SOLID FIRED HOT GAS GENERATOR WITH EXTENDED REGULATING RANGE

Abstract

The invention relates to a solid fired hot gas generator which comprises a plurality of solid burners for extending the regulating range, which form a multiple solid burner with an enlarged regulating range. A solid feed and a combustion air feed are assigned to each solid burner and with the aid of a dosing means a separate, dosed solid feed to each solid burner is guaranteed. The firing power of the multiple solid burner which is in particular a multiple impulse burner extends from the minimum power of one of the solid burners to the maximum power of all solid burners so that a regulation of all necessary load regions of a plant unit to be supplied is covered.

Description

The invention relates to a solid fired hot gas generator with an extended regulating range which can preferably be used in grinding-drying installations, for example for grinding solid fuels.

Coal grinding plants with an air swept mill, for example a vertical roller mill of the LOESCHE type, a suspended roller mill or a ring roller mill, in which wet raw coal is subjected to a grinding-drying process with the supply of hot gas and ground to coal dust, with a separating unit, for example a filter, in which the coal dust-gas mixture is separated, and with a hot gas generator for generating the hot gas, to which a part of the gas is fed back as return gas, are known from coal gasification, pig iron and steel production with PCI (Pulverised Coal Injection) processes and from the cement industry (DE 40 35 730 C2, catalogue of LOESCHE GmbH, Düsseldorf, “Loesche-Mühlen für feste Brennstoffe”, 01/2008).

Coal dust fired hot gas generators are additionally used in the non-metallic minerals industry to dry raw meal, slag and granulated blast furnace slag and cement. Hot gas generators which are fired with brown coal or hard coal dust are also known in the gypsum, sugar and potash industry.

A hot gas generator with a burner which is fired with pneumatically conveyed combustion dust, for example hard coal or brown coal dust, biomass dust or mixtures thereof, with the supply of combustion air, a burner muffle arranged on the outlet side on the burner, a feed for the gas to be heated and a mixing component which is arranged after the burner muffle and formed as a perforated jacket (LOMA) with staggered cylinder portions and with a protective jacket forms an annular channel for the gas to be heated is known from DE 197 06 077 A1.

The hot gas generator described in DE 42 08 951 A1 already comprises a perforated jacket unit made of metal for flowing in of the gas to be heated and a burner muffle which is formed to be substantially shorter in axial direction than the perforated jacket unit and is lined with a fire-resistant material. The burner is here, however, a multi-lance burner with lean gas-combustion air nozzles surrounding each other.

DE 197 25 613 A1 discloses a burner for generating hot waste gases by combusting heating oil or heating gas or coal dust. The coal dust is transported with a gaseous carrier medium, preferably air, and is injected through an injection lance, which extends from the burner head to the point of the largest diameter of a conical reaction chamber and is provided at the outlet side end with a deflection hood, into the reaction chamber. The combustion air is fed via a radial blade cascade at the head-side end of the reaction chamber. The blade cascade and a part of the reaction chamber are surrounded by an air collecting housing, in which the combustion air is to be settled and from which the combustion air passes via the blade cascade into the reaction chamber. The burner generates, as a consequence of its flow pattern, a particularly large area of turbulent fluctuation movements. The combustion dust is transported back to the air guide blades after leaving the deflection hood and is heated by a swirling, screw-like flame to approximately 1000° C. and ignited. The flame jet has a strong impulse and produces a very rapid recirculation of the gases.

In the internet publication “Impuls-Brenner, System Dr. Schoppe, für Braunkohlenstaub, Heizöl und Gas von 100 kW bis 35 MW” the aforementioned burner is described as an impulse burner.

A further development of the impulse burner which is to comprise an increased flame stability and flame jet speed for a hot gas temperature range of at least 200° C. to 900° C. is described in DE 102 32 373 B4.

Burners for solid fuels which are used in association with mixing chambers have a regulating range of maximum 1:5. This technically substantiated limitation of the regulating range makes more difficult or prevents the use of hot gas generators with mixing chambers, for example a perforated jacket unit, in process-based installations which require higher regulating ranges, for example regulating ranges up to 1:10. Such regulating ranges can be caused by greatly fluctuating moistures of the material to be dried and changes in the throughput of the aggregate to be delivered.

The throughput of a vertical roller mill of the LOESCHE type lies for example between 100% and 40%. The mill thus has a regulating ratio of 1:2.5. If a minimum throughput coincides with a very low moisture and a relatively high outside temperature only a relatively low heat is necessary. A maximum heat consumption results with a maximum throughput, a maximum moisture of the material to be ground and dried and a relatively low outside temperature.

The following concrete example is to illustrate that a regulating ratio of approximately 1:8 is necessary in order to be able to approach all “operating points”.

EXAMPLE

Hard Coal

Max. case Throughput=80 t/h

Moisture=15%

Temperature=5° C.

Heat quantity=49.66×10⁶ kJ/h (13.8 MW)

Min. case Throughput=32 t/h

Moisture=5%

Temperature=35° C.

Heat quantity=6.1×10⁶ kJ/h (1.695 MW)

The regulating ratio thus amounts to: 49.66:6.1=1:8.14.

The aforementioned regulating ratio of 1:8.14 has been achieved thus far without a hot gas generator with a solid burner. In grinding-drying installations for grinding coal, therefore, insofar as waste heat is not available from the process itself, predominantly hot gas generators with a gas or oil burner are used. In case of coal gasification installations as a rule synthesis gas is fed to the hot gas generator as fuel and in PCI plants blast furnace gas for combustion. The coal grinding installations for coal gasification, PCI plants and in the cement industry require regulating ranges of at least 1:8. Generally a regulating ratio of at least 1:10 for oil and gas fired hot gas generators is already state of the art.

It is an object of the invention to create a solid fired hot gas generator, in particular a coal dust fired hot gas generator, with an extended regulating range in order to be able to replace heating oil and gas by a cost-effective fuel, for example brown coal dust, hard coal dust etc. and also to be able to set aside the economically inefficient use of synthesis gas, blast furnace gas etc. for producing hot gases in hot gas generators.

According to the invention the object is achieved through the features of claim 1 and claim 2. Useful and advantageous embodiments are contained in the sub-claims and the description of the figures.

A core thought can be seen in equipping a hot gas generator with a plurality of burners in order to increase the regulating range.

According to the invention a solid fired hot gas generator comprises a plurality of solid burners in order to increase or extend the regulating range so that a multiple solid burner is formed.

An independent solid feed and a combustion air feed are assigned to each solid burner and each solid burner can be fired independently of the other solid fuels burners. The firing power of the multiple solid burner then extends from the minimum power of one of the solid burners to the maximum power of all solid burners provided. The regulating range is thus extended and all load regions of an aggregate, to which the hot gas produced in the hot gas generator is supplied, can be covered.

In a preferred embodiment a hot gas generator with a burner muffle and a start burner, which is arranged in a burner plate of the burner muffle, with a feed means for the gas to be heated and with a mixing component, in which the combustion gas produced is mixed with the gas to be heated, and which is arranged after the burner muffle, comprises a plurality of solid burners which are arranged coaxially with the start burner and fixed in the burner plate of the burner muffle.

The number of burners can advantageously be adapted to the respective requirements. For example two, three or four, possibly also more solid burners can be flanged to the burner plate of the burner muffle. Burners of equal or different size can also be advantageously used, that is to say burners with equally large or different sized firing power.

The inventive hot gas generator is usefully designed in vertical construction and the multiple solid burner is designed and arranged in the burner plate of the burner muffle so that the solid burner with its coal dust supply and its reaction chamber extend into the burner muffle.

It is advantageous if three solid burners are arranged with equal distance from each other and arranged coaxially with the start burner guided on a longitudinal shaft of the burner muffle and through the burner plate. The burners can also be arranged at a defined angle in such a way that the flue gases leaving the burners are guided to the centre of the outlet of the burner muffle. As the solid burners are provided for ash-containing fuels a vertically or downwardly inclined arrangement is recommended in the burner plate or in the burner muffle of the hot gas generator.

It is further advantageous that a burner muffle which must be adapted merely in its dimensioning to the provided number of solid burners in the burner plate can be used. The burner muffle can be lined with a fire-resistant material.

It is also useful if the burner muffle is surrounded with a feed means for the gas to be heated and the gas to be heated can be fed to the subsequent mixing component for mixing with the combustion gas produced.

A perforated jacket unit can advantageously be arranged as a mixing component which is formed as a steel combustion chamber and comprises in axial direction a plurality of cylindrical and coaxial perforated jackets which form at their transitions annular gaps for flowing in of gas to be heated and are surrounded by an outer, closed sheet steel jacket with the formation of an annular channel. Such a sheet steel chamber is known as a perforated jacket combustion chamber (LOMA-combustion chamber).

Impulse burners of Carbotechnik Energiesysteme GmbH, Geretsried can be advantageously used for example as solid burners. These have been described above in connection with DE 197 25 613 A1 and DE 102 32 373 B4 and an internet publication of this company. However, other solid burners can also be used.

The impulse burners have powers between 0.5 and 100 MW and are suited to arrangement in an upper, end face burner plate of the burner muffle of the inventive hot gas generator so that a multiple impulse burner is formed.

For separate control and regulation of each individual solid burner a dosing means is provided which can supply each solid burner with coal dust individually and independently of the operation of the adjacent burner and can move to each desired regulating point.

The CT dosing machine for fluidising, dosing and pneumatic conveying of Carbotechnik Energiesysteme GmbH, Geretsried is particularly suitable.

The dosing machine is described in an internet publication of the aforementioned company and in EP 0 054 018 B1 and EP 0 210 162 B2.

The extended or increased regulating range of the inventive hot gas generator with a multiple solid burner or a multiple impulse burner is to be explained further below with the aid of the example described at the start.

In this example a maximum heat quantity of 13.8 MW was necessary. For process-based reasons and having regard to the incorporation of the burners in the burner muffle a number of three solid burners is selected as an optimum arrangement. Each solid burner then has to provide a power of 4.6 MW. In case of a regulating range of an individual solid burner of 1:4 there is a minimum power of 1.15 MW. One thus even falls short of the necessary heat quantity of 1.695 MW and the regulating range of an individual solid burner of 1:4 is extended to a regulating range of the inventive multiple burner with three solid burners to 1:12.

According to the heat requirement only one solid burner of the multiple burner arrangement or two or all three fuel burners can be brought into operation. The overall regulating ratio then lies for the hot gas generator with three solid burners at 1:12.

Such a value is achieved also only in exceptional cases with gas burners.

The inventive multiple solid burner arrangement on or in the burner muffle of a hot gas generator thus facilitates in an extraordinarily efficient manner the production of hot gases, grinding-drying installations and other thermal installations. The use of solid fuels, for example brown coal dust, which is considerably more cost-effective in comparison with heating oil and combustion gases and is additionally available in adequate quantity, is particularly advantageous. When using blast furnace gas or synthesis gas to produce hot gases for drying purposes, in particular in coal grinding installations, a substitution with coal dust can be carried out.

The invention is explained in further detail below by reference to a description of the figures. These show in a greatly schematised representation:

FIG. 1 an axial longitudinal section through an inventive hot gas generator with a multiple solid burner and

FIG. 2 a top view according to line II-II in FIG. 1.

FIGS. 1 and 2 show a hot gas generator with a multiple solid burner 10, which consists in this example of three solid burners 3, 4, 5.

It follows from FIG. 1 with two illustrated solid burners 3, 4 that a solid feed 6 and a combustion air feed 7 are assigned to each solid burner 3, 4, 5 and that the solid burners 3, 4, 5 are arranged in a burner plate 12 of a burner muffle 2. The burner muffle 2 and a subsequently arranged mixing component 9 are vertically orientated like the solid burners 3, 4, 5 and a start burner 8.

Impulse burners for coal dust, for example brown coal dust, are used as solid burners 3, 4, 5, which comprise a conically extending reaction chamber 16 with a conically tapering flame accelerating nozzle 17, an injection lance 18 with deflection hood 19 for injecting fluidised coal dust and a radial blade cascade 25 on the burner head, through which combustion air passes into the reaction chamber 16, whereby this enters via a lateral inlet opening 7 into an air housing 28 and passes from here to the radial blade cascade 25 and the reaction chamber 16.

The impulse burners fired with solid fuels have a high flame jet speed and a flame 30 extends, as shown in FIG. 1, through the burner muffle 2 into the mixing component 9.

If no solid fuel is available the impulse burners can be switched to gas in order to be able to maintain the operation of subsequent installations. Gas feeds 27 follow, besides the solid feeds 6, from FIG. 1 to the solid or impulse burners 3, 4 visible here.

In the mixing component 9 the heating and mixing of the combustion gases produced in the multiple solid burner 10 with process gas 13 to be heated, which is fed via a feed means 11, take place.

The feed means 11 surrounds, with its radial housing, the burner muffle 2, into which the solid burners 3, 4, 5 extend with their reaction chamber 16 and the flame accelerating nozzle 17.

The burner muffle 2 is lined in this embodiment with a fire-resistant material 15. The fire-resistant lining can also be omitted. A perforated jacket unit 20 is connected to the burner muffle 2 on the outlet side and thus opposite the multiple solid burner arrangement 10 in the burner plate 12 as a mixing component 9. This perforated jacket unit 20 is part of the steel combustion chamber and consists of a plurality of cylindrical and coaxial perforated jackets 21 with enlarging diameters. Annular gaps 22 for flowing in of the gas 13 to be heated are formed between the individual perforated jackets 21 and an annular channel 24 is formed between the perforated jackets 21 and an outer closed sheet steel material 23, into which annular channel 24 the gas 13 to be heated is fed from the feed means 11 and then via the annular gaps 22 and holes of the perforated jacket 21 into the mixing chamber 26. The hot gas 14 formed is removed via an outlet opening 29.

FIG. 2 shows a top view of the hot gas generator at the height of the burner plate 12 of the burner muffle 2 with the spiral housing of the feed means 11 for the gas to be heated arranged on the periphery of the burner muffle 2. A start burner 8, which is operated with gas or oil, is arranged in the centre of the burner plate 12 and the three solid burners 3, 4, 5 extend coaxially and at the same distance from each other and from the start burner 8 vertically downwards.

The solid burners 3, 4, 5 used as impulse burners are also suited for the combustion of gases. If no coal dust is available in case of interruption, the impulse burners can be switched without problems to natural gas, synthesis gas or blast furnace gas so that the operation of the subsequent installations, for example of a power station in coal gasification, a blast furnace in PCI plants, etc., can be maintained.

An essential advantage of the inventive multiple fuel burner is the extension of the field of use of hot gas generators with solid burners.

The use of a hot gas generator with multiple fuel burners, in particular multiple impulse burners, is a possibility in coal gasification plants and in PCI plants in the steel industry and for non-ferrous metallurgical processes and also in general heat-based installations. The synthesis gas produced in the coal gasification can thereby be advantageously used in the energy producing industry and increasingly in the plastics industry. If on the other hand synthesis gas is branched off as an energy carrier for the grinding-drying process this requires, with the usual heat outputs of between 10 and 30 MW, synthesis gas quantities of 3300 m_N³/h to 10,000 m_N³/h with a calorific value of the synthesis gas of approximately 11,000 kJ/m_N³. This represents a considerable loss for the intended use. Blast furnace gas from the steel industry has in the meantime also been used increasingly frequently in special power stations for power generation. The use of coal dust for hot gas generation avoids the use of the abovementioned gases and other fuels such as light and heavy oil, natural gas, etc. in hot gas generators and is extraordinarily advantageous having regard to energy and investment.

Claims

1. Solid fired hot gas generator with an extended regulating range,

characterised in that

a plurality of solid burners are arranged in a burner muffle and a multiple solid burner is formed,

an independent solid feed and combustion air feed are assigned to each solid burner and

the firing power of the multiple solid burner can be regulated from the minimum power of a solid burner to the maximum power of all solid burners so that load regions of a subsequent installation unit, to which the hot gas produced in the hot gas generator is fed, are covered.

2. Hot gas generator according to claim 1,

with a start burner which is arranged in a burner plate of the burner muffle,

with a feed means for gas to be heated and

with a mixing component arranged after the burner muffle, in which the combustion gas produced is mixed with the gas to be heated,

characterised in that

a plurality of solid burners are arranged coaxially to the start burner and are fixed in the burner plate of the burner muffle.

3. Hot gas generator according to claim 1,

characterised in that

solid burners of the same size or different sizes form a multiple solid burner.

4. Hot gas generator according to claim 2,

characterised in that

three solid burners are arranged with an equal angular distance from each other and with an equal radial distance from the start burner in the burner plate.

5. Hot gas generator according to claim 1,

characterised in that

the solid burners are arranged at a defined angle to the longitudinal axis of the burner muffle.

6. Hot gas generator according to claim 1,

characterised in that

a dosing means is provided for a separate, dosed solid feed to each solid burner.

7. Hot gas generator according claim 1,

characterised in that

dust-form fuel, in particular coal dust or biomass dust, can be fed in fluidised form to the solid burners.

8. Hot gas generator according to claim 1,

characterised in that

impulse burners, in particular for hard coal dust, brown coal dust, petroleum coke dust, biomass dust and dust mixtures, are arranged as solid burners, which respectively comprise a conically extending reaction chamber, possibly with a conically tapering flame accelerating nozzle, and an injection lance with deflection hood for the fluidised, dust-form fuel and a radial blade cascade for supplying combustion air.

9. Hot gas generator according to claim 8,

characterised in that

the impulse burners used as solid burners can be switched to gas and operated for example with natural gas, synthesis gas or blast furnace gas.

10. Hot gas generator according to claim 1,

characterised in that

a perforated jacket unit (LOMA) with a plurality of cylindrical and coaxial perforated jackets, with annular gaps between the perforated jackets and with an annular channel between the perforated jackets and an outer, closed sheet steel jacket is disposed as a mixing component.

11. Hot gas generator according to claim 1,

characterised by

use in coal gasification plants, PCI plants in the steel industry and in non-ferrous metallurgical processes, in the cement industry and in general heat-based installations.