TECHNICAL FIELD
[0001] 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 2A 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
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
US 5 567 305,
US 5 358 626,
WO 98/11174 and
US 2003/183248 all disclose compositions for reducing coke formation.
[0007] 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
[0008] Described herein are compositions comprising alkali metal salt and alkaline metal
salts, optionally along with sulfur containing compound, wherein the composition reduces
coke formation during hydrocarbon cracking.
[0009] 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.
[0010] Also described herein is 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
[0011] 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:
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.
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 M1 and M2 (R-413
and R-414), respectively, demonstrating the memory effect of the composition.
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 M1 and M2 (R-413 and R-414), respectively, demonstrating the memory
effect of the composition.
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 M1 and M2 (R-413 and
R-414), respectively, demonstrating the memory effect of the composition.
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.
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.
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 M1 and M1 (R-413 and R-414), respectively,
demonstrating the memory effect of the composition.
DETAILED DESCRIPTION
[0012] 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.
[0013] A first aspect of the invention is a composition comprising potassium carbonate and
calcium acetate, wherein the composition reduces coke formation during hydrocarbon
cracking, wherein the concentration of the potassium carbonate and the calcium acetate
ranges from about 1 ppmw to 4ppmw; and wherein in the said concentration, the potassium
carbonate is about 35wt% and the calcium acetate is about 65wt%.
[0014] The composition optionally comprises a sulfur containing compound.
[0015] A second aspect of the invention is a method for reducing coke formation during hydrocarbon
cracking, said method comprises step of introducing a composition according to the
first aspect, optionally along with a sulfur-containing compound, into a reactor system
and subjecting the reactor system to hydrocarbon cracking
[0016] 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.
[0017] The concentration of the potassium carbonate and calcium acetate in the composition
ranges from about 1pppmw to 4ppmw.
[0018] The concentration of the potassium carbonate and calcium acetate in the composition
is ranging from about 1ppmw to 4ppmw, wherein in the said concentration, potassium
carbonate is about 35wt% and calcium acetate is about 65%.
[0019] In an embodiment, the concentration of the sulfur containing compound in the hydrocarbon
feed is ranging from about 50ppmw to 250 ppmw.
[0020] 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.
[0021] In an embodiment, the composition of the present disclosure is soluble in solvents
including but not limiting to polar solvent and non-polar solvent.
[0022] In an exemplary embodiment, the potassium carbonate and calcium acetate of the composition
is soluble in water or polar solvents.
[0023] 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.
[0024] In an exemplary embodiment, the composition of the present disclosure reduces coke
formation in a reactor system by at least 40%.
[0025] In another exemplary embodiment, the composition of the present disclosure reduces
coke formation in a reactor system by at least 60%.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] In an embodiment, the reactor system includes but is not limited to cracking reactor
unit employed for cracking of hydrocarbons.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] In a preferred embodiment, in the method of the present disclosure, the composition
is injected into the reactor system along with the steam.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] In an exemplary embodiment, the method of reducing formation of coke and/or deposition
of coke during cracking of hydrocarbons involves the following acts:
[0051] 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.
[0052] 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.
[0053] Described herein is a method in which the composition 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 1ppmw to 100ppmw, 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.
[0054] Described herein is a method in which the composition 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 1ppmw to 10ppmw, 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.
[0055] Described herein is a method in which the composition 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 1ppmw to 10ppmw, 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.
[0056] 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.
[0057] 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.
[0058] 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.
[0059] 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.
[0060] 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.
[0061] 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.
[0062] 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/CO2
analyser (52), two Gas Chromatographies (54 & 56) and the output of the GCs goes to
Personal Computer for area integration and processing.
[0063] 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.
[0064] 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)
[0065] 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)
[0066] 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
[0067] 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).
[0068] 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 M1 and the results are provided in figures 2 to 4.
Example 5: Memory effect of the composition of the present disclosure (Trial 2).
[0069] 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.
[0070] 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.
[0071] 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
[0072] 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.
[0073] 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.
|
R-408 |
R-412 |
Remark |
BWR pH |
6.389 |
8.44 |
Product stream |
TLEW pH |
2.839 |
6.089 |
Condenser water |
LPRW pH |
2.774 |
3.27 |
Steam condensate |
ORGW pH |
1.013 |
1.056 |
Organic layer extraction with HNO3 |
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
REFERENCE NUMERAL TABLE:
Sl. No. |
Reference No. |
Description |
1 |
100 |
System. |
2 |
10 |
Naphtha Tank. |
3 |
12 |
Water Tank. |
4 |
14 |
Naphtha Balance. |
5 |
16 |
Water Balance. |
6 |
18 |
Naphtha Metering pump. |
7 |
20 |
Water Metering pump. |
8 |
22 |
Naphtha Vaporizer. |
9 |
24 |
Water Vaporizer. |
10 |
26 |
Mixer. |
11 |
36 |
Reactor coil. |
12 |
38 |
Heated Furnace. |
13 |
44 |
Transfer Line heat Exchanger 1. |
14 |
46 |
Transfer Line heat Exchanger 2. |
15 |
48 |
Gas liquid separator. |
16 |
50 |
Wet gas meter. |
17 |
52 |
CO/CO2 Analyzer. |
18 |
54 and 56 |
Gas Chromatography. |
1. A composition comprising potassium carbonate and calcium acetate, wherein the composition
reduces coke formation during hydrocarbon cracking, wherein the concentration of the
potassium carbonate and the calcium acetate ranges from about 1 ppmw to 4ppmw; and
wherein in the said concentration, the potassium carbonate is about 35wt% and the
calcium acetate is about 65wt%.
2. The composition as claimed in claim 1, wherein the composition is soluble in water
and polar solvent, independently.
3. 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.
4. 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.
5. 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.
6. A method for reducing coke formation during hydrocarbon cracking, said method comprises
step of introducing a composition as claimed in claim 1, optionally along with a sulfur-containing
compound, into a reactor system and subjecting the reactor system to hydrocarbon cracking.
7. The method as claimed in claim 6, 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.
8. The method as claimed in claim 6, wherein the hydrocarbon cracking is carried at a
temperature ranging from about 800°C to 850°C.
9. The method as claimed in claim 6, 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%.
10. The method as claimed in claim 6, wherein the sulfur-containing compound is selected
from the group comprising dimethyl disulphide, dimethyl sulphide, diethyl sulphide,
diethyl disulphide, carbon disulphide and dimethyl sulfoxide, or any combination thereof,
and the concentration of the sulfur-containing compound in the hydrocarbon feed ranges
from 50 ppmw to 250 ppmw.
1. Composition comprenant du carbonate de potassium et de l'acétate de calcium, dans
laquelle la composition réduit la formation de coke pendant un craquage d'hydrocarbures,
dans laquelle la concentration du carbonate de potassium et de l'acétate de calcium
varie d'environ 1 ppm en poids à 4 ppm en poids ; et dans laquelle, dans ladite concentration,
le carbonate de potassium représente environ 35 % en poids et l'acétate de calcium
représente environ 65 % en poids.
2. Composition selon la revendication 1, dans laquelle la composition est soluble dans
l'eau et un solvant polaire, indépendamment.
3. Composition selon la revendication 1, dans laquelle la composition réduit la formation
de coke d'au moins 40 % pendant un craquage d'hydrocarbures par rapport au craquage
d'hydrocarbures sans la composition ; dans laquelle la composition réduit le coke
de surface d'au moins 60 % pendant un craquage d'hydrocarbures par rapport au craquage
d'hydrocarbures sans la composition ; et dans laquelle la composition réduit le coke
écaillé d'au moins 35 % pendant un craquage d'hydrocarbures par rapport au craquage
d'hydrocarbures sans la composition.
4. Composition selon la revendication 1, dans laquelle la composition réduit en outre
la formation de coke par effet de mémoire de la composition pendant un craquage d'hydrocarbures,
dans laquelle l'effet de mémoire de la composition est conservé pendant au moins deux
cycles du craquage d'hydrocarbures ; et dans laquelle le coke de surface est réduit
d'au moins 50 % et le coke écaillé est réduit d'au moins 25 %, individuellement dans
des cycles suivants pendant le craquage d'hydrocarbures par comparaison au craquage
d'hydrocarbures sans la composition.
5. Composition selon la revendication 1, dans laquelle la composition réduit la lixiviation
de métaux d'au moins 40 % pendant un craquage d'hydrocarbures par rapport au craquage
d'hydrocarbures sans la composition.
6. Procédé pour réduire la formation de coke pendant un craquage d'hydrocarbures, ledit
procédé comprend l'étape consistant à introduire une composition selon la revendication
1, facultativement avec un composé contenant du soufre, dans un système de réacteur
et à soumettre le système de réacteur à un craquage d'hydrocarbures.
7. Procédé selon la revendication 6, dans lequel la composition est introduite dans le
système de réacteur avec de l'eau ou un hydrocarbure ou les deux ; dans lequel l'hydrocarbure
est choisi dans un groupe comprenant le naphta, le gazole, l'éthane et le propane,
ou toute combinaison de ceux-ci ; et dans lequel le système de réacteur est un réacteur
de craquage.
8. Procédé selon la revendication 6, dans lequel le craquage d'hydrocarbures est effectué
à une température dans la plage allant d'environ 800°C à 850°C.
9. Procédé selon la revendication 6, dans lequel la formation de coke pendant le craquage
d'hydrocarbures est réduite d'au moins 40 %, dans lequel le coke de surface pendant
le craquage d'hydrocarbures est réduit de 60 % ; et dans lequel le coke écaillé pendant
le craquage d'hydrocarbures est réduit d'au moins 35 %.
10. Procédé selon la revendication 6, dans lequel le composé contenant du soufre est choisi
dans le groupe comprenant le disulfure de diméthyle, le sulfure de diméthyle, le sulfure
de diéthyle, le disulfure de diéthyle, le sulfure de carbone et le sulfoxyde de diméthyle,
ou toute combinaison de ceux-ci, et la concentration composé contenant du soufre dans
la charge d'hydrocarbures est dans la plage allant de 50 ppmw à 250 ppmw.