System for supplying CO2 gas to facility requiring CO2 or mixture containing CO2, such as slaughter house or greenhouse for cultivating plants

Abstract

The invention relates to a method for supplying CO2 gas to a venue comprising a facility (20) requiring CO2 or a mixture containing CO2, such as a slaughter house or a greenhouse for cultivating plants, characterized by the following steps: arranging a boiler (4) capable of supplying hot water to the venue within the venue, said boiler performing an oxygen combustion process between fuel (14) and pure oxygen (1), the oxygen supplied to the boiler being obtained from a liquid oxygen source present in the venue; some or all of the CO2 contained in the flue gas produced by the boiler is recovered by transferring heat between the flue gas and liquid oxygen in an exchanger (2).

Description

[0001] The present invention relates to methods and installations for using gaseous CO2, in particular in the food processing industry.

[0002] This area includes in particular the beverage industry, modified atmospheres for the preservation of foods, or poultry anesthesia in slaughterhouses, or also the cultivation of plants in greenhouses.

[0003] The demand for CO2 in developed countries is still increasing (especially for the above applications).

[0004] This CO2 is mainly produced from fertilizer and methanol (byproduct) plants, or from plants used to produce hydrogen. Due to frequent shutdowns of fertilizer production plants and geopolitical tensions, the availability of this molecule has become crucial, which in turn has a strong impact on the price of this gas.

[0005] Due to these frequent crises, it has thus become common in many countries to observe, for example, in recent years that greenhouse growers have been without commercial CO2 supplies for several months of the year, which, as is known, has a direct impact on their productivity.

[0006] There are also strong environmental constraints, as developed countries want to reduce greenhouse gas emissions by promoting the search for solutions aimed at reducing the carbon footprint, which will have a direct impact on the methods of producing CO2.

[0007] The present invention seeks to provide an innovative solution for producing CO2 at the actual site of the user of such CO2.

[0008] As will be seen in more detail below, the invention proposes to use one or more devices (boilers) conventionally present in such sites for generating heat by converting them to oxy-fuel combustion. In this way, the heat generated by the boiler will result from the production of CO2 and will therefore be considered "unavoidable heat" in the legal sense.

[0009] Oxy-fuel combustion is a combustion process in which the oxidant gas is no longer air but rather "pure" oxygen, ie, characterized by a purity typically greater than 95% and 99% for liquid oxygen.

[0010] Oxy-fuel combustion (thus using oxygen instead of air) has been adopted by certain industries operating at high temperatures (glass works, cement plants, metallurgical plants, etc.) because it offers many advantages, among which can be mentioned:

[0011] • Flue gas volume is reduced by reducing / removing nitrogen ballast.

[0012] • In direct correlation to the reduction in flue gas volume, thermal efficiency is increased (due to lower heat losses in the flue gases).

[0013] • Heat transfer is enhanced by means of two phenomena: Since the flue gas consists essentially of exhaust gases (CO2, H2O), the flame temperature increases and the radiant heat flux increases.

[0014] • There is a reduction in the emission of thermal NOx or dioxin-type pollutants (associated with the reduction in the volume of the oxidant). Special literature reports gains in fuel here ranging from 10% to 40%. The heating of the oxidant and the fuel also makes it possible to reduce the consumption of the latter.

[0015] In particular, the aim is to increase the CO 2 content of the combustion flue gases, which thus contain mainly CO 2 and water, by removing the nitrogen ballast.

[0016] The purer the oxygen used for combustion, the closer the combustion flue gas is to a binary mixture of H2O / CO2. In turn, the main stage of capturing CO2 consists in condensing water.

[0017] Another important advantage is that the volume of flue gas to be treated is reduced. The residual pollutants are less diluted than when burning in combustible air.

[0018] Thus, the present invention relates to a site where CO2 is used, and in addition the site is provided with a boiler capable of supplying hot water to the site, the boiler (in particular a condensing boiler) using an oxy-fuel combustion intermediate between a fuel (CH4, C3H8, etc.) and pure oxygen, the oxygen supplied to the boiler being obtained from a liquid oxygen source present at the site,

[0019] And then, according to the invention, all or part of the CO 2 contained in the flue gases produced by the boiler is recovered, wherein a heat exchange is arranged between said flue gases and liquid oxygen in an exchanger.

[0020] In particular, the present invention is noteworthy for proposing the use of the "free" cold of liquid oxygen already present on site to purify and in some cases liquefy the CO2 present in the flue gases produced by the boiler, in this case without the contribution of electrical energy which is usually required for such a change of state (by compression / expansion).

[0021] The "pure" CO2 thus obtained (recovered), in its gaseous or liquid form, can be stored (sequestered) for the purpose of subsequent use in the site under consideration, or used "as a just-in-time stream", as a stream "synchronized" with the hot water demand and therefore the operation of the boiler.

[0022] Schematically, the heat exchanger used can be a plate exchanger or else a tubular exchanger.

[0023] In the exchanger, a change of state of the CO2 (liquid at 20 bar / -20°C) is achieved due to the drop in temperature.

[0024] The operation of a condensing gas boiler uses the same principles as a conventional boiler and in addition can utilize all the energy produced in the gas combustion process.

[0025] In conventional boilers, the central heating water circuit is heated by means of the combustion of natural gas. Condensing gas boilers utilize the energy contained in the combustion flue gases. The flue gases emitted during the combustion of natural gas contain steam; the latter condenses, releasing heat. The return water from the heating circuit is heated by means of this energy, and the discharge of the water released during the condensation process (condensate) is carried out via the wastewater system.

[0026] By way of example, it may be considered that for the anesthesia of chickens or pigs it is advantageous to synchronize the CO2 demand with the hot water demand; the temperature drop obtained by increasing the cooling of the liquid oxygen makes it possible to purify the CO2 gas (for example, at 20 bar and -20°C, only CO2 will be liquid).

[0027] Still by way of example, for other applications, such as greenhouses for growing plants, it may be advantageous to store the liquid CO 2 in conventional CO 2 tanks for use at another time.

[0028] By way of example, in the case of a tomato greenhouse, greenhouse growers heat the greenhouse at night and thereby produce CO2 at night, whereas they need CO2 during the day for photosynthesis; therefore it is necessary to store the CO2 in cryogenic tanks.

[0029] Of course, the person skilled in the art is aware of the existence of the prior art, which can be illustrated in particular by documents JP2009 / 203860 and WO 2022 / 070125, which relate to facilities of the power station or generator type, wherein, by way of example, in document JP 2009 / 203860, a supercritical fluid (e.g. nitrogen or e.g. CO2) is supplied to the turbine (10), wherein the fluid exhausted by combustion is purified of the CO2 therein by exchange with liquid oxygen, for environmental reasons (zero emission of CO2, ozone layer, etc.), the CO2 thus recovered being directed to suitable tanks ("water flows to the waste water storage tank 83 and carbon dioxide flows to the waste carbon dioxide storage tank 84").

[0030] In all cases:

[0031] - These existing documents do not include oxy-fuel combustion boilers for supplying hot water to a given site;

[0032] - these prior art documents do not describe a situation in which the site consuming hot water also requires gaseous CO 2 or a gas mixture containing CO 2 for a piece of equipment at the site (such as a slaughterhouse or also a greenhouse for growing plants);

[0033] - These prior art documents do not describe the use of CO2 recovered in the flue gases of the boiler to supply such a piece of equipment consuming CO2.

[0034] The invention further relates to a method for supplying gaseous CO2 to a location, including an installation requiring CO2 or a mixture containing CO2, such as a slaughterhouse or also a greenhouse for growing plants, characterized in that the following measures are implemented:

[0035] - having a boiler available within the site capable of supplying hot water to the site, the boiler using oxy-fuel combustion intermediate between fuel and pure oxygen, the oxygen supplied to the boiler being obtained from a liquid oxygen source present in the site;

[0036] - Recovery of all or part of the CO2 contained in the flue gases originating from the boiler, wherein a heat exchange is arranged between said flue gases and liquid oxygen in an exchanger.

[0037] The invention therefore also relates to a method and a device for purifying and liquefying CO2 at a user site, these purification and liquefaction being achieved by increasing the cooling of liquid oxygen present at the site.

[0038] Prior to this liquefaction of CO2, the flue gases may be subjected to one or more treatments by physical and / or chemical, but also cryogenic, separation methods, with the objectives of:

[0039] - Heating oxygen and fuel gas to improve combustion and reduce nitrogen oxide emissions;

[0040] - condensing steam in flue gases and recovering the heat or latent energy of condensation (steam is converted into liquid water by lowering the temperature of flue gases);

[0041] - Removal of dust (refractory dust) that may be generated by the furnace of the boiler.

[0042] By way of example, oxy-fuel combustion using methane requires 64 g oxygen per 16 g CH4 and will produce 36 g water (easily separated) and 44 g CO2. Thus, the O2 / CO2 ratio is 64 / 44 = 1.45.

[0043] CO2 requires about 85 kcal / kg to change from +20°C to -20°C (20 bar). At a temperature of -30°C at 8 bar, liquid oxygen releases 71.7 kcal / kg from its liquid form. Therefore, the theoretical refrigeration available is (71.7×1.45)+103 kcal to liquefy 1 kg of CO2.

[0044] The above advantages of using liquid oxygen allow the user of such oxy-fuel combustion to afford most (indeed even all) of the oxygen required for combustion. It is known that CO2 sequestration is chosen in order to upgrade the gas relative to the conventional process using commercial CO2, where the user can obtain CO2 at a widely competitive level; in addition, such a user reduces its CO2 emissions by reducing its consumption of CH4 and by not using "commercial" sources of CO2 (since such sources are recovered on site).

[0045] Attached Figure 1 ] shows an example of a piece of equipment suitable for implementing the invention in the case of use in a facility considered for tunnel anesthetization of poultry. In the case of such facilities, work is carried out under conditions where the demand for CO2 is synchronized with the demand for hot water: hot water is used to pluck the poultry, and gaseous CO2 is used to put them to sleep. In this case, there is no need to liquefy the CO2.

[0046] Should Figure 1 The names of the components that exist in are as follows:

[0047] -1: Liquid oxygen storage.

[0048] - 2: O2 vaporizer: This exchanger 2 carries out a heat exchange between the flue gases and liquid oxygen; the temperature of the flue gases is reduced therein to a temperature typically close to 2°C in order to remove as much water as possible and thereby preserve the CO2.

[0049] -3: Plate for regulating the injection of O2 and CH4.

[0050] -4: Boiler.

[0051] -5: Burner.

[0052] -6: Module for analyzing flue gases.

[0053] -7: Low temperature purifier.

[0054] - 8: low-pressure turbine (the turbine 8 makes it possible to extract the flue gases originating from the exchanger 7 and send them into the tunnel 20 , while also compensating for the pressure drops that occur in the previous stages).

[0055] -9: Regulating valve (controlled by the anesthesia tunnel; if the tunnel is closed, the gas is sent to the outside, and the more CO2 the tunnel needs, the more the valve opens towards the tunnel circuit).

[0056] - 10: CH4 heater (this heater makes it possible to heat the fuel gas before feeding it to the burner).

[0057] - 11: O2 heater (this heater makes it possible to heat the oxygen before feeding it to the burner).

[0058] - 12: Flue gas condenser (makes it possible to heat the water before sending it to the boiler).

[0059] - 13: Municipal water or borehole water, which will be heated for use on site and is cold (usually 10°C to 20°C) This water also makes it possible to reduce the temperature of the flue gases at the boiler outlet.

[0060] -14: Fuel required to heat water via boiler; this fuel may also be heated to improve combustion efficiency.

[0061] -20: Poultry anesthesia tunnel.

[0062] The following describes in detail the Figure 1 Examples of what happens in the various devices present in the embodiment and the thermal characteristics of the fluids involved in each stage are also given (the data represent only one embodiment, which only illustrates the equipment and operating conditions used here):

[0063] - In the boiler 4: the municipal water enters it at a temperature of around 25°C and flows out of it at a temperature of around 85°C; the flue gases leave the boiler at a temperature of around 220°C.

[0064] - In the heater 10: the fuel gas enters at a temperature of around 15°C and flows out of it at a temperature of around 95°C, and the flue gases leave the element 10 at a temperature of around 210°C.

[0065] - In the heater 11 : oxygen enters at a temperature of around 5°C and flows out of it at a temperature of around 95°C, and the flue gases leave this element 11 at a temperature of around 200°C.

[0066] - In the condenser 12, municipal water enters it at a temperature of around 5°C and leaves it at a temperature of around 25°C, and the flue gases leave this element 12 at a temperature of around 90°C (exchanger 12 thus makes it possible to recover heat from the flue gases and preheat the water that will enter the boiler (principle of a condensing boiler)).

[0067] - In exchanger 2, oxygen enters at a temperature of around -183° C. and leaves it at a temperature of around +5° C., and flue gases leave this element 2 at a temperature of around +2° C. At this stage, water is completely condensed and only CO2 remains.

[0068] - In element 7, municipal water enters it at a temperature of around 15°C and flows out of it at a temperature of around 5°C, and the flue gases leave this element 7 at a temperature of around 10°C (exchanger 7 thus makes it possible to raise the temperature of the CO2 after the water has been removed from it by approximately 10°C-12°C, which is required for this type of anesthetic application according to current regulations).

[0069] Consider below the example of a 40 t / h slaughterhouse, with anesthesia under the following conditions:

[0070] -CO2 requirement is 5g / kg poultry.

[0071] - For a production of 10,000 chickens per hour, taking into account that each chicken weighs 2.2 kg on average, a requirement of 110 kg CO2 per hour is obtained, therefore 2500 mol / h of CO2 and therefore 2500 x 2 = 5000 mol / h of oxygen, ie 160 kg of oxygen.

[0072] -2500 mol of CH4 x 16 = 40 kg of CH4 / hour.

[0073] - Considering that the energy released by burning methane at 25°C is 39.77MJ / m 3 (55.53MJ / kg), or 11.05kWh / m 3 (15.42kWh / kg=616kWh).

[0074] - The weight of CO2 released for each mole of octane consumed is 44 g.

[0075] -Methane consumption / CO2 emission ratio is 44 / 16=2.75g.

[0076] -1kg of methane emits 2.75kg of CO2.

[0077] - Regarding CH4, 20% saving (energy saving by no nitrogen + raising T°C of oxidant / fuel, radiation transfer): (616 / 100)×20=123kW

[0078] -123×€0.10 / kW gas (price can be used as reference) = €12.3 / hour

[0079] - Under the conditions of this simulation, the savings on natural gas make it possible to pay for part of the oxygen used to produce CO2:

[0080] 160 x €0.088 / kg = €14.08 O2 / hour

[0081] 14.08-12.3=€1.78 / 110kg CO2, i.e. 1.78 / 110×1000=16.1.

[0082] This equates to a cost of €16.1 / tonne of CO2

[0083] Although there is no saving in combustion, the cost of CO2 is around €134.5 / tonne (compared to around €150 / tonne for commercial CO2).

[0084] In the field of tunnels for anesthetizing poultry, it is generally considered desirable to achieve a CO2 content of at least 55% in the tunnel.

[0085] And therefore it is necessary to emphasize the fact that air / CH4 combustion will not make it possible to achieve sufficient CO2 values ​​in the flue gases (the presence of nitrogen in the combustion air limits the CO2 concentration to 11.5%).

[0086] Examples of tunnel poultry anesthesia facilities are Figure 1 , where the operation is carried out under conditions where the CO2 demand is synchronized with the hot water demand: the hot water is used to pluck the poultry and the gaseous CO2 is used to put the poultry to sleep; therefore, it is not necessary to liquefy the CO2 here.

[0087] However, in other applications, liquefying the CO2 would be useful; for example, one can mention the use of CO2 by greenhouse growers; the CO2 demand corresponds to the photosynthesis of the plants and is therefore during the day, while the need to heat the greenhouse is mainly effective at night (when the greenhouse is cooler).

[0088] Therefore, for these users, it is advantageous to liquefy the CO2 at night in order to distribute it during the day (in sunlight).

[0089] By further configuring the exchanger 2 to go down to -20°C and 20 bar by adding a compressor at the inlet of the exchanger 2, the device 8 no longer has a reason to be in this application (it should be noted that this "greenhouse grower" variant is not in Figure 1 denoted in ).

[0090] The exchanger 2 used for this liquefaction can also be a cryogenic condenser, which is a heat exchanger operating at low temperatures; the gaseous effluent generated by the industrial process enters the interior of the shell and tubes and then proceeds through a series of baffles surrounding the finned tube bundles in which the liquid refrigerant circulates.

[0091] As mentioned above, CO2 is a gas that changes state to a solid phase at a pressure close to 4.7 bar; therefore, it is necessary to avoid approaching this pressure.

[0092] Pressures between 16 and 20 bar are economically advantageous, while a temperature of -20°C requires little capital expenditure in terms of insulation.

[0093] Therefore, it is generally considered that the pairing "20 bar, -20°C" represents the best compromise.

Claims

1. A method for supplying gaseous CO2 to a location comprising an installation (20) requiring CO2 or a mixture containing CO2, such as a slaughterhouse or also a greenhouse for growing plants, characterized in that Implement the following measures: - having a boiler (4) available in the said site, capable of supplying hot water to the site, said boiler using oxy-fuel combustion between a fuel (14) and pure oxygen (1), the oxygen supplied to the boiler being obtained from a source of liquid oxygen (1) present in the site; - Recovery of all or part of the CO2 contained in the flue gases produced by the boiler, wherein a heat exchange is arranged between said flue gases and the liquid oxygen in the exchanger (2).

2. The method according to claim 1, characterized in that The CO 2 thus recovered is in its gaseous form and is stored (sequestered) with the purpose of subsequent use in the site under consideration, or used “as a just in time stream”, as a stream “synchronized” with the hot water demand.

3. The method according to claim 1, characterized in that The CO 2 thus recovered is in its liquid form and is stored in tanks for liquid CO 2 with the purpose of subsequent use at the site under consideration.

4. The method according to claim 3, characterized in that The exchanger in which the heat exchange between the flue gases and the liquid oxygen is arranged is configured to convey the flue gases entering the exchanger under pressure and temperature conditions capable of liquefying the CO2 present in these flue gases, thereby utilizing the cold of the liquid oxygen present in the place, in this case without requiring the contribution of electrical energy, which is usually required for this change of state.

5. The method of claim 2, wherein: The facilities that require CO2 are those used to anesthetize poultry or other animals prior to slaughter.

6. The method according to claim 3 or 4, wherein: The facility requiring CO2 is a facility for growing plants in a greenhouse, wherein the demand for CO2 occurs essentially during the day, while the demand for heating the greenhouse occurs essentially at night, and at night, i.e. during the operating phase of the boiler, the CO2 recovered in liquid form is stored in a tank for liquid CO2 for the purpose of using the CO2 during the day when needed in the greenhouse.

7. The method according to any one of the preceding claims, characterized in that Prior to said heat exchange between said flue gases and said liquid oxygen, said flue gases (12, 11, 10, 7, etc.) are subjected to one or more treatments by physical and / or chemical and / or cryogenic separation methods, with the aim of carrying out one or more of the following actions: - heating the oxygen and the fuel gas in order to improve the combustion taking place in the boiler and reduce the emissions of nitrogen oxides; - condensing the steam of these flue gases; - Remove dust that may be generated by the furnace of the boiler.

8. A device for supplying gaseous CO2 to a site, the site comprising an installation (20) requiring CO2 or a mixture containing CO2, such as a slaughterhouse or also a greenhouse for growing plants, the site comprising a boiler (4) capable of supplying hot water to the site, the boiler using an oxygen-fuel combustion between a fuel (14) and pure oxygen (1), the oxygen supplied to the boiler being obtained from a source of liquid oxygen (1) present in the site, characterized in that The device comprises a heat exchanger (2) which makes it possible to arrange a heat exchange between the flue gases and the liquid oxygen so as to make it possible to recover all or part of the CO2 contained in the flue gases produced by the boiler and to supply the facility with the CO2 thus recovered.

9. The device according to claim 8, characterized in that The CO 2 thus recovered is in its liquid form, and in that the device comprises means for storing the CO 2 thus recovered in its liquid form, for its subsequent use at the site in question.

10. The device according to claim 8, characterized in that The CO 2 thus recovered is in its gaseous form, and in that the plant comprises means for storing this CO 2 thus recovered, so that it can be subsequently used at the site in question.

11. The device according to claims 8 and 9, characterized in that The heat exchanger (2) making it possible to arrange a heat exchange between the flue gases and the liquid oxygen is configured to convey the flue gases entering the exchanger under pressure and temperature conditions capable of liquefying the CO2 present in the flue gases, thereby taking advantage of the cold of the liquid oxygen present in the place, in this case without requiring the contribution of electrical energy, which is usually required for this change of state.

12. The device according to any one of claims 8 and 11, characterized in that The device comprises means (12, 11, 10, 7, etc.) for treating the flue gases before they reach the exchanger, using physical and / or chemical and / or cryogenic separation methods, with the aim of carrying out one or more of the following actions: - heating the oxygen and the fuel gas in order to improve the combustion taking place in the boiler and reduce the emissions of nitrogen oxides; - condensing the steam of these flue gases; - Remove dust that may be generated by the furnace of the boiler.

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