EP0683219B1 - Process for air blast gasification of carbonaceous fuels - Google Patents

Description

Technical field

The present invention relates to a method according to the preamble of claim 1. It also relates to a device to carry out the procedure.

State of the art

Oxygen-blown processes, for example Shell coal gasification processes, are currently mainly used for gasifying coal or residual oil. These processes produce a gas with a relatively high calorific value, 12-15 MJ / kg, which, due to its low mass flows, can be desulphurized without great loss of enthalpy and can be dedusted by washing equipment. The typical gasification reactions run CH4 + H2O → CO + 3H2 C + H2O → CO + H2 endothermic.
The energy required is, for example, by exothermic reaction 2C + O2 → 2CO made available.

About 22% of the calorific value of the fuel is first converted into heat by the exothermic reaction (3a) and then again into fuel enthalpy via the endothermic reactions (1) and (2).
In an air-blown gasification process according to the prior art, the exothermic reaction (3a) would become: 2C + O2 + 4N2 → 2CO + 4N2 and the calorific value of the product gases is reduced to less than 50% compared to oxygen-blown gasification. A major disadvantage of this process is the fact that the gasification product is contaminated with atmospheric nitrogen.

From EP 0 001 857 is known in a continuous Gasification process the exothermic reaction from the endothermic Separate reaction physically. The exothermic reaction can with Air can be carried out without the product containing atmospheric nitrogen contaminate. Nevertheless, the heat transfer between the Gas flows over a partition at the desired high Temperatures to new problems.

Presentation of the invention

The invention seeks to remedy this. The invention how it is characterized in the claims, the task lies based on a process and a gasification tank of the type mentioned above for the gasification of carbonaceous Fuels required energy by one to produce air-blown gasification process without that Gasification product is contaminated with atmospheric nitrogen. The procedure must also be carried out in such a way that the Heat transfer from the exothermic flow to the endothermic Flow at a high temperature level is not hindered.

The process is carried out with the help of a gasification tank carried out, in which a combustion Swirl flow is generated. It is in a swirl burner a substoichiometric fuel / air mixture on the axis burned, being essentially the exothermic reaction (3b) expires. Countercurrent is in the outer radius area also fuel with superheated steam at 700-1200 ° C gasified after the endothermic reactions (1) and (2). Due to the stable layering in the cylindrical reaction chamber it is avoided that the energy supplying partial flow in the Center where the combustion temperature is around 1800 ° C, with the fuel / steam mixture to be gasified in outer radius area mixes. The heat transfer from the energy supplier Partial flow to the mixture to be gasified happens through direct radiant heat exchange, through indirect Radiant heat exchange involving the combustion chamber wall and by convective heat transfer between the the combustion chamber wall heated by radiation and the gasification mixture. Following the gasification reactor is through Addition of secondary air to the central partial flow, which up to now already a large part of its sensible warmth towards it has emitted gasifying fuel / steam mixture completely burned out.

An advantage of the invention can be seen in the fact that two-stage combustion control is possible, including fuels use with fuel-bound nitrogen, without in the exhaust gas maintain high nitrogen oxide levels.

Another advantage of the invention is that the procedure applies to all fuels, in particular for liquid fuels, such as heavy oils, residual oils, orimulsion, or for coal in the form of coal water slurry (CWS) or in the form of coal dust.

• Es wird keine Luftzerlegungsanlage mehr benötigt;
• Das Verfahren kann sowohl atmosphärisch als auch unter Druck betrieben werden;
• Es entsteht ein Vergasungsprodukt mit einem moderaten Heizwert ≈ 10 MJ/kg, das in einer Gasturbine schadstoffarm verbrannt werden kann.

Further advantages of the invention are:

• An air separation plant is no longer required;
• The process can be operated both atmospherically and under pressure;
• The result is a gasification product with a moderate calorific value ≈ 10 MJ / kg, which can be burned in a gas turbine with low emissions.

Advantageous and expedient developments of the inventive Task solutions are characterized in the other claims.

In the following, an embodiment will be made with reference to the drawings the invention explained in more detail. All for the immediate Understanding the invention does not require elements are omitted. The direction of flow of the media is with Arrows indicated.

Brief description of the drawings

Fig. 1

einen zylindrischen Vergasungsbehälter, in welchem ein Vergasungsprodukt mit einem Heizwert ≈ 10 MJ/kg bereitgestellt wird,

Fig. 2

einen Vormischbrenner in der Ausführung als "Doppelkegelbrenner" in perspektivischer Darstellung, entsprechend aufgeschnitten und

Fig. 3-5

Schnitte durch verschiedene Ebenen des Vormischbrenners gemäss Fig. 2.

It shows:

Fig. 1

a cylindrical gasification container in which a gasification product with a calorific value ≈ 10 MJ / kg is provided,

Fig. 2

a premix burner in the version as a "double cone burner" in perspective, cut open accordingly and

Fig. 3-5

Sections through different levels of the premix burner according to FIG. 2.

Ways of carrying out the invention, commercial usability

• Radial geschichtete Drallströmung mit heissem Kern geringerer Dichte und kälterer Aussenströmung hoher Dichte.
• Gestufte Verbrennungsführung zur Minimierung der NOx-Emissionen.
• Strahlungswärmeaustausch zwischen unterstöchiometrischem heissem Kern und Reaktionsraumwand bzw. direkter Strahlungswärmeaustausch zwischen heissem Kern und VergasungsGemisch.

Dieses Verfahren, d.h. der bereitgestellte Brennstoff 15, eignet sich vorzüglich als Brennstoffaufbereitungssystem für Gasturbinen, Kombianlagen oder Heizkraftwerke mit Schweröl als Brennstoff, beispielsweise auch unter Zugabe von Klärschlamm. Auch zur Erzeugung eines Synthesegas in der chemischen Grundstoffindustrie ist das Verfahren geeignet. Gegenüber den sauerstoffgeblasenen Vergasungsprozessen hat es den weiteren Vorteil, dass wesentlich geringere Investionen und Betriebskosten anfallen.1 shows a cylindrical gasification container 1, which consists of a burner 100, a reaction chamber 2, a downstream flow chamber 3 in the direction of flow of the hot gases, and an intermediate pipe 4 connected in between. The burner 100 is preferably designed as a premix burner 2-5 referenced. The above-mentioned premix burner 100, which generates a stable hot gas flow 5 in the core or center 6 of the reaction chamber 2, acts on the head side and in the center of the reaction chamber 2. These hot gases 5 flow, so to speak, in a bundle and with a swirl through the reaction space 2. This flow through the center of the reaction space 2 is the actual energy supplier, the combustion temperature of which is approximately 1800 ° C. is. The intermediate pipe 4 has a number of openings 7 arranged in the circumferential direction of the flow cross-section, through which a secondary air 8 of the substoichiometric hot gases 5 flowing through there is admixed, the temperature of which is increased by the reaction that then takes place before these new hot gases 5a flow through the downstream flow chamber 3. This flow space 3 also fulfills the function of a heat exchanger: in the counterflow direction to the hot gases 5a, a steam flow 9 is introduced in a ring shape to the flow space 3, the initial temperature of which is approximately 150 ° C. This steam 9 is superheated along the heat exchange path before it flows through the intermediate pipe 4. In return, the hot gases 5a cool down to exhaust gases 14 with a temperature of 500 ° C., for which they are ideally suited for generating steam for operating a steam turbine. Adjacent to the upstream reaction chamber 2, the annular opening of the intermediate tube 4 has a series of swirl bodies 10 arranged in the circumferential direction with fuel injection, which produce a mixture of fuel and superheated steam, hereinafter referred to as gasification mixture 11, which is forced to rotate. This rotating movement encases the central flow of the hot gases 5 in the counterflow direction in such a way that heat is transported between the two media without mutual exchange and without physical separation, as is the case with heat exchangers. This gasification mixture 11 leaves the reaction chamber 2 as fuel 15 with a calorific value <10 MJ / kg and at a temperature of approx. 650 ° C., the still existing rotating movement being canceled by further swirl bodies 12 placed at the end of the reaction chamber 2 before this fuel 15 is supplied to its area of application. The heat transfer from energy-supplying hot gases 5 to the gasification mixture 11 can take place not only by direct radiant heat exchange, but also optionally by indirect radiant heat exchange involving the wall of the reaction chamber 2, or by convective heat transfer between the reaction chamber wall mentioned by radiation and the gasification mixture 11. This gives one Part of its heat in the heat exchange process of a primary air 13, the flow of which runs in a ring shape to the gasification mixture 11. This heated primary air 12 with a temperature> 500 ° C then forms the combustion air for the premix burner 100. Accordingly, the following basic principles are used:

• Radially stratified swirl flow with a hot core of lower density and a colder outer flow of high density.
• Staged combustion control to minimize NOx emissions.
• Radiant heat exchange between the substoichiometric hot core and reaction chamber wall or direct radiant heat exchange between the hot core and the gasification mixture.

This method, ie the fuel 15 provided, is particularly suitable as a fuel processing system for gas turbines, combination plants or combined heat and power plants with heavy oil as fuel, for example also with the addition of sewage sludge. The process is also suitable for generating a synthesis gas in the basic chemical industry. Compared to the oxygen-blown gasification processes, it has the further advantage that significantly lower investments and operating costs are incurred.

To better understand the structure of burner 100, it is of advantage if the individual at the same time as FIG. 2 Cuts according to Figures 3-5 can be used. Furthermore, in order not to make Fig. 2 unnecessarily confusing, are those shown schematically in FIGS. 3-5 Baffles 121a, 121b have only been hinted at. The following is the description of FIG. 2 as needed referred to the remaining figures 3-5.

The burner 100 according to FIG. 2 is a premix burner and is made up of of two hollow conical part-bodies 101, 102 which are nested staggered. The dislocation the respective central axis or longitudinal symmetry axes 101b, 102b of the tapered partial bodies 101, 102 to one another creates on both sides, in a mirror image arrangement, each have a tangential air inlet slot 119, 120 free (Fig. 3-5), through which the combustion air 115 in the interior burner 100, i.e. flows into the cone cavity 114. The conical shape of the partial bodies 101, 102 shown in the flow direction has a certain fixed angle. Of course, depending on the operational use, the partial body 101, 102 an increasing or decreasing in the direction of flow Show cone inclination, similar to a trumpet. Tulip. The last two forms are not included in the drawing, since they can be easily understood by the expert are. The two conical partial bodies 101, 102 each have a cylindrical starting part 101a, 102a, which also, analogous to the conical partial bodies 101, 102, offset from one another run so that the tangential air inlet slots 119, 120 available over the entire length of the burner 100 are. There is a nozzle in the area of the cylindrical starting part 103 housed, the injection 104 approximately with the narrowest Cross section of the through the tapered body 101, 102nd formed cone cavity 114 coincides. The injection capacity and the type of this nozzle 103 depends on the given parameters of the respective burner 100. Of course the burner can be purely conical, i.e. without a cylindrical one Initial parts 101a, 102a. The conical Sub-bodies 101, 102 also each have a fuel line 108, 109 on which along the tangential Entry slots 119, 120 arranged and with injection openings 117 are provided, through which preferably a gaseous Fuel 113 in the combustion air flowing through there 115 is injected, as shown by the arrows 116 want. These fuel lines 108, 109 are preferably at the latest at the end of the tangential inflow, before entering the cone cavity 114, placed, this to get an optimal air / fuel mixture. The exit opening of the burner 100 is on the combustion chamber side 122 into a front wall 110 in which a number of holes 110a are present. The latter occur when necessary Function, and ensure that dilution air or cooling air 110b fed to the front part of the combustion chamber 122 becomes. In addition, this air supply ensures flame stabilization at the output of burner 100. This flame stabilization becomes important when it comes to the Compactness of the flame due to radial flattening support. With the fuel supplied through the nozzle 103 it is a liquid fuel 112, at most can be enriched with a recirculated exhaust gas. This fuel 112 is at an acute angle in the Cone cavity 114 injected. The nozzle 103 thus forms a tapered fuel profile 105 that is tangential from the incoming rotating combustion air 115 enclosed becomes. In the axial direction, the concentration of the Fuel 112 continuously through the incoming combustion air 115 degraded to optimal mixing. Becomes the burner 100 is operated with a gaseous fuel 113, this is preferably done via opening nozzles 117 introduced, the formation of this fuel / air mixture directly at the end of the air inlet slots 119, 120 is coming. When fuel 112 is injected via the Nozzle 103 is in the area of the vortex burst, that is in the area the backflow zone 106 at the end of the burner 100, the optimal homogeneous fuel concentration across the cross-section reached. The ignition takes place at the top of the backflow zone 106. Only at this point can a stable flame front 107 arise. A flashback of the flame inside the burner 100, as is latently the case with known premixing sections is a remedy there with complicated flame holders is not to be feared here. Is the combustion air 115 additionally preheated or with a recirculated Exhaust gas enriched, this supports the evaporation of liquid fuel 112 sustainable before the Combustion zone is reached. The same considerations also apply if via lines 108, 109 instead of gaseous liquid fuels are supplied. When designing the tapered partial body 101, 102 with respect to the taper angle and width of the tangential air inlet slots 119, 120 narrow limits must be observed so that the desired Flow field of the combustion air 115 with the flow zone 106 can set at the output of the burner. General is too say a reduction in tangential air inlet slots 119, 120 the backflow zone 106 further upstream moves, but then the mixture earlier comes to ignition. After all, it should be noted that the Once the backflow zone 106 is fixed, it is positionally stable is because the swirl number increases in the direction of flow in the area the cone shape of the burner 100. The axial speed can be within the burner 100 by a corresponding Supply of an axial combustion air flow, not shown change. The construction of the burner 100 is also excellent, the size of the tangential To change air inlet slots 119, 120, with what a relative without changing the overall length of the burner 100 large operational bandwidth can be captured.

3-5 now shows the geometric configuration of the Baffles 121a, 121b. They have a flow initiation function these, according to their length, the respective End of the tapered partial body 101, 102 in the direction of flow extend towards the combustion air 115. The Channeling the combustion air 115 into the cone cavity 114 can by opening or closing the guide plates 121a, 121b by one in the area of the entry of this channel into the Cone cavity 114 placed pivot point 123 can be optimized, this is particularly necessary if the original gap size the tangential air inlet slots 119, 120 changed becomes. Of course, these can be dynamic arrangements can also be provided statically, as required Baffles are an integral part with the tapered partial bodies 101, 102 form. The burner 100 can also can be operated without baffles, or others can Aids for this are provided.

Reference list

1

Gasification tank

2nd

Reaction space

3rd

Flow space

4th

Intermediate tube

5

Hot gases, hot gas stratification

5a

New hot gases

6

Center, core

7

Openings

8th

Secondary air

9

steam

10th

Swirl body

11

Gasification mixture

12th

Swirl body

13

Primary air

14

Exhaust

15

fuel

100

Premix burner

101, 102

Partial body

101a, 102a

Cylindrical starting parts

101b, 102b

Longitudinal symmetry axes

103

Fuel nozzle

104

Fuel injection

105

Fuel injection profile

106

Reverse flow zone (vortex breakdown)

107

Flame front

108, 109

Fuel lines

110

Front wall

110a

Air holes

110b

Cooling air

112

Liquid fuel

113

Gaseous fuel

114

Cone cavity

115

Combustion air

116

Fuel injection

117

Fuel nozzles

119, 120

Tangential air inlet slots

121a, 121b

Baffles

122

Combustion chamber

123

Pivot point of the guide plates

Claims (8)

1. Process for air-blown gasification of carbon-containing fuels, the required energy for the gasification being provided by heat exchange between an endothermic and an exothermic reaction, a hot gas being produced by the exothermic reaction of combustion of a substoichiometric fuel/air mixture, and a gasification mixture being produced by the endothermic reaction of a gasification process between a fuel and superheated steam, characterized in that the fuel/air mixture flows with central rotation into a reaction space, with the result that a central rotated hot gas stream is generated in the longitudinal direction of the reaction space, in that the gasification mixture is introduced with annular rotation into the reaction space, in the longitudinal direction opposite to the hot gas flow, with the result that the gasification mixture, in the form of the rotational annular flow flowing countercurrently in the longitudinal direction, surrounds the rotational central hot gas flow in a common reaction space, and in that the heat exchange is effected by heat radiation between the hot gas and the gasification mixture.
2. Process according to Claim 1, characterized in that secondary air is admixed to the hot gas after the heat exchange process, in that this new hot gas prepares the superheated steam in the heat exchange process and flows away as exhaust gas, and in that the gasification mixture heats primary air in the heat exchange process and subsequently flows away as fuel.
3. Device for carrying out a process for air-blown gasification of carbon-containing fuels, the device essentially consisting of a gasification vessel, characterized in that the gasification vessel (1) consists of a reaction space (2), an intermediate piece (4) downstream in the direction of flow of the hot gases (5) and a flow space (3), in that a burner (100) which generates a central rotational hot gas flow (5) in the longitudinal direction of the reaction space (2) is arranged at the top of the reaction space (2), in that the intermediate piece (4) has a number of rotation structures (10) which are arranged in the circumferential direction and rotate the gasification mixture (11) flowing through, and in that the hot gases (5) are surrounded by this gasification mixture (11) in a direction opposite to the direction of flow.
4. Device according to Claim 3, characterized in that the burner (100) consists of at least two hollow, conical subcomponents (101, 102) which are fitted in one another in the flow direction and the longitudinal symmetry axes (101b, 102b) of which are mutually offset, in that the adjacent walls of the subcomponents (101, 102) form tangential channels (119, 120) for a combustion air flow (115) in the longitudinal extent of the subcomponents, and in that at least one fuel nozzle (103) is present in the hollow conical space (114) formed by the subcomponents (101, 102).
5. Device according to Claim 4, characterized in that further fuel nozzles (117) are arranged in the region of the tangential channels (119, 120), in the longitudinal extent of the latter.
6. Device according to Claim 4, characterized in that the subcomponents (101, 102) extend conically at a fixed angle in the flow direction.
7. Device according to Claim 4, characterized in that the subcomponents (101, 102) have an increasing conicity in the flow direction.
8. Device according to Claim 4, characterized in that the subcomponents (101, 102) have a decreasing conicity in the flow direction.

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