INTEGRATED METHOD FOR THERMAL CONVERSION AND INDIRECT COMBUSTION OF A HEAVY HYDROCARBON FEEDSTOCK IN A REDOX CHEMICAL LOOP FOR PRODUCING HYDROCARBON STREAMS AND CAPTURING THE CO2 PRODUCED

Abstract

The invention relates to an integrated method for thermal conversion and indirect combustion of a heavy hydrocarbon feedstock in a redox chemical loop for producing hydrocarbon streams. The heavy hydrocarbon feedstock (1) is brought into contact with inert particles (2) in a thermal conversion zone (100). Thermal conversion in the absence of hydrogen, water vapour and a catalyst produces a first gaseous effluent of hydrocarbon compounds (4) and coke, which effluent is deposited on the inert particles (5). The latter is then burned in a redox chemical loop (200) in the presence of oxygen-carrying solid particles (6). The inert particles thus flow between the thermal conversion zone (100) and a reduction zone (300) of the chemical loop while the oxygen-carrying solid particles flow between the oxidation (400) and reduction zones (300) of the chemical loop.

Claims

1. A method for converting a heavy hydrocarbon feedstock into a lighter hydrocarbon stream and coke by thermal conversion and coke conversion by combustion in a redox chemical loop wherein: a thermal conversion of the heavy hydrocarbon feedstock is carried out in a thermal conversion zone by bringing it into contact with hot inert particles to produce, in the absence of dioxygen and a catalyst, optionally in the presence of water vapour and/or dihydrogen, a first gaseous effluent of hydrocarbon compounds and coke, the latter being deposited on the inert particles, the coked inert particles are discharged from the thermal conversion zone and are sent to a reduction zone of a redox chemical loop in which particles of an oxygen-carrying solid flow, a combustion of the coke deposited on the discharged coked inert particles is carried out in the reduction zone to produce a second gaseous effluent, hot inert particles at least partially freed from coke and oxygen-carrying solid particles in the reduced or partially reduced state, the oxygen-carrying solid particles in the reduced or partially reduced state forming a bed located above a bed formed by the inert particles in the reduction zone, the oxygen-carrying solid particles in the reduced or partially reduced state are discharged from the reduction zone and at least partially returned to an oxidation zone of the chemical loop to oxidise them by means of an oxidising gas before reintroducing them into the reduction zone, the hot inert particles which are at least partially freed from coke are discharged from the reduction zone and at least partially returned to the thermal conversion zone, the energy necessary for the thermal conversion reaction being at least partially provided by the exothermic combustion of all or part of the coke in the reduction zone.

2. The method according to claim 1, wherein the second gaseous effluent produced in the reduction zone is recovered and separated from the oxygen-carrying solid particles in the reduced or partially reduced state.

3. The method according to claim 2, wherein the second gaseous effluent, produced in the reduction zone and separated from the oxygen-carrying solid particles in the reduced or partially reduced state, is cooled in at least one heat exchanger by heat exchange with a fluid, for example water in liquid form, and, optionally, the heated fluid is used to generate thermal or electrical energy.

4. The method according to claim 1, wherein the hot inert particles form a non-entrained bed in the thermal conversion zone passed through by the flowing heavy feedstock.

5. The method according to claim 1, wherein the first gaseous effluent originating from the thermal conversion zone is subjected, optionally directly, to fractionation in a fractionation zone, optionally after separation of coked inert particle fines.

6. The method according to claim 5, wherein the fractionation zone separates the first gaseous effluent at least into an incondensable gaseous fraction and a liquid fraction, and, optionally, at least one portion of said incondensable gaseous fraction is returned to the thermal conversion zone.

7. The method according to claim 1, wherein the oxygen-carrying solid particles in the reduced or partially reduced state originating from the reduction zone and separated from the second effluent, are partially recycled in the reduction zone.

8. The method according to claim 1, wherein the hot inert particles, which are at least partially freed from coke, are cooled before they are returned to the thermal conversion zone in a heat exchanger by heat exchange with a fluid, for example water in liquid form.

9. The method according to claim 1, wherein at least one fluid selected from: the second gaseous effluent after separation of the oxygen-carrying solid particles in the reduced or partially reduced state and optionally after cooling, the oxidising gas reduced during the re-oxidation of the oxygen-carrying solid particles after separation of the re-oxidised oxygen-carrying solid particles, is subjected to a purification treatment.

10. The method according to claim 1, wherein the heavy hydrocarbon feedstock is selected from hydrocarbon feedstocks with high sulphur content, atmospheric residues, vacuum residues, alone or in combination.

11. The method according to claim 1, comprising one or more of the following features: a particle size of the oxygen-carrying solid particles which is sufficiently lower than that of the inert particles, optionally lower by a factor from 1 to 1000, an average diameter of the oxygen-carrying solid particles and inert particles from 50 μm to 2 mm, a density of oxygen-carrying solid particles and inert particles from 500 to 6000 kg/m3, a superficial velocity of a fluidisation gas of the reduction zone from 30 to 300% of the terminal average fall velocity of the inert particles.

12. An installation for converting a heavy hydrocarbon feedstock for implementing the method according to claim 1, comprising at least: one thermal conversion reaction zone, devoid of supply of dioxygen and catalyst, optionally equipped with a supply of water vapour and/or dihydrogen, comprising a supply of heavy hydrocarbon feedstock, a supply of hot inert particles, a first conduit for discharging a first gaseous effluent comprising hydrocarbon compounds and a second conduit for discharging coked inert particles, the first discharge conduit being optionally equipped with a first gas-solid separation device to separate the first gaseous effluent from the coked inert particle fines, one redox chemical loop comprising a reduction zone and an oxidation zone in which particles of an oxygen-carrying solid flow, the reduction zone comprising a supply of hot coked inert particles connected to the second conduit for discharging coked inert particles from the thermal conversion zone, a supply of oxygen-carrying solid particles originating from the oxidation zone, a conduit for discharging the inert particles, which are at least partially freed from coke, connected to the supply of hot inert particles of the thermal conversion zone, a conduit for discharging the oxygen-carrying solid particles in the reduced or partially reduced state, the supply of oxygen-carrying solid particles being located in the lower portion of the reduction zone, under the supply of coked inert particles, and the oxidation zone comprising a supply of oxidising gas, a supply of oxygen-carrying solid particles in the reduced or partially reduced state connected to the discharge conduit of the reduction zone and a conduit for discharging the re-oxidised oxygen-carrying solid particles connected to the supply of oxygen-carrying solid particles of the reduction zone.

13. The installation according to claim 12, comprising at least one of the following features: a second gas-solid separation device for separating a second gaseous effluent from the oxygen-carrying solid particles in the reduced or partially reduced state located on the conduit for discharging the oxygen-carrying solid particles in the reduced or partially reduced state from the reduction zone, a third gas-solid separation device for separating the reduced oxidising gas exiting the oxidation zone from the re-oxidised oxygen-carrying solid particles located on the conduit for discharging the re-oxidised oxygen-carrying solid particles from the oxidation zone.

14. The installation according to claim 13, comprising a conduit for recycling oxygen-carrying solid particles in the reduced or partially reduced state originating from the second gas-solid separation device to the supply of the reduction zone.

15. The installation according to claim 12, comprising one or more heat exchangers selected from a heat exchanger to cool the second gaseous effluent originating from the second gas-solid separation device and a heat exchanger to cool the recycled inert particles in the thermal conversion zone.

16. The installation according to claim 13, comprising at least one of the following features: at least one purification system to purify the second gaseous effluent originating from the second gas-solid separation device, optionally downstream of said at least one heat exchanger, at least one other system for purifying the reduced oxidising gas originating from the third gas-solid separation device.

17. The installation according to claim 12, further comprising a fractionation zone supplied by the first conduit for discharging the first gaseous effluent from the thermal conversion zone, optionally downstream of the first gas-solid separation device, the fractionation zone being optionally equipped with a conduit for recycling an incondensable gaseous fraction supplying the thermal conversion zone.

Description

DESCRIPTION OF FIGURES

[0130] The invention is now described with reference to the appended, non-limiting drawings, in which:

[0131] FIG. 1 represents an exemplary embodiment of an installation implementing the method according to the invention.

[0132] In the FIGURE, the references relating to flowing fluids are in parentheses.

[0133] In a first step, the heavy hydrocarbon feedstock 1, for example a petroleum product with a high sulphur content, is subjected to a thermal conversion in a reaction zone 100, herein a non-entrained fluidised bed reactor, in the presence of hot inert particles 2. To this end, the reaction zone 100 comprises a supply 101 of heavy hydrocarbon feedstock 1 and a supply 102 of hot inert particles 2. The heavy hydrocarbon feedstock 1 and the hot inert particles 2 are introduced in the lower portion of the reaction zone 100. The hot inert particles 2 form a non-entrained bed 3 of constant height. The supply 101 of heavy hydrocarbon feedstock 1 is herein located above the supply 102 of hot inert particles 2. In contact with the hot inert particles 2 at high temperature, the heavy hydrocarbon feedstock 1 undergoes a thermal conversion, generating a gaseous effluent 4 (called first gaseous effluent in the following) progressing vertically upwards in the reaction zone 100 and coke being deposited on the hot inert particles 2. Generally, the heavy hydrocarbon feedstock 1 is introduced inside of the reaction zone 100 via injectors spraying it.

[0134] The reaction zone 100 also comprises a conduit 103 for discharging the first gaseous effluent 4 essentially consisting of hydrocarbon compounds most often mixed with coked inert particle fines 5. The discharge conduit 103, located in the upper portion of the reaction zone 100, is equipped with a first gas-solid separation device 104 to separate the first gaseous effluent 4 from coked inert particle fines 5. By way of example, the first gas-solid separation device 104 can comprise two cyclones.

[0135] The coked inert particle fines 5 are discharged from the system (5″) via the conduit 105, but a portion can be recycled (5′) to the reaction zone 100 via a conduit 106 opening into the bed 3 of inert particles. The coked inert particles 16 are discharged from the reaction zone 100 via the conduit 107. The conduit 107 herein withdraws the coked inert particles 16 from an upper portion, in particular from the top, of the bed 3 of inert particles inside the reaction zone 100. The coke deposited on the surface of the coked inert particles 16 is then burned in a chemical loop 200 which comprises a reduction zone 300 and an oxidation zone 400.

[0136] The reduction zone 300, herein a fluidised bed reactor, comprises a supply 301 of coked inert particles 16 originating from the reaction zone 100, a supply 302 of oxygen-carrying solid particles in the oxidised state 17 partially originating from the oxidation zone 400 and a gas-solid separator 305, a conduit 303 for discharging the inert particles at least partially freed from coke 7, which form at least one portion of the hot inert particles 2 entering the thermal conversion zone 100.

[0137] The reduction zone 300 also comprises a conduit 304 for discharging oxygen-carrying solid particles in the reduced or partially reduced state mixed with a second gaseous effluent 8, rich in CO.sub.2 and H.sub.2O when the combustion is total. This discharge conduit 304 is equipped with a second gas-solid separation device 305 to separate the second gaseous effluent 8 from the oxygen-carrying solid particles in the reduced or partially reduced state 9.

[0138] The supply 302 of oxygen-carrying solid particles in the oxidised state 17 is located in the lower portion of the reduction zone 300, under the supply 301 of coked inert particles 16. This promotes a counter-current of the coked inert particles 16 and the oxygen carrier particles in the oxidised state 17 in order to carry out the coke combustion. A fluidising gas, herein water vapour, is injected via a supply 19 provided under the supplies 301 and 302. The difference in particle size between these particles, the gas generated by the coke combustion and/or the injection of water vapour via the supply 19 allow this counter-current movement and the formation of two beds of particles: [0139] a lower bed 306 composed essentially of inert particles passed through by the oxygen-carrying solid particles in the oxidised state 17 transferring their oxygen for the coke combustion. [0140] an upper bed 307 composed essentially of oxygen-carrying solid particles in the reduced or partially reduced state 9.

[0141] A supply 18 of the reduction zone 300 (located herein under the supply 301 of coked inert particles and above the supply 302 of oxygen-carrying solid particles in the oxidised state 17) allows topping up with inert particles 2′ (loss by attrition withdrawn in 106′ or subtraction from the installation via the conduit 106″). The invention is however not limited to this position of the supply of fresh inert particles 2′, nor to these positions of the extractions of used/degraded inert particles.

[0142] The conduit 303 for discharging the mostly decoked inert particles 7, returns the latter to the supply 102 of the thermal conversion zone 100. This discharge conduit 303 is herein located at the bottom of the reduction zone 300. A heat exchanger 105 allows controlling the temperature at which the inert particles join the thermal conversion zone 100.

[0143] The oxidation zone 400, herein a fluidised bed reactor, comprises a supply 401 of oxidising gas 10, a supply 402 of oxygen-carrying solid particles in the reduced or partially reduced state 9′ originating from the second separation device 305 and a conduit 403 for discharging the oxygen-carrying solid particles in the oxidised or partially oxidised state 6.

[0144] In the example, this discharge conduit 403 is equipped with a third gas-solid separation device 404 for the separation of the oxygen-carrying solid particles in the oxidised or partially oxidised state 6 and oxidising gas whose oxygen content is lowered 11. The flow of oxygen-carrying solid particles in the oxidised or partially oxidised state 6 is partially or totally returned, in mixture with a portion of the reduced or partially reduced oxygen-carrying solid particles 9″, towards the reduction zone 300 via a conduit 405 connected to the supply 302. A portion 6′ of the oxygen-carrying solid particles in the oxidised state 6 can also be returned to the inlet of the oxidation zone in order to continue their oxidation. In order to maintain the capacity of the oxygen-carrying solid particles to transfer oxygen, a portion of the particles at equilibrium can be withdrawn from the system (via the conduit 403′) and a topping up with fresh particles (20) can be made, for example upstream of the reduction zone 300.

[0145] The oxidising gas generally being air, the oxidising gas whose oxygen content is lowered 11 is then air enriched in nitrogen. This air flow enriched in dinitrogen 11 can optionally be sent to a subsequent purification treatment.

[0146] The represented installation further comprises a fractionation zone 500 supplied with the first gaseous effluent 4 from the thermal conversion zone 100. The fractionation zone 500 is herein a distillation column under atmospheric pressure.

[0147] At the outlet of the fractionation zone, is recovered an incondensable gaseous fraction 13, a condensable gaseous fraction 14 and a liquid fraction 15. The distillation column can possibly be equipped with additional withdrawals to produce middle distillate cuts and a residue (or distillation bottom). The sulphur content of the different liquid fractions will be significantly lower than that of the feedstock 1. Depending on the sulphur content of the starting feedstock, some cuts may be valorised as marine fuel with a sulphur content of less than 0.5% m. At a minimum, the distillation column will produce an incondensable gas fraction 13 and a liquid fraction (syncrude) by mixing fractions 14 and 15. The incondensable gaseous fraction 13 could be partially recycled to the reaction zone 100 to improve the hydrodynamic conditions and therefore the performance in terms of conversion of the heavy feedstock 1. To this end, a compressor 502 might be provided on the conduit 501 recycling a portion of the incondensable gaseous fraction 13 to the reaction zone 100.

[0148] The represented installation herein comprises a heat exchanger 311 used to cool the second gaseous effluent 8 and produce water vapour 21 on the utility side which could be valorised either as a heat transfer fluid, or to generate electricity via a turbine. The represented installation finally comprises a purification system 312 for condensing water and subtracting the SOx and the NOx, or even dedusting the flow and/or converting the possibly produced CO (in the case of incomplete combustion of the coke) into CO.sub.2, thus producing a concentrated CO.sub.2 stream which can be transported and used or stored.