【Q&A Question 222】November 28, 2016
Thread Content
【Q&A Question 222】November 28, 2016: What are the causes of fouling in furnace tubes? A reference ** will be shown after responding; scoring is achieved by answering the key points. 1. The feed rate is too low or the amount of circulating gas is insufficient, resulting in an excessive residence time of the oil product in the furnace tubes. 2. The flame hits the furnace tube directly, causing localized overheating. There is residual coke inside the furnace tubes, which acts as a catalyst to promote the formation of new coke. The raw materials contain many impurities that make them prone to decomposition. Summary of Q&A posts from 2016 (updated up to November): http://bbs.hcbbs.com/thread-1597792-1-1.html. We are seeking sponsors for the “2016 HaiChuan Top 10 Members Selection Contest”: http://bbs.hcbbs.com/thread-1628108-1-1.html (Source: HaiChuan Chemical Forum)
The furnace temperature is too high, and the flow rate of the medium inside the furnace tubes is too slow
1) Local overheating due to uneven heating, with excessively high temperature at the furnace outlet； 2) Large fluctuations in furnace temperature are caused by the evacuation of the radiation feed pump or significant variations in the feed rate ； 3) Low steam injection volume or interruption ； 4) Raw materials containing many impurities such as sulfur and salts are prone to decomposition ； 5) Incomplete burning, with residual old ash remaining ； 6) A blocked back route or excessive pressure in the coke tower results in a slow flow rate of residue oil.
The quality of the raw materials is poor, and low space velocity leads to flow deviation; there is no local overheating in the heating furnace, and the furnace was not turned off after feeding stopped
High furnace tube temperature, low hydrogen-to-oil ratio, high space velocity, and poor quality of raw materials
1. The feed rate is too low or the amount of circulating gas is insufficient, resulting in an excessive residence time of the oil product in the furnace tubes. 2. The flame hits the furnace tube directly, causing localized overheating. 3. Residual coke inside the furnace tube acts as a catalyst, promoting the formation of new coke. 4 The raw materials contain many impurities and are prone to decomposition.
1. The burner does not burn evenly, resulting in excessively high local temperatures; 2. The feed contains high levels of olefins and other polycyclic aromatic hydrocarbons, which cause polymerization and coking inside the furnace tubes
①Uneven flames result in uneven furnace temperatures, leading to localized overheating of the furnace tubes. ②Excessive changes in feed rate or sudden interruptions, etc. ③The flame deflects the furnace tube, causing localized overheating.
1. The feed rate is too low or the amount of circulating gas is insufficient, resulting in an excessive residence time of the oil product in the furnace tubes. 2. The flame hits the furnace tube directly, causing localized overheating. There is residual coke inside the furnace tube, which acts as a catalyst to promote the formation of new coke. The raw materials contain many impurities that make them prone to decomposition
Reasons for tube coking: 1) Uneven flame length or direct flame impact on the tubes, resulting in uneven heating of the tubes and localized overheating. 2) Significant changes or interruptions in the feed rate and steam injection rate result in a substantial decrease in the flow velocity inside the furnace tubes. 3) Changes in the properties of the raw materials result in a high residue value and salt content. 4) The instrument readings are inaccurate, and the temperature at the furnace outlet is too high. 5) Deviation of the four feed branch streams. 6) Illusions from control and indication instruments, leading to incorrect judgments. 7) The feed contains a large amount of coke powder. 8) The furnace tubes are not completely burned out.