FI116571B - Process for melting inert material - Google Patents

Description

116571

METHOD FOR Melting Inert Material

The invention relates to a process for melting inert material in a metallurgical temperature reactor, such as a flame smelting furnace, according to the independent claim.

Waste and by-products from the metallurgical industry are typically difficult to handle. Examples include hydrometallurgical precipitates from zinc factories such as jarosite and dust and flakes from the steel industry. The above materials are generally non-combustible chemically inert materials. Waste can be treated by melting the waste material, binding it to another material and utilizing it in another process or product. The reactivity of the solid particles in the waste does not produce heat, but when it is thawed, all the energy required must be supplied in the form of external fuel. The reactions are thus endothermic. Often the waste particles are agglomerated of many small particles and thus have a porous structure.

According to Fl Patent 91283, a method and apparatus for raising the temperature and mixing efficiency of non-combustible powdery solids to a level sufficient to achieve the desired melting and evaporation are known. The invention is characterized in that the heating and mixing takes place in at least two steps. The reaction shaft is fed with a mixture of fuel and oxygen or oxygen-enriched air which ignites and into which the flame is fed a non-combustible solid. The furnace is equipped with various burners to produce heat: 25 in addition to powdered material and air / oxygen supply. The reactions are: carried out in a suspension melting furnace.

U.S. Patent Nos. 4,653,077 and 4,732,368 discloses a method and apparatus for melting waste and slags. Also in the solutions according to these publications, fuel 2 116571 is fed together with oxygen or oxygen-enriched air into the reactor and the feed to be melted is subsequently fed to the reactor.

Fl patent 108865 discloses a device for feeding a finely divided sulphidic solid and an oxygen-containing oxidizing gas into a slurry melting furnace, whereby the solid and the oxidizing gas are suspended in a separate suspension formation state before being fed to the reaction space. The invention makes the combustion of the feed material more homogeneous.

When using separate burners in the reaction mode to generate energy, it is difficult to cause the flame to transfer heat to the material to be melted. In addition, the thermal load of the reaction walls is high and difficult to control since some of the radiation from the burner flames is directed to the walls causing local overheating.

It is an object of the present invention to provide a novel solution for melting an inert material such as waste in a metallurgical temperature reactor such as a flame smelting furnace. In particular, it is an object of the invention to enhance the melting of an inert material in a flame smelting furnace by at least forming a slurry of the fuel producing heat of combustion and oxidizing gas prior to their introduction into the flame smelting furnace.

The invention is characterized by what is stated in the characterizing part of claim 1. Other embodiments of the invention are characterized by what is stated in the other claims.

: 25 / The solution according to the invention provides considerable advantages. Invention, ···. is directed to a process for melting an inert material, such as waste, in a metallurgical temperature reactor, such as a flame smelting furnace, wherein at least the inert material is fed through a separate mixing valve to the temperature reactor t? 30, wherein at least the inert material and the fuel are mixed with the oxidant gas in a separate mixing state into a slurry substantially before being fed by their temperature reactor reactions. Further, according to the invention, the suspension is passed through a reaction of a preheated temperature reactor to ignite the suspension and further melt the inert material. When the suspension 5 is formed prior to ignition of the fuel, the combustion will be uniform in the suspension. By feeding the inert material, fuel, and oxidizing gas, i.e., oxygen or oxygen-enriched air, already in suspension into the temperature reactor, the heat released by the fuel particles is effectively transferred to the inert particles, whereupon the inert particles melt. When the fuel is mixed in the suspension, heat transfer between the combustible fuel particles and the meltable inert particles is very effective compared to if the fuel were to be fed later.

The inert material fed to the temperature reactor is finely divided so that the particles 15 have a maximum diameter of 0.2 millimeters. Being small inert particles, they are better able to melt in the temperature reactor.

According to one embodiment of the invention, the fuel used is a gaseous fuel, such as natural gas. According to another embodiment of the invention: · According to another embodiment, the fuel used is a solid fuel such as coal dust.

·; When using solid fuel, the fuel can be mixed with an inert material even before the mixture is fed into the mixing space.

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According to one embodiment of the invention, the inert material melts

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:, · * 25 generated dust and gases are removed from the temperature reactor. According to one embodiment of the invention, a binder such as; ''; silicate. According to one embodiment of the invention, the diffuser burner is used as the mixing space. By diffuser burner is meant a device having a separate space for forming a slurry prior to feeding the slurry into the reactor. According to one embodiment of the invention 4 116571, a flame smelting furnace is used as the metallurgical temperature reactor.

Due to the reactions in the slurry and the heat transfer, the thermal load on the walls of the 5 temperature reactors is also well controlled and no overheating occurs. Thus, the reaction temperature can be kept very high, for example by adding oxygen enrichment, without the amount of heat transferred to the walls of the melting unit being detrimental to the reactor itself and correspondingly low waste heat. The solution according to the invention can also be considered as an economical and efficient method for melting waste or similar inert material. Preferably, according to the invention, no additional burners are needed to bring heat to the reactor. The combustion of the fuel in the suspension maintains the temperature of the temperature reactor at such a high level that ignition occurs as soon as the suspension enters the reaction state.

15

In the following, the invention will be illustrated by means of a figure.

· ', · *; Figure 1 Implementation of the method according to the invention; Fig. 1 shows a process according to the invention for melting an inert material 1, such as waste, in a metallurgical temperature reactor 8 such as a flame smelting furnace. The inert material is fed through a separate mixing cock 2 into the reaction space 3 of the preheated temperature reactor 8, and each inert material 1 and fuel 4 such as carbon dust are mixed with the oxidation gas 5 in a 2: i: 25 slurry 6 substantially before feeding the slurry to the ... the wall is provided with a sufficient number of nozzles 7 through which the oxidizing gas 5 can be discharged at various points in the mixing. * ··! When using solid fuel as an example,; ! *, the fuel can already be mixed with the inert material to be melted: 30 before being fed into a mixing space such as a diffuser burner.

5, 116571

When discharged from the mixing chamber by the reactions 3 of the temperature reactor 8, the fuel particles in the suspension 6 are ignited and heat is transferred from the particles to the inert particles which are melted by the heat. When the reactants are in suspension even before the fuel ignites, the heat transfer between the combustible fuel and the inert material to be melted is effective. The molten material is removed from the bottom of the temperature reactor through a drain hole and the material is further processed as required. Dusts and gas formed during melting are removed with the combustion gases from the temperature reactor. The dust is separated from the gas, for example in a gas purification unit, and possibly recycled to a temperature reactor with an inert feed.

The invention will now be explained in more detail by way of example.

Example 15

By way of example, the process according to the invention is used to melt dust of an LD steel converter, classified as hazardous waste, in a usable form in silicate bonded form. When treated in this manner, the aforementioned dust can be utilized, for example, as a construction material or stored ;; '20 landfill.

The LD converter dust (Fe 33%, CaO 28%, S1O2 4%, C 2%, iron in dust as hematite) is fed at 5 t / h (= tons / hour) to a metallurgical temperature reactor, such as a flame smelting furnace, mixed through a diffuser burner amount of carbon dust (concentration: C 72.2%, H 4.8%, 1.21 t / h) to generate melting energy and sand (content: SiO 2 90%) to generate 2.1 t / h of silicate slag. Oxygen for coal combustion »*» *: · *: supplied to the same burner with oxygen enriched air (oxygen 1710 Nm3 / h and: X air 1127 Nm3 / h).

: 30 6 116571

The inert material (dust from the LD converter), the silicate (sand), and the carbon are mixed before being fed to the diffuser burner. In the burner, the oxygen-enriched air is mixed with the solids mixture, so that all four components (dust, sand, carbon and oxygen) are homogeneous in suspension upon reaction. The reactions 5 are preheated and its temperature remains high due to the burning of the carbon contained in the suspension. The inert dust particles and the sand heat up to the melting temperature while in suspension in the reaction state and react with each other to form molten silicate slag at the bottom of the temperature reactor according to Example 6.8 t / h (Fe 23.0%, SiO 2 30.0%, CaO 18.8%, 1300 ° C 9). The molten material 10 is discharged from the outlet of the temperature reactor and cast into ingots or granulated with, for example, water, depending on the intended use. In addition, the temperature reactor produces gas (3783 Nm 3 / h and temperature 1333 ° C 9).

It will be apparent to one skilled in the art that various embodiments of the invention are not limited to the above examples, but may vary within the scope of the appended claims.

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Claims (8)

A method of melting inert material (1), such as waste in a metallurgical flame melting furnace (8), wherein at least the inert material is measured through a special mixing space (2) in the reaction space (3) of the flame melting furnace, characterized in that at least the inert material (1) and fuel (4) are mixed with the oxidizing gas (5) in the particular mixing compartment (2) to a suspension (6) substantially before being fed into the reaction space (3) of a flame melting furnace (8). 10 Process according to claim 1, characterized in that the suspension (6) is led into the reaction space (3) of the preheated flame-melting furnace (8) to ignite the suspension and further to melt the inert material. 15 Method according to Claim 1 or 2, characterized in that the inert material is finely divided, the particles having a diameter of not more than 0.2 mm. j 4. Process according to claim 1, characterized in that a gaseous fuel such as natural gas is used as fuel. in Process according to claim 1, characterized in that a solid fuel, such as coal powder, is used as fuel. 25 Process according to any of the preceding claims, characterized in that dust and gases formed during the melting of the inert material are removed from the furnace of flame. in Process according to claim 1, characterized in that a binder, •. As silicate is further fed into the mixing space (2). 10 1 1 6571 Method according to Claim 1, characterized in that a diffuser burner is used as mixing space (2). i * »») # »t