Background
The lubricating oil is a non-volatile oily lubricant and is prepared by blending base oil and additives, wherein the quality of the base oil determines the evaporation performance, low-temperature fluidity, high-temperature thermal oxidation stability, viscosity-temperature performance and the like of the lubricating oil product. The base oil is a carrier of the lubricating oil additive and also a main body of the lubricating oil. Compared with the traditional 'three sets of' processes, the hydrogenation process can change the original hydrocarbon structure through a chemical reaction mode, and converts cyclic substances, saturated hydrocarbon, aromatic hydrocarbon and the like in the oil into ideal components, so that the limitation on the raw materials is relatively wide, and the hydrogenated base oil has the characteristics of low sulfur, low nitrogen, low aromatic hydrocarbon content, low toxicity, higher viscosity index, excellent thermal stability and oxidation stability, lower volatility, good viscosity-temperature performance, good additive sensitivity and the like.
The hydrogenation technology of lubricating oil usually adopts a two-stage process, and the raw oil is firstly subjected to hydrotreating to remove impurities such as sulfur, nitrogen, oxygen and the like, and the generated oil is subjected to isodewaxing to obtain different types of high-quality lubricating oil base oil. The liquid phase lubricating oil hydrogenation technology can meet the requirement of clean diesel oil production under the condition of greatly reducing energy consumption. US6213835, US6428686 and CN103797093B disclose a hydrogenation process of pre-dissolved hydrogen, which all dissolve hydrogen into the lubricating oil raw material to carry out hydrogenation reaction, and the residual hydrogen is not utilized and is directly treated additionally after separation.
Refinery gases generally include dry gases, liquefied gases, and the like, and have various paths for their use. The main application comprises that dry gas is hydrogenated and then used as a raw material for preparing ethylene by steam cracking, liquefied gas is hydrogenated and then used as a raw material for preparing ethylene by steam cracking, a raw material for synthesizing maleic anhydride, liquefied gas for vehicles and the like. In the existing refinery gas hydrogenation technology, CN201410271572.3 discloses a coking dry gas hydrogenation catalyst and a catalyst grading method. The method only solves the problem of controlling the reaction temperature during the hydrogenation of the coking dry gas, but the temperature rise in the reaction process is large. CN201010221244.4 discloses a method for preparing ethylene cracking material by hydrogenation of liquefied petroleum gas, which comprises two reactors, a cooling facility is arranged between the reactors, and CN201310628425.2 discloses a high-temperature hydrogenation purification process of liquefied petroleum gas, wherein olefin saturation and hydrogenation are performed by hydrogenation to remove impurities. As is well known, the hydrogenation reaction of unsaturated hydrocarbons such as olefin, diene, alkyne and the like is a strong exothermic reaction, the temperature rise in the gas hydrogenation process is very large, generally 100-200 ℃, the balance of the hydrogenation reaction is damaged along with the temperature rise, and the generation of carbon deposition is seriously increased, so that the service cycle of the catalyst is reduced.
CN201010221263.7 discloses a liquefied petroleum gas-coker gasoline hydrogenation combination process method, which is a combination method, but not a liquid phase hydrogenation method, the coker gasoline is firstly mixed with hydrogen to carry out fixed bed hydrogenation reaction, and a hydrogenation product and liquefied gas are mixed and enter another reactor, so that the problem of hydrogenation temperature rise of the liquefied gas is only solved.
In summary, in the prior art, the refinery gas hydrotreating process is a gas phase reaction, the lubricating oil hydrogenation is a liquid phase reaction, and the reaction types of the two reactions are completely different, so the refinery gas hydrotreating and lubricating oil liquid phase hydrogenation combined method is rarely reported.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a hydrogenation combination processing method. The method can simultaneously carry out hydrotreating on refinery gas and producing the lubricating oil base oil. The utilization efficiency of hydrogen is improved on the premise of ensuring the quality of lubricating oil products, the problem of temperature rise in the hydrotreating process of refinery gas is effectively solved, the equipment investment is reduced overall, and the operation energy consumption is reduced.
The invention relates to a refinery gas combined processing method, which comprises the following steps:
(a) raw oil and circulating oil of lubricating oil are mixed with hydrogen in hydrogen dissolving equipment and then enter a hydrotreating catalyst bed layer in a lubricating oil hydrotreating reactor to react under the condition of liquid-phase hydrogenation operation;
(b) mixing the reactant flow obtained in the step (a) with refinery gas and hydrogen in a gas dissolving device, and then allowing the mixture to enter a hydrogenation catalyst bed layer in a supplementary hydrogenation reactor to react under the liquid-phase hydrogenation operation condition;
(c) separating the hydrogenation reaction effluent in the step (b) into a gas phase and a liquid phase, continuously separating the gas phase obtained by separation after removing hydrogen sulfide to obtain hydrogen and hydrotreated refinery gas, fractionating the liquid phase obtained by separation to obtain naphtha, diesel oil and hydrotreated heavy distillate oil, and returning part of the hydrogenation reaction effluent obtained in the step (a) and/or part of the hydrogenation reaction material flow obtained in the step (b) and/or part of the liquid phase obtained by separation of the high-pressure separator as circulating oil to hydrogen dissolving equipment.
(d) Mixing the hydrotreated heavy distillate oil and hydrogen, feeding the mixture into a hydroisomerization catalyst bed layer in a hydroisomerization reactor, reacting under the condition of hydrogenation operation, separating reactant flow in a high-pressure separator, recycling the separated gas, and fractionating the separated liquid in a fractionating tower to obtain various lubricating oil base oils.
The lube-oil feedstock used in the above process may include various vacuum distillates, such as second-cut distillate, third-cut distillate, fourth-cut distillate, light deasphalted oil, etc., or solvent refined oils of the above feedstocks, and solvent refining may be carried out by conventional methods.
In the method, the hydrotreating operation condition is generally that the reaction pressure is 3.0-20.0 MPa, and the volume space velocity of the raw oil of the lubricating oil is 0.2h-1~8.0h-1The average reaction temperature is 180-450 ℃, and the ratio of the circulating oil to the raw oil of the lubricating oil is 0.5: 1-10: 1; the preferable operation conditions are that the reaction pressure is 4.0 MPa-18.0 MPa, and the volume airspeed of the raw oil of the lubricating oil is 0.5h-1~6.0h-1The average reaction temperature is 200-440 ℃, and the ratio of the circulating oil to the raw oil of the lubricating oil is 0.6: 1-8: 1.
In the method, the supplementary hydrotreating operation condition is generally that the reaction pressure is 3.0MPa to 20.0MPa, and the volume airspeed of the raw oil of the lubricating oil is 0.5h-1~40.0h-1The average reaction temperature is 180-450 ℃; the preferable operation conditions are that the reaction pressure is 4.0 MPa-18.0 MPa, and the volume airspeed of the raw oil of the lubricating oil is 0.8h-1~30.0h-1The average reaction temperature is 200-440 ℃.
In the method, the hydrogenation active component in the hydrogenation catalyst is one or more of Co, Mo, W and Ni, the weight content of the hydrogenation active component is 5-70% in terms of oxide, the carrier of the hydrogenation catalyst is generally alumina, amorphous silicon aluminum, silicon oxide, titanium oxide and the like, and other auxiliary agents such as P, Si, B, Ti, Zr and the like can be simultaneously contained. The catalyst may be used commercially or may be prepared by methods known in the art. The hydrogenation active component is a catalyst in an oxidation state, and is subjected to conventional vulcanization treatment before use, so that the hydrogenation active component is converted into a vulcanization state. The commercial hydrogenation catalysts mainly comprise hydrogenation catalysts such as 3926, 3936, CH-20, FF-14, FF-18, FF-24, FF-26, FF-36, FF-46, FF-56, FH-98, FH-UDS and FZC-41 developed by the Fushu petrochemical research institute (FRIPP), hydrogenation catalysts such as HR-406, HR-416 and HR-448 of IFP company, hydrogenation catalysts such as ICR154, ICR174, ICR178 and ICR179 of CLG company, hydrogenation catalysts such as HC-P, HC-K UF-210/220 newly developed by UOP company, hydrogenation catalysts such as TK-525, TK-555 and TK-557 of Topsor company, KF-752, KF-756, KF-757, KF-840, KF-848, KF-901, KF-907 and the like hydrogenation catalysts of AKZO corporation.
In the method, the catalyst bed layers of the hydrotreating reactor in the step (a) are arranged into a plurality of layers, preferably 2-8 layers, and a gas dissolving device is arranged between the adjacent catalyst bed layers; the introduced hydrogen is mixed with the reactant flow in the gas dissolving device and then enters the next catalyst bed layer for reaction.
In the above method, one or more catalyst beds, preferably 2 to 8 catalyst beds, may be provided in the make-up hydrogenation reactor. If only one catalyst bed layer is arranged in the supplementary hydrogenation reactor, the liquid-phase hydrogenation reaction material flow is mixed with the refinery gas in the gas dissolver and then enters the top of the supplementary hydrogenation reactor and passes through the catalyst bed layer; if a plurality of catalyst beds are arranged in the supplementary hydrogenation reactor, a gas dissolving device is arranged between the beds, refinery gas and hydrogen are mixed and then enter any gas dissolving device arranged between adjacent catalyst beds, and are mixed with reactant flow from the previous catalyst bed and then enter the next catalyst bed for reaction.
A preferred embodiment is as follows: the catalyst bed layers of the lubricating oil hydrogenation reactor are arranged into three layers, the catalyst bed layer of the supplementary hydrogenation reactor is arranged into two layers, hydrogen is introduced between the second catalyst and the third catalyst bed layer of the lubricating oil hydrogenation reactor, and hydrogen and refinery gas are introduced between the catalyst bed layers of the supplementary hydrogenation reactor.
In the method, the raw lubricating oil and the circulating oil are mixed and then enter the lubricating oil hydrogenation reactor from the top, the mixture flow with dissolved hydrogen can pass through the catalyst bed layer from top to bottom in a downward mode, the raw lubricating oil and the circulating oil are mixed and then can also enter the lubricating oil hydrogenation reactor from the bottom, and the mixture flow with dissolved hydrogen can pass through the catalyst bed layer from bottom to top in an upward mode.
In the method, the mixed material flow of the lubricating oil hydrogenation reaction effluent dissolved with the refinery gas enters from the top of the supplementary hydrogenation reactor, the mixed material flow dissolved with the refinery gas can pass through the catalyst bed layer from top to bottom, the mixed material flow of the lubricating oil hydrogenation reaction effluent dissolved with the refinery gas can also enter from the bottom of the supplementary hydrogenation reactor, and the mixed material flow dissolved with the refinery gas can pass through the catalyst bed layer from bottom to top.
In the above method, the previous catalyst bed or the next catalyst bed is based on the flowing direction of the reactant flow, and whether the hydrogenation reaction is an upflow type or a downflow type, the bed in the adjacent beds which is contacted with the reactant flow first is an upper bed and then is a lower bed.
In the method, the refinery gas may comprise one or more of dry gas, liquefied gas and the like. The source of the gas can be one or more of coking, catalytic cracking, thermal cracking, visbreaking and the like.
In the method, if hydrogen and refinery gas are introduced simultaneously in any process, the volume ratio of the introduced hydrogen to the refinery gas is 1: 1-100: 1, preferably 1: 1-50: 1.
In the method, the hydrogenation reaction effluent is separated by a high-pressure separator and/or a low-pressure separator. The high-pressure separator is a conventional gas-liquid separator. The hydrogenation reaction flow is separated in a high-pressure separator to obtain gas and liquid. The low-pressure separator is a conventional gas-liquid separator. The liquid obtained by separation in the high-pressure separator is separated in the high-low pressure separator to obtain gas and liquid.
In the method, the fractionating system used for fractionating comprises a stripping tower and/or a fractionating tower. And the liquid obtained by separation in the low-pressure separator is subjected to steam stripping and/or fractionation in a fractionation system to obtain a naphtha product, a diesel product and a hydrogenated lubricating oil product.
In the above method, the gas separator used for gas separation is a conventional separator. The gas obtained by separation in the high-pressure separator and the gas obtained by separation in the low-pressure separator are mixed, hydrogen sulfide is removed, then hydrogen, dry gas, liquefied gas and the like are obtained by separation in the gas separator, and if liquid products exist, the gas directly enters a stripping tower and/or a fractionating tower.
In the method, the hydroisomerized raw oil is a heavy fraction obtained by fractionating hydrogenated reactants, and the sulfur content of the heavy fraction is required to be less than 5 mug/g, the nitrogen content is required to be less than 5 mug/g, preferably the sulfur content is less than 3 mug/g, and the nitrogen content is less than 3 mug/g.
In the method, the hydroisomerization operation condition is generally 3.0-18.0 MPa of reaction pressure, and the volume space velocity of the raw oil is 0.2h-1~6.0h-1The average reaction temperature is 180-450 ℃, and the volume ratio of hydrogen to oil is 300: 1-1500: 1; the preferable operation conditions are that the reaction pressure is 4.0 MPa-16.0 MPa, and the volume airspeed of the raw oil is 0.4h-1~5.0h-1The average reaction temperature is 200-440 ℃, and the volume ratio of hydrogen to oil is 400: 1-1200: 1.
In the method, the hydroisomerization catalyst is various suitable lubricating oil hydroisomerization catalysts, the carrier is an NU-10 molecular sieve or ZSM-22 molecular sieve with an alumina and TON structure, an SAPO-11 molecular sieve, beta zeolite and the like, the content of the molecular sieve in the catalyst is 30-80 wt%, preferably 40-70 wt%, and partial silicon oxide, amorphous silicon aluminum and the like can also be added into the carrier; the active metal component is one or more of Pt, Pd, Ru, Rh and Mo, Ni, and the content in the catalyst is 0.1 wt% -30.0 wt%. The optional auxiliary agent component is one or more of boron, fluorine, chlorine and phosphorus, and the content of the optional auxiliary agent component in the catalyst is 0.1 wt% -5.0 wt%; the specific surface of the catalyst is 150-500 m2The pore volume is 0.15-0.60 ml/g. Before use, the catalyst is reduced to make the hydrogenation active metal in a reduction state in the reaction process. The commercial hydrogenation catalysts mainly comprise FIW-1, FRIC-1, FEIC-2 and the like developed by the Fushun petrochemical research institute (FRIPP).
In the above method, the hydroisomerization effluent is separated by a high-pressure separator and/or a low-pressure separator. The high-pressure separator is a conventional gas-liquid separator. The hydrogenation reaction flow is separated in a high-pressure separator to obtain gas and liquid. The low-pressure separator is a conventional gas-liquid separator. The gas obtained by separation in the high-pressure separator is recycled after being pressurized by a compressor, and the liquid obtained by separation in the high-pressure separator is separated in the low-pressure separator to obtain the gas and the liquid.
In the above process, the hydroisomerization fraction is fractionated using a fractionation system comprising a fractionation column. And the liquid obtained by separation in the low-pressure separator is fractionated in a fractionating system to obtain naphtha and various lubricating oil base oil products.
In the process of gas hydrogenation, the temperature rise of a catalyst bed layer is large due to large reaction heat release, so that the temperature range of the hydrogenation reaction is large, the effect of the hydrogenation reaction is influenced, the generation of carbon deposition of the catalyst is accelerated, and the service cycle of the catalyst is shortened. In the liquid-phase hydrogenation process of the lubricating oil, hydrogenation reaction is realized by hydrogen dissolved in the oil, so that the purpose of producing clean lubricating oil products is achieved, the dissolved hydrogen is excessive and cannot be completely reacted, and the hydrogen dissolved in the oil generated by hydrogenation after the reaction is finished can be remained by 20-70% of the hydrogen, so that the hydrogen is not used effectively, namely, the energy consumption is increased.
According to the invention, by fully utilizing the characteristic that a large amount of hydrogen is still dissolved in the generated oil by the lubricating oil liquid-phase circulating hydrogenation process, a supplementary hydrogenation reactor is arranged in the follow-up of the lubricating oil hydrogenation reactor, the refinery gas raw material is dissolved in the lubricating oil hydrogenation reaction material flow and enters the catalyst bed layer of the supplementary hydrogenation reactor, and the hydrogenation reaction of the gas is completed by utilizing the dissolved hydrogen and the catalyst atmosphere, so that the problem of large gas hydrogenation temperature rise is solved, and the hydrogen dissolved in the lubricating oil is used for the gas hydrogenation reaction, thereby reducing the hydrogen consumption; or a plurality of catalyst beds are arranged in a further supplementary hydrogenation reactor, part of dry gas or all dry gas raw materials in the mixed gas and lubricating oil hydrogenation generated oil are mixed and enter the first catalyst bed, and the rest gas and/or hydrogen mixed mixture enters the subsequent catalyst bed. The combination method is generally characterized in that the gas hydrogenation process is completed on the premise of not influencing the quality of the lubricating oil product or further improving the quality of the lubricating oil product to obtain the lubricating oil product and the gas product, and the two technologies are optimally combined, so that the hydrogen dissolved in the lubricating oil product is reduced, namely, the hydrogen consumption and the energy consumption are reduced, the equipment investment is saved, and the operation cost is reduced.