GB2214521A - Method of producing ferrosilicon in an electrical power generating plant furnace - Google Patents

Description

1 I.

r 2 1 j r-, r) 'I df- ' ú- "METHOD OF PRODUCING FERROSILICON IN A POWER PLANT FURNACE" This invention relates both to power generation and ferrous metallurgy, and more particularly to a method of producing ferrosilicon in a power plant furnace.

The invention provides for obtaining silicon from furnaces of power plant in addition to power generation, rendering generation of electric power a low-waste process.

It is generally known that the quality of solid fossil fuel produced annually throughout the world has been steadily declining. This is caused, first and foremost, by the rising share of low-calorie fuel produced by strip mining. Furthermore, mechanised excavation of thin seams of coal in underground mines. and also the scooping of much and rock interlayers in the process of excavation in open-cast coal mines results in the produced coal having a high content of various foreign matter. Consequently. the ash content of the coal grows, whereas the calorific value of fuel per unit of weight falls.

The incombustible mineral part of solid fuel. of which the chemical content includes up to 50% by weight of silicon oxides, up to 27% by weight of aluminium oxides and 10 to 20% by weight of iron oxides is 1 2 completely turned into ashes and cinders when burnt in power plant furnaces. Therefore, the weight of ash and cinder waste of steam power plants grows.

The waste is accumulated in ash and cinder disposal areas where it gradually dries up and becomes compacted. In this form the waste of steam power plants is only scarcely utilized. mostly for building up land profiles for recultivation or land-planning purposes. road-building and construction. To an even lesser degree an ash-cinders mixture (ACM) is used as the initial stock for production of construction materials, such as cement, binders and aggregates for concrete, gravel and rubble.

Broad utilization of ACM is hindered by its relatively high content of iron oxides which can be as high as 22% by weight. It is mainly for this reason that the strength of artificial gravel and crushed stone produced from ACM is inferior to that of similar natural materials. the more so because of the more ferric and ferrous compounds it contains. Articles made of concrete with the use of binders including products of ACM processing lose their initial appearance within relatively short periods. mostly on account of rusty stains developing on the surface of building structures in a moist environment.

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v 3 The use of ACM in agriculture as a micro-element fertilizer is curbed by its containing heavy metals (lead. zinc and others) capable of being transferred into foodstuffs, to threaten the health of human beings.

Another trend in utilization of the bulk of ash and cinder waste is extraction from the cinders of drops of a metallic alloy (ferrosilicon) with a silicon content of 12-25% by weight. The world's demand for lowsilicon ferrosilicon has been growing. resulting from the rising volumes of foundry operations with processed initial materials, and from broad introduction of BOF (basic oxygen furnace) technologies in iron and steel metallurgy.

As a reducing or deoxidizing agent, ferrosilicon is a valuable initial material in ferrous metallurgy and foundry technologies.

The known power plant furnaces are designed both to combine production of ferrosilicon with steam output for power generating purposes. Although definite pre-requisites for this process are inherent in the existing furnaces. they are not, however. derived from power plant furnaces to a degree providing for production of ferrosilicon.

There is known a process of producing ferrosilicon in furnaces of the shaft type. e.g. in blast furnaces (R. Durrer, G. Volkert, 11Metallurgiya FerrosplavovII, 1976, Metallurgiya/Moscow/). The refractory-lined 4 inner chamber of a blast furnace is formed of three cylindrical portions and two tapering ones. The upper cylindrical portion - the furnace top - is used for loading the charge into the shaft furnace. It merges with the tapering portion claiming the main volume of the furnace its shaft accommodating most of the charge advancing into the lower higher temperature regions. The base of this tapering portion merges with the central cylindrical portion for smooth transition of the charge into the second tapering portion of the opposite taper - the bosh supported by the lower cylindrical portion - the hearth with a refractory- lined bottom. The hearth accumulates the fluid products of smelting; slags at the top and ferrosilicon at the bottom.

correspondingly, the upper part of the hearth accommodates a slag escape outlet and the lower part accommodates a ferrosilicon escape outlet. The periphery of the top part of the hearth accommodates tuyeres with burners for feeding air. gaseous fuel or pulverized or liquid fuel into the furnace.

Ferrosilicon is produced in a shaft furnace by smelting minerals with a high silica content with iron or its oxides in the presence of a carbon-containing reducing agent.

The process includes loading into the furnace through the furnace top a charge containing quartz.

quartzite or other minerals with a silica content of at c 6 least 96%. rust-free iron shavings and solid carboncontaining reducing agent coke fines. once charged. the furnace is heated by feeding a combustible mixture of fuel oil, fuel gas or pulverized coal with air through the burners. With the charge heated to 13500. iron and silicon are reduced from their oxides in the presence of the reducing agent - coke fines yielding ferrosilicon, the reduction process also yielding carbon monoxide as a gas leaving the furnace through the furnace top. The higher the temperature, the greater is the silicon content in the ferrosilicon obtained. Ferrosilicon and slags flow down, forming a bath where the slags float on the ferrosilicon surface. When the slag level has risen above the slag escape outlet, it is opened to tap the slag. whereafter the silicon is run out through the bottom escape outlet of the bath. Afterwards the tap holes are plugged with refractory clay, and a new smelting cycle is commenced.

However. the above described process yields low-silicon ferrosilicon even when initial materials or ores with a high silica content is used for its production.

The process is further characterized by increased percentage of metal scrap in the charge - as high as 45% by weight, and considerable input of the specifically processed carbon-containing material - coke fines, while only some 30% by weight of silicon is reduced from the charge. whereas the rest of silica goes into slag.

4 k 6 The process yields an increased mass of solid waste, to say nothing about this technology of producing ferrosilicon in a furnace not being associated with generation of electricity.

There is known a method of producing ferrosilicon in a power plant furnace (SU, A, 815060), where the fuel used for firing the furnace is carbon-containining matter of which the cinders contain iron oxide in an amount of 10-22% by weight.

The power plant furnace is defined by four verticle walls, its bottom the hearth - being formed by two inclined walls incorporating sectioned bundles or banks of water-cooled tubes. The vertical walls at the opposite longitudinal sides of the furnace have paired openings therethrough for accommodating the burners.

The internal surface of the longitudinal walls of the furnace in the area of the arrangement of the burners and below them is refractory-lined, the same as the inclined surfaces of the hearth. The inclination of hearth sections is selected to guide the contents towards the hearth runouts the escapes intended for delivering the cinders from the furnace into the underlying water-filled baths - the granulators. The granulators are equipped with conveyor facilities for guiding granulated cinders into the hydraulic ash/cinders removal duct, to carry them into the pipeline leading to the ash/cinders disposal area.

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The top part of the furnace accommodates a tubular steam generator associated with a steam turbine and its electric generator. The path of the furnace gases includes heat-exchange apparatus, electrostatic precipitation filters and a flue providing the required draught for the furnace.

Most of the burners of the furnace are rated for the supply of pulverized coal with the excess-air (oxygen) coefficient of 1.10 to 1.19. Either one or two burners are fired with a hydrocarbon fuel, e.g. fuel oil for maintaining the temperature above the firing point of the solid fuel. Fuel-oil burners are all the more necessary when low-grade solid fuel is used, with its low content of organic matter and volatile hydrocarbons.

According to the last described known method, the carbon-containing fossil fuel is fed in a mixture with air into the furnace, and with the internal space of the furnace being maintained at a 1500-ISSOOC temperature.

the fuel burns with an air (oxygen) excess coefficient of 1.10-1.19, yielding hot furnace gases. The gases transfer their heat to the heat-exchange surfaces of the steam generator, for the water in its tubes to turn into steam fed into the steam turbine to rotate the shaft of the electric generator supplying electric power.

With coal particles burning in the combustion space of the furnace. appropriate conditions are created therein for the reaction of reduction of metals from the respective oxides (the mineral part of the fuel), 8 i.e. iron. Silicon. aluminium, calcium and other oxides. These conditions embrace the high (1500-1550OC) temperature of the gaseous medium in the combustion space of the furnace. the availability of solid (carbon) and gaseous (carbon monoxide) reducing agents, and sufficient time for the course of the reaction of reduction and for separation of the reaction products. Microscopic particles of the reduced metal, mainly iron, and of ferrosilicon with a low silicon content (to be referred to as low-silicon ferrosilicon) are formed in the burnt particles of coal. i.e. in the ashes and cinders settling on the walls and hearth of the combustion chamber.

However. the time of residence of coal particles in the high-temperature environment of the hot furnace gases has been found to be insufficient for adequately complete reduction of the entire mass of iron and silicon oxides and for fusion of the droplets of the reduced metals into their alloy - low-silicon ferrosilicon.

Thus, small-size inclusions of iron and its alloys with silicon. present in the particles of cinders, cannot be considered a marketable product for metallurgical uses.

The greater part (80-85% by weight) of the burnt fuel is carried away from the combustion space of the furnace by furnace gases. In their path of gradually cooling down in the heatexchange apparatus, passing 4 9 through the precipitation filters and escaping via the flue. the gases have the ash particles they carry separated in the electrostatic precipitators and washed down into the hydraulic ash/cinders removal duct, wherefrom the ash/cinders slurry is directed via a pipeline to the disposal area.

The smaller part (15-20% by weight) of the incombustible component of the fuel is deposited on the walls and hearth surfaces of the furnace as cinders.

The cinders flow at a relatively slow rate, determined by their viscosity at a given temperature towards the bottom part of the furnace space, to the escape outlet. As the cinders are thus moving. processes similar to those described above take place in their midst.

However, more stable temperature conditions owing to the higher heat capacity of cinders and their longer stay under these conditions promote a fuller course of reactions of reduction of iron and silicon oxides in the cinders than in the ashes. The cinders yield an alloy of low-silicon ferrosilicon in the form of individual drops 4-5 mm in diameter. The granulation of the molten mass takes place at high cooling rates, so that some of the drops of ferrosilicon become exposed and segregated from the cinders as such. This means that granules of ferrosilicon can be extracted from the slurry and separated from the solidified mass of cinders, by incorporating in the hydraulic ash/cinders removal system a section with a hydro-operated trap performing recovery of ferrosilicon granules.

The above described process provides for combining within one and the same furnace the generation of energy for producing electric power with partial processing of the solid waste of the fuel burnt in the furnace into marketable products. i.e. low-silicon ferrosilicon and initial stock for production of construction materials.

As the process of reduction of ferrosilicon from the metal oxides takes place at the temperature of molten cinders withdrawal at which the cinders normally flow down the walls and hearth of the furnace towards the escape outlet. not exceeding 1400-15000C, the viscosity 15 of the cinders remains comparatively high (from about 8 Pa.s to about 20 Pa.s, and under such conditions the mass exchange in the molten cinders is impaired. Ultimately, the drops recoverable in the hydro-operated traps gather ferrosilicon particles amounting to only 20 2. 5-20.0% by weight of the total iron oxides. or 0.52.0% by weight of the cinders. Furthermore. the above described process provides for obtaining ferrosilicon from only that part of the solid waste of the fuel which is turned into cinders. and this part amounts to only 15-20% by weight of the incombustible component of the solid fuel, i.e. to 4.5-6.0% by weight of the coal feed. The ash component -I 11 1 of the solid waste of steam power plants and fuel-oil cinders take no part in the process of reduction of ferrosilicon and recovery of initial stock for construction materials. 5 It is the main object of the present invention to create a method of producing ferrosilicon in a power plant furnace, which should provide for stepping up the yield of ferrosilicon. It is another object of the present invention to create a method of producing ferrosilicon in a power plant furnace, which supports at the same time a low-waste technology of generation of electric power.

With these objects in view, the present invehtion resides in a method of producing ferrosilicon in a power plant furnace using for its fuel carbon-containing matter of which the cinders contain iron oxides in a quantity of 10-22% by weight, including the operations of forming in the power plant furnace a bath of molten cinders and directing on its surface a jet of a hydrocarbon fuel to heat the bath to a temperature of 170018000C, directing together with the hydrocarbon fuel onto said bath the fine- particle products of combustion of carbon-containing matter, and recovering ferrosilicon from the cinders yielded by the combustion progress.

12 The feed of the hydrocarbon fuel jet helps to support isothermal conditions for the reaction of reduction. For this purpose. in accordance with the invention. the jet of the hydrocarbon fuel is directed onto the surface of the cinders bath specifically created in the hearth part of the power plant furnace. to ensure that the bath is heated to 1700-18000C.

With the cinders bath formed in the power plant furnace, favourable conditions are created for overheating of the molten cinders by 200 25011C in comparison with conventional temperatures of molten cinders withdrawal. This is made possible by the supply of additional heat released by combustion of the hydrocarbon fuel.

Moreover, the formation of the cinders bath creates favourable thermodynamic conditions for reduction of iron oxides by carbon. namely. the more stable and higher temperature of the environment provided by the molten cinders containing both metal oxides and a carbon-containing reducing agent offers a greater reaction surface for the reduction process. Thus, the reaction of reduction encompasses a greater proportion of oxides of iron and other metals than is possible in the process of the prior art.

On the other hand. the lower viscosity of the environment wherein the reaction of reduction takes place promotes more intense mass exchange, which means that gaseous products of the reaction are more intensely 1 released to rise onto the surface of the melt, whereas heavier droplets of the metal reduced from its oxide are carried down by gravity, to accumulate on the furnace bottom. Owing to a substantial density differential of the cinders as such and the metal, the latter forms on the bottom of the furnace a Si and Fe alloy, which allows conduct of a technology with separate delivery of the cinders and of the metallic alloy, e.g. ferrosilicon.

With the fine-particle products of combustion of the carbon-containing matter being directed to the cinders bath together with the hydrocarbon fuel, conditions are created for engaging in the reduction process the most actively reduceable oxides, and thus for ensuring an even higher yield of ferro-alloys.

It is expedient that the fine-particle products of combustion of carboncontaining matter should be the products of combustion of the carboncontaining matter forming in the power plant furnace itself.

This would support an even lower-waste technology of generation of electric power.

Thus, the herein disclosed method of producing ferrosilicon in a power plant furnace provides for generating heat and/or electric energy and producing ferrosilicon at the same time and within one and the same plant.

Owing to the rationalized combination of the two processes, a product which is actually novel for powergenerating installations is obtained, its production 14 utilizing the energy otherwise wasted on the fusion of the incombustible part of fuel coal, turning it into cinders. The combined process requires only a small additional input of heat, sufficient for overheating the cinders by 200-2500C to enhance mass exchange in the reaction of reduction of metals from the oxides contained in the cinders.

With the additional ashes included in the jet of the hydrocarbon fuel, it becomes possible, on the one hand, to directionally influence the yield of ferrosilicon, and on the other hand, to reduce still further the final mass of solid waste.

owing to the above discussed considerations, the disclosed method provides for implementing a low-waste technology of generation of heat and/or electric power, with utilization of the heat of the cinders melt and of a part of the bulk of the solid waste of the fuel feed at steam turbine electric stations for production of ferro-alloys, and the initial stock for manufacture of constructional materials.

The disclosed method can be performed in any known power plant furnace which uses for its fuel carbon-containing matter of which the cinders contain iron (oxide in a quantity of 10-22% by weight). Thus, the furnace may be defined by four vertical walls, with its bottom of two inclined walls incorporating bundles of water-cooled tubes in the form of sections lined on the inside with refractory materials. The front and 4 is rear vertical walls of the furnace have through openings, accommodating the burners, the burners being arranged in opposing pairs. It is a common practice to equip a power plant furnace with eight to twelve burners of which either one or two burners are fired with a hydrocarbon fuel, e.g. fuel oil or natural fuel gas and the rest of the burners are fired with a pulverized carbon-containining solid fuel. e.g. coal. peat. oil. shale and so forth.

In an apparatus capable of performing the disclosed method the burners fired with the hydrocarbon fuel are directed towards the bottom of the furnace. Furthermore, they are associated with a system for supplying pulverulent carbon-containing matter jointly with the hydrocarbon fuel.

The bottom part of the hearth of the furnace accommodates outlets for escape of the cinders, with the inclination of the hearth sections of the furnace guiding the cinders melt towards these outlets. An enclosure made of a refractory material surrounds these escape outlets, so that it defines a molten cinders bath jointly with some of the hearth sections in the operation of the power-plant furnace. The hearth of the furnace further accommodates another escape outlet for ferrosilicon. Directly underlying the cinders escape outlets are granulation baths accommodating conveyers for delivering cooled granulated cinders to the ash/ 16 cinders hydraulic removal duct associated with a pumping station having its pumps connected to the pipeline leading to the ashes and cinders disposal area of the steam electric station.

The fuel combustion function of the power plant furnace is controlled by regulating the feed rate of fuel supplied through the burners and the feed rate of the oxidizing agent, of which the ratio defines the air (oxygen) excess ratio which is generally slightly above the 1.0 value.

The combustion of the carbon-containing fuel releases heat which heats the heat exchange surfaces of the water tubes, producing there superheated stream which is fed to a steam turbine to rotate the rotor shaft of an electric generator producing electric power.

The process of combustion inside the furnace yields not only heat, but also solid particles of unburnt fuel, ashes carried away by the furnace gases, and cinders - these materials amounting to the waste of the process of generation of electricity.

The cinders deposited on the walls of the furnace flow down these walls into the molten cinders bath in the hearth part of the power plant furnace, the cinders temperature being close to the value associated with conventional molten cinders withdrawal for a given grade of fuel.

-1 -4 17 By directing onto the surface of the cinders bath the torch of a burner supplied with a hydrocarbon fuel, e.g. fuel oil, of which the heat value is higher than that of a pulverulent carbon-containing fuel (e.g. coal.

peat, oil, shale), the molten cinders in the bath are -heated to a 1700-18000C temperature.

The overheating of the cinders bath to 1700-18000C enhances the yield of reduced iron and silicon.

The following data have been experimentally obtained and appear in Table 1.

Table 1

Temperature Quantity of reduc- No of molten ed ferrosilicon, % cinders, OC -of weight of cin- ders Content of Oerros-licon, % of of silicon aluminium 1 1550 o.6 8-12 2 1610 1.85 10-14 traces 3 1650 2.4 10-17 0.56 4 1700 6.a 18-25 0.67 1720 7.4 22-28 1.11 6 1760 8.3 24-32 1.86 7 1800 10.1 34-40 1.96 8 1810 6.1 17-22 4.7 9 1840 3.7 14-17 9.63 It can be seen from the data in Table 1 that overheating the cinders bath to a temperature between 17000C and 18000C is preferred.

18 With the bath of molten cinders heated to a temperature below 17000C. the yield by weight of reduced ferrosilicon is at the level of the known process considered as the prior art of the present invention.

overheating of the cinders bath to a temperature above 18000C is illadvised. as it is accompanied by a dropping yield of ferrosilicon on account of silicon monoxide formation. with a simultaneous growth of the weight of aluminium reduced from its oxide. However, the presence of aluminium in deoxidizing additives is ill-advisable, its limits being definitely prescribed by the corresponding standards of metallurgy.Besides the higher temperatures accelerate the process of deterioration of the refractory lining of the molten cinders bath.

Thus, it can be regarded as an optimized duty of the process of reduction of iron and silicon from their oxides to maintain a temperature of 178018000C with the yield of ferrosilicon about 10.0% by weight and the maximum content of silicon in the alloy at 34-40% by weight.

At a 1700-18000C temperature the cinders melt reduces its viscosity from 4-6 Pa.s to 1-2 Pa.s. In this environment of lower hydraulic resistance the rate of mass exchange at the surface of particles of the solid reducing agent (coal) grows due to the transport of droplets of reduced metals - iron and silicon - 1 19 towards the bottom of the cinders bath and of bubbles of carbon monoxide rising to the surface of the bath. The gases emerging at the surface of molten cinders are carried away by the hot furnace gases.

Furthermore, with the lower viscosity of the melt.

the gravity forces induce its separation into layers, with the bottommost layer being the one of heavier metals and the overlying layer being the one of more lightweight cinders. In operation of a power plant furnace the process of downward transport of metals and upward transport of cinders deprived of the heavier metals goes on continuously.

Thus. the raising of the temperature of the bath of molten cinders to 1700-18000C increases the percentage of the metal reduced from the cinders and enhances its quality owing to more favourable thermodynamic conditions created for the reaction of reduction.

Jointly with the hydrocarbon fuel, there are directed onto the surface of the molten cinders bath fine-particle products of combustion of carboncontaining matter, formed in the main space of the power plant furnace.

With pulverulent products of combustion of carboncontaining matter. e.g. pulverized coal or pulverulent ashes, being directed onto the surface of the bath of molten cinders together with the hydrocarbon fuel, the mass of the solid waste of the thermal power plant engaged in the processing grows, and, correspondingly, the yield of ferrosilicon and of the initial stock for construction materials, free from oxides, also grows.

However, it is possible to direct onto the surface of the bath of molten cinders as the fine-particle products of combustion of carbon-containing matter not only the products of combustion taking place in the power plant furnace itself, but also pulverulent products of combustion of carbon-containing matter of any kind, obtained elsewhere.

If the fine-particle products of combustion of carbon-containing matter were applied onto the surface of the cinders bath by mere spreading, this would reduce the temperature of the upper layer of the cinders by screening out the heat transfer to the cinders by radiation. To avoid this, the fine- particle products of combustion of carbon-containing matter are directed onto the bath surface in the jet of the hydro-carbon fuel, the high temperature of its torch heating up this pulverulent additive, enhancing the balance of heat transfer to the surface of the cinders bath.

As more and more ferrosilicon is produced, the thickness of its bottommost layer in the bath of molten cinders grows. Thus, the accumulated ferrosilicon is periodically let out through the bottom escape outlet, the periods depending on the volume of the cinders bath h S 21 and on the type of power plant furnace. Short of discharging the entire volume of accumulated ferrosilicon, the outlet is plugged once again. to allow for accumulation until the next discharging operation.

The bath of molten cinders is continuously replenished by molten cinders flowing down the walls of the furnace. with the lightweight upper layer overflowing the enclosure of the bath and flowing towards the cinders outlet to enter the granulation bath and to be further delivered to the hydro-operated trap, and then into the bin for the initial stock for manufacture of construction materials. For the nature and advantages of the present invention to be even better understood. given below are examples of performance of the disclosed method of producing ferrosilicon in a power plant furnace. Example 1 Coal with the following content of oxides in its cinders, % by weight: silicon oxides 49.2, aluminium 20 oxides 25.4 and iron oxides 15.4, is fed into a power plant furnace in a mixture with air, with a 1.1-1.19 air excess coefficient. The coal-air mixture is combusted at 1500-15500C. A part of the coal mass with the ash content of 20% by weight is deposited onto the walls of the furnace below the burners and flows down in the molten state upon the bottom of the furnace where molten cinders accumulate and form a cinders bath. A jet of 22 fuel oil is directed onto the surface of the molten cinders, raisingthe melt temperature to 16500C. After 16 hours of accumulation of ferrosilicon, it is discharged through the bottom outlet.

The quantity of ferrosilicon is 2.4% by weight of the total cinders, with the silicon content in the alloy varying between 10 and 17% by weight. The content of aluminium is below 0.6% by weight.

Example 2

The same grade of coal is combusted under conditions similar to those of Example 1. By directing onto the surface of the bath of molten cinders a jet of fuel oil.

the metal bath temperature is raised to 17000C. i.e. the bath is overheated by 100-1500C above the conventional temperature of removal of molten cinders.

The process yields 6.8% by weight of ferrosilicon with a 18-25% by weight silicon content in the alloy, which is higher than the yield of Example 1.

Example 3

The same grade of coal is combusted under conditions similar to those of Example 1, but with the temperature of the molten cinders bath raised to 1BOO0C.

The discharge of ferrosilicon accumulated in the furnace shows that its yield is 10.1% by weight. with 34-40% by weight of silicon and a 1.96% by weight content of aluminium.

h 23 Example 4

With the same grade of coal combusted and the same conditions maintained, the temperature of the bath of molten cinders is raised to 18400C. and the yield of ferrosilicon drops to 3.7% by weight. The silicon content in the alloy is 14 - 17% by weight. but the content of reduced aluminium grows to 9.6% by weight.

Example 5 Coal of which the cinders contain 56.4% by weight silicon oxides. 22.5% by weight aluminium oxides and 11.0% by weight iron oxides is burnt in a power plant furnace, in a pulverized coal-air mixture with a 1.10-1.19 air excess coefficient fed into the furnace. With the bath of molten cinders having formed on the hearth of the fiirnace, a burner directed at the surface of the molten cinders bath is activated. its jet containing a mixture of air, fuel oil and pulverulent products of combustion of the carbon-containing' fuel to maintain the temperature of the melt at 17000C. In this jet the content of the pulverulent products of combustion of the carbon- containing fuel amounts to 0.1% by weight of the ashes and cinders formed by combustion of this grade of coal in the power plant furnace itself.

The yield of reduced ferrosilicon is 10% by weight of the total cinders, with the alloy containing about 30% by weight silicon and less than 1.0% by weight aluminium.

24 It can be seen from the above examples that the optimum temperature of the heating of the bath of molten cinders is in the 1700-18000C range, which supports the maximum yield of ferrosilicon even with the highest possible content of aluminium oxides in the cinders.

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Claims (3)

1. CLAIMS,

   A method of producing ferrosilicon in a power plant furnace, using for its fuel carbon-containing matter of which the cinders contain iron oxides in a quantity of 10-22% by weight. including the operations of forming in the power plant furnace a bath of molten cinders and directing onto its surface a jet of a hydrocarbon fuel to heat said bath to a temperature of 1700-18000C. directing together with said hydrocarbon fuel onto said bath the fine-particle products of combustion of carbon-containing matter, and recovering ferrosilicon from the cinders yielded by the combustion process.
2. 2. A method as claimed in Claim 1, wherein the fine-particle products of combustion of carboncontaining matter are the products of combustion of the carbon-containing matter, forming in the power plant furnace itself.
3. 3. A method of producing ferrosilicon a power plant furnace, substantially as hereinbefore described and illustrated by the cited examples of its performance.

   Published 1989 at The Patent Office, State House, 66171 High Holborn, LondonWClR4TP. Purther copies maybe obtained from The Patent Office Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1/87