WO2023161609A1

WO2023161609A1 - Fcc electrolyser system

Info

Publication number: WO2023161609A1
Application number: PCT/GB2023/050373
Authority: WO
Inventors: Hacib Ben AISSA
Original assignee: Ceres Intellectual Property Company Limited
Priority date: 2022-02-24
Filing date: 2023-02-20
Publication date: 2023-08-31
Also published as: GB2618982A; TW202402394A; GB202202558D0

Abstract

A system comprising a regenerator (2) for regenerating a catalyst from a fluid catalytic cracking unit and at least one solid oxide electrolyser cell (36), wherein the regenerator (2) has an infeed for receiving an oxygen supply for enabling burning of catalyst coke off the catalyst for enabling regeneration of the catalyst for reuse in the fluid catalytic cracking unit and the at least one solid oxide electrolyser cell (36) comprises an anode, a cathode and an electrolyte, a steam input (42) and an oxygen rich gas output (56), wherein the oxygen rich gas output (56) connects to the infeed of the regenerator (2).

Description

FCC Electrolyser system

The present invention relates to an electrolyser system integrated into an industrial fluid catalytic cracking or FCC process.

Fluid catalytic cracking (FCC) is a conversion process commonly used in a petroleum refinery. It is used to convert hydrocarbon fractions of crude oil into gasoline, olefinic gases, and other products. The output from the process may be cracked gases, cracked naphtha, light cycle oils, slurry and heavy cycle oils (HCO).

FCC is commonly carried out on a portion of crude oil commonly known as heavy gas oil or vacuum gas oil (HVGO). Such oils may have an initial boiling point of at least 340 “Cat atmospheric pressure and an average molecular weight ranging from about 200 to 600. In some processes, the average molecular weight may be higher. During the process, this oil is heated to a high temperature and a moderate pressure, and brought into contact in a reactor, and/or a riser to that reactor, with a hot catalyst - usually a powdered catalyst due to the large surface area thereof, to break long-chain molecules of the oil into shorter- chain molecules. The output from the reactor is commonly collected as a vapour and fed to a fractionation or distillation column for separation into separate fractions. The catalyst is then recycled from the reactor in a regenerator so that it can be reused.

There are two conventional configurations for the FCC unit. The first is a "stacked" type where a reactor and a catalyst regenerator are contained in two separate vessels, with the reactor above the regenerator. A skirt connects between the vessels. The second is a "side-by-side" type where the reactor and catalyst regenerator are in two separate vessels, connected by piping. The present invention is applicable to either of these types.

Figure 1 shows a schematic flow diagram of a typical side by side FCC unit, with a reactor 1 , a regenerator 2, a boiler 3, a fractionation or distillation column 4, a settling column 5 and a riser 6.

During the FCC process, when the heavy gas oil or vacuum gas oil (HVGO) is mixed with the hot catalyst in the riser 6, and as it passes up the riser 6 and into the reactor 1 , long-chain molecules of the oil get converted into shorter-chain molecules. During this process, carbonaceous material (referred to as catalyst coke) will deposit onto the catalyst and reduce the catalyst’s effectiveness or reactivity. By the time it reaches the reactor 1 , or shortly thereafter, the catalyst will effectively be spent and will need to be regenerated before reuse. For this purpose the catalyst coke needs to be burnt off the catalyst, and that occurs in the regenerator 2. The reactor 1 thus has a fluid pathway to carry the spent catalyst into the regenerator 2. Conventionally the burning off is done by supplying oxygen and air, and the spent catalyst coke, to the regenerator 2. This then allows the coke to be burnt off the catalyst, with flue gases and regenerated catalyst then venting from the regenerator 2 through further fluid pathways. The regenerated catalyst is fed back to the bottom of the riser 6 to complete a loop, whereas the flue gases are usually fed to elsewhere in the plant. Commonly these flue gases - typically in excess of 700 degrees C - are used to generate steam in a boiler 3.

FCC units are designed to operate substantially continuously and there may be intervals of 3 to 5 years between scheduled shutdowns for routine maintenance. Furthermore, they are energy intensive due to the need to regenerate the catalyst. It would be advantageous to be able to increase the efficiency of the FCC units, while retaining long service intervals.

According to the present invention there is provided a system comprising a regenerator for regenerating a catalyst from a fluid catalytic cracking unit and at least one solid oxide electrolyser cell, wherein: the regenerator has an infeed for receiving an oxygen supply for enabling burning of catalyst coke off the catalyst for enabling regeneration of the catalyst for reuse in the fluid catalytic cracking unit; and the at least one solid oxide electrolyser cell comprises an anode, a cathode and an electrolyte, a steam input and an oxygen rich gas output, wherein the oxygen rich gas output connects to the infeed of the regenerator.

With this arrangement, the oxygen supply (for example ambient air) for the infeed of the regenerator can be enriched by oxygen rich gas exiting the oxygen rich gas output of the at least one solid oxide electrolyser cell during operation of the at least one solid oxide electrolyser cell, or potentially, the oxygen rich gas can be the oxygen supply.

In some embodiments the system is a fluid catalytic cracking system comprising a fluid catalytic cracking (FCC) unit that incorporates the regenerator and the at least one solid oxide electrolyser cell (also referred to herein as a SOEC or SOEL). In some embodiments the fluid catalytic cracking unit is for breaking long-chain molecules of a heavy gas oil or vacuum gas oil into shorter-chain molecules using a catalyst, and comprises a reactor, the regenerator, a fractionation or distillation column and a riser.

In some embodiments the oxygen rich gas will have an oxygen content greater than that of ambient air, i.e. greater than 21%. Preferably it will be 23 to 24% or higher.

By using the oxygen rich gas from the at least one SOEC, which gas is hot as it exits the at least one solid oxide electrolyser cell, there is no need (or a lesser need) to heat the oxygen supply within the regenerator. Further, the oxygen content will be higher than just ambient air, whereby less or no additional oxygen is needed to be provided to the regenerator. Yet further, less nitrogen will be provided in the oxygen supply (as a percentage of the gas that was nitrogen is now replaced by the increased amount of oxygen), whereby there is less nitrogen to heat, and less flue gases too. The efficiency of the regenerator is thus considerably improved. Further, a resulting lower gas velocity through the regenerator will help reduce equipment erosion.

In addition, by using oxygen enriched gas as the oxygen supply for the regenerator, the rate of burning of the coke can be increased, which in turn speeds up the rate of catalyst regeneration, thus enabling an increase in the oil throughput of the FCC unit. As the rate of cracking of the oil is a common bottleneck in oil refineries, the present invention helps to debottleneck the refinery containing this FCC unit.

In some embodiments the oxygen rich gas output from the at least one SOEC is thermally connected across a heat exchanger to a gas infeed for the at least one solid oxide electrolyser cell, such as an air feed or a nitrogen stream feed, or even a steam feed. In other words, the oxygen rich gas output from the at least one SOEC and a gas infeed for the at least one solid oxide electrolyser cell, such as an air feed or a nitrogen stream feed, or even a steam feed, are in fluid flow communication with at least one heat exchanger for exchanging heat between oxygen rich gas from the oxygen rich gas output and an infeed gas for the gas infeed. There may be a separate heat exchanger for each of these gas infeeds. This allows the oxygen rich gas (oxygen enriched nitrogen) exiting the oxygen rich gas output during operation of the at least one solid oxide electrolyser cell, which will be hot from the at least one solid oxide electrolyser cell, to be cooled, and for the infeed gas or gases for the gas infeed or infeeds to be heated. This then further improves the efficiency of the system.

The at least one solid oxide electrolyser cell usually has a hydrogen output. A hydrogen stream will exit the hydrogen output during use of the at least one solid oxide electrolyser cell. In some embodiments the hydrogen stream can instead or additionally be thermally connected across the gas infeed for the at least one solid oxide electrolyser cell via a heat exchanger. In other words, the hydrogen stream and the gas infeed(s) are in fluid flow communication with at least one heat exchanger for exchanging heat between the hydrogen stream and feed gas(es) for the gas infeed(s). This allows the hydrogen stream exiting the at least one solid oxide electrolyser cell, which will be hot from the at least one solid oxide electrolyser cell (i.e. relatively hotter than the gas infeed), to be cooled, and for the gas infeed into the at least one SOEC, which will be relatively colder than the hydrogen stream, to be heated. This then further improves the efficiency of the system.

In some embodiments, the regenerator has an outlet for flue gases, the outlet for flue gases being thermally connected across a boiler to produce steam, for example via a heat exchanger. In a typical system involving a heat exchanger, the flue gases and water in the boiler may be in fluid flow communication with at least one heat exchanger for exchanging heat between the flue gases and the water. In some embodiments the steam can be fed into the reactor of the FCC unit. Alternatively, or additionally, the steam may be fed into the at least one solid oxide electrolyser cell via the steam input - it may then provide all of the steam, or part of the steam, supplied to the at least one solid oxide electrolyser cell.

In some embodiments, a steam buffer tank may be provided between the boiler and the at least one SOEC to allow a buffer for the steam from the boiler to the at least one SOEC.

In some embodiments an oxygen rich gas tank may be provided between the at least one SOEC and the regenerator to allow a buffer for the oxygen rich gas supply from the at least one SOEC to the regenerator.

The present invention also provides a method for regenerating a catalyst from a fluid catalytic cracking unit, comprising providing a regenerator for regenerating a used catalyst from a fluid catalytic cracking (FCC) unit and at least one solid oxide electrolyser cell (SOEC), wherein: the regenerator regenerates the used catalyst for reuse in the fluid catalytic cracking unit by having an infeed that receives an oxygen supply for burning catalyst coke off the catalyst; and the at least one solid oxide electrolyser cell comprises an anode, a cathode and an electrolyte, an electrical current source, a steam input and an oxygen rich gas output, wherein the oxygen rich gas output is connected to the infeed of the regenerator to supply at least part of the oxygen supply to the regenerator.

In some embodiments the method also comprises providing the fluid catalytic cracking unit for breaking long-chain molecules of a heavy gas oil or vacuum gas oil into shorter- chain molecules using a fluid catalytic cracking system. The method thus also operates to break long-chain molecules of a heavy gas oil or vacuum gas oil into shorter-chain molecules using a catalyst, and comprises a reactor, the regenerator, a fractionation or distillation column and a riser.

In some embodiments the regenerator has a fluid passageway for flue gases, the flue gases powering an electrical generator, wherein electricity from the electrical generator provides the electrical current source for the at least one solid oxide electrolyser cell. Usually any such electrical current from the electrical generator would power a combustion air compressor for the regenerator, as usually it is necessary to pump ambient air into the regenerator. However, the power can be redirected instead to the SOEC, or excess power may be produced, which can then be redirected to the SOEC.

In some embodiments, as the present invention uses oxygen rich gas from the oxygen rich gas output of the at least one solid oxide electrolyser cell as a source gas for the regenerator, and since that oxygen rich gas can be under pressure as it exits the at least one solid oxide electrolyser cell (i.e. at a pressure higher than ambient pressure), the amount of power required for powering the combustion air compressor will be less than that found in the prior art, whereby there may be excess electrical power where none existed previously, or more excess electrical power than previously existed, so all of that excess electrical power can be redirected to power the at least one SOEC.

In some embodiments the method comprises a system in accordance with the first aspect of the present invention, or some if its embodiments. In each aspect of the present invention, in some embodiments the at least one solid oxide electrolyser cell operates at a temperature of between 400 and 1000 degrees centigrade. More typically it operates at a temperature of between 450 and 650 degrees centigrade.

In each aspect of the present invention, in some embodiments the regenerator operates with a flue venting temperature in excess of 700 degrees centigrade. More preferably the flue gas venting from the regenerator is hotter than the operating temperature of the at least one SOEC so that it can heat gas intakes of the at least one SOEC (e.g. the steam or the ambient air streams into the at least one SOEC). In some embodiments it can heat those gas intakes up to the preferred intake temperature of the at least one SOEC.

For each aspect of the present invention, in some embodiments the at least one solid oxide electrolyser cell is part of a stack of such cells, the oxygen rich gas outputs from the cells together connecting to the infeed of the regenerator.

In some embodiments the system comprises the regenerator for regenerating the catalyst from the fluid catalytic cracking unit and the at least one solid oxide electrolyser cell, wherein the at least one solid oxide electrolyser cell is part of a solid oxide electrolyser cell system, the inventive system comprising the regenerator and the solid oxide electrolyser cell system.

BRIEF DESCRIPTION OF DRAWINGS

These and other features of the present invention will now be described in further detail, purely by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows a prior art fluid catalytic cracking unit for breaking long-chain molecules of a heavy gas oil or vacuum gas oil into shorter-chain molecules;

Figure 2 shows a prior art solid oxide electrolyser cell;

Figure 3 shows an embodiment of the present invention in which at least one solid oxide electrolyser cell (SOEC/SOEL) is incorporated with an FCC unit; Figure 4 shows the embodiment of Figure 3, further modified to utilise the hydrogen output from the at least one SOEC to pre-heat the steam and air for the SOEC;

Figure 5 shows the embodiment of Figure 3, further modified to utilise flue gases from a regenerator of the FCC unit to generate electricity, the electricity being fed to the SOEC;

Figure 6 shows the embodiment of Figure 3, further modified to utilise steam from a boiler of the FCC unit used to generate electricity, the electricity and the steam being fed to the SOEC; and

Figure 7 shows a graph in which expected improvements of the conversion rate and load capacity, upon increasing from 21 % oxygen by volume (ambient air) to 27% by volume (oxygen enriched air), is shown.

SPECIFIC DESCRIPTION

Referring first of all to Figure 1 , there is shown a schematic flow diagram of a typical side by side fluid catalytic cracking (FCC) unit 10, with a reactor 1 , a regenerator 2, a boiler 3, a fractionation or distillation column 4, a settling column 5 and a riser 6.

In use, heavy gas oil or vacuum gas oil (HVGO) is mixed with a hot catalyst in the riser 6, and as it passes up the riser 6 and into the reactor 1 , long-chain molecules of the oil get converted into shorter-chain molecules, which converted gases 24 are then fed to the fractionation or distillation column 4 through pipework 26. During this process, carbonaceous material (referred to as catalyst coke) will deposit onto the catalyst and reduce the catalyst’s effectiveness or reactivity.

By the time the catalyst reaches the reactor 1 , or shortly thereafter, the catalyst will effectively be spent and will need to be regenerated before reuse. To do this, the catalyst is loaded into the regenerator 2 so that the catalyst coke can be burnt off in the regenerator 2.

The reactor 1 has a fluid pathway 7 to carry the spent catalyst into the regenerator 2. The regenerator 2 has an oxygen supply 8, which may be just air 9 or air plus an oxygen supplement as shown

In the regenerator 2, the catalyst coke is burnt off using the oxygen supply and heat, with flue gases 14 and regenerated catalyst 16 then venting from the regenerator 2 through further fluid pathways 18, 20.

The fluid pathway for the regenerated catalyst feeds the catalyst back to the bottom of the riser 6, whereat more oil for cracking is supplied, thus completing a loop for the catalyst.

The flue gases are instead usually fed to elsewhere in the plant. Commonly these flue gases - typically in excess of 700 degrees C - are used to generate steam 22 in the boiler 3.

The converted gases 24, after feeding into the fractionation or distillation column 4, will be separated into various fractions, and will be output therefrom through further pipework 28, 30, 32, 34. These fractions can vary, dependent upon the degree of fractionation or distillation carried out, but usually the outputs include cracked gasses through an upper pipe, cracked naphtha and light cycle oil through intermediate pipework 30, 32 and a slurry out through a bottom pipework 34.

The bottom pipework 34 connects to the settling column 5. The settling column 5 is for settling the slurry output from the distillation column 4 to enable the slurry (heavy oils) to be filtered or otherwise separated into, for example, HCO for output and recyclable oil for recirculation through the FCC unit via the riser 6.

The heavy gas oil or vacuum gas oil (HVGO) that is supplied to the FCC unit will typically be preheated high-boiling petroleum feedstock (at about 315 to 430 °C) consisting of long-chain hydrocarbon molecules. As discussed above it can be combined with recycled slurry oil from the bottom of the distillation column 4 and it is injected into the riser 6 where it is vaporised and cracked into smaller molecules of vapour by contact and mixing with the catalyst - which is itself provided as a very hot powdered catalyst from the regenerator 2. All of the cracking reactions usually take place in the catalyst riser within a period of 2-4 seconds. The hydrocarbon vapours "fluidize" the powdered catalyst and the mixture of hydrocarbon vapours and catalyst flows upward to enter the reactor.

Usually this is at a temperature of about 535 °C and a pressure of about 1.72 bar.

In a typical reactor 1 the cracked product vapours are separated from the spent catalyst by flowing through a set of two-stage cyclones within the reactor and the spent catalyst flows downward through a steam stripping section to remove any hydrocarbon vapours before the spent catalyst returns to the catalyst regenerator 2. The flow of spent catalyst to the regenerator 2 is usually regulated by a slide valve in the spent catalyst line 7.

The regenerator 2 usually operates at a temperature of about 715 °C and a pressure of about 2.41 bar. Hence the regenerator usually operates at about 0.7 bar higher pressure than the reactor 1. The combustion of the coke is exothermic and it produces a large amount of heat that is partially absorbed by the regenerated catalyst and provides the heat required for the vaporization of the feedstock upon recirculation back to the riser 6 and the endothermic cracking reactions that take place in the catalyst riser 6. For that reason, FCC units are often referred to as being 'heat balanced'.

The hot catalyst (at about 715 °C) leaving the regenerator 2 may flow into a catalyst withdrawal well where any entrained combustion flue gases are allowed to escape and flow back into the regenerator.

The flow of regenerated catalyst to the feedstock injection point below the catalyst riser may be regulated by a slide valve in the regenerated catalyst line.

The hot flue gas 14 exits the regenerator 2 usually after passing through multiple sets of two-stage cyclones that remove entrained catalyst from the flue gas 14.

The amount of catalyst circulating between the regenerator 2 and the reactor 1 can amount to about 5 kg per kg of feedstock, which is equivalent to about 4.66 kg per litre of feedstock. Thus, an FCC unit processing 75,000 barrels per day (11 ,900 m3/d) will circulate about 55,900 tonnes per day of catalyst. Even small improvements in the efficiency of operation of the regenerator can thus provide significant benefits.

The bottom product oil from the fractionating column 4 can contain residual catalyst particles which were not completely removed by the cyclones, or the like, at the top of the reactor 1 . For that reason, the bottom product oil is commonly referred to as a slurry or a slurry oil. Part of that slurry is recycled back into the main fractionating column. This may be above the entry point of the hot reaction product vapours so as to cool and partially condense the reaction product vapours as they enter the fractionating column. The remainder of the slurry oil is pumped through the settling column 5. The bottom oil from the settling column 5 contains most of the slurry oil catalyst particles and is recycled back into the catalyst riser 6 by combining it with the FCC feedstock oil. The clarified slurry oil or decant oil is withdrawn from the top of slurry settler 5 for use elsewhere in the refinery, as heavy cycle oil (HCO), a heavy fuel oil blending component, or as carbon black feedstock.

Depending on the choice of FCC design, the combustion in the regenerator 2 of the coke on the spent catalyst may or may not be complete combustion to carbon dioxide CO2. The combustion air flow is controlled so as to provide the desired ratio of carbon monoxide (CO) to carbon dioxide for each specific FCC design. The flue gas 14 from the regenerator 2 thus may contain CO and CO2 and it may be at or around 715 °C and at a pressure of 2.41 bar. In some prior art systems it is routed through a secondary catalyst separator containing swirl tubes designed to remove 70 to 90 percent of the particulates in the flue gas 14 leaving the regenerator. Although not needed in all downstream applications, it is beneficial where required to prevent erosion damage to downstream equipment. For example, in some plants the flue gas is fed to a turbo-expander, rather than a boiler or heat exchanger (or prior thereto), and separating out the particulates helps to avoid corrosion or erosion/wear of the blades in the turbo-expander.

The expansion of flue gas through a turbo-expander can provide sufficient power to drive a combustion air compressor for the regenerator 2, as required for applications that use ambient air.

Where fed to a boiler 3, the flue gas may be used as a fuel if it contains carbon monoxide - for example if the boiler is a steam-generating boiler (also referred to as a CO boiler), where the carbon monoxide in the flue gas is burned as fuel to provide steam for use elsewhere in the refinery.

Referring next to Figure 2, the operation of a SOEC is schematically illustrated. As shown, the SOEC 36 comprises an anode 48, a cathode 50, an electrolyte 52, the hydrogen output 40, the steam input 42, plus also a hot gas (usually nitrogen rich) input 54 and a hot gas (oxygen enriched) output 56. To operate the SOEC, a current source is applied across the SOEC, which then, through electrolysis, separates from the steam some of its components by splitting the water molecules, thus producing output stream of hydrogen and oxygen, with the hydrogen venting through the hydrogen output 40 and the oxygen enriching the hot gas output at the hot gas output 56. For this to occur, the steam is fed into the cathode, which is porous. When the current and thus a voltage is applied, the steam at the cathode-electrolyte interface is reduced to form pure H2 and oxygen ions. The hydrogen gas then diffuses back up through the cathode and is collected at its surface as hydrogen fuel, while the oxygen ions are conducted through the dense electrolyte. The electrolyte must be dense enough that the steam and hydrogen gas cannot diffuse through and lead to the recombination of the H2 and O2-. At the electrolyte-anode interface, the oxygen ions are oxidized to form pure oxygen gas, which is collected at the surface of the anode.

Referring next to Figure 3, an embodiment of the present invention is shown. In this embodiment, the FCC unit of Figure 1 is supplemented by connection to at least one solid oxide electrolyser cell 36, also known as SOECs or SOELs. It may be one SOEL/SOEC, a stack thereof, multiple stacks or multiple SOECs or SOELs. A schematic representation covering each of these is shown for simplicity.

Oxygen enriched gas 46 outputted from an oxygen enriched gas output 56 of the at least one SOEC 36 is connected to the oxygen supply 8 of the regenerator 2. In this embodiment it connects to an ambient air supply line 9 of the oxygen supply 8 via a feed line 44, and there is an additional oxygen supply line 14, although if the volume of oxygen enriched gas 46 from the at least one SOEC 36 is plentiful enough, the oxygen supply 8 could just be the oxygen enriched gas 46 from the at least one SOEC 36.

Whether the oxygen enriched gas 46 fed into the regenerator 2 is combined with ambient air 48 or is instead provided as the entirety of the oxygen supply 8 for the regenerator 2, the oxygen supply 8 supplied to the regenerator 2 will have a higher oxygen content than ambient air 48 as the at least one SOEC supplies oxygen enriched gas 46 at a percentage higher than 21 % due to the operation of the at least one SOEC separating oxygen out of steam 42 and using that oxygen to enrich the gas output from the anode side of the at least one SOEC 36. As a consequence, while processing the same volume of vacuum gas oil 50, the FCC unit 10 will require a smaller volume of oxygen supply 8, thus reducing the amount of flue gases 14, and in turn increasing the efficiency of the process versus an arrangement that uses just ambient air as the oxygen source. This in turn can debottleneck a refinery as more vacuum gas oil can be processed for a given reactor size, as more catalyst can be regenerated too for a given rate of ingestion of oxygen supply 8. This can even be achieved by retrofitting the regenerator 2 with the SOEC 36, thus avoiding a redesign of the plant and existing equipment.

A buffer tank 84 can be provided between the SOEC and the regenerator 2 to store oxygen enriched gas 46 from the SOEC 36. In this embodiment it is shown on the supply line 44.

As shown in Figure 3, the oxygen rich gas stream 46 from the at least one SOEC is thermally connected across a heat exchanger 58 to a gas infeed for the solid oxide electrolyser cell, such as an air feed (as shown an ambient air infeed) or a nitrogen stream feed. With this arrangement the oxygen rich gas stream 46 and the gas infeed are in fluid flow communication with a heat exchanger for exchanging heat between the oxygen rich gas stream 46 and the gas infeed. The oxygen rich gas stream 46 could additionally (or alternatively) be thermally connected across a (further) heat exchanger 60 to the steam feed 42, i.e. the oxygen rich gas stream 46 and the steam feed 42 being in fluid flow communication with a heat exchanger for exchanging heat between the oxygen rich gas stream 46 and the steam feed 42.

The use of heat exchangers 58, 60 in this manner allows the oxygen rich gas 46 (usually oxygen enriched nitrogen or oxygen enriched air) exiting the oxygen rich gas output 56 during operation of the at least one solid oxide electrolyser cell 36, which gas 46 will be hot from the solid oxide electrolyser cell 36, to be cooled, and for the gas infeed into the at least one SOEC to be heated. Preheating the air or gas infeed for the at least one SOEC 36 can further improve the efficiency of the system.

The at least one solid oxide electrolyser cell 46 usually has a hydrogen output 40. A hydrogen stream 38 will exit the hydrogen output 40 during use of the at least one solid oxide electrolyser cell 36.

A storage tank 80 may be provided for the hydrogen output from the SOEC 36. In this embodiment it is shown in the hydrogen output line from the SOEC 36.

In some embodiments, the hydrogen stream 38 can instead or additionally be thermally connected across the gas infeeds for the at least one solid oxide electrolyser cell 36 via one or more heat exchanger (shown in the embodiment of Figure 4, with a first heat exchanger 146 for the steam feed 42 and a second heat exchanger 148 for the ambient air feed 52). This alternative configuration allows the hydrogen stream 38 exiting the at least one solid oxide electrolyser cell 36, which will likewise be hot from the at least one solid oxide electrolyser cell 36 (i.e. relatively hotter than the gas infeed), to be cooled, and for the steam and air infeeds 42, 52 into the at least one SOEC 36, which will both be relatively colder than the hydrogen stream 38, to be heated. This then further improves the efficiency of the system.

Referring back to Figure 3, the regenerator 2 has an outlet for flue gases 14 at the top thereof. That outlet thermally connects the flue gases 14 to or across a boiler via a fluid pathway 18 to produce steam, for example via a heat exchanger or a CO boiler. This steam can be fed into the reactor of the FCC unit. Alternatively, or additionally, the steam may be fed 86 into the at least one solid oxide electrolyser cell 36 via the steam input 42 - it may then provide all of the steam, or part of the steam, supplied to the at least one solid oxide electrolyser cell 36 and the reactor.

A storage tank 82 may be provided for the steam output from the boiler. In this embodiment it is shown in the feed line 86 between the boiler’s steam output 22 and the heat exchanger 60 between the oxygen enriched gas line 44 and the steam feed 42.

In another embodiment, for example as shown in Figures 5, in which the flue gases 14 from the regenerator 2 are connected to an electrical motor-generator 92, for example upon expansion of the flue gases 14, electrical power 94 from the electrical motorgenerator 92 can be used to power the at least one SOEC 36. Further, that electrical power 94 may drive any required compressor or pump 62 for drawing the oxygen supply 8 into the regenerator 2. Yet further the flue gases 14 can also be connected to a boiler/heat exchanger 3 for forming steam 22, which steam 22 can thereafter be fed 86 into the SOEC 36. Yet further, the off gases 14 after passing through the boiler 3 can feed across the ambient air feed 52 to pre-heat the ambient air 52 via a further heat exchanger 96.

In another embodiment, for example as shown in Figures 6, in which the flue gases 14 from the regenerator 2 are connected to a boiler/heat exchanger 96 for forming steam 22 to generate power 94 from an electrical motor-generator 92, for example upon expansion of the steam 22, electrical power 94 from the electrical motor-generator 92 can be used to power the at least one SOEC 36. Further, that electrical power may drive any required compressor or pump for drawing the oxygen supply 8 into the regenerator 2. Yet further the steam can thereafter be fed 86 into the SOEC 36 and the off gases 14 after passing through the boiler 3 can feed across the ambient air feed 52 to pre-heat the ambient air 52 via a further heat exchanger 96.

Referring back again to Figure 3, in this embodiment as well the flue gases, after the boiler 3, thermally connect across a heat exchanger 96 to the gas infeed for the at least one SOEC 36, i.e. the flue gases and the gas infeed are in fluid flow communication with a heat exchanger 96 for exchanging heat between the flue gases and the gas infeed. Residual heat from the flue gases can then pre-heat the supplied gas for the at least one SOEC 36 - usually the boiler 3 will drop the temperature thereof to a point below that of the output gases of the at least one SOEC, whereby that heat exchanger 96 can be a first heat exchanger 96 to preheat the gas supply - ambient air in this embodiment.

An advantage of the present invention is that it can be retrofitted to existing FCC units as it connects to input and output lines, rather than into the inner workings of the system. Furthermore, if considered during initial design of the FCC unit, an even higher heat integration can be considered for ensuring a high overall energy efficiency for the FCC unit 10. This can then lead to even greater benefits, or an increase in the amount of benefit versus a retrofit.

The main benefits are a higher oil processing capacity due to increased oxygen availability in the regenerator, leading to an increased conversion of catalyst for reuse. There can also be a reduction of residue in the FCC process and an alleviation of problems with air blowers, as the flow from the at least one SOEC will already be under pressure. There can also be a reduction of gas flow in the regenerator for a given quantity of catalyst conversion as the higher oxygen content means less nitrogen and other gases. This in turn also reduces the gas flow through downstream cyclones. That reduced flow also reduces catalyst losses and erosion in the equipment.

These benefits are exemplified in the following table, comparing throughput for a given FCC unit, for an increase in oxygen content (volume %) in the oxygen supply 8 from 21% (ambient air only) to 22.2% oxygen (oxygen enriched air from at least one SOEC):

See also the graph shown in Figure 7, which plots expected improvements of the conversion rate upon increasing from 21 % oxygen by volume to 27% by volume. As can be seen, the conversion rate at 27% oxygen (oxygen enriched air) is expected to be significantly increased throughout the full illustrated range of feedrates compared to 21 % oxygen (ambient air), and likewise there is an expected increase in load capacity. As shown, the improvements are significant. Various embodiments of the present invention have been described above purely by way of example. Modifications in detail may be made to the invention within the scope of the claims as appended hereto.

Claims

CLAIMS:

1. A system comprising a regenerator for regenerating a catalyst from a fluid catalytic cracking unit and at least one solid oxide electrolyser cell, wherein: the regenerator has an infeed for receiving an oxygen supply for enabling burning of catalyst coke off the catalyst for enabling regeneration of the catalyst for reuse in the fluid catalytic cracking unit; and the at least one solid oxide electrolyser cell comprises an anode, a cathode and an electrolyte, a steam input and an oxygen rich gas output, wherein the oxygen rich gas output connects to the infeed of the regenerator.

2. The system of claim 1 , wherein the oxygen rich gas output from the at least one solid oxide electrolyser cell and a gas infeed for the at least one solid oxide electrolyser cell are in fluid flow communication with a heat exchanger for exchanging heat between an oxygen rich gas stream from the oxygen rich gas output and a feed gas for the gas infeed for the at least one solid oxide electrolyser cell, such as an air feed, a nitrogen stream feed or a steam feed.

3. The system of claim 1 or claim 2, wherein the at least one solid oxide electrolyser cell has a hydrogen output, wherein a hydrogen stream therefrom and a gas infeed for the at least one solid oxide electrolyser cell are in fluid flow communication with a heat exchanger for exchanging heat between the hydrogen stream an a feed gas for the gas infeed.

4. The system of any one of the preceding claims, wherein the regenerator has an outlet for flue gases, the outlet for flue gases being thermally connected across a boiler or a heat exchanger to produce steam.

5. The system of claim 4, wherein fluid connections are provided to carry the steam into a reactor of the fluid catalytic cracking unit.

6. The system of claim 4 or claim 5, wherein fluid connections are provided to carry the steam into the at least one solid oxide electrolyser cell.

7. The system of claim 4, claim 5 or claim 6 wherein a steam buffer tank is provided along the fluid connections to allow a buffer for the steam from the boiler.

8. The system of any one of the preceding claims, wherein an oxygen rich gas tank is provided between the at least one solid oxide electrolyser cell and the regenerator to allow a buffer for the oxygen rich gas supply from the at least one solid oxide electrolyser cell to the regenerator.

9. A method for regenerating a catalyst from a fluid catalytic cracking unit, comprising providing a regenerator for regenerating a used catalyst from a fluid catalytic cracking unit and at least one solid oxide electrolyser cell, wherein: the regenerator regenerates the used catalyst for reuse in the fluid catalytic cracking unit by having an infeed that receives an oxygen supply for burning catalyst coke off the catalyst; and the at least one solid oxide electrolyser cell comprises an anode, a cathode and an electrolyte, an electrical current source, a steam input and an oxygen rich gas output, wherein the oxygen rich gas output is connected to the infeed of the regenerator to supply at least part of the oxygen supply to the regenerator.

10. The method of claim 9, wherein the oxygen supply for the infeed of the regenerator is enriched by oxygen rich gas exiting the oxygen rich gas output of the at least one solid oxide electrolyser cell during operation of the at least one solid oxide electrolyser cell.

11 . The method of claim 9, wherein oxygen rich gas exiting the oxygen rich gas output of the at least one solid oxide electrolyser cell during operation of the at least one solid oxide electrolyser cell provides the oxygen supply for the regenerator.

12. The method of any one of claims 9 to 11 , wherein the regenerator has an outlet for flue gases, the outlet for flue gases being thermally connected across a boiler or a heat exchanger to produce steam.

13. The method of claim 12, wherein the produced steam, via the steam input, provides all of the steam supplied to at least one solid oxide electrolyser cell.

14. The method of any one of claims 9 to 13, wherein the oxygen rich gas output from the at least one solid oxide electrolyser cell and a gas infeed for the at least one solid oxide electrolyser cell are in fluid flow communication with a heat exchanger for exchanging heat between an oxygen rich gas stream from the oxygen rich gas output and a feed gas for the gas infeed, such as an air feed, a nitrogen stream feed or a steam feed.

15. The method of claim 14, wherein the oxygen rich gas exiting the oxygen rich gas output during operation of the at least one solid oxide electrolyser cell is hot from the at least one solid oxide electrolyser cell, and it heats the feed gas for the gas infeed into the at least one solid oxide electrolyser cell.

16. The method of any one of claims 9 to 15, wherein the at least one solid oxide electrolyser cell has a hydrogen output, wherein a hydrogen stream therefrom and a gas infeed for the at least one solid oxide electrolyser cell are in fluid flow communication with a heat exchanger for exchanging heat between the hydrogen stream and a feed gas for the gas infeed.

17. The method of claim 16, wherein the hydrogen stream exiting the at least one solid oxide electrolyser cell is hot from the at least one solid oxide electrolyser cell and it heats the feed gas for the gas infeed into the at least one solid oxide electrolyser cell.

18. The method of any one of claims 9 to 17, wherein the regenerator has a fluid passageway for flue gases, the flue gases powering an electrical generator, wherein electricity from the electrical generator provides the electrical current source for the at least one solid oxide electrolyser cell.

19. The method of any one of claims 9 to 18, wherein the regenerator has a fluid passageway for flue gases, the flue gases and a gas infeed for the at least one solid oxide electrolyser cell being in fluid flow communication with a heat exchanger for exchanging heat between the flue gases and a feed gas for the gas infeed, whereby the flue gases heat the feed gas.

20. The method of claim 19, wherein the flue gases preheat ambient air for the gas infeed.

21. The method of claim 19, wherein the regenerator operates with a flue venting temperature hotter than the operating temperature of the at least one solid oxide electrolyser cell and it heats the feed gas to a target intake temperature for the at least one solid oxide electrolyser cell.

22. The method of any one of claims 9 to 21 , wherein the method is carried out using the system according to any one of claims 1 to 8.

23. A fluid catalytic cracking system comprising a fluid catalytic cracking (FCC) unit that incorporates the system of any one of claim 1 to 8.

24. The method of any one of claims 9 to 21 , wherein the method is carried out using the fluid catalytic cracking system according to claim 23.