Background
Paraffin is a solid petroleum product obtained by solvent dewaxing and deoiling vacuum distillate oil, and is an important raw material for medicine, daily chemical industry and other fine chemical industries. The paraffin wax can be roughly classified into paraffin wax, high-melting-point petroleum wax, microcrystalline wax, vaseline, and the like. The paraffin wax for the applications needs to be deeply refined to remove sulfur, nitrogen compounds and polycyclic aromatic hydrocarbon contained in the paraffin wax so as to be harmless to human bodies. The paraffin refining includes clay refining and hydrorefining, wherein the hydrorefining technology is a process of hydro-converting non-ideal components in raw materials under certain temperature, pressure, hydrogen and the presence of a catalyst. Compared with clay refining, hydrorefining has the characteristics of high product yield, good quality, no waste residue and the like, and is a main method for refining paraffin.
The paraffin hydrofining is to deeply refine a paraffin raw material under mild reaction conditions to effectively remove heteroatoms such as sulfur, nitrogen and the like and saturated polycyclic aromatic hydrocarbons. The mild reaction condition means that cracking and isomerization reaction of carbon-carbon bond is not allowed to occur in the paraffin hydrogenation process, the oil content in the paraffin is prevented from rising, and the physical properties such as penetration degree, melting point and the like are prevented from changing. The hydrogenation technology of microcrystalline wax and mixed crystal wax is to process the high-quality microcrystalline wax and mixed crystal wax produced by refining deasphalted oil or heavy oil with solvent and dewaxing and deoiling, and even can reach the quality requirements of food grade and medicine grade. The liquid phase hydrogenation technology can meet the requirement of producing clean paraffin under the condition of greatly reducing energy consumption. US6213835 and US6428686 disclose a hydrogenation process in which hydrogen is pre-dissolved. In the methods, hydrogen is dissolved in raw materials to carry out hydrogenation reaction, the residual hydrogen in the reaction is not utilized, and the hydrogen 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 paraffin hydrogenation is a liquid phase reaction, and the reaction types of the two reactions are completely different, so the refinery gas hydrotreating and paraffin liquid phase hydrogenation combined method is rarely reported.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a hydrogenation combined process. The method can simultaneously hydrotreat refinery gas and produce paraffin products. The utilization efficiency of the hydrogen is improved on the premise of not influencing the quality of the paraffin products and even improving the quality of the paraffin 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 hydrogenation combined process, which comprises the following steps:
(a) mixing the paraffin raw oil and the circulating oil with hydrogen in a hydrogen dissolving device, then feeding the mixture into a hydrogenation catalyst bed layer in a hydrogenation reactor to react under the condition of hydrogenation operation, wherein the catalyst bed layer is provided with a plurality of layers, preferably 2-6 layers, and a gas dissolving device is arranged between adjacent catalyst bed layers;
(b) mixing refinery gas and/or hydrogen, entering a gas dissolving device arranged between any adjacent catalyst bed layers, mixing the refinery gas and/or hydrogen with a reactant flow from the previous catalyst bed layer, and entering the next catalyst bed layer for reaction;
(c) mixing the hydrogenation reaction material flow obtained in the step (b) 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;
(d) separating the hydrogenation reaction effluent obtained in the step (c) into a gas phase and a liquid phase, continuously separating the gas phase obtained by separation after removing hydrogen sulfide to obtain hydrogen and refinery gas after hydrogenation treatment, fractionating the liquid phase obtained by separation to obtain naphtha and paraffin products, and returning part of the liquid phase obtained by separation of the high-pressure separator and/or part of the hydrogenation reaction effluent obtained in the step (b) and/or part of the hydrogenation reaction material flow obtained in the step (c) as circulating oil to hydrogen dissolving equipment.
In the above method, the raw paraffin oil used may include one or more of liquid paraffin, high melting point petroleum wax, microcrystalline wax, mixed microcrystalline wax, vaseline, synthetic wax, and other paraffin fractions.
In the method, the hydrogenation operation condition is generally that the reaction pressure is 3.0-15.0 MPa, and the volume space velocity of the paraffin raw oil is 0.2h-1~6.0h-1The average reaction temperature is 180-450 ℃, and the ratio of the circulating oil to the paraffin raw oil is 0.2: 1-10: 1; the preferable operation conditions are that the reaction pressure is 4.0 MPa-14.0 MPa, and the volume airspeed of the paraffin raw oil is 0.3h-1~5.0h-1The average reaction temperature is 200-430 ℃, and the ratio of the circulating oil to the paraffin raw oil is 0.5: 1-8: 1.
In the method, the supplementary hydrogenation operation condition is generally that the reaction pressure is 3.0-15.0 MPa, and the volume space velocity of the paraffin raw oil is 0.3h-1~40.0h-1The average reaction temperature is 180-450 ℃; the preferable operation conditions are that the reaction pressure is 4.0 MPa-14.0 MPa, and the volume airspeed of the paraffin raw oil is 0.5h-1~30.0h-1The average reaction temperature is 200-430 ℃.
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% by weight calculated by 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 481-2B, FV-1, FV-10, FV-20, FV-30 and the like developed by Fushun petrochemical research institute (FRIPP).
In the method, preferably, the paraffin raw oil and the circulating oil are mixed and then mixed with hydrogen in a hydrogen dissolving device, and then the mixture enters a hydrogenation catalyst bed layer to react under the hydrogenation operation condition, wherein the volume of the hydrogenation catalyst passing through the reaction material is 30-80% of that of all the hydrogenation catalysts, preferably 35-75%, and most preferably 40-65%, and then the reaction material is introduced into refinery gas.
In the method, the paraffin raw oil and the circulating oil are mixed and then enter from the top of the hydrogenation reactor, the mixed material flow in which the hydrogen and/or the hydrogen-refinery gas is dissolved can pass through the catalyst bed layer from top to bottom, the paraffin raw oil and the circulating oil are mixed and then can also enter from the bottom of the hydrogenation reactor, and the mixed material flow in which the hydrogen and/or the hydrogen-refinery gas is dissolved 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, the dry gas and the liquefied gas in the refinery gas in the step (b) and the step (c) are independently mixed with hydrogen and then respectively enter gas dissolving equipment arranged between different adjacent catalyst bed layers.
One particularly preferred embodiment is as follows: the hydrogenation reactor is internally provided with three catalyst beds, gas dissolving equipment is arranged between adjacent catalyst beds, dry gas and hydrogen are mixed and then enter the gas dissolving equipment between the second catalyst bed and the third catalyst bed, liquefied gas and hydrogen are mixed and then enter the gas dissolving equipment between the beds of the supplementary hydrogenation reactor, and the dry gas entering the hydrogenation reactor accounts for 50-100% of the volume of all dry gas raw materials.
In the method, the volume ratio of the hydrogen introduced in the step (b) to the refinery gas is 2: 1-200: 1, preferably 5: 1-150: 1, and more preferably 10: 1-100: 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 and a paraffin product.
In the above method, the gas separator used for gas separation is a conventional separator. And the gas obtained by separation in the high-pressure separator and the gas obtained by separation in the low-pressure separator are mixed and then separated in the gas separator to obtain hydrogen, dry gas, liquefied gas and the like, and if a liquid product exists, the gas directly enters a stripping tower and/or a fractionating tower.
Hydrogen dissolved in the paraffin liquid phase hydrogenation process is excessive, and a large amount of hydrogen can be dissolved in hydrogenation generated oil after the reaction is finished, so that the hydrogen is not used effectively, namely, the energy consumption is increased; 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. Research results show that the refinery gas and the incompletely hydrotreated material of paraffin have higher solubility and the refinery gas has higher saturation in a liquid phase, and the refinery gas can be effectively dissolved in a paraffin stream for hydrogenation reaction. In the paraffin liquid phase circulating hydrogenation device, a gas raw material and hydrogen are mixed and enter a plurality of catalyst bed layers behind the device, the aim of producing hydrogenation purified gas is achieved by utilizing a hydrogenation catalyst with higher reaction pressure and higher activity and hydrogen atmosphere fused into a liquid phase, the utilization efficiency of the hydrogen is improved on the premise of not influencing the quality of paraffin products, the equipment investment is reduced overall, and the operation energy consumption is reduced.
In the prior art, clean paraffin is produced from paraffin raw materials by a liquid phase circulating hydrogenation method, dry gas products are produced from dry gas raw materials by a fixed bed hydrogenation method, and liquefied gas products are produced from liquefied gas raw materials by a fixed bed hydrogenation method. The gas has a certain solubility in liquid, which is the principle of the development of a paraffin liquid phase circulation hydrogenation technology, namely, the hydrogenation reaction is realized by utilizing hydrogen dissolved in paraffin, wherein the catalyst of a first bed layer plays the largest role, and a large amount of hydrodesulfurization reaction which easily occurs all occur in the bed layer. However, the dissolved hydrogen cannot be completely reacted, and a large amount of hydrogen can be remained in the reaction product, and usually 20% -70% of the dissolved hydrogen can be remained. Dry gas and liquefied gas, etc. as organic gases, have higher solubility in paraffin and can increase the amount of dissolved hydrogen in the presence of hydrogen. And the dissolved dry gas and liquefied gas are easy to generate hydrogenation reaction in the atmosphere of catalyst and hydrogen, thus realizing the purpose of producing clean gas. According to the invention, by fully utilizing the characteristic that the paraffin liquid phase circulation hydrogenation process needs to dissolve hydrogen, in order to reduce the influence of dissolved gas on the original paraffin hydrogenation as much as possible, the mixed hydrogen of a gas raw material enters the catalyst bed layer behind the first catalyst bed layer, the hydrogenation reaction of the gas is completed by utilizing the atmosphere of hydrogen and the catalyst, and the hydrogen can be dissolved into the paraffin raw material more so as to promote the paraffin hydrogenation reaction; or further mixing part of dry gas or all dry gas raw materials in the mixed gas with hydrogen to enter a second catalyst bed layer, wherein the main points are that the olefin content in the dry gas is low, the hydrogen consumption is low, the quantity of required active centers is small, the time of a reaction desorption process is short, the influence on the paraffin hydrogenation reaction is reduced to the minimum, and the gas with relatively high hydrogen consumption is introduced into the subsequent catalyst bed layer with relatively low hydrogen consumption in paraffin hydrogenation, so that the influence on the paraffin hydrogenation effect is reduced.
The method further utilizes the characteristic that a large amount of hydrogen is still dissolved in the oil generated by the paraffin liquid-phase circulating hydrogenation process, a supplementary hydrogenation reactor is arranged behind the paraffin hydrogenation reactor, the refinery gas raw material is dissolved in the paraffin hydrogenation reaction material flow and enters a 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 paraffin is used for the gas hydrogenation reaction, so that the hydrogen consumption is reduced; 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 paraffin hydrogenation 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 paraffin product to obtain the paraffin product and the gas product, and the two technologies are optimally combined to save equipment investment and operation cost.