Fatty acid salt coking inhibitor as well as preparation method and application thereof

Abstract

The invention discloses a fatty acid salt coking inhibitor as well as a preparation method and application thereof, and belongs to the technical field of coking inhibitors. According to the technical scheme, fatty acid reacts with a potassium compound to obtain the coking inhibitor, wherein the fatty acid is one or a mixture of oleic acid and stearic acid, and the potassium compound is potassium hydroxide, potassium carbonate or potassium bicarbonate. The coking inhibitor disclosed by the invention can be directly added into cracking raw oil for heavy raw material cracking furnaces such as diesel oil and tail oil, and injection equipment such as an inhibitor nozzle does not need to be additionally arranged independently, so that the unnecessary blocking risk is reduced, and the process complexity is reduced; and compared with the existing sulfur and phosphorus-containing oil-soluble inhibitor, the coking inhibitor provided by the invention has good decoking performance for middle and later-stage gas-phase coking.

Description

Technical Field

[0001] The invention relates to the technical field of coking inhibitors, and in particular to a fatty acid salt coking inhibitor and a preparation method and application thereof. Background Art

[0002] More than 80% of the world's ethylene production uses tubular furnace steam cracking technology. Its hydrocarbon liquid raw materials often contain a large amount of aromatic components, which plays a vital role in the operating efficiency of the ethylene cracking furnace.

[0003] Hydrocarbon raw materials and steam undergo thermal cracking reaction in high-temperature furnace tubes to produce small molecular target products such as ethylene and propylene. At the same time, it is accompanied by a large number of side reactions. The dehydrogenation of aromatic components produces by-products such as tar and coke, which has brought many adverse effects on ethylene production, resulting in a series of adverse effects such as reduced yield of target products, decreased processing capacity of the device, increased energy consumption and shortened operation cycle.

[0004] The cracking coking mechanism of aromatics and its influencing factors are very complex, but the most recognized ones include: catalytic coking, gas phase coking and free radical coking. Gas phase coking is the main form of coking, which refers to the coke generated in the main body of the gas flow. Aromatics are very important intermediate substances in gas phase coking. Some of these aromatics come from the raw materials themselves, and some are generated through trimerization reactions. The coking process can be expressed as:

[0005]

[0006] In recent years, a variety of coking inhibition technologies have been developed to combat aromatic coking, including changing cracking reaction conditions, hydrothermal cracking, pretreatment of cracking raw materials, surface treatment of furnace tubes, and addition of coking inhibitors. The use of new cracking technologies and furnace tube surface treatment processes requires huge investments in replacing cracking furnaces and furnace tubes, which is difficult to achieve in a short period of time. In addition, chemical market prices change rapidly, and investment returns cannot be guaranteed.

[0007] Changing the dilution ratio and steam of cracking is helpful to reduce coking, but the effect is limited, and the increased dilution steam affects the processing capacity and output of the device and increases the energy consumption of the device. Therefore, adding coking inhibitors to the cracking raw materials is a generally recognized and most effective method.

[0008] The reported coking inhibitors mainly include sulfur and phosphorus compounds, metal salt compounds, and organic polysiloxane compounds. For example, Chinese invention patent CN101294100A discloses a method for inhibiting coking in a hydrocarbon steam cracking device, which requires the use of at least one of silica sol, aluminum sol and titanium sol to pretreat the furnace tube, and then inject sulfur and phosphorus compound inhibitors during the cracking process. Existing sulfur and phosphorus oil-soluble inhibitors are mainly used for catalytic coking before or at the initial stage of feeding. Sulfur and phosphorus inhibitors can form a layer of passivation on the surface of the furnace tube before the coking product is produced, slowing down the process of catalytic coking. However, as the cracking furnace runs to the middle and late stages, the catalytic coking weakens, the gas phase coking increases, and the coke layer will still gradually thicken. Sulfur and phosphorus oil-soluble inhibitors cannot eliminate the coke layer of gas phase coking.

[0009] Chinese invention patent CN1367225A discloses a method for inhibiting coking in a hydrocarbon steam cracking device. After the furnace tube is decoked, potassium, lithium silicate, borate, or potassium, magnesium, calcium, and barium nitrate inorganic salt coking inhibitor is added to the water vapor before resuming feeding, and the duration is 1-3 hours. However, inorganic salts are incompatible with hydrocarbon materials. During the addition process, it is very easy to cause the inhibitor to be unevenly distributed in the pipeline, resulting in the deposition of inorganic salts in the furnace tube, and even blocking the furnace tube, causing the cracking furnace to be shut down unplanned, seriously affecting the stable operation of production. In addition, the use method of the inhibitor is very important for the effect of inhibiting coking and the stable operation of the cracking furnace. If the injected inhibitor solution is not vaporized quickly, the liquid is sprayed onto the high-temperature furnace tube, and the furnace tube will be fatigued and damaged due to the creep stress of continuous shrinkage and thermal expansion; if too much inorganic salt inhibitor is injected, it may cause the deposition of the inhibitor in the furnace tube or the fall of large pieces of coke to block the furnace tube.

[0010] Therefore, it is necessary to develop a new coking inhibitor that can reduce the coking in the heavy oil cracking furnace and solve the problems existing in the existing coking inhibitors. Summary of the invention

[0011] The technical problem to be solved by the present invention is: to overcome the shortcomings of the prior art and provide a fatty acid salt coking inhibitor and a preparation method and application thereof. The coking inhibitor of the present invention is aimed at cracking furnaces of heavy raw materials such as diesel and tail oil, and can be directly added to the cracking raw oil without the need to separately add injection equipment such as inhibitor nozzles, thereby reducing unnecessary blockage risks and reducing the complexity of the process; and compared with existing sulfur-phosphorus-containing oil-soluble inhibitors, the coking inhibitor of the present invention has good decoking performance for mid- and late-stage gas-phase coking.

[0012] The technical solution of the present invention is:

[0013] In a first aspect, the present invention provides a method for preparing a fatty acid salt coking inhibitor, wherein a fatty acid is reacted with a potassium compound to obtain the coking inhibitor; wherein the fatty acid is a mixture of one or both of oleic acid and stearic acid, and the potassium compound is potassium hydroxide, potassium carbonate or potassium bicarbonate.

[0014] Since fatty acids have polar head groups that can connect to metallic potassium ions, they can be used as surfactants and softeners; at the same time, they also have non-polar chains that allow them to dissolve in organic solvents.

[0015] Preferably, the fatty acid is a mixture of oleic acid and stearic acid.

[0016] Preferably, in the fatty acid, the molar ratio of oleic acid to stearic acid is 1:(0.5-1.5).

[0017] Preferably, the molar ratio of the fatty acid to the potassium element is 1:(1.0-1.1).

[0018] In the second aspect, the present invention provides a coking inhibitor prepared by the above-mentioned preparation method, which has both lipophilicity and hydrophilicity and can slow down the coking of heavy oil cracking furnace tubes. The coking inhibitor can be directly added to oil raw materials or water, and its lipophilic groups can capture coking precursors and combine with them, thereby inhibiting further carbonization of the coking precursors.

[0019] The mechanism of action of the coking inhibitor is as follows: since the inhibitor contains both a polar head group (metal cation) and a lipophilic group of a non-polar chain such as stearic acid, it can be dissolved in an organic solvent. The lipophilic group of the coking inhibitor can combine with the precursor of tar to form a mixture of tar and the coking inhibitor, thereby preventing the tar from further dehydrogenating and condensing to form a side reaction of coke. At the same time, the mixture of the two undergoes catalytic gasification in the presence of hot steam, that is, the coking inhibitor releases an alkali metal oxide, which can catalyze the conversion of the coking precursor into carbon monoxide and hydrogen, thereby eliminating and slowing down the deposition of coke on the tube wall.

[0020] The reaction mechanism of the coking inhibitor of the present invention in inhibiting coking is:

[0021]

[0022] The coking inhibitor can not only inhibit early coking, but also reduce and remove the existing coke layer. The application of the coking inhibitor in the steam cracking ethylene production unit solves the problems of short operation cycle, short service life of cracking furnace tubes, high energy consumption and low production efficiency in the prior art. It can significantly reduce the coke amount in the furnace tubes, reduce the tube wall temperature, and greatly extend the operation cycle of the cracking furnace.

[0023] The coking inhibitor of the present invention does not require the use of complicated auxiliary facilities such as nozzles, thereby preventing inhibitor deposition or fatigue damage caused by shrinkage, thermal expansion and creep of the furnace tube caused by the inhibitor.

[0024] In a third aspect, the present invention also provides the use of the above-mentioned fatty acid salt coking inhibitor, which is used to slow down the coking of heavy oil cracking furnace tubes.

[0025] Among them, the coking inhibitor of the present invention is applicable to cracking furnaces SRT-III, SRT-IV, GK-VI, CBL industrial furnaces and simulated cracking test furnaces.

[0026] The coking inhibitor of the present invention is applicable to heavy oils such as diesel or hydrocracking tail oil. When the cracking furnace uses liquid hydrocarbon raw materials, the inhibitor can be added to the liquid hydrocarbon raw materials or to the dilution steam; when the cracking furnace uses gaseous raw materials, the inhibitor can be added to the dilution steam.

[0027] The specific method of using the coking inhibitor of the present invention is:

[0028] The coking inhibitor is injected into the cracking feedstock and enters the heavy oil cracking furnace together with the cracking feedstock. For example, the inhibitor can be injected into the cracking feedstock at the inlet or outlet of the raw material pump of the heating furnace, preferably at the inlet of the raw material pump, with the help of the mechanical stirring action of the raw material pump to obtain a good stirring and mixing effect; the inhibitor can also be pre-mixed with part of the cracking feedstock in advance, and then the mixture is injected into the cracking feedstock at the inlet or outlet of the raw material pump of the heating furnace through a pipeline.

[0029] The inhibitor can also be injected into the dilution steam in advance to form a mixture of inhibitor and steam, which then enters the heavy oil cracking furnace together.

[0030] Preferably, the injection amount of the coking inhibitor is 50-100 ppm of the input amount of the cracking raw material.

[0031] When the coking inhibitor of the present invention is used, the injection method of the coking inhibitor can be a continuous injection method or an intermittent injection method. Moreover, when the inhibitor is injected by the continuous injection method or the intermittent injection method, the injection concentration of the inhibitor, the start or stop of the injection of the inhibitor, all need to be determined according to the temperature of the tube wall of the radiation section of the cracking furnace.

[0032] Among them, the continuous injection method refers to the continuous injection of small doses of inhibitors at the beginning of the cracking reaction of hydrocarbon feedstock in the cracking furnace, which can inhibit the rapid rise in the furnace tube wall temperature in the initial stage of the cracking furnace feeding.

[0033] The intermittent injection method means that no inhibitors are injected in the early stage of the cracking furnace operation. After the coke layer is gradually generated in the tube wall of the radiation section, the thermal resistance of the tube wall increases, and the tube wall temperature rises to above 1000℃, the system starts to inject the inhibitor; the injection is continued for 24-120h. At this time, the coke layer on the tube wall is significantly thinned or reduced, and the thermal resistance of the tube wall is reduced. When the tube wall temperature drops significantly by about 30-50℃, the injection of the inhibitor is stopped; after a period of operation, when the tube wall temperature rises significantly to 1000℃ again, the inhibitor is injected again until the injection of the inhibitor cannot effectively reduce the tube wall temperature.

[0034] Compared with existing inorganic salt inhibitors or low molecular weight salt inhibitors, the fatty acid salt coking inhibitor of the present invention has good oil solubility, can be directly added to the raw oil, and enters the cracking furnace tube with the raw oil, without the need to separately add injection equipment such as inhibitor nozzles.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. In the actual operation of industrial cracking furnaces, existing inorganic salt inhibitors or low molecular weight organic inhibitors have poor oil solubility and need to be equipped with inhibitor nozzles separately to help distribute them into the furnace tubes. In actual operation, since the nozzle of the inhibitor injection nozzle is relatively small, generally with a diameter of 0.5-5mm, once iron filings or other debris are mixed into the inhibitor storage tank and pipeline, the inhibitor injection nozzle will be blocked. Once blocked, the inhibitor injection will fail. In addition, multiple groups of inhibitor nozzles need to work in parallel at the same time. In actual operation, there is often a problem of too large or too small flow rate of a nozzle, resulting in uneven injection dosage of different nozzles. The temperature of the corresponding furnace tube with a smaller injection dosage is significantly higher than that of other groups, triggering the over-temperature shutdown of the cracking furnace, and the over-temperature of a single group of furnace tubes in the cracking furnace will inevitably affect the overall operation cycle. The coking inhibitor of the present invention is aimed at cracking furnaces for heavy raw materials such as diesel and tail oil, and can be directly added to the cracking raw oil and enter the cracking furnace tubes with the cracking raw oil. The process is mature and stable, and there is no need to separately add injection equipment such as inhibitor nozzles, thereby reducing unnecessary blockage risks and reducing the complexity of the process. At the same time, the inhibitor has good emulsification properties, and within the set concentration range, inhibitor deposition will not occur, and fatigue damage will not occur due to shrinkage, thermal expansion, creep, etc. of the furnace tubes caused by injection, thereby increasing operational stability.

[0037] 2. Compared with the existing sulfur-phosphorus oil-soluble inhibitors, the coking inhibitor of the present invention has good decoking performance for gas phase coking in the middle and late stages. The existing sulfur-phosphorus oil-soluble inhibitors are mainly used for catalytic coking before or at the initial stage of feeding. The sulfur-phosphorus inhibitors can form a layer of passivation on the surface of the furnace tube before the coking product is produced, slowing down the process of catalytic coking. However, as the cracking furnace runs to the middle and late stages, the catalytic coking weakens, the gas phase coking increases, and the coke layer will still gradually thicken. The sulfur-phosphorus oil-soluble inhibitors cannot eliminate the coke layer of gas phase coking. In the operation of an actual industrial cracking furnace, the coking inhibitor of the present invention can be used in different stages of the cracking furnace, including the early, middle and late stages. The best application scenario is the middle and late stages of the operation of the cracking furnace, because at this time, part of the coke layer has accumulated in the furnace tube of the cracking furnace, and the purpose of removing the existing coke layer can be achieved by injecting the coking inhibitor of the present invention. Of course, the coking inhibitor of the present invention can also be injected in the early stage of the operation of the cracking furnace, which can also prevent the increase of the coke layer and extend the operation cycle of the cracking furnace.

[0038] 3. When the coking inhibitor of the present invention is used in a steam cracking ethylene production device, it can significantly reduce the coke content of the furnace tube and greatly extend the operation cycle of the cracking furnace.

[0039] 4. When the coking inhibitor of the present invention is used in a steam cracking ethylene production device, it can reduce the cracking furnace tube wall temperature and reduce the number of cracking furnace coking, thereby extending the life of the cracking furnace tube and saving the cracking furnace coking energy consumption and the cost of replacing the cracking furnace tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the thermal cracking device used in the embodiment of the present invention.

[0041] In the figure, 1, cracking furnace; 101, thermocouple; 2, quench cooler; 3, gas-liquid separation tank. DETAILED DESCRIPTION

[0042] In order to enable persons skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0043] The coking inhibitors in the following examples were prepared by the following method:

[0044] The fatty acid reacts with potassium compounds to obtain a coking inhibitor.

[0045] The fatty acid is one or a mixture of oleic acid and stearic acid.

[0046] The potassium compound is potassium hydroxide, potassium carbonate or potassium bicarbonate.

[0047] Generally speaking, fatty acids with a small carbon number react faster than those with a large carbon number (C12>C14>C16>C18); at the same time, the reaction rate of saturated fatty acids is higher than that of monounsaturated fatty acids and polyunsaturated fatty acids. Although unsaturated fatty acids react slowly, they have the function and effect of binding with different tar molecules. The reaction must be carried out under full mixing, which requires continuous stirring to allow the reactants to fully mix and react. After the reaction is complete, the coking inhibitor product is obtained by cooling.

[0048] The coking inhibitor prepared in the following examples participates in the following thermal cracking process:

[0049] Use Figure 1 The thermal cracking device shown has a cracking reaction temperature of 800°C, a cracking raw material of diesel, a feed rate of 5kg / h, a dilution ratio of 0.8, and a residence time of 0.40s. The reaction materials need to be heated by the feed system and the cracking furnace 1, and then enter the quencher 2. The liquid phase product is collected from the product separation lower port of the gas-liquid separation tank 3, and the hydrocarbon composition of the cracked gas after the reaction and the content of carbon monoxide and carbon dioxide are sampled and analyzed from the venting port. When the tube wall temperature (TMT) of the cracking furnace 1 reaches the upper limit of 1100°C, the feed is stopped and the operation time is recorded as the evaluation basis for the length of the operation cycle.

[0050] The coking inhibitor in the embodiment of the present invention can be injected into steam or water from injection port 1, or injected into the cracking raw material from injection port 2. However, the inorganic salt inhibitor in the comparative example can only be injected into steam or water from injection port 1.

[0051] After injecting the coking inhibitor, the temperature of the cracking furnace 1 is raised to above 800°C, and air is mixed in and maintained at 800°C. The oxygen content of the coking gas at the outlet of the quencher 2 is detected by the coking controller. At the beginning, the carbon monoxide and carbon dioxide contents are relatively high, reaching the upper limit of the carbon monoxide and carbon dioxide gas analyzer detection of 25%; as the coking process continues, the carbon monoxide and carbon dioxide contents gradually decrease, and the oxygen content continues to increase until it reaches a level equivalent to the oxygen content of the air. At this time, the coking operation is completed and the total coking operation time is recorded. During the coking operation, the temperature indication of the thermocouple 101 in the furnace tube of the cracking furnace 1 must be continuously detected. It is required not to exceed the upper temperature limit of 1100°C of the 2520 material. It is generally set within 1000°C. Once it approaches this temperature, the inflow of coking air is reduced to control the coking reaction.

[0052] Example 1

[0053] The preparation method of the coking inhibitor of this embodiment is as follows: a mixed fatty acid composed of oleic acid and stearic acid in a molar ratio of 1:1 is reacted with potassium hydroxide, wherein the theoretical molar ratio of potassium hydroxide to the mixed fatty acid is 1:1, but considering the reversibility of the esterification reaction, in order to allow the fatty acid to react completely, the amount of potassium hydroxide should be slightly larger, so the molar ratio of potassium hydroxide to the mixed fatty acid in this embodiment is 1.05:1, and the coking inhibitor is finally obtained.

[0054] Using the above Figure 1 The thermal cracking process shown adopts a continuous injection method. When the cracking reaction of the hydrocarbon feedstock is fed into the cracking furnace 1, a coking inhibitor is continuously injected in small doses. The injection amount is 80ppm of the cracking hydrocarbon feedstock input to complete a feeding operation cycle: the cracking reaction temperature is 800°C, the cracking feedstock is diesel, the feed amount is 5kg / h, the dilution ratio is 0.8, and the residence time is 0.40s; when the TMT of the cracking furnace 1 reaches the upper limit of 1100°C, the feeding is stopped, and the operation time is recorded as 80h; the carbon monoxide and carbon dioxide contents are 0.09% and 0.07% respectively; the charring time is 0.4h.

[0055] Example 2

[0056] The difference from Example 1 is that this example adopts an intermittent injection method, injecting a coking inhibitor 20 hours into the middle of the cracking reaction of the hydrocarbon feedstock in the cracking furnace 1, and examining the effects of intermittent and continuous injection on the operating cycle.

[0057] Complete a feeding operation cycle: cracking reaction temperature 800℃, cracking raw material is diesel, feeding amount is 5kg / h, dilution ratio is 0.8, residence time is 0.40s; when the cracking furnace 1TMT reaches the upper limit of 1100℃, the feeding is stopped, and the operation time is recorded as 75h; the carbon monoxide and carbon dioxide contents are 0.05% and 0.03% respectively before injection, and are 0.09% and 0.07% respectively after injection; the charring time is 0.4h.

[0058] Comparative Example 1

[0059] The difference from Example 1 is that in Comparative Example 1, no coking inhibitor is injected.

[0060] Complete a feeding operation cycle: cracking reaction temperature 800℃, cracking raw material is diesel, feeding amount is 5kg / h, dilution ratio is 0.8, residence time is 0.40s; when the cracking furnace 1TMT reaches the upper limit of 1100℃, the feeding is stopped, the recorded operation time is 40h, the carbon monoxide and carbon dioxide contents are 0.05% and 0.03% respectively; the charring time is 1h.

[0061] It can be seen from Examples 1-2 and Comparative Example 1 that when the coking inhibitor of the present invention is injected into the cracking furnace 1 by the continuous injection method, the operation cycle is extended by 1 times compared with Comparative Example 1 in which the coking inhibitor is not injected, and the coking time is reduced by 60%, indicating that the coking inhibitor of the present invention has an obvious coking inhibition effect when used by the continuous injection method. When the coking inhibitor of the present invention is injected into the cracking furnace 1 by the intermittent injection method, the operation cycle is extended by 0.88 times compared with Comparative Example 1 in which the coking inhibitor is not injected, and the coking time is reduced by 60%. Therefore, it can be seen from Examples 1-2 and Comparative Example 1 that the coking inhibitor of the present invention has an obvious coking inhibition effect in both the early and middle and late stages of operation.

[0062] Comparative Example 2

[0063] The difference from Example 1 is that Comparative Example 2 uses a potassium carbonate inhibitor (ie, an inorganic potassium salt inhibitor).

[0064] A continuous injection method is adopted. Potassium carbonate is continuously injected in small doses at the beginning of the cracking reaction of the hydrocarbon raw material into the cracking furnace 1. The injection amount is 80ppm of the cracking hydrocarbon raw material input amount. A feeding operation cycle is completed: the cracking reaction temperature is 800℃, the cracking raw material is diesel, the feeding amount is 5kg / h, the dilution ratio is 0.8, and the residence time is 0.40s. During the experiment, the carbon monoxide and carbon dioxide contents are 0.12% and 0.08% respectively, which are significantly higher than those of comparative example 1. This shows that the inorganic potassium salt inhibitor also plays a role in eliminating coke. However, because the inlet pressure of the cracking furnace 1 increases rapidly, it is judged that the furnace tube is blocked. Although the TMT of the cracking furnace 1 does not reach the upper limit of 1100℃, the feeding is also stopped. The recorded operation time is 30h and the charring time is 0.6h. The furnace tube of the cracking furnace 1 is disassembled, and the furnace tube is dredged with pure water. The composition of the aqueous solution is collected and analyzed. The result shows potassium carbonate, which shows that the inorganic potassium salt inhibitor lacks oil solubility and is easily unevenly distributed, resulting in deposition in the furnace tube and blocking the furnace tube.

[0065] Comparative Example 3

[0066] The difference from Example 1 is that Comparative Example 3 uses a dimethyl disulfide inhibitor (ie, an organic sulfur-phosphorus inhibitor).

[0067] A continuous injection method was adopted. When the cracking reaction of hydrocarbon feedstock was started in the cracking furnace 1, dimethyl disulfide was continuously injected in small doses. The injection amount was 80 ppm of the cracking hydrocarbon feedstock, and one feeding operation cycle was completed: the cracking reaction temperature was 800°C, the cracking feedstock was diesel, the feeding amount was 5 kg / h, the dilution ratio was 0.8, and the residence time was 0.40 s. When the TMT of the cracking furnace 1 reached the upper limit of 1100°C, the feeding was stopped, and the operation time was recorded as 60 h. The carbon monoxide and carbon dioxide contents were 0.05% and 0.03% respectively, and the charring time was 0.7 h.

[0068] Comparative Example 4

[0069] The difference from Comparative Example 3 is that Comparative Example 4 adopts an intermittent injection method, and dimethyl disulfide is injected 20 hours in the middle of the cracking reaction of the hydrocarbon feedstock into the cracking furnace 1, and the injection amount is 80 ppm of the cracking hydrocarbon feedstock input.

[0070] Complete a feeding operation cycle: cracking reaction temperature 800℃, cracking raw material is diesel, feeding amount is 5kg / h, dilution ratio is 0.8, residence time is 0.40s; when the cracking furnace 1TMT reaches the upper limit of 1100℃, the feeding is stopped, the recorded operation time is 45h, the carbon monoxide and carbon dioxide contents are 0.05% and 0.03% respectively, and the charring time is 0.9h.

[0071] It can be seen from Comparative Examples 1, 3-4 that organic sulfur and phosphorus inhibitors are more effective in inhibiting coking in the early stage of operation, but the effect is not obvious in the middle and late stages.

[0072] Example 3

[0073] The difference from Example 1 is that in Example 3, when preparing the coking inhibitor, only palmitic acid is used as the fatty acid, wherein the theoretical molar ratio of potassium hydroxide to palmitic acid is 1:1. However, considering the reversibility of the esterification reaction, in order to allow the fatty acid to react completely, the amount of potassium hydroxide should be slightly larger. Therefore, in this example, the molar ratio of potassium hydroxide to palmitic acid is 1.05:1, and the coking inhibitor is finally obtained.

[0074] A continuous injection method is adopted. Potassium palmitate is continuously injected in small doses at the beginning of the cracking reaction of hydrocarbon raw materials into the cracking furnace 1. The injection amount is 80ppm of the cracking hydrocarbon raw material input to complete a feeding operation cycle: the cracking reaction temperature is 800°C, the cracking raw material is diesel, the feeding amount is 5kg / h, the dilution ratio is 0.8, and the residence time is 0.40s; when the TMT of the cracking furnace 1 reaches the upper limit of 1100°C, the feeding is stopped, and the recorded operation time is 50h, which is 0.25 times longer than that of comparative example 1; the carbon monoxide and carbon dioxide contents are 0.05% and 0.03% respectively before the injection, and are 0.07% and 0.04% respectively after the injection; the charring time is 0.8h, which is 20% less than that of comparative example 1.

[0075] It can be seen from Example 1, Comparative Example 1 and Example 3 that the coking inhibitor prepared using only palmitic acid and potassium hydroxide has a slight coking inhibition effect, but its coking inhibition effect is significantly poorer than that using two fatty acids at the same time. This is because the potassium palmitate coking inhibitor prepared in Example 3 is targeted at light oil coke, while the mixed fatty acid potassium coking inhibitor prepared in Example 1 is targeted at heavy oil coke. Light oil is relatively light relative to heavy oil, and its coke is relatively high in saturation, while the carbon number of potassium palmitate is comparable to the average carbon number distribution of light oil, so it has a strong binding force with the coke of light oil and a good decoking effect, while the decoking effect on the coke of heavy oil is relatively poor.

[0076] Example 4

[0077] The difference from Example 1 is that in Example 4, when preparing the coking inhibitor, only oleic acid is used as the fatty acid, wherein the theoretical molar ratio of potassium hydroxide to oleic acid is 1:1. However, considering the reversibility of the esterification reaction, in order to allow the oleic acid to react completely, the amount of potassium hydroxide should be slightly larger. Therefore, in this example, the molar ratio of potassium hydroxide to oleic acid is 1.05:1, and the coking inhibitor is finally obtained.

[0078] A continuous injection method is adopted. Potassium oleate is continuously injected in small doses at the beginning of the cracking reaction of the hydrocarbon raw material into the cracking furnace 1. The injection amount is 80ppm of the cracking hydrocarbon raw material input to complete a feeding operation cycle: the cracking reaction temperature is 800°C, the cracking raw material is diesel, the feeding amount is 5kg / h, the dilution ratio is 0.8, and the residence time is 0.40s; when the TMT of the cracking furnace 1 reaches the upper limit of 1100°C, the feeding is stopped, and the recorded operation time is 65h, which is 0.52 times longer than that of comparative example 1; the carbon monoxide and carbon dioxide contents are 0.05% and 0.03% respectively before the injection, and are 0.07% and 0.04% respectively after the injection; the charring time is 0.61h, which is reduced by 40% compared with comparative example 1.

[0079] It can be seen from Example 1, Comparative Example 1 and Example 4 that the use of potassium oleate coking inhibitor alone also has a certain coking inhibition effect, but its coking inhibition effect is poorer than that of the coking inhibitor using two fatty acids at the same time.

[0080] Example 5

[0081] The difference from Example 1 is that in Example 4, when preparing the coking inhibitor, only stearic acid is used as the fatty acid, wherein the theoretical molar ratio of potassium hydroxide to stearic acid is 1:1. However, considering the reversibility of the esterification reaction, in order to allow the stearic acid to react completely, the amount of potassium hydroxide should be slightly larger. Therefore, in this example, the molar ratio of potassium hydroxide to stearic acid is 1.05:1, and the coking inhibitor is finally obtained.

[0082] A continuous injection method is adopted. Potassium stearate is continuously injected in small doses at the beginning of the cracking reaction of the hydrocarbon raw material into the cracking furnace 1. The injection amount is 80ppm of the cracking hydrocarbon raw material input to complete a feeding operation cycle: the cracking reaction temperature is 800°C, the cracking raw material is diesel, the feeding amount is 5kg / h, the dilution ratio is 0.8, and the residence time is 0.40s; when the TMT of the cracking furnace 1 reaches the upper limit of 1100°C, the feeding is stopped, and the recorded operation time is 70h, which is 0.75 times longer than that of comparative example 1; the carbon monoxide and carbon dioxide contents are 0.05% and 0.03% respectively before the injection, and are 0.07% and 0.04% respectively after the injection; the scorching time is 0.60h, which is 40% less than that of comparative example 1.

[0083] It can be seen from Example 1, Comparative Example 1 and Example 5 that the use of potassium stearate coking inhibitor alone also has a certain coking inhibition effect, but its coking inhibition effect is poorer than that of the coking inhibitor using two fatty acids at the same time.

[0084] Example 6

[0085] The preparation method of the coking inhibitor of this embodiment is as follows: a mixed fatty acid composed of oleic acid and stearic acid in a molar ratio of 1:1.5 is reacted with potassium carbonate, wherein the theoretical molar ratio of potassium carbonate to the mixed fatty acid is 0.5:1. However, considering the reversibility of the esterification reaction, in order to allow the fatty acid to react completely, the amount of potassium carbonate should be slightly larger. Therefore, in this embodiment, the molar ratio of potassium carbonate to the mixed fatty acid is 0.52:1, and the coking inhibitor is finally obtained.

[0086] Using the above Figure 1 The thermal cracking process shown adopts a continuous injection method. When the cracking reaction of the hydrocarbon feedstock is fed into the cracking furnace 1, a coking inhibitor is continuously injected in small doses. The injection amount is 80ppm of the cracking hydrocarbon feedstock input to complete a feeding operation cycle: the cracking reaction temperature is 800°C, the cracking feedstock is diesel, the feed amount is 5kg / h, the dilution ratio is 0.8, and the residence time is 0.40s; when the TMT of the cracking furnace 1 reaches the upper limit of 1100°C, the feeding is stopped, and the operation time is recorded as 80h; the carbon monoxide and carbon dioxide contents are 0.09% and 0.07% respectively; the charring time is 0.4h.

[0087] Example 7

[0088] The difference from Example 4 is that this example adopts an intermittent injection method, and injects the coking inhibitor 20 hours in the middle of the cracking reaction of the hydrocarbon feedstock in the cracking furnace 1.

[0089] Complete a feeding operation cycle: cracking reaction temperature 800℃, cracking raw material is diesel, feeding amount is 5kg / h, dilution ratio is 0.8, residence time is 0.40s; when the cracking furnace 1TMT reaches the upper limit of 1100℃, the feeding is stopped, and the operation time is recorded as 75h; the carbon monoxide and carbon dioxide contents are 0.05% and 0.03% respectively before injection, and are 0.09% and 0.07% respectively after injection; the charring time is 0.4h.

[0090] Example 8

[0091] The preparation method of the coking inhibitor of this embodiment is as follows: a mixed fatty acid composed of oleic acid and stearic acid in a molar ratio of 1:0.5 is reacted with potassium bicarbonate, wherein the theoretical molar ratio of potassium bicarbonate to the mixed fatty acid is 1:1, but considering the reversibility of the esterification reaction, in order to allow the fatty acid to react completely, the amount of potassium bicarbonate should be slightly larger, so in this embodiment, the molar ratio of potassium bicarbonate to the mixed fatty acid is 1.12:1, and the coking inhibitor is finally prepared.

[0092] Using the above Figure 1 The thermal cracking process shown adopts a continuous injection method. When the cracking reaction of the hydrocarbon feedstock is fed into the cracking furnace 1, a coking inhibitor is continuously injected in small doses. The injection amount is 80ppm of the cracking hydrocarbon feedstock input to complete a feeding operation cycle: the cracking reaction temperature is 800°C, the cracking feedstock is diesel, the feed amount is 5kg / h, the dilution ratio is 0.8, and the residence time is 0.40s; when the TMT of the cracking furnace 1 reaches the upper limit of 1100°C, the feeding is stopped, and the operation time is recorded as 80h; the carbon monoxide and carbon dioxide contents are 0.09% and 0.07% respectively; the charring time is 0.4h.

[0093] Example 9

[0094] The difference from Example 8 is that this example adopts an intermittent injection method, and injects the coking inhibitor 20 hours in the middle of the cracking reaction of the hydrocarbon feedstock in the cracking furnace 1.

[0095] Complete a feeding operation cycle: cracking reaction temperature 800℃, cracking raw material is diesel, feeding amount is 5kg / h, dilution ratio is 0.8, residence time is 0.40s; when the cracking furnace 1TMT reaches the upper limit of 1100℃, the feeding is stopped, and the operation time is recorded as 75h; the carbon monoxide and carbon dioxide contents are 0.05% and 0.03% respectively before injection, and 0.08% and 0.06% respectively after injection; the charring time is 0.45h.

[0096] Comparative Example 5

[0097] The preparation method of the coking inhibitor of Comparative Example 5 is as follows: a mixed fatty acid consisting of palm oil and stearic acid in a molar ratio of 1:1 is reacted with potassium hydroxide, wherein the theoretical molar ratio of potassium hydroxide to the mixed fatty acid is 1:1, but considering the reversibility of the esterification reaction, in order to allow the fatty acid to react completely, the amount of potassium hydroxide should be slightly larger, so the molar ratio of potassium hydroxide to the mixed fatty acid in this embodiment is 1.05:1, and a coking inhibitor is finally obtained.

[0098] Using the above Figure 1 The thermal cracking process shown adopts a continuous injection method. When the cracking reaction of the hydrocarbon feedstock is fed into the cracking furnace 1, a coking inhibitor is continuously injected in small doses. The injection amount is 80ppm of the cracking hydrocarbon feedstock input to complete a feeding operation cycle: the cracking reaction temperature is 800°C, the cracking feedstock is diesel, the feed amount is 5kg / h, the dilution ratio is 0.8, and the residence time is 0.40s; when the TMT of the cracking furnace 1 reaches the upper limit of 1100°C, the feeding is stopped, and the operation time is recorded as 60h; the carbon monoxide and carbon dioxide contents are 0.07% and 0.05% respectively; the charring time is 0.7h.

[0099] Comparative Example 6

[0100] The difference from Comparative Example 5 is that this embodiment adopts an intermittent injection method, and injects the coking inhibitor 20 hours in the middle of the cracking reaction of the hydrocarbon feedstock in the cracking furnace 1.

[0101] Complete a feeding operation cycle: cracking reaction temperature 800℃, cracking raw material is diesel, feeding amount is 5kg / h, dilution ratio is 0.8, residence time is 0.40s; when the cracking furnace 1TMT reaches the upper limit of 1100℃, the feeding is stopped, and the operation time is recorded as 65h; the carbon monoxide and carbon dioxide contents are 0.05% and 0.03% respectively before injection, and 0.07% and 0.05% respectively after injection; the charring time is 0.55h.

[0102] It can be seen from Examples 1-2 and Comparative Examples 5-6 that the mixed fatty acid salt coking inhibitor prepared from oleic acid and stearic acid in Example 1-2 has a longer operating time than the mixed fatty acid salt coking inhibitor prepared from palmitic acid and stearic acid in Comparative Example 5. Therefore, it can be seen that the mixed fatty acid salt coking inhibitor prepared from oleic acid and stearic acid has a better effect.

[0103] Experimental Example 1

[0104] Without adding any inhibitors, Figure 1 In the thermal cracking process shown, the cracking reaction temperature is 800°C, the cracking raw material is diesel, the feed rate is 5kg / h, the dilution ratio is 0.8, and the residence time is 0.40s; when the cracking furnace runs for 20h, the cracking products of the cracking furnace are collected, and the yield of the cracking products is analyzed by chromatography. The results are shown in Table 1.

[0105] Experimental Example 2

[0106] The mixed fatty acid salt inhibitor of Example 1 is used as follows Figure 1 The thermal cracking process shown adopts a continuous injection method. When the cracking reaction of the hydrocarbon feedstock is put into the cracking furnace 1, a coking inhibitor is continuously injected in small doses. The injection amount is 80ppm of the cracking hydrocarbon feedstock input. The cracking reaction temperature is 800°C. The cracking feedstock is diesel, the feed amount is 5kg / h, the dilution ratio is 0.8, and the residence time is 0.40s. When the cracking furnace runs for 20h, the cracking products of the cracking furnace are collected, and the yield of the cracking products is analyzed by chromatography. The results are shown in Table 1.

[0107] Table 1 The yield of the pyrolysis products of Experimental Example 1 and Experimental Example 2

[0108]

[0109] It can be seen from Table 1 that under the same raw materials and process conditions, the cracking yields of Experimental Example 1 and Experimental Example 2 are very close, and the main technical and economic indicators of the device such as ethylene, propylene and triene yields of Experimental Example 2 are slightly higher than those of Experimental Example 1. This is because the inhibitor slows down the coking side reaction and is conducive to the formation of the target product. This proves that the coking inhibitor of the present invention will not have a negative impact on the technical and economic indicators of the device.

[0110] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, and all of these shall be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for preparing a fatty acid salt coking inhibitor, characterized in that: The coking inhibitor is obtained by reacting a fatty acid with a potassium compound; wherein the fatty acid is one or a mixture of oleic acid and stearic acid, and the potassium compound is potassium hydroxide, potassium carbonate or potassium bicarbonate.

2. The method for preparing the fatty acid salt coking inhibitor according to claim 1, wherein The fatty acid is a mixture of oleic acid and stearic acid.

3. The method for preparing the fatty acid salt coking inhibitor according to claim 2, characterized in that: Among the fatty acids, the molar ratio of oleic acid to stearic acid is 1:(0.5-1.5).

4. The method for preparing the fatty acid salt coking inhibitor according to claim 1, characterized in that: The molar ratio of the fatty acid to the potassium element is 1:(1.0-1.1).

5. A fatty acid salt coking inhibitor prepared by the preparation method according to any one of claims 1 to 4.

6. The use of the fatty acid salt coking inhibitor as claimed in claim 5, characterized in that: The coking inhibitor is used to slow down the coking of heavy oil cracking furnace tubes.

7. The use of the fatty acid salt coking inhibitor according to claim 6, characterized in that: The coking inhibitor is injected into the cracking feedstock and enters the heavy oil cracking furnace together with the cracking feedstock; or the coking inhibitor is injected into the dilution steam and enters the heavy oil cracking furnace together with the dilution steam.

8. The use of the fatty acid salt coking inhibitor according to claim 6, characterized in that: The injection amount of coking inhibitor is 50-100ppm of the cracking raw material input.

9. The use of the fatty acid salt coking inhibitor according to claim 6, characterized in that: The coking inhibitor is injected by a continuous injection method or an intermittent injection method.

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