RU2092588C1 - Method of producing agglomerated stock from sulfur material - Google Patents

Abstract

FIELD: ferrous metallurgy. SUBSTANCE: filter bed is formed to absorb sulfur releases taking place upon thermally treating ore material. Filter bed consists of lump iron-containing screening of thermally treated product and limestone flux. Size of flux is 2-3.5 as high as that of thermally treated product and its content in bed is maintained within the range 1-(2-10). EFFECT: improved environmental condition. 1 tbl

Description

 The invention relates to ferrous metallurgy, more specifically associated with ensuring environmental safety of mining and metallurgical complexes.

In the known methods for the production of agglomerated raw materials, a bed is used from its own heat-treated product, an interlayer of granular iron-containing material moistened with lime pulp, which provides absorption of sulfur-containing substance [1]
Closest to the proposed technical solution is a method for the production of agglomerated raw materials from sulfur materials, including pelletizing the charge; laying on the machine the bed layers and the actual mixture and their subsequent heat treatment, in which a mixture of iron and CaO-containing materials is used as a bed [2] Alkaline earth metal oxides or hydroxides, in particular CaO, and iron-containing material are used as CaO-containing material represented by sinter charge components. Moreover, the CaO-containing component is more dispersed than the sinter charge component. The use of CaO-containing components in the form of oxides or hydroxides is limited by the absence of lime-burning plants at a number of metallurgical enterprises and requires capital expenditures to organize the corresponding production.

 In addition, the use of highly dispersed components as a bed is associated with a decrease in the gas permeability of the layer and a deterioration in sintering, firstly, and a significant dust removal (and a corresponding deterioration in the environmental situation), and secondly.

 One of the main problems associated with the processing of sulphurous ores by the thermal-oxidative process is caused by the formation of a significant amount of sulphurous compounds, which, together with the exhaust gases, are evacuated to the atmosphere. Abroad, for the capture of sulfur compounds behind roasting machines, systems of sulfur treatment plants are provided, the construction and operation of which requires considerable material costs.

To capture sulfur compounds in the proposed solution, a filter bed is organized where sorption of sulfur compounds is carried out. The concentration of sulfur compounds in emissions when using such a filter is in equilibrium for a given temperature. The temperature of the bed in the process of agglomeration of raw materials ranges from 200 800 ^o C.

 The efficiency of a filter bed is determined by two factors such as gas permeability and reaction surface.

 The gas permeability of the filter bed is ensured both due to a certain content of limestone flux in the bed, and due to a certain granulometry of the flux, and these factors are interrelated. The presence in the filter bed of a frame made of a sufficiently durable heat-treated product gives it the necessary strength. This is just the new quality that occurs when the filter bed is formed.

 The reaction surface of the filter is formed due to the content of the sorbent (limestone flux) of optimal particle size distribution. It is well known that for reversible reactions, which undoubtedly include the interaction of flux with sulfur compounds, the completeness of the interaction is achieved with a certain excess of reagent. The experimentally determined excess coefficient values for the Ca / S ratio were 3.5 5.0. In terms of limestone flux for charge conditions in Russia, this gives such limits on its content in the filter bed as 1: (2-10). The lower limit of 1:10 corresponds to the processing conditions of the low sulfur blend (S≅0.3%) and means that the filter is formed from one part of limestone flux and ten parts of a heat-treated product. The upper limit is due to an increase in sulfur content in charge materials (S> 0.4). In this case, the content of limestone flux in the filter bed is increased so that one share of the flux accounts for two parts of the heat-treated product. Reducing the flux content in the filter below the lower limit (below 1: 10 significantly reduces the reaction surface of the filter and does not allow to achieve high levels of purification of exhaust gases. An increase in the flux content in the filter above the upper limit, i.e. above the ratio (1: 2), worsens its strength properties and makes it practically inoperative. At the same time, it is necessary to take care of the granulometry of the flux. With a low flux content (lower limit), the best gas-dynamic characteristics correspond to a flux size of 2 caliber average At a high flux content (upper limit), optimal gas dynamics are ensured when its size is 3.5 caliber of the average piece of heat-treated product supplied to the bed.

 Pure limestone, dolomitic limestone, melted limestone, as well as complex fluxing materials (for example, limestone with additives of gypsum, chalk, marl, etc.) can be used as limestone flux.

 Examples of specific implementation of the method.

To illustrate, we chose the production of pellets fluxed to a basicity of 1 from concentrates with different sulfur contents, which are found in the practice of producing iron ore pellets (0.3-0.5%). The residual content of S in the pellets is 0.1%. The fractional composition of the suitable pellets, from which the bed is also separated, is 95% represented by a fraction of 8 16 mm, i.e. the average size of the bed fraction is 12 mm. As follows from the material balance, to obtain a ton of pellets, 899 kg of concentrate with a content of 4.5% SiO ₂ will be required (the rest is limestone and bentonite).

 Example 1

The sulfur content in the concentrate of 0.32% Ca / S ratio for this case is 3.5. Sulfur emission is determined solely by its content in the concentrate, since other charge components in this case do not contain sulfur, and will amount to, kg / t:
899 • 0.32 / 100 1000 • 0.1 / 100 1.88,
Where
0.32, 0.1, respectively, the content of S in the concentrate and finished pellets,
The required amount of limestone in bed is calculated as follows, kg / t of pellets:
1.88 • 3.5 • 100/40 16.45,
Where
100/40 stoichiometric conversion factor for Ca into limestone.

 Bed consumption is not difficult to obtain from the ratio of the heights of bed layers and raw pellets, provided that they have the same bulk density: in traditional methods of firing a bed layer of 100 mm with a layer height of 400 mm of calcined material. Therefore, the ratio of the heights of the bed layers and pellets will be 100: 400 or 1: 4, i.e. bed consumption will be equal to 0.2 t / t (200 kg / t of pellets).

Then the ratio of limestone and calcined product in the composition of the bed will be determined from:
16.45: (200 16.45) 16.45: 183.55 1:10,
which meets the lower declared limit.

In this case, the size of the limestone fraction in bed will be:
12 • 2.0 24 mm.

 Example 2

The sulfur content in the concentrate is 0.52% Sulfur emission will be, kg / t of pellets:
899 • 0.52 / 100 1000 • 0.1 / 100 3.67.

The Ca / S ratio for this case is 5.0. The required amount of limestone is obtained from, kg / pellets:
3.67 • 5.0 • 100/40 45.9.

In this case, the ratio of limestone and calcined product in bed will be:
45.9: (200 45.9) 45.9: 154.1 1: 2,
i.e., meets the upper declared limit. For this case, the size of the limestone fraction in bed is:
12 • 3,5 42 mm.

 It is advisable to evaluate the effectiveness of the proposed technical solution when comparing it with the indicators of the most modern types of desulfurization plants, for example, such as the TIFELLA LIFAC system.

 Comparative indicators of the proposed option for the purification of exhaust gases from sulfur and patented by TAMPELLA and implemented on a roasting machine of Karelsky Okatysh JSC are presented in the table.

 Thus, there is undoubtedly a significant advantage of the proposed method of firing with the capture of sulfur emissions.

 It should also be noted that the method can be implemented without significant capital investments.

Claims (1)

 A method for the production of agglomerated raw materials from sulfur materials, including pelletizing, laying on the machine bed layers from a mixture of lumpy iron and CaO-containing materials and a mixture and their subsequent heat treatment, characterized in that limestone flux is used as the CaO-containing material, and as iron-containing material use screening of the heat-treated product, and the size of the limestone flux is chosen equal to 2.5 3.5 caliber pieces of screening of the heat-treated product, and the content of fl ca in the bed is maintained in the range of 1 (2 -10).

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