Process for the preparation of syngas from carbonaceous waste material

Abstract

Process for the production of syngas from carbonaceous waste material and CO2 comprising the following stages: a stage a) comprising the reaction [R1] in which the carbonaceous material is reacted with carbon dioxide to obtain carbon monoxide according to the following reaction scheme: [R1] CO2 + C = 2 CO; a stage b) of producing H2 and adding it to the carbon monoxide obtained in stage a) to obtain syngas, wherein stage b) comprises at least one of the following stages: bl) the carbon monoxide from the previous stage is reacted with water vapour to obtain carbon dioxide and hydrogen according to the following reaction scheme: [R2] CO + H2O = CO2 + H2 b2) producing hydrogen by means of electrolysis of water, which is added to the carbon monoxide from stage a). The invention also relates to the unit in which stages a) and bl) are conducted as well as the related apparatus comprising the aforementioned unit.

Description

[0001] PROCESS FOR THE PREPARATION OF SYNGAS FROM CARBONACEOUS WASTE MATERIAL.

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a process for producing syngas from CO2 and waste carbonaceous material.

[0004] BACKGROUND OF THE INVENTION

[0005] In industrial processes, the reuse of CO2 often involves the use of large amounts of hydrogen or hydrogen-rich molecules, in reactions such as complete hydrogenation, for example the Sabatier reaction or methanation (Che, M., Nobel Prize in chemistry 1912 to Sabatier: Organic chemistry or catalysis? Catalysis Today, 218-219, 162-171, 2013) to obtain methane, the dry reforming reaction (Vita et al., Methanol synthesis from biogas: A thermodynamic analysis, Renewable Energy, 118, 673-684, 2018), to obtain intermediate syngas for the synthesis of high value-added chemicals such as methanol, dimethyl ether or reactions with hydrogen sulphide (Manenti, CO2 as feedstock: A new pathway to syngas, Computer Aided Chemical Engineering, 37, 1049-1054, 2015).

[0006] It is also well known that one of the problems with respect to the circular economy concerns the reuse of carbonaceous material such as that contained in rubber dust, coke, residual biomass and that obtained in processing waste.

[0007] SUMMARY OF THE INVENTION

[0008] The applicant has now found a process for the production of syngas, which uses CO2 as a starting material, which does not require large amounts of hydrogen and which moreover uses waste carbonaceous material, without resorting to large amounts of hydrogen.

[0009] This process, which forms the object of the present invention, comprises the following stages:

[0010] - a stage a) comprising the reaction [Rl] in which the carbonaceous material is reacted with carbon dioxide to obtain carbon monoxide according to the following reaction scheme:

[0011] [Rl] CO2 + C = 2 CO;

[0012] - a stage b) of producing hydrogen and adding it to the carbon monoxide obtained in stage a) to obtain syngas, characterized in that stage b) comprises at least one of the following stages: bl) the carbon monoxide from the previous stage is reacted with water vapour to obtain carbon dioxide and hydrogen according to the following reaction scheme:

[0013] [R2] CO + H2O = CO2 + H2 b2) producing hydrogen by electrolysis of water, which is added to the carbon monoxide from stage a). A further object of the present invention is the unit in which stages a) and bl) are carried out, as well as the relative apparatus comprising the aforementioned unit.

[0014] DESCRIPTION OF THE FIGURES

[0015] Figure 1 shows a preferred schematic configuration of the apparatus 1 according to the present invention, for conducting stages a) and bl) of the process of the invention both in the presence and in the absence of oxygen, when the carbonaceous material is a solid.

[0016] Figure 2B shows the process carried out in the unit 1.1 of figure 1, when stage a) is conducted in the presence of oxygen and in which the lower section A and the upper section B are divided into different zones, depending on what happens within them.

[0017] Figure 2A instead shows the graphs of the heights as a function of the temperatures of the gases and the carbonaceous solid material in vessel 1.1, of the process carried out as shown in figure 2B.

[0018] Figure 3 shows the block diagram of a preferred embodiment of the process of the invention.

[0019] Figure 4B shows the process of the invention, when carried out in unit 1.1 of figure 1, in the case in which stage a) is carried out in the absence of oxygen and in which the lower section A and the upper section B are divided into different zones, depending on what takes place inside them.

[0020] Figure 4A shows the graphs of the heights of gases and carbonaceous solid material as a function of temperatures in unit 1.1, when carried out as shown in figure 4B.

[0021] Figure 5 shows a block diagram of a preferred embodiment of the process of the invention.

[0022] Figure 6 shows a block diagram of the process of the invention.

[0023] Figure 7 shows a block diagram of a preferred embodiment of the process of the invention.

[0024] Figure 8 shows a block diagram of a preferred embodiment of the process of the invention. Figure 9 shows a block diagram of an embodiment of the process of the invention.

[0025] Figures 10 A and 10 B show two block diagrams of two preferred embodiments of the process of the invention.

[0026] DETAILED DESCRIPTION OF THE INVENTION

[0027] For the purposes of the present invention, the term "comprising" does not exclude the possibility that the process and the apparatus according to the present invention may comprise several stages or several components respectively not listed after said definition.

[0028] The terms "consist" or "consist of' exclude this possibility.

[0029] For the purposes of the present invention, residue or waste carbonaceous material means a waste material containing considerable amounts of carbon in the elemental or bound state, preferably >30%, preferably greater than 50% and even more preferably greater than 80%, such as for example: rubber dust, coke, residual biomass, organic material processing waste. Carbon in the elemental state means carbon also covalently bound with heteroatoms other than carbon, such as for example H, O, P, S, N etc.

[0030] Non-volatilised carbonaceous material means material which does not react with the CO2 in [Rl], comprising ash as the main component and having an elemental carbon content of less than 30%, preferably less than 20% even more preferably less than 10%.

[0031] Biot number (Bi) means:

[0032] • h is the coefficient of thermal exchange with the outside (W / m2 / K);

[0033] • L is the characteristic length, usually chosen equal to the equivalent diameter of the solid (m);

[0034] • A the thermal conductivity of the solid.

[0035] Equivalent diameter means the diameter of a hypothetical spherical particle that has the same geometric, optical, electrical or aerodynamic behavior as a real non-spherical particle.

[0036] For the purposes of the present invention in syngas, S and SN refer to:

[0037] S = H2 / CO

[0038] SN = (H2 - CO2) / (CO + CO2).

[0039] The reaction [Rl] is better known as the Boudouard inverse reaction.

[0040] The reaction [R2] is better known as the Fontana reaction or the Water Gas shift Reaction.

[0041] The process of the invention when it provides that stage b) comprises stage bl) is also identified in the present invention with the acronym RBF (Reverse Boudouard Fontana).

[0042] The electrolyser used in stage b2) is preferably a solid oxide electrolyser also indicated by the acronym SOEC (solid oxide electrolytic cell). However, other electrolysers may also be used, for example polymeric electrolysers or low temperature electrolysers.

[0043] The definition of an autothermal process is a process that is self-sustaining from an energy point of view, with the exception of the start-up phase.

[0044] This occurs when in the process of the invention, the stage a) is carried out in the presence of oxygen or oxygen-containing mixture.

[0045] The temperature at which the reaction [Rl] is conducted is at least 600°C, preferably at least 700°C, more preferably at least 800°C, under optimum conditions at least 900°C.

[0046] The reaction temperature [R2] is equal to or less than the temperature of [Rl], preferably not less than 620°C, more preferably not less than 650°C. The temperature of the stage bl) is between 100°C and 900°C [Rl], preferably between 500°C and 900°C and more preferably between 700°C and 900°C, with the optimal condition at 828°C (Hillestad et al., 2018, Improving carbon efficiency and profitability of the biomass to liquid process with hydrogen from renewable power, Fuel, 234, 1431-1451).

[0047] The process of the invention is preferably conducted at a pressure of 1 to 200 bar, preferably 1 to 100 bar and more preferably 20 to 100 bar, and using vapour or water at similar pressure conditions.

[0048] In the process according to the present invention stage a) may be carried out in the presence or absence of oxygen.

[0049] When in the process according to the present invention stage a) is conducted in the presence of oxygen, the process as a whole is autothermal, since especially in the RBF process it exploits the enthalpy of the effluents exiting the reaction [Rl], to ensure the autothermicity of the electrolyser and of the reaction R2, with considerable energy advantage.

[0050] Sometimes, in the process according to the present invention, when stage a) is conducted in the presence of oxygen and operates at temperatures above 700°C, preferably above 800°C, it is not necessary to add in full the amount of CO2 required, because in stage a) CO2 is formed by oxidation according to the reaction:

[0051] [R4] C+ 02 = CO2

[0052] The process can be carried out in endothermic mode, and this occurs when in the process of the invention stage a) is carried out in the absence of oxygen, in this case an external source of CO2 suitably heated is always used, for example electrically, by solar concentration or simply exploiting its high temperature when leaving ovens or furnaces.

[0053] When in the process according to the present invention stage b) comprises or consists of stage bl), it is preferably carried out in the further apparatus that is the object of the present invention and of which a preferred embodiment is shown in figure 1.

[0054] In particular, the apparatus 1 comprises a unit consisting of a closed vessel of substantially cylindrical shape 1.1, formed by an upper section B and a lower section A separated from each other by a dust collector 1.3, wherein: the upper section B in which stage bl) of the process of the invention is conducted comprises:

[0055] • A fixed catalytic bed 1.4,

[0056] An outlet 1.10 for the gases arranged laterally above the catalytic bed 1.2 a water inlet 1.11 arranged laterally and a water spreader 1.12 arranged inside this upper section B parallel to and above said dust collector 1.3, on top of said upper section B an inlet 1.13 is used to load the fresh catalyst and on the side, an outlet 1.14 arranged laterally in said upper section B to allow the removal of the spent catalyst; the lower section (A), in which instead stage a) of the process according to the present invention takes place, comprises a

[0057] • device for introducing the fresh carbonaceous residue material 1.7,

[0058] • a bed 1.5 of non-volatilised carbonaceous residue material;

[0059] • a grid or perforated plate 1.6 to separate said non-volatilised carbonaceous residue material and to allow its removal by means of a hopper 1.16, arranged under said grid or perforated plate and connected to an outlet 1.15 arranged at the bottom of said lower section A.

[0060] • an inlet 1.17 for the CO2 gas and possibly 02 gas arranged under the grid 1.6.

[0061] The apparatus 1 according to the present invention further comprises:

[0062] - a fan 8 directly connected to a heating unit 9 which in turn is directly connected to the inlet 1.17 of the reactant gases (CO2 and possibly oxygen), located at the bottom side of the lower section A of the vessel 1.1.

[0063] In the preferred embodiment shown in figure 1, the fresh carbonaceous material used as a reagent is solid, consequently the device for loading it into the lower section of the vessel is the auger 1.7, preferably facing upwards to avoid problems of premature degradation caused by the hot fumes coming from below.

[0064] When, on the other hand, the fresh carbonaceous residue material has a pasty or fluid consistency, a slurry pump and a loading line are used to load it inside the container and a spreader or a sprayer are used to distribute it inside the section below A.

[0065] When the process is carried out in the apparatus 1, stage a) is carried out in the presence of oxygen, in autothermal mode and using fresh solid carbonaceous material, the process includes the following operating stages.

[0066] In the lower section A the fresh solid carbonaceous material is fed into the head of the lower section by means of the auger 1.7 and progressively descends downwards, coming into contact with the hot gases that rise up said lower section A under different thermal conditions exchanging heat and mass so that in the uppermost section of the lower section any moisture present in the fresh solid carbonaceous material is eventually removed, in the section below the dry carbonaceous material heats up further and quickly encountering the increasingly hot gases and in this zone the reaction [Rl] takes place, where the hot gas comprising CO2 completely or partially volatilises the carbonaceous material transforming it completely or partially into CO and transforming into CO itself, in the final section of the lower zone the non-volatilised and carbonaceous residue material undergoes a thermal inversion towards the gas being hotter internally than externally due to a high Biot number, heats the gas, and deposits on the grid 1.6. In section A the carbon dioxide together with the oxygen are blown into the fan 8 and preheated in the heating unit 9, in this case this heating unit is used only for starting the apparatus (1). The gases supplied from below through the opening (1.17) enter the vessel 1.1 in the lower section (A), they rise upwards meeting the carbonaceous hot solid material countercurrently and are further heated to the temperature necessary to activate the exothermic oxidation reaction: [R3] C+ 0.5 02 = CO, where CO2 was not supplied, but was generated in situ within the lower section A, the reaction [R3] is combined with the exothermic oxidation reaction:

[0067] [R4] C+ 02 = CO2

[0068] The exothermic reaction [R3] possibly associated with the reaction [R4] is able to heat the gases to a temperature higher than that of the solid particles, until the oxygen is completely consumed and reaches a sufficiently high temperature, at least 500°C, more preferably at least 600°C, even more preferably 700°C to allow the endothermic reaction [Rl] to take place, subsequently the gas slowly begins to cool by transferring heat to the carbonaceous fresh material entering the head of the lower section B.

[0069] The gases exiting from the lower section A pass through the dust collector 1.3 and, once filtered, enter the upper zone B, where the reaction [R2] takes place in which hydrogen is produced and in part the carbon monoxide is reformed to CO2 so that the temperature of the effluents exiting is not lower than 620°C, so that the reaction is suitably shifted to the right or allows part of the CO2 to be reformed from CO generating as much hydrogen in the stoichiometry of [R2], The catalyst used in section B is selected from those of conventional type such as iron, chromium or other transition metals.

[0070] Figure 2B is a schematic representation of the process described above as it takes place in the unit 1.1 of the apparatus 1 when stage a) is carried out in the presence of oxygen. For this reason, the lower zone A and the upper zone B are divided into different zones, depending on what takes place within them. In particular, 1.4 indicates the zone where the reduction of carbon dioxide takes place in the lower zone A of the container 1.1.

[0071] In this zone 1.4, different zones can be distinguished starting from the bottom upwards, the first zone in which the cooling solid gives up heat and is indicated as SOLID COOLING, GAS PREHEATING. In the zone above indicated in the figure as OXIDATION, the exothermic oxidation reactions [R3] and [R4] take place, which develop heat by raising the temperature of the gases to temperatures such as to activate the endothermic Boudouard inverse reaction in the zone above indicated as [Rl] REVERSE BOUDUARD. In the zone indicated as SOLID PREHEATING, GAS COOLING above the zone where the reaction [Rl] takes place, the gases cool by transferring heat and preheating the fresh solid carbonaceous material that is introduced into this zone.

[0072] Figure 2A shows, in the form of a qualitative graph, the heights in vessel 1.1, in metres, of gases and carbonaceous solid material as a function of temperature in °C, when the system is operated with the process described above. Starting from the bottom, it is highlighted how the solid particles favor the increase of the temperature of the gases introduced from the bottom by direct contact of the solid-gas phases. Once an appropriate ignition temperature has been reached, typically at a distance of one metre from the bottom of the unit, the oxygen is activated and begins to oxidise part of the solid and part of the thermally volatilised substances, allowing the gas to exceed the solid in temperature as the apparatus rises. The peak temperature (hot-spot) is obtained from the gas at the complete depletion of oxygen in the ascent path of the unit. By further raising the unit from the peak temperature, the gas progressively heats the solid, progressively losing heat and decreasing its temperature until it reaches the optimal conditions to move to the upper zone.

[0073] In the new zone, it is possible to supply water (by means of atomisers) or vapour in order to correct, where necessary, the temperature to reach the optimal conditions of the reaction [R2] which takes place in substantial thermal equilibrium or in mild exo / endo-thermal conditions depending on the selected temperature. The dashed part indicates the temperature of the gases in section B of the vessel if they come into contact with a spray of water or water vapour at a temperature lower than that of the catalytic bed 1.2 where the Fontana reaction takes place. Under the preferred conditions the reaction [R2] is carried out at around 620-650°C and takes place under weakly exothermic conditions.

[0074] However, in a particular implementation mode, it is possible to supply the overlying zone with only a portion of the stream coming from the underlying zone and bypass the rest to the outside, in order to push the reaction [R2] to its maximum potential up to low temperatures, even equal to 200-250°C. The bypass and exhaust currents from the head of the unit can then be mixed outside.

[0075] The process that is the object of the present invention, wherein stage a) is carried out in the presence of oxygen using carbonaceous residue material with a pasty consistency, can be carried out in the apparatus 1. In this case the fresh carbonaceous material is distributed inside the lower section A by means of a slurry pump and by means of a loading line sent into a spreader that sprays it from top to bottom. These droplets meet the gases, which rise up said lower section A under different thermal conditions, exchanging heat and mass so that in the upper section of the lower section any moisture present in the fresh carbonaceous solid material is eventually removed, in the underlying section the dry carbonaceous material heats up further and quickly meeting the increasingly hot gases and in this zone the reaction R1 takes place, where the hot gas comprising CO2 completely or partially volatilises the carbonaceous material transforming it completely or partially into CO and transforming into CO itself, in the final section of the lower zone the non-volatilised and carbonaceous residue material undergoes a thermal inversion, cooling by heating the gas, and deposits on the grid 1.5.

[0076] In this case also, with regard to the gas phase, in the section below A the carbon dioxide together with the oxygen blown into the fan 8 and preheated in the heating unit 9, in this case used only for starting the apparatus 1, are supplied from below through the opening 1.17 inside the lower section A, they rise meeting the hot solid material countercurrently and are heated to a temperature to activate the exothermic oxidation reaction: [R3] C+ 0.5 02 = CO, where CO2 was not supplied, but was generated in situ within the lower section (B), the reaction [R3] is combined with the exothermic oxidation reaction:

[0077] [R4] C+ 02 = CO2

[0078] In this case the exothermic reaction [R3] possibly associated with the reaction [R4] is also able to heat the gases to a temperature higher than that of the solid particles, until the oxygen is completely consumed and reaches a sufficiently high temperature, preferably at least 500°C, more preferably at least 600°C, even more preferably 700°C to allow the endothermic reaction [Rl] to take place, subsequently the gas slowly begins to cool by transferring heat to the carbonaceous fresh material entering the head of the lower section A.

[0079] The gas exiting from the lower section A passes through the dust collector 1.3 and thus filtered enters the upper zone B where the reaction [R2] takes place in which hydrogen is produced and the carbon monoxide is in part reformed to CO2, so that the temperature of the effluents exiting is not lower than 620°C, so that the reaction is appropriately shifted to the right.

[0080] According to a further embodiment of the process of the invention carried out in the apparatus 1, it may provide for the case wherein the carbonaceous material in the form of droplets or spray can move in equicurrent according to techniques well known to the person skilled in the operation of spray dryers (Di Pretoro, Manenti, 2020). In this case, the gas progressively cools, providing heat to the droplets, while the droplets themselves maintain their constant temperature, equal to the evaporation temperature of the liquid, until evaporation is complete. The solid dried of its solvent behaves as described for the solids feedstock, volatilising and heating according to its own chemical-physical characteristics (Biot number).

[0081] The RBF process, when carried out in endothermic mode or when stage a) is carried out in the absence of oxygen with fresh solid carbonaceous material and is carried out in the apparatus 1 comprises the following operating modes. In the lower section A the fresh solid carbonaceous material is fed into the head of the lower section A by means of the auger 7 and progressively descends downwards, coming into contact with the hot gases that rise up said lower section (A) under different thermal conditions exchanging heat and mass so that in the uppermost section of the lower section any moisture possibly present in the fresh solid carbonaceous material is removed, in the section below the dry carbonaceous material is rapidly further heated encountering the increasingly hot gases and in this zone the reaction [Rl] takes place, where the hot gas comprising CO2 completely or partially volatilises the carbonaceous material transforming it completely or partially into CO and transforming into CO itself, in the final section of the lower zone the non-volatilised carbonaceous material undergoes a thermal inversion towards the gas being hotter internally than externally due to the high Biot number, heats the gas, and deposits on the grid (6) as carbonaceous residue material.

[0082] In the lower section A, the CO2 is externally heated by the heating unit 9 until it reaches temperatures not lower than 650°C, preferably equal to at least 700°C, more preferably higher than 800°C, even more preferably higher than 900°C, before coming into contact with the carbonaceous fresh material. From the first contact with the solid, the gas begins to cool in a monotonous manner, transferring heat to the fresh carbonaceous material.

[0083] The gas exiting from the lower section A passes through the dust collector 1.3 and thus filtered enters the upper zone B where the reaction [R2] takes place in which hydrogen is produced and in part the carbon monoxide is reformed to CO2, so that the temperature of the effluents exiting is not lower than 620°C.

[0084] Figure 4B represents a schematic figure of the vessel 1.1 of figure 1, when stage a) is carried out in the absence of oxygen and in which the lower zone A and the upper zone B are divided into different zones, depending on what takes place inside them.

[0085] In the same figure, the zone indicated with 1.4 in the lower section A of the container 1.1 is also divided into the respective zones of reverse Boudouard and solid preheating. In both cases, the CO2, already hot, cools by transferring heat to the solid to carry out the reaction [Rl] in the lower part and to preheat the fresh solid exiting the auger 1.7 in the upper part. The nonvolatilised residue is deposited on the grid 1.6. Figure 4A shows in the form of a graph the heights in the unit 1.1 of the gases in m and of the carbonaceous solid material as a function of temperature in °C. Starting from the bottom, it is noted that the CO2 stream has a continuously decreasing temperature due to the endothermicity of the reaction [Rl] and the thermal exchange between the hot CO2 and the cooler solid. On the contrary, the solid that descends progressively into the unit heats up, gradually encountering hotter gases and volatilising with progressive rapidity. Also in this case, the dashed part indicates the temperature of the gases in section B of the vessel if they come into contact with a spray of water or water vapour at a lower temperature than that of the catalytic bed 1.2 where the Fontana reaction takes place.

[0086] The RBF process, in other words the process of the invention, when it also includes stage bl) can provide that the CO2 not reacted in stage a) and therefore in reaction [Rl] and that formed in reaction [R2] can be removed with conventional techniques both at the end of reaction [Rl] and at the end of reaction [R2], or only at the end of reaction [R2] and recycled to stage a) upstream of the reaction [Rl].

[0087] This is also the case when the process is carried out in the apparatus 1 and in the unit 1.1.

[0088] In fact, where required, the gas can leave the unit 1.1, undergo not only purification, but also thermal treatments, and return to the unit.

[0089] This type of process is shown in a preferred form in figure 3.

[0090] Conventional separation techniques are, for example, those of absorption with amines, softening, scrubber, water column, pressure swing adsorption, etc.

[0091] In the embodiment of the process of the invention described in figure 3, it is conducted in autothermal mode therefore in the presence of oxygen in stage a). In the reaction [Rl] the hot CO2 volatilises the carbonaceous material and partially oxidizes it to CO according to the reaction [Rl] and the CO2 is reduced by an equal number of moles according to the same reaction [Rl], The hot gas stream leaving the reaction zone [Rl] and containing CO and CO2 is purified from CO2 by the above conventional techniques. The CO2 removed is recycled upstream in stage a), the CO purified in stage bl) is reacted with water or vapour according to reaction [R2] generating H2 and CO2, the latter is separated from the syngas with conventional techniques and recycled upstream of stage a).

[0092] In figure 3 it is also envisaged that the last stage of purification makes it possible also to remove the water formed in the reaction [R2],

[0093] According to a preferred embodiment of the RBF process conducted in the absence of oxygen when the reaction [Rl] in stage a) is conducted at temperatures greater than or equal to 900°C, the stream exiting stage a) is low in CO2 or CO2-free, in this case, CO2 removal is conducted only on the gases exiting the reaction [R2],

[0094] In figure 5, it is also envisaged that in this purification stage the water is also removed from the reaction products, and recycled in stage bl) upstream of the reaction [R2], The process of the invention may include both stage bl) and stage b2).

[0095] The Fontana reaction [R2] is generally conducted under mild conditions to avoid excessively increasing the CO2 content in the final syngas mixture. This implies that the RBF process obtains a syngas with low S and SN values that are not optimal for the main syntheses of high value-added chemicals, such as methanol, dimethyl ether (Bozzano, G., Manenti, F., Efficient methanol synthesis: Perspectives, technologies and optimization strategies, Progress in Energy and Combustion Science, 2016, 56, pp. 71-105).

[0096] Stage b2) of water electrolysis makes it possible to adjust the ratios of S and SN higher and to even reach values of SN and S = 2.

[0097] Therefore, the object of the present invention is a process in which in addition to stage bl), stage b2) is carried out whereby water vapour is also fed to an electrolyser where pure oxygen and hydrogen are generated, hydrogen and unreacted water are added to the gases exiting the reaction [R2],

[0098] A preferred embodiment of such a process is shown in figure 6, wherein stage a) is carried out in the absence of oxygen. The hot CO2 in reaction [Rl] is reduced to CO and the effluents leaving stage a) after the addition of hydrogen from the water electrolysis, after any removal of unreacted water vapour, are preferably subjected to a purification stage, in which the CO2 is removed, which is sent to stage a). In this purification stage the water formed in the reaction [R2] is also preferably removed.

[0099] The process of the invention may involve the case where stage b) consists only of stage b2).

[0100] This category also includes the process according to the present invention as described in figure 7, wherein stage a) is carried out in the absence of oxygen and in the reaction [Rl], the hot CO2 is reduced to CO by volatilising and oxidizing the portion of carbon present in the solid and / or liquid residue. The conversion takes place with partial or total reduction of CO2. At the exit of reaction [Rl], the CO stream is mixed with hydrogen from an electrolyser until the optimum S ratio is reached. The downstream purification stage is useful to remove residual or excess CO2 depending on the uses of the syngas. The CO2 is recirculated to stage a).

[0101] Also in this case, preferably, the unreacted water is also removed in the electrolyser, which is recirculated before the electrolyser, therefore upstream of stage b2).

[0102] Another embodiment of the process of the invention is described in figure 8 in which stage b) coincides with only stage b2) which is carried out in an autothermal manner.

[0103] The pure oxygen produced in the electrolyser is supplied at stage a) for thermal self- sustainment. The CO2 and the carbonaceous residue react according to the reverse Boudouard reaction [Rl], The effluent leaving stage a) is directly mixed with the hydrogen from the electrolyser of stage b2). The obtained gas mixture is sent to purification for removal of CO2 which is recycled to stage a) and water which is recycled to the electrolyser. The amounts of oxygen and hydrogen produced by the electrolyser are not stoichiometrically suitable for the aforementioned uses. To obtain the amount of hydrogen such as to completely reduce CO and CO2 leaking from the unit, given the stoichiometry of the electrolysis reaction, an amount of oxygen higher than that required by the unit itself in the devolatilisation section is obtained to support itself thermally. In other words, the nature of the invention leads to an overproduction of oxygen if all the hydrogen required for the complete transformation of the gaseous effluents into chemicals were to be produced by electrolysis given the stoichiometry of the electrolysis reaction itself. Figure 9 shows another form of implementation of the process similar to that provided in figure 8 which only provides for stage b2) in autothermal mode. Also in this case, the oxygen produced in the electrolyser is sent to stage a). However, this process differs from that shown in figure 8, in that it does not provide for the purification stage and therefore not even the recycling of CO2 or even water to the electrolyser to stage a). Figure 10a shows a preferred embodiment in which stage b) coincides with only stage b2) in which oxygen is recycled to stage a) and which instead only provides for the elimination of water from the hydrogen produced in stage b2) before it is mixed with the effluents from reaction [R1 ] . The removed water is recycled upstream of the electrolyser.

[0104] Figure 10b describes a process identical to that shown in figure 10A, with the only difference that in this case in stage a) only the carbonaceous material is supplied; therefore, without the CO2 that is formed in situ according to the [R4] reaction with oxygen at elevated temperatures.

Claims

CLAIMS1. Process for the production of syngas from carbonaceous residue material comprising the following stages:- a stage a) comprising the reaction [Rl] in which the carbonaceous material is reacted with carbon dioxide to obtain carbon monoxide according to the following reaction scheme:[Rl] CO2+ C = 2 CO;- a stage b) of producing hydrogen and adding it to the carbon monoxide obtained in stage a) to obtain syngas, wherein stage b) comprises at least one of the following stages: bl) the carbon monoxide from the previous stage is reacted with water vapour to obtain carbon dioxide and hydrogen according to the following reaction scheme:[R2] CO + H2O = CO2 + H2b2) producing hydrogen by electrolysis of water, which is added to the carbon monoxide from stage a).

2. Process according to Claim 1, wherein the temperature at which the reaction [Rl] is conducted is preferably at least 600°C, at least 700°C, preferably at least 800°C, preferably at least 900°C.

3. Process according to Claim 1 or 2, wherein the temperature of the reaction [R2] is preferably not lower than 620°C, preferably not lower than 650°C.

4. Process according to any one of Claims 1-3, wherein the temperature of stage b2) ranges from 100 to 900°C, preferably from 500 to 900°C, more preferably from 800 to 900°C.

5. Process according to any one of Claims 1-4 conducted at a pressure between 1 and 200 bar, preferably between 1 to 100 bar and more preferably from 20 to 100 bar and encompasses the use of steam or water at analogous pressure conditions.

6. Process according to any one of Claims 1 to 5 wherein stage a) is conducted in the presence of oxygen or in the absence of oxygen.

7. Process according to Claim 6, conducted in the presence of oxygen and in stage a) the CO2 employed in the reaction [Rl] is formed in situ according to the reaction:[R4] C+ O2= CO2 whereby in stage a) carbonaceous material is supplied in the absence of CO2.

8. Process according to Claim 6, conducted in the absence of oxygen and in stage a) an external carbon dioxide source is employed.

9. Process according to any one of Claims 1-8, wherein stage b) comprises or consists of stage bl).

10. Apparatus (1) comprising:- a unit (1.1) consisting of a substantially cylindrical closed container, comprising an upper section (B) and a lower section (A) separated from each other by a dust remover (1.3), wherein: the upper section (B) comprises:A fixed catalytic bed (1.4),An outlet (1.10) for the gases arranged laterally above the catalytic bed (2) a water inlet (1.11) arranged laterally and a water spreader (1.12) arranged inside this upper section (B) parallel to and above said dust remover (1.3), at the top of said upper section (B) an inlet (1.13) for loading the fresh catalyst and at the side portion, an outlet (1.14) arranged laterally in said upper section to allow the removal of the spent catalyst; the lower section (A) comprises• a device for introducing the carbonaceous fresh material (1.7),• a bed (1.5) of non-volatilized carbonaceous residue material;• a grid or perforated plate (1.6) to separate said non-volatilized carbonaceous residue material and to allow its removal by means of a hopper (1.16), arranged under said grid or perforated plate and connected to an outlet (1.15) arranged at the bottom of said lower section (B);• an inlet (1.17) for the reagent gases (CO2 and possibly 02) arranged under the grid or perforated plate (1.6);- a fan (8) directly connected with a heating unit (9) in turn connected with the inlet (1.17) for the reagent gas(es) arranged at the bottom in the lower section (A) of the unit (1.1).

11. Apparatus according to Claim 10, wherein when the carbonaceous fresh material is solid, the device (1.7) for distributing it is an auger, while, when the carbonaceous fresh material hasa fluid consistency, a slurry pump connected to a load line is used and the carbonaceous material is distributed inside the lower section (A) by means of a spreader or sprayer.

12. Process according to Claim 9, wherein stage a) is conducted in the presence of oxygen in the apparatus according to Claim 10 or 11, comprising the following operational stages:1-lower section (A)1.1 Solid carbonaceous material when the solid carbonaceous fresh material is fed to the head of the lower section (A) through the auger (1.7) and descends progressively downwards, coming into contact with the gases that ascend said lower section (A) at different thermal conditions exchanging heat and mass so that in the highest section of the lower section any moisture present in the solid carbonaceous fresh material is eventually removed, in the section below the carbonaceous dry material is rapidly further heated and encounters the increasingly hot gases and in this zone the [Rl] reaction takes place, where the hot gas comprising CO2 completely or partially volatilizes the carbonaceous material transforming it completely or partially into CO and transforming itself into CO, in the final section of the lower zone the non-volatilized carbonaceous residue material undergoes a thermal inversion in comparison with the gas, said carbonaceous material being hotter internally than externally, heats the gas, and is deposited on the grid 1.5.1.2 gaseous material the carbon dioxide together with the oxygen blown into the fan (8) and preheated in the heating unit (9) in this case used only for starting up the apparatus (1), are supplied from below through the opening (1.17) inside the lower section (A), they ascend meeting the hot solid material countercurrently and are heated to a temperature to activate the exothermic oxidation reaction: [R3] C+ 0.5 O2= CO, when CO2 is not supplied, but is generated in situ within the lower section (B), the reaction [R3] is combined with the exothermic oxidation reaction:[R4] C+ O2= CO2said exothermic reaction [R3] possibly associated with the reaction [R4] being able to heat the gases to a temperature higher than that of the solid particles, until the oxygen is completely consumed and to reach a sufficiently high temperature, at least 600°C, preferably 700°C, more preferably 800°C, even more preferably to 900°C to allow the endothermic reaction [Rl] to take place, subsequently the gas begins to cool by transferring heat to the carbonaceous fresh material entering the head of the lower section (B);2-upper section (B)the gases exiting from the lower section (A) pass through the dust remover (1.3) and thus filtered enter the upper zone (B) where the reaction [R2] takes place in which hydrogen is produced and CO2 is partially reformed, so that the temperature of the effluents exiting is not lower than 620°C, preferably 650°C.

13. Process according to Claim 9, conducted in the presence of oxygen in the apparatus according to Claim 10 or 11, comprising the following stages:

1. lower section (A)1.1 carbonaceous material in paste-like form when the carbonaceous fresh material has a paste-like consistency, it enters the lower zone (A) by means of the slurry pump and a loading line and is distributed by means of a spreader that sprays said material in the form of sprays or droplets from above and descends progressively downwards, coming into contact with the hot gases that ascend said lower section (A) under different thermal conditions, exchanging heat and mass so that in the upper section of the lower section any moisture present in the paste-like carbonaceous fresh material is eventually removed, in the underlying section the carbonaceous dry material is further heated and quickly encounters the increasingly hot gases and in this zone the [Rl] reaction takes place, where the hot gas comprising CO2 completely or partially volatilizes the carbonaceous material transforming it completely or partially into CO and reducing the CO2 of the gas to CO, in the final section of the lower zone, the non-volatilized carbonaceous material undergoes a thermal inversion against the gas, being hotter internally than externally, heating the gas, and being deposited on the grid (5) as residue material comprising ash,1.2 gaseous material the carbon dioxide together with the oxygen blown into the fan (7) and preheated in the heating unit (8) used only to start the apparatus (1), are supplied from below to the inside by means of the inlet (1.17), ascend the lower section meeting the hot carbonaceous material in a paste-like form countercurrently and are heated until the exothermic oxidation reaction is activated: [R3] C+ 0.5 O2= CO, when CO2 is not preheated and supplied but is instead generated in situ within the lower section (B), the reaction R3 is combined with the exothermic oxidation reaction:[R4] C+ O2= CO2 said exothermic reaction [R3] possibly associated with the reaction [R4] being able to heat the gases to a temperature higher than that of the particles in paste-like form, until the oxygen is completely consumed and reaches a sufficiently high temperature, at least 600°C, preferably at least 700°C, more preferably at least 800°C, even more preferably 900°C to allow theendothermic reaction [Rl] to take place, subsequently the gas slowly begins to cool by transferring heat to the carbonaceous fresh material entering the head of the lower section (A);2-Upper section (B) the gas exiting from the lower section (A) passes through the dust remover (1.3) and thus filtered enters the upper zone (B) where the reaction [R2] takes place in which hydrogen is produced and CO2 is partly reformed, so that the temperature of the effluents exiting is not lower than 620°C, preferably 650°C.

14. Process according to Claim 9, conducted in the apparatus according to Claim 10 or 11, in the absence of oxygen, comprising the following steps:1- lower section (A)1.1- Solid carbonaceous material when the carbonaceous fresh material is solid, it is fed at the head to the lower section (A) through the auger (7) and progressively descends downwards, coming into contact with the hot gases that ascend said lower section (A) under different thermal conditions, exchanging heat and mass so that in the upper section of the lower section any moisture present in the solid carbonaceous fresh material is eventually removed, in the section below the carbonaceous dry material is rapidly further heated encountering the increasingly hot gases and in this zone the reaction [Rl] takes place, where the hot gas comprising CO2 completely or partially volatilizes the carbonaceous material transforming it completely or partially into CO and the CO2 present in the CO gas, in the lower section of the lower zone the not completely volatilized carbonaceous material undergoes a thermal inversion in comparison with the gas, said carbonaceous material being hotter internally than externally (high Biot number), heats the gas, and deposits on the grid (6) as non-volatilized residue material ,1.2 - gaseous material the CO2 is externally heated by the heating unit (9) until it reaches temperatures not lower than 650°C, preferably equal to at least 700°C, more preferably higher than 800°C, even more preferably higher than 900°C, before coming into contact with the carbonaceous fresh material, subsequently in the upper part of the lower section the gas begins to cool by transferring heat to the carbonaceous fresh material;2-upper section (B) the gas exiting from the lower section (A) passes through the dust eliminator (3) and thus filtered enters the upper zone (B) where the reaction [R2] takes place in which hydrogen is produced and in part the carbon monoxide is reformed to CO2, so that the temperature of the effluents exiting is not lower than 620°C, preferably 650°C.

15. Process according to any one of Claims 9, 12-13 conducted in the presence of oxygen wherein in stage a) the hot CO2 volatilizes the carbonaceous material and partially oxidizes it to CO according to the reaction [Rl] and the CO2 is reduced by an equal number of moles according to the same reaction [Rl], the hot gas stream leaving the reaction zone [Rl] and containing CO and CO2 is purified from the CO2 by conventional techniques, the CO2 thus separated is recycled upstream in stage a), the purified CO is reacted with water or steam according to the reaction [R2] generating H2 and CO2, which is separated from the syngas by conventional techniques and recycled upstream of stage a).

16. Process according to any one of Claims 9, or 14, wherein when stage a) is conducted in the absence of oxygen and the reaction [Rl] is conducted at temperatures greater than or equal to 900°C, the stream exiting stage a) is CO2 poor or CO2-free, in this case, CO2 removal is conducted only on the gases exiting the reaction [R2],17. Process according to any one of Claims 1-9, 12-16 wherein stage b) comprises or consists of stage bl) and b2).

18. Process Claim 17, wherein stage a) is conducted in the absence of oxygen and, to increase S and SN in the syngas, stage b2) is carried out whereby steam is also fed to an electrolyser where pure oxygen and hydrogen are generated, the hydrogen, from which the unreacted steam has possibly been removed, is added to the gases leaving the reaction [R2] and sent for purification, to remove the CO2 that is recycled to stage a) before the reaction [Rl] takes place.19.Process according to any one of Claims 1-8, wherein stage b) comprises or consists of stage b2).20.Process according to Claim 19, wherein stage a) is conducted in the absence of oxygen and in the reaction [Rl], the hot CO2 is reduced to CO by volatilizing and oxidizing the carbon portion present in the solid and / or liquid residue, while the CO2 is partially or completely reduced.

21. Process according to Claim 19, wherein oxygen formed in the electrolysis of water is supplied to stage a) and hydrogen possibly purified from water is added downstream of the reaction [Rl].

22. Process according to Claim 20 or 21 wherein the gas mixture exiting the reaction [Rl] and added with hydrogen from the electrolysis is subjected to purification, removing the CO2 that is recycled to stage a).

23. Process according to Claims 21 and 22, wherein in stage a) only carbonaceous material is supplied and the CO2 employed reaction [Rl] is formed in situ according to the reaction [R4] C+ O2= CO2