EP1337609A1

EP1337609A1 - Method and device for the preparation of fuels

Info

Publication number: EP1337609A1
Application number: EP01983536A
Authority: EP
Inventors: Bernhard SCHRÖDER; Martin Müller; Holger Wulfert; Walter Hartig; Horst Zewe
Original assignee: ERC Emissions-Reduzierungs-Concepte GmbH; Loesche GmbH
Current assignee: ERC Emissions-Reduzierungs-Concepte GmbH; Loesche GmbH
Priority date: 2000-10-11
Filing date: 2001-10-09
Publication date: 2003-08-27
Also published as: DE10050332A1; DE10050332C2; JP2004511654A; KR20030072333A; CN1479778A; RU2265644C2; CN1245489C; WO2002031091A1; AU2002215014A1; BR0114625A

Abstract

The invention relates to a method and device for the preparation of fuels by means of a catalyst solution. According to the invention, the costs of raw iron production may be reduced and in particular the consumption of coke reduced, by means of an increase in the directly-fed coal dust and application of low-grade coal or petroleum coke, whereby a catalyst is injected in the form of a solution, which reduces the ignition temperature of the fuel, during the coal milling of coarse coal to give fine coal or coal dust.

Description

Method and device for the preparation of fuels

The invention relates to a method for preparing fuels, in particular coal dust for the production of pig iron, according to the preamble of claim 1 and a device for carrying out the method according to the preamble of claim 11.

WO 99/64636 discloses a process for producing pig iron in a blast furnace, in which, according to the PCI (Powdered Coal Injection) process, coal dust as auxiliary fuel together with hot wind and / or oxygen is fed to the blast furnace by blow molding in order to reduce the consumption of coke decrease, thereby reducing the cost of production per ton of pig iron. To achieve a further reduction in coke consumption, coal dust prepared with a catalyst is used. Aqueous solutions of compounds of the sub-group elements zirconium, molybdenum, tungsten, manganese, iron, cobalt, nickel, copper, zinc or of aluminum, tin or lead, in particular a copper sulfate solution, are proposed as a catalyst additive. In addition to reduced coke consumption, the advantages of the coal dust provided with the catalyst additive are said to be the replacement by cheaper coal, less slag accumulation and reduced particle emissions as well as an improved quality of the pig iron. The aforementioned process is further described in the article "Blast furnace efficiency enhancer for pulverized coal injection" by the magazine "Steel Technology" February 2000, page 61 ff. The coal dust supplied for the partial replacement of coke via the blow molds has a particle size of 75 μm and a moisture content of <1%, and 350 to 600 ml of catalyst solution are fed in per ton of coal. The feed takes place with the aid of a separate device, which is arranged after a raw coal silo and before an MPS mill (FIG. 2), raw coal being prepared by spraying with the catalyst solution. Furthermore, it is described that the spraying device must meet special requirements due to the corrosive properties of the catalyst solution and that a cleaning system is also required for regular cleaning of the nozzles.

The invention has for its object to provide a method and an apparatus for preparing fuels, in particular coal dust for pig iron production, which in a particularly simple and efficient manner, both a saving of coke and an increase in the blowing coal and use of allow low-quality coal or petroleum coke (pet-coke).

In terms of the method, the object is achieved in that a catalyst is used which lowers the ignition temperature of the fuel or increases the rate of combustion at a constant temperature, and in that the catalyst, in particular as a catalyst solution, is applied to the coal particles during the grinding of the coal to fine coal. The coal particles or coal dust prepared in this way can be directly blown into the blow molds of the supplied to the furnace and together with the hot wind, which is heated to approx. 1250 C in a hot air heater, and / or with

Oxygen blow molding of a blast furnace or a silo

Interim storage can be supplied.

It has been found that a preparation with a catalyst, which is offered by the company ERC-Emissions-Reductions-Concepte GmbH under the product name carbamin 5010 and is disclosed in DE 198 00 873 C2, reduces the ignition temperature of fuels and accelerates them which leads to combustion. A reduced ignition temperature and an acceleration of the combustion within the blow molds mean faster ignition and faster burning of the residual coke, i.e. almost complete combustion of the coal within the blow molds. In addition to the oxygen partial pressure, the temperature of the blow molds (radiation component) and the fineness of grinding of the coal, as well as their inlet temperature and their moisture, these factors determine the efficiency of the coal dust injection and its effect on the consumption of coke and the quality and quantity of the pig iron produced.

The ignition temperature and the burning behavior are determined by the origin of the coal used. The so-called carburizing or maceral composition plays an important role in the blow molds. The volatile parts of the coal ensure the ignition of the residual coke as soon as it has reached the ignition temperature. However, the actual temperature increase of the coke within the blow molds does not take place via the combustion of the volatile components, but primarily via the radiant heat of the blow mold walls. The combustion of the remaining coke is kinetically inhibited, with the inertite part of the coal in particular delaying the combustion. Additives with a catalytic effect, ie catalysts that lower the ignition temperature of the residual coke, result in better combustion. The burn-up time of the coal is reduced, and because of the shorter burn-off time, the amount of coal injected can be increased, or less volatile coal or pet-coke can be used.

The catalytically active additive from ERC, hereinafter referred to as ERC additive, is described in DE 198 00 873 C2. It is used as an aqueous solution which contains cerium and iron salts of organic and / or inorganic acids and has a pH below 7 and can contain a wetting agent and / or a neutralizing agent. Reference is made to the compositions and concentrations of the catalyst solution and the fields of use indicated in the aforementioned patent specification.

Thereafter, the known catalyst solution for reducing the emission of pollutants during combustion and / or drying and / or thermal processes of carbon-containing fuels is provided and can be a solid fuel such as coal, wood, biomass, waste and heavy oil and other liquid fuels and / or supplied air are added before combustion. The pollutant-reducing effect is also listed with regard to the blow molds in the blast furnace process. It is not described how the preparation of the fuel is carried out.

A particular advantage of the method according to the invention is the possibility of operating the combustion of the prepared coal dust in the blow molds with a smaller excess of air, so that the formation of nitrogen oxides is suppressed. A particularly advantageous preparation of coal dust with a catalyst solution, in particular with the ERC additive, can be carried out in a roller mill in which raw coal or petroleum coke is subjected to a grinding and drying process, ground to coal dust and, with the aid of a fluid flow, in particular hot gas, a classifier above of the grinding chamber is fed.

The catalytic additive is expediently sprayed or sprayed as an aqueous solution at a temperature in the range from 5 to 35 ° C. into the grinding visible area, where

Temperatures below the boiling or decomposition temperature prevail.

In terms of the device, it was found that injection of the ERC additive in a mill, in particular in a roller mill, e.g. a LOESCHE airflow roller mill, which results in a particularly effective preparation of the comminuted fuel particles. It is assumed that the millbase fluid flow within a LOESCHE airflow roller mill in conjunction with a corresponding arrangement of the at least one spray device and alignment of the spray jets promotes the wetting and / or penetration of the coal or coke particles. The crushing process results in a significant increase in the surface area of the coal, so that there is a significantly higher occupancy density on reaction surfaces and also exposed pore spaces can be better wetted or infiltrated.

A particular advantage is that for the ERC additive known devices for water injection in Roller mills can be used. The devices can each be arranged above the grinding rollers and either between two adjacent grinding rollers, opposite one another or at an angle of approximately 120 °. The spray angle can be 10 to 70, preferably about 60 to 70, and approximately vertical or in

Be aligned in the direction of the grinding rollers or classifier. The arrangement of two devices in the mill housing is advantageous, wherein the spray direction and the spray angle can be the same or different.

In principle, the devices can be arranged with any conceivable spray angle anywhere in the grinding area and also in the viewing area of the mill. At least one device or nozzle should be arranged in such a way that the catalyst liquid can be metered in and the coal or coke ground material can be prepared even on the grinding bed, which builds up on the grinding plate or the grinding bowl. When the spraying devices are arranged at the level of a semolina cone, an injection direction tangential to the semolina cone should preferably be chosen in order to spray the fluid-solid particle clouds moving spirally toward the classifier. This can prevent the wetting of the grit cone wall by the catalyst and caking phenomena, in particular when the injection pressure is high, on the grit cone wall.

It is advisable to regulate the feed of the ERC additive depending on the coal to be ground, its feed quantity and the speed of the fluid. The ERC additive, which is stored in a tank, for example, is fed in via feed lines and a solution with the necessary lent concentration. The injection can be carried out with compressed air, a pressure of about 2 to 10 bar being appropriate.

In addition to the advantages in terms of lower coke consumption by substituting the more expensive coke or more expensive coal with cheaper coal or petroleum coke, and the cost reduction in the production of pig iron which is thereby achieved, a reduced dust emission and an improved quality of the pig iron are achieved. It becomes possible to reduce the combustion air or oxygen, which reduces the formation of nitrogen oxides. Cheaper and more expensive coal differ in particular in their proportion of volatiles and their proportion of ash. Cheaper coal has a lower percentage of volatiles, usually less than 25 to 30%, and an increased ash percentage, usually more than 7 to 8%. Reduced dust emissions, i.e. a reduction in the emission of unburned soot leads to a reduction in energy losses and less expenditure in the washing process of the gases of the blast furnace, since the soot removal requires considerable energy and technical effort. The reduction in soot emissions is an expression of the quality of the burnout of the amount of coal blown in and thus the effectiveness of the catalyst used.

The invention is explained below with reference to a drawing; in this show in a highly schematic representation

1 shows a partial longitudinal section through an airflow roller mill with a spray device.

Figure 2 is a highly schematic representation of an airflow roller mill with two spray devices. 3 to 5 a cross section through airflow roller mills with four, three and two grinding rollers and two spray devices each.

An air flow roller mill 2 is shown in detail in FIG. 1. On a grinding table 3, grinding rollers 4 roll, of which only one is shown. A blade ring 5 is arranged on the circumference of the grinding plate 3, via which hot gas 13 flows into the grinding and classifying chamber 12 with a swirl flow predetermined by the blade tendency and feeds ground material comminuted by the grinding rollers 4 into a classifier 7 in a material flow 6. Material that has not yet been comminuted sufficiently falls back through a semolina cone 8 onto the grinding plate 3 and is subjected to further comminution. The fine material 9 comes out of the classifier 7 via a fine material discharge (not shown) and is supplied to blow molding (not shown) a shaft furnace (not shown) or a silo as an intermediate store (not shown).

The carbon particles of the ascending mill fluid flow are prepared with devices 10 which are designed for spraying or spraying a catalyst solution to improve combustion, in particular an ERC additive, into the grinding visible space 12. These devices 10 can be arranged above the grinding rollers 4 and / or at the level of the grinding rollers 4, in particular a little above the grinding table 3 or the grinding plate edge, in particular attached to the mill housing 11. At least one of the spray devices 10 should face the grinding table 3 and should prepare the grinding bed building on the grinding table 3. The catalyst solution can be supplied via a common feed line 18. The devices 10 essentially correspond to spray devices for water, which are usually provided in LOESCHE airflow roller mills for reducing the temperature of the ground material or for safety reasons. These known water spray devices can advantageously be used to inject the ERC additive.

The temperature of the ERC additive injected via the device 10 is less than 95 ° C. The injection is carried out with compressed air 14, which is fed to the device 10 at a pressure of 2 to 10 bar. The spray angle of the above and essentially horizontally oriented spray devices 10 is advantageously between 60 and 70 degrees, while the spray angle of the lower spray devices 10 depends on the angle of inclination of the spray jet.

An arrangement of the spray devices 10 at the level of the lower region of the semolina cone 8 is particularly advantageous, since an efficient preparation of the regrind particles of the ascending regrind fluid flow 6 is achieved. In Fig. 1, a spray device 10 is also arranged at the level of the grinding rollers 4. This device is provided in particular for the preparation of the ground material building up on the grinding plate 3 and the ground material particles thrown over the edge of the grinding plate 3. In addition, the hot gas 13 absorbs the sprayed catalyst solution, so that the regrind particles in the upward regrind fluid flow 6 can be wetted or infiltrated.

Fig. 2 shows a highly schematic representation of an airflow mill 2, which is equipped above the grinding rollers 4, of which only one grinding roller 4 is shown, with two spray devices 10. The spray devices 10 are fastened in the mill housing 11 and connected to a pump unit (not shown) via feed lines 15. The ERC additive is stored in a tank (not shown) and is diluted with water in a predetermined ratio in front of the pump set. Shut-off devices 16 and solenoid control valves 17 allow metering depending on the amount of coal fed in and the speed of the hot gas.

In addition, a spray device 10 is arranged just above the grinding table (not shown) and the nozzles are aligned such that the grinding bed is wetted with the catalyst liquid.

Fig. 3 shows a cross section through a roller mill 2 with four grinding rollers 4 and two spray devices 10. The spray devices 10 are each arranged almost centrally between two grinding rollers 4 and opposite each other and aligned such that an angle bisector of the spray angle α (see Fig. 1 and 2) forms a 'secant and, as a result, the carbon particles of the regrind fluid flow are prepared in the spaces between two grinding rollers 4 and in the mill center.

The spray devices 10 can expediently also be arranged such that there is a tangential orientation of the spray angle. In this way, neither areas of the grinding rollers nor the housing of the semolina cone (not shown) are wetted, or there is only very little wetting, so that no caking phenomena occur. The tangentially oriented spray devices 10 are shown in broken lines. These tangentially oriented spray devices can be arranged in addition to the approximately radially arranged spray devices 10 or alternatively to these and at different heights. 4 shows an airflow roller mill 2 with three grinding rollers 4 and two spray devices 10. The spray devices 10 are arranged off-center in two of the three spaces between the grinding rollers 4 and spray the ERC additive into the spaces and approximately parallel to an inside end face of one of the two adjacent grinding rollers 4 towards the mill center.

The roller mill 2 according to FIG. 5 has two grinding rollers 4 and two spray devices 10. These are opposite one another, but positioned off-center between the two grinding rollers 4. In addition or as an alternative to the spray devices 10 of FIGS. 4 and 5, the tangentially oriented spray devices 10 shown in dashed lines in FIG. 3 can be provided.

The ERC additive can be supplied by the spray devices 10 in a ratio of 0.2 to 1 liter per ton of coal, with a dilution of about 1:10 taking place. The

Injection is carried out with compressed air of approximately 2 to 10 bar. The o spray angle α can be 10 to 70, preferably 60 to 70.

The prepared coal dust is fed through the blow molds of a blast furnace at a speed of around 200 m / s. It was found that the residual fire time after the coal was injected was 4 to 5 microseconds and the concentration of the ERC additive was approximately 30 to 50 ppm.

Claims

1. Process for the preparation of fuels with a catalyst, in particular coal dust, which is burned in blow molds during the production of pig iron in a blast furnace, characterized in that a catalyst which lowers the ignition temperature or increases the rate of combustion of the fuel at a constant temperature, during the coal grinding of raw coal to fine coal or coal dust is supplied to the coal particles, in particular is applied to the coal particles.

2. The method according to claim 1, characterized in that an ERC additive suitable for reducing the emission of pollutants during combustion and / or drying and / or thermal processes of carbon-containing material is used as the catalyst.

3. The method according to claim 2, characterized in that the ERC additive as a solution, which contains cerium and iron as salts of inorganic and / or organic acids in an aqueous solution with a pH <7, in the grinding visible space (12 ) is sprayed.

4. The method according to claim 2 or 3, characterized in that the raw coal in a roller mill (2) with grinding rollers (4) rolling on a grinding plate (3) and the ERC additive above the grinding plate (3) and / or the grinding rollers (4) is supplied.

5. The method according to any one of claims 2 to 4, characterized in that the raw coal in an airflow roller mill (2) with an integrated classifier (7) and a grinding classifying chamber (12) is subjected to a grinding-drying process and the ERC -Additive with a temperature below o 100 C is fed into the grinding visible space (12).

6. The method according to claim 5, characterized in that the ERC additive is supplied to the grinding visible space (12) with a spray angle α of approximately 10 to 70.

7. The method according to claim 5 or 6, characterized in that the ERC additive is sprayed horizontally and tangentially to a lower region of a semolina cone (8) into the grinding visible space (12).

8. The method according to any one of claims 2 to 7, characterized in that the supply of the ERC additive is regulated in dependence on the raw coal supplied and the fluid velocity.

9. The method according to any one of claims 2 to 8, characterized in that the ERC additive is injected with compressed air into the grinding classifying chamber (12) and the compressed air is supplied at a pressure of 2 to 10 bar.

10. The method according to any one of claims 2 to 9, characterized in that the ERC additive is added in a ratio of 0.2 to 1 liter per ton of coal and a dilution of about 1:10 takes place.

11. Device for preparing fuel with a catalyst, in particular coal dust for pig iron production and for carrying out the method according to one of claims 1 to 10, characterized in that a roller mill for grinding raw coal or coke in fine coal or coal dust, in particular an air stream - Rolling mill (2), with grinding rollers (4) rolling on a grinding plate (3) and an integrated classifier (7), a mill housing (11), a grinding and classifying chamber (12) and a feed for raw coal as well as a fine material discharge for fine coal or Coal dust (9) is provided and at least one device (10) is arranged in the grinding classifying chamber (12), by means of which the catalyst can be fed to the carbon particles during the grinding and classifying process in order to lower the ignition temperature or to increase the rate of combustion at the same temperature and in particular can be applied to the carbon particles.

12. The device according to claim 11, characterized in that the devices are designed as spray devices (10) and are arranged above the grinding table (3) and / or the grinding rollers (4).

13. The device according to 11 or 12, characterized in that devices are used as spraying devices (10) which are provided for water injection into the grinding visible space (12).

14. Device according to one of claims 11 to 13, characterized in that the spray devices (10) have a spray angle o α in the range from approximately 10 to 70.

15. Device according to one of claims 11 to 14, characterized in that two spray devices (10) are provided and, viewed in plan view, are each arranged between two grinding rollers (4).

16. The apparatus according to claim 15, characterized in that the spray devices (10) are arranged in the center or off-center between two adjacent grinding rollers (4).

17. The device according to one of claims 11 to 16, characterized in that the catalyst as a solution to the spray devices (10) with the aid of a pump unit can be supplied and injected and sprayed with compressed air of 7 to 10 bar.

18. Device according to one of claims 11 to 17, characterized in that the spray devices (10) are arranged horizontally and are oriented in the direction of the spaces between the grinding rollers (4) and mill center in such a way that, based on a cross section of the roller mill (2), a bisector of the spray angle α forms a secant.

19. Device according to one of claims 11 to 18, characterized in that at least one spray device is directed in the direction of the grinding table (3) and onto the grinding bed which is being built up.

20. Device according to one of claims 11 to 18, characterized in that the spray devices (10) are aligned tangentially to a semolina cone (8).