Summary of problems affecting long-term operation of atmospheric and vacuum distillation units

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The problems that affect the long-term operation of atmospheric and vacuum equipment are summarized. The main contents include:: Severe low-temperature corrosion on the top of the tower ； Poor crude oil desalination effect ； Sulfur and naphthenic acid corrosion in high temperature areas is serious ； There is salt formation at the top of the tower ； 3. Note that anti-corrosion measures are not perfect ； Coking in the middle and lower parts of the vacuum tower ； Water cooler scaling and low material quality ； Coking, vibration and deformation of heating furnace tubes ； Crude oil quality exceeds standard ； Over-temperature operation ； Poor vacuuming effect ； Heating furnace nitrogen oxide emissions exceed standards ； The top load of the normal pressure tower is large ； Device running at low load ； The three tops are dehydrated and contain more oil. ； The pressure pipeline inspection does not meet the requirements. The proportion of each problem is shown in the table: The number of serial number problems accounted for 1. Serious low-temperature corrosion at the top of the tower 1526.79% 2. Poor desalination effect of crude oil 712.50% 3. Severe sulfur and naphthenic acid corrosion at high temperature parts 58.93% 4. Salt formation at the top of the tower 58.93% 5. Imperfect anti-corrosion measures for the third injection 35.36% 6. Coking in the middle and lower parts of the decompression tower 35.36% 7. Fouling and poor material quality of the water cooler 35.36% 8 Coking, vibration, and deformation of the heating furnace tube 35.36% 9 The quality of crude oil exceeds the standard 23.57% 10 The nitrogen oxide emission of the heating furnace exceeds the standard 23.57% 11 Over-temperature operation 23.57% 12 Poor vacuuming effect 23.57% 13 The load at the top of the normal pressure tower is large 11.79% 14 The device operates at low load 11.79% 15 The three-top dehydration oil content is large 11.79% 16 Pressure pipeline inspection does not meet the requirements 11.79% Total 56100% Comprehensive analysis of the prevalence, importance and difficulty of solving the above problems, and condensing the bottleneck problems that affect the long-term operation of the atmospheric and vacuum distillation unit, the results are as follows: (1) The low-temperature corrosion at the top of the tower is serious, and the "one removal and three injection" anti-corrosion measures need to be improved, mainly in the following aspects: 1. Severe low-temperature corrosion on the top of the tower: The trays and tower walls on floors 1-4 of the atmospheric tower are severely corroded. ； The heat exchanger valves in the normal top part and the small pipes in the normal pressure tower body are seriously corroded and thinned. ； Corrosion and leakage of the atmospheric leg of the overhead oil and gas condensation system ； The cooler and pipelines of the overhead condensation system are seriously corroded at low temperatures. ； The permanent roof plate heat exchanger is severely corroded and clogged ； The corrosion rate of the probe in the normal top/reduced top system exceeds the standard ； The inner wall of the tube bundle at the end of the lining tube of the constant-top air cooler is prone to thinning and leakage. 2. Poor crude oil desalting effect: The operation effect of electric desalination is poor, and the qualification rate of salt content after desalination is low. ； The residence time of the crude oil electric desalting system is insufficient and the volume of the electric desalting tank is too small, which seriously restricts the desalting and dehydration effect. ； The blending of dirty oil and the single-tank operation of electric desalination have reduced the operation efficiency of the electric desalination of the device. There is scaling in the heat exchange system and the corrosion of the tower top system has intensified. ； The impurity content of Daqing crude oil is getting higher and higher, and the normal operation of the electric desalination system is affected. 3. The three anti-corrosion measures are imperfect: The pH value of dehydration at the top of the tower is not automatically controlled ； The water injection position at the top of the normal pressure tower is unreasonable, the atomization effect of the water injection and agent injection nozzles is poor, and the water injection volume is insufficient. ； The neutralizer and corrosion inhibitor were not injected separately, there was no dedicated nozzle, the pH value and corrosion rate exceeded the standards, etc. (2) Serious sulfur and naphthenic acid corrosion in high-temperature areas is mainly manifested in the following aspects: Naphthenic acid corrosion of high temperature pipeline equipment ； High-temperature sulfur and naphthenic acid corrosion and leakage problems in the middle and lower inner walls of the pressure reduction tower ； Corrosion problems in the middle and lower tower bodies of normal pressure towers ； Decompression tower body corrosion problem ； High-temperature machine pump body corrosion problems, etc. (3) The phenomenon of salt formation at the top of the tower is mainly manifested in the following aspects: There is salt formation at the top of the normal pressure tower ； Salt and scale formation in the overhead circulation system ； Salt formation in constant-top and reduced-top condensation systems and process anti-corrosion issues ； Plate air cooling salt formation and life issues ； There is salt formation at the top of the atmospheric tower. After salt forms at the top of the atmospheric tower, the separation effect at the top of the tower decreases. The salt in the top circulation system causes corrosion to the top of the tower, causing the risk of leakage. (4) Coking in the middle and lower parts of the vacuum tower is mainly manifested in the following aspects: Coking control in the middle and lower parts of the pressure reduction tower ； The packing in the lower part of the vacuum tower is coked ； Vacuum tower packing coking, etc. (5) The scaling and low material quality of the water cooler are mainly manifested in the following aspects:: The pipe bundle material of the initial top water cooler is low ； Roof reduction and scaling of each side line cooler ； Problems with scaling of the overhead cooler, etc. (6) Coking, vibration, deformation and excessive emissions of heating furnace tubes are mainly manifested in the following aspects: Coking of decompression furnace tube ； Decompression furnace tube bending and deformation ； Normal pressure furnace tube vibration ； Nitrogen oxide emissions from heating furnaces exceed standards, etc.