PROCESS BURNER AND PROCESS FOR COMBUSTION OF CARBON MONOXIDE-CONTAINING FUEL GASES

Abstract

The invention relates to a process burner for combustion of a plurality of fuel gases with a gaseous auxiliary medium, wherein one of the fuel gases comprises carbon monoxide (CO). The process burner according to the invention includes a first fuel gas unit, a second fuel gas unit and an auxiliary media unit. A first fuel gas which may be natural gas for example is introduced into the process burner via a first fuel gas nozzle in the region of the combustion zone. Carbon monoxide-containing fuel gas is introduced into the process burner via the second fuel gas unit, wherein a second fuel gas nozzle for introducing the carbon monoxide-containing fuel gas is arranged in the region of the auxiliary media unit.

Claims

1. A process burner for combustion of a plurality of fuel gases with a gaseous auxiliary medium, wherein one of the fuel gases comprises carbon monoxide (CO), comprising: a. a first fuel gas unit configured to introduce a first fuel gas, comprising a first fuel gas conduit and a first fuel gas nozzle, wherein the first fuel gas conduit comprises a first fuel gas inlet and a first fuel gas outlet, wherein the first fuel gas inlet is in fluid connection with a first fuel gas source and the first fuel gas outlet is connected to the first fuel gas nozzle; b. a second fuel gas unit for introducing a second fuel gas, comprising a second fuel gas conduit and a second fuel gas nozzle, wherein the second fuel gas conduit comprises a second fuel gas inlet and a second fuel gas outlet, wherein the second fuel gas inlet is in fluid connection with a second fuel gas source, wherein the fuel gas from the second fuel gas source comprises at least carbon monoxide and the second fuel gas outlet is connected to the second fuel gas nozzle; c. an auxiliary media unit comprising an auxiliary media conduit and a burner plenum, wherein the auxiliary media conduit comprises an auxiliary media inlet and an auxiliary media outlet, wherein the auxiliary media inlet is in fluid connection with an auxiliary media source and the auxiliary media outlet is connected to the burner plenum; d. a burner tile, wherein the burner tile adjoins the burner plenum and the burner tile has a refractory surface, wherein the refractory surface adjoins a combustion zone of the process burner, wherein the burner tile and the combustion zone are configured for combustion of the first fuel gas and the second fuel gas with the auxiliary medium, wherein, the first fuel gas nozzle for introducing the first fuel gas is arranged inside the combustion zone and the second fuel gas nozzle for introducing the second fuel gas is arranged inside the auxiliary media unit.

2. The process burner according to claim 1, wherein the second burner gas nozzle for introducing the second burner gas is arranged inside the burner plenum.

3. The process burner according to claim 1, wherein the second fuel gas conduit at least partially extends through the burner plenum.

4. A steam reformer or a steam cracker, comprising a process burner according to claim 1.

5. A process for combustion of a plurality of fuel gases with a gaseous auxiliary medium in a process burner, wherein the process burner comprises a first fuel gas unit, a second fuel gas unit and an auxiliary media unit and wherein one of the fuel gases comprises carbon monoxide, comprising the following process steps: a. introducing a first fuel gas from a first fuel gas source into the first fuel gas unit, wherein the first fuel gas unit comprises a first fuel gas conduit and a first fuel gas nozzle; b. introducing a second fuel gas from a second fuel gas source into the second fuel gas unit, wherein the fuel gas from the second fuel gas source comprises at least carbon monoxide and wherein the second fuel gas unit comprises a second fuel gas conduit and a second fuel gas nozzle; c. introducing an auxiliary medium from an auxiliary media source into the auxiliary media unit, wherein the auxiliary media unit comprises an auxiliary media conduit and a burner plenum; d. introducing the first fuel gas via the first fuel gas nozzle into a combustion zone of the process burner, wherein the combustion zone adjoins a refractory surface of a burner tile and the burner tile adjoins the burner plenum; e. introducing the second fuel gas into the auxiliary media unit via the second fuel gas nozzle; f. combusting the first fuel gas and the second fuel gas with the auxiliary medium in the combustion zone of the process burner.

6. The process according to claim 5, wherein the second fuel gas is introduced into the burner plenum of the auxiliary media unit.

7. The process according to claim 5, wherein the fuel gas from the second fuel gas source comprises at least 50 mol % of carbon monoxide.

8. The process according to claim 5, wherein the auxiliary media source comprises air, oxygen or oxygen-enriched air.

9. The process according to claim 5, wherein the second fuel gas is introduced via the second fuel gas nozzle at a temperature of less than 160° C.

10. The process according to claim 5, wherein the ratio of the volume flow of the auxiliary medium relative to the volume flow of the second fuel gas, is 15:1 to 10:1.

11. The process according to claim 5, wherein the second fuel gas is introduced into the second fuel gas unit at a temperature of 20° C. to 50° C.

12. The process according to claim 5, wherein the auxiliary medium is introduced into the auxiliary media unit at a temperature of 250° C. to 350° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The invention is hereinbelow more particularly elucidated by an exemplary embodiment and numerical examples. In the following detailed description reference is made to the accompanying FIGURE which forms a part of the exemplary embodiment and which contains an illustrative representation of a specific embodiment of the invention. In this connection, direction-specific terminology such as “top”, “bottom”, “front”, “back”, etc., is used with reference to the orientation of the described FIGURE. Since components of embodiments may be positioned in a multiplicity of orientations, the direction-specific terminology is used for elucidation and is in no way limiting. A person skilled in the art will appreciate that other embodiments may be used and structural or logical changes may be undertaken without departing from the scope of protection of the invention. The following detailed description is therefore not to be understood in a limiting sense, and the scope of protection of the embodiments is defined by the accompanying claims. Unless otherwise stated the drawing is not to scale,

[0050] FIG. 1 shows an inventive process burner 100 having a first fuel gas unit, a second fuel gas unit and an auxiliary media unit.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0051] Process burner 100 according to FIG. 1 is configured for operation in a steam reformer and is operated with natural gas as the first fuel gas and pure carbon monoxide (purity >99% by weight) as the second fuel gas. Ambient air is used as the auxiliary medium.

[0052] The process burner 100 is secured via a steel construction 101 located outside the combustion space of the steam reformer. The flame of the process burner 100 radiates downwards into the radiation space of the steam reformer which is externally delimited by a refractory wall 102. Arranged in the radiation space of the steam reformer are a plurality of nickel catalyst-filled reaction tubes which are heated by a multiplicity of the depicted process burners 100. Inside the reaction tubes natural gas is reacted with steam to afford synthesis gas in an endothermic reaction.

[0053] The process burner 100 comprises a first fuel gas unit which comprises at least one first fuel gas conduit 110, a first fuel gas nozzle 111, a flow controller 114, a flange 115 and a lance 116. The first fuel gas conduit 110 comprises a first fuel gas inlet 112 and a first fuel gas outlet 113. The first fuel gas inlet 112 is in fluid connection with a first fuel gas source (not shown). The first fuel gas source is natural gas. The amount of flow of the first fuel gas (natural gas), i.e. the volume flow of the first fuel gas, is varied via the flow controller 114. A portion of the first fuel gas conduit 110 is the burner lance 116 which is connected via a flange 115 to the upper section of the fuel gas conduit 110. The burner lance 116 which thus forms a portion of the first fuel gas conduit 110 partially extends through a burner plenum 131 and opens into the first fuel gas nozzle 111 through which the first fuel gas is introduced into the process burner 100, more particularly into a combustion space 141 of the process burner 100.

[0054] The process burner 100 further comprises a second fuel gas unit which comprises at least one second fuel gas conduit 120 and a second fuel gas nozzle 121. The second fuel gas conduit 120 may likewise comprise a flow controller for the second fuel gas (not shown). The second fuel gas conduit 120 comprises a second fuel gas inlet 122 and a second fuel gas outlet 123. The second fuel gas inlet 122 is in fluid connection with a second fuel gas source (not shown). The second fuel gas source is pure carbon monoxide (purity at least 99% by weight). The second fuel gas nozzle 121 is connected to the second fuel gas conduit via the second fuel gas outlet 123. The second fuel gas nozzle is arranged inside an auxiliary media unit, more particularly inside an auxiliary media conduit 130. The portion of the second fuel gas conduit 120 opening into the second fuel gas nozzle 121 may likewise be configured as a burner lance.

[0055] The process burner 100 further comprises an auxiliary media unit which comprises at least one auxiliary media conduit 130, a sound absorber 134 and a burner plenum 131 (windbox). The auxiliary media conduit 130 comprises an auxiliary media inlet 132 and an auxiliary media outlet 133, The auxiliary media inlet 132 is in fluid connection with an auxiliary media source (not shown). The auxiliary medium from the auxiliary media source is ambient air. The auxiliary media outlet 133 is connected to the burner plenum 131 or is at least in fluid connection with the burner plenum 131, The burner plenum 131 conducts and distributes the auxiliary medium (air) in the direction of the burner tip or the burner neck (lower portion of the process burner), A portion of the auxiliary media conduit 130 is the sound absorber 134 which here comprises the auxiliary media outlet 133 and opens into the burner plenum 131. The sound absorber 134 absorbs the sound from the adjoining reformer furnace.

[0056] Adjoining the burner plenum 131 is the burner tile 140 which is here configured as a hollow-cylindrical burner tile 140 and has a refractory surface (not shown) at least on its inside. In other embodiments the burner plenum 131 may be merely in fluid connection with the burner tile 140, without there being a direct connection between the burner plenum 131 and the burner tile 140. Adjacent to the refractory surface of the burner tile 140 is the combustion space 141 of the process burner 100 in which the actual combustion of the first and second fuel gas with the auxiliary medium (air) is carried out. A portion of the first fuel gas conduit 110, here the burner lance 116, and the first fuel gas nozzle 111 extend into the combustion space. Produced in the combustion space 141 is a flame which radiates downwards into the radiation space of the steam reformer.

[0057] The inventive process burner 100 may comprise a plurality of first and/or second fuel gas units. In one example a first fuel gas unit may be arranged centrally and surrounded by a plurality of further first fuel gas units. The inventive process burner 100 may thus be configured as a fuel staged or air staged process burner. In these configurations known to those skilled in the art the combustion reaction is retarded, thus reducing undesired NOx emissions. The inventive process burner moreover comprises a pilot or start-up burner in the region of the burner tile 140 to initiate the combustion reaction inside the combustion zone 141.

[0058] In alternative embodiments the second fuel gas nozzle 121 may also be arranged inside the sound absorber 134 or the burner plenum 131 which both form a portion of the auxiliary media unit. In the combustion zone 141 temperatures of about 1500° C. to 2000° C. may prevail. By contrast, the temperatures inside the auxiliary media unit are several times lower. In particular the inventive process burner 100 may be configured such that the temperatures at the outlet of the second fuel gas nozzle 121 are below 200° C. or even below 100° C. This effectively prevents the undesired Boudouard reaction of two mol of carbon monoxide to afford one mole of solid carbon (graphite) and carbon dioxide from occurring at the outlet of the second fuel gas nozzle 121 since the activation energy for this reaction is not achieved. The second fuel gas unit is thus not affected by blockages through carbon deposits. While the temperature of the second fuel gas does subsequently continue to increase in the direction of the burner plenum 131 and the second fuel gas does ultimately also “see” high temperatures in the combustion zone 141 dilution with the first fuel gas takes place here and it is also virtually impossible for carbon formed in the combustion zone 141 to be deposited on the inside of the first fuel gas nozzle 111. This is because there prevails in the first fuel gas nozzle 111 a certain pressure drop in the direction of the combustion space which ensures that carbon particles do not pass into the interior of the second fuel gas nozzle 121 but rather are conducted away in the direction of the radiation space of the reformer furnace with the flue gas.

[0059] The following table reports four inventive Examples 1 to 4 whose data were determined by computer simulations using the software Aspen+.

TABLE-US-00001 Example Example Example Example 1 2 3 4 CO flow rate Nm.sup.3/h 151 30 151 30 Interior diameter mm 20.9 20.9 15.8 15.8 (CO outlet second fuel gas T (air)conduit) ° C. 310 310 310 310 T (CO) ° C. 35 35 35 35 T (second fuel ° C. 99 178 86 159 gas conduit outlet, outside) T (second fuel ° C. 99 176 84 157 gas conduit outlet, inside)

[0060] Pure carbon monoxide was used as the second fuel gas and this was introduced into the process burner via the second fuel gas nozzle in the region of the auxiliary media unit at a temperature of 35° C. and a pressure of 3 bang. The auxiliary medium, in this case preheated air, passes through the auxiliary media conduit at a temperature of 310° C. The flow rate of the carbon monoxide introduced into the process burner via the second fuel gas conduit in the region of the auxiliary media unit, and the diameter at the outlet for carbon monoxide at the second fuel gas conduit (second fuel gas outlet) which opens into the second fuel gas nozzle, were varied.

[0061] Arranging the second fuel gas nozzle in the region of the auxiliary media unit has the result that temperatures of markedly below 200° C., advantageously below 100° C., are to be expected in the region of the second fuel gas nozzle when the flow rate of carbon monoxide is appropriately high (Examples 1 and 3). The low temperatures at the outlet of the second fuel gas conduit effectively inhibit formation of carbon from carbon monoxide in this region, especially at high CO flow rates. At the high flow rates of the Examples 1 and 3 it can be assumed that the formation of solid carbon from CO is particularly effectively inhibited since at temperatures of below 135° C. it can be assumed that the activation energy of the Boudouard reaction of two mol of carbon monoxide to afford one mole of solid carbon (graphite) and carbon dioxide (uncatalyzed case) is not achieved at least in the region of the outlet of the second fuel gas conduit.

[0062] The following table shows two further inventive Examples 5 and 6. The temperature for the auxiliary medium (air) was somewhat lower here and the volume flow of the auxiliary medium was adjusted so as to result in a ratio of volume flows of auxiliary medium to carbon monoxide (second fuel gas) of about 13:1. In both examples a temperature of markedly below 135° C. was in turn determined in the region of the outlet of the second fuel gas conduit and it can therefore be assumed that the activation energy for the carbon formation reaction is not achieved at least in the region of the outlet of the second fuel gas conduit.

TABLE-US-00002 Example 5 Example 6 CO flow rate Nm.sup.3/h 54.8 42.8 Air flow rate Nm.sup.3/h 706.4 551.0 Interior mm 20.9 20.9 diameter (CO outlet) T (air) ° C. 270 270 T (CO) ° C. 35 35 T (fuel gas ° C. 117 121 conduit outlet, outside) T (fuel gas ° C. 115 119 conduit outlet, inside)

LIST OF REFERENCE NUMERALS

[0063] 100 Process burner [0064] 101 Steel construction [0065] 102 Reformer furnace wall [0066] 110 First fuel gas conduit [0067] 111 First fuel gas nozzle [0068] 112 First fuel gas inlet [0069] 113 First fuel gas outlet [0070] 114 Row controller [0071] 115 Range [0072] 116 Burner lance [0073] 120 Second fuel gas conduit [0074] 121 Second fuel gas nozzle [0075] 122 Second fuel gas inlet [0076] 123 Second fuel gas outlet [0077] 130 Auxiliary media conduit [0078] 131 Burner plenum [0079] 132 Auxiliary media inlet [0080] 133 Auxiliary media outlet [0081] 134 Sound absorber [0082] 140 Burner the [0083] 141 Combustion zone

[0084] It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described 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.