PROCESS AND PLANT FOR PRODUCING CO-RICH SYNTHESIS GAS BY PARTIAL OXIDATION

Abstract

Proposed are a process and a plant for producing a hydrogen- and carbon oxides-containing synthesis gas by partial noncatalytic oxidation of a fluid or fluidizable carbon-containing input stream of fossil origin as a first input stream in the presence of an oxygen-containing oxidant and optionally a moderator to obtain a CO-rich raw synthesis gas. According to the invention a second input stream including a pyrolysis oil obtained from biomass is reacted simultaneously with the first input stream in the noncatalytic partial oxidation.

Claims

1. A process for producing a hydrogen- and carbon oxides-comprising raw synthesis gas by simultaneous noncatalytic partial oxidation of a fluid or fluidizable carbon-containing input stream of fossil origin as a first input stream and a second input stream comprising a pyrolysis oil obtained from biomass with an oxygen-containing oxidant in a common noncatalytic partial oxidation reactor, comprising the steps of: (a) providing the first input stream in fluid or fluidized form, providing the second input stream in liquid, conveyable form, providing an oxidant stream, (b) providing a partial oxidation reactor comprising a reaction chamber having at least one inlet and an outlet, at least one burner arranged at the at least one inlet of the reaction chamber and a cooling zone arranged downstream of the outlet of the reaction chamber and in fluid connection therewith, (c) introducing the first input stream, and the oxidant stream into the reaction chamber via the at least one burner and introducing the second input stream into the reaction chamber via the at least one burner or via a feed conduit separate from the at least one burner, (d) at least partially reacting the first input stream and the second input stream with the oxidant stream under partial oxidation conditions in the burner and/or in the reaction chamber arranged downstream of the burner to afford a hot raw synthesis gas stream, (e) discharging the hot raw synthesis gas stream from the reaction chamber and introducing same into the cooling zone, (f) discharging the cold raw synthesis gas stream from the cooling zone and from the partial oxidation reactor for further processing or further treatment.

2. The process according to claim 1, wherein the cooling zone is configured as a quench or as a waste heat boiler or as a combination of both.

3. The process according to claim 1, wherein the cooling zone is configured as a quench and that the process further comprises the steps of: (e1) subjecting the hot raw synthesis gas stream in the cooling zone to a cold, water-containing quench medium stream to obtain a cold raw synthesis gas stream and a stream of hot quench medium, (e2) discharging the hot, liquid quench medium stream from the cooling zone and introducing at least a portion of the hot quench medium stream into a first heat exchanger for cooling the hot quench medium stream by indirect heat exchange against a first coolant to obtain the cold quench medium stream, (e3) discharging the cold quench medium stream from the first heat exchanger and recycling at least a portion of the cold quench medium stream to the cooling zone to form a quench medium stream circuit.

4. The process according to claim 1, wherein the mass flow proportion of the second input stream based on the sum of the mass flows of the first and second input stream is at least 5% by weight.

5. The process according to claim 1 wherein the first input stream has an ash content of at most 5% by weight.

6. The process according to claim 1, wherein the first input stream comprises natural gas, crude oil or at least one liquid or gaseous crude oil descendent product.

7. The process according to claim 1, wherein the first input stream comprises crude oil or at least one liquid crude oil descendent product in each case comprising suspended or fluidized carbon-containing solids particles.

8. The process according to claim 1, wherein the second input stream has an ash content of at most 1% by weight.

9. The process according to claim 1 wherein the second input stream has an oxygen content of at least 10% by weight, in each case based on anhydrous pyrolysis oil.

10. The process according to claim 1, wherein the second input stream is atomized before or during introduction thereof into the reaction chamber.

11. The process according to claim 1, wherein the second input stream is atomized before or during introduction thereof into the reaction chamber, wherein the atomizing medium is: the moderator stream and/or at least a portion of the first input stream if said stream is gaseous.

12. The process according to claim 1, wherein the second input stream is introduced into the reaction chamber via the at least one burner, wherein the second input stream is introduced into the at least one burner via a separate conduit channel and atomized using the atomizing medium and introduced into the reaction chamber in the atomized state.

13. The process according to claim 1, wherein the second input stream is introduced into the reaction chamber separately from the at least one burner via at least one separate feed lance, wherein the second input stream is atomized using the atomizing medium and introduced into the reaction chamber in the atomized state.

14. The process according to claim 1, wherein the mass ratio of the atomizing medium to the second input stream is between more than zero and 1 g/g.

15. A plant for producing a hydrogen- and carbon oxides-comprising raw synthesis gas by simultaneous noncatalytic partial oxidation of a solid, liquid or gaseous carbon-containing input stream of fossil origin as a first input stream and a pyrolysis oil as a second input stream with an oxygen-containing oxidant in a common noncatalytic partial oxidation reactor, wherein the plant comprises the following constituents in fluid connection with one another: (a) a means for providing the first input stream in fluid or fluidized form, means for providing the second input stream in liquid, conveyable form, means for providing the oxidant stream, (b) a partial oxidation reactor comprising a reaction chamber having an inlet and an outlet, at least one burner arranged at the inlet of the reaction chamber and a cooling zone arranged downstream of the outlet of the reaction chamber and in fluid connection therewith, (c) a means for introducing the first input stream, the oxidant stream and the optional moderator stream into the at least one burner and a means for introducing the second input stream into the reaction chamber via the at least one burner or via a feed conduit separate from the at least one burner, (d) a means for discharging a hot raw synthesis gas stream from the reaction chamber and means for introducing same into the cooling zone, (e) a means for discharging a cold raw synthesis gas stream from the partial oxidation reactor.

16. The plant according to claim 15, wherein the cooling zone is configured as a quench or as a waste heat boiler or as a combination of both.

17. The plant according to claim 15, wherein the cooling zone is configured as a quench and the plant also comprises the following constituents: (e1) a means for subjecting the hot raw synthesis gas stream in the cooling zone to a cold, water-containing quench medium stream, (e2) a first heat exchanger, a means for discharging a hot liquid quench medium stream and a cold raw synthesis gas stream from the cooling zone and a means for introducing at least a portion of the hot quench medium stream into the first heat exchanger, (e3) a means for discharging a cold quench medium stream from the first heat exchanger and a means for recycling at least a portion of the cold quench medium stream to the cooling zone to form a quench medium stream circuit.

18. A process for retrofitting an existing plant for noncatalytic partial oxidation of a first, carbon-containing input stream of fossil origin as the first input stream, wherein the existing plant comprises the following constituents: (a) a means for providing the first carbon-containing input stream of fossil origin in fluid or fluidized form, means for providing the oxidant stream, (b) a partial oxidation reactor comprising a reaction chamber having an inlet and an outlet, at least one burner arranged at the inlet of the reaction chamber and a cooling zone arranged downstream of the outlet of the reaction chamber and in fluid connection therewith, (c) a means for introducing the first input stream, the oxidant stream and the optional moderator stream into the at least one burner and means for introducing the second input stream into the reaction chamber via the at least one burner or via a feed conduit separate from the at least one burner, (d) a means for discharging a hot raw synthesis gas stream from the reaction chamber and means for introducing same into the cooling zone, (e) a means for discharging a cold raw synthesis gas stream from the partial oxidation reactor, wherein the existing plant is additionally provided with a feed for a pyrolysis oil as the second input stream, wherein the feed for the second input stream opens into the at least one burner or separately from the at least one burner opens directly into the reaction chamber and the feed is configured such that the second input stream is atomized before or during the introduction thereof into the reaction chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Developments, advantages and possible applications of the invention are also apparent from the following description of working and numerical examples and the drawings. All features described and/or depicted, either in themselves or in any combination, form the invention, regardless of the way they are combined in the claims or the back-references therein.

[0090] FIG. 1 shows an embodiment of a gasification process/a corresponding plant by noncatalytic partial oxidation (POX) according to the prior art,

[0091] FIG. 2 shows an embodiment of a gasification process by noncatalytic partial oxidation (POX) according to the invention,

[0092] FIG. 3 shows an embodiment of a burner for noncatalytic partial oxidation (POX) according to the invention,

[0093] FIG. 4 shows an example of an inventive embodiment of a burner faceplate having a plurality of burners and an injection lance.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0094] In the plant 1 shown schematically in FIG. 1 for synthesis gas production according to the prior art by noncatalytic partial oxidation for example of crude oil or a crude oil descendent product, for example a cracker residue, as a liquid, carbon-containing first input stream, the reaction chamber 10 is supplied via the burner 11 with the first input stream via conduits 13 and 3, with steam as moderator via conduit 2 and with oxygen as oxidant via conduits 14 and 4. The detailed media path is not depicted in the figure; thus a pre-mixing of one or more of the media, for example of the pyrolysis oil or the oxidant or both, with the moderator may be carried out upstream of the burner or in the burner itself, wherein steam or carbon dioxide or mixtures of these substances are used as the moderator.

[0095] The reaction of the first input stream with the oxidant to afford a raw synthesis gas is carried out under partial oxidation conditions in the burner 11 and/or in the reaction chamber 10 arranged downstream of the burner to afford a hot raw synthesis gas stream.

[0096] Via conduit 12 the raw synthesis gas enters the cooling chamber 20 which is configured as a quench. By spraying water which is supplied via conduits 21 and 22 as a cold quench medium stream, said quench instantaneously lowers the temperature of the raw synthesis gas to a temperature between 150° C. and 250° C. at a typical pressure between 25 and 80 bar(a). The thus obtained cooled raw synthesis gas largely freed of solids particles, for example soot or coke particles, is subsequently discharged from the partial oxidation plant via conduit 15 and sent for further processing or further treatment.

[0097] The hot, liquid quench medium optionally laden with solids particles collects in the lower region of the cooling chamber and forms a liquid fill level therein. The hot quench medium is then discharged from the cooling chamber 20 via conduit 24 and passed to the first heat exchanger 30 via conduit 24. If the hot quench medium is discharged at the lowest point of the cooling chamber 20 as shown and it contains a significant proportion of solids particles said medium is advantageously applied to an apparatus for solids separation (not shown) to separate at least a portion of the entrained solids particles before the hot quench medium is passed on to the first heat exchanger 30.

[0098] The first heat exchanger 30 performs a first partial cooling of the hot quench medium in indirect heat exchange against the oxidant stream supplied via conduit 14 as the first coolant which is thus preheated and passed to the burner 11 via conduit 4. The partially cooled quench medium is then passed to a second heat exchanger 40 via conduit 32. The second heat exchanger 40 performs the further partial cooling of the quench medium in indirect heat exchange against the first input stream supplied via conduit 13 as the second coolant which is thus likewise preheated and passed to the burner 11 via conduit 3.

[0099] The cold quench medium is discharged from the second heat exchanger 40 via conduit 42 and, via conduits 44, 22, 21 and pump 23, recycled as cold quench medium to the cooling chamber 20, thus forming a closed quench medium circuit. A small proportion compared to the recirculating mass flow of the quench medium is continuously discharged from the process via conduit 46 to limit contamination of the circulating quench medium by fine solids fractions and undesired dissolved substances. The discharged mass flow of the quench medium is continuously replaced by fresh water via conduit 48.

[0100] The specified choice of the first and the second coolant offers particular advantages: The oxidant less sensitive to overheating encounters the still-hot quench medium stream as the first coolant in the first heat exchanger while the already partially cooled quench medium is further cooled with the hydrocarbons-containing first input stream as the second coolant in the second heat exchanger. In this way the first input stream as a carbon-containing input stream is preheated, but overheating, which can result in undesired side reactions on account of the reactivity of several ingredients, is avoided.

[0101] In the embodiment shown in FIG. 2 of a gasification process by noncatalytic partial oxidation (POX) according to the invention all depicted elements and the reference numerals therefor correspond to those in FIG. 1 to the extent that they have already been mentioned in connection with the embodiment elucidated therein. Added in novel and inventive fashion are conduits 5 and 49 by means of which a pyrolysis oil as a second input stream is passed to conduit 2 and on to the burner 11. The course of the second input stream shown in FIG. 2 is thus to be understood as being purely schematic; a more detailed example of the supply of the second input stream to the burner is shown below in FIG. 3.

[0102] Before being supplied to the burner the second input stream is preferably preheated, for example using a heat exchanger 50. Here too, the already partially cooled quench medium stream in conduit 32 or 42 for example may serve as heat transfer medium (not shown). It is particularly preferable to use the already relatively well cooled quench medium stream in conduit 42 as heat transfer medium for preheating the second input stream. In this way the second input stream as a carbon-containing input stream is preheated, but overheating, which can result in undesired side reactions on account of the reactivity of several ingredients, is avoided. Since the second input stream generally has a higher concentration of reactive ingredients having a propensity for undesired side reactions it is preferable to use a cooler heat transfer medium stream for the preheating of the second input stream than for the preheating of the first input stream. It is thus particularly preferable to arrange the heat exchanger 50 downstream of the heat exchanger 40 if the quench medium stream is to be used as heat transfer medium in both heat exchangers.

[0103] FIG. 3 shows schematically an example of the construction of a burner 11 according to an inventive embodiment of the invention. The inventive burner 11 depicted in side view in the upper portion of FIG. 3 is supplied with steam as moderator via conduit 11-10, with oxygen as oxidant via conduit 11-20, once more with steam as moderator via conduit 11-30 and with natural gas as a first input stream via conduit 11-40. The central conduit 11-51 is used to supply the burner with pyrolysis oil as a second input stream. The central conduit 11-51 is at its end configured as an atomizing apparatus and already before entry into the reaction chamber 10, i.e. still in the interior of the burner 11, opens into the annular channel 11-11 which coaxially and concentrically surrounds it and carries steam serving as atomizing medium for the second input stream, so that the pyrolysis oil is already atomized in the burner interior. The further annular channels 11-21 (oxygen), 11-31 (steam) and 11-41 (natural gas) are all likewise arranged coaxially and concentrically. This is depicted again in the lower portion of FIG. 3 as a plan view of a cross section through the burner. Natural gas, oxygen, steam as moderator and the mixture of moderator and atomized pyrolysis oil exit the burner via the corresponding conduits/annular channels and enter the reaction chamber as indicated schematically by flow arrows. Taking place in the reaction chamber is the partial oxidation reaction between the first and second input stream and the oxygen as oxidant with flame formation (shown as dotted line).

[0104] The inventive media path inside the burner ensures a uniform, low soot and low coke conversion of the first, fossil-derived input stream and the pyrolysis oil as the second input stream in the partial oxidation. The conversion of the first input stream benefits from the high oxygen content of the second input stream. The space-saving construction of a combined burner for the first and second input stream is also advantageous. Separate feed lances for the second input stream are not required and are thus saved.

[0105] Further constructive constituents of the burner, for example required cooling apparatuses and feeds for corresponding cooling media, are not shown in FIG. 3 due to the highly schematic representation. A person skilled in the art will supplement them with his knowledge of the art where required or advantageous.

[0106] FIG. 4 shows schematically a further example of an inventive embodiment of the invention as a plan view of a cross section of the apparatus. Three burners 11 are symmetrically arranged on a common burner faceplate 61. The construction of the burners corresponds to that of FIG. 3 with the annular channels 11-11, 11-21, 11,31 and 11-41 but without the central conduit 11-51. The central conduit 11-51 may alternatively also be retained but now used for feeding the first feed stream, for example natural gas; it would then be possible to dispense with one annular channel, for example the annular channel 11-41.

[0107] Arranged in the center of the circular faceplate 61 is a feed lance for pyrolysis oil as the second input stream. The feed conduit for the atomizing medium, for example steam, is not depicted. Said feed conduit preferably surrounds the central feed conduit for the pyrolysis oil as an annular channel. Both feed conduits open into a two-fluid atomizer nozzle (not shown) as an atomizing apparatus. It is advantageous that no alterations to the configuration of the burner are required compared to an operation of the partial oxidation reactor with only the first input stream. This moreover allows operating periods in which the partial oxidation reactor is supplied either with only the first input stream or with the first and the second input stream.

[0108] Arrangement of the feed lances and the burner on a common faceplate attached on the entry side of the reaction chamber has the advantage that feed lances and burners are thus particularly easy to unmount and subsequently remount for repairs and revisions.

NUMERICAL EXAMPLE

[0109] The following numerical example obtained by thermodynamic calculations shows the positive effect of the addition of pyrolysis oil as a second input stream in an existing plant for producing CO-rich synthesis gas by partial oxidation (POX) of natural gas as a first input stream.

[0110] In the comparative example a plant for noncatalytic partial oxidation (POX plant) having a thermal input power of 250 MW is considered as a base case without addition of pyrolysis oil. Preheated natural gas together with steam and recycle streams as input material is together with oxygen as oxidant converted into a raw synthesis gas. 29.2 t/h of CO and 3.8 t/h of H.sub.2 are formed in the raw synthesis gas at the outlet of the reactor. The reactor is supplied with altogether 13.9 t/h of fossil carbon in the form of natural gas having a methane content of 93% by volume as the first input stream and therefore altogether 90% by weight of the carbon is passed to the partial oxidation in the form of methane.

[0111] In the inventive numerical example the POX plant is likewise supplied with natural gas having a methane content of 90% by volume as the first input stream but the first input stream is reduced to such an extent that the same mass of carbon monoxide in the raw synthesis gas is producible upon addition of 5.3 t/h of pyrolysis oil having a heating value of 20 MJ/kg (as supplied, comprising 18% by weight water) and a carbon content of 54.6% by weight (anhydrous) as the second input stream. The first input stream may accordingly be reduced to 85% so that only 11.8 t/h of the carbon carrier of fossil origin need be employed to produce a particular CO mass flow. The thermal input power of the plant is thus reduced to 242 MW. The required oxygen amount at identical reactor temperature is simultaneously reduced by 6%. The mass of hydrogen produced is thus reduced slightly by 6% but remains 3.7 t/h. This results in an increase in the CO/H.sub.2 ratio in the synthesis gas by 6%.

[0112] If the proportion of renewable products of non-fossil origin is calculated as the difference between the inventive numerical example and 85% of the comparative example a regenerative and thus CO.sub.2-free proportion of altogether produced CO of 15% and H.sub.2 of 10% may be determined. In addition to the 6% reduction in oxygen demand in the gasification the same amount of CO is producible at a fossil carbon demand reduced by 2.4 t/h.

[0113] The invention is especially also suitable for retrofitting existing plants for low-CO.sub.2 synthesis gas production. In this case additional CO and H.sub.2 may be produced from biomass at minimal capital cost.

[0114] A further advantage is realized for plants whose main product is CO. In these plants the raw synthesis gas from the gasification stage is first freed of CO.sub.2 typically in a scrub and then in a cryogenic process (so-called coldbox) separated into the product CO and a residual gas. By increasing the CO/H.sub.2 ratio in the raw synthesis gas while maintaining a constant total amount of raw synthesis gas an existing plant retrofitted according to the invention makes it possible to produce more CO product and/or achieves lower consumption numbers for the overall process.

LIST OF REFERENCE SYMBOLS

[0115] 1 Plant

[0116] 2-5 Conduit

[0117] 10 Reaction chamber of partial oxidation reactor

[0118] 11 Burner

[0119] 11-10 Conduit

[0120] 11-20 Conduit

[0121] 11-30 Conduit

[0122] 11-40 Conduit

[0123] 11-11 Annular channel

[0124] 11-21 Annular channel

[0125] 11-31 Annular channel

[0126] 11-41 Annular channel

[0127] 11-51 Central conduit

[0128] 12-15 Conduit

[0129] 20 Cooling chamber of partial oxidation reactor

[0130] 13-15 Conduit

[0131] 21-22 Conduit

[0132] 23 Pump

[0133] 24 Conduit

[0134] 30 First heat exchanger

[0135] 32 Conduit

[0136] 40 Second heat exchanger

[0137] 42-49 Conduit

[0138] 50 Third heat exchanger

[0139] 51 Feed lance

[0140] 61 Faceplate