DE4208951A1 - Hot gas producing heater - has burner using heat value of poor gas for heating process air with heat passing through hole cover for application to air - Google Patents

Abstract

Poor gas and combustion air are fed to a burner and, at least at the outlet side,are mixed. Connecting on the outlet side to the burner is a muffler. At least peripherally in the outlet area of the burner muffler is an inlet for process air to be heated. The burner (18) is of the multi-lance type (3) with poor gas-combustion air nozzles (5,15) one enclosing the other. For the burner muffler is provided a hole cover (11-14) of metal into which flows the process air (P) to be heated. USE/ADVANTAGE - A hot gas producer burning poor gas or top gas, which produces heat economically, and which is efficient from a wt. and combustion technique viewpoint.

Description

The invention relates to a hot gas generator with weak Gas burner according to the preamble of claim 1.

Such hot gas generators with lean gas burners are known in particular from the smelting process of iron ores. In the smelting of iron ores in the blast furnace process, there are gaseous products which are sufficiently known under the name "top gases" and which to a certain extent consist of combustible constituents (CO; H ₂ ) but predominantly from inert gaseous constituents (CO ₂ , N ₂ ) exist.

The term "lean gas" is primarily based on top gas, but this should not be understood as a limitation. The term lean gas used in the context of this invention therefore relates to a range of the specific heat content or the heat density of less than 1200 kcal / standard cubic meter or approximately 5 MJ / m ³ .

The combination of a lean gas burner with a hot gas It is therefore a producer in many process engineering processes considered desirable in which weak gases occur len and accordingly used and ent must be taken care of, above all it is desirable is worth, by means of its relatively low calorific value Lean gases to heat up existing process air in order to this heated process air drying processes or the to be able to carry out the same in the procedure.  

The previous designs of hot gas generators with Lean gas burners, however, have the serious disadvantage that for a technically optimal burnout, the burning always completely fire with the downstream mixing chamber part must be firmly bricked up. Above all under the Aspect of an optimal burnout level, e.g. B. of CO content in the flue gas has been very long and large so far voluminous combustion chambers required. Such hot gas Producers, consisting of combustion chamber and mixing chamber, have considerable weight on what is of the design and Statics, but also from the heat economy considerable disadvantages.

The problem of efficient lean gas combustion wins but of great importance, since the weak gases of the aforementioned Type in a wide variety of technical processes len and in most cases only very poorly or with very high expenditure on equipment for a combustion with good Burnout level can be subjected. These weak gases consist to a large extent of inert, ie not flammable components, so that the combustion accessible components, sometimes in very low concentrations trations, which is reflected in the low calorific values of the Lean gases find their expression.

Such low gas fuels, as they are called "waste product te "or by-products from a wide variety of processes are known, e.g. B. top gas or smoldering gas from the aluminum nium recycling or the like are the majority characterized that its main component, the burned carbon monoxide (CO).  

Gases of the aforementioned type mostly have CO contents which are well below 45% by volume, while the main constituents can be non-combustible components, such as CO ₂ and N ₂ . Other flammable gaseous constituents, like other, very different, gaseous organic compounds can also be added to the gases designated here as "lean gas".

Conventional lean gas burners are constructive Solution always in connection with the design of the Ver combustion chamber or the combustion chamber housing. With these units, the combustion chamber comes into play to the extent that it almost always supports combustion function. This is usually a complete fireproof bricked combustion chamber with burner muffle and combustion chamber housing provided. Added to this is this Interpretation that the dimensioning of the combustion chamber and spe target the dimension of the burner muffle depending on the required mixing effects are taken. This means that with conventional lean gas burners Hot gas generators a very high cost in which the Ver combustion-supporting combustion chamber construction operated will, resulting in relatively large dimensions of the focal chamber on the one hand and solid, fireproof linings on the other hand, which ultimately leads to an uneconomical Chen order of magnitude of the combined unit.

For conventional hot gas generators with a low gas burner the lean gas to be burned is often replaced by a tan potential feed in the burner head in a more or less intensely rotating movement. The lean gas flow and the combustion air is usually too next fed to the burner via two separate chambers, the one medium possibly in the manner of a spiral  shaped opening with the other medium in the actual Combustion chamber is flown. The mix between Lean gas and combustion air therefore only take place in the Combustion chamber, so to speak, with the combustion process running.

An example of such a burner is from "Burning and firing "(Rudolf Günther, Springer-Verlag, Ber lin 1974, p. 227, Fig. 4.91).

In order to use the burner design and inflow technology of the guarantee the media a sufficiently good combustion To be able to, it is necessary to have the combustion chamber as possible dimensioned large, so sufficient combustion times are available.

In addition, it is necessary with these units, one that To create combustion-supporting "hot" surroundings which is realized in that the combustion chamber is very long and fireproof lined is created. These fireproof Linings are heated to high temperatures and thus support the combustion process, which ultimately Lich, but with considerable disadvantages, too a satisfactory burnout result is achievable.

Known units of a hot gas generator with combined Low gas burners therefore require due to the massive Design with fireproof linings for the entire furnace chamber high unit weights. There is also a long start-up time in order to apply the refractory linings to the mostly to be able to heat up the focal temperatures, which entails considerable start-up costs. Most is too which is a continuously operated burner that not only is used as a start or pilot burner, required to maintain the continuous and good combustion hold. But also the shutdown, i.e. switching off, this Ag  gregates is associated with problems because in these aggregates there is a very large amount of storage heat. In cases an emergency shutdown must prevent this storage heat damage caused by overheating. Out for this reason it is with such conventional hot gas producers with lean gas burners required an emergency Install chimney through which the storage heat in the event can be dissipated from rapid shutdown measures. For this a sufficient amount of cooling air is required to the hot gas generator. In the event of a power failure, the Cooling air unit types operated by emergency generator will hold.

Based on these disadvantages with known hot gas produce with low gas burners, especially for the Combustion of top gas are designed, it is the job of Invention, a device with a hot gas generator Lean gas burner economical, weight and to be more efficient in terms of combustion technology than previous ones Constructions.

This object is achieved by the features of characterizing part of claim 1 solved.

An essential idea of the invention is therefore on the one hand the design of the lean gas burner in that there an optimal mixture between the one to be burned Lean gas and the required combustion air on very short space is reached. For this, the burner in the we considerably designed as a multi-lance burner in which the ver combustion air and the lean gas over each other Nozzles into the combustion chamber at high speed flow so that a high combustion surface in the Hin view of optimal combustion of the lean gas is fathered. On the other hand, however, it is assumed that the combustion chamber required to heat the process air  to be designed as a chamber with a refractory lining equip, but instead a perforated jacket device preferably choose sheet steel sheaths that are roughly coaxial and merge into one another with an annular gap. Because of the measures and a relatively short burner muffle is sufficient with the object or aggre according to the invention gat considerable weight savings in the overall system. The constructive measures carried out therefore lead to lean gas combustion even at low calorific values in the range of 1000 kcal / m (normal state) with a independent combustion process, so that only one Start burner is required. By means of this starter ners the burner muffle is briefly z. B. in an An travel time from 10 to 15 min. to the required tem heated up temperature. The intense mixing of the weak gases with the necessary combustion air allow it but also to provide a very short burner muffle that then due to the substantial combustion of the Dimension of the burner muffle a perforated jacket device connects to the inflow of the process gas to be heated.

This combination of a relatively short burner muffle with a perforated casing device, e.g. B. made of sheet steel considerable advantages with regard to the heating industry Such a facility, since only very little memory Heat is required during the start-up process. Even with the Ab the entire unit can shut down very quickly can be switched without the need for emergency fireplaces. In addition, there is a very wide range of rules for the Follow-up processes required amount of heat, this both on the good controllability of the incoming Low gas as well as the supplied process air back is feasible. In addition, the invention excels appropriate aggregate also due to the good resilience in the rear look at strong temperature changes.  

The unit according to the invention is therefore designed such that within the very short burner muffle, the more appropriate wise in a ratio of 1: 3 to 1: 5 to the length of the Perforated device stands out by a fanned out short Flame and that by means of high flow velocities Low-gas and combustion air meter injected via nozzles serve an intensive mixing with subsequent high Burning degree of the combustible components of the lean gas is enough.

For this purpose, it is expedient to provide the top gas and to divide the combustion air into many individual flows where for the two media via interlocking nozzles for Burner outlet. Through swirl inserts, esp special gas-side and air-side nozzle bores that it allow the combustion air portion to be at right angles in the individual gas flows occurs, the contact and reaction areas of the two media are enlarged sert.

In addition, even at high exit speeds Media from the nozzles through the occurring on the edges local vortex good mixing and support guaranteed safe ignition.

The optimal mixing of the two react with each other the media should also allow the rated output carefully adjust the mixture down considerably can. On the other hand, it is also conceivable that the gas quantity can be increased considerably with sufficient pre-pressure can without fear of the flame breaking off.

The individual pipes or lances through which the burns air or alternatively the gas to the burner outlet over the nozzles are at least in  Nozzle area made of highly heat-resistant material, to burn or melt the nozzles, too Avoid lean gas combustion.

To illustrate the advantages of the invention Aggregate will be achieved, especially with regard to the dimensional dimensions are given in the following example:

For the combustion of blast furnace gas in a hot gas generator according to the invention, the axial length of the burner muffle was approx. At approx. 6.8 × 10 ⁶ kcal / h, which corresponds to a blast furnace gas throughput of approx. 9,500 m ³ / h (standard state). 2 m selected, with good burn-out results being achieved at the burner muffle outlet. The combustion took place in a temperature range greater than 700 ° C.

As part of a flue gas analysis, the combustion chamber escapes CO values between 50 and 250 ppm, which characterized the very high degree of burnout.

The subsequent mixing room section, which is connected to the burner socket fel connects, and in their area the pro to be heated zeßluft is flown, is according to the invention from a perforated jacket device, in particular from perforated Sheet steel, surrounded. These perforated cylinder jackets be act that the z. B. rotating over a volute process air to be heated up the hot flue gases from keeps the steel perforated jacket, so to speak cool, and on on the other hand, the smoke gases emerging from the flame if set in a rotating movement, thus a good streak-free mixture between flue gas and Process air is reached.  

Especially with regard to the previously required refractories material lining along the entire length of burner muffle and mixing chamber shows the blatant front part of the unit according to the invention.

In a comparison with a conventional hot gas generator with the aforementioned heat output of 6.8 × 10 ⁶ kcal / h, a fireproof brick chamber of approx. 7 m in length would be required, this combustion chamber having a wider space of approx. 2 m in length for mixing the process air to be heated should be connected. This would result in a total length of approx. 9 m. Because of the high temperatures, this total length would have to be fire-resistant.

Assume a combustion chamber diameter of approximately 2.2 m and a wall thickness of approx. 200 mm of the refractory material, this would result in a weight over this total length of 9 m the refractory lining of about 25 t.

In an aggregate according to the invention there is only one Ge weight of refractory material of about 2.5 t contrary to what corresponds to only 10% of the conventional weight.

When considering the control and heat economy speed of the unit according to the invention with a conventional Chen, previously outlined hot gas generator shows the Er There are also serious advantages in this regard.

From the following consideration, the serious Un differed in the storage heat absorption of the corresponding Combustion chambers very clearly.

At an average temperature of the above-mentioned clothing 800 ° C and a specific heat mecapacity for the refractory material of 0.21 kcal / kg × grd.,  For example, the following amounts of fuel are available heat the corresponding combustion chambers when starting conducive:

Conventional combustion chamber
M = 0.21 kcal / kg × grd. X 25,000 kg x 800 ° C;
M = 4.2 × 10⁶ Kcal
Requirement = 420 kg of heating oil;

Combustion chamber according to the invention
M = 21 kcal / kg × grd. X 2500 kg x 800 ° C;
M = 0.42 × 10⁶ Kcal
Requirement = 42 kg heating oil.

From this it can be seen that in a conventional burning chamber that has to be applied about ten times as much energy, to the mass of refractory materials to the desired one Operating temperature z. B. to be able to heat up when starting.

When shutting down, i.e. switching off the system, this is due to conventional units that this over many hours Cooling process must be subjected to the heat ge usually has to be driven over the roof in order to following consumption, otherwise supplied with heated process air not endanger or damage.

In an aggregate according to the invention are therefore unnecessary an emergency chimney and heat-resistant butterfly valves for this.

Although the advantages of the unit according to the invention are straight in the combination of the hot gas generator with the lean gas torch and the specific design come into play,  it is also conceivable that the so constructed and out created lean gas burners as an independent invention ke can be used.

As an alternative, both the air outlet nozzles can be located inside and be surrounded by gas nozzles, and the media can be charged in reverse. This design allows low gases to be optimally burned up to a range of around 600 kcal / m ³ (standard condition) and used for hot gas generation.

The burner muffle in the aggregate according to the invention switched perforated jacket device makes by the type and Way of the flow characteristic of the process air into the Mixing chamber a refractory lining of the mixing chamber part not necessary because the process air to be heated is the cylindrical steel jacket of the pipe jacket cools. Farther is made by the spiral process air The muffle escaping hot flue gases into a spiral shaped movement and it succeeds with the next Cooling effect a very intensive mixing between the hot flue gases and the process air to be heated.

This device according to the invention offers the possibility Lean gases of various origins for thermal hosts economic processes in which previously existed preferably high-quality energy sources such as oils, natural gases, Coal etc. can be used. Of particular note are thermal, process engineering and cost aspects. Also due to the ver one is always in harsh environmental protection conditions increasing efforts to produce gaseous products for To use purposes that are normally only used in very little or not at all technical Lean gases recycled. A variety of these products  were and still are burned to this day without whose energy content is used. The resulting Smoke gases are simply emitted into the atmosphere.

By means of the unit according to the invention, the emission of environmentally harmful flue gas components, such as CO, soot, NO _x , can therefore be considerably minimized, so that the legal standards can also be achieved thereby.

Thus, the proportion of CO with the Ag according to the invention lean gas between 18 vol.% and approx. 30 Vol .-% lie.

A particularly preferred application for the Invention appropriate aggregate can ge in the smelting of iron ores will see. These processes have been around for years that strives for the reduction process in smelting it to partially replace required coke with coal dust This could mean that the polluting Effects in coke production are reduced to others could coal directly without the intermediate stage of Ver Kokung are used, which leads to considerable cost savings would lead.

The direct use of coal, however, requires that this must be dried, for which a dry is just now tion process with heated in the unit according to the invention Process air when using the energy content of Would then offer lean gas.

Another area of application for the combustion of strongly CO-containing weak gases occurs in connection with the gasification of coal. The efficiency could also of power plants as part of minimizing flue gas emissions by means of the method according to the invention be improved.

The invention is described below using a schematic Embodiment explained in more detail. Show it:

Fig. 1 shows an axial longitudinal section through a unit according to the invention with a specifically designed burner in the right area and a perforated jacket device in the left area, and

FIG. 2 shows a radial section along the line AA according to FIG. 1.

An example of a hot gas generator device 10 is shown schematically in Fig. 1 in longitudinal section. The device, which is largely coaxial to the longitudinal axis, has a start burner 1 with air supply L and natural gas supply E in the right area. This start burner 1 is followed by an air housing 2 with feed connector for the combustion air L. The air housing 2 is coupled to a gas chamber 4 , in which the blast furnace gas is passed through a feed pipe.

These previously mentioned assemblies of the starting burner 1 , the air housing 2 and the gas chamber 4 essentially represent the lean gas burner 18 .

The air is supplied from the air housing 2 to the outlet of the burner 18 via individual pipes 3 or lances which penetrate the gas chamber and are surrounded on the outlet side in the example by gas nozzles 5 . The division of the combustion air and the supplied top gas into individual streams, which enter the combustion chamber via the nozzles 15 and 5 , therefore causes intensive mixing and surface enlargement, so that in the burner muffle 6 adjoining to the left, a relatively short-flame optimal combustion of the lean gas , especially gout gases, can be realized.

The burner muffle 6 is made of refractory material, e.g. B. chamotte, lined, a rod-shaped thermocouple 7 must be provided in the wall of the combustion chamber to measure and control the inner wall temperature. A UV cell 17 is also seen at the burner inlet.

The burner muffle 6 is from the outside of a Spiralge housing 8 for supplying the process air to be heated P ben. From this volute casing 8 , on the one hand, a protective jacket 9 and, in the case of game 4, telescopically interlocking perforated jackets 11 , 12 , 13 and 14 extend to the left in the direction parallel to the axis. In particular, the perforated sheaths 11 to 14 and the protective sheath 9 are expediently made of sheet steel. From right to left in the direction of the burner flame and radiation, a diameter enlargement of the individual perforated sheaths is provided, annular gaps 16 being formed at the step-like transition region through which the process air flows. The perforated jackets 11 to 14 are equipped with a large number of holes 17 , so that an optimal flow of the colder process air into the flue gas flow is possible over this and over the annular gaps.

This inflowing colder process air P causes cooling of the perforated shells 11 to 14 on the one hand and on the other hand by a correspondingly constructive design a spiral-like sheathing of the flue gases generated before the flame, so that guidance and simultaneous cooling takes place in this area.

In the illustration of FIG. 2 is a radial section along illustrated line AA. Here, the design of the burner 18 coaxial to the axis with a plurality of Lan zen 3 can be seen . In the chambers for the combustion air and the blast furnace gas, there is initially a kind of tangential flow, which, however, is divided in terms of pressure into individual lances or nozzles, the diameter reduction of which enables uniform application across the entire cross section of the chamber.

The unit according to the invention is therefore due to the combination nation of a lean gas burner, especially a low pressure-lean gas multi-lance burner with a perforated jacket device marked, on the one hand in the burner optimal mixing with technically complete ver Burning the lean gas is achieved so that at the end very low CO concentrations occur in the combustion chamber be enough. This combustion process is with the ge weight-saving measure of a perforated jacket device com which is stabilized by its flow Total combustion under heat economy most important aspects.

Claims (8)

1. hot gas generator with lean gas burner, the lean gas burner lean gas and combustion air being supplied, which are mixed at least on the outlet side,
with a burner muffle and
with an inflow device for the process to be heated, which is provided at least circumferentially in the outlet region of the burner muffle and is largely parallel to the axis of the burner muffle, characterized in that
that the burner ( 18 ) is designed as a multi-lance burner ( 3 ) with surrounding lean gas combustion air nozzles ( 5 , 15 ),
that the burner muffle ( 6 ) a subsequent hole jacket device ( 11 to 14 ) made of metal for a flow of the process air to be heated (P) is assigned, and
that the burner muffle ( 6 ) is designed to be substantially shorter in the axial direction in relation to the perforated jacket device ( 11 to 14 ). 2. Hot gas generator according to claim 1, characterized in that the ratio of the axial length of the burner muffle ( 6 ) to the perforated jacket device ( 11 to 14 ) is approximately 1: 3 to 1: 5. 3. Hot gas generator according to one of claims 1 or 2, characterized in that the perforated jacket device ( 11 to 14 ) in the axial direction several, largely cylindrical and coaxial perforated jackets ( 11 , 12 , 13 , 14 ) that the perforated jackets ( 11 to 14 ) are arranged interlocking with increasing diameter in the axial direction and form at their transitions an annular gap ( 16 ) for the inflow of process air to be heated. 4. Hot gas generator according to one of claims 1 to 3, characterized in that the perforated casing device has inner, perforated sheet steel jackets ( 11 , 12 , 13 , 14 ) and an outer, closed sheet steel jacket ( 9 ) which for guiding the incoming process air (P) serve. 5. Hot gas generator according to one of claims 1 to 4, characterized in that a starting burner ( 1 ) is provided which can be switched off after a short start-up time. 6. Hot gas generator according to one of claims 1 to 5, characterized in that in the burner ( 18 ) a plurality of individual flow distributions ( 3 ) of the combustion air (L) and the lean gas (G) is provided, and that the outlet side of the burner ( 18 ) interlocking outlet nozzles ( 5 , 15 ) of both media are provided. 7. hot gas generator according to claim 6, characterized,  that swirl inserts and / or radially directed nozzles holes are provided. 8. Hot gas generator according to one of claims 1 to 7, characterized in that only the burner muffle ( 6 ) is lined with refractory material.