Method of Hydrocarbon Pyrolysis and Device for Implementing Same

Abstract

A method of oxidative pyrolysis involves heating hydrocarbon feedstock, heating a steam-oxygen mixture, combusting hydrocarbon feedstock in vapors of a steam-oxygen mixture in a special reactor, rapidly cooling the obtained products of incomplete combustion of chemical reactions in two steps, after which the cooled steam-gas mixture is directed to the fractionation unit. A hydrocarbons pyrolysis device has a steam-oxygen mixture and feedstock mixing chamber, a pyrolysis chamber and a coking reactor, a device for heating hydrocarbon feedstock, a device for heating steam-oxygen mixture coupled to a mixing chamber, a coking reactor having a device for supplying coolant to the pyrogas flow, a separation unit coupled to the coking reactor, a fractionation unit with an additional coolant supply device. Disposal of heavy oil residues by rapid coking with high economic efficiency and environmental safely while obtaining high-quality coke and producing aromatic compounds occurs without construction or additional installations.

Claims

1. A method of oxidative pyrolysis of liquid and gaseous hydrocarbons, the method comprising: heating of hydrocarbon feedstock and heating of a steam-oxygen mixture, combusting the hydrocarbon feedstock in vapors of a steam-oxygen mixture in a special reactor to obtain products of incomplete combustion of the hydrocarbon feedstock; rapidly cooling of the products of incomplete combustion in two stages, the first stage comprising: finely-dispersed spraying of products of combustion of heavy oil residues being mazut, gas oil, or cracking-residues into a flow of the products of incomplete combustion while reducing a temperature of a resulting steam-oxygen mixture to a temperature of the equilibrium value of combustion products during a short period of time; directing the resulting steam-oxygen mixture into a channel of a coking reactor; where the formation of, directing the steam/dust/gas along the channel to the separation unit while forming coke panicles and evaporating the coke particles off a surface of gas-oil fractions and causing partial cracking; separating obtained coke from the steam-gas mixture and transporting it for further processing; and the second stage comprising: cooling the steam-gas mixture to a temperature not lower than 250° C. by liquid hydrocarbons being oil, mazut, or gas-oil, by finely-dispersed spraying the liquid hydrocarbons into a pyrogas flow; and directing a cooled steam-gas mixture to a fractionation unit.

2. The method of oxidative pyrolysis according to claim 1, wherein the hydrocarbon feedstock is gasoline fractions, kerosene, gas oil, ethane, propane, or butane.

3. The method of oxidative pyrolysis according to claim 1, further comprising obtaining in the fractionation unit light, medium and heavy oil fractions with aromatic pyrolysis products dissolved in the fractions being benzene, toluene, xylene and naphthalene, and directing non-condensed gases comprising olefins being ethylene, propylene and butylene from the fractionation unit for further processing.

4. The method of oxidative pyrolysis according to claim 1, wherein the steam-oxygen mixture comprises water steam, a content of the water steam in the steam-oxygen mixture ranges from 0% to 50% by mass %.

5. The method of oxidative pyrolysis according to claim 1, wherein a content of the steam-oxygen mixture ranges from 15% to 25% of the mass of the hydrocarbon feedstock undergoing pyrolysis.

6. The method of oxidative pyrolysis according to claim 1, further comprising using the hydrocarbon gases methane, ethane, propane or butane as gaseous feedstock for pyrolysis to provide up to 40-50% of hydrogen volume in pyrolysis products.

7. The method of oxidative pyrolysis according to claim 1, wherein the fractionation unit is a cyclone-type apparatus.

8. The method of oxidative pyrolysis according to claim 1, wherein dimensions of the channel are determined in accordance with a capacity of a pyrolysis unit for the obtained pyrogas, and wherein the coke particles remain in the channel of the coking reactor for at least 2 seconds.

9. The pyrolysis method according to claim 1, further comprising separating the coke particles from pyrogas in the separation unit by an electro-filter by depositing fine coke particles on electrodes and by agglomerating the fine coke panicles by electro-filtration.

10. The method of oxidative pyrolysis according to claim 1, wherein the cooling of the steam-gas mixture at the first stage is carried out for 0.005-0.03 seconds.

11. The method of oxidative pyrolysis according to claim 1, the temperature of the equilibrium value of the combustion products is selected within a range of not less than 450° C. and not more than 650° C.

12. A device for carrying out oxidative pyrolysis of liquid and gaseous hydrocarbons by a method according to claim 1, the device comprising: a mixing chamber for the steam-oxygen mixture and hydrocarbon feedstock; a pyrolysis chamber and a coking reactor, the pyrolysis chamber being made as a fire-blocking gate with longitudinal channels in which combustion reactions occur; a device for heating the hydrocarbon feedstock, a device for heating the steam-oxygen mixture coupled to a mixing chamber for mixing the steam-oxygen mixture and the feedstock; the coking reactor and a separation unit coupled to the coking reactor, wherein an entrance to the coking reactor is a quenching zone, the entrance comprising a device for supplying coolant to the pyrogas flow; and the separation unit coupled to the fractionation unit by a channel comprising an additional device tor supplying the coolant.

13. The device for oxidative pyrolysis according to claim 12, wherein the devices for supplying the coolant are made in a form of a belt of spray nozzles for supplying the coolant under pressure.

14. The device for oxidative pyrolysis according to claim 12, wherein the separation unit for separating coke particles from pyrogas comprises at least two electro-filters capable of intermittent switching as agglomerated carbon black accumulates on the electrodes of a working electro-filter.

15. The device for oxidative pyrolysis according to claim 14, wherein the electro-filters are capable of switching the flow of pyrogas to an electro-filter with cleaned electrodes.

16. The device for oxidative pyrolysis according to claim 14, wherein the electro-filters are capable of self shaking and transporting carbon to the cooling unit by means of a water steam or inert gas.

17. The device for oxidative pyrolysis according to claim 12, wherein the fire-blocking grate is made in a form of longitudinal channels of a size providing that the reagents remain in a channel for no longer than 0.003-0.01 seconds, and wherein the reagents move in the channels with a speed exceeding that of a flame propagation during combustion of the reagents.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The proposed method of pyrolysis of liquid and gaseous hydrocarbons and the device for its implementation are illustrated by drawings, where

[0050] FIG. 1 depicts the diagram of the device implementing the proposed method of pyrolysis;

[0051] FIG. 2 depicts the diagram of the separation unit (item 8 in FIG. 1);

[0052] FIG. 3 depicts the diagram of the fractionation unit (according to the method of distillation of hydrocarbon feedstock, pat. RU 2301250).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] The device (FIG. 1) contains a furnace 1 for heating hydrocarbon feedstock to 500-600° C., a furnace 2 for heating the oxidizer to 200-400° C. (i.e. oxygen 10% to 20% of the mass of feedstock or a mixture of oxygen 10% to 20% of the mass of feedstock and water up to 20%), a mixing chamber 3 of the oxidizer and feedstock with an ignition section 4 at the outlet of the mixing chamber, a fire blocking grate 5 in the channels of which combustion reactions take place, a belt of spray nozzles 6 through which “quenching” liquid is fed under pressure (a range of petroleum products, most often heavy residues: mazut, gas oil, cracking residue), a coking reactor 7 which is a hollow pipe, a separation unit 8 for separating coke from the pyrogas flow, a channel 9 for supplying steam-gas mixtures into the fractionation unit 11, a belt of injectors 10 for injecting coolant represented by a wide fraction of hydrocarbons (i.e. oil, gas condensate, gas oil or diesel fraction) for post-cooling of steam-gas-liquid mixture at the second step of pyrogas cooling.

[0054] The proposed method using the device is implemented as follows.

[0055] The pyrolysis feedstock is fed by a pump (not depicted in the drawings) to the heating furnace 1 (FIG. 1). There it is heated up to 500-600° C. and is then sent into the mixing chamber 3 of the steam-oxygen mixture and feedstock. Oxygen from the oxygen production unit (i.e. from the membrane air separation unit, not depicted in the drawings) is supplied under pressure to the furnace 2 and heated up to 300-400° C. Water steam is supplied separately at the temperature of 100° C. At the outlet of the mixing chamber 3 in the ignition section 4 there is a constant flame source from any type of ignition device. The ignited mixture enters the channels of the fire-blocking grate 5 with the thickness of 100 mm and with the channels' diameter of 8-12 mm. The shape of the channels can be cylindrical or conical, but it is important for the residence time of reagents in the channel to correspond to the rate of chemical reactions of oxidative pyrolysis determined experimentally and equal to about 0.003-0.01 seconds. In this case, the speed of movement of reagents in the channel cannot be lower than 30 msec, i.e. the speed of flame propagation, because otherwise combustion reactions might move into the mixing chamber 3. Knowing the total consumption of feedstock, it is possible to calculate the size of the fire-blocking grate and the number of channels by the selected diameter of the channels. For a rectangular channel the channel diameter is usually taken in the range of 8-12 mm, and for a conical channel up to 16 mm at the wide end. Pyrolysis reactions take place in the channels of the fire-blocking grate 5 and the red-hot grate itself serves as a stabilizer of combustion processes under conditions of lack of an oxidizer. At the outlet of the grate 5, a quenching liquid (for example, mazut) is supplied into the flow through the belt of injectors 6 for a sharp decrease in the flow temperature up to 600-650° C. The resulting steam-gas mixture enters the coking reactor 7 and then moves to the separation unit 8 in which the formed fine coke particles are separated from the flow and sent for cooling and further processing. The steam-gas mixture cleaned from coke enters the channel 9 where a cooling liquid (for example, oil) fed into the flow through the belt of injectors 10 reduces the temperature of the resulting steam-liquid mixture up to 350° C. The resulting steam-liquid mixture is sent to the fractionation unit 11.

[0056] The diagram of the separation unit (item 8 in FIG. 1) is given in FIG. 2. The flow of pyrolysis gases with coke particles enters one of the two electric filters 12. Fine coke particles settle on the electrodes 13 and form agglomerates and the pyrogas cleaned from coke is sent to the fractionation unit (item 11 in FIG. 1). As soon as a substantial amount of coke accumulates on the electrodes 13 the flow of pyrogas with coke particles is sent to the second electro-filter 12 and the flow is cleaned from coke through the second electro-filter. Meanwhile, a flow of water steam 14 (or inert gas) is sent to the first electro-filter 12 with simultaneous shaking of the accumulated coke from the electrodes. The flow of water steam picks up the pieces of agglomerated coke, partially cools them and the two-phase mixture of steam and coke particles 15 enters the cyclone separator 16. From the cyclone separator 16 the water steam cleaned from coke 17 is sent again to the cleaning of the electro-filter 12 and the coke from the cyclone 16 is sent for post-cooling and further processing as carbon black.

[0057] In FIG. 3 the diagram of the fractionation unit according to the method of distillation of hydrocarbon feedstock based on the patent RU No 2301250 is presented. The diagram depicts five cyclone separators C1-C5 (19, 22, 25, 28, 31) for separation of steam-liquid mixtures and four air cooling units AV01-AV04 (21, 24, 27, 30) for partial condensation of hydrocarbon steam. In case oil is used for cooling of pyrolysis gases from the outlets of 18 electro-filters 12 (FIG. 2) to the temperature of 360° C. and any liquid hydrocarbons undergo pyrolysis, then the fractionation unit (FIG. 3) works as follows. The steam-liquid mixture with a temperature of 360° C. enters the first cyclone separator C1 (19). From the cyclone C1 (19) the condensed phase (liquid) represented by hydrocarbons with a boiling point above 360° C. drains down the walls of the cyclone C1 (19) under the influence of gravity and after cooling enters the commodity park (mazut fraction) through the outlet 20. The mixture of steams with boiling points below 360° C. comes from cyclone C1 (19) to the air cooling unit AV01 (21) where hydrocarbons with boiling points of 240°−360° C. condense. From AV01 (21) the steam-liquid mixture enters the cyclone C2 (22) where after separating the steam and condensed phases the liquid with boiling points of 240°−360° C. (component of diesel fuel) after cooling enters the warehouse through the outlet 23 (not depicted in the drawings) and the mixture of steams with boiling points below 240° C. enters AV02 (24). In AV02 (24) hydrocarbons with boiling points of 200° C.-240° C. condense and the resulting steam-liquid mixture enters the cyclone C3 (25) where after separation of the steam and condensed phases the liquid with boiling points of 200° C.-240° C. (component of diesel fuel with naphthalene dissolved in it) after cooling enters the naphthalene extraction unit (not depicted in the drawings) from where the fraction cleaned from naphthalene is mixed with the fraction of 240° C.-360° C. (for production of diesel fuel) and the mixture of steams with boiling points below 200° C. enters the AV03 (27). In AV03 (27) hydrocarbons with boiling points of 150° C.-200° C. condense and the resulting steam-liquid mixture enters the cyclone C4 (28) where after separation of the steam and condensed phases the liquid with boiling points of 150° C.-200° C. (gasoline component) enters the warehouse through the outlet 29, and the mixture of steams with boiling points below 150° C. enters AV04 (30). In AB04 (30) hydrocarbons with boiling points below 150° C. condense and the resulting steam-liquid mixture enters the cyclone C5 (31) where after separation of the gas and condensed phases the liquid with boiling points below 150° C. (component of gasoline with BTX dissolved in; BTX is a mixture of benzene, toluene and xylene) after cooling enters through the outlet 32 the BTX extraction unit 9 (not depicted in the drawings) from where the fraction purified from BTX enters for mixing with the fraction 150° C.-200° C. (for production of gasoline) and the warehouse. Gases cleaned from the condensed phase in cyclone C5 contain from 30 to 50% of olefins and are supplied for further processing through the outlet 33.

EXAMPLES FROM PRACTICAL APPLICATION

Example 1

[0058] The proposed method of hydrocarbon feedstock oxidative pyrolysis was implemented at an experimental plant of oxidative pyrolysis for processing 68 kg of straight-run gasoline per hour (boiling point IBP −180° C.). The feedstock was heated to 500° C.

[0059] A mixture of oxygen 11% (of feedstock consumption) heated to 300° C. and 8% of water steam heated to 100° C. was used as an oxidizer. The shape of the channels of the fire-blocking grate was of square form with the side of 8 mm and a wall with the thickness of 3 mm. The rate of outflow of combustion products was adopted at 50 msec with an oxidative pyrolysis reaction time of 0.003 sec and the length of the grate's channels of 150 mm. In total, 16 square-shaped grate channels were made with four channels on each side of the grate.

[0060] The calculated adiabatic temperature of reaction products was approximately 1100° C., and the real temperature taking heat losses into account was about 950° C. Mazut was used as a quenching liquid. According to calculations 1.92 kg of mazut was taken for quenching (cooling) to the temperature of 600-650° C. per 1 kg of the feedstock. For quenching, mazut from light oil was used with a yield of light oil products of about 71%. Therefore, the estimated yield of coke from such mazut was about 15% i.e. about 19.6 kg per hour. The temperature in the coking reactor was maintained in the range from 660° C. at the beginning of the reactor to 615° C. at the end of the coking reactor. The real yield of coke was 17.8-18.3 kg per hour. A modified electric filter for cleaning welding production gases was used as an electro-filter for deposition of coke particles in this model installation.

[0061] The average density of pyrogas at 650° C. was 0.82 kg/m.sup.3 and the density of the steam phase at this temperature was about 6 kg/m.sup.3.

[0062] The estimated weight content of pyrogas was 38.5% and the weight content of the steam phase was 61.5%. Therefore, the volume flow rate of the steam-gas mixture in the coking channel was 112.5 m.sup.3/h or 0.03125 m.sup.3/sec.

[0063] The diameter of the coking reactor was adopted at 0.2 m, the flow rate was 1 msec and the length of the channel of the coking reactor was 2.5 meters, hence the residence time of the particles in the coking reactor was at least 2 seconds.

[0064] After cleaning from the coke, the steam-gas mixture entering fractionation with the mass flow rate of 0.0546 kg/sec was cooled with oil to 350° C. Cooling was carried out with oil with an average yield of light fractions of 71% with a flow rate of about 0.03 kg/sec.

[0065] As a result, the following pyrolysis products were obtained*:

TABLE-US-00001 Product Yield in % (m) of type reaction products H.sub.2 0.8 CH.sub.4 12.0 C.sub.2H.sub.6 3.2 C.sub.2H.sub.4 24.0 C.sub.3H.sub.6 12.0 C.sub.3H.sub.8 1.4 C.sub.4 H.sub.6 2.4 C.sub.4 H.sub.8 4.0 BTX 7.5 naphthaline 4.5 [0066] Pyrolysis gases were selected for analysis at the outlet of the fractionation unit. The indicators for BTX and naphthalene in pyrolysis products are obtained from the difference between these pyrolysis products dissolved in the corresponding fractions of the coolant (oil) and the indicators of BTX and naphthalene in the source oil. Data on product yields were obtained by a chromatograph.

Example 2

[0067] Modular combined oxidative pyrolysis device for processing 77 kg of atmospheric gas oil per hour (boiling point 180° C.-330° C.). The feedstock was heated to 500° C.

[0068] A mixture of oxygen (heated to 300° C.) in the amount of 11% and water steam (heated to 100° C.) in the amount of 8% of the feedstock consumption was used as an oxidizer. The shape of the channels of the fire blocking grate was square with the side of 8 mm and the wall thickness of 3 mm. The calculated flow rate of the combustion products was adopted at 60 msec, the reaction rate of oxidative pyrolysis was 0.003 sec, the length of the grate's channels was 150 mm. In total, 16 square-shaped grate's channels were made with four channels on each side of the grate. The calculated adiabatic temperature of the reaction products was approximately 1240° C. and the real temperature taking heat losses into account was about 980° C. Mazut was used as a quenching liquid. According to calculations, 2.0 kg of mazut was taken for quenching (cooling) to the temperature of 600-650° C. per 1 kg of feedstock. For quenching, mazut from light oil was used with a yield of light oil products of about 71%. Therefore, the estimated yield of coke from such mazut was about 15%, i.e. about 23.1 kg per hour. The temperature in the coking reactor was about 650° C. at the beginning of the reactor and 625° C. at the end of the coking reactor. The actual yield of coke was 28.4-29.5 kg per hour. It is obvious that heavy pyrolysis resins also underwent coking. A modified electric filter for welding production gases cleaning was used as an electro-filter for deposition of coke particles for this model device.

[0069] The total mass flow rate at the entrance to the coking reactor was 246.4 kg/h, of which the mass flow rate of the steam-gas mixture was:

246.4−29.0=217.4 kg/h

[0070] The average density of pyrogas at 650° C. turned out to be equal to 0.82 kg/m.sup.3, and the density of the steam phase at this temperature was about 6 kg/m.sup.3.

[0071] The estimated mass fraction of pyrogas was 38.0% and the mass fraction of the steam phase was 62.0%. The diameter of the coking reactor was adopted at 0.2 m, the flow rate was about 1 msec, and the length of the channel of the coking reactor was 2.5 meters, therefore, the residence time of the particles in the coking reactor was at least 2 seconds.

[0072] After cleaning from coke, the steam-gas mixture entering for fractionation with a mass flow rate of 0.0603 kg/sec was cooled with vacuum gas oil to 350° C. with a flow rate of about 0.033 kg/sec.

[0073] As a result, the following pyrolysis products were obtained:

TABLE-US-00002 Product Yield in % (m) of type reaction products H.sub.2 0.6 CH.sub.4 8.0 C.sub.2H.sub.6 2.4 C.sub.2H.sub.4 20.0 C.sub.3H.sub.6 9.5 C.sub.3H.sub.8 1.4 C.sub.4 H.sub.6 2.4 C.sub.4 H.sub.8 3.4 BTX 7.0 naphthtaline 11.5 [0074] Pyrolysis gases were selected for analysis at the outlet of the fractionation unit. The indicators for BTX and naphthalene in pyrolysis products are obtained from the difference between these pyrolysis products dissolved in the corresponding fractions of the coolant (gas oil) and the indicators of BTX and naphthalene in the initial gas oil. At the outlet of the separation unit a mixture of coolant and pyrocondensate was obtained, which also contains gasoline fractions with boiling points below 200° C. Data on product yields were obtained by a chromatograph.

Example 3

[0075] At the same model combined oxidative pyrolysis device, oxidative pyrolysis of methane gas was carried out in order to produce hydrogen. The consumption of ethane was 19 kg per hour. Ethane was heated to 500° C.

[0076] As an oxidizer, a mixture of 10% oxygen (heated to 300° C.) and 10% of water steam (heated to 100° C.) from the feedstock consumption was used. The shape of the channels of the fire blocking grate was square with the side of 8 mm and the wall thickness of 3 mm. The calculated flow rate of the combustion products was adopted at 60 msec, the reaction rate of oxidative pyrolysis was 0.003 sec, the length of the grate's channels was 150 mm. In total, 4 square-shaped grate's channels were made with 2 channels on each side of the grate. The calculated adiabatic temperature of the reaction products was approximately 1200° C. (and the real one, taking heat losses into account was about 1050° C.).

[0077] Mazut was used as a quenching liquid. According to the calculations, 2.2 kg of mazut was taken for quenching (cooling) to the temperature of 600-650° C. per 1 kg of the feedstock. For quenching, mazut from light oil was used with a yield of light oil products of about 71%. Therefore, the estimated yield of coke from such mazut was about 15%, i.e. about 6.3 kg per hour. The temperature in the coking reactor was maintained at 660° C. at the beginning of the reactor and 635° C. at the end of the coking reactor. The actual yield of coke was 6.8-7.2 kg per hour. (A modified electric filter for welding gases cleaning was used as an electro-filter for deposition of coke particles in this model device.)

[0078] The average density of pyrogas at 650° C. turned out to be 0.2 kg/m.sup.3 and the density of the steam phase at this temperature was about 6 kg/m.sup.3.

[0079] The estimated mass fraction of pyrogas was 31.0% and the mass fraction of the steam phase was 69.0%. The diameter of the coking reactor was adopted at 0.2 m, the flow rate was 0.9 msec, and the length of the channel of the coking reactor was 2.5 meters. Therefore, the residence time of the particles in the coking reactor was at least 2 seconds.

[0080] As a result, the following pyrolysis products were obtained:

TABLE-US-00003 Product Yield in % (m) of type reaction products H.sub.2 4.1 CH.sub.4 6.5 C.sub.2H.sub.6 2.4 C.sub.2H.sub.4 47.0 C.sub.3H.sub.6 0.5 C.sub.3H.sub.8 0.0 C.sub.4 H.sub.6 0.2 C.sub.4 H.sub.8 0.0 BTX 0 naphthaline 0 [0081] Pyrolysis gases were selected for analysis at the outlet of the fractionation unit. Data on product yields were obtained by a chromatograph.

[0082] The volume of the resulting hydrogen turned out to be at least 50% of the volume of pyrogas. In addition, as a result of coking of mazut (in %) from the original mazut the following were obtained: [0083] Coking gasoline—8%. [0084] Diesel fractions (boiling point 180° C.-330° C.)—17%. [0085] Distillates with boiling points above 330° C.—51%. [0086] Carbon black—16.5%.

[0087] The proposed group of inventions contributes to creation of an effective method of hydrocarbon feedstock oxidative pyrolysis, particularly gasoline fractions, kerosene, gas oil, ethane, propane, butane and a device for its performance for the purposes of obtaining olefins, aromatic hydrocarbons, hydrogen and carbon black.

REFERENCE LIST

[0088] 10 Mukhina T. N., Barabanov N. L., Menshikov V. A., Avrech G. L. Pyrolysis of hydrocarbons.—Moscow: Khimiya, 1987, Pp. 54-56, 118, 95-200. [0089] 2. Lebedev N. N. Chemistry and technology of basic organic and petrochemical synthesis, Moscow: Khimiya, 1988, p. 82. [0090] 3. Reichsfeld V. O. Reactional equipment and factories' machines, Leningrad: Khimiya, 1985, P. 121. [0091] 4. Miller, S. A. Acetylene, its properties, production and application. Translated from Leningrad, Khimiya, 1969, p. 398. [0092] 5. Proskuryakov V. A. Chemistry of oil and gas, St. Petersburg: Khimiya, 1995, P. 310. [0093] 6. Merkin A. P. Fragile miracle, Moscow: Khimiya, 1983, P. 167.