METHOD FOR PURIFYING A RAW GAS STREAM AND PURIFICATION DEVICE

Abstract

In order to provide a method for the purification of a raw gas stream containing water vapour that is simple and cost-efficient to perform, it is proposed that the method should comprise the following: feeding the raw gas stream to a reforming region in which contaminants in the raw gas stream react chemically with the water vapour in the raw gas stream, as a result of which a reformed raw gas stream is obtained; feeding the reformed raw gas stream and an oxidising agent stream to an oxidation region in which constituent parts of the reformed raw gas stream react chemically with oxidising agent of the oxidising agent stream, as a result of which a clean gas stream is obtained. Moreover, optionally a closed-loop control of the oxygen content is provided. Further, it is optionally provided for the clean gas stream to be fed to a condenser, as a result of which the volumetric flow of the clean gas stream is reduced and/or as a result of which energy can be recovered and used for pre-heating the oxidising agent and for other production processes.

Claims

1. A method for the purification of a raw gas stream containing water vapour and having organic contaminants, in particular for the purification of waste steam, wherein the method comprises the following: feeding the raw gas stream to a reforming region in which contaminants in the raw gas stream react chemically with the water vapour in the raw gas stream, as a result of which a reformed raw gas stream is obtained; feeding the reformed raw gas stream and an oxidising agent stream to an oxidation region in which constituent parts of the reformed raw gas stream react chemically with oxidising agent of the oxidising agent stream, as a result of which a clean gas stream is obtained.

2. A method according to claim 1, wherein the chemical reaction in the reforming region is an allothermal and/or hydrothermal gasification, and/or in that the chemical reaction in the oxidation region is a reaction with an external source of energy and/or an autothermal oxidation.

3. A method according to claim 1, wherein the method is carried out by means of a purification device that comprises a plurality of flow chambers, wherein a first of the flow chambers at least some of the time forms the reforming region, and wherein a second of the flow chambers at least some of the time forms a heat storage region to which the clean gas stream is fed.

4. A method according to claim 3, wherein the purification device comprises at least a third flow chamber that at least some of the time forms a pre-heating region to which the oxidising agent stream is feedable for the purpose of being pre-heated before the oxidising agent stream is fed to the oxidation region.

5. A method according to claim 3, wherein the raw gas stream and/or the clean gas stream and/or the oxidising agent stream is/are fed alternately in each case to different flow chambers, such that the flow chambers respectively alternately form the reforming region and/or the heat storage region and/or the pre-heating region.

6. A method according to claim 1, wherein the raw gas stream has an oxidising agent content, in particular an oxygen content, of less than 5% by volume.

7. A method according to claim 1, wherein in the reforming region, the raw gas stream is heated to at least approximately 800° C.

8. A method according to claim 1, wherein the raw gas stream in the reforming region and/or the clean gas stream in a heat storage region and/or the oxidising agent stream in a pre-heating region are each guided through a respective heat storage unit of a heat storage device, wherein one or more or all of the heat storage units are formed by or comprise in particular ceramic flow bodies.

9. A method according to claim 1, wherein a heat exchanger and/or a heating device is/are used to heat the raw gas stream before it is fed to the reforming region and/or to heat the oxidising agent stream before and/or after it is fed to a pre-heating region.

10. A method according to claim 1, wherein the clean gas stream is first fed to a heat storage region and then to a downstream heat exchanger, wherein the clean gas stream is cooled by means of the heat exchanger in particular sufficiently for condensate to form and as a result for heat that is still in the clean gas stream first to be transferred to the heat exchanger and/or made usable in some other way.

11. A method according to claim 1, wherein the oxidising agent stream is fed to the oxidation region such that it bypasses the reforming region and/or independently of a flow path of the raw gas stream.

12. A method according to claim 1, wherein the mass flow and/or the volumetric flow of the oxidising agent stream are controlled by open and/or closed-loop control depending on a mass flow and/or volumetric flow of the raw gas stream and/or depending on a degree of contamination in the raw gas stream and/or depending on a calorific value of the raw gas stream and/or depending on an oxygen content in the clean gas stream, in particular such that a predetermined content of oxygen/oxidising agent and/or a predetermined temperature are achieved in the oxidation region and/or in a clean gas discharge line.

13. A method according to claim 1, wherein the clean gas stream is fed to a heat exchanger, in particular a condenser, and in that water vapour in the clean gas stream is condensed by means of the heat exchanger, in particular by means of the condenser.

14. A purification device for the purification of a raw gas stream containing water vapour, in particular for the purification of waste steam, wherein the purification device comprises the following: a raw gas feed for feeding the raw gas stream to a reforming region of the purification device, in which contaminants in the raw gas stream react chemically with the water vapour in the raw gas stream, as a result of which a reformed raw gas stream is obtainable; and an oxidising agent feed for feeding an oxidising agent stream to an oxidation region of the purification device, in which constituent parts of the reformed raw gas stream react chemically with oxidising agent of the oxidising agent stream, as a result of which a clean gas stream is obtainable.

15. A purification device according to claim 14, wherein the purification device comprises a plurality of flow chambers, which are in particular provided with heat storage material, and an open-loop control device, wherein the purification device is configured to be put into different operating modes by the control device, wherein, in a first purification mode: the raw gas stream is configured to be fed, by means of the raw gas feed, at least to a first of the flow chambers, and the clean gas stream is configured to be discharged, by means of a clean gas discharge line, from at least a second of the flow chambers; and wherein, in a second purification mode: the raw gas stream is configured to be fed, by means of the raw gas feed, to the at least one second flow chamber, and the clean gas stream is configured to be discharged, by means of the clean gas discharge line, from the at least one first flow chamber.

16. A purification device according to claim 14, wherein the purification device comprises a plurality of flow chambers through which the raw gas stream, the clean gas stream and/or the oxidising agent stream are configured to flow, wherein the flow chambers each comprise a heat storage unit, wherein one or more or all of the heat storage units has a layered structure comprising different materials, in particular different heat storage materials.

17. A purification device according to claim 14, wherein the purification device comprises a heat exchanger that is arranged in the clean gas discharge line and takes the form of a condenser and by means of which water vapour in the clean gas stream is condensable such that in particular a volume and/or volumetric flow of the clean gas stream in the clean gas discharge line is reducible.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0076] FIG. 1 shows a schematic illustration of a first embodiment of a purification device for the purification of raw gas that contains water vapour and has organic contaminants, having closed-loop control of the oxygen content in the clean gas stream;

[0077] FIG. 2 shows a schematic illustration of the purification device, corresponding to FIG. 1, in a purifying and flushing mode;

[0078] FIG. 3 shows a schematic illustration of the purification device, corresponding to FIG. 1, in the purifying mode; and

[0079] FIG. 4 shows a schematic section through the structure of a heat storage unit of a heat storage device of the purification device.

[0080] Like or functionally equivalent elements are provided with the same reference numerals in all the Figures.

DETAILED DESCRIPTION OF THE DRAWINGS

[0081] A purification device that is illustrated in FIGS. 1 to 4 and is designated 100 as a whole is used in particular for the purification of raw gas.

[0082] The purification device 100 is particularly suitable for the purification of waste steam, which is also known as fumes or vapour.

[0083] The purification device 100 comprises in particular a regenerative thermal oxidiser 102 for the thermal conversion of odorous substances and other contaminants in the waste steam.

[0084] Preferably, the purification device 100 comprises a reforming region 104, a heat storage region 106 and a pre-heating region 108.

[0085] The reforming region 104 is configured to have the raw gas that is to be purified fed to it by means of a raw gas feed 110 of the purification device 100.

[0086] Preferably, the pre-heating region 108 is configured to have oxidising agent and/or flushing gas fed to it by way of an oxidising agent feed 112 and/or a flushing gas feed 114.

[0087] Further, there is preferably provided a clean gas discharge line 116 of the purification device 100, by way of which clean gas generated from the raw gas is dischargeable.

[0088] Thus, the clean gas discharge line 116 is in particular an exhaust gas discharge line 118 of the purification device 100.

[0089] In particular, the clean gas discharge line 116 adjoins or comprises the heat storage region 106.

[0090] A plurality of heat exchangers 120 of the purification device 100 preferably serve to heat or cool gas streams in order ultimately to optimise the energy efficiency of the purification device 100.

[0091] Moreover, there is preferably provided a heat storage device 122 of the purification device 100, by means of which the heat generated in the purification device 100 is temporarily storable and is re-usable for optimised operation of the purification device 100.

[0092] For this purpose, the heat storage device 122 comprises in particular a plurality of heat storage units 124.

[0093] The purification device 100 comprises an oxidation region 126 that adjoins the reforming region 104 and the pre-heating region 108, and opens in particular into the heat storage region 106.

[0094] In the embodiment of the purification device 100 that is illustrated in FIGS. 1 to 4, the reforming region 104, the pre-heating region 108 and the heat storage region 106 are not fixed, but are formed by different flow paths 128 of the purification device 100 in a manner varying over time, depending on the locations of feeding in the raw gas and the oxidising agent and the discharging of clean gas.

[0095] Here, each flow path 128 comprises a heat storage unit 124 of the heat storage device 122, with the result that heat is feedable to or removable from the flow paths 128, depending on the respective feed or discharge of gas.

[0096] One or more optional heating devices of the purification device 100 may contribute to optimising operation of the purification device 100, in addition to the heat storage device 122 and/or in addition to the heat exchangers 120.

[0097] As can be seen in particular from a comparison of FIGS. 2 and 3, flow along the flow paths 128 is in different directions, depending on the respective operating mode (purification mode) of the purification device 100.

[0098] For optimised use and/or heat transfer, the heat storage units 124 in the flow chambers 128 are preferably provided with a layered structure.

[0099] As can be seen from FIG. 4, in this case in particular optimisation of the infeed and guiding through of raw gas may be provided. For this purpose, in particular a first layer 130a formed for example from a dense-burned ceramic material is provided.

[0100] A second layer 130b, adjoining the first layer 130a, is preferably formed from aluminium oxide china or a similar ceramic material, and has a greater density than the material of the first layer 130a. As a result, a region of high heat storage capacity can be created.

[0101] A third layer 130c, adjoining the second layer 130b, comprises for example a mullite material that has a reaction-accelerating action and contributes to optimising the chemical kinetics within the flow chamber 128.

[0102] Finally, a fourth layer 130d, adjoining the third layer 130c, preferably serves to optimise inflow to the oxidation region 126, which adjoins the heat storage unit 124. For this purpose, the fourth layer 130d has a bulk material comprising a turbulence-generating material, for example saddle-type bodies.

[0103] During the flow of raw gas through the heat storage unit 124, illustrated in FIG. 4, the heat storage unit 124 serves as a reforming region 104 of the purification device 100.

[0104] When this same heat storage unit 124, or a further heat storage unit 124 of identical construction, is used as a heat storage region 106, the direction of flow is reversed.

[0105] The purification device 100 preferably comprises an oxidising agent sensor 140, in particular for the detection of oxygen, which, by open or closed-loop control by means of a control unit 141, controls the volumetric flow of the oxidising agent fed by way of the oxidising agent feed 112.

[0106] For the purpose of briefly flushing the oxidising agent, preferably one common or two individual switchover units 115 is/are used.

[0107] The embodiment of the purification device 100 that is illustrated in FIGS. 1 to 4 preferably functions as follows:

[0108] A raw gas, taking the form for example of waste steam, is guided by way of the raw gas feed 110 to a first flow chamber 128a, which forms the reforming region 104.

[0109] Arranged in this first flow chamber 128a is a heat storage unit 124, for example corresponding to the embodiment illustrated schematically in FIG. 4.

[0110] Before the raw gas is fed in, this heat storage unit 124 has been charged with heat such that the raw gas that is then fed in is heated by the heat storage unit 124. In particular, a temperature of at least approximately 750° C., for example at least 800° C., is achieved.

[0111] At these high temperatures, the constituent parts of the raw gas are broken down, with the result that in particular from hydrocarbons and water a reformed raw gas—for example water gas—is produced. In particular here, long-chain hydrocarbons and hydrocarbons of low volatility are to a very great extent converted to methane, carbon monoxide, hydrogen and other readily combustible substances.

[0112] The raw gas has a very low oxygen content of less than 5% by volume, in particular at most approximately 1% by volume, with the result that the readily combustible constituent parts do not oxidise in the reforming region 104 but can be conveyed on from the reforming region 104 to the oxidation region 126.

[0113] In particular here, the entire raw gas stream that has passed through the reforming region 104 is fed to the oxidation region 126 as a reformed raw gas stream.

[0114] In the oxidation region 126, the reformed raw gas stream meets a gas stream that contains oxidising agent, in particular an oxidising agent stream.

[0115] The oxidising agent stream is in particular air or an air mixture, or a process gas that contains oxidising agent, in particular containing oxygen.

[0116] The oxidising agent stream is fed by way of the oxidising agent feed 112 to a third flow chamber 128c. Here, care is taken that the temperature of the oxidising agent stream is at least approximately 100° C. or above, for example at least 100° C., preferably at least approximately 110° C. This preferably enables undesired condensation of water to be avoided.

[0117] The oxidising agent stream can be heated by means of an optional heating device and/or one or more heat exchangers 120. This operation is preferably a pre-heating.

[0118] Only once it is in the flow chamber 128c is the oxidising agent stream heated to a desired temperature so that it can be fed to the oxidation region 126. The target temperature of the oxidising agent stream here is preferably at least 750° C., for example at least approximately 800° C., in particular approximately 850° C.

[0119] This heating to the target temperature in the flow chamber 128 is in particular achieved by the third flow chamber 128c also having a heat storage unit 124, for example according to the embodiment illustrated in FIG. 4. This heat storage unit 124 is preferably heated before the oxidising agent stream is fed in, for example using the clean gas stream.

[0120] The oxidising agent stream preferably has an oxygen content of at least approximately 15% by volume, for example at least approximately 18% by volume, preferably approximately 21% by volume.

[0121] Bringing together the heated, reformed raw gas stream and the heated oxidising agent stream in the oxidation region 126 results in oxidation of the combustible constituent parts of the reformed raw gas stream in the oxidation region 126, as a result of which in particular hydrocarbons, carbon monoxide and hydrogen are removed from the reformed raw gas stream by oxidation, in particular giving carbon dioxide and water.

[0122] As a result, a clean gas stream is ultimately obtainable and is discharged from the oxidation region 126 through a second flow chamber 128b, which forms the heat storage region 106.

[0123] In the heat storage region 106, the clean gas stream emits at least some of its heat to the heat storage unit 124 arranged in the second flow chamber 128b. This heat storage unit 124 is preferably a heat storage unit 124 corresponding to the embodiment illustrated in FIG. 4.

[0124] After flowing through the second flow chamber 128b forming the heat storage region 106, the clean gas is discharged by way of the clean gas discharge line 116. By means of an optional heat exchanger 120, the quantity of heat still remaining in the clean gas may preferably be at least partly discharged from the clean gas stream and hence made useful in some other way.

[0125] The above-described purification operation of the purification device 100 (for example according to FIG. 1, which illustrates in particular normal operation) may preferably be maintained until the quantities of heat stored in the heat storage units 124 of the first and third flow chambers 128a, 128c are no longer sufficient for adequate heating of the raw gas stream and/or the oxidising agent stream, or are no longer sufficient for an adequate reaction in the reforming region 104. The point in time at which switchover is performed is preferably determined by measurement, calculation or another determination of the energy content in the flow chambers, in particular by carrying out an energy comparison of the flow chambers using a control module, for example the control module XtraBalance.

[0126] When adequate heating is no longer possible, the purification device 100 is put, preferably by means of an open-loop control device 115, into a flushing mode (see FIG. 2), in which for example by means of a flushing gas feed 114 ambient air is briefly fed to the third flow chamber 128c. Raw gas and flushing gas are fed to the first flow chamber 128a, and/or clean gas is fed to the second flow chamber 128b. In particular, the flushing gas, which is for example ambient air, is used to achieve cleaning of the heat storage units 124, in order ultimately to avoid an undesired emission of odorous substances or harmful gases at the time of a subsequent flow reversal.

[0127] After the flushing procedure, the raw gas is no longer fed to the first flow chamber 128a but for example to the second flow chamber 128b, which consequently is no longer the heat storage region 106 but now forms the reforming region 104 (see FIG. 3).

[0128] Finally, because of the infeed of the clean gas stream, the heat storage unit 124 arranged in the second flow chamber 128b has previously been heated to a high temperature and thus now forms a sufficient heat source for carrying out the reforming procedure for reforming the raw gas stream.

[0129] The first flow chamber 128a, which previously formed the reforming region 104, now correspondingly forms the flushing region 108, with the result that the clean gas stream generated in the oxidation region 126 is now discharged by way of the third flow chamber 128c.

[0130] This heats the heat storage unit 124 that is arranged in the third flow chamber 128c and thus prepares it for later use as a reforming region 104 or indeed as a pre-heating region 108.

[0131] In addition to the operating modes of the purification device 100 that are illustrated in FIGS. 2 and 3, numerous further operating modes may be implemented. In particular, the third flow chamber 128c, which in FIGS. 1, 2 and 3 forms the pre-heating region 108, is also used for guiding away/discharging the clean gas at regular intervals (see FIG. 3) and hence prepared for re-use as a pre-heating region 108 or indeed a reforming region 104.

[0132] The oxidising agent feed 112 is controlled in particular depending on an oxygen content in the clean gas stream. In particular, the quantity of oxidising agent, in particular the volumetric flow of oxidising agent and/or the mass flow of oxidising agent, is preferably controlled by open and/or closed-loop control such that reliable oxidation of the substances in the reformed raw gas stream is produced in the oxidation region 126. Performance of the appropriate closed-loop control may be for example temperature-dependent, oxygen-dependent or indeed dependent on a composition of the clean gas stream. Moreover, it goes without saying that numerous further open-loop and/or closed-loop control variables are conceivable.

[0133] Because a reformed raw gas stream is produced from a raw gas stream in the described purification device 100 before the reformed raw gas stream undergoes chemical reaction with the oxidising agent, the purification device 100 may be operated particularly simply and cost-efficiently. Moreover, additional devices such as separators and scrubbers can be avoided.

[0134] In a further development, it may moreover be provided for the clean gas stream to be fed to a condenser, in particular a heat exchanger 120 that is arranged in the clean gas discharge line 116 and takes the form of a condenser. As a result, preferably the volume of the clean gas stream can be reduced, in particular by condensing out the water vapour in the clean gas stream. Thus, a negative pressure, below the ambient pressure, can preferably be generated in the condenser, as a result of which the energy requirement for conveying the raw gas stream and the clean gas stream for the raw gas purification can be reduced.