Fatty acid salt coking inhibitors, methods of making and using same

Abstract

The application discloses a kind of fatty acid salt coking inhibitors and its preparation method and application, belong to coking inhibitor technical field.The technical scheme is: fatty acid is reacted with potassium compound, namely the coking inhibitor is obtained;Wherein, fatty acid is the mixture of one or two of oleic acid and stearic acid, and potassium compound is potassium hydroxide, potassium carbonate or potassium bicarbonate.The coking inhibitor of the application can be directly added to the cracking raw material oil for the cracking furnace of diesel and tail oil and other heavy raw materials, without needing to separately add inhibitor nozzle and other injection equipment, reduce unnecessary risk of blockage, reduce the complexity of process;And compared with the existing sulfur and phosphorus-containing oil-soluble inhibitor, the coking inhibitor of the application has good mid-late gas phase coking removal performance.

Description

TECHNICAL FIELD

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

[0002] More than 80% of the global ethylene production adopts the tubular furnace steam cracking process, and the hydrocarbon liquid raw material often contains a large amount of aromatic components, which has a crucial effect on the operation condition of the ethylene cracking furnace.

[0003] The hydrocarbon raw material and steam are subjected to thermal cracking reaction in a high-temperature furnace tube to generate small-molecule target products such as ethylene and propylene, accompanied by a large number of side reactions, and the dehydrogenation of aromatic components generates tar and coke and other by-products, which brings many adverse effects to ethylene production, resulting in a series of adverse effects such as a decrease in target product yield, a decrease in device processing capacity, an increase in energy consumption, and a shortening of the operation cycle.

[0004] The cracking and coking mechanism of aromatic substances and its influencing factors are very complex, but the currently recognized ones include catalytic coking, gas phase coking, and free radical coking. Among them, gas phase coking is the main coking form, which refers to the coke generated in the gas flow main body. Aromatic hydrocarbons are very important intermediates for gas phase coking, some of which come from the raw material itself, and some are generated by trimerization reaction. The coking process can be represented as:

[0005]

[0006] In view of the coking of aromatic hydrocarbons, various coking inhibition technologies have been developed in recent years, including changing the cracking reaction conditions, hydrogenation thermal cracking, cracking raw material pretreatment, furnace tube surface treatment, and adding coking inhibitors. The adoption of new cracking technologies and furnace tube surface treatment processes requires a huge investment to replace the cracking furnace and furnace tube, which is difficult to achieve in a short time, and the chemical market price changes quickly, so the investment income cannot be guaranteed.

[0007] Changing the dilution ratio of cracking and the steam measures is beneficial to reduce coking, but the effect is limited, and the increased dilution steam affects the processing capacity and yield of the device, and increases the energy consumption of the device. Therefore, adding coking inhibitors in the cracking raw material is a universally 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 patent CN101294100A discloses a method for inhibiting coking of a hydrocarbon steam cracking device, which requires at least one of silica sol, alumina sol, and titania sol to be used for pretreatment of the furnace tube, and then a sulfur and phosphorus compound inhibitor is injected during the cracking process. The existing sulfur and phosphorus-containing oil-soluble inhibitors are mainly used for catalytic coking before or at the initial stage of feeding. The sulfur and phosphorus-containing inhibitors can form a passivation layer on the surface of the furnace tube before the coking material is generated, thereby slowing down the process of catalytic coking. However, as the cracking furnace runs to the middle and later stages, catalytic coking is weakened, gas phase coking increases, and the coke layer still gradually thickens. The sulfur and phosphorus-containing oil-soluble inhibitors cannot eliminate the coke layer of gas phase coking.

[0009] Chinese patent CN1367225A discloses a method for inhibiting coking of a hydrocarbon steam cracking device. After the furnace tube is decoked, inorganic salt coking inhibitors such as potassium, lithium silicate, borate, or nitrate salts of potassium, magnesium, calcium, and barium are added to the water vapor before resuming feeding, and the duration is 1-3 h. However, the inorganic salts are not soluble in hydrocarbon materials, and during the addition process, the inhibitors are very easy to be unevenly distributed in the pipeline, which leads to deposition of the inorganic salts in the furnace tube, and even blockage of the furnace tube, causing unplanned shutdown of the cracking furnace and seriously affecting the stable operation of production. In addition, the method of using the inhibitors is very important for the effect of inhibiting coking and the smooth operation of the cracking furnace. If the injected inhibitor solution is not quickly gasified, the liquid is sprayed onto the high-temperature furnace tube, and the creep stress of the furnace tube due to continuous cold contraction and thermal expansion will cause fatigue damage. If the amount of injected inorganic salt inhibitors is too large, the inhibitors may be deposited in the furnace tube or large pieces of coke may fall off and block the furnace tube.

[0010] Therefore, it is necessary to develop a new coking inhibitor to slow down the coking of heavy oil cracking furnaces and solve the problems existing in the existing coking inhibitors. SUMMARY

[0011] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a fatty acid salt coking inhibitor, a preparation method and application thereof. The coking inhibitor of the present application can be directly added to the cracking raw oil for cracking furnaces of diesel and tail oil and other heavy feedstocks, without the need for separate injection equipment such as inhibitor nozzles, thereby reducing unnecessary blockage risks and process complexity. Compared with the existing sulfur and phosphorus-containing oil-soluble inhibitors, the coking inhibitor of the present application has good coke removal performance for gas phase coking in the middle and later stages.

[0012] The technical scheme of the present application is as follows:

[0013] In a first aspect, the present application provides a method for preparing a coking inhibitor of fatty acid salt, which comprises reacting a fatty acid with a potassium compound, wherein the fatty acid is a mixture of oleic acid and stearic acid, and the potassium compound is potassium hydroxide, potassium carbonate or potassium bicarbonate.

[0014] The fatty acid can be used as a surfactant and softener due to the presence of polar head group which can be connected with potassium ion, and it can be dissolved in organic solvent due to the non-polar chain.

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

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

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

[0018] In a second aspect, the present application provides a coking inhibitor with lipophilicity and hydrophilicity for reducing coking of heavy oil cracking furnace tube, which is prepared by the above method and can be directly added into oil raw material or water. The lipophilic group of the coking inhibitor can capture and combine with coking precursors to inhibit further carbon deposition of the coking precursors.

[0019] The mechanism of the coking inhibitor is that the polar head group (metal cation) and the lipophilic group with non-polar chain such as stearic acid exist in the inhibitor at the same time, so that the inhibitor can be dissolved in organic solvent. The lipophilic group of the coking inhibitor can combine with the precursors of tar to form a mixture of tar and coking inhibitor, thereby preventing the further side reaction of tar dehydrogenation condensation into coke. Meanwhile, the mixture of the two can be catalytically gasified in the presence of hot steam, i.e. the coking inhibitor releases alkali metal oxide which can catalyze the conversion of coking precursors into carbon monoxide and hydrogen, thereby eliminating and reducing the deposition of coke on the tube wall.

[0020] The reaction process of the coking inhibitor of the present application for inhibiting coking is as follows:

[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 device can solve the problems of short operation cycle, short service life of cracking furnace tube, high energy consumption and low production efficiency in the prior art, and can significantly reduce the amount of coke in the tube and the tube wall temperature, thereby greatly prolonging the operation cycle of the cracking furnace.

[0023] The coking inhibitor of the present application does not need to use complex auxiliary facilities such as nozzles, thereby being able to avoid the deposition of the inhibitor or the fatigue damage caused by the inhibitor making the furnace tube shrink in cold and expand in hot.

[0024] In a third aspect, the present application further provides the use of the above-mentioned fatty acid salt coking inhibitor for slowing down the coking of the heavy oil cracking furnace tube.

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

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

[0027] The specific use method of the coking inhibitor of the present application is as follows:

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

[0029] The inhibitor can also be injected into the dilution steam in advance to form a mixture of the inhibitor and the steam, and then enter 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 application is used, the injection method of the coking inhibitor can adopt continuous injection method or intermittent injection method. And when the inhibitor is injected by using the continuous injection method or the intermittent injection method, the injection concentration of the inhibitor, the start of injection or the stop of injection of the inhibitor all need to be determined according to the tube wall temperature of the radiant section of the cracking furnace.

[0032] Among them, the continuous injection method refers to continuously injecting the inhibitor in small doses from the beginning of the cracking reaction of the cracking furnace when the hydrocarbon raw material is put into the cracking furnace, which can inhibit the rapid rise of the tube wall temperature of the furnace tube in the initial stage of the cracking furnace.

[0033] The intermittent injection method refers to that in the early stage of the operation of the cracking furnace, no inhibitor is injected, and after the gradual formation of the coke layer in the radiation section pipe wall, the pipe wall thermal resistance increases, the pipe wall temperature rises to above 1000 DEG C, the system starts to inject the inhibitor; the injection lasts for 24-120h, at this time, the coke layer on the pipe wall is obviously thinned or reduced, the pipe wall thermal resistance is reduced, and when the pipe wall temperature obviously decreases by about 30-50 DEG C, the injection of the inhibitor is stopped; after a period of operation, when the pipe wall temperature obviously rises to 1000 DEG C again, the injection of the inhibitor is started again until the injection of the inhibitor cannot effectively reduce the pipe wall temperature.

[0034] Compared with the existing inorganic salt inhibitor or low molecular weight salt inhibitor, the fatty acid salt coking inhibitor has good oil solubility, can be directly added to the raw oil, and enters the cracking furnace pipe with the raw oil, and does not need to separately add injection equipment such as inhibitor nozzle.

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

[0036] 1. In the actual industrial cracking furnace operation, the existing inorganic salt inhibitor or low molecular weight organic inhibitor has poor oil solubility, and needs to be separately provided with an inhibitor nozzle to help it to be distributed into the furnace pipe. In actual operation, since the injection nozzle of the inhibitor has a small nozzle, generally 0.5-5mm in diameter, once iron filings or other impurities are mixed into the inhibitor storage tank and pipeline, the injection nozzle of the inhibitor will be blocked, and once blocked, the injection of the inhibitor will fail. Moreover, the inhibitor nozzle needs to be worked in parallel by multiple groups, and in actual operation, the problem of too large or too small flow of a certain nozzle often occurs, resulting in uneven injection amount of different nozzles, and the corresponding furnace pipe temperature of the smaller injection amount is obviously higher than that of other groups, triggering the over-temperature shutdown of the cracking furnace, and the over-temperature of a single furnace pipe of the cracking furnace will affect the overall operation cycle. The coking inhibitor of the present application can be directly added to the cracking raw oil and enter the cracking furnace pipe with the cracking raw oil, and the process is mature and stable, does not need to separately add injection equipment such as inhibitor nozzle, reduces unnecessary blockage risk, and reduces the complexity of the process; at the same time, the inhibitor has good emulsifying performance and will not cause inhibitor deposition or fatigue damage due to the injection of the inhibitor causing the cold shrinkage and thermal expansion of the furnace pipe, thereby increasing the operation stability.

[0037] 2. Compared with the existing oil-soluble inhibitor containing sulfur and phosphorus, the coking inhibitor of the present application has good decoking performance for mid-late stage gas phase coking. The existing oil-soluble inhibitor containing sulfur and phosphorus is mainly used for catalytic coking at the initial stage of feeding. The oil-soluble inhibitor containing sulfur and phosphorus can form a layer of passivation on the surface of the furnace tube before the coking material is generated, slowing down the process of catalytic coking. However, as the cracking furnace runs to the mid-late stage, catalytic coking decreases and gas phase coking increases, and the oil-soluble inhibitor containing sulfur and phosphorus cannot eliminate the coking layer of gas phase coking. In the actual operation of the industrial cracking furnace, the coking inhibitor of the present application can be used in different stages of the cracking furnace, including the initial stage, the middle stage and the late stage. The best application scenario is the mid-late stage of the operation of the cracking furnace, because at this time part of the coking layer has accumulated in the cracking furnace tube, and the coking inhibitor of the present application can be injected to achieve the purpose of removing the existing coking layer. Of course, the coking inhibitor of the present application can also be injected at the early stage of the operation of the cracking furnace, which can also prevent the increase of the coking layer and prolong the operation cycle of the cracking furnace.

[0038] 3. When the coking inhibitor of the present application is applied to the steam cracking ethylene production device, the amount of coke on the furnace tube can be significantly reduced, and the operation cycle of the cracking furnace can be greatly prolonged.

[0039] 4. When the coking inhibitor of the present application is applied to the steam cracking ethylene production device, the temperature of the cracking furnace tube wall can be reduced, the frequency of coking of the cracking furnace can be reduced, thereby prolonging the service life of the cracking furnace tube, saving the energy consumption of coking of the cracking furnace and the cost of replacing the cracking furnace tube. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a schematic diagram of a thermal cracking device used in an embodiment of the present application.

[0041] In the figure, 1 is a cracking furnace; 101 is a thermocouple; 2 is a quenching device; and 3 is a gas-liquid separation tank. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application.

[0043] The coking inhibitor of the following embodiments is prepared by the following method:

[0044] The fatty acid reacts with the potassium compound to obtain the coking inhibitor.

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

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

[0047] Generally, fatty acids with fewer carbon atoms react faster than those with more carbon atoms (C12>C14>C16>C18); saturated fatty acids also react faster than monounsaturated fatty acids and polyunsaturated fatty acids. Although unsaturated fatty acids react more slowly, they have the ability to bind with different tar molecules. The reaction must be carried out under conditions of thorough mixing, which requires continuous stirring to ensure the reactants are fully mixed and reacted. After the reaction is complete and cooled, the coking inhibitor product is obtained.

[0048] The coking inhibitors prepared in the following examples are used in the following pyrolysis process:

[0049] Adopting such Figure 1 The pyrolysis unit shown has a pyrolysis reaction temperature of 800℃, uses diesel oil as the feedstock at a rate of 5 kg / h, a dilution ratio of 0.8, and a residence time of 0.40 s. The reactants are heated by the feeding system and pyrolysis furnace 1 before entering the quench cooler 2. Liquid products are collected from the product separation outlet of the gas-liquid separator 3, and samples are taken from the vent outlet to analyze the hydrocarbon composition, carbon monoxide, and carbon dioxide content of the pyrolysis gas after the reaction. Feeding is stopped when the thermal pyrolysis furnace 1 tube wall temperature (TMT) reaches the upper limit of 1100℃, and the operating time is recorded as an evaluation criterion for the length of the operating cycle.

[0050] In this embodiment of the invention, the coking inhibitor can be injected into steam or water through injection port one, or into the pyrolysis feedstock through injection port two. In contrast, the inorganic salt inhibitor in the comparative example can only be injected into steam or water through injection port one.

[0051] After injecting coking inhibitor, the temperature of pyrolysis furnace 1 is raised to above 800℃, air is introduced and maintained at 800℃, and the oxygen content of the coking gas at the outlet of quench cooler 2 is detected by the coking controller. Initially, the carbon monoxide and carbon dioxide contents are high, reaching the upper limit of 25% for the carbon monoxide and carbon dioxide gas analyzers. As the coking process continues, the carbon monoxide and carbon dioxide contents gradually decrease, while the oxygen content continues to rise until it reaches a level comparable to that of air. At this point, the coking operation is complete, and the total coking time is recorded. During the coking operation, the temperature indication of thermocouple 101 in the furnace tube of pyrolysis furnace 1 must be continuously monitored, and it must not exceed the upper temperature resistance limit of 1100℃ for the 2520 material. Generally, it is set below 1000℃. 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 the present 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 make the fatty acid reaction complete, the amount of potassium hydroxide is a little more, so the molar ratio of potassium hydroxide to the mixed fatty acid in the present embodiment is 1.05:1, and finally the coking inhibitor is prepared.

[0054] The thermal cracking process shown in the foregoing Figure 1 The coking inhibitor is continuously injected in small doses at the beginning of the cracking reaction of the hydrocarbon raw material into the cracking furnace 1 using a continuous injection method, and the injection amount is 80 ppm of the input amount of the cracking hydrocarbon raw material. A feeding operation cycle is completed: the cracking reaction temperature is 800°C, the cracking raw material is diesel oil, the feeding amount is 5 kg / h, the dilution ratio is 0.8, and the residence time is 0.40 s; 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 80 h; the carbon monoxide and carbon dioxide contents are 0.09% and 0.07%, respectively; and the coking time is 0.4 h.

[0055] Example 2

[0056] The difference from Example 1 is that in the present embodiment, the coking inhibitor is injected in the middle of the cracking reaction of the hydrocarbon raw material into the cracking furnace 1 for 20 h, and the effect of intermittent and continuous injection on the operation cycle is investigated.

[0057] A feeding operation cycle is completed: the cracking reaction temperature is 800°C, the cracking raw material is diesel oil, the feeding amount is 5 kg / h, the dilution ratio is 0.8, and the residence time is 0.40 s; 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 75 h; the carbon monoxide and carbon dioxide contents before injection are 0.05% and 0.03%, respectively, and after injection, they are 0.09% and 0.07%, respectively; and the coking time is 0.4 h.

[0058] Comparative Example 1

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

[0060] A feeding operation cycle is completed: the cracking reaction temperature is 800°C, the cracking raw material is diesel oil, the feeding amount is 5 kg / h, the dilution ratio is 0.8, and the residence time is 0.40 s; 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 40 h, the carbon monoxide and carbon dioxide contents are 0.05% and 0.03%, respectively; and the coking time is 1 h.

[0061] From Examples 1-2 and Comparative Example 1, when the coking inhibitor of the present application is injected into the cracking furnace 1 using the continuous injection method, the operation cycle is prolonged by 1 times compared to Comparative Example 1 without the injection of the coking inhibitor, and the coking time is reduced by 60%, indicating that the coking inhibitor of the present application has a significant coking inhibition effect when used using the continuous injection method. When the coking inhibitor of the present application is injected into the cracking furnace 1 using the intermittent injection method, the operation cycle is prolonged by 0.88 times compared to Comparative Example 1 without the injection of the coking inhibitor, and the coking time is reduced by 60%. Thus, from Examples 1-2 and Comparative Example 1, it can be seen that the coking inhibitor of the present application has a significant coking inhibition effect in the early and middle-late stages of operation.

[0062] Comparative Example 2

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

[0064] Using the continuous injection method, the potassium carbonate is continuously injected in small doses from the start 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 amount, and one feedstock operation cycle is completed: the cracking reaction temperature is 800℃, the cracking feedstock is diesel, the feedstock amount is 5 kg / h, the dilution ratio is 0.8, and the residence time is 0.40 s. During the experiment, the carbon monoxide and carbon dioxide contents are 0.12% and 0.08%, respectively, which is significantly higher than that of Comparative Example 1, indicating that the inorganic potassium salt inhibitor also plays a role in eliminating coke, but because the inlet pressure of the cracking furnace 1 rapidly rises, it is judged that the furnace tube is blocked, and although the TMT of the cracking furnace 1 does not reach the upper limit of 1100℃, the feedstock is also stopped, and the operation time is recorded as 30 h, and the coking time is 0.6 h. The furnace tube of the cracking furnace 1 is disassembled, and the furnace tube is dredged using pure water, and the composition of the aqueous solution is collected and analyzed, and the result shows that it is potassium carbonate, indicating that the inorganic potassium salt inhibitor lacks oil solubility, and is prone to uneven distribution, leading to 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 (i.e., an organic sulfur phosphorus inhibitor).

[0067] Using the continuous injection method, the dimethyl disulfide is continuously injected in small doses from the start 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 amount, and one feedstock operation cycle is completed: the cracking reaction temperature is 800℃, the cracking feedstock is diesel, the feedstock amount is 5 kg / h, the dilution ratio is 0.8, and the residence time is 0.40 s; when the TMT of the cracking furnace 1 reaches the upper limit of 1100℃, the feedstock is stopped, and the operation time is recorded as 60 h, and the carbon monoxide and carbon dioxide contents are 0.05% and 0.03%, respectively, and the coking time is 0.7 h.

[0068] Comparative Example 4

[0069] The difference between Comparative Example 3 and Comparative Example 4 is that the latter uses intermittent injection method, and dimethyl disulfide is injected at the middle stage of 20h of the pyrolysis reaction of the hydrocarbon raw material in the cracking furnace 1, and the injection amount is 80ppm of the input amount of the pyrolysis hydrocarbon raw material.

[0070] A feeding operation cycle is completed: the pyrolysis reaction temperature is 800℃, the pyrolysis 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 upper limit of the TMT of the cracking furnace 1 reaches 1100℃, the feeding is stopped, the operation time is recorded as 45h, the carbon monoxide and carbon dioxide contents are 0.05% and 0.03% respectively, and the coking time is 0.9h.

[0071] As can be seen from Comparative Examples 1, 3 and 4, the organic sulfur and phosphorus type 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 between Example 1 and Example 3 is that in the preparation of the coking inhibitor, only palmitic acid is used in Example 3, and the theoretical molar ratio of potassium hydroxide to palmitic acid is 1:1. However, considering the reversibility of the esterification reaction, in order to make the fatty acid reaction complete, the amount of potassium hydroxide is slightly more, so the molar ratio of potassium hydroxide to palmitic acid in this example is 1.05:1, and the coking inhibitor is finally prepared.

[0074] A continuous injection method is used, and potassium palmitate is continuously injected in small doses from the beginning of the pyrolysis reaction of the hydrocarbon raw material in the cracking furnace 1, and the injection amount is 80ppm of the input amount of the pyrolysis hydrocarbon raw material. A feeding operation cycle is completed: the pyrolysis reaction temperature is 800℃, the pyrolysis 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 upper limit of the TMT of the cracking furnace 1 reaches 1100℃, the feeding is stopped, the operation time is recorded as 50h, which is 0.25 times longer than that of Comparative Example 1; the carbon monoxide and carbon dioxide contents before injection are 0.05% and 0.03% respectively, and those after injection are 0.07% and 0.04% respectively; the coking time is 0.8h, which is 20% less than that of Comparative Example 1.

[0075] As can be seen from Example 1, Comparative Example 1 and Example 3, the coking inhibitor prepared by using only palmitic acid and potassium hydroxide has a slight coking inhibition effect, but the coking inhibition effect is obviously poorer than that of the coking inhibitor prepared by using two kinds of fatty acids simultaneously. This is because the potassium palmitate prepared in Example 3 is directed against light oil coking products, and the mixed potassium fatty acid prepared in Example 1 is directed against heavy oil coking products. The coking products of light oil are relatively lighter and have higher saturation than those of heavy oil, and the carbon number of potassium palmitate is comparable to the average carbon number distribution of light oil, so the binding force of potassium palmitate with the coking products of light oil is stronger, and the coking removal effect is better, but the coking removal effect on the coking products of heavy oil is relatively poor.

[0076] Example 4

[0077] The difference from Example 1 is that in the preparation of the coking inhibitor, only oleic acid is used as the fatty acid, and the theoretical molar ratio of potassium hydroxide to oleic acid is 1:1. However, considering the reversibility of the esterification reaction, in order to make the reaction of oleic acid complete, the amount of potassium hydroxide is a little more, so the molar ratio of potassium hydroxide to oleic acid in this example is 1.05:1, and the coking inhibitor is finally prepared.

[0078] Using continuous injection method, potassium oleate is continuously injected in a small dose into the pyrolysis furnace 1 at the beginning of the pyrolysis reaction of the hydrocarbon raw material, and the injection amount is 80 ppm of the input amount of the pyrolysis hydrocarbon raw material. A feeding operation cycle is completed: the pyrolysis reaction temperature is 800℃, the pyrolysis raw material is diesel oil, the feeding amount is 5kg / h, the dilution ratio is 0.8, and the residence time is 0.40s; when the TMT of the pyrolysis furnace 1 reaches the upper limit of 1100℃, the feeding is stopped, and the running time is recorded as 65h, which is 0.52 times longer than that of Comparative Example 1; the contents of carbon monoxide and carbon dioxide before injection are 0.05% and 0.03% respectively, and those after injection are 0.07% and 0.04% respectively; the coking time is 0.61h, which is 40% less than that of Comparative Example 1.

[0079] As can be seen from Example 1, Comparative Example 1 and Example 4, the coking inhibitor prepared by using only potassium oleate also has a certain coking inhibition effect, but the coking inhibition effect is poorer than that of the coking inhibitor prepared by using two kinds of fatty acids simultaneously.

[0080] Example 5

[0081] The difference from Example 1 is that in the preparation of the coking inhibitor, only stearic acid is used as the fatty acid, and the theoretical molar ratio of potassium hydroxide to stearic acid is 1:1. However, considering the reversibility of the esterification reaction, in order to make the reaction of stearic acid complete, the amount of potassium hydroxide is a little more, so the molar ratio of potassium hydroxide to stearic acid in this example is 1.05:1, and the coking inhibitor is finally prepared.

[0082] The continuous injection method is used to continuously inject the potassium stearate in small doses at the beginning of the cracking reaction of the hydrocarbon raw material in cracking furnace 1, and the injection amount is 80 ppm of the input amount of the cracking hydrocarbon raw material. One feeding operation cycle is completed: the cracking reaction temperature is 800°C, the cracking raw material is diesel oil, the feeding amount is 5 kg / h, the dilution ratio is 0.8, and the residence time is 0.40 s. When the TMT of cracking furnace 1 reaches the upper limit of 1100°C, the feeding is stopped, and the operation time is recorded as 70 h, which is 0.75 times longer than that of Comparative Example 1. The carbon monoxide and carbon dioxide contents before and after injection are 0.05% and 0.03%, respectively, and 0.07% and 0.04%, respectively. The coking time is 0.60 h, which is 40% less than that of Comparative Example 1.

[0083] As can be seen from Example 1, Comparative Example 1 and Example 5, the use of only potassium stearate coking inhibitor also has a certain coking inhibition effect, but the coking inhibition effect is poorer than that of the use of two kinds of fatty acid coking inhibitors at the same time.

[0084] Example 6

[0085] The preparation method of the coking inhibitor of the present example is as follows: the mixed fatty acid composed of oleic acid and stearic acid in a molar ratio of 1:1.5 is reacted with potassium carbonate. The theoretical molar ratio of potassium carbonate to mixed fatty acid is 0.5:1, but considering the reversibility of esterification reaction, in order to make the fatty acid reaction complete, the amount of potassium carbonate is a little more, so the molar ratio of potassium carbonate to mixed fatty acid in the present example is 0.52:1, and finally the coking inhibitor is prepared.

[0086] The pyrolysis process as shown in the foregoing Figure 1 The continuous injection method is used to continuously inject the coking inhibitor in small doses at the beginning of the cracking reaction of the hydrocarbon raw material in cracking furnace 1, and the injection amount is 80 ppm of the input amount of the cracking hydrocarbon raw material. One feeding operation cycle is completed: the cracking reaction temperature is 800°C, the cracking raw material is diesel oil, the feeding amount is 5 kg / h, the dilution ratio is 0.8, and the residence time is 0.40 s. When the TMT of cracking furnace 1 reaches the upper limit of 1100°C, the feeding is stopped, and the operation time is recorded as 80 h. The carbon monoxide and carbon dioxide contents are 0.09% and 0.07%, respectively. The coking time is 0.4 h.

[0087] Example 7

[0088] The difference from Example 4 is that the intermittent injection method is used to inject the coking inhibitor in the middle of the cracking reaction of the hydrocarbon raw material in cracking furnace 1.

[0089] A feed running cycle was completed: the cracking reaction temperature was 800°C, the cracking raw material was diesel, the feed amount was 5 kg / h, the dilution ratio was 0.8, and the residence time was 0.40 s; when the upper limit of 1100°C of the TMT of the cracking furnace 1 was reached, the feeding was stopped, and the running time was recorded as 75 h; the carbon monoxide and carbon dioxide contents were 0.05% and 0.03% respectively before the injection, and 0.09% and 0.07% respectively after the injection; the coking time was 0.4 h.

[0090] Example 8

[0091] The preparation method of the coking inhibitor of the present example is as follows: the 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 mixed fatty acid is 1:1, but considering the reversibility of esterification reaction, in order to make the fatty acid react completely, the amount of potassium bicarbonate is a little more, so the molar ratio of potassium bicarbonate to mixed fatty acid in the present example is 1.12:1, and finally the coking inhibitor is prepared.

[0092] The thermal cracking process as shown in the foregoing Figure 1 The continuous injection method was adopted, and the coking inhibitor was continuously injected in a small dose at the beginning of the cracking reaction of the hydrocarbon raw material in the cracking furnace 1, and the injection amount was 80 ppm of the input amount of the cracking hydrocarbon raw material. A feed running cycle was completed: the cracking reaction temperature was 800°C, the cracking raw material was diesel, the feed amount was 5 kg / h, the dilution ratio was 0.8, and the residence time was 0.40 s; when the upper limit of 1100°C of the TMT of the cracking furnace 1 was reached, the feeding was stopped, and the running time was recorded as 80 h; the carbon monoxide and carbon dioxide contents were 0.09% and 0.07% respectively; and the coking time was 0.4 h.

[0093] Example 9

[0094] The difference from Example 8 is that: the intermittent injection method was adopted in the present example, and the coking inhibitor was injected at the middle stage of 20 h of the cracking reaction of the hydrocarbon raw material in the cracking furnace 1.

[0095] A feed running cycle was completed: the cracking reaction temperature was 800°C, the cracking raw material was diesel, the feed amount was 5 kg / h, the dilution ratio was 0.8, and the residence time was 0.40 s; when the upper limit of 1100°C of the TMT of the cracking furnace 1 was reached, the feeding was stopped, and the running time was recorded as 75 h; the carbon monoxide and carbon dioxide contents were 0.05% and 0.03% respectively before the injection, and 0.08% and 0.06% respectively after the injection; and the coking time was 0.45 h.

[0096] Comparative Example 5

[0097] The coking inhibitor of Comparative Example 5 was prepared as follows: a mixed fatty acid composed of palm oil and stearic acid in a molar ratio of 1:1 was reacted with potassium hydroxide, wherein the theoretical molar ratio of potassium hydroxide to the mixed fatty acid was 1:1, but considering the reversibility of the esterification reaction, the amount of potassium hydroxide was a little more in order to make the fatty acid react completely, thus the molar ratio of potassium hydroxide to the mixed fatty acid in this example was 1.05:1, and finally the coking inhibitor was prepared.

[0098] The thermal cracking process shown in the foregoing Figure 1 was adopted, and the coking inhibitor was continuously injected in small doses at the beginning of the cracking reaction of the hydrocarbon raw material in the cracking furnace 1. The injection amount was 80 ppm of the input amount of the cracking hydrocarbon raw material. One feeding operation cycle was completed: the cracking reaction temperature was 800°C, the cracking raw material 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 contents of carbon monoxide and carbon dioxide were 0.07% and 0.05%, respectively. The coking time was 0.7 h.

[0099] Comparative Example 6

[0100] The difference from Comparative Example 5 is that the coking inhibitor was injected in the middle of the cracking reaction of the hydrocarbon raw material in the cracking furnace 1 in this example.

[0101] One feeding operation cycle was completed: the cracking reaction temperature was 800°C, the cracking raw material 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 65 h. The contents of carbon monoxide and carbon dioxide were 0.05% and 0.03% before injection, and 0.07% and 0.05% after injection, respectively. The coking time was 0.55 h.

[0102] As can be seen from Examples 1-2 and Comparative Examples 5-6, the coking inhibitor of Examples 1-2 prepared from the mixed fatty acid salt of oleic acid and stearic acid has a longer operation time than the coking inhibitor of Comparative Example 5 prepared from the mixed fatty acid salt of palm oil and stearic acid, and thus it can be known that the coking inhibitor prepared from the mixed fatty acid salt of oleic acid and stearic acid has a better use effect.

[0103] Experimental Example 1

[0104] No inhibitor was added, and the thermal cracking process shown in the foregoing Figure 1 was adopted. The cracking reaction temperature was 800°C, the cracking raw material 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 operation time of the cracking furnace was 20 h, the cracking products of the cracking furnace were collected, and the yield of the cracking products was analyzed by chromatography. The results are shown in Table 1.

[0105] Experimental Example 2

[0106] Using the mixed fatty acid salt inhibitor of the foregoing Experimental Example 1, using the thermal cracking process as shown in Figure 1 Figure 1, using a continuous injection method, the coking inhibitor was continuously injected in small doses at the start of the cracking reaction in the cracking furnace 1, the injection amount was 80 ppm of the cracking hydrocarbon feedstock input amount, the cracking reaction temperature was 800°C, the cracking feedstock was diesel, the feedstock amount was 5 kg / h, the dilution ratio was 0.8, and the residence time was 0.40 s; when the cracking furnace operation time was 20 h, the cracking products of the cracking furnace were collected, and the cracking product yields were analyzed using chromatography, the results are shown in Table 1.

[0107] Table 1 Cracking product yields of Experimental Example 1 and Experimental Example 2

[0108]

[0109] As can be seen from Table 1, under the same feedstock and process conditions, the cracking yields of Experimental Example 1 and Experimental Example 2 are very close, the main technical and economic indicators such as ethylene, propylene and triene yields of Experimental Example 2 are slightly higher than those of Experimental Example 1, which is because the inhibitor slows down the coking side reactions, which is beneficial to the generation of target products, thus it can be proved that the coking inhibitor of the present application will not have a negative impact on the technical and economic indicators of the device.

[0110] Although the present application has been described in detail through reference to preferred embodiments, it is to be understood that the present application is not limited to the disclosed embodiments. Various modifications and changes can be made to the present application without departing from the spirit and scope of the present application. Any skilled person in the art can easily make changes or substitutions within the technical scope disclosed in the present application, and these changes or substitutions should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. Use of a salt of a fatty acid as a coking inhibitor, characterized in that, The preparation method of the fatty acid salt coking inhibitor is that a fatty acid is reacted with a potassium compound to obtain the coking inhibitor; wherein the potassium compound is potassium hydroxide, potassium carbonate or potassium bicarbonate; the fatty acid is a mixture of oleic acid and stearic acid; the molar ratio of the oleic acid to the stearic acid in the fatty acid is 1:(0.5-1.5); and the coking inhibitor is used for slowing down coking of a heavy oil cracking furnace tube.

2. The use of a fatty acid salt coking inhibitor according to claim 1, wherein The molar ratio of the fatty acid to the potassium element is 1:(1.0-1.1).

3. The use of a fatty acid salt coking inhibitor according to claim 1, wherein the fatty acid salt is a salt of a fatty acid having 8 to 22 carbon atoms. The coking inhibitor is injected into cracking raw materials and enters the heavy oil cracking furnace together with the cracking raw materials; or the coking inhibitor is injected into dilution steam and enters the heavy oil cracking furnace together with the dilution steam.

4. The use of a fatty acid salt coking inhibitor according to Claim 1, wherein the coking inhibitor is a salt of a fatty acid having 8 to 22 carbon atoms. The injection amount of the coking inhibitor is 50-100 ppm of the input amount of the cracking raw materials.

5. The use of a fatty acid salt coking inhibitor according to Claim 1, wherein the coking inhibitor is a salt of a fatty acid having 8 to 22 carbon atoms. The coking inhibitor is injected by using a continuous injection method or an intermittent injection method.

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