RU2740741C1 - Method of processing fine-dispersed raw material in a flash smelting furnace - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to a method of processing fine-dispersed raw material in a smelting furnace of horizontal or vertical type, in particular, fine sulphide ore concentrates, concentrates of technogenic deposits containing non-ferrous metals, characterized by low content of sulfur. Method for processing fine-dispersed feedstock in a smelting furnace includes feeding a metal-containing charge and a flux in the form of a downhole charge-and-gas flame into the reaction zone of said furnace with an oxygen or air stream enriched in oxygen, passage of gas flow through the zone of the apron installed on the surface of the arch of the settling tank of the furnace, melting of the charge with formation of melts of matte and slag or metal and slag, separation of the latter by settling, separate withdrawal of liquid products of melting and gases, note here that canopy with height up to 1/2 of average height of gas underroof space of furnace is installed across gas flow over entire width of settler in last third of length of settler roof between reaction shaft and furnace uptake. Said canopy is made of refractory blocks or water-cooled elements. Method is carried out in horizontal melting furnace of horizontal type.

EFFECT: higher efficiency of suspended smelting process, possibility to process fine-dispersed raw material, reduced probability of skull formation in the uptake and slag bath of the furnace.

3 cl, 7 dwg

Description

The invention relates to the field of metallurgy of non-ferrous metals, in particular to the smelting of raw materials containing non-ferrous metals, in a suspended smelting furnace and can be used to melt finely dispersed raw materials, to reduce the loss of non-ferrous metals with slags and to reduce the likelihood of deposition in a settling tank, a pharmacy and a heat recovery boiler (KU) suspended smelting furnaces (PVP).

The invention is aimed at involving in the processing in PVP raw materials of non-ferrous metals (sulfide ore concentrates, concentrates of technogenic deposits), characterized by a reduced particle size (particle size), that is, raw materials, in the oxidative smelting of which in a suspended state the processes of enlargement and interaction of particles are limited by their size, as a result, the indicators of dust removal and, accordingly, the likelihood of deposit formation in the settling tank, pharmacy and heat recovery boiler for suspended smelting furnaces increase.

There is a method of suspended smelting of finely ground sulfide raw materials containing metals, for example, copper, nickel and lead, including feeding the raw material into the suspension smelting furnace together with flux and oxidizing gas to form a suspension of particles in the reaction shaft of the furnace and at least two molten phases ( US patent 4139371).

In traditional flash smelting, finely ground sulphide feedstock containing metals such as copper, nickel and lead, recycled dust and fluxes, and air and / or oxygen mixture used as oxidizing gas, preheated or cooled, are fed into a vertical the reaction shaft of the suspension smelting furnace from top to bottom so that oxidation reactions take place at a high temperature. Due to the influence of the heat of reactions and possible additional fuel, most of the reaction products will melt. From the reaction shaft, the suspension enters the horizontal part of the furnace, that is, into the settler, which contains at least two, but sometimes three layers of the melt. In the case where the sump contains three melt layers, the lowest layer is the metal layer in the feed. More often, there are only two melt layers in the furnace: at the bottom there is a matte or a layer of metal and a layer of slag above it. Most of the molten or solid particles in the slurry go directly to the melt that is at the bottom of the reaction shaft at a temperature approximately equal to that of the slag, while the finer-grained ingredients continue to move to the other end of the furnace. Throughout the entire path, the particles of the suspension are deposited in the sump melt. From the other end of the settler, the waste gases enter the vertical shaft of the suspended smelting furnace, from where they enter the gas processing unit, which consists of a heat recovery boiler and an electrostatic precipitator. It is attempted to melt the charge in the suspension smelting furnace as autogenously as possible, without external fuel, by means of preheating and / or by means of oxygen enrichment of the oxidizing gas supplied to the reaction area.

The finest particles of the charge, as well as particles that have not reacted or melted, tend to leave the suspension smelting furnace together with the gas flow due to the fact that their surface area / weight ratio is higher than that of molten particles. These particles are released from the gas phase in the KU, and the finest particles are captured in the electrostatic precipitator. Particulate matter released in the gas processing plant, i.e. dust carried away by gases is returned to the flash smelting furnace. Recirculation of dust carried by gases increases energy consumption, which is compensated by the supply of additional fuel. Increasing the use of additional fuel increases the total amount of gas in the flash smelting furnace.

The method has the following disadvantages:

- an increase in the content of fine particles in the processed charge, mainly consisting of ore raw materials, technogenic raw materials, recycled materials (dust) and flux, leads to an increase in dust emission;

- an increase in dust removal and a decrease in the size - particle size of PVP dust leads, in turn, to an increase in the likelihood of deposition in the gas path of the furnace, pharmacy and KU, which limits the possibility of trouble-free operation of the suspended smelting furnace.

Also known is an improved method of smelting in suspension fine sulphide raw materials, including supplying air and / or an oxygen mixture used as an oxidizing gas into a vertical reaction shaft of a suspended smelting furnace from top to bottom so that oxidation reactions take place at a high temperature; the improvement of the method consists in deflecting the gas flow and pressing it against the surface of the melt in the furnace, thereby reducing the likelihood of build-up in the gas path of the furnace, pharmacy and KU. The deflection of the gas flow to the slag surface is realized by installing a canopy on the roof of the PVP settler. A canopy up to 300 mm high is installed across the entire width of the furnace perpendicular to the gas flow of the PVP settler. The best is to install a visor 2 meters from the pharmacy. The flow velocity at the installation site of the beam increases from 18 to 25 m / s. (The mechanism of formation of refractory crust in furnaces of suspended smelting and methods of its elimination. Abstract of the dissertation of the candidate of technical sciences: 05.16.02 / Krupnov Leonid Vladimirovich; [Place of defense: National Mineral Resources University "Gorny"] - St. Petersburg, 2015. - 19 p. URL: https://search.rsl.ru/ru/record/01005562882).

The method is taken as the closest analogue, but it has the following disadvantages:

1. The indicated height of the canopy (300 mm), given low melt levels and a height of the under-roof space exceeding 1000 mm, will not lead to an effective deflection of the gas flow and, accordingly, will not provide the expected result.

2. Installation of a canopy 2000 mm from the pharmacy at high rates of PVP and high gas flow rates exceeding 30-35 m / s will result in the horizontal gas flow reaching the end wall of the PVP, which can contribute to the formation of unwanted vortices and the precipitation of dust particles in the cold zone of the furnace ...

The objective of the claimed invention is to ensure stable, trouble-free operation of PVP when processing finely dispersed raw materials with an increased content of particles of the sludge class (-10 microns).

The technical result of the claimed invention is to increase the productivity of the suspended smelting process, reduce the likelihood of deposition in the gas path of the furnace, pharmacy and KU.

The specified technical result is achieved by the fact that in the proposed method for processing fine raw materials in a suspended smelting furnace, including the supply of a metal-containing charge and a flux in the form of a charge-gas torch into the reaction zone of the said furnace by a stream of oxygen or oxygen-enriched air, the passage of the gas flow through the zone installed on the surface of the roof the sump of the furnace, the visor on the roof of the sump, melting of the charge with the formation of matte and slag melts, separation of the latter by settling, separate withdrawal of liquid products of smelting and gases, in contrast to the closest analogue, the visor (spoiler), up to 1/2 of the average height of the gas under-roof space of the furnace is set across the gas flow across the entire width of the settler, in the last third of the length of the settler arch between the reaction shaft and the furnace chamber.

The canopy can be made of refractory blocks (bricks) or water-cooled elements (caissons).

The method can be carried out in a horizontal suspended smelting furnace.

The proposed technical solution is illustrated by graphic materials.

FIG. 1 shows a diagram of the installation of a visor in a vertical PVP.

FIG. 2 shows the geometric dimensions and a diagram of the gas space of the settling tank and the PVP pharmacy.

FIG. 3, table 1 shows the calculation of the area of the gas space of the settling tank and the PVP pharmacy.

FIG. 4 shows the estimates of the gas flow velocity fields in the calculation area of the furnace:

- without visor (a);

- when installing a visor measuring 200 mm by 200 mm (b).

FIG. 5, table 2 shows the effect of the size of the visor on the proportion of particles (% rel.) Of variable size and density, dropped out of the gas-dust flow of the PVP settler.

FIG. 6 shows graphs of the effect of the canopy on the static pressure in the furnace.

FIG. 7, table 3 shows the operating conditions of the NMP PVP.

The essence of the proposed method is as follows

Smelting of sulphide concentrate containing non-ferrous metals is carried out in a suspended smelting furnace (PVF). The method includes feeding crushed sulfide concentrates, fluxes, oxygen-containing gas and other components of the charge into the furnace, smelting, separating smelting products into matte and slag, and periodically dispensing smelting products. According to the invention, the implementation of the method is carried out in a PVP with a vertical or horizontal scheme for feeding the charge.

The horizontal gas-dust flow of the PVP settler, when passing through the zone of the installed visor, deviates, pressing against the surface of the melt. In this case, the process of additional assimilation of dust particles transported by the gas flow by the slag melt is initiated. Behind the zone of installation of the visor, due to turbulence and expansion of the gas flow, a zone of reduced velocities arises, which favors additional precipitation of dust from the flow. In addition, an additional decrease in the flow rate occurs due to the transition of the flow to the pharmacy area.

The visor should be installed over the entire width of the furnace gas space to press the entire flow to the melt surface.

The installed canopy is characterized by a relatively short length (less than 1000 mm), which limits the likelihood of "blocking" the gas flow in the area of the canopy installation and the occurrence of problems with evacuating the furnace exhaust gases - FIG. 1. In the case of overlapping more than 50% of the under-roof space of the furnace with a canopy, a significant decrease in the efficiency of evacuation of furnace gases is possible. In the event that the visor covers less than 20% of the furnace under-roof space, the deviation of the exhaust gas flow will be insignificant, the installation of the visor will not lead to the desired result.

The place of installation of the visor - the last third of the length of the sump vault between the reaction shaft and the PVP pharmacy is determined by the length of the zone of "normalization" of the gas flow deflected by the visor. If the visor is brought closer to the pharmacy, the flow deviation will be distorted and leveled by the influence of the pharmacy. In the event that the visor is brought closer to the reaction shaft, the efficiency of its operation will be reduced due to the complete normalization of the flow when it moves from the visor to the pharmacy. The recommended position of the visor leads to a synergy of two factors contributing to the loss of dust from the gas stream - the pressing of the stream to the melt surface (the result of installing the visor) and a decrease in the gas flow rate when the stream enters the pharmacy.

When implementing the method in a PVP with a horizontal scheme of charge supply, the mechanism of action of the visor is similar, but under conditions of a two-sided (from two ends of the furnace) installation of charge sprayers, gas-reflecting visors (spoilers) are also installed on both sides of the pharmacy located in the center of the PVP settler.

The visor material must be inert to the highly oxidizing gas stream. Accordingly, the visor is made of a refractory material that does not contain graphite, or from caisson elements, since the temperature of the most heat-loaded borders of the visor can reach 1400-1450C.

Justification of parameters

Accepted initial data for subsequent calculation

Used parameters of gas-dust flow

- average composition of gases (% vol.):

33 SO ₂ ; 0.5 SO ₃ ; 14.2 H ₂ O; 12 CO ₂ ; 2.8 O ₂ ; 37 N ₂ ; 0.5 Ar

- gas consumption: Q = 61000 nm ³ / h;

- average gas temperature: t _g = 1250 ° С

- gas properties correspond to ideal gas.

The calculations were carried out for particles with a size of 10 μm, 50 μm, 100 μm, characterized by a density of 2300 kg / m ³ , 3800 kg / m ³ , 5500 kg / m ³ , respectively.

Sump dimensions

The geometrical dimensions and the diagram of the area of the gas space of the settling tank and the PVP pharmacy are shown in Fig. 2.

The calculation of the area of the gas space of the settler and the PVP pharmacy is presented in table 1, in Fig. 3.

Calculation

Numerical simulation of turbulent gas flow (using the standard k-ε model) was carried out using the ANSYS Fluent package. Gas flow near solid surfaces was modeled using the method of wall functions. This approach allows, with sufficient accuracy in engineering practice, to calculate near-wall turbulent flows without a detailed calculation of the multilayer structure of the boundary layer. Due to the technological features of the suspended smelting furnace, the volumetric content of solid particles in the sump and pharmacy zones is low, and they do not have a noticeable effect on the movement of the gas phase. This makes it possible to significantly simplify the mathematical model and consider the motion of the gas phase and solid particles separately.

Particle motion was simulated using the obtained averaged velocity fields. For these purposes, a special author's program was created. Estimates show that the main forces acting on a particle are the force of hydrodynamic resistance and the force of gravity.

At the initial moment of time, a number of particles were placed at the beginning of the lower shaft tunnel, evenly distributed within a given initial volume. The particle velocity at the initial moment was set equal to the gas flow rate at this point. After that, the equations of motion of each particle were numerically integrated until the particle was inside the marked finite region, which corresponded to the successful passage of the particle through the shaft, or until the particle collided with the walls of the shaft.

If during integration it was found that the particle is outside the geometry of the modeling area, then the particle sticking point was the point of intersection of the segment between the last known point inside the modeling area and the current position of the particle that flew out of the modeling area.

Justification of the installation site of the canopy on the sump vault The estimates were made using a canopy with a height of 200 mm (40% of the accepted height of the sump gas space) to 500 mm (70% of the accepted height of the sump gas space). The aim of the simulation was to construct the velocity field of the gas flow in the investigated area of the gas space of the furnace. An example of the change in the velocity field of the gas flow as a result of the installation of the visor is illustrated in Fig. 4.

If the visor is installed at a distance of more than 3000 mm from the pharmacy, then the horizontal flow restored after the effect of the visor will turn into a vertical flow in the central zone of the pharmacy, which will contribute to additional precipitation of dust particles from the stream by reducing the flow rate. The indicated position of the visor is optimal.

When the visor is installed at a distance of less than 2500 mm from the pharmacy, the gas-dust flow pressed against the slag melt, passing under the pharmacy, will be localized in the "end" zone of the oven and the pharmacy, increasing the likelihood of build-up in the slag end of the oven.

When the visor is installed at a distance of more than 3500-4000 mm from the pharmacy, the flow restored after the influence of the visor will be pressed against the settling tank-pharmacy transition, similar to the design of the furnace without a visor: the installation efficiency of the visor will be reduced.

Justification of the geometric dimensions of the visor

The following dimensions of the installed visor are considered:

1. The original version of the sump without a canopy;

2. A visor measuring 200 × 200 mm across the entire width of the sump at a distance of 3000 mm from the entrance to the pharmacy;

3. A visor of 500 × 500 mm across the entire width of the sump at a distance of 3000 mm from the entrance to the pharmacy;

4. A visor measuring 500 × 270 mm across the entire width of the sump at a distance of 3000 mm from the entrance to the pharmacy, where 270 mm is the height of the visor;

5. A visor measuring 500 × 200 mm over the entire width of the sump at a distance of 3000 mm from the entrance to the pharmacy, where 200 mm is the height of the visor.

The effect of the visor size on the proportion of particles (% rel.) Of variable size and density, precipitated from the gas-dust flow of the PVP settler is illustrated by the calculation results presented in Table 2, Fig. 5.

The presence of a visor affects the deposition of large particles (100 microns), the density of which is 2300 kg / m ³ . Large particles of higher density are deposited in the melt regardless of the size of the visor.

The visor has the greatest influence on the loss of particles of average diameter (50 microns). Moreover, the main role is played by the height of the visor, and not its length. The proportion of particles deposited in the melt increases from 6% to 60% (visor with dimensions of 500 × 500 mm) and from 6% to 9% (visor with dimensions of 200 × 200 mm). The above data refer to particles with a density (p) of 2300 kg / m ³ . For particles of higher density, the presence of a visor also leads to a significant increase in the number of particles falling into the melt.

The greatest influence on the precipitation of particles into the melt is exerted by a visor with a size of 500 × 500 mm.

The visor increases the resistance to the flow of flue gases. Examples of the distribution of static pressure in the investigated area of the gas space of the furnace are shown in Fig. 6. Installation of a 200 × 200 mm canopy leads to a difference in static pressure at the inlet and outlet of the sump of about 20 Pa (2 mm HV), and installation of a 500 × 500 mm canopy leads to a difference in static pressure at the inlet and the outlet from the sump is about 300 Pa (30 mm h.c.).

From the above analysis, we can conclude that the best option is a visor with a size of at least (D × H) 200 × 350 mm (it covers half of the section of the gas phase of the settler). The installation of such a canopy will significantly increase the deposition of medium-sized particles (50 μm) into the melt.

Thus, the recommended height of the canopy was 300-500 mm (up to 50% of the minimum height of the gas space of the PVP sump), the recommended place for installing the canopy is 2500-3000 mm from the transition of the sump vault to the pharmacy along the furnace axis. The recommended width of the canopy up to 1000 mm is not a basic dimension and is determined by the design features of the furnace roof.

The method is illustrated by examples

Suspended smelting furnaces at the Nadezhda Metallurgical Plant (NMP) process copper-nickel sulphide concentrates to produce matte and slag, which are sent to depleting electric furnaces. The deterioration of the quality of the processed concentrates mentioned, which consists in a significant reduction in the particle size of the raw materials, has led to an increase in the likelihood of build-up in the pharmacy, the transition from the pharmacy to the waste heat boiler and at the inlet to the waste heat boiler. To combat build-up in PVP NMP, melts were carried out, providing for the installation of a visor at a distance of 2500 mm from the pharmacy, covering the entire section (width) of the settler.

1. For PVP NMP using the ANSYS Fluent package, a turbulent gas flow was simulated (using the standard k-ε model) in the furnace settler. Installation of a canopy with a width of 500 mm and a height of 270 mm over the entire width of the sump vault at a distance of at least 2500 mm from the entrance to the pharmacy leads to a reduction in dust emission into the dust cleaning system by 10-30% rel. depending on the size and density of particles of the gas-dust flow.

Simulation conditions:

- average composition of gases (% vol.): 33 SO ₂ ; 0.5 SO ₃ ; 14.2 H ₂ O; 12 CO ₂ ; 2.8 O ₂ ; 37 N ₂ ; 0.5 Ar;

- gas consumption: Q = 61000 nm ³ / h;

- maximum flow rate 23.3 m / s;

- average gas temperature: t _g = 1250 ° С;

- gas properties correspond to ideal gas.

Operating conditions of PVP NMP are presented in table 3, fig. 7.

The calculations were carried out for particles with a size of 10 μm, 50 μm, 100 μm, characterized by a density of 2300 kg / m ³ , 3800 kg / m ³ , 5500 kg / m ³ , respectively.

2. On the roof of the sump PVP NMP, along the entire width of the sump at a distance of 2500 mm from the entrance to the pharmacy, a visor 140 mm high and 600 mm wide is made of refractory bricks.

Operating conditions of PVP NMP are presented in table 3, fig. 7. In the course of instrumental measurements, a decrease in the surface temperature of the vault in the canopy zone by 150-170 ° C was established in comparison with the surface of the sump vault, which is located more than 1750 mm from the canopy to the center of the furnace. A decrease in the temperature of the gas space at a distance of 100 mm from the roof after the canopy by 10-30 ° C compared to the gas temperature in front of the canopy was noted, zero gas flow rates were noted behind the canopy at a distance of 90 mm from the roof.

No significant distortion of the gas flow of the furnace settler and a decrease in dust emission were found, which confirms the predicted need for installing a higher visor. It is necessary to increase the height of the canopy and raise the level of the molten bath in the furnace to reduce the height of the under-roof gas space.

3. On the roof of the sump PVP NMP, along the entire width of the sump of the sump at a distance of 2000 mm from the entrance to the pharmacy, a visor 300 mm high and 600 mm wide is installed from refractory bricks.

Operating conditions of PVP NMP are presented in table 3, fig. 7.

In the course of instrumental measurements, a decrease in the surface temperature of the vault in the canopy zone by 160-190 ° C was established in comparison with the surface of the sump vault, which is more than 1750 mm from the canopy to the center of the furnace.

Shown is the distortion of the gas flow due to a decrease in temperature after the canopy by 20-50 ° C at a height of 100 mm from the roof compared to the same level of measurement in front of the canopy. Zero gas flow rates were recorded after the canopy at a distance of 300-350 mm from the roof.

It was revealed that the velocity and volume of exhaust gases are the same before and after the canopy, the gas velocity varies in the range of 8-12 m / s, the volume of exhaust gases is in the range of 60,000-80000 m ³ / h.

During the test period, there was no violation of the rarefaction indicators on the sump roof and in the waste heat boiler. To increase the efficiency of the performance indicators of the visor, it is necessary to raise the melt bath to 1180-1300 mm, which, with the used melting performance, will provide an increase in the average gas flow rate in the sump from 8 to 10 m / s, in the area of the visor to 14 m / s.

Thus, the method of processing finely dispersed raw materials in a suspended smelting furnace allows to ensure stable, trouble-free operation of PVP when processing finely dispersed raw materials with an increased content of particles of the sludge class (-10 microns). When implementing the method, the productivity of the suspended smelting process is increased by reducing the likelihood of build-up in the gas path of the furnace, pharmacy and KU.

Claims (3)

1. A method of processing sulphide finely ground raw materials containing copper, nickel and lead in a suspended smelting furnace, including feeding a metal-containing charge and a flux in the form of a descending charge-gas torch into the reaction zone of the said furnace with a stream of oxygen or oxygen-enriched air, passing the gas flow through the zone of the set on the surface of the roof of the sump of the furnace, the visor on the roof of the sump, melting the charge with the formation of melts of matte and slag or metal and slag, separating the latter by settling, separate withdrawal of liquid products of smelting and gases, characterized in that they ensure the deflection of the gas flow and its pressing to the surface of the melt in furnace by installing a visor across the gas flow along the entire width of the settler in the last third of the length of the settler vault between the reaction shaft and the furnace chamber, while the height of the visor is up to 1/2 of the average height of the gas undervoltage space of the furnace. 2. A method according to claim 1, characterized in that the visor is made of refractory blocks or water-cooled elements. 3. The method according to claim 1, characterized in that it is carried out in a horizontal suspension smelting furnace.

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