How to determine coking in a tubular furnace

Under the same processing volume, an increase in furnace temperature, higher fuel consumption, and a greater pressure drop in the furnace tubes indicate coking. Reason: Uneven heating of the furnace tubes, flame impinging on the tubes, resulting in local overheating of the furnace tubes. Fluctuations in feed volume and flow deviation cause the oil temperature to rise and fall erratically, or result in too low a flow rate, leading to an excessive residence time for the oil. The raw material heterocycles are polymerized, decomposed, or contain impurities. During maintenance, the coking was not removed thoroughly; as the furnace started operating again, the existing coke inside the furnace tubes acted as a catalyst, promoting the formation of new coke

In the case of coking in tubular furnaces, washing with cleaning oil and steam purging are generally used first; if these methods are ineffective, high-pressure mechanical treatment is employed, and as a last resort, the pipes have to be replaced. Perhaps there are other methods as well; everyone is welcome to discuss them together.

The coking is quite severe; it can be removed by burning, and in severe cases, high-pressure cleaning is the only option. If the furnace tube is deformed, it can only be replaced

Charring operation of the heating furnace: Principle of charring: At a certain temperature, the coke inside the furnace tubes breaks apart under the impact of high-temperature steam and air; the resulting fragments and unburned coke powder are carried away by the airflow. Purpose: To cause charring in the heating furnace. Improve the heat transfer efficiency of the furnace tubes and extend their service life. 7 {/ i) H7 U, B 1. Preparation for coking 1) Replace 2 oil transfer lines with blind flanges, and replace 1 coking tank line with a blind flange; adjust the coking process and check whether the pipelines of the coking tank are unobstructed. # y5 n" K1 S2 z1 B6 r7 G 2) Introduce fresh water; steam, compressed air – steam pressure at 0.8 MPA, compressed air pressure ≤ 0.4 MPA. 3) Prepare the ignition rod and fully open the flue dampers. 4) Contact the instrument technician to install instruments such as furnace temperature, outlet temperature, and convective outlet temperature. 6 O; j$ # k* ~1 U$ n 3) After heating with air, close attention should be paid to the color of the furnace tubes. The normal color is dark red; when the temperature of the tubes in the viscosity-reduction furnace reaches 560–570°C, they turn red. It is also necessary to pay close attention to the pressure of the industrial air and steam. If the color of the furnace tubes is abnormal, the supply of air should be stopped and the steam flow increased. 4) The temperature at which charring begins is 450°C in the furnace; in the later stages of charring, the pressure-free furnace can reach temperatures of 480–490°C, but not exceeding 500°C. The reduced-pressure furnace and the viscosity-reduction furnace can reach temperatures of 570–600°C. " i( x) C" h! Q4 t& F0 A+ H 5): To determine whether the burning is complete, one checks whether the furnace temperature has reached the upper limit for burning – 490°C for atmospheric-pressure furnaces, and 590°C for reduced-pressure and viscosity-reduction furnaces. When the color of the water does not turn black after the air supply is started, and the water assumes a slight reddish-brown color, it indicates that the burning is essentially complete. After all of the material at |4 g9 B8 E- L5 {% X 6) has burned up, the temperature in the furnace is reduced by 50°C per unit time. The heating is stopped when the furnace temperature drops to 200°C. When the furnace temperature falls below 150°C, the furnace tubes are washed with water; the clearer the water becomes, the lower the salt content and the cleaner the burning process has been. 4. Precautions * U2 l- H" U, ^% }$ u. ~# Z) f 1) It is necessary to strictly control the temperature parameters of each furnace; excessive temperatures are not allowed, with superheated steam temperature to be ≤430°C. : F3 d$ I* ]* p. _ 2） Regularly check the drainage outlet of the coking tank as well as the coking situation; if a large amount of coke is discharged, reduce the air supply, and vice versa – increase the air supply to prevent large pieces of coke from blocking the pipelines. In the event that the pipelines get blocked, it should be resolved before continuing with the burning process. Attention must also be paid to the furnace tubes, ensuring that the vibration of the pipelines is not too severe. ; ~. P5 y, K! E9 O 3) The interval between each burning process should be 10–15 minutes; ensuring adequate ventilation helps achieve an effective burning effect while also preventing the burned residues from becoming too large or causing deformation of the furnace tubes. 4) During the burning process, a dedicated person should be responsible for adjusting the flame; records of air and steam supply as well as temperature readings should be kept at each stage, and the ignition process must be even. 5) Sufficient steam pressure and air pressure must be ensured. 9 s/ V" y) E* L+ B% Y$ c Be careful; water can be added to the burnt tank first. The steam temperature at the drain outlet is high and the volume of steam is large, so take precautions to avoid injury.

I heard that there is a Korean company that is very skilled at removing coking