SYSTEM FOR SUPPLYING CO2 GAS TO A FACILITY THAT REQUIRES CO2 OR A MIXTURE COMPRISING CO2, SUCH AS AN ABATTOIR OR A GREENHOUSE FOR CULTIVATING PLANTS

Abstract

A method for supplying CO.sub.2 gas to a site comprising a facility (20) that requires CO.sub.2 or a mixture comprising CO.sub.2, such as an abattoir or a greenhouse for cultivating plants, comprises the following steps: a boiler (4) capable of supplying hot water to the site is arranged within the site, the boiler carrying out the process of oxycombustion between a fuel (14) and pure oxygen (1), the oxygen that supplies the boiler being obtained from a liquid oxygen source present on the site; and some or all of the CO.sub.2 contained in the flue gas produced by the boiler is recovered by transferring heat between the flue gas and the liquid oxygen in an exchanger (2).

Claims

1. A process for feeding, with gaseous CO.sub.2, a site comprising an installation requiring CO.sub.2 or a mixture comprising CO.sub.2, the process comprising the steps of: supplying hot water to the site using a boiler, the boiler employing oxy-fuel combustion between a fuel and pure oxygen, the pure oxygen fed to the boiler being obtained from a liquid oxygen source present on the site; recovering all or part of CO.sub.2 contained in the flue gases produced by the boiler, arranging heat exchange between the flue gases and the liquid oxygen in an heat exchanger; and recovering CO.sub.2 in its gaseous form or its liquid form, while having purified in the heat exchange all or part of water comprised in the flue gases.

2. The process as claimed in claim 1, wherein CO.sub.2 recovered in its gaseous form is stored or (sequestered) for the purpose of subsequent use on the site under consideration, or else used as a just-in-time stream, as a stream synchronized with a hot water requirement.

3. The process as claimed in claim 1, wherein the CO.sub.2 recovered in its liquid form is stored in a tank as liquid CO.sub.2 for the purpose of subsequent use on the site under consideration.

4. The process as claimed in claim 3, wherein the heat exchanger in which heat exchange between the flue gases and the liquid oxygen is arranged is configured to convey the flue gases entering the heat exchanger under pressure and temperature conditions to liquefy CO.sub.2 present in the flue gases, thus taking advantage of cold of the liquid oxygen present on the site, thereby without a need for a contribution of electrical energy.

5. The process as claimed in claim 1, wherein the installation requiring CO.sub.2 is an installation for anesthesia of poultry or animals, before slaughtering.

6. The process as claimed in claim 1, wherein the installation requiring CO.sub.2 is an installation for cultivation of plants in a greenhouse.

7. The process as claimed in claim 6, wherein the requirement for CO.sub.2 occurs essentially during the day, whereas the requirement for heating the greenhouse occurs essentially during the night, CO.sub.2 recovered in liquid form during the night being stored in a tank for liquid CO.sub.2 for the purpose of use of CO.sub.2 during the day when the greenhouse requires CO.sub.2.

8. The process as claimed claim 1, wherein the heat exchange between the flue gases and the liquid oxygen is preceded by one or more treatments of the flue gases by physical and/or chemical and/or cryogenic separation methods, the one or more treatments comprising: heating the liquid oxygen and the fuel gas, in order to improve the combustion occurring in the boiler and to reduce discharges of nitrogen oxides; condensing a steam of the flue gases; and removing possible dust generated by a furnace of the boiler.

9. A device for feeding, with gaseous CO.sub.2, a site comprising an installation requiring CO.sub.2 or a mixture comprising CO.sub.2, the device comprising: a boiler, configured to and capable of providing hot water to the site, the boiler employing oxy-fuel combustion between a fuel and pure oxygen, the oxygen fed to the boiler being obtained from a liquid oxygen source present on the site; and a heat exchanger, configured to arrange heat exchange between the flue gases and the liquid oxygen in order to recover all or part of CO.sub.2 contained in the flue gases produced by the boiler, and to feed to, using the recovered CO.sub.2, the installation; wherein the heat exchanger is configured to recover, according to the use which will be made thereof on the site under consideration, CO.sub.2 in its gaseous form or its liquid form, while having purified in the heat exchange all or part of the water comprised in the flue gases.

10. The device as claimed in claim 9, wherein the heat 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 heat exchanger under pressure and temperature conditions to liquefy CO.sub.2 present in the flue gases, thus taking advantage of cold of the liquid oxygen present on the site, thereby without a need for a contribution of electrical energy.

11. The device as claimed in claims 9, further comprising steps for treatment of the flue gases before their arrival in the heat exchanger, wherein the treatment steps employing physical and/or chemical and/or cryogenic separation methods, the treatment steps comprising one or more of the following actions: heating the oxygen and the fuel gas, in order to improve the combustion occurring in the boiler and to reduce discharges of nitrogen oxides; condensing a steam of the flue gases; and removing possible dust generated by a furnace of the boiler.

12. The device as claimed in claim 9, wherein the installation requiring CO.sub.2 is an installation for anesthesia of poultry or animals, before slaughtering.

13. The device as claimed in claim 9, wherein the installation requiring CO.sub.2 is an installation for cultivation of plants in a greenhouse.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0064] For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawing, in which like elements are given the same or analogous reference numbers and wherein:

[0065] FIG. 1 illustrates a system for supplying CO.sub.2 gas to a facility that requires CO.sub.2 or a mixture comprising CO.sub.2, such as an abattoir or a greenhouse for cultivating plants, in accordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0066] That which takes place in the various items of equipment present in FIG. 1, and also an implementational example giving the thermal characteristics of the fluids involved at each stage, data representing only one implementational example which are only illustrative of the items of equipment and operating conditions used here, are described in detail in that which follows: [0067] In the boiler 4: the municipal water enters therein at a temperature in the vicinity of 25 C. and emerges therefrom at a temperature in the vicinity of 85 C.; the flue gases exit from the boiler at a temperature in the vicinity of 220 C. [0068] In the heater 10: the fuel gas enters at a temperature in the vicinity of 15 C. and emerges therefrom at a temperature in the vicinity of 95 C., and the flue gases exit from this element 10 at a temperature in the vicinity of 210 C. [0069] In the heater 11: the oxygen enters at a temperature in the vicinity of 5 C. and emerges therefrom at a temperature in the vicinity of 95 C., and the flue gases exit from this element 11 at a temperature in the vicinity of 200 C. [0070] In the condenser 12, the municipal water enters therein at a temperature in the vicinity of 5 C. and exits therefrom at a temperature in the vicinity of 25 C., and the flue gases exit from this element 12 at a temperature in the vicinity of 90 C. (the exchanger 2 thus makes it possible to recover heat from the flue gases and preheats the water which will enter the boiler (principle of the condensation boilers)). [0071] In the exchanger 2, the oxygen enters at a temperature in the vicinity of 183 C. and exits therefrom at a temperature in the vicinity of +5 C., and the flue gases exit from this element 2 at a temperature in the vicinity of +2 C. In this stage, the water is completely condensed and only CO.sub.2 remains. [0072] In the element 7, the municipal water enters therein at a temperature in the vicinity of 15 C. and emerges therefrom at a temperature in the vicinity of 5 C., and the flue gases exit from this element 7 at a temperature in the vicinity of 10 C. (the exchanger 2 thus makes it possible to raise the temperature of the CO.sub.2 by around 10-12 C. after having removed the water therefrom, which is required for such anesthesia applications according to the legislations in force).

[0073] Consideration is given, in that which follows, to the example of a 40 tonne/h abattoir, anesthetizing under the following conditions: [0074] A CO.sub.2 requirement of 5 g per kg of poultry. [0075] For production of 10 000 chickens per hour, considering chickens weighing on average 2.2 kg each, a requirement of 110 kg of CO.sub.2 per hour is obtained, hence 2500 mol/h of CO.sub.2, and thus 25002=5000 mol/h of oxygen, i.e. 160 kg of oxygen. [0076] 2500 mol of CH.sub.416=40 kg of CH.sub.4 per hour. [0077] Considering that the combustion of methane at 25 C. releases an energy of 39.77 MJ/m.sup.3 (55.53 MJ/kg), i.e. 11.05 kWh/m.sup.3 (15.42 kWh/kg=616 kWh). [0078] The weight of CO.sub.2 released per mole of octane consumed is 44 g. [0079] The methane consumption/CO.sub.2 discharges ratio is 44/16=2.75 g. [0080] 1 kg of methane discharges 2.75 kg of CO.sub.2. [0081] A saving of 20% with regard to the CH.sub.4 (saving in energy with nitrogen absence+rise T C. oxidant/fuel, radiative transfers): (616/100)20=123 kW [0082] 1230.10 per kW gas (price which can be regarded as reference)=12.3 per hour [0083] Under the conditions of the present simulation, the saving with regard to natural gas makes it possible to pay a part of the oxygen for the production of the CO.sub.2:

1600.088 per kg=14.08 O.sub.2 per hour

14.08-12.3=1.78 per 110 kg of CO.sub.2, i.e. 1.78/1101000=16.1. [0084] Which amounts to a cost of the CO.sub.2 at 16.1/tonne. [0085] While no saving occurs with regard to the combustion, the cost of the CO.sub.2 is in the vicinity of 134.5 per tonne (to be compared with approximately 150/tonne for commercial CO.sub.2).

[0086] In this field of tunnels for the anesthesia of poultry, it is generally considered that it is desired to achieve a content of CO.sub.2 in the tunnel which is at least 55%.

[0087] And thus it is necessary to emphasize the fact that an air/CH.sub.4 combustion would not make it possible to achieve sufficient values of CO.sub.2 in the flue gases (the presence of nitrogen in the combustion air limits the concentration of CO.sub.2 to 11.5%).

[0088] The example of a tunnel poultry anesthetization installation has been enlarged upon in detail in FIG. 1, where the operation was carried out under conditions where the CO.sub.2 requirement is synchronized with the hot water requirement: hot water is used to pluck the poultry and gaseous CO.sub.2 is used to put the poultry to sleep; it is consequently not necessary here to liquefy the CO.sub.2.

[0089] However, in other applications, it will be useful to liquefy the CO.sub.2; mention may be made, for example, of the case of use of the CO.sub.2 by greenhouse growers; the CO.sub.2 requirement corresponds to the photosynthesis of the plant thus in the day, whereas the requirement to heat the greenhouse is predominantly effective overnight (when it is colder).

[0090] Thus, for these users, it is advantageous to liquefy the CO.sub.2 at night in order to distribute it during the day (in sunlight).

[0091] The exchanger 2 will then be configured to drop to 20 C. and 20 bar, by having added a compressor at the inlet of the exchanger 2, the means 8 then no longer having a reason to be in such an application (it should be noted that this greenhouse grower variant is not represented in FIG. 1).

[0092] The exchanger 2 for carrying out such a liquefaction can also be a cryocondenser, which is a heat exchanger operating at low temperature; the gaseous effluent resulting from the industrial process enters the interior of a shell-and-tube, then advances through a series of baffles, around a fin tube bundle in which a liquid cryogen circulates.

[0093] As has been said, CO.sub.2 is a gas which changes in state to the solid phase at a pressure close to 4.7 bar; it is thus necessary to avoid approaching this pressure.

[0094] A pressure between 16 bar and 20 bar is economically favorable, while a temperature of 20 C. requires few capital expenditures in terms of insulation.

[0095] It is thus generally considered that the pair 20 bar, 20 C. represents the best compromise.

[0096] Reference herein to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the invention. The appearances of the phrase in one embodiment in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term implementation.

[0097] As used in this application, the word exemplary is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as exemplary is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the word exemplary is intended to present concepts in a concrete fashion.

[0098] Additionally, the term or is intended to mean an inclusive or rather than an exclusive or. That is, unless specified otherwise, or clear from context, X employs A or B is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then X employs A or B is satisfied under any of the foregoing instances. In addition, the articles a and an as used in this application and the appended claims should generally be construed to mean one or more unless specified otherwise or clear from context to be directed to a singular form.

[0099] The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

[0100] About or around or approximately in the text or in a claim means 10% of the value stated.

[0101] As used herein, room temperature in the text or in a claim means from approximately 20 C. to approximately 30 C.

[0102] The term ambient temperature refers to an environment temperature approximately 20 C. to approximately 30 C.

[0103] Comprising in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing i.e. anything else may be additionally included and remain within the scope of comprising. Comprising is defined herein as necessarily encompassing the more limited transitional terms consisting essentially of and consisting of; comprising may therefore be replaced by consisting essentially of or consisting of and remain within the expressly defined scope of comprising.

[0104] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range. Any and all ranges recited herein are inclusive of their endpoints (i.e., x=1 to 4 or x ranges from 1 to 4 includes x=1, x=4, and x=any number in between), irrespective of whether the term inclusively is used.

[0105] It will be understood that many additional changes in the details, materials, steps, and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above and/or the attached drawings.

[0106] While embodiments of this invention have been shown and described, modifications thereof may be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments described herein are exemplary only and not limiting. Many variations and modifications of the composition and method are possible and within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims which follow, the scope of which shall include all equivalents of the subject matter of the claims.