EP3322773A1

EP3322773A1 - A composition, method and applications thereof

Info

Publication number: EP3322773A1
Application number: EP16745176.4A
Authority: EP
Inventors: Padmavathi GARIMELLA; Sumeet Kumar SHARMA; Nagesh Sharma; Raksh Vir Jasra; Laxmilal Jain
Original assignee: Reliance Industries Ltd
Current assignee: Reliance Industries Ltd
Priority date: 2015-07-14
Filing date: 2016-07-13
Publication date: 2018-05-23
Anticipated expiration: 2036-07-13
Also published as: EP3322773B1; KR20180042849A; US20180208856A1; WO2017009785A1

Abstract

The instant disclosure relates to a composition comprising potassium carbonate and calcium acetate, optionally along with sulfur containing compound. The composition of the present disclosure reduces coke formation during hydrocarbon cracking, particularly reduces surface coke and spalled coke during hydrocarbon cracking when compared to hydrocarbon cracking without the said composition. The disclosure further relates to a method for reducing formation and/or deposition of coke during pyrolysis or cracking of hydrocarbons.

Description

A COMPOSITION, METHOD AND APPLICATIONS THEREOF

TECHNICAL FIELD

[1] The present disclosure relates to the field of organic chemistry, particularly steam cracking of hydrocarbons. The disclosure relates to a composition comprising inorganic salts including but not limiting to Group 1A and Group 2A metallic salts, respectively. The composition of the present disclosure is employed for reducing formation and/or deposition of coke in the systems employed for high temperature processing or cracking of hydrocarbons. The present disclosure also relates to addition of a composition comprising inorganic salts including but not limiting to Group 1A and Group 2 A metallic salts into the system employed for cracking of hydrocarbons. The present disclosure thus provides a composition comprising metallic salts such as potassium carbonate and calcium acetate, and a method of employing the same to reduce coke formation and/or deposition during cracking of hydrocarbons. The disclosure also exemplifies a system wherein said method and composition is employed for said reduction of coke.

BACKGROUND

[2] Steam cracking of hydrocarbons to olefins such as ethylene and propylene is an important process in petrochemical industry. Hydrocarbons such as ethane, propane, butane, their mixtures and naphtha are cracked to olefins in tubular reactors in the presence of steam at higher temperatures in the range from 800-855°C.

[3] The inherent problem associated with the material of construction (MOC) of inner surface of reactors/cracker coil units is their tendency to promote the coke formation as the side reaction from thermal cracking leads to undesirable product. Coke is deposited as a layer on the inner walls of the reactor coils and in transfer line exchangers (TLEs) which are used to recover heat from product stream. The amount of coke deposited on the coil surface depends on feed stock composition, severity of operation such as operating temperatures and steam dilution ratio, coil design and metallurgy of the metals used in reactor unit construction. The accumulation of coke reduces the coil diameter and thereby increases the pressure drop, and reduces the amount of heat transfer and hence, external tube metal temperature has to be increased with time on stream.

[4] Coke formation is linked to or is a result of complex mechanisms involving catalytic, radical and condensation reactions. Catalytic mechanism involves metallic species such as iron (Fe), nickel (Ni) and chromium (Cr) which have potential catalytic activity and are used for the inner surface of reactor/cracking coil unit. Filamentous coke is formed with metallic agglomerates at the propagating tips of the unit. These coke filaments are excellent collection sites for cokes formed by various mechanisms including free-radical mechanism and condensation mechanism. Free-radical mechanism involves reactions of micro species, mainly gaseous free radicals, with the macro radicals present at the coke surface, whereas condensation mechanism is a non-catalytic mechanism and occurs at the metallic surface or the coke surface. Heavy poly nuclear compounds present in tar and soot condense at the reactor inner wall and gas interface, where they dehydrogenate and contribute to the coke deposition on the inner walls of the reactor unit.

[5] A periodic shut down of the unit is required to burn off the coke by decoking using steam and air at temperatures of around 870°C. Such decoking is required once in 30-90 days depending on the operation mode and feed composition. As a result during the decoking process, the production of ethylene and other industrial products is stopped for considerable time and also, frequent decoking deteriorates coil metal of the reactor. The major challenge experienced in steam cracking is reduction of coke deposition in the radiant section and transfer line exchangers (TLE). Efforts are thus required to eliminate or at least reduce coke formation and increase run length between two decokings.

[6] Several methods have been disclosed previously to overcome the deleterious effects of coke build up on reactor surfaces which include 1. metallurgical modification, 2. surface pre-treatment, 3. increased steam dilution ratio, 4. improved control of the operating conditions, and 5. improved feed stock quality.

[7] Despite the efforts employed in the previously, there is still a need for a commercially feasible and inexpensive composition and method to reduce coke deposition on the reactor walls (surface coke) and spalled coke formation during pyrolysis of hydrocarbons to produce light olefins. However, the instant invention overcomes the above mentioned drawbacks through the aspects described herein below.

SUMMARY OF THE DISCLOSURE

[8] The present disclosure relates to a composition comprising alkali metal salt and alkaline metal salts, optionally along with sulfur containing compound, wherein the composition reduces coke formation during hydrocarbon cracking.

[9] The composition of the present disclosure further reduces coke formation by memory effect of the composition during hydrocarbon cracking, wherein the memory effect of the composition is retained for at least two cycles of the hydrocarbon cracking. [10] The present disclosure further relates to a method for reducing coke formation during hydrocarbon cracking, wherein the method comprises step of introducing a composition comprising potassium carbonate and calcium acetate, optionally along with sulfur containing compound into a reactor system and subjecting the reactor system to hydrocarbon cracking.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

[11] In order that the disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figure. The figure together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure where:

[12] Figure 1 relates to a schematic diagram of the experimental set up (pyrolysis system) for thermal cracking process of hydrocarbons and thereby converting it into olefins.

[13] Figure 2 relates to a bar chart showing the amount of surface coke formed during hydrocarbon cracking in absence (R-405 and R-408) and presence (R-412) of the composition of the present disclosure. The figure also establishes the sustainable effect of the elements of the composition after primary run, in the form of memory runs Ml and M2 (R-413 and R-414), respectively, demonstrating the memory effect of the composition.

[14] Figure 3 relates to a bar chart showing the comparison of percentage reduction in surface coke deposited during hydrocarbon cracking in absence (R-408) and presence (R- 412) of the composition of the present disclosure. The figure also establishes the sustainable effect of the elements of the composition after primary run, in the form of memory runs Ml and M2 (R-413 and R-414), respectively, demonstrating the memory effect of the composition.

[15] Figure 4 relates to a bar chart showing the amount of spalled coke formed during hydrocarbon cracking in absence (R-408) and presence (R-412) of the composition of the present disclosure. The figure also establishes the sustainable effect of the elements of the composition after primary run, in the form of memory runs Ml and M2 (R-413 and R-414), respectively, demonstrating the memory effect of the composition.

[16] Figure 5 relates to a bar chart depicting the percentage yield of the product yield obtained upon hydrocarbon cracking in in absence (R-408) and presence (R-412) of the composition of the present disclosure.

[17] Figure 6 relates to a bar chart depicting the amount of metal leaching recorded by inductively coupled plasma (ICP) analysis during hydrocarbon cracking in absence (R-408) and presence (R-412) of the composition of the present disclosure. The figure also establishes the sustainable effect of the elements of the composition after primary run, in the form of memory runs (R-413 and R-414), respectively, demonstrating the memory effect of the composition.

[18] Figure 7 relates to a bar chart showing the amount of metal content observed during hydrocarbon cracking in absence (R-408) and presence (R-412) of the composition of the present disclosure, demonstrating reduced metal leaching by the composition. . The figure also establishes the sustainable effect of the elements of the composition after primary run, in the form of memory runs Ml and Ml (R-413 and R-414), respectively, demonstrating the memory effect of the composition.

DETAILED DESCRIPTION

[19] To overcome the non-limiting drawbacks as stated in the background, the present disclosure provides a commercially feasible and inexpensive composition, a method and application of the composition for reducing formation of coke and/or reducing deposition of coke in reactor systems during cracking of hydrocarbon.

[20] The present disclosure relates to a composition comprising plurality of inorganic salts, optionally along with sulfur containing compound.

[21] In an embodiment, the inorganic salts in the composition are metallic salts having same or different cationic and anionic moieties, wherein the cationic moiety includes cations from groups of the Periodic Table including but not limiting to Group IA and Group IIA.

[22] In an exemplary embodiment, the cationic moiety of the composition comprises Group IA metals including but not limiting to lithium, sodium, potassium, rubidium, caesium and francium or Group IIA metals including but not limiting to beryllium, magnesium, calcium, strontium, barium, and radium, or any combination of metals thereof.

[23] In an exemplary embodiment, the anionic moiety of the composition comprises anions including but not limiting to acetate, fumerate, formate, malate, oxalate, carbonates, bicarbonates, sulphates, bisulphates, sulphities and bisulphities.

[24] In preferred embodiment, the group IA metal salt in the composition is potassium carbonate.

[25] In another preferred embodiment, the group 2A metal salt in the composition is calcium acetate.

[26] In an exemplary embodiment, the sulfur containing compound in the composition includes but not limited to dimethyl disulfide (DMDS), dimethyl sulfide (DMS), diethyl sulfide (DES), diethyl disulfide (DEDS), carbon disulfide, dimethyl sulfoxide and a mixture of disulphides. [27] In an embodiment, the concentration of the potassium carbonate and calcium acetate in the composition is ranging from about lppmw to lOOppmw, preferably about lppmw to lOppmw, more preferable about lpppmw to 4ppmw, wherein in the said concentration potassium carbonate is about 30wt% to 40 wt% and calcium acetate is about 60wt% to 70wt%.

[28] In a preferred embodiment, the concentration of the potassium carbonate and the calcium acetate in the composition is ranging from about lppmw to lOppmw, wherein in the said concentration, potassium carbonate is about 35wt% and calcium acetate is about 65%.

[29] In another preferred embodiment, the concentration of the potassium carbonate and calcium acetate in the composition is ranging from about lppmw to 4ppmw, wherein in the said concentration, potassium carbonate is about 35wt% and calcium acetate is about 65%.

[30] In an embodiment, the concentration of the sulfur containing compound in the hydrocarbon feed is ranging from about 50ppmw to 250 ppmw.

[31] In an alternate embodiment, sulfur is part of the cracking process and the sulfur containing compound is injected as liquid in to the cracking process, alongside the composition of the present disclosure. The sulfur containing compounds include but not limiting to dimethyl disulfide and other disulfides, injected directly into the cracker alongside the composition of the present disclosure.

[32] In an embodiment, the composition of the present disclosure is soluble in solvents including but not limiting to polar solvent and non-polar solvent.

[33] In an exemplary embodiment, the potassium carbonate and calcium acetate of the composition is soluble in water or polar solvents.

[34] The composition comprising potassium carbonate and calcium acetate, optionally along with sulfur containing compound, of the present disclosure reduces coke formation and/or reduces deposition of coke in a reactor system.

[35] In an exemplary embodiment, the composition of the present disclosure reduces coke formation in a reactor system by at least 40%.

[36] In another exemplary embodiment, the composition of the present disclosure reduces coke formation in a reactor system by at least 60%.

[37] In an embodiment, the composition of the present disclosure reduces coke formation in a reactor system during cracking process by at least 40% when compared to the process in absence of the said composition.

[38] In another embodiment, the composition of the present disclosure reduces formation of surface coke during cracking process by at least 60% when compared to the process in absence of the said composition.

[39] In another embodiment, the composition of the present disclosure reduces spalled coke in a reactor system during cracking process by at least 25% when compared to the process in absence of the said composition.

[40] In another embodiment, the composition of the present disclosure demonstrates memory effect, wherein such composition reduces the formation of surface coke by at least 50% and reduces spalled coke by at least 25%, in a reactor system during cracking process.

[41] Memory effect represents the composition of the present disclosure remaining after decoking cycle which would reduce coke formation in the subsequent cracking cycle. For instance, the composition of the present disclosure added during first cycle of cracking also reduces coke formation in the subsequent cycle, at least for 2 cycles, and there is no need of adding the said composition in the said subsequent cycles of cracking.

[42] In an embodiment, the memory effect of the composition is retained and is effective for at least 2 cycles of cracking process in the reactor system.

[43] In an additional embodiment, the composition of the present disclosure in the reactor system during cracking process reduces corrosion by at least 40% when compared to the process in absence of the said composition.

[44] In another additional embodiment, the composition of the present disclosure in the reactor system during the cracking process reduces metal leaching by at least 50%when compared to the process in absence of the said composition.

[45] In an embodiment, the composition of the present disclosure reduces coke formation within a reactor system, wherein such reactor system includes but is not limited to cracking reactor unit employed for cracking of hydrocarbons.

[46] The present disclosure further relates to a method for reducing coke formation and/or deposition of coke during hydrocarbon cracking, said method comprises the step of introducing a reactor system with the composition of the present disclosure.

[47] In an embodiment, the reactor system includes but is not limited to cracking reactor unit employed for cracking of hydrocarbons.

[48] In a preferred embodiment, the present disclosure relates to a method of employing the composition of the present disclosure for reducing formation of coke and/or deposition of coke within the reactor system, wherein such reactor system includes but is not limited to cracking reactor unit employed for cracking of hydrocarbons. The method comprises introducing the composition of the present disclosure to said reactor system, wherein the composition comprises potassium carbonate and calcium acetate, optionally along with sulfur containing compound.

[49] In a non-limiting embodiment, the method of reducing formation coke and/or deposition of coke within the reactor system during cracking of hydrocarbons, comprises steps of:

a) introducing the composition of the present disclosure into the reactor system along with water or hydrocarbon feed stock or both; and

b) subjecting the reactor system to high temperature and allowing cracking of the hydrocarbons introduced therein, in presence of the composition, during which the formation and/or deposition of coke within reactor system is found to be substantially reduced, when compared to cracking process without said composition.

[50] In a non-limiting embodiment, addition of the composition into the reactor system during cracking reduces the formation of surface coke, reduces the formation of spalled coke within the reactor unit, respectively and/or deposition of coke on the inner walls of the reactor unit, transfer lines and cracking tubes within the system employed for the cracking reaction, thereby increasing the run length and reducing the need for frequent decoking of the reactor.

[51] In a non-limiting embodiment, the method of the present disclosure employing the composition of the present disclosure results in reduction in coke formation and/or deposition of coke by at least 40% during cracking of hydrocarbon when compared to cracking of hydrocarbons without said composition.

[52] In a non-limiting embodiment, the method of the present disclosure employing the composition of the present disclosure results in reduction in coke formation and/or deposition of coke by at least 60% during cracking of hydrocarbon, when compared to cracking of hydrocarbons without said composition.

[53] In another non-limiting embodiment, the method of the present disclosure employing the composition of the present disclosure results in reduction of surface coke by at least 60% during cracking of hydrocarbon when compared to cracking of hydrocarbons without said composition.

[54] In another non-limiting embodiment, the method of the present disclosure employing the composition of the present disclosure results in reduction of spalled coke by at least 25% when during cracking of hydrocarbon compared to cracking of hydrocarbons without said composition.

[55] In another non-limiting embodiment, during the method of the present disclosure, the composition of the present disclosure demonstrates memory effect, wherein such method having the memory effect of the composition results in reduction of surface coke by at least 50% and results in reduction of spalled coke by at least 25% during hydrocarbon cracking when compared to the hydrocarbon cracking without the composition.

[56] In a non-limiting embodiment, in the method of the present disclosure, the composition of the present disclosure is introduced into the reactor system along with water employed for generation of the steam or along with the steam generated directly or along with the hydrocarbon or hydrocarbon feed stock, or any combination thereof.

[57] In a preferred embodiment, in the method of the present disclosure, the composition is injected into the reactor system along with the steam.

[58] In another preferred embodiment, in the method of the present disclosure, the composition is injected into the reactor system along with hydrocarbon or hydrocarbon feed stock.

[59] In a non-limiting embodiment, the hydrocarbon or the hydrocarbon feed that is loaded into the reactor system includes compounds such as but not limiting to naphtha. In a preferred embodiment, the naphtha that is used as the hydrocarbon feed includes but not limited to light naphtha and heavy naphtha, preferably light naphtha.

[60] In a non-limiting embodiment, the method of the present disclosure employing the composition of the present disclosure, for reducing formation of coke and/or reducing deposition of coke within reactor system, is applicable for any reactor or system conventionally known in the art for cracking of hydrocarbons. Such reactor or system may perform cracking of hydrocarbons by performing a series of steps which are well established and understood by a person skilled in the art. However, for reduction of coke formation and/or reduction of deposition of coke, the composition of the present disclosure must be integrated with steps for cracking of hydrocarbons.

[61] In an exemplary embodiment, the method of reducing formation of coke and/or deposition of coke during cracking of hydrocarbons involves the following acts:

[62] Initially, the furnace is turned on and the temperature is slowly increased from room temperature while nitrogen or air is fed in continuously at the rate of about 80 to 100 °C/h. After a desired temperature profile of about 450°C to 500°C cross over temperature and about 800°C to 830°C of coil outlet temperature is established in the reactor, water along with the composition of the present disclosure is introduced into the reactor unit. After about thirty minutes, nitrogen or air that is supplied is discontinued and hydrocarbon feed (naphtha) is fed into the reactor unit. The flow rates of the naphtha and the water are set in such a way that the desired dilution ratio of about 0.3 to 0.5 is maintained throughout the process. The temperature of the furnace is lowered to about 20°C, as soon as naphtha is introduced into the reactor due to the endothermic reactions that are occurring in the reactor unit. Thereafter, the temperature is increased slowly to a desired temperature profile of about 450°C to 500°C cross over temperature and coil outlet temperature of about 810°C to 850°C. The product gases that are formed as a result of the reaction are analyzed by using two gas chromatographs. The product gases includes but not limiting to hydrogen, methane, ethane, ethylene, propane, propylene, butane, butenes, 1,2-butadiene, 1,3-butadiene and pentanes. Typical material balance is performed to check the mass conservation, for a predetermined time period by taking the weights of naphtha and water, weighing the amount of liquid product collected, weighing the total amount of gas through gas flow meter during the period and analyzing the product gas so formed. During the reaction (cracking run), the product gas is analyzed once in about 12 hours. After completion of a run, the reactor is cooled down to room temperature of about 20°C to 40°C and weight of thermowell of the reactor is measured to estimate the amount of surface coke reduced during the reaction, wherein the formation of coke is reduced by at least 60%. Similarly, spalled coke is collected at the end of the run after cooling to room temperature about 20°C to 40°C and opening of the furnace, to estimate the amount of spalled coke reduced during the reaction, wherein the spalled coke is reduced by at least 25%, post which the thermos well is fixed into the reactor followed by which leak test is performed.

[63] In another exemplary embodiment, the method of reducing formation of coke and/or deposition of coke during cracking of hydrocarbons involves the following acts: Initially, the furnace is turned on and the temperature is slowly increased while nitrogen or air is fed in continuously. After a desired temperature profile of about 450°C to 500°C cross over temperature and about 800°C to 830°C of coil outlet temperature is established in the reactor, water is introduced into the reactor unit. After about thirty minutes, nitrogen or air that is supplied is discontinued and hydrocarbon feed (naphtha) along with the composition of the present disclosure is fed into the reactor unit. The flow rates of the naphtha along with the composition of the present disclosure and the water are set in such a way that the desired dilution ratio of about 0.3 to 0.5 is maintained throughout the process. The temperature of the furnace is lowered to about 20°C, as soon as naphtha along with the composition of the present disclosure is introduced into the reactor due to the endothermic reactions that are occurring in the reactor unit. Thereafter, the temperature is increased slowly to a desired temperature profile of about 450°C to 500°C cross over temperature and coil outlet temperature of about 810°C to 850°C. The product gases that are formed as a result of the reaction are analyzed by using two gas chromatographs. Typical material balance is performed to check the mass conservation, for a predetermined time period by taking the weights of naphtha and water, weighing the amount of liquid product collected, weighing the total amount of gas through gas flow meter during the period and analyzing the product gas so formed. During the reaction (cracking run), the product gas is analyzed once in about 12 hours. After completion of a run, the reactor is cooled down to room temperature of about temperature of about 20°C to 40°C and weight of thermowell of the reactor is measured to estimate the amount of surface coke reduced during the reaction, wherein the formation of coke is reduced by at least 60%. Similarly, spalled coke is collected at the end of the run after cooling to room temperature about 20°C to 40°C and opening of the furnace, to estimate the amount of spalled coke reduced during the reaction, wherein the spalled coke is reduced by at least 25%, post which the thermowell is fixed into the reactor followed by which leak test is performed. In a non-limiting embodiment, the method of the present disclosure employing the composition of the present disclosure involves cracking of hydrocarbons at high temperature ranging from about 800°C to 850°C, preferably at about 825°C.

[64] In a non-limiting embodiment, in the method of the present disclosure, the composition of the present disclosure employed for reducing formation of spalled coke and reducing formation of surface coke within the reactor system and/or deposition of coke on the inner walls of the reactor system, comprises potassium carbonate and calcium acetate at concentration ranging from about lppmw to lOOppmw, wherein in the said concentration, potassium carbonate is about 30wt% to 40wt% and calcium acetate is about 60wt% to 70wt% and sulfur containing compound is at a concentration ranging from about 50ppmw to 250 ppmw, with respect to hydrocarbon.

[65] In a preferred embodiment, in the method of the present disclosure, the composition of the present disclosure employed for reducing formation of spalled coke and reducing formation of surface coke within the reactor system and/or deposition of coke on the inner walls of the reactor system, comprises potassium carbonate and calcium acetate at concentration ranging from about lppmw to lOppmw, wherein in the said concentration, potassium carbonate is about 35wt% and calcium acetate is about 65wt% and sulfur containing compound is at a concentration ranging from about 50ppmwto 250 ppmw, with respect to hydrocarbon.

[66] In another preferred embodiment, in the method of the present disclosure, the composition of the present disclosure employed for reducing formation of spalled coke and reducing formation of surface coke within the reactor system and/or deposition of coke on the inner walls of the reactor system, comprises potassium carbonate and calcium acetate at concentration ranging from about lppmw to lOppmw, wherein in the said concentration, potassium carbonate is about 35wt% and calcium acetate is about 65wt% and sulfur containing compound is at a concentration ranging from about 50ppmwto 250 ppmw, with respect to hydrocarbon.

[67] In a non-limiting embodiment, the metallic salts of the composition decomposes into oxides during the process of hydrocarbon cracking at the pyrolysis temperature of about 810°C to 855°C, which interacts with the coke formed or deposited within the reactor system and catalyses the coke gasification reaction, thereby reducing the net coke formation.

[68] In an exemplary embodiment, the potassium carbonate of the composition decomposes into potassium oxide during the process of hydrocarbon cracking at the pyrolysis temperature of about 810°C to 855°C, said potassium oxide interacts with the coke formed or deposited within the reactor system and catalyses the coke gasification reaction, thereby reducing the net coke formation.

[69] In another exemplary embodiment, the calcium acetate of the composition decomposes into calcium oxide during the process of hydrocarbon cracking at the pyrolysis temperature of about 810°C to 855°C, said calcium oxide interacts with the coke formed or deposited within the reactor system and catalyses the coke gasification reaction, thereby reducing the net coke formation.

[70] In another exemplary embodiment, the sulfur containing compound in the composition controls the excess carbon oxides formed during coke gasification. Thereby acting synergistically along with potassium carbonate and calcium acetate of the composition in reducing coke formation.

[71] In an embodiment, the sulfur content in the feed and/or in the composition that is used in a reaction should be sufficient to control the excess carbon oxides formed during coke gasification. In a non-limiting embodiment, the relative amount of composition is adjusted to maintain coke reduction and thereby reduce corrosion level. The concentration of each element in the composition is less than 1 ppmw to meet the specifications with respect to fouling and corrosion. For instance, ppmw of the composition consists of 65%calcium acetate and 35% of potassium carbonate i.e about 2.6 ppmw of calcium acetate and about 1.4 ppmw of potassium carbonate. The Calcium element concentration in Calcium acetate is about 25% which amounts to about 0.65 ppmw calcium and Potassium element concentration in potassium carbonate is about 56.58% which amounts to about 0.792 ppmw,. Therefore, the concentration of each of the element in the composition is significantly lower than the 1 ppmw limit to minimize the corrosion.

[72] In an exemplary embodiment, the method of reducing formation of coke and/or deposition of coke during the process for cracking of hydrocarbons as described above is carried out in a cracking system (reactor system) such as those provided by figure 1 herein. Figure 1 is a representative flow diagram of the pyrolysis system [100] employed for cracking of hydrocarbon feed (naphtha) which comprises naphtha vaporizer, water vaporizer, mixer, cracker furnace, naphtha tank, naphtha feed pump, water feed tank, water feed pump, transfer line heat exchangers (TLEs) 1 and 2 and gas-liquid separator, wherein all the furnaces employed in the system are electrically heated.

[73] In an exemplary embodiment, within the pyrolysis system exemplified in the present disclosure, naphtha (feed) (10) and water comprising the composition of the present disclosure (12) are stored in two SS tanks at atmospheric pressure. The tanks are provided with level gauges using which the flow rate of the naphtha and water comprising the composition of the present disclosure can be checked regularly. Two tanks are placed on two separate electronic weighing balances (14 and 16) to measure the amount of feed and water comprising the composition consumed in a particular run. In another embodiment, there are two metering pumps (18 & 20) of predetermined capacity each for the pumping of the hydrocarbon naphtha feeds and water comprising the composition, respectively. The suction is taken from the storage tanks through spiral tube to minimize pulsations in the feed flow. The system further comprises two vaporizers namely naphtha vaporizer (22) and water vaporizer (24) made of SS316. Heat is supplied electrically thereby heating the furnaces to vaporize the naphtha and the water, optionally along with the composition of the present disclosure that is pumped from the metering pumps. During a typical run, the outlets of vaporizers are sent to a mixer (26) where the temperature is raised to a range of about 400°C to 600°C, preferably around 480°C which is referred to as cross over temperature. The reactor coil (36) is a straight tube made of 11 mm inner diameter, 3.01 mm thickness comprising incoloy 800 tube of 355 mm long with a provision to measure temperature profile. Thermowell is 260 mm long and 6.35 mm outer diameter made of SS-316 and fixed from the bottom of the rector tube which also serves as a concentric insert. The coil is fixed in an electrically heated furnace (38) of 360 mm long and 255 mm wide in a single zone. Temperature can be independently controlled to a desired temperature profile of about 450°C to 855°C in the coil at inlet to outlet . Thermocouple is located inside the reactor coil to measure process gas temperature profile by moving the location. The external wall temperature of furnace is measured at center location. The gases that exit from the furnace are quenched to around 600 °C. The naphtha feed flow rate can be varied up to 100 g/h. The gases are further cooled in two transfer line heat exchangers (TLEs 44 & 46) that are connected in series, to condense the steam, optionally comprising the composition of the present disclosure and heaviers in the cracked product mixture. The condensed water and liquid is collected from the gas liquid separator (48) and weighed for mass balance calculations. Non condensed gases are further cooled and measured by a wet gas meter (50). The gaseous mixture is sent for analysis by CO/C02 analyser (52), two Gas Chromatographies (54 & 56) and the output of the GCs goes to Personal Computer for area integration and processing.

[74] In a further embodiment, the cracked gas sample that is liberated after the process is simultaneously analysed by two gas chromatographic (GC) systems. Hydrogen and methane are detected by a thermal conductivity detector (TCD) in the first GC system (HP 3362), whereas all the hydrocarbons present in the gaseous mixture are analysed by second GC (HP 5890) using flame ionisation detector. Peak identification and integration is performed by a commercial integration package and with these identifications, the product distribution in terms of weight percentage can be determined. Since the feed flow rate is known, yields of products %wt/wt of hydrocarbon feed and material balance can be calculated.

[75] Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based upon description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein. Further, the disclosure herein provides for examples illustrating the above described embodiments, and in order to illustrate the embodiments of the present disclosure certain aspects have been employed. The examples used herein for such illustration are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the following examples should not be construed as limiting the scope of the embodiments herein.

EXAMPLES

Example 1: Hydrocarbon cracking with water as steam and without employing the composition of the present disclosure (Control Run) [76] An experimental run (R-405) is carried out in a bench scale cracker having a cracker coil made of Incoloy 800HT and using naphtha as the feed. The coil outlet temperature is maintained at a temperature of about 825°C and steam dilution is at a ratio of about 0.32. The corresponding residence time is around 0.5 seconds. The feed olefin content is found to be about 1.94%. Blank run is carried out using distilled water for steam for a time period of about 48 hours. The surface coke deposited on the surface of thermowell is recorded as 0.26 g at the end of 48 hour run when the furnace is opened after cooling. The reproducibility of the run is tested by repeating the run under same conditions. Example 2: Hydrocarbon cracking with plant steam condensate as water without employing the composition of the present disclosure (Control Run)

[77] An experimental run (R-408) is carried out under the same conditions as the blank run described in example 1, except that the plant steam condensate obtained from quench water comprised of caustic (NaOH), which is being added for pH adjustment in place of water. The blank run is carried out for about 48 hours and the surface coke deposited in presence of caustic is found to be about 0.293 g same range as that of the base runs (Example 1). The quantity of spalled coke from the reactor is found to be 13.28 g. This data is considered as bench mark in assessing the composition of the present disclosure for coke reduction estimation.

Example 3: Hydrocarbon cracking in presence of the composition of the present disclosure

[78] An experimental test run (R-412) is carried out under the same conditions as the blank run described in example 1, wherein along with the plant steam condensate the composition of the present disclosure is introduced, by dissolving the composition in plant steam condensate at a concentration of about 4ppmw, wherein calcium acetate is about 65wt% and potassium carbonate is about 35wt%. The concentration of the composition is maintained at 4ppmw throughout the 48h run of the experiment. The amount of surface coke that is formed during the reaction is found to be much lesser than the runs in Examples 1 and 2 above, and is found to be 0.115 g, as disclosed in Figure 2. The amount of surface coke that is formed during the reaction comprising the composition of the present disclosure is reduced by about 60% when compared to benchmark base run performed in Example 2 and as described in Figure 3. The amount of spalled coke is found to be 8.61 grams, which is reduced by about 35% when compared to benchmark base run performed in Example 2, as also described in Figure 4. Further addition of the composition of the present disclosure also did not show any negative effect on product yield, as described in Figures 5 and 6. The components of the final product obtained after the base run of example 2 (without the composition) and the present experiment (with the composition) appear to be very similar in quantity and quality. Further, Inductive Couple Plasma (ICP) analysis of coke and liquid samples that were formed showed no evidence of corrosion, indicating that the composition of the present disclosure does not cause corrosion

Example 4: Memory effect of the composition of the present disclosure (Trial 1).

[79] An experimental run (R-413) is carried out to test the effect (memory effect) of the residue elements of the composition that was used in example 3 in the reactor system. Hence, in the same reactor, this experimental run is carried out under the same conditions as the blank run described in Example 2 i.e. there is no addition of composition of the present disclosure through plant steam condensate to test the memory effect of the elements of the composition of the present disclosure left over in the reactor system after one cycle of cracking process.. After completion of run, the surface coke was found to be 0.145 g, which is about 50.6% reduction in surface coke when compared to the coke formed in blank run of example 2. Further, the spalled coke is found to be 9.95g, which is about 25% reduction in spalled coke when compared to the spalled coke formed in blank run of example 2. The reduction of the surface coke and spalled coke in this example is due to the presence of residue elements of the composition of present disclosure that was used in example 3. This memory run is represented by Ml and the results are provided in figures 2 to 4.

Example 5: Memory effect of the composition of the present disclosure (Trial 2).

[80] An experimental run (R-414) is carried out to further test the memory effect of the residue elements of the composition of the present disclosure left over in the reactor after trial 1 of example 4. This experimental run is carried out under the same conditions as the first memory run as disclosed in example 4. The amount of surface coke that is formed at the end of 48 hour run length is found to be 0.142g, which is about 51% reduction in the surface coke when compared to the surface coke formed in the blank run of Example 2. Further, the amount of spalled coke is found to be 8.52 g, which is about 35.8% reduction in the spalled coke when compared to the spalled coke formed in the blank run of Example 2. Furthermore, no evidence of corrosion was observed by Inductive Couple Plasma (ICP) analysis of the spalled coke sample. The memory run of example 5 is represented by M2, and the results are provided in figures 2 to 4.

In view of the data presented in examples 4 and 5, the memory effect of the composition of the present disclosure is very evident. Because, even after two blank runs without the composition of the present disclosure, about 50% reduction in the surface coke and about 25% to 35% reduction is spalled coke was observed, which clearly establishes the sustainable memory effect of the elements of the composition even after the primary run with the composition is completed. [81] Further, inductively coupled plasma (ICP) analysis of coke samples from examples 3, 4 and 5 above also showed reduction in metal leaching after addition of the composition of the present disclosure and during the memory runs, respectively when compared to the blank run of example 2. The results are illustrated in Figure 6. Example 6: Elemental analysis and downstream effect of elements from the additive mixture

[82] Element analysis is carried out for all the streams that include bubbler water through which product gas stream is passed, steam condensate, organic liquid product, hydrocarbon feed, aqueous additive solution, TLE wash water, spalled coke, decoking gas and decoking steam condensate, to analyse the effect of elements present in the composition of the present disclosure and where they land up, post completion of the experiments. The results obtained indicate that the elements of the composition land up in the decreasing order in - organic liquid product, spalled coke, steam condensate and decoking steam condensate and, around 1%) of the total elements formed can land up in TLE. Further, the organic liquid stream goes for separation of various products and the elements would be retained in oil and Carbon Black Feed Stock (CBFS). The elements of the composition that are deposited on surface coke formed on the reactor surface are washed along with decoking steam water and settle in steam condensate. Thermogravimetric analysis (TGA) of coke sample also show reduced metal content in test runs comprising the composition as disclosed in Figure 7 and thus supporting the observation of reduced metal leaching in test run comprising the composition as reported by ICP analysis. Further, pH of all the samples is found to be within the range as that of the plant in the test run with the composition (R-412) as presented below.

[83] The product gases are passed through water in a glass bubbler to dissolve the elements, the sample is noted as BWR. After the run, hot water is passed through condenser and collected for analysis which is denoted as TLEW. Sample from steam condensate sent for analysis is called LPRW. Cracker liquid product is extracted with HN03 to extract additive elements in to it which is denoted as ORGW.

[84] The present disclosure in view of the above described illustrations and various embodiments, is thus able to successfully overcome the various deficiencies of prior art and provide for an improved process for reducing formation and/or deposition of coke in reactor systems during cracking of hydrocarbons, by employing the composition comprising of metallic salts such as potassium carbonate and calcium acetate, optionally along with sulfur containing compound which decreases the coke formation and/or deposition up to 60% without effecting downstream units.

[85] In the specification the expressions cracking, cracking of hydrocarbon, hydrocarbon cracking, cracking process are used interchangeably, wherein the expressions cracking, cracking of hydrocarbon, hydrocarbon cracking and cracking process refer to the same subject matter, wherein organic molecules such as long chain hydrocarbon are broken down into simpler molecules such as lighter hydrocarbon by breaking the carbon-carbon bonds.

[86] Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein.

[87] The foregoing description of the specific embodiments fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

[88] Throughout this specification, the word "comprise", or variations such as "comprises" or "comprising" wherever used, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[89] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

[90] The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

[91] Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

[92] While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

REFERENCE NUMERAL TABLE:

SI. No. Reference No. Description

1 100 System. 10 Naphtha Tank.

12 Water Tank.

14 Naphtha Balance.

16 Water Balance.

18 Naphtha Metering pump.

20 Water Metering pump.

22 Naphtha Vaporizer.

24 Water Vaporizer.

26 Mixer.

36 Reactor coil.

38 Heated Furnace.

44 Transfer Line heat Exchanger 1.

46 Transfer Line heat Exchanger 2.

48 Gas liquid separator.

50 Wet gas meter.

52 CO/C0₂ Analyzer.

54 and 56 Gas Chromatography.

Claims

We Claim:

1. A composition comprising alkali metal salt and alkaline metal salt, optionally along with sulfur containing compound, wherein the composition reduces coke formation during hydrocarbon cracking.

2. The composition as claimed in claim 1, wherein the alkali metal salt is potassium carbonate and alkaline earth metal salt is calcium acetate; wherein the concentration of the potassium carbonate and the calcium acetate is ranging from about lppmw to 4ppmw; and wherein in the said concentration, the potassium carbonate is about 35wt% and the calcium acetate is about 65wt%.

3. The composition as claimed in claim 1, wherein the sulfur containing compound is selected from a group comprising dimethyl disulfide, dimethyl sulfide, diethyl sulfide, diethyl disulfide carbon disulfide and dimethyl sulfoxide, or any combination thereof, and concentration of the sulfur containing compound is ranging from about 50ppmw to 250 ppmw.

4. The composition as claimed in claim 1, wherein the composition is soluble in water and polar solvent, independently.

5. The composition as claimed in claim 1, wherein the composition reduces coke formation by at least 40% during hydrocarbon cracking when compared to the hydrocarbon cracking without the composition; wherein the composition reduces surface coke by at least 60% during hydrocarbon cracking when compared to the hydrocarbon cracking without the composition; and wherein the composition reduces spalled coke by at least 35% during hydrocarbon cracking when compared to the hydrocarbon cracking without the composition.

6. The composition as claimed in claim 1, wherein the composition further reduces coke formation by memory effect of the composition during hydrocarbon cracking, wherein the memory effect of the composition is retained for at least two cycles of the hydrocarbon cracking; and wherein the surface coke is reduced by at least 50% and the spalled coke is reduced by at least 25%, individually in subsequent cycles during the hydrocarbon cracking when compared to the hydrocarbon cracking without the composition. .

7. The composition as claimed in claim 1, wherein the composition reduces metal leaching by at least 40% during hydrocarbon cracking when compared to the hydrocarbon cracking without the composition.

8. A method for reducing coke formation during hydrocarbon cracking, said method comprises step of introducing a composition comprising potassium carbonate and calcium acetate, optionally along with sulfur containing compound in to a reactor system and subjecting the reactor system to hydrocarbon cracking.

9. The method as claimed in claim 8, wherein the composition is introduced into the reactor system along with water or hydrocarbon or both; wherein the hydrocarbon is selected from a group comprising naphtha, gas oil, ethane and propane, or any combination thereof; and wherein the reactor system is cracker reactor.

10. The method as claimed in claim 8, wherein concentration of the potassium carbonate and the calcium acetate is ranging from about lppmw to 4ppmw, in the said concentration, the potassium carbonate is about 35wt% and the calcium acetate is about 65wt%.

11. The method as claimed in claimed 8, wherein the sulfur containing compound is selected from a group comprising dimethyl disulfide, dimethyl sulfide, diethyl sulfide, diethyl disulfide carbon disulfide and dimethyl sulfoxide, or any combination thereof, and concentration of the sulfur containing compound is ranging from about 50ppmw to 250 ppmw.

12. The method as claimed in claim 8, wherein the hydrocarbon cracking is carried at a temperature ranging from about 800°C to 850°C .

13. The method as claimed in claim 8, wherein coke formation during the hydrocarbon cracking is reduced by at least 40%, wherein surface coke during the hydrocarbon cracking is reduced by 60%; and wherein spalled coke during the hydrocarbon cracking is reduced by at least 35%.