamber. Question 48: How to deal with excessive carbon monoxide content in flue gas? answer: For a complete combustion furnace, there should be no carbon monoxide in the flue gas. If carbon monoxide is detected in flue gas analysis, it indicates incomplete combustion and chemical incomplete combustion loss. The main reason is poor atomization effect of the burner or insufficient air supply. When the furnace is dark, the flame is red, or the chimney emits black smoke, carbon monoxide must be present in the flue gas. It is necessary to adjust the "three doors and one plate" to improve the atomization conditions and ensure complete combustion of the burner. When chemical incomplete combustion occurs, combustible gases will be produced in the flue gas, mainly including CO, H₂, and may contain a small amount of CH₄. In incompletely burned flue gas, CO and H₂ have a certain structural relationship and will not appear alone. ； If there is CO in the flue gas, it must be accompanied by H₂. Therefore, both CO and H₂ are unfavorable factors that restrict the improvement of thermal efficiency. Usually, when the CO content is less than 1%, CO/H₂=3.6 ； When the CO content is greater than 1%, CO/H₂=2. Question 49: What should be done when the oxygen content and carbon monoxide content in the flue gas are both high? answer: The cause of this phenomenon is insufficient air supply at the burner and poor atomization effect, resulting in incomplete combustion and the production of carbon monoxide. ； The high oxygen content in the flue gas is due to the loose sealing of the upper part of the furnace body and air leakage into the furnace. The combustion problem needs to be solved first, and the air supply volume should be appropriately increased to ensure complete combustion of the burner. ； Secondly, it is necessary to strengthen the sealing of the furnace body to reduce unnecessary air leakage. file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps19.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps20.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps21.jpg第50题：加热炉壁温超高的原因及处理方法是什么？ answer: If the wall temperature is extremely high due to the small opening of the flue baffle and low furnace negative pressure, the "three doors and one plate" need to be adjusted to maintain the furnace negative pressure at 2-4mm water column. If the wall temperature is extremely high due to poor insulation of the furnace body, it is necessary to re-insulate the furnace body during maintenance, or fill refractory ceramic fibers in brick joints and expansion areas to reduce the furnace wall temperature to below 40°C. file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps22.png Question 51: What operating problems does heating furnace smoke reflect? answer: If the stove emits a small amount of smoke, if it is burning oil, it is usually caused by insufficient steam, poor atomization effect, incomplete combustion or imbalance of the oil-steam ratio of individual burners. ； A large amount of black smoke may be caused by excessive oil volume, instrument failure, drop in steam pressure, or burnout of the furnace tube. ； risk * * Improper operation of the smoke system and the flame extinguishing from time to time lead to incomplete combustion ； Gray smoke is caused by oil in the gas or a sudden increase in flow. Question 52: What is the reason for the fluttering and weak flame? answer: The reason why the flame is fluttering and weak is that there is insufficient air volume, so the primary and secondary dampers need to be opened appropriately. Question 53: What is the reason why the flame turns white, hard, flashes and jumps? answer: The flame is white and hard, which is caused by too much steam or too much air. ； Flame flashes and jumps for reasons including: ⑴ Oil and gas valve opening is too large ； ⑵ Fuel pressure fluctuates sharply and regularly. Question 54: How should I adjust it when the color in the furnace is too dark and there is a lot of smoke? answer: Observation found that the color of the furnace was too dark, indicating insufficient combustion. ； A lot of smoke means that the chimney has insufficient suction power or the air volume in the furnace is too small. At this time, it is necessary to open the large air door or flue baffle appropriately. Question 55: How to deal with the flame rolling up and down in the furnace? answer: ⑴ Open the damper to increase the amount of air to ensure complete combustion ； ⑵ Open the flue baffle appropriately to increase the amount of smoke emitted and promote complete combustion. ； ⑶ Reduce gas flow ； ⑷ If this phenomenon is caused by gas carrying oil, gas deoiling operations need to be strengthened. Question 56: What causes smoke from the heating furnace chimney and how to deal with it? answer: reason: ⑴ Heating furnace tube burned through ； ⑵ The feeding amount of the heating furnace suddenly increases ⑶ The heating furnace has insufficient suction power and insufficient excess air. ⑷ The fuel oil pressure rises sharply and the fuel-to-steam ratio is unbalanced, resulting in incomplete combustion. ⑸ The properties of the fuel oil change, such as the viscosity increases, and the atomization effect becomes worse. ⑹ Atomization steam pressure drops or is interrupted. Treatment measures: ⑴ When the furnace tube burns through, perform the furnace tube rupture treatment process. ⑵ When the feed volume suddenly increases, contact the operator to adjust the operation to ensure stable flow. ⑶ When the excess air coefficient is insufficient, open the air inlet door or flue baffle to increase the excess air coefficient. ⑷ If the rise in fuel oil pressure is caused by instrument failure, switch the instrument control mode from automatic to manual. ⑸ When the properties of fuel oil change, the ratio of oil to steam should be appropriately adjusted to ensure normal atomization and increase the temperature of the fuel oil. ⑹ When the atomizing steam pressure drops or is interrupted, the heating furnace switches to burning external gas, top oil, pentane oil or liquefied gas. file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps23.jpg Question 57: What are the causes of furnace tube coking? answer:⑴ The furnace tube is heated unevenly, and the flame hits the furnace tube directly, causing local overheating of the furnace tube. ⑵ The feed amount is too small and the oil stays in the furnace tube for too long. ⑶ The furnace temperature is too high, causing the oil to coke. ⑷ The coke layer remaining in the furnace tube produces an induction effect and accelerates the formation of new coke. Question 58: What is localized overheating? What are the dangers of local overheating? answer: When peeling, white spots, spots, etc. appear on the furnace tube, it is determined to be local overheating. Local overheating can easily cause furnace tubes to rupture and a large amount of oil and gas to leak out, which can lead to furnace tube explosion accidents. Question 59: How to deal with a ruptured heating furnace tube? answer: ⑴ Turn off the heating furnace immediately, close the fuel valve, open the flue baffle, and close the air inlet door. ⑵ Stop feeding and drain the medium in the furnace tube as much as possible. ⑶ Perform depressurization operations on the system. ⑷ If the situation is serious, report the fire alarm promptly. Question 60: What are the standards for furnace tube replacement? answer: ⑴ It needs to be replaced when bubbling, cracks or network cracks appear. ⑵ The horizontal furnace tube needs to be replaced when the curvature between two adjacent brackets is greater than 1.5-2 times the outer diameter of the furnace tube. ⑶ The furnace tube needs to be replaced due to severe corrosion and peeling, and the tube wall thickness is less than the calculated allowable value. ⑷ It needs to be replaced when the outer diameter increases by 4-5% compared with the original outer diameter. ⑸ The expansion port has been expanded repeatedly and needs to be replaced when it exceeds the specified expansion value. ⑹ The expansion port needs to be replaced if it corrodes or falls off, or if the exposure of the expansion port is less than 3 mm. Question 61: What is the reason why the gas burner cannot ignite and how to deal with it? answer: reason: ⑴ The pumping force is too small. ⑵ The nitrogen content in the gas is too high. Treatment method: ⑴ Close the flue damper and air inlet door. ⑵ Replace non-combustible gas and increase gas concentration. Question 62: How should the heating furnace be operated when there is strong wind or rainy weather? answer: When the wind force is small, it will have little impact on the operation of the heating furnace. ； When the wind is strong, the flue baffle and air inlet door need to be properly closed to prevent the heating furnace from stalling due to excessive suction force and affecting normal operation. On cloudy and rainy days, the air pressure is low and the chimney suction force is affected. It is necessary to open the flue baffle appropriately to enhance the chimney suction force to ensure normal operation. Question 63: What should you pay attention to when operating during thunderstorms? answer: Thunderstorm days are accompanied by wind, rain and lightning, which can easily cause power outages and have a greater impact on operations. Pay special attention during operation, anticipate accidents, and prepare emergency response measures. Question 64: What are the ways to recover waste heat from heating furnace flue gas? answer: Heating furnace flue gas waste heat recovery absorbs flue gas heat through low-temperature thermal media, which can greatly improve heating file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps24.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps25.jpg热炉热效率，具有显著节能效果，具体途径包括以下三种：1. Make full use of the convection chamber to heat the process media. 2. Preheat the furnace combustion air through the air preheater. 3. Use waste heat boiler to generate steam. Question 65: What type of heat pipe air preheater does this device use? How it works file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps26.png是什么？答：本装置采用热虹吸式热管空气预热器。该设备是高效回收烟气余热的设施，由一组密封管段构成。首先将密封管段内空气抽尽，充入定量液体（通常称为工质，石油化工加热炉所用热管式空气预热器一般以水为工质，采用钢管制造，工质水的使用温度通常可达300℃）。工作时，管外热介质（烟气）流过时，热量传递给管内的水，使水受热蒸发并流向管段另一端（冷端）；在冷端，水蒸气热量被冷空气吸收后冷凝，冷凝水借助热管自身倾斜度（倾角通常为10—15°）依靠重力返回蒸发段。此过程持续循环，实现冷热介质的换热。 Question 66: What type of heating furnace is suitable for using a waste heat boiler to recover flue gas waste heat? answer: The waste heat boiler recovery flue gas waste heat plan needs to be formulated based on the steam supply and demand conditions of the entire plant or the device. It is usually suitable for heating furnaces with high exhaust gas temperatures and large heat loads. Generally speaking, when the main furnace exhaust temperature and the medium temperature are higher than 500°C, the benefits of installing a waste heat boiler to produce steam are more significant. If the heat load of a single heating furnace is small, multiple furnaces can be combined to carry out waste heat recovery work. The waste heat boiler of the reforming device in this workshop realizes waste heat utilization by recovering the concentrated flue gas from the four-in-one heating furnace. Question 67: How does low-temperature dew point corrosion in heating furnaces occur? What are the dangers? answer: The fuel oil or fuel gas used in the heating furnace contains a small amount of sulfur, and the sulfur will generate sulfur dioxide (SO₂) during the combustion process. Due to the furnace design and operation requirements to maintain a certain excess air coefficient, excess oxygen is present in the combustion chamber. Under normal excess air coefficient conditions, about 1% to 3% of the SO₂ generated by combustion will further react with excess oxygen to form sulfur trioxide (SO₃). When the flue gas temperature is high, SO₃ gas will not cause corrosion to metals ； But when the flue gas temperature drops below 400°C, SO₃ will combine with water vapor to generate sulfuric acid vapor. The reaction formula is as follows: SO₃↑ + H₂O↑ —— (below 400℃) → H₂SO₄↑ If the exhaust temperature of the heating furnace continues to decrease, the generated sulfuric acid vapor will condense on the heating surface at the rear of the furnace, causing low-temperature sulfuric acid corrosion. The sulfurous acid gas generated by the combination of SO₂ and water vapor usually does not condense in the furnace due to its low dew point temperature and is not harmful to the furnace. With the development of heating furnace energy-saving technology, the exhaust gas temperature requirements are continuously lowered, creating conditions for the generation and condensation of sulfuric acid steam. This kind of corrosion often occurs on the heat exchange tube surfaces of waste heat recovery equipment such as air preheaters and waste heat boilers. In severe cases, it can cause corrosion and perforation of the heat exchange tube bundle in less than one year of operation, affecting the normal operation of the heating furnace. It can be seen that low-temperature dew point corrosion has become the main obstacle to reducing exhaust gas temperature and improving thermal efficiency. Question 68: What are the measures to prevent and mitigate low-temperature dew point corrosion in heating furnaces? file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps27.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps28.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps29.jpg些？答：鉴于低温露点腐蚀已成为进一步降低加热炉排烟温度、提升热效率的主要障碍，防止与减轻该腐蚀已成为行业普遍关注的问题。目前常用的措施如下：1. Increase the air temperature at the inlet of the air preheater, or reasonably control the wall temperature of the heat exchange surface in the design ； 2. Use corrosion-resistant materials ； 3. Promote low-oxygen combustion, strictly control the amount of excess combustion air, and reduce the generation of SO₃ ； 4. Use low-sulfur fuel to lower the flue gas dew point temperature and reduce low-temperature corrosion. Question 69: What are the quality requirements for boiler feed water (deoxygenated water)? Why? answer: The quality requirements for boiler feed water (deoxygenated water) are as follows: Hardness ≤0.005mg equivalent file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps30.png/升；溶解氧≤0.015mg/升；pH值8.5—9.2（最低不小于7）；含油量≤1mg/升；含铜量≤0.01mg/升；含铁量≤0.05mg/升；总CO₂量≤6mg/升；SiO₂≤100μg/升；电导率≤5μS/cm；联氨0.02—0.05mg/升。天然水中含有较多钙、镁化合物（主要包括Ca(HCO₃)₂、Mg(HCO₃)₂、MgSO₄、CaSO₄），此类水被称为硬水。硬水易产生水垢，不适宜直接作为锅炉用水，必须经过软化处理。若余热锅炉使用未经软化的硬水，水中的Mg(HCO₃)₂、Ca(HCO₃)₂在加热煮沸后会分解生成CaCO₃、Mg(OH)₂沉淀，在高温下附着于锅炉壁形成水垢，导致传热性能下降，易引发局部过热甚至爆炸事故。因此，余热锅炉必须使用达到质量指标的软化水。此外，水中溶解的氧气在加热过程中会逐渐析出，高温下的氧气会腐蚀金属设备，引发安全事故。故余热锅炉用水不仅需软化，还需进行脱氧处理，以保障锅炉的安全稳定运行。 Question 70: Why does a waste heat boiler need to be boiled before it is put into operation? What cleaning agent is used? What are the design flow, pressure and temperature of steam drum V308? answer: During the assembly and manufacturing process of waste heat boiler system components, oil and other sediments will remain or adhere to them. In order to avoid foam and droplets during operation of the equipment, it is necessary to thoroughly clean the oil stains and lubricating grease on the surface of the waste pot parts. ； Therefore, the boiling operation must be performed before the waste heat boiler is put into operation. There are many types of reagents used in cooking stoves, the following two are commonly used: ⑴ A mixture of soda ash (Na₂CO₃) and caustic soda (NaOH) in equal proportions, add 6kg of this mixture per cubic meter of cooking water ； ⑵ A mixture of trisodium phosphate and caustic soda in equal proportions, add 4.8kg of this mixture per cubic meter of water. The design parameters of steam drum V308 are as follows: Boiler feed water flow 28983kg/hr, temperature 120℃, pressure 5.6MPa ； The medium pressure steam flow is 27603kg/hr, the temperature is 472℃, and the pressure is 4.21MPa. Question 71: How many desuperheaters does the reformer waste heat boiler system include? What are their respective functions and working principles? answer: The reforming unit waste heat boiler system is equipped with two desuperheaters, namely surface desuperheater ME301 and water spray desuperheater ME302. The function of ME301 is to reduce the temperature of the 472°C superheated steam generated by the waste heat boiler to 450°C, and then send it to the medium-pressure steam pipe network for use by the circulation compressor. Its working principle is: Cooling is achieved by exchanging heat with part of the boiler feed water at 104°C. The superheated steam travels through the shell process and the boiler feed water travels through the pipe process. ； The amount of boiler feed water entering the equipment is adjusted through the ME301 outlet temperature to control the cooling effect. The function of ME302 is to decompress the medium-pressure steam with a pressure of 3.82MPa and a temperature of 450°C to 0.98MPa, and then further cool the superheated steam to file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps31.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps32.jpgfile:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps33.jpg250℃的低压蒸汽。 Question 72: Why does a waste heat boiler need to be drained? answer: When steam is generated in the steam drum of a waste heat boiler, various impurities in the steam drum will be concentrated. Concentrated impurities will aggravate problems such as boiler scaling, corrosion, and steam-water azeotrope. Therefore, part of the concentrated water must be discharged from the boiler to remove suspended solids, salts, dissolved solids, water slag, iron slag and other sediments in the boiler water, so that the boiler water quality reaches the specified standards. file:///C:/Users/lenovo/AppData/Local/Temp/ksohtml10716/wps34.png锅炉排污是保障锅炉正常运行的必要措施，需予以重视。 Question 73: What are the types of sewage discharge methods for steam drums? How to operate and control? answer: Steam drum blowdown can be divided into two categories: intermittent blowdown and continuous blowdown according to the operation time. Intermittent blowdown is also called periodic blowdown, that is, the accumulated water slag and dirt are discharged from the bottom of the boiler at regular intervals. ； Usually the sewage is discharged every 8-24 hours, each time lasting 0.5-1 minute, and the sewage discharge rate is not less than 1%. Intermittent blowdown is suitable for frequent and short periods of time, which can make the boiler water evenly concentrated and help improve steam quality. Continuous blowdown refers to the continuous discharge of concentrated boiler water. The main purpose is to prevent the boiler water from having excessive salt and sulfur content. ； The blowdown parts are mostly located in the area where the boiler water is most concentrated, that is, 200-300mm below the drum water level. The continuous blowdown volume is usually adjusted based on the boiler water quality analysis indicators. Question 74: What are the phenomena, causes and treatment measures of bursting of waste heat boiler furnace tubes? answer: The phenomenon of bursting of waste heat boiler tubes: ⑴ When the degree of explosion is minor, the sound of steam will be emitted from the rupture, and white smoke will emit from the chimney. ； ⑵ When the explosion is severe, there will be an obvious explosion sound and white smoke will emit from the chimney. ； ⑶ Boiler water level, steam pressure and flue gas temperature drop rapidly. Cause analysis: ⑴ The hardness of the water supply exceeds the standard, causing scale to accumulate on the pipe wall ； ⑵ The sediment in the water is not removed in time through regular sewage discharge. When the cold water mixture rises, it carries the sediment, causing pipe blockage. The pipe cannot be fully cooled and overheats and explodes. ； ⑶ The pipe has corroded and its wall thickness has become thinner, making it unable to withstand the original design operating pressure. ； ⑷ The pipe wall is thinned due to dust wear, or there are defects such as slag inclusions and delamination, or the welding quality is unqualified. ； ⑸ The start-up process was not operated according to the regulations, and the temperature and pressure were raised too quickly, resulting in uneven stress and heating of the equipment, and damage due to stress concentration. ； ⑹ Water is released too early or the cooling rate is too fast when shutting down the furnace ； ⑺ When the boiler is severely short of water, the pipes overheat and burst due to lack of water cooling. Precautions: ⑴ Strengthen water quality management, closely monitor water levels during operation, and carry out regular sewage discharge operations ； ⑵ Strictly follow the operating procedures when starting and stopping work. Treatment measures: If the furnace tube of the waste heat boiler bursts, it should be reported to the relevant departments in time for coordinated handling. ； When the situation is serious, emergency shutdown procedures must be followed. Question 75: What are the types of waste heat boiler shutdowns? What situations do they apply to? answer: Waste heat boiler shutdowns are divided into two categories: normal shutdown and emergency shutdown. Normal shutdown refers to a planned shutdown operation, which is usually performed during a comprehensive overhaul of the device or a systematic overhaul of the heating furnace. Emergency shutdown is an emergency shutdown operation taken when the waste heat boiler cannot maintain normal operation due to sudden equipment failure or abnormal operating conditions. It often occurs in emergencies such as furnace tube rupture, severe water shortage, damaged water supply pump and inability to switch to standby.