High Sulfur Heavy Crude Oil Processing Route
In recent years, with the vigorous development of shale oil resources in the United States, the supply of light crude oil has been increased, and the global economy and consumer market have been depressed due to the impact of the epidemic. In the short term, the international oil price has been at a low level, and the price difference between superior and inferior crude oil has narrowed.
Therefore, it is worth discussing whether the refinery processing high sulfur heavy crude oil has significant economic benefits. For the processing of high sulfur heavy crude oil, different process combination routes were adopted to realize the production of oil and chemical products, and the product structure and economic benefits of different schemes were compared and analyzed, which provided a reference for the optimization of the processing route selection of the refinery.
1. Delayed coking technology route
Delayed coking technology is a relatively mature, reliable and flexible thermal cracking technology. It has the advantages of good raw material adaptability, high decarbonization efficiency, low investment and operation cost, and is also an effective means of refinery "waste" treatment.
According to the latest standard of petroleum coke, when the sulfur content of coke is greater than 3%, coke can only be used as the enterprise's own production and use, and the local deployment of self-use petroleum coke cannot be sold as a product, which is not conducive to the full utilization of petroleum resources.
2. Technical route of fixed bed residual oil hydrogenation
Fixed bed residual oil hydrotreating technology is mature, the equipment is simple, and the investment is relatively low. It is suitable for processing atmospheric residual oil, or processing vacuum residual oil and mixing part of straight distillation heavy wax oil, coking wax oil, deasphalted oil, furfural extraction oil, catalytic diesel oil, etc. Generally, the metal content of raw materials is less than 150µg/g and the residual carbon value is less than 15%. The fixed-bed residual oil hydrogenation unit is mainly used for the pretreatment of catalytic cracking raw materials, aiming at deep desulfurization and taking into account the needs of the removal of residual carbon and metal. The conversion rate is generally controlled at 10%~20%.
At present, the fixed bed residual oil hydrogenation unit is mainly limited by the operation cycle, so it is usually necessary to adopt multiple reactors, set multiple catalyst beds, and fill the hydrogenation protective agent, metal removal catalyst, desulfurization catalyst and nitrogen and carbon removal catalyst in order to meet the needs of the long cycle operation of the unit.
3. Boiling bed residue hydrogenation technology route
The hydrotreating process of boiling bed residue has complex equipment, high investment, relatively mature technology, high hydrogenation conversion rate and good adaptability to raw materials. Usually under the condition of high temperature and high hydrogen partial pressure, the heavy raw materials contact with the catalyst in the boiling bed reactor from bottom to top for catalytic hydrogenation reaction and thermal cracking reaction, and are converted into dry gas, liquefied gas, naphtha, diesel oil, wax oil, and some unconverted tail oil.
In order to reduce the blockage of the asphaltene precipitation in the heavy fraction system of reaction products, the total conversion rate should be controlled according to the properties of raw materials. The conversion rate is generally less than 80%.
4. Technical route of slurry bed residue hydrogenation
Slurry bed hydrogenation technology has simple structure, mainly bubble type reactor, high equipment investment, and almost no limit on the content of impurities in the raw material.
Slurry bed hydrogenation process has a high conversion rate, which can reach more than 90%~95%, so it is regarded as an effective way to light the inferior residue. At high conversion rates, the residue can be treated by a gasification plant, while the distillate requires further hydrogenation.
5. Technical route of solvent deasphalting
Solvent deasphalting is an important pretreatment process of inferior residue. Its essence is liquid-liquid extraction physical separation based on the principle that hydrocarbon solvents have different solubility to the components in the residue. Most of the asphaltenes and aromatic compounds which are difficult to be converted, as well as the heavy metals, sulfur and nitrogen impurities which are harmful to cracking catalyst and hydrogenation catalyst, are removed from the residue, so as to obtain good quality deasphaltening oil.
The solvent used is the main factor determining the yield and quality of deasphalted oil. In general, propane solvent is suitable for the production of lubricating oil feedstock, butane or butane mixed solvent is suitable for the production of catalytic cracking feedstock, pentane solvent deasphalted and hydrodesulfurization combined process can provide more catalytic cracking feedstock.
