METHOD AND DEVICE FOR HARVESTING INNER ENERGY FROM EXHAUST GASES

Abstract

In a thermochemical method, a syngas comprising oxygen is combusted in a furnace, thereby producing a hot exhaust gas. The exhaust gas is subsequently discharged into the surroundings while the inner energy of the exhaust gas is at least partly used to carry out a reformation reaction. For this purpose, steam together with a hydrocarbon-containing fuel and an oxygen-containing gas are supplied to a reformer and converted into syngas in an endothermic reaction using inner energy of the exhaust gas. The heat of the exhaust gas is used in particular to evaporate water and supply same to the reformer in a superheated state. The syngas is then supplied to the furnace as fuel. The invention prevents undesired constituents of the furnace atmosphere, in particular sulfur compounds, from being supplied to the reformer.

Claims

1. A process for recovering internal energy from hot exhaust gases in which a hydrocarbon-containing fuel and steam are fed to a reformer, in which a synthesis gas containing carbon monoxide and hydrogen is produced in an endothermic reforming reaction and the synthesis gas is then fed to a furnace, in which it is combusted with an oxygen-containing oxidizing agent, wherein a hot exhaust gas containing carbon dioxide and steam is produced, and the internal energy contained in the exhaust gas is at least partially used to carry out the endothermic reforming reaction in the reformer, wherein the exhaust gas is completely discharged and the steam used in the reforming reaction is generated from water which is supplied from a feed line, evaporated in an evaporator using internal energy of the exhaust gas and is then fed to the reformer.

2. The process as claimed in claim 1, wherein an oxygen-containing gas is fed to the reformer, which is used in the reforming reaction to generate the synthesis gas.

3. The process as claimed in claim 2, wherein internal energy of the exhaust gas from the furnace is at least partially used for heating the fuel and/or the steam and/or the oxygen-containing gas prior to the respective feeding thereof to the reformer.

4. The process as claimed in claim 1, wherein the internal energy of the exhaust gas from the furnace is at least partially transferred to the reactants of the reforming reaction present in the reformer in a heat exchanger arranged in the reformer.

5. The process as claimed in claim 1, wherein the reaction temperature in the reformer, or in a reactor or a functional section of the reformer, is between 700° C. and 900° C., preferably between 750° C. and 800° C.

6. The process as claimed in claim 1, wherein a fuel consisting at least predominantly of methane is used as fuel and the ratio of the mass flows of the reactants fed to the reformer for the reforming reaction is [ṅ(CH.sub.4)/ṅ(O.sub.2)/ṅ(H.sub.2O)] = [1/0-0.6/0.5-1.5], preferably [ṅ(CH.sub.4)/ṅ(O.sub.2)/ṅ(H.sub.2O)] = [1/0.1-0.5/0.6-1.2].

7. The process as claimed in claim 1, wherein a catalyst from the group of iron, cobalt, nickel or platinum is provided in the reformer.

8. A device for recovering internal energy from hot exhaust gases, the device having: a reformer connected to a feed line for a hydrocarbon-containing fuel and a feed line for oxygen; a furnace which is equipped with: a feed line for an oxygen-containing oxidizing agent; an exhaust gas line for discharging exhaust gas from the furnace; and a feed line connecting the reformer to the furnace for feeding a synthesis gas produced in the reformer into the furnace; and at least one heat exchanger for transferring internal energy of the exhaust gas to reaction products in the reformer; wherein the exhaust gas line is thermally connected to an evaporator, which is fluidically connected to a water feed line fluidically separated from the exhaust gas line and to a feed line for steam opening into the reformer, and has a heat exchanger surface for evaporating the water supplied via the water feed line by thermal contact with the exhaust gas supplied from the exhaust gas line.

9. The device as claimed in claim 8, wherein a heat exchanger is provided in the reformer for transferring internal energy from the exhaust gas to the reaction products present in the reformer.

10. The device as claimed in claim 9, wherein an indirect heat exchanger connected to the exhaust gas line is provided in the reformer, at which the reaction products of the reforming reaction in the reformer can be brought continuously into thermal contact with the exhaust gas from the furnace.

11. The device as claimed in claim 8, wherein a multi-part reformer consisting of a plurality of reactors and/or functional sections is used as the reformer, wherein the reactors and/or functional sections are at least partially equipped with a heat exchanger for transferring internal energy from the exhaust gas to the respective reaction products and/or with a feed line for steam and/or a feed line for oxygen-containing oxidizing agent.

12. The device as claimed in claim 8, further comprising a control system operatively connected to the feeds by means of which the mass flows of the reactants of the reforming reaction in the reformer can be varied.

13. The device as claimed in claim 8, wherein the furnace is a glass melting furnace.

Description

DESCRIPTION OF THE DRAWING

[0037] A working example of the invention will be explained in more detail on the basis of the figure. The single figure (FIG. 1) schematically shows a diagram of the mode of operation of a device according to the invention.

DETAILED DESCRIPTION

[0038] The device 1 shown in FIG. 1 comprises a furnace 2, for example a glass melting furnace, which is equipped with a feed line 3 for a synthesis gas and a feed line 4 for an oxidizing agent, and with an exhaust gas line 5 for discharging the exhaust gas produced in the furnace 2 during combustion of the synthesis gas with the oxidizing agent. The synthesis gas is produced in a reformer 6, which is flow-connected to the furnace 2 via the feed line 3. The reformer 6 is in flow connection with a feed line 7 for a hydrocarbon-containing fuel, such as methane, natural gas, fuel oil or the like, with a feed line 8 for an oxygen-containing gas and a feed line 9 for steam.

[0039] The oxygen-rich gas used in the working example shown here is the same gas that is used as an oxidizing agent in the furnace 2, for example oxygen having a purity of 95% by volume or above. For this reason, the feed lines 4, 8 are connected to each other and to a common source not shown here, for example an oxygen tank or a pipeline; however, it is also conceivable that different oxygen-containing gases are used in the furnace 2 and in the reformer 6; in this case, the feed lines 4, 9 are connected to different sources.

[0040] In the working example shown here, the feed lines 7, 8, 9 open together into a mixer 11, from which a common feed line 12 transports the gas mixture into the reformer 6; in the scope of the invention, however, it is also conceivable that the feed lines 7, 8, 9 open directly into the reformer 6.

[0041] In order to increase the efficiency of the reaction taking place in the reformer 6, this is equipped with a catalyst in a manner not shown here, which is nickel for example, which is applied to an inert support material in the form of bulk material.

[0042] During operation of the device 1, a synthesis gas containing carbon monoxide and hydrogen is produced in the reformer 6 from the reactants methane, oxygen and steam in an endothermic reforming reaction, the synthesis gas being fed to the furnace 2 via the feed line 3 and combusted in the furnace 2 with the oxidizing agent supplied via the feed line 4. The resulting exhaust gases are discharged via the exhaust gas line 5. They contain carbon dioxide and steam, but may also contain other constituents such as oxygen. The temperature of the exhaust gases is, for example, 1000° C. to 1650° C., preferably 1400° C. to 1500° C.

[0043] In order to be able to use the heat of the exhaust gas, the exhaust gas line 5 passes through a series of heat exchangers 13, 14, 15, 16 downstream of the furnace 2, each of which is, for example, a tube, gap or tube-basket recuperator. In a first heat exchanger 13, heat contact takes place in the reformer 6 at a heat exchanger surface between the exhaust gas passed through the exhaust gas line 5 with the reaction products, thereby providing at least part of the heat required for the endothermic reforming reaction. The continuous supply of heat from the exhaust gas to the heat exchanger surface in the heat exchanger 13 enables the operation of the reformer 6 as a recuperator. The still hot exhaust gas is then fed to an evaporator 14. In the evaporator 14 there is a heat exchanger surface 20 on which at least part of the internal energy present in the exhaust gas is transferred to water, which is conveyed to the evaporator 14 via a water feed line 17. The water evaporates at the heat exchanger surface 20 and is then introduced into the reformer 6 in the form of superheated steam via the feed line 9. Optionally, the exhaust gas then passes through heat exchangers 15, 16, in which preheating of the two remaining reactants, oxygen and fuel, takes place.

[0044] In none of the heat exchangers 13, 14, 15, 16 is there any material mixing of exhaust gas from the exhaust gas line with any of the media conveyed in the feed lines 7, 8, 9, 17; rather, the exhaust gas cooled in the heat exchangers 13, 15, 16 and the evaporator 14 is discharged from the exhaust gas line 7 into the ambient atmosphere via a chimney 19 after passing through a purification stage 18 or is fed to some other use.

[0045] The mass flow rates of the reactants supplied via the feed lines 7, 8, 9 can be varied and the ratios can be adjusted to the conditions by means of a control system not shown here, for example in order to bring about the most complete possible conversion of the fuel in the reformer 6 and at the same time to reduce or completely prevent the tendency to form carbon deposits.

[0046] Due to the fluidic separation between the furnace exhaust gas on the one hand and the reactants of the reforming reaction on the other hand, the device 1 reliably prevents harmful constituents of the exhaust gas, for example sulfur compounds, from accumulating in the reformer and causing damage therein, for example to the catalyst bed. By transferring internal energy from the furnace exhaust gases to the reaction products of the reforming reaction at the heat exchangers 13, 15, 16 and the evaporator 14, a high energy efficiency is nevertheless achieved.

LIST OF REFERENCE SIGNS

[0047] 1. Device [0048] 2. Furnace [0049] 3. Feed line [0050] 4. Feed line [0051] 5. Exhaust gas line [0052] 6. Reformer [0053] 7. Feed line (for fuel) [0054] 8. Feed line (for oxygen) [0055] 9. Feed line (for water) [0056] 10. - [0057] 11. Mixer [0058] 12. Common feed line [0059] 13. Heat exchanger [0060] 14. Evaporator [0061] 15. Heat exchanger [0062] 16. Heat exchanger [0063] 17. Water feed line [0064] 18. Purification stage [0065] 19. Chimney [0066] 20. Heat exchanger surface