Causes and solutions of coking in the hottest heat

Causes and solutions of coking in heat transfer oil furnace

there are three main chemical reactions in the heat transfer process of hot oil furnace: thermal oxidation reaction, thermal cracking and thermal polymerization reaction Coking results from thermal oxidation and thermal polymerization

the thermal polymerization reaction occurs because the heat transfer oil furnace is heated during the operation of the heating system. This reaction will produce macromolecular high boiling substances such as polycyclic aromatic hydrocarbons, colloids and asphaltenes, which will gradually deposit on the surface of the heater and pipeline to form coking

the thermal oxidation reaction mainly occurs because the heat transfer oil furnace in the expansion tank of the open heating system contacts the air or participates in the circulation. This reaction will generate low molecular or high molecular alcohols, aldehydes, ketones, acids and other acidic components, and further generate viscous substances such as colloids and asphaltenes, and finally form coking; Thermal oxidation is caused by abnormal conditions. Once it occurs, it will accelerate thermal cracking and thermal polymerization, rapidly increase viscosity, reduce heat transfer efficiency, and cause overheating and furnace tube coking The generated acidic substances will also cause equipment corrosion and leakage

second, the harm of coking

the coking produced during the use of the heat transfer oil furnace will form a thermal insulation layer, resulting in a decrease in heat transfer coefficient, an increase in exhaust gas temperature, and an increase in fuel consumption; On the other hand, as the temperature required by the production process remains unchanged, the temperature of the heating furnace tube wall will rise sharply, which will cause the furnace tube to bulge and rupture, and finally burn through the furnace tube, causing the heating furnace to catch fire and explode, causing serious accidents such as personal injury to equipment and operators In recent years, such accidents are common

III. influencing factors of coking

1 Through the analysis of the above coking formation process, it is found that the oxidation stability and thermal stability of the heat transfer oil furnace are closely related to the coking speed and quantity Many fire and explosion accidents are caused by the poor thermal stability and oxidation stability of heat transfer oil furnaces, which cause serious coking during operation

2. The design and installation of heating system

whether the various parameters provided by the design of heating system and the installation of equipment are reasonable directly affect the coking tendency of heat transfer oil furnace The installation of each equipment is different, which will also affect the service life of the heat transfer oil furnace The equipment installation must be reasonable, and timely rectification is required during commissioning, which is conducive to extending the service life of the heat transfer oil furnace

3. Daily operation and maintenance of the heating system

different operators have different levels of control over factors such as temperature and flow rate of the heating system, even if they use the same heating equipment and heat transfer oil furnace, due to different objective conditions such as educational level and technical level Temperature is an important parameter for thermal oxidation reaction and thermal polymerization reaction in heat transfer oil furnace With the increase of temperature, the reaction speed of these two reactions will increase sharply, and the coking tendency will also increase According to the relevant theory of chemical engineering principle: with the increase of Reynolds number, the coking rate slows down Reynolds number is directly proportional to the flow rate of the heat transfer oil furnace Therefore, the greater the flow rate of the heat transfer oil furnace, the slower the coking

IV. solutions to coking

measures should be taken from the following aspects to slow down the formation rate of coking and extend the use mission of heat transfer oil furnace:

1 Select the heat transfer oil furnace with appropriate brand and monitor the existence of these problems, so that China's plastic machinery industry cannot meet the change trend of physical and chemical indicators of foreign plastic machinery level as soon as possible.

heat transfer oil is classified according to the maximum service temperature. Among them, mineral heat transfer oil mainly has three brands: l-qb280, l-qb300 and l-qc320, and its maximum service temperature is 280 ℃, 300 ℃ and 320 ℃ respectively According to the maximum heating temperature of the heating system, the heat transfer oil with appropriate brand and quality meeting the standard of sh/t "heat transfer fluid" should be selected The heat transfer oil furnace prepared by refined base oil with excellent thermal stability and high temperature antioxidant and anti scaling additive shall be selected Among them, high temperature antioxidant can effectively delay the oxidation thickening during the operation of heat transfer oil furnace; High temperature anti scaling agent can dissolve the coking in the furnace tube and pipeline, disperse it in the heat transfer oil furnace, and finally filter it through the bypass filter of the system to keep the furnace tube and pipeline clean After using the heat transfer oil for three months or half a year, track and analyze its viscosity, flash point, acid value and carbon residue. When two of these indicators exceed the specified limit (carbon residue is not more than 1.5%, acid value is not more than 0.5mgkoh/g, flash point change rate is not more than 20%, viscosity change rate is not more than 15%), consider adding some new oil or changing all oil

2. Heating can also turn traditional "white pollution" plastics into degradable environmental protection products. Reasonable design and installation of the system

the design and installation of the heating system of the heat transfer oil furnace should strictly follow the design procedures of the heat transfer oil furnace formulated by the relevant national departments to ensure the safe operation of the heating system

3. Standardize the daily operation of the heating system. The special experimental machine for steel strand is an ideal testing equipment for industrial and mining enterprises, scientific research institutions, colleges and universities, engineering quality supervision stations and other departments. The daily operation of the heating system of the heat transfer oil furnace should strictly implement the safety technical supervision regulations for the organic heat carrier furnace formulated by the relevant national departments, and monitor the change trend of the temperature and flow rate of the heat transfer oil furnace and other parameters in the heating system at any time In actual use, the average temperature at the outlet of the heating furnace should be at least 20 ℃ lower than the maximum operating temperature of the heat transfer oil furnace The temperature of the heat-conducting oil furnace in the expansion tank of the open system should be lower than 60 ℃, and the maximum temperature should not exceed 180 ℃ The flow rate of the heat transfer oil furnace in the hot oil furnace should not be less than 2.5 m/s, so as to increase the turbulence degree of the heat transfer oil furnace, reduce the thickness of the stagnant bottom layer in the heat transfer boundary layer and the thermal resistance of convective heat transfer, improve the convective heat transfer coefficient, and achieve the purpose of strengthening fluid heat transfer

4. Cleaning of heating system this paper is a related introduction to the experimental steps of hydraulic universal testing machine and the commissioning of oil pump

thermal oxidation and thermal polymerization products first form polymerized high carbon viscous substances, which are attached to the pipe wall, and these substances can be removed by chemical cleaning High carbon viscous substances further form incomplete graphitized deposits, and chemical cleaning is only effective for the parts that have not been carbonized Graphitized coke is completely formed Chemical cleaning of such substances has not solved the problem, and mechanical cleaning is mostly used abroad

it should be checked frequently in use. When the formed high carbon viscosity has not been carbonized, users can buy chemical cleaning agents for cleaning