ES2377499T3 - Mixture of fuels for feeding to blow nozzles in the production of cast iron in blast furnace and procedure and installation for the manufacture and feeding of the fuel mixture - Google Patents

Abstract

The invention relates to a fuel mixture that is to be delivered into tuyeres during the production of pig iron in a blast furnace as well as a method and devices for the production and delivery of the fuel system. In order to optimize the production of pig iron in blast furnaces, an inventive fuel system is provided which is to be blown in according to the PCI method via tuyeres and can be produced in an extraordinarily simple and efficient manner. Said fuel mixture comprises a ready-to-inject coal dust-cinder mixture which is produced by joint grinding, especially in a vertical rolling mill. The invention makes it possible to improve the blast furnace process while allowing extraordinarily efficient utilization of the especially oil-contaminated cinder materials obtained in milling processes.

Description

Mixture of fuels for feeding to blow nozzles in the production of cast iron in blast furnace and procedure and installation for the manufacture and feeding of the fuel mixture

The invention relates to a mixture of fuels for feeding to blow nozzles in the production of cast iron in blast furnace according to the general concept of claim 1 and to a method of preparing and feeding the fuel mixture according to the general concept of the claim 7.

It is known that, in the production of pig iron in blast furnaces, for a decrease in the consumption of coke with the hot air draft that is introduced by means of the air draft or blow nozzles at the bottom of the etching other substances are also injected reducers and heaters, for example coal powder, oil or natural gas, the PCI (pulverized carbon injection) process being used for coal dust, in particular.

In the company brochure "Pulverized Coal Injection Systems" by Paul Wurth S.A. from 05/2002, milling facilities are described to produce powder coal systems and distribution and feeding systems for pneumatic feeding of powdered coal in blast furnace nozzles according to the PCI procedure.

WO 99/64636 describes a process in which powdered carbon prepared with catalyst addition is injected. As catalysts, aqueous solutions of compounds of the elements of the zirconium, molybdenum, tungsten, manganese, iron, cobalt, nickel, copper, zinc or aluminum, tin or lead subgroups are recommended, in particular a copper sulfate solution.

In the article "Blast furnace efficiency enhancer for pulverized coal injection" of the magazine "Steel Technology", February 2000, page 61 and following, the mentioned procedure is described in more detail. The powdered coal fed through the blow nozzles for partial coke replacement has a grain size <1 mm and a moisture content <3%, and is fed per ton of coal from 350 to 600 ml of catalyst. The feeding is carried out using a special device that is arranged after the raw coal silo and before the MPS mill, the raw coal being prepared by spraying with the catalyst solution. The disadvantage is that the spraying device must meet special requirements due to the corrosive properties of the catalyst solution and a cleaning system is additionally necessary to regularly clean the nozzles.

From DE 100 50 332 A1 a process and a device for the preparation of fuels, in particular coal powder, for the production of pig iron are known, in which a catalyst containing cerium salts and acidic iron salts is used organic and / or inorganic and causes a reduction in the ignition temperature and acceleration of combustion and, thus, faster combustion of residual coke. The preparation of the powdered coal is carried out with an aqueous solution of the catalyst during the grinding of the raw coal to give powdered carbon. The coal mill, for example a roller mill with air flow of the LOESCHE type, must be equipped for the preparation of the powdered coal with the corresponding feeding devices and spraying devices. Measuring and regulating devices that must be included in the technical concept of regulation and safety of the grinding plant as a whole and are associated with additional investments and costs are necessary to achieve an effective wetting of the carbon particles.

From DE 41 04 072 A1 a recycling process for rolling mill scale containing oil is known in which the rolling mill is milled and dried as an additive with coal intended for injection in the blast furnace and then injected as Powdered fuel to the blast furnace. Mixtures of fuels described may contain coal and rolling scale containing oil or if not drying laminate and mineral oil dried or if not rolling scale, which has been crushed and dried with a reduced amount of coal, and mineral oil . The proportion of the rolling scale in a mixture of scale and coal is indicated to be 5 to 20%, preferably 6 to 8%. A relatively higher proportion of this type of scale in the fuel mixture can, however, cause lumps to form before and during the grinding process and cause problems in feeding the mixture through the blow nozzles and also a increased corrosion, particularly in the region of the feed line, nozzles and dosing valves. It can also be found that the use of untreated laminate husks having a relatively high proportion of oil and water is a disadvantage. In addition, a heat conservation of the coal and husk mixture to be injected that requires additional devices and costs is described.

The invention is based on providing a mixture of fuels for feeding through blown nozzles of a blast furnace and on a process for preparing and feeding the fuel mixture that leads to an extraordinarily effective preparation and feeding of the fuel mixture for obtain an improved combustion behavior and an optimized blast furnace process.

The objective is achieved, in relation to the fuel mixture, by means of the characteristics of claim 1 and with respect to the process by means of the characteristics of claim 7.

The invention is based on the basic idea that a mixture of fuels of at least one solid carbon support and a scale material is used as a previously reduced iron material and is fed together with the draft of hot air and / or oxygen through of the air draft or blown nozzles, for example according to the PCI procedure.

As solid carbon supports, coal, for example coal, but also lignite, granulated carbon, coal mixtures, mixtures of coal and coke, and plastics, for example as mixtures of plastics and coal or plastic suspensions in oil, can be used and fed. together with a husk material as a previously reduced iron material with a grain size that can be predetermined through blasting nozzles in the blast furnace.

Preferably, a mixture of fuels containing carbon solid support or a mixture of coal and petroleum coke is used as the support for rolling shells.

It is particularly advantageous that the mixture according to the invention can be subjected to a joint grinding process, suitably a grinding and drying process, in a mill, in particular in a roller mill with integrated sorter, for example in a mill mill with LOESCHE air flow, and feed the blow nozzles with a grain size that can be predetermined.

Basically, the carbon supports or the raw fuel material and the scale material can be ground separately in a suitable mill or in a grinding system and fed together in a particularly adjustable mixing ratio or also separately to the blow nozzles of the blast furnace. It is particularly economical and preferred, however, a joint grinding and sorting process, for example in a roller mill with air flow.

It has been found that a mixture of coal powder and scale in which the proportion of scale is 3%, is a mixture prepared for injection that can be transported pneumatically that can be ground extraordinarily economically and effectively leads to a combustion behavior significantly Improved in the blast furnace and can also lead to a reduced collection of unburned coal.

In comparison with the normal combustion of coal and with the known PCI procedure, a clear acceleration of the combustion of the reducer has been determined, in particular of the powdered coal introduced, in particular of the powdered coal introduced and at least partially of the coke. In addition, it is advantageous that due to the addition of scale in the injection of powdered coal a reduced amount of fed ore and reductant per ton of pig iron production should be used. It has also been determined that by the addition according to the invention of husk to the coal powder a reduction of the flame temperature is achieved, whereby the addition of oxygen and, thereby, the surface yield of the crucible can be increased.

In addition, there is an essential advantage of the fuel and scale mixture in the economical and efficient evaluation of the scale material, in particular of the rolling scale produced in the rolling processes and similarly in relatively large quantities. Essentially, the husk is an iron oxide (II, III) (Fe3O4 = FeO Fe2O3) formed in hot forming and heat treatment on a steel surface, which has associated mixtures of calcium oxide CaO, silicon dioxide SiO2, aluminum oxide Al2O3, sodium oxide Na2O, magnesium oxide MgO, manganese and sulfur traces, P2O5, TiO2, Zn, Zr, Cu, Cr, Co, V, Ni and Pb and which is released by rolling or al Forging (laminate or calamine scale) or is removed by washing, spraying or also by peeling or rolling the steel surface.

The iron content in the rolling mill can be between 30 and 80%, so that an assessment is effective through an economic aspect and also from an environmental point of view. To date, a valuation has been carried out in the form of a rolling scale in pellets or in briquettes that, together with the blast furnace coke and loaded by means of the top of the top, is fed to a blast furnace. However, the need for pelletization and briquetting, which requires additional procedural steps, is disadvantageous.

According to the process according to the invention for the preparation and feeding of the fuel mixture according to the invention, at least one solid carbon support or also a mixture of two or more carbon supports and a husk material as a material containing reduced iron are fed prior to a mill and they are ground together and fed with a grain size that can be predetermined according to the PCI procedure through blow nozzles to a blast furnace.

According to the invention, a mill is fed, for example, to a roller mill with integrated sorter, as a solid carbon support or as a raw material of coal fuel, in particular coal or lignite, or a mixture of coal and petroleum coke and a husk material, for example rolling sheeting, which can have a metal or iron content between 30 and 80%, in a mixing ratio that can be predetermined and still undergoes grinding and sorting process.

According to the invention the proportion of husks in the feed mixture is 3%.

It is suitable to use a raw material or a mixture of fuels with a calorific value> 3000 kcal / kg, a humidity of approximately 15% and a feed grain size <10 to 80 mm.

The rolling mill can be transported to the mill feed separately to the raw fuel material and first add the fuel material or the fuel particles to the mill. It is advantageous for the grinding and sorting process and the desired grinding product, however, to previously connect a mixing device to the coal mill, for example a mixing bed or a mixing drum, and to feed the crude fuel material with the husk material as a feed mixture, grind it and separate the mixture of fine material after the sorter into a filter and feed it as a fuel mixture prepared for injection into the blasting nozzles of the blast furnace.

It is advantageous for safety reasons to grind in an inert atmosphere. Using a hot gas, for example smoke gas, which is brought to the hot gas generator at the necessary temperature, moisture is removed from the feed mixture and the milling and drying process is carried out. The grinding can also be carried out by an air-operated grinding plant with hot air as a drying gas. Another possibility to feed hot gases for the milling and drying process is the use of waste gas from wind heater or Cowper gas.

In principle, the rolling scale can be obtained by mechanical peeling with a hydraulic cleaning process or by rolling and abrasion transport processes. Generally the husk has a high humidity (up to 90%) and is loaded with lubricating oils and greases from the rolling process. After a post-treatment, for example in a settling tank or by pressing processes, a water content in the range of 2 to 15%, an oil content between 0 and 5% and a grain size of grain can be obtained approximately 0.5 mm to a maximum of 50 mm.

The advantage is a mixture of coal feed and rolling scale. The raw coal in this mixture may have a grain size between 0 and 10 mm (Warndt coal) or between 0 and 50 mm. The grain size of the husk can be a maximum of 50 mm. The granulation after the mill is 50 to 80% <90 µm.

Basically, a joint grinding of raw coal or crude coal and petroleum coke and scale material can be carried out in all suitable milling systems and mills, for example in ball mills and vertical roller mills and the like. A mixture of coal / petroleum coke and husk material feed has no negative influence on the grinding process.

Surprisingly, it has been found that the overall grinding of the raw solid fuel material, in particular coal, and of the scale in a roller mill of the LOESCHE type can be carried out in an extraordinarily cost-effective, economical and efficient manner. In addition, it has been determined that the characteristic parameters of the milling process, such as, for example, the specific workload and the power factor of the mill, by adding a rolling mill to the coal or a mixture of coal and coke 3% oil, do not suffer any disadvantageous modification. Also the grain size distribution is almost identical, that is, there are only very small differences in the range of 50% R 90 µm to 0.05% R 90 µm, for example the specific workload between a ground from pure coal and ground with husks. With increasing proportions of scale in the fuel mixture, even a reduction in the workload of the mill was determined.

Particularly advantageous is an improved ignition behavior of the fuel and scale mixture in the blowing nozzles which can also be attributed to synergistic effects of the milling set of rolling scale and a crude fuel material. Thus, it has been determined that after the whole grinding process, scale particles adhere to the fuel particles and, despite the difference in density between the fuel and the scale particles, no separation or grinding takes place. neither in the classification nor during the feeding and injection according to the PCI procedure. It has been found, surprisingly, that the intimate bond between the carbon particles and the shell components significantly increases the acceleration of combustion.

Both components come into intimate contact in the framework of the grinding process through the crushing processes in each roller. It is accepted that the metal oxides present in the rolling mill are adhered, so to speak, in a lubricated manner, to the grain of coal or to the carbon particle. To this end, the oil residues present in the scale that contribute to the bonding process are also very advantageous.

or adhesion. This intimate union between the grain of coal to be burned and the components of the husk, which are metal oxides with a redox potential and catalytic activity, leads to a surprisingly improved combustion behavior of the powdered carbon particles. The combustion system according to the invention or the mixture of fuel and scale prepared for injection, therefore, provides not only the possibility of re-feeding the scale by-product in an extraordinarily simple and economical way to the production of pig iron, but also It is simultaneously associated with an optimization of the blast furnace process.

In addition, it is advantageous that due to the feeding of the rolling mill through the blowing nozzles the oil of the rolling mill is subjected to very high temperatures and the risk of the formation of harmful combustion products is very low. Therefore, no measures are necessary for encapsulating the oil adhered to the rolling mill, which is described, for example, in DE 100 38 566 A1.

In relation to the devices, it is provided according to the invention that a transport device and / or a dosing device for additionally disposing of the devices for the raw fuel material are provided in addition to the devices for the raw fuel material. the husk material deposited in a hopper or feed silo, for example rolling mill.

Alternatively, a pre-mixing device before the mill can be arranged for a premix of the mill scale or of the previously reduced iron material and of the crude fuel material, so that a feed mixture with a mixing ratio can be formed which can predetermined and can be fed to the ground, for example, by means of a dosing hopper.

In addition, it may be considered appropriate that after a filter in which the mixture of coal powder and scale of the mill is discharged and before a silo it is provided for the collection of the mixture prepared for injection another mixing device.

Generally, shipping containers or feeding vessels and a distribution silo are disposed after the silo of fine material, and the fuel mixture according to the invention is fed to the blasting nozzles of the blast furnace by injection injection.

It is advantageous that the fuel mixture according to the invention can be fed in the same way as powdered coal according to the PCI process through the blast nozzles of the blast furnace. We refer, for example, to the company prospect "Pulverized Coal Injection Systems" of the company Paul Wurth SA, which describes the usual feeding systems by shear force or pneumatically, and distribution and transport systems, including the dense and fluid current transport and measurement and regulation systems and a possible preheating of powdered coal in detail.

The invention will be further explained below by means of a drawing in which the single drawing shows a diagram of an installation to explain the mixture of fuels according to the invention and the course of the procedure and of the installation devices in a very schematic way.

In the process development four essential stages of the process can be recognized for preparing or using a new fuel mixture for blasting nozzles of a blast furnace.

In a first stage the preparation of the components for the fuel mixture 10 according to the invention is carried out, which is prepared by a joint grinding in a mill 2. In the present example, a roller mill with a flow stream is provided for the milling process. LOESCHE type air. However, other vertical roller mills or ball mills and the like can also be used.

The starting materials are at least one solid carbon support 6, for example coal, in particular coal or lignite, or a mixture of coal and petroleum coke, hereinafter referred to in abbreviated form as raw coal 6. The crude coal 6 is transported from a drain 8 to a raw coal hopper 16 and through a coal transport or distribution device 15 to a transport device 5, which is arranged before the mill 2.

As the second component, a scale material, for example a rolling scale, is conveyed as a previously reduced iron material 7, from a scale hopper 17 or a storage device using a scale transport or distribution device 14 to the transport device 5 for the preparation of a feed mixture 4.

Alternatively, the feed mixture 4 can also be prepared in a mixing bed or in a mixing drum, in which the raw coal and the husk material are mixed together and by means of a dosing hopper, the mill is fed (not shown). It is suitable to feed the feed mixture 4 of raw carbon 6 and rolling scale 7 to the mill 2 with a mixing ratio that can be predetermined.

In a second process step, the grinding of the inlet mixture 4 is carried out obtaining a fuel mixture prepared for injection 10. This is carried out in the present embodiment in a roller mill with air flow 2 and in inert operation. With the feeding of a heated or inert gas heated 9 to the necessary drying temperature in a hot gas generator 11, the feed mixture 4 is subjected to a grinding and drying process. The hot gas 9 can be advantageously conducted in a circuit (not shown) and the hot gas generator 11 can be operated, for example, with gaseous gas.

It is particularly advantageous that the grinding of the fuel and husk inlet mixture 4 can be carried out in the mill 2 in the same way as the grinding of the raw coal to obtain powdered coal. The feed laminate scale 7 has normally undergone a pretreatment to reduce the content of water and adhered oil. Through the grinding and drying process of the feed mixture 4 in the mill 2 with integrated sorter 3, a combustion system that optimizes the blast furnace process is prepared with the fuel mixture and scale prepared to inject 10.

In a post-connected filter 12, for example a fabric or sleeve filter, the fuel and scale mixture is discharged in powder form 10 and transported by a cell wheel 18 to a silo container 20.

The silo container 20 symbolizes with the rear device for pneumatic feeding of the fuel and scale mixture prepared for injection 10 the third process stage. This includes storage in the silo, regulation of the pneumatic feed of the fuel mixture and scale prepared for injection 10 using a pressure vessel with nitrogen 21, shipping containers or feeding vessels 22, 23 and a container of distribution 24 and a connection conduit or transport conduit 25. From the distribution vessel 24 the plurality of blow nozzles 27 correspondingly inject lines 26 for blow nozzles 27, through which the mixture of injects is injected

10 fuel and / or raw coal prepared for injection 10 together with the hot draft air.

Due to the high temperatures of approximately> 2000 ° C in the region of the blasting nozzles of the blast furnace the carbon of the fuel is burned giving carbon monoxide, which reduces the iron oxide of the minerals with formation of carbon dioxide to iron . Because in the case of the scale particles of the fuel and scale mixture, in particular, they are iron oxides, these are also reduced.

An essential advantage of the mixture of fuels according to the invention composed of a mixture of fuel and scale prepared for injection can be seen in that the amount of reducer for the scale, compared to a comparable amount of fed ore, is greatly reduced with relation to metal content. Simultaneously an assessment of a by-product is achieved. It is also advantageous that oil-contaminated husk material can be used particularly. It has also been shown that the feeding of the

The mixing of fuel and scale according to the invention through the blasting nozzles of the blast furnace leads to an optimization of the blast furnace process, for example by increasing the acceleration of combustion of the reducer, in particular of the carbon introduced with nozzles and at least partially also of coke. Other advantages are the economical and efficient preparation and feeding of the fuel mixture according to the invention.

Claims (12)

1. Mixture of fuels for feeding to blow nozzles in the production of pig iron in a blast furnace with at least one solid carbon support (6) and a scale material (7) that can be fed as a mixture of fuel and scale (10) prepared for injection through blow nozzles (27), characterized because, The fuel and scale mixture (10) prepared for injection is a mixture of coal powder and scale that can be pneumatically transported and has a proportion of 3% scale. 2. Fuel mixture according to claim 1, characterized in that, The mixture of coal powder and husk has a granulation of 50 to 80% <90 µm.

3.

Mixture of fuels according to claim 1 or 2, characterized in that,

The pretreated shell material (7) with a water content of 2 to 15%, an oil content of between 0 and 5% is used as the starting material for the mixture of powdered coal and scale material (10). and a grain size of up to a maximum of 50 mm.

Four.

Mixture of fuels according to one of claims 1 to 3, characterized in that,

in the mixture of powdered coal and husk (10), as solid carbon support (6), coal, a mixture of coal, coke or a mixture of coal and coke is contained.

5.

Mixture of fuels according to one of the preceding claims, characterized in that,

The mixture of powdered coal and husk (10) can be prepared by grinding coal, lignite, granulated coal, a mixture of coal or a mixture of coal and petroleum coke and the husk material (7) in a mill with an integrated sorter and can be pneumatically fed using a transport gas from pressure vessels (21) through shipping or feeding vessels (22, 23) and a distribution vessel (24) to the injection line (26) and to the blowing nozzles (27).

6.

Mixture of fuels according to one of the preceding claims, characterized in that,

The mixture of powdered coal and scale (10) prepared for injection contains scale material (7) with an iron content of 30 to 80%.

7.

Process for preparing and feeding a mixture of fuels according to one of the preceding claims in which at least one solid carbon support (6) and a scale material (7) is milled and classified in a mill (2) and fed in the form of a mixture of fuel and scale prepared for injection (10) through blow nozzles (27) to a blast furnace (28),

characterized because, a feed mixture (4) with a 3% scale ratio and an iron content in the scale material (7) of 30 to 80% is fed into the mill (2) and ground in a milling and drying process providing a mixture of coal powder and scale (10) that can be pneumatically transported with a granulation of 50 to 80% <90 µm.

8.

Method according to claim 7, characterized in that,

coal, a mixture of coal, coke or a mixture of coal and petroleum coke, as solid carbon support (6), is subjected to a grinding process together with the husk material (7) and the mixture of powdered coal and shell prepared for injection is injected (10) by means of a transport and distribution device (20 to 26) through a blow nozzle (27) to the blast furnaces (28).

9.

Method according to claim 7 or 8, characterized in that,

the solid carbon support (6) by means of a dosage (15) and the scale material (7) by means of a scale dosage (14) is fed to a premix device (5) in which the feed mixture is prepared ( 4) for the mill (2).

10.

Method according to one of claims 7 to 9, characterized in that,

The grinding is carried out in an inertized or air-operated mill (2) and an inert gas (9) or hot air is supplied for the grinding and drying process, which is heated in a hot air generator (11) to The necessary temperature.

eleven.

Method according to one of claims 7 to 10, characterized in that,

For the feed mixture (4), solid fuel material with a calorific value> 3000 kcal / kg, a humidity of approximately 15% and a grain size of a maximum of 80 mm and a pretreated shell material (7) are mixed. with a water content in the range of 2 to 15%, an oil content of between 0 and 5% and a grain size of at most 50 mm in the premix device (5) before the mill (2) .

12.

Method according to one of claims 7 to 11, characterized in that,

the feed mixture (4) is milled in a vertical roller mill (2) with integrated sorter (3) and after classification the mixture of powdered coal and injection-ready scale (10) with a scale ratio of 3 % and a granulation of 50 to 80% <90 µm is pneumatically transported using a transport gas or a mixture of gases from a pressurized gas container (21) to a transport line (25) and is fed by a system of continuous supply and a distribution device (24) and injection line (26) to the blowing nozzles (27). Figure 1