Methanation process and reactor for reacting hydrogen with at least one carbon-based compound and producing methane and water

Abstract

A methanation reactor for reacting dihydrogen with a carbon-based compound and producing methane. The reactor has a hollow body configured to receive a fluidized bed of catalytic particles, an inlet for each carbon-based compound and dihydrogen, and an outlet for methane and water. A water inlet is provided to inject liquid-phase cooling water into the fluidized bed. When each carbon-based compound is a gas, the reactor has at least one water-injection nozzle and at least one gas injection nozzle for a gas consisting of the carbon-based gas and dihydrogen, and at least one water-injection nozzle positioned below the gas-injection nozzle. The flow rate of water introduced into the hollow body can depend on the temperature measured in the reactor.

Claims

1. A methanation method for reacting dihydrogen with at least one of carbon monoxide and carbon dioxide in a gaseous form and producing a methane, comprising the steps of: providing inside a hollow body of methanation reactor a fluidized bed of catalytic particles; injecting a liquid-phase cooling water into a first location of said fluidized bed for mixing the liquid-phase cooling water with the catalytic particles such that the liquid-phase cooling water vaporizes on contact with the fluidized bed in said first location, absorbing thereby phase-change latent heat; inputting said at least one of carbon monoxide and carbon dioxide and dihydrogen into a second location inside said fluidized bed, said second location having said vaporized cooling water allowing thereby methanation reaction between said at least one of carbon monoxide and carbon dioxide and hydrogen; and outputting the methane and water produced from the methanation reaction; wherein said second location is distanced from said first location such that temperature of said at least one of carbon monoxide and carbon dioxide in said second location is configured to minimize coke deposit formation and while cooling the methanation reaction.

2. The methanation method according to claim 1, wherein said at least one of carbon monoxide and carbon dioxide and the dihydrogen is input in the fluidized bed.

3. The methanation method according to claim 2, wherein said first location is closer to a base of the hollow body than said second location.

4. The methanation method according to claim 3, wherein the step of injecting being achieved by at least one water-injection nozzle and the step of inputting being achieved by at least one gas injection nozzle to inject a gas comprising said at least one of carbon monoxide and carbon dioxide gas and dihydrogen, said at least one water-injection nozzle being positioned below said at least one gas-injection nozzle.

5. The methanation reactor according to claim 2, wherein the step of injecting being achieved by at least one water-injection nozzle and the step of inputting being achieved by at least one gas injection nozzle for a gas comprising said at least one of carbon monoxide and carbon dioxide gas and dihydrogen, said at least one water-injection nozzle being positioned below said at least one gas-injection nozzle.

6. The methanation method according to claim 1, further comprising a step of condensing water vapor present downstream of the step of outputting of methane and water.

7. The methanation method according to claim 6, further comprising a step of transportation of the condensed water to the water injection step.

8. The methanation method according to claim 1, further comprising, downstream of the step of outputting methane and water, a gas-solid separation step.

9. The methanation method according to claim 1, further comprising a step of temperature sensing in the reactor and a step of regulation of a flow rate of the liquid-phase cooling water introduced into the hollow body as a function of the temperature measured by the temperature sensing step.

10. The methanation method according to claim 1, further comprising a heat exchange step, downstream of the step of outputting methane and water, to cool the methane and water and to co-generate a thermal energy during the heat exchange.

11. The methanation method according to claim 1, wherein the amount of the liquid-phase cooling water introduced into the hollow body by the water inlet is more than 75% of the amount of the water output from the hollow body.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Other particular advantages, aims and features of the invention will become apparent from the non-limiting description that follows of at least one particular embodiment of the methanation reactor and the methanation method that are the subjects of the present invention, with reference to drawings included in an appendix, wherein:

(2) FIG. 1 represents, schematically, a particular embodiment of the methanation reactor that is the subject of this invention; and

(3) FIG. 2 represents, in the form of a logical diagram, steps in a particular embodiment of the methanation method that is the subject of the present invention.

DESCRIPTION OF EXAMPLES OF REALIZATION OF THE INVENTION

(4) The present description is given as a non-limiting example.

(5) It is now noted that FIG. 1 is not to scale.

(6) FIG. 1 shows a first particular embodiment of the reactor 10 that is the subject of the present invention. This reactor 10 comprises:

(7) a hollow body 105 configured to receive a fluidized bed of catalytic particles 106 and which comprises at least one nozzle 110 for injecting a carbon-based compound and dihydrogen, and at least one nozzle 120 for injecting water;

(8) an outlet 115 for methane and water;

(9) a means of gas-solid separation 135 for the methane produced by the methanation reaction;

(10) a heat exchanger 145 configured to cool the methane and water and to co-generate thermal energy during the heat exchange realized;

(11) a means of condensing 125 water vapor present downstream of the methane outlet 115;

(12) a circuit 130 for transporting condensed water to a nozzle for injecting cooling water 120; and

(13) a means of regulating 140 the flow rate of the water introduced into the hollow body 105 as a function of the temperature measured in the reactor 10 by a temperature sensor 107.

(14) The hollow body 105 is, for example, a metallic cylinder of revolution closed at its extremities. This hollow body 105 is partially filled with a fluidized catalyst bed. Through the action of gravity, this catalyst is located near the base of the hollow body 105. This hollow body 105 comprises at least one carbon-based compound and dihydrogen injection nozzle 110, allowing the carbon-based compound and dihydrogen to be introduced into the fluidized bed. Preferably, the carbon-based compound is carbon monoxide or carbon dioxide in gaseous form.

(15) In addition, the hollow body 105 comprises at least one nozzle 120 for injecting cooling water. The outlet of each nozzle 120 for injecting cooling water is preferably closer to the base of the hollow body 105 than the outlet of each nozzle 110 for injecting the carbon-based compound. In this way, the injected water is very quickly brought to the vapor state on contact with the fluidized bed, absorbing phase-change latent heat.

(16) As most of the heat exchange between the injected water and the fluidized bed occurs in the vicinity of the cooling water injection nozzle 120, the temperature of the fluidized bed at the location of the carbon-based compound injection nozzle 110 is higher than 260 C., which reduces or even eliminates the formation of carbonyl.

(17) Preferably, the amount of water introduced by the water injection nozzles 120 is more than 75% of the amount of water output from the hollow body, more preferably more than 80% and, even more preferably, more than 85%. The injection of water, by the injection nozzles 120, is preferably realized directly into the fluidized bed contained in the hollow body 105.

(18) This hollow body 105 comprises, lastly, a methane and water vapor outlet 115 that emerges onto a duct 116. This duct takes the methane and water vapor to a means of gas-solid separation 135 for the methane output. This gas-solid separation means 135 is, for example, a filter configured to hold the fine catalyst particles that may be transported by the methane and/or the water vapor.

(19) This reactor 10 also comprises, downstream of the gas-solid separation means 135, a heat exchanger 145 configured to cool the methane and water and to co-generate thermal energy during the heat exchange realized. This exchanger 145 is, for example, a U-shaped tube heat exchanger. In some variants, this exchanger 145 is an exchanger from amongst the following:

(20) horizontal tube bundle heat exchanger;

(21) vertical tube bundle heat exchanger;

(22) spiral heat exchanger;

(23) plate heat exchanger;

(24) block heat exchanger; or

(25) finned heat exchanger.

(26) This reactor 10 also comprises, downstream of the heat exchanger 145, a means of condensing 125 water vapor. This condensation means 125 is, for example, a condenser with separated fluids. In some variants, this condensation means 125 is a condenser with direct contact between a coolant fluid and the vapor to be condensed. In other variants, this condensation means 125 is a shell-and-tube or tube bundle heat exchanger. In these variants, the heat exchanger 145 and the condensation means 125 are combined into a single device. The methane, not condensed, exits via a duct 117.

(27) In some variants, downstream of the condensation means 125, the reactor 10 comprises the circuit 130 for transporting condensed water, one part of which is evacuated by an output duct 118 and one part of which is transported to the nozzles 120 for injecting cooling water by utilizing a pump 132. The proportion of water recycled in this way is of the same order of magnitude as the condensate flow-rate, i.e. of the order of 85% to 95% depending on the temperature of the condensation means.

(28) The reactor 10 also comprises a means of regulating 140 the flow rate of the water introduced into the hollow body 105 as a function of the temperature measured in the bed in the reactor 10 by a temperature sensor 107. The regulation means 140 is, for example, a valve controlled pneumatically or electronically by an electronic circuit (not shown). This electronic circuit receives information representative of the temperature inside the hollow body 105 and actuates the valve as a function of the information received so that the flow-rate of water introduced into the hollow body is an increasing function of the temperature measured. In this way a control loop is realized for the interior temperature in the fluidized catalyst bed of the hollow body 105.

(29) FIG. 2 shows logical diagram of steps in a particular embodiment of the methanation method 20 that is the subject of the present invention. The method 20 comprises:

(30) a step 205 of injecting liquid-phase cooling water into a fluidized bed contained in a hollow body during a methanation reaction step 215;

(31) a step 210 of inputting the carbon-based compound and hydrogen into the hollow body configured to receive a fluidized bed of catalytic particles;

(32) a step 215 of methanation reaction between the hydrogen and the carbon-based compound to produce methane and water;

(33) a step 225 of measuring the temperature inside the hollow body; and

(34) a step 220 of outputting methane and water.

(35) The step 205 of injecting cooling water into the hollow body is realized, for example, by utilizing cooling water injection nozzles that inject the water at the location of a fluidized catalyst bed contained in the hollow body.

(36) The step 210 of inputting the carbon-based compound and hydrogen into the hollow body is realized, for example, by utilizing cooling water injection nozzles for injecting carbon monoxide or dioxide and dihydrogen. These injection nozzles inject the gas above at least one, and preferable all, of the cooling water injection nozzles.

(37) The step 220 of outputting methane and water is realized, for example, by utilizing a duct, one inlet of which is located on an upper portion of the hollow body.

(38) The measurement of the temperature inside the hollow body carried out during the step 225 is used to slave the flow-rate of the water introduced into the hollow body during the step 205, this flow-rate being an increasing function of the temperature inside the hollow body.

(39) The various steps shown in FIG. 2 are performed continuously and simultaneously during the nominal operation of the reactor. Preferably, the water introduced into the hollow body during the step 205 is the water from the reaction cooled by a condenser and, possibly, a heat exchanger, or a device combining the functions of a condenser and a heat exchanger.

(40) As can be seen by reading the description above, the present invention enables the size of a methanation reactor to be reduced. In effect the injection of water directly into the reaction medium means that one does not have to use a heat exchanger wherein the exchange surfaces to be used are large. In addition, the injected water is used within the reactor through the gas to water reaction formula so as to ensure the presence of dihydrogen in the methanation reaction. In addition, the presence of a water condensation means downstream of the methane and water outlet allows the water produced naturally by the methanation reaction to be recycled for subsequently cooling the reaction. Lastly, the temperature inside the reactor is slaved by introducing water according to an increasing function of the temperature measured in the reactor, and the production of carbonyl can be minimized.