Integrated process for oxy-fuel combustion and production of oxygen

Abstract

Process for heating via oxy-fuel combustion in which a stream of air is heated by means of at least one portion of the residual heat present in the fuel gases discharged from the combustion chamber, at least one portion of said hot air stream is introduced into an oxygen production unit in which a portion of the oxygen present in the hot air stream is extracted by means of one or more ITM, with a first stream of oxygen at high temperature being obtained, said first stream of oxygen is mixed with a second stream of oxygen so as to obtain a total stream of oxygen at a lower temperature than that of the first stream of oxygen, at least one portion of the total stream of oxygen being transported to the combustion chamber and used within as oxygen-rich oxidizer.

Claims

1. A process for heating by oxy-fuel combustion in a furnace, comprising the steps of: incinerating a fuel with an oxygen-rich oxidant in a combustion chamber of the furnace with generation of heat and flue gases in the combustion chamber; discharging the generated flue gases from the combustion chamber, said discharged flue gases containing residual heat; heating a stream of air with at least a part of the residual heat present in the discharged flue gases to produce a stream of hot air at a temperature TA1; introducing at least a part of the stream of hot air into an oxygen production unit in which a portion of the oxygen present in said at least a part of the stream of hot air is extracted with one or more ITMs, thereby producing a first oxygen stream at a temperature TO1 and a stream of oxygen-depleted air at a temperature TA2 in which TA2<TA1; downstream of the oxygen production unit, mixing the first oxygen stream with a second oxygen stream to thereby produce an overall oxygen stream at a temperature TO2 in which TO2<TO1, the second oxygen stream being supplied by an air separation unit, a liquefied-oxygen tank or a gaseous- or liquefied-oxygen pipeline; transporting at least a part of the overall oxygen stream to the combustion chamber and using said at least a part of the overall oxygen stream as oxygen-rich oxidant in the combustion chamber, said at least a part of the overall oxygen stream being heated to a temperature TOf upstream of the combustion chamber in which TOf>TO2, wherein at least a part of the fuel incinerated in the combustion chamber is preheated upstream of the combustion chamber by heat exchange with the stream of oxygen-depleted air resulting from the oxygen production unit.

2. The heating process of claim 1, in which the stream of hot air exhibits a temperature TA1 of 700 C. to 1000 C.

3. The process of claim 1, in which the stream of hot air exhibits a pressure PA1 of 1 bar ab to 6 bar ab at the inlet of the oxygen production unit.

4. The process of claim 1, in which the portion of oxygen extracted from the at least a part of the stream of hot air corresponds to between 10% and 100% of the oxygen present in said at least a part of the stream of hot air.

5. The process of claim 1, in which the temperature TA2 of the stream of oxygen-depleted air is from 400 C. to 750 C.

6. The process of claim 1, in which the first oxygen stream corresponds to between 90 vol % and 15 vol % of the overall oxygen stream.

7. The process of claim 1, in which the second oxygen stream is also supplied by a Pressure Swing Adsorption unit or a Vacuum Pressure Swing Adsorption unit.

8. The process of claim 1, in which the at least a part of the overall oxygen stream is heated to a temperature TOf between 250 C. and 620 C. upstream of the combustion chamber.

9. The process of claim 1, in which the at least a part of the overall oxygen stream is heated upstream of the combustion chamber by heat exchange with the stream of oxygen-depleted air resulting from the oxygen production unit.

10. The process of claim 1, in which the combustion chamber is: a melting chamber for the melting of vitrifiable material; a calcination chamber; or a steel reheating chamber.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a schematic of an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(2) The invention and its advantages will be better understood in the light of the example below of a process according to the invention and of an installation suitable for the implementation of such a process, reference being made to FIG. 1, which is a diagrammatic representation of such an installation for the melting of glass suitable for the implementation of the process according to the invention.

(3) Said installation comprises a combustion chamber 100 of a furnace, more particularly a glass melting or melting/refining chamber, provided with one or more burners 200 suitable for the combustion of a preheated oxygen-rich fuel.

(4) The installation also comprises a system for distributing oxygen-rich oxidant for supplying said burners 200 with oxidant, and also a system for distributing fuel for supplying said burners 200 with fuel (for example, natural gas).

(5) Although just one burner is represented in the FIGURE, the combustion chamber typically comprises several burners, and even a large number of burners, for example in the case of a melting furnace of float type.

(6) The flue gases generated by the combustion are discharged from the combustion chamber 100 and sent to a circuit for discharge of the flue gases 11.

(7) One or more heat exchangers 10, referred to as primary exchangers, are placed on the circuit for discharge of the flue gases 11 downstream of the combustion chamber 100. In the primary exchanger 10, a part of the residual heat from the discharged flue gases is transferred to a stream of air 21, with, on the one hand, a stream of hot air 22 and, on the other hand, a stream of tempered discharged flue gases 12 being obtained.

(8) The hot air reaches a temperature of the order of 700 C. and up to 900 C., indeed even up to 950 C., at the outlet of the primary exchanger 10.

(9) The stream of hot air 22 is thus brought to a level of temperature at which the extraction of the oxygen over an ITM can be carried out on an industrial scale. It is at a pressure close to atmospheric pressure.

(10) This stream of hot air 22 is introduced into an unit for the production of oxygen by extraction by means of a ceramic ITM 20 with a capacity of 1 to 100 tonnes of oxygen per day.

(11) At these pressures and with a suitable membrane surface area, the extraction output is, for example, of the order of 50%.

(12) Thus, a first oxygen stream 50 and also a stream of oxygen-depleted air 23 are obtained at the outlet of the production unit 20.

(13) The first oxygen stream 50 produced from an ITM is hot, with a temperature TO1 of the order of 900 C. This hot oxygen 50 is directly injected into a system for distribution of oxygen, where it is mixed with colder oxygen 60 resulting from another source of oxygen (such as an ASU (Air Separation Unit), a VSA (Vacuum Swing Adsorption) unit, a LOX (liquid oxygen) tank or a gaseous oxygen circuit).

(14) An overall oxygen stream 70, containing from 20 to 25 vol % (and up to 50 vol %) of oxygen resulting from the ITM oxygen production unit and from 75 to 80 vol % (and down to 50 vol %) of oxygen resulting from the other oxygen source, is thus obtained.

(15) The hot oxygen produced from an ITM is thus cooled without loss of energy for the installation and can without risk be transported in the oxygen distribution system, the materials of which do not have to withstand the highly aggressive conditions of the very-high-temperature oxygen.

(16) The mixture of oxygen from different sources thus obtained is then used as oxygen-rich oxidant to generate the combustion of the fuel in the combustion/melting chamber 30.

(17) According to the invention, it is possible to optimize the configuration of the glass melting installation by positioning the oxygen production unit or units 20 at the most appropriate spot, even if this is at a distance from the burners 200 of the combustion chamber 100, and it is not necessary to use, for the transportation of the overall oxygen stream 70, materials, generally very expensive materials, which withstand the high-temperature oxygen.

(18) In the embodiment illustrated, the production of oxygen by an ITM is integrated with a technology for preheating oxygen and the fuel, for example natural gas, for supplying the oxy-fuel combustible burners 200 of the combustion chamber 100 of the glass melting installation.

(19) A similar technology for preheating oxygen is known in particular from U.S. Pat. No. 6,071,116.

(20) The oxygen-depleted air 23 resulting from the oxygen production unit 20, which exhibits a temperature TA2 of the order of 450 C., is channeled to secondary heat exchangers 31 and 32.

(21) In the first secondary exchanger 31, a part of the oxygen-depleted air 23 is used for the preheating of the fuel 25, for example natural gas, upstream of the burners 200 of the combustion chamber 100. A stream of preheated fuel 26, which is supplied to the burners 200, and a first tempered stream of oxygen-depleted air 27 are obtained.

(22) Similarly, in the second secondary exchanger 32, a part of the oxygen-depleted air 23 is used for the preheating of at least a part of the overall oxygen stream 70 upstream of said burners 200. A stream of preheated oxygen 71, which is supplied to the burners 200, and a second tempered stream of oxygen-depleted air 28 are obtained.

(23) Just one first secondary exchanger 31 and just one second secondary exchanger 32 are shown in FIG. 1. However, the installation can comprise several first secondary exchangers 31 and several second secondary exchangers 32. In particular, when the combustion chamber comprises a large number of burners 200, the installation can comprise a number of first secondary exchangers 31 and a number of second secondary exchangers 32, each heat exchanger 31 and 32 supplying a limited number of burners 200, indeed even just one burner 200. This makes it possible in particular to limit the pipelines for the transportation of preheated fuel or preheated oxygen respectively.

(24) Although, according to the invention, the oxygen produced from an ITM is cooled by mixing it with oxygen from another source, the invention nevertheless makes it possible, to have a temperature of the oxygen (oxygen mixture or overall oxygen stream) at the inlet of the secondary exchanger 32, of typically approximately 300 C., and thus to reduce the size and the cost of the secondary exchanger(s) 32 for the preheating of the oxygen.

(25) The present invention thus makes it possible to use the residual heat from the flue gases discharged from the combustion chamber 100 for the production of oxygen and for the preheating of the fuel and of an oxygen-rich oxidant, to optimize the configuration of the installation and to limit the use of materials which have to withstand hot oxygen.

(26) While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

(27) The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

(28) 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.

(29) Providing in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

(30) Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

(31) 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.

(32) All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.