CA2861050A1 - Integrated method for the chemical-looping gasification and indirect combustion of solid hydrocarbon feedstocks - Google Patents

Abstract

The invention relates to an integrated method of gasification and indirect combustion in a chemical loop of a solid hydrocarbon feedstock in which: the solid hydrocarbon feedstock (1) is brought into contact with water (2) in a gasification reaction zone RG for discharging ashes (9) and producing a gaseous effluent (3) comprising synthesis gas and water; the reduction reaction zone RR of a chemical oxidation-reduction loop is fed with at least a portion of the gaseous effluent (3) produced in the gasification reaction zone to produce a gaseous effluent (4) concentrated in C02 and H 2 O, the oxygen-carrying solid particles from the reduction reaction zone RR of the chemical loop are reoxidized in the oxidation reaction zone RO by means of an oxidizing gas (6) and fumes are removed ( 7). The invention also relates to an installation for implementing said integrated process.

Description

INTEGRATED METHOD FOR GASIFICATION AND COMBUSTION
INDIRECT LOAD HYDROCARBON LOADS IN LOOP
CHEMICAL
FIELD OF THE INVENTION
The invention relates to an integrated gasification and combustion process indirect of solid hydrocarbons by oxidation-reduction in a chemical loop, for the heat production and / or the production of CO + H2 synthesis gas.
Terminology Process of Chemical Looping Combustion or CLC: In the following text, one CLC (Chemical Looping Combustion) means a process of oxidation loop reduction on active mass. It should be noted that, so Generally, the terms oxidation and reduction are used in relation to the state respectively oxidized or reduced active mass. The oxidation reactor is the one in which the redox mass is oxidized and the reactor of reduction is the reactor in which the redox mass is reduced.
Prior art In a context of growing global energy demand, the capture of carbon dioxide for sequestration has become a necessity inescapable in order to limit the emission of greenhouse gases prejudicial to the environment. The active mass loop oxidation reduction method, or Chemical Looping Combustion (CLC) in Anglo-Saxon terminology, allows to produce energy from hydrocarbon fuels while facilitating the capture of carbon dioxide emitted during combustion.
An oxygen carrier (metal oxide) is used for the transfer of oxygen continuously from the "air reactor" or "oxidation reactor" (RO) to the "fuel reactor" or "combustion reactor" or "reduction reactor" (RR) where

2 oxygen is supplied to the fuel. Thus, the direct contact between the air and the fuel is avoided. The resulting gas is rich in CO2 and is not diluted with nitrogen. It can thus be, after simple condensation of the produced water, compressed and stored. The reduced oxygen transporter (Me) is then transported to the air reactor to be re-oxidized (Me0), thus forming a chemical loop.
Solid fuels, having a high carbon to hydrogen ratio, produce a high amount of greenhouse gases. Thus, the combustion of the solid fuels is a particularly interesting application for CLC process. Various CLC configurations have already been developed and tested at the laboratory scale for the combustion of solids. However, some works of Further research is needed to ensure the feasibility of process- The most important technological challenges for the CLC process with solid charge concern solid-solid separation (oxygen carrier -unburned solid fuel) and the operation of the pressure high.
Description of the invention In order to overcome the aforementioned drawbacks, a new system is proposed to to burn (and / or gasify) a solid fuel without direct contact between the oxygen carrier and fuel.
Summary of the invention The invention relates to an integrated gasification and combustion process indirect in a chemical loop of a solid hydrocarbon feedstock in which:
the solid hydrocarbon feedstock (1) is brought into contact with water (2) in a RG gasification reaction zone in order to evacuate ashes (9) and producing a gaseous effluent (3) comprising synthesis gas:
CO, H2 and H20 water;
the reaction reduction zone RR is fed with a chemical loop of oxidation-reduction, in which particles of solid carrier of oxygen Me / Me0, by at least a part of the gaseous effluent (3) produced in the gasification reaction zone to produce a gaseous effluent (4) concentrated in CO2 and H2O,

3 the particles of oxygen-bearing solid obtained from the zone are reoxidized RR reduction reaction of the chemical loop in the zone reaction of oxidation RO by means of an oxidizing gas (6) and evacuated fumes (7).
Preferably, a portion (5) of the concentrated effluent is recycled to CO2 and H20 produced in the RR reduction zone to supply oxygen to the zone RG gasification reaction.
In one embodiment, the RR reduction reaction zone is fed to by the totality of the gaseous effluent (3) produced in the reaction zone of gasification RG, in order to produce heat that is recovered at the of the RO oxidation reaction zone or on the effluent transport lines gaseous.
In another embodiment, the reaction zone is fed with RR reduction by a part (3a) of the gaseous effluent produced in the zone RG gasification reaction in sufficient quantity to produce energy necessary for the gasification reaction, the other part (3b) allowing produce CO + H2 synthesis gas.
Preferably, the solid hydrocarbon feedstock is chosen from coal, the coked catalysts of the fluidized catalytic cracking (FCC) process or the cokes produced by the flexicoker process.
The invention also relates to a gasification and combustion plant in a chemical loop comprising:
a reaction gasification zone RG fed with a charge solid hydrocarbon (1) and water (2) and comprising an outlet pipe a gaseous effluent comprising synthesis gas and water (3) and a outlet duct of ash produced (9);
a chemical combustion loop comprising a reaction zone of RR reduction and an oxidation reaction zone RO, said reduction reaction zone RR being fed by at least a part of the gaseous effluent (3) coming from the gasification zone RG and by a

4 transport duct of oxygen-carrying solid particles (MeO) of said oxidation zone RO, and comprising an outlet pipe of an effluent gaseous (4) comprising CO2 and H2O;
and said oxidation reaction zone RO being supplied by a gas oxidant (6) and via a transport pipe of the solid carrier particles reduced oxygen (Me) from the reduction reaction zone, and comprising a transport pipe for evacuating the fumes (7).
The installation may include a pipe for transporting a part (5) of the gaseous effluent comprising CO2 and H2O (4) to the feed of the gasification zone RG.
In one embodiment, the installation may also include minus one heat exchanger in the oxidation zone RO (El) and / or on the flue gas transport duct (7) (E2).
In another embodiment, the outlet pipe of the effluent gaseous (3) is divided into two lines allowing the feeding of the RR reduction in synthesis gas for combustion (3a) and gas evacuation product synthesis (3b).
Detailed description of the invention Gasification of solid fuel The gasification reaction of the solid hydrocarbon feed takes place in the gasification reaction zone, in the presence of water vapor and possibly CO2 (in the event that some of the smoke is recycled exit from the combustion reactor RR to the supply of the gasification zone RG). The water introduced into the gasification zone can be vaporized and / or under pressure.
Under the operating conditions of the process according to the invention, namely a temperature advantageously between 800 and 1100 C, a pressure advantageously between 1 and 20 bars, a H20 / charge ratio advantageously between 7 and 10, the gasification is complete, of such so that only CO + H2 syngas and water are produced residual. At the exit of the gasification zone, we also recover the ash produced by the gasification of the solid hydrocarbon feed.
The gasification reaction is endothermic, the energy required is provided at least in part by the exothermic combustion of all or part of the synthesis produced in the chemical loop.
When all the syngas produced is sent to the combustion zone of the chemical loop, the energy provided by the combustion of synthesis gas is in excess of the requirements of the gasification reaction. It is so possible to recover excess energy in the form of heat, by means of one or more exchangers placed in the oxidation zone or on the lines of gas transportation.
When only part of the synthesis gas is sent to the combustion of the chemical loop, the energy provided by the combustion of the gas of synthesis is preferably only used to meet the needs of the gasification reaction. In this case, in order to maximize the production of synthesis gas at the end of the process, it is appropriate to send the combustion zone RR a part of the synthesis gas in a quantity strictly necessary to obtain the energy necessary for the gasification.
Combustion reaction of synthesis gas in chemical loop The CLC process involves the implementation of oxidation-reduction reactions of an active mass to decompose the combustion reaction into two successive reactions. A first oxidation reaction of the active mass, with air or a gas acting as oxidant, can oxidize the mass active.
A second reaction of reduction of the active mass thus oxidized using a reducing gas then makes it possible to obtain a reusable active mass and one a gaseous mixture essentially comprising carbon dioxide and water, even synthesis gas containing hydrogen and nitric oxide.
This technique thus makes it possible to isolate the carbon dioxide or the gas of synthesis in a gas mixture substantially free of oxygen and nitrogen.

Since combustion is generally exothermic, it is possible to produce energy from this process, in the form of steam or electricity, in having exchange surfaces in the mass circulation loop active or on gaseous effluents downstream of combustion reactions or oxidation.
US Patent 5,447,024 discloses a chemical loop combustion method comprising a first reactor for reducing an active mass by means of a reducing gas and a second oxidation reactor to restore the active mass in its oxidized state by an oxidation reaction with air wet. Circulating fluidized bed technology is used to enable the continuous passage of the active mass from its oxidized state to its reduced state.
The active mass, passing alternately from its oxidized form to its reduced form and conversely, describes an oxidation-reduction cycle.
Thus, in the reduction reactor, the active mass (MO) is firstly reduced to the Mx0y-2n-m / 2 / state via a Cnlim hydrocarbon (here the gas synthesis) which is correlatively oxidized to CO2 and H2O, depending on the reaction (1), or optionally in CO + H2 mixture according to the proportions used.
(1) CnHm + MxOy n CO2 + m / 2 H20 + Mx0y-2n-m / 2 In the oxidation reactor, the active mass is restored to its oxidized state (MO) in contact with the air according to the reaction (2), before returning to the first reactor.
(2) MxOy-2n-m12 (n + m / 4) 02 Mx0y In the equations above, M represents a metal.
The efficiency of the fluidized bed chemical loop combustion (CLC) process circulating relies to a large extent on the physico-chemical properties of the active redox mass.
The oxidation-reduction chemical loop combustion plant includes a oxidation reaction zone and a reduction reaction zone.
The oxygen-carrying solid is oxidized in an oxidation zone comprising at least less a fluidized bed at a temperature generally between 700 and 1200 C, preferably between 800 and 1000 C. It is then transferred to a reduction zone comprising at least one fluidized bed reactor where it is put in contact with the fuel (here the synthesis gas) at a temperature generally between 700 and 1200 C, preferably between 800 and 1000 C. The contact time typically varies between 10 seconds and 10 minutes, preferably between 1 and 5 minutes. The ratio between the quantity of mass circulation and the amount of oxygen to be transferred between the two areas The reaction mixture is advantageously between 20 and 100.
In the context of the integrated process according to the invention, the combustion of the gas of synthesis in the reduction zone RR is total, the flow of gas leaving the Reduction reactor is composed mainly of CO2 and water vapor.
A flow of CO2 ready to be sequestered is then obtained by condensation of the water vapour. Energy production is integrated into the combustion process CLC chemical loop by means of heat exchange in the area reaction and on the fumes of the oxidation zone which are cooled.
List of Figures Figure 1: Figure 1 shows the diagram of the integrated process according to the invention with gasification of the solid fuel, then chemical looping combustion of synthesis gas produced, in its application for the production of heat.
Figure 2: Figure 2 shows the diagram of the integrated process according to the invention with gasification of the solid fuel, then chemical looping combustion part of the synthesis gas produced, in order to provide the necessary energy to the gasification of the charge, in its application for the production of synthesis.
Figure 3: Figure 3 illustrates the example and represents the results steady Thermodynamics of 90/0 H20 and 100/0 Carbon simulated with software CHEMKINTm.
Description of figures The system for implementing the integrated gasification process and Chemical looping combustion according to the invention is composed of three reactors main: RG gasification reactor, RR reduction reactor, reactor RO oxidation.

Description of Figure 1: Figure 1 illustrates the process according to the invention with indirect combustion of solid hydrocarbon feedstock for the production of heat.
As a first step, the solid fuel (1) is gasified in the presence of water vapor (2) in the gasification reactor RG. The effluent obtained (CO + H2) comprising CO + H2 synthesis gas (3) is then transported to the RR reduction reactor where the gas is burnt in contact with the carrier of oxygen (Me / Me0) circulating in the chemical loop in the form of particles. The flue gas (4) leaving the RR reduction reactor contains mainly CO2 and H20. So, CO2 can be easily separated by condensing the water vapor. A fraction of this gaseous effluent consisting essentially of CO2 and H2O (5) can be injected into the gasification reactor RG in order to maintain the temperature or bring oxygen to gasify the fuel. The oxygen carrier in the state reduced Me is then transported to the oxidation reactor RO where it is re-oxidized into contact with the air introduced as an oxidizing gas (6). The degree difference oxidation between the reduced oxygen carrier (Me) at the outlet of the RR
and the oxygen carrier in the oxidized state (Me0) at the output of RO is AX.
A heat exchanger E present in the oxidation reactor (El) or on a flue gas transport line (E2) from the oxidation zone RO makes it possible to recover energy in the form of heat.
In a preferred embodiment, the fumes from the oxidation zone RO (7) can be cooled in exchanger E2 by heat exchange with water in liquid form (8) to supply the gasification reactor with water (2) in vapor form, and / or under pressure. This also presents the advantage of evacuating the installation of the cooled fumes (7). The ashes (9) are also removed from the facility from the RG gasification zone.
Description of Figure 2: Figure 2 illustrates the integrated process according to the invention with gasification of the solid hydrocarbon feed allowing both the CO + H2 synthesis gas production and heat production necessary to the gasification reaction. The scheme of the gasification system and indirect combustion in its application for the production of synthesis is shown in Figure 2. This system is similar to the configuration of the combustion process presented above, with a modification to the level of the gas outlet (3) of the gasification reactor RG. In this diagram, only a fraction of the synthesis gas (3a) produced in the RG is transported to the RR combustion reactor to produce the heat necessary for the gasification. The other part of the synthesis gas (3b) is considered as product of the process and is removed from the installation. The water vapor in the gas summary can be further condensed to improve the value heat of gas.
The process can therefore be used for the production of synthesis gas. This gas synthesis can be used as a feedstock for other transformation processes chemical, for example the Fischer Tropsch process for producing from syngas of liquid hydrocarbons with hydrocarbon chains long usable then as fuel bases.
Advantages of the process according to the invention The advantages of the process according to the invention are numerous.
Since there is no direct contact between the oxygen carrier and the fuel (which is previously gasified), the device allowing to put the process according to the invention can easily be adapted to processes of existing combustion by replacing the air inlet with steam water and CO2.
The integrated process according to the invention renders superfluous a solid separation -solid (oxygen carrier - unburned solid fuel), since the fuel is brought into contact with the oxygen carrier particles only once gasification, a separation which was previously necessary in published CLC for solid loads.
The method according to the invention, in its two embodiments, can operate with high pressure in the gasification reactor RG, while that the RO and RR reactors operate at atmospheric pressure. this allows in particular to produce high-pressure synthesis gas (for the process Fischer-Tropsch for example). Moreover, since the reaction zones RO

and RR operate at atmospheric pressure, the integrated process according to the invention allows a lower cost of operation and construction materials of RO and RR reactors. Finally, fuel leaks are minimized RO and RR reactors as well as the loss of the oxygen carrier to the reactor RG gasification.
The gasification is carried out under water vapor and not under air (absence of nitrogen), the synthesis gas obtained has a high calorific value.
The gasification is carried out under water vapor and not under air (absence nitrogen), the production of nitrogen oxides is minimized.
The main limitation of these processes is the supply of heat to the reactor of gasification because the gases have a limited heat capacity. In a mode of preferred embodiment, superheated steam (for example a temperature advantageously close to 1000 C). It should be noted that thanks to the injection of water vapor (and possibly CO2 from fumes of the reduction zone), there is 2 to 5 times more oxygen fed to the reactor of gasification compared to the case where air alone is injected directly into the reactor. This difference is related to the fact that we replace the nitrogen of the air by H20 or CO2.
The gasification can be conducted at atmospheric pressure or under pressure.

In the case of operation of gasification under pressure (for example at pressures between 5 and 50 bar, preferably between 20 and and 40 bar), the water vapor necessary for the gasification results from a cycle steam at least partially supplied with water resulting from reactor fumes of reduction in which the heat required to preheat and pressurize the Steam is recovered by exchange on the flue gases of the oxidation reactor (RO).
Different types of reactors can be implemented in different reaction zones RG, RO and RR of the process according to the invention. The reactor gasification RG can in particular be a circulating fluidized bed boiler or a bubbling fluidized bed. The technological choice of the type of reactors oxidation RO and RR combustion is also wide. It can be fluidized bed bubbling or circulating bed.
The solid hydrocarbon feedstocks used in the process according to the invention can be selected from all types of hydrocarbon fuels solids, including coal, biomass, coked catalysts fluidized catalytic cracking (FCC) process or product cokes speak flexicoker process, taken alone or in a mixture.
The hydrocarbon feedstocks are introduced into the gasification reactor RG
in the form of a dispersed solid, generally of average diameter between 10 microns and 5 mm, preferably between 50 microns and 1 mm about.
The efficiency of the CLC chemical loop combustion process in a fluidized bed circulating relies to a large extent on the physico-chemical properties of the active redox mass. The reactivity of the oxidation couple (s) reducers involved as well as the associated oxygen transfer capacity are parameters influencing the design of the RO and RR reactors, on particle circulation speeds. The lifetime of the particles as for it depends on the mechanical strength of the particles as well as their stability chemical. In order to obtain particles that can be used for this process, particles put into play are usually composed of a couple or a set of oxido-reducing pairs selected from CuO / Cu, Cu 2 O / Cu, NiO / Ni, Fe 2 O 3 / Fe 3 O 4, FeO / Fe, Fe3O4 / Fe0, MnO2 / Mn2O3, MnO3 / MnO4, MnO4 / MnO, MnO / Mn, Co304 / CoO, CoO / Co, and a binder providing physico-chemical stability necessary. It is possible to use synthetic or natural ores.
Large particles are more difficult to transport and require speeds important transportation. To limit the transport speeds in lines of transfer and inside the reactors, and thus limit the losses of loads in the process as well as the phenomena of abrasion and erosion, so it is preferable to limit the particle size of carrier material from oxygen to a maximum value close to 500 microns.
Preferably, the oxygen-carrying material introduced into the chemical loop combustion plant therefore has a particle size such as that more than 90% of the particles have a size between 100 and 500 microns.

More preferably, the material introduced into the installation has a particle size such that more than 90% of the particles have a diameter of particles between 150 and 300 microns.
Even more preferably, the material introduced into the installation has a particle size such that more than 95% of the particles have an included diameter between 150 and 300 microns.
The method according to the invention can advantageously be integrated into a refinery.
Example:
In the following example, the main reactor is the reactor of gasification (RG). Figure 3 shows the concentrations (Xeq) of thermodynamic equilibrium gases in the reactor RG. These results illustrate that in the state balance, almost all the injected carbon is converted to CO2. CO concentration is very low at about 600 C, but increases with temperature. This graph as well as the material balance are used to calculate the different contents in gas at the outlet of the RG reactor.
For this purpose, the thermodynamic equilibrium results of 90% of H 2 O and 10% of carbon were simulated with CHEMKINTm software.
A stationary zero-order model has been developed to study the feasibility of this system. The coal is injected into the bed with a flow of kg / h. The properties of the injected coal are shown in Table 1.
gasification was carried out with superheated steam at 1000 C and a mass flow rate of 27 kg / s (equivalent to the stoichiometric flow of air necessary to ensure complete combustion). The properties of synthesis gas at the RG reactor are presented in Table 2. Concentrations are calculated on the thermodynamic basis and the material balance. The temperature of RG reactor outlet is 600 C and the average temperature of the RG reactor is 800 C.

% weight (excluding Components water weight, ash Carbon (C) 64% 72%
Hydrogen (H) 5% 6%
Nitrogen (N) 1% 1%
Total sulfur (S) 1% 1%
Oxygen (0) 18% 20%
Ashes 12%
Table 1: Properties (ultimate analysis) of the coal used for the case study, with LHV = 28 M3 / kg.
Flow Rate Concentration Concentration Components% weight (kg / s) (mol / s) (mol%) (excluding water, mol%) CO2 13.0% 3.95 0.141 8% 28%
H20 81.4% 22.93 1.273 71%
CO 1.8% 0.51 0.018 1% 4%
H2 2.5% 0.70 0.347 19% 68%
CH4 0.0% 0.00 0.000 0% 0%
N2 0.1% 0.03 0.001 0% 0%
SO2 0.2% 0.04 0.0007 0% 0%
Table 2: concentrations of the different gases at the outlet of the reactor RG gasification.
The synthesis gas produced in the gasification reactor RG can be sent all or part of it to the combustion reactor to produce energy.
In the case of synthesis gas production, only part of the gas necessary to maintain the overall energy balance is sent to the RR combustion reactor. In this example, the minimum fraction required to be sent to the combustion reactor is 53%. This system can therefore deliver 47% syngas as product.
In the case of heat production, during combustion, all synthesis is burned in the RR reduction reactor to produce energy.

Claims (9)

1. Integrated gasification process and indirect looping chemical a solid hydrocarbon feedstock in which:
the solid hydrocarbon feedstock (1) is brought into contact with water (2) in a RG gasification reaction zone in order to evacuate ashes (9) and producing a gaseous effluent (3) comprising synthesis gas:
CO, H2 and H2O water;
the reaction reduction zone RR is fed with a chemical loop of oxidation-reduction, in which particles of solid carrier of oxygen Me / MeO, by at least a part of the gaseous effluent (3) produced in the gasification reaction zone to produce a gaseous effluent (4) concentrated in CO2 and H2O, the particles of oxygen-bearing solid obtained from the zone are reoxidized RR reduction reaction of the chemical loop in the zone reaction of oxidation RO by means of an oxidizing gas (6) and evacuated fumes (7). 2. Method according to claim 1 wherein a part (5) is recycled of the effluent concentrated in CO2 and H2O produced in the RR reduction zone for supplying oxygen to the RG gasification reaction zone. 3. Integrated Gasification and Indirect Circulation Loop chemical according to claim 1 or 2 wherein the reaction zone of RR reduction by all the gaseous effluent (3) produced in the zone RG gasification reaction, in order to produce heat that is recovered at the oxidation reaction zone RO or on the lines of transport gaseous effluents. 4. Integrated Gasification and Indirect Circulation Loop chemical according to claim 1 or 2 wherein the reaction zone of RR reduction by a part (3a) of the gaseous effluent produced in the zone RG gasification reaction in sufficient quantity to produce energy necessary for the gasification reaction, the other part (3b) allowing produce CO + H2 synthesis gas. 5. Integrated Gasification and Indirect Circulation Loop chemical according to one of the preceding claims wherein the hydrocarbon feedstock solid is selected from coal, coke catalysts of the process of catalytic cracking in fluidized bed (FCC) or cokes produced by the process flexicoker. 6. Gasification plant and chemical looping combustion comprising:
a reaction gasification zone RG fed with a charge solid hydrocarbon (1) and water (2) and comprising an outlet pipe a gaseous effluent comprising synthesis gas and water (3) and a outlet duct of ash produced (9);
a chemical combustion loop comprising a reaction zone of RR reduction and an oxidation reaction zone RO, said reduction reaction zone RR being fed by at least a part of the gaseous effluent (3) coming from the gasification zone RG and by a transport duct of oxygen-carrying solid particles (MeO) of said oxidation zone RO, and comprising an outlet pipe of an effluent gaseous (4) comprising CO2 and H2O;
and said oxidation reaction zone RO being supplied by a gas oxidant (6) and via a transport pipe of the solid carrier particles reduced oxygen (Me) from the reduction reaction zone, and comprising a transport pipe for evacuating the fumes (7). 7. Installation according to claim 6 comprising a transport pipe a portion (5) of the gaseous effluent comprising CO2 and H2O (4) to feeding the gasification zone RG. 8. Installation according to claim 6 or 7 comprising at least one heat exchanger in the oxidation zone RO (E1) and / or on the conduct of transport of fumes (7) (E2). 9.
Installation according to claim 6 or 7 in which the outlet pipe of the gaseous effluent (3) is divided into two conduits for feeding of the reduction zone RR in synthesis gas for combustion (3a) and the evacuation of the synthesis gas produced (3b).