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1. What are the requirements for the drainage of heating furnaces? Drainage from heating furnaces is extremely important; it must be given due consideration during their design. The following requirements must be met: (1) No rainwater should accumulate on the roof or other parts of the heating furnace. (2) The welds of the furnace top steel plate that are in contact with the furnace lining should be fully welded to prevent rainwater from leaking in. (3) Drainage and waste discharge measures should be considered at the bottom of the furnace and around the heating furnace. 2. What are the conditions for using spring hangers? Here, the spring hangers refer to those used on the oil transfer lines subjected to incoming radiation. The usage condition is as follows: when the radiant furnace tube is a socket tube, a spring hanger should be installed on the oil transfer line that receives radiation in order to bear the weight of this line, thereby allowing the radiant inlet tube to expand freely without bending. Spring hangers are not provided in other cases. VIII. Burners 3. How are burners classified? In tubular heaters, the combustion of liquid or gaseous fuels takes place through burners. To ensure proper combustion of fuel, various types of burners are available today, depending on the properties of the fuel and the requirements for combustion. (1) Classified by ventilation method: there are natural ventilation burners and forced-air burners. (2) Classified by fuel type: there are gas burners, liquid burners, and oil-gas combined burners. ①Gas burners are further divided into: external mixing burners – where the gas is ejected first and then mixed with air, resulting in a longer flame. Premixed burner – all air or partial air (semi-premixed) is mixed with gas first before being injected into the furnace for combustion. ②Liquid burners (classified by atomization method): file:///C:\Users\Blackfox\AppData\Local\Temp\ksohtml\wpsD9F8.tmp.jpg 4. What is the importance of burners? In tubular heating furnaces, heat is generated by burners, and this heat is then transferred to the oil through the furnace tubes; therefore, the relationship between the flame and the furnace tubes becomes a key issue in such furnaces. A burner is a device that supplies heat; it is also a device that consumes energy. The quality of burner design, selection, manufacturing, and operation is directly related to the thermal efficiency of the heating furnace as well as the length of its operational cycle. It is incomplete and even unrealistic to discuss the quality of a heating furnace in isolation from the burner. 5. What are the basic requirements for burners? Burners are one of the key components of tubular heating furnaces, and their quality has a direct impact on the heating efficiency of the furnace as well as on the manufacturing process. Therefore, the following requirements are imposed on burners: (1) To meet the needs of different types of furnaces and to ensure the necessary heat intensity in the furnace chamber. (2) To maintain continuous and stable combustion, there must be a flame of a certain shape and length, one that is steady and does not go out. The flame is orange-yellow in color, with a low likelihood of tempering or decarburization. (3) The excess air coefficient is low, ensuring complete combustion as well as thorough and uniform mixing of the fuel gas with air. (4) For liquid burners, it is capable of uniformly atomizing various fuel oils within the required adjustment range. (5) Meets process requirements, offers great operational flexibility and good adjustability; it is simple and reliable to operate, and produces no noise during operation. (6) No clogging, no oil leakage, no coking. (7) Simple structure, compact design, small size, and light weight. (8) Low operating costs, and easy to maintain and replace. 6. What are the components of an oil-gas combined burner? What is the function of each component? Tubular heating furnaces commonly use oil-gas combined burners, which consist of three parts: an oil nozzle, a gas nozzle, and a flame channel (see Figure 8-1). file:///C:\Users\Blackfox\AppData\Local\Temp\ksohtml\wpsD9F9.tmp.jpg (1) Function of the nozzle: Steam and fuel oil mix inside the nozzle and are then ejected from it; the small holes in the nozzle are arranged in a circle, causing the oil to be sprayed in the form of a conical mist. (2) Function of the gas nozzle: 8 gas pipes are arranged in a circle, and the gas is ejected through the nozzle. (3) Function of the flame channel: Composed of two layers of flame channel bricks, it creates a high-temperature zone within the flame channel to stabilize the combustion flame ； Ensure good mixing of air and fuel ； The two layers of firebrick allow for separate secondary air supply; the primary air enters through the inner layer of firebrick, and there is an air regulator at the air supply point ； The secondary air enters from the inside of the outer firebrick passage through the secondary air regulator. If the primary air regulator is opened wider and the secondary air regulator is closed tighter, the flame will be shorter; conversely, the flame will be longer. 7. What are the characteristics of oil-gas combined burners? Oil nozzles and gas nozzles are present in oil-gas combined burners. Petrochemical plants generate a large amount of fuel gas on-site, and they aim to burn it all off; for any shortfall in heat, fuel oil is used to make up for it. Therefore, oil-gas combined burners are generally used. This burner can burn oil alone, burn gas alone, or burn a mixture of oil and gas. However, when burning a mixture of oil and gas, poor mixing of the fuel with air results in a longer flame with poor shape; therefore, it is best for one burner to burn only one type of fuel. Oil and gas are both available; it is possible to use oil alone in some burners and gas alone in others. When burning two fuels simultaneously, measures should be taken to maintain a constant load for one fuel, while using the other fuel to control the temperature of the medium inside the furnace tube. When operating on gas alone for an extended period without using oil, the oil guns should be removed or a small amount of steam should be introduced to prevent them from being damaged. The air regulator and flame channel of the oil-gas combined burner are designed for the maximum energy of one type of fuel. If the total amount of fuel oil and gas burned in a burner is too high, natural ventilation combustion can result in insufficient air supply, incomplete combustion, and an excessively long flame. 8. What fuels are commonly used in heating furnaces? The common fuels for tubular heating furnaces in petroleum chemical plants are fuel oil and fuel gas. The fuel oils used in refineries are all heavy oils produced on-site, such as vacuum residue, atmospheric heavy oil, cracking residue, and residues from other units; among these, vacuum residue is the most commonly used. The fuel gas used in refineries is divided into refinery fuel gas and fuel gas produced by the facilities. Refinery fuel gas is a mixture of fuel gases from various units, and its composition and properties vary significantly depending on the characteristics of the crude oil, the processing procedures, and the operating conditions. Refinery units that produce large amounts of fuel gas include catalytic cracking, thermal cracking, coking, and platinum reforming. 9. What conditions are necessary for fuel combustion? Two conditions are required for the combustion of fuel: one is air (oxygen) ； Second, there must be a ignition source or heat; both conditions are essential. 10. What is the purpose of installing flame arresters on gas pipelines? Whether it’s high-pressure or low-pressure gas, under normal operating conditions, as long as no air mixes into the gas pipeline and the gas is discharged at a certain pressure, flames will not travel back into the pipeline. However, during startup or shutdown procedures, if there is air present in the pipeline, or if air leaks into it due to loose flanges or malfunctioning valves, it may cause flames to re-enter the pipeline and spread throughout the entire piping network and equipment, leading to an explosion. Therefore, flame arresters must be installed on gas pipelines. In gas pipelines, multi-layer copper wire meshes or flame arresters are generally used. The copper wire meshes dissipate heat and cool down the area, preventing the flame from spreading to the other side. A water-sealed flame arrester can also be used to prevent tempering.