CN105349801A - Method for chromium slag co-processing by means of smelting of laterite-nickel ores through ore-smelting electric furnace - Google Patents

Abstract

The invention discloses a method for co-processing chromium slag for smelting laterite-nickel ore in a submerged thermal electric furnace. The steps for co-processing chromium slag include: mixing chromium slag into the dry base of laterite-nickel ore according to a certain ratio, and then adding the chromium slag as a reduction coal as smelting agent or fuel as smelting raw material; pretreat the prepared smelting raw material to obtain calcine or sintered ore; put calcine or sintered ore into submerged thermal electric furnace to smelt nickel-chromium iron according to certain smelting parameters, At the same time, the purpose of detoxification of chromium slag is achieved. The invention fully combines the complementarity of laterite nickel ore and chromium slag components, not only realizes the detoxification of chromium slag, but also reduces the lime consumption in the smelting process, increases the chromium content in the ferronickel alloy, and improves the economic benefits of the enterprise, not only It is beneficial to the efficient and comprehensive treatment of hazardous solid waste in our country and can also realize resource utilization.

Description

A method for co-processing chromium slag in submerged heat electric furnace smelting laterite nickel ore

technical field

The invention relates to the field of solid waste treatment, in particular to a method for co-processing chromium slag by smelting laterite nickel ore in a submerged heat electric furnace.

Background technique

Chromium slag hazardous waste mainly comes from industrial production such as chromium salt and stainless steel, and generally contains 2% to 10% of chromium oxide, mostly in the valence state of trivalent chromium and hexavalent chromium. Hexavalent chromium will cause serious corrosion to organisms and the environment due to its strong oxidizing properties, while trivalent chromium is less harmful, but it is easy to be absorbed and accumulated, and there is a greater risk of migration and conversion to hexavalent chromium, leaching High toxicity. Therefore, chromium-containing wastes are highly toxic and have been included in the national list of hazardous wastes as Class I hazardous wastes.

At present, chromium slag is mainly treated by detoxification methods, including dry detoxification and wet detoxification. Dry detoxification is to mix chromium slag and carbon reducing agent in a certain proportion, then reduce and calcinate, and use the strong reducing property of CO at high temperature to reduce hexavalent chromium in chromium slag to trivalent chromium compound, so as to achieve the purpose of detoxification; wet method Detoxification is to first transfer the hexavalent chromium in the chromium slag to the aqueous solution, and then use a reducing agent to reduce the hexavalent chromium to trivalent chromium, and then perform solidification treatment. The wet detoxification methods mainly include: water dissolution reduction, acid dissolution reduction , Salt dissolution reduction and alkaline reduction.

The composition characteristics of hazardous waste determine that some hazardous waste can be disposed of in other industrial kilns other than the centralized hazardous waste disposal facilities, such as cement kilns, power plant boilers, ironmaking blast furnaces and other high-temperature furnaces. Since the 1970s, European and American countries have begun to vigorously develop the research and application of hazardous waste co-disposal technology in industrial kilns such as cement kilns. In my country, due to its own oxidizing properties, chromium slag can be harmlessly disposed in the reducing atmosphere of blast furnace ironmaking, and chromium-containing pig iron can also be obtained. Alternative raw materials are involved in raw meal ingredients. But present chromium slag detoxification method has the following problems:

Although the effect of dry detoxification is good, the cost of dry detoxification as a separate treatment is high and the economy is poor; the effect of wet detoxification is poor: the water-dissolved poison is not sufficient, and there is a phenomenon of "returning yellow"; The demand for large-scale detoxification is not suitable for bulk treatment; the detoxification effect of salt-dissolved poison is not ideal; the alkaline detoxification process is complicated and accompanied by secondary pollution. The blast furnace method can co-dispose chromium slag to achieve the detoxification effect of chromium slag. However, due to the high gangue content in chromium slag, it is not suitable to be implemented on large blast furnaces. Only small blast furnaces have a precedent for application, but small blast furnaces are required to be eliminated in the iron and steel industry according to national regulations. device of. The harmless treatment of chromium slag hazardous waste has increasingly become an urgent problem in this field.

Contents of the invention

The present invention aims to provide a method for co-processing chromium slag for smelting laterite nickel ore in a submerged thermal electric furnace to solve the problems of poor detoxification effect of existing chromium slag, high economic cost of detoxification, and unfavorable promotion of co-processing detoxification due to equipment problems.

At present, smelting laterite nickel ore in submerged thermal electric furnace is the main way to smelt ferronickel. The main components of laterite nickel ore are SiO ₂ , MgO, Al ₂ O ₃ and Fe ₂ O ₃ , and contain 0.2% to 1% of chromium. Electric energy is used as energy for reducing laterite nickel ore iron, nickel, chromium, slag, and ferronickel melting. Because lateritic nickel ore contains a large amount of _SiO2 , it is acidic. In the process of smelting with submerged thermal electric furnace, it is necessary to add a large amount of alkaline substances such as limestone as a slagging agent to adjust the slag alkalinity. The main component of chromium slag is CaO and MgO, and contains about 6% iron and about 5% Cr ₂ O ₃ , the chromium slag is alkaline because it contains a large amount of CaO and MgO, which is just complementary to the formation of laterite nickel ore, and can replace limestone as mineral heat It is used as slagging agent for smelting laterite nickel ore in electric furnace. In addition, the reducing agent used in the process of smelting laterite nickel ore in the submerged electric furnace can also reduce the Cr ₂ O ₃ in the chromium slag to Cr, which enters the nickel-iron water and becomes a valuable element of the nickel-chromium iron water. The chromium in the chromium slag Elements are reused, turning waste into treasure, reducing the amount of trace elements added in the smelting process of laterite nickel ore, and reducing costs.

In view of the above analysis, the present invention develops a method of low cost, low energy consumption, simple preparation process, smelting laterite nickel ore with submerged thermal electric furnace and co-processing chromium slag, so as to solve the problem of poor detoxification effect of existing chromium slag, high economic cost of detoxification, Co-disposal detoxification is not conducive to the purpose of promotion and other issues due to equipment problems.

The method for the co-disposal of chromium slag in submerged heat electric furnace smelting laterite nickel ore comprises the following steps:

1) The chromium slag is blended into the laterite nickel ore dry basis, the chromium slag and the laterite nickel ore dry basis are mixed according to a ratio of 1 to 5 wt%, and then 5 to 20% of the total mass of coal is added as a reducing agent or fuel, Fully mixed to obtain raw materials to be smelted;

2) Pretreat the prepared smelting raw materials to remove the physical water and crystal water in the raw materials to be smelted to obtain calcine or sintered ore;

3) Put the pretreated calcined sand or sintered ore into the submerged thermal electric furnace for smelting, and obtain molten nickel-chromium iron while detoxifying the chromium slag;

4) Formation of harmless slag.

Further, in the process of the above-mentioned pretreatment materials in the step 2), because the amount of chromium slag added is small, the existing submerged heat electric furnace pretreatment process can be used. At present, the main pretreatment process includes rotary kiln method or sintering Law.

Further, the smelting parameters in the submerged electric furnace in step 3) include: the smelting temperature in the submerged electric furnace is controlled at 1500-1650°C, the ternary basicity of the slag is controlled between 0.55-0.7, and the content of FeO in the slag is controlled Below 1 wt%.

Further, the content of Cr ₂ O ₃ in the slag is controlled below 0.15wt%.

Further, when the pretreatment process is the rotary kiln method, the calcined sand described in step 3) is loaded into the submerged thermal electric furnace in the way of hot delivery and hot charging; when the pretreatment process is the sintering method, in step 3) The sintered ore is cooled first and then sieved before being loaded into the submerged heat electric furnace.

The chromium slag includes chromium salt chromium slag, stainless steel slag, stainless steel dust and the like. The dry base of the laterite nickel ore can be obtained by drying the natural laterite nickel ore in a drum kiln. The heating source of the rotary kiln and the sintering machine adopts coal with a calorific value of 5000-6000kCal, and the coal includes bituminous coal and lignite.

The ternary basicity of slag in the smelting parameters refers to the mass ratio of CaO+MgO to SiO ₂ . The FeO content in the slag is controlled below 1wt%, in order to fully reduce the chromium oxide, and a small amount of unreduced chromium oxide also exists in the slag in the form of trivalent, which realizes the detoxification, solidification and resource utilization of chromium. In addition, the control of the basicity of the slag is also an optimal choice based on the addition of chromium slag. The mass ratio of CaO+MgO to _SiO2 is controlled between 0.55-0.7, and the smelting temperature in the submerged electric furnace is controlled at 1500-1650°C to facilitate smelting Reduction with chromium oxide, so as to ensure that chromium enters ferronickel water from chromium slag, and fully realizes resource utilization.

The mass ratio that chromium slag is mixed into laterite nickel ore among the present invention is determined according to slagging system and electricity consumption, through a large amount of theoretical analysis and practice, the mass ratio that chromium slag of the present invention is mixed into laterite nickel ore is 1%～5 % is the best, so that the Cr element is fully reduced to the molten iron, and at the same time, the content of the key chromium oxides and chromate accumulated substances in the chromium slag reaches the minimum, and the complete detoxification of the chromium slag can be realized.

The method for co-processing chromium slag by smelting laterite nickel ore in the submerged thermal electric furnace of the present invention can not only realize the detoxification of chromium slag, but also reuse the chromium element in the chromium slag to realize resource utilization; and combine the submerged thermal electric furnace to smelt laterite nickel The characteristics of the ore can not only increase the chromium content in ferronickel, but also reduce the amount of slagging agent used, and significantly improve the economic benefits of the enterprise; in addition, there are hundreds of submerged electric furnace smelting equipment for laterite nickel ore of the present invention in my country , which facilitates the short-distance transportation of chromium salt chromium slag and stainless steel slag near the factory, reduces the transportation cost and the secondary risk in the transportation process; Efficient comprehensive treatment of waste.

detailed description

The present invention is described in further detail below in conjunction with embodiment.

Example 1

The smelting equipment in this embodiment adopts a rotary kiln-submerged electric furnace (RK-EF), and the rated power of the submerged electric furnace is 15000kVA.

The undried laterite nickel ore contains about 30% physical water in its natural state, and it is sent to a drum drying kiln for drying to remove the physical water in it to obtain the dry basis of laterite nickel ore. The dry basis composition of laterite nickel ore is shown in Table 1 .

The chromium slag adopts chromium salt chromium slag, and the specific composition of the chromium slag is shown in Table 2. The chromium slag and the laterite nickel ore dry basis are weighed and mixed according to the mass ratio of 2wt%, and at the same time, 30% of the total mass of the stainless steel slag and the laterite nickel ore dry basis is added. 10% lump coal is mixed as reducing agent.

The prepared raw materials are sent to the feed inlet of the φ3.2m×65m rotary kiln for pretreatment to obtain calcined sand. The maximum temperature of the rotary kiln is controlled at 1000°C.

The heating heat source of the rotary kiln adopts coal with a calorific value of 5500kCal, such as bituminous coal or lignite. The fixed carbon content in the coal is 72wt%, the volatile matter is 16wt%, and the ash content is 12wt%.

The obtained calcined sand is sent and charged into the submerged thermal electric furnace, and the temperature of the calcined sand leaving the rotary kiln at the kiln head is controlled at 800°C.

Finally, the smelting treatment is carried out in the submerged electric furnace, the temperature in the submerged electric furnace is controlled at 1550±50°C, the content of FeO in the slag is controlled at 0.55wt%, and the mass ratio of the ternary basicity (MgO+CaO) and (SiO ₂ ) is controlled as 0.6, and the Cr ₂ O ₃ content in the slag is controlled to 0.12wt%.

Table 1 lateritic nickel ore main component (dry basis) (wt%)

Element SiO ₂ MgO MnO CaO Al ₂ O ₃ TF Cr ₂ O ₃ Ni content 36.74 15.64 0.67 2.32 4.94 14.47 0.71 1.85

Table 2 Main components of chromium salt chromium slag (wt%)

Element SiO ₂ MgO CaO Al ₂ O ₃ TF Cr ₂ O ₃ content 10.17 22.33 30.02 5.74 6.61 4.66

The composition of ferronickel after smelting is shown in Table 3, and the composition of slag is shown in Table 4. It can be seen that, by the method _of the present invention, the _Cr2O3 content in the chromium salt chromium slag is reduced from 4.66% to 0.12 _% in the smelting iron slag, and the remaining trace chromium is also solidified in the slag with stable _Cr2O3 , and at the same time The Cr content in nickel-chromium iron water reaches 2.8%. Therefore, without affecting the normal production of ferronickel, the present invention not only enables the co-disposal of hazardous waste chromium salt chromium slag, but also turns Cr element waste into treasure to obtain molten nickel-chromium iron, realizing resource utilization.

Table 3 Main components of nickel-chromium pig iron smelted with laterite nickel ore and chromium slag (wt%)

Element Fe C Ni Cr S P Si content 82.1 2.5 10.5 2.8 0.10 0.03 0.9

Table 4 Main components of nickel-chromium pig iron smelting slag with laterite nickel ore mixed with chromium slag (wt%)

Element FeO Cr ₂ O ₃ S SiO ₂ Al ₂ O ₃ CaO MgO content 0.55 0.12 0.04 56.62 8.16 7.32 26.67

Example 2

The smelting equipment in this embodiment adopts a sintering machine-submerged thermal electric furnace, and the rated power of the submerged thermal electric furnace is 15000kVA.

Raw material used in this embodiment and its composition: laterite nickel ore composition and service condition are identical with embodiment 1; The undried laterite nickel ore contains about 30% physical water in its natural state. It is sent to a drum drying kiln for drying to remove the physical water. The dry basis composition of laterite nickel ore is shown in Table 1.

Raw material ratio in this embodiment: the quality of stainless steel slag accounts for 5% of the dry basis of the laterite nickel ore; the powdered coal accounts for 15% of the total mass of the stainless steel slag and the dry basis of the laterite nickel ore.

Send the prepared smelting raw materials into the sintering machine for sintering pretreatment to obtain sintered ore. The heating source of the sintering machine is pulverized coal with a calorific value of 5500kCal, such as bituminous coal or lignite. The fixed carbon content in coal is 72wt%. Part 16wt%, ash 12wt%.

The cooled sinter enters the submerged electric furnace after screening. The temperature in the submerged electric furnace is controlled at 1550±50°C, the content of FeO in the slag is controlled at 0.35%, and the mass ratio of ternary alkalinity (MgO+CaO) to (SiO ₂ ) is 0.65, and the Cr ₂ O ₃ content in the slag is 0.13wt%.

The main component (wt%) of table 5 stainless steel slag

Element SiO ₂ Cr ₂ O ₃ CaO _{Fe2O3 _} Al ₂ O ₃ MnO MgO content 26.9 2.8 51.9 3.6 5.3 0.4 8.7

It can be seen that by the method _of the present invention, the _Cr2O3 content in the chromium salt chromium slag is reduced from 2.8% to 0.13% _of that in the smelting iron slag, and the remaining trace chromium is also solidified in the slag with stable _Cr2O3 , and at the same time The Cr content in nickel-chromium iron water reaches 3.5%. Therefore, without affecting the normal production of ferronickel, the present invention not only enables co-disposal of hazardous waste chromium salt and chromium slag, but also turns Cr element from waste into treasure and realizes resource utilization.

Table 6 Main components of nickel-chromium pig iron smelted with laterite ore and stainless steel slag (wt%)

Element Fe C Ni Cr S P Si content 81.9 2.6 10.4 3.5 0.12 0.028 0.85

Table 7 Main components of nickel-chromium pig iron smelting slag mixed with laterite ore and stainless steel slag (wt%)

Element FeO Cr ₂ O ₃ S SiO ₂ Al ₂ O ₃ CaO MgO content 0.35 0.13 0.05 54.25 8.53 10.56 24.67

To sum up, the embodiment of the present invention provides a method for co-processing chromium slag in smelting laterite-nickel ore in a submerged heat electric furnace, which not only realizes the detoxification of chromium slag, but also turns chromium into treasure and improves the economic benefits of the enterprise. Improve the efficiency of my country's comprehensive treatment of hazardous waste.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention.

Claims (10)

1. a method for chromium slag is put in the coexistence of ore-smelting furnace smelting red clay nickel ore, comprises the steps:

1) allocate in red soil nickel ore butt by chromium slag, chromium slag mixes with the proportioning of red soil nickel ore butt according to 1 ~ 5wt%, then add account for total mass 5 ~ 20% coal as reductive agent or fuel mix, obtain raw material to be smelted;

2) raw materials for metallurgy prepared is carried out pre-treatment, obtain calcining or agglomerate;

3) calcining pre-treatment obtained or agglomerate load in ore-smelting furnace to be smelted, to obtaining nickel chromium triangle molten iron while chromium residue detoxifying;

4) harmless slag is formed.

2. the method for chromium slag is put in ore-smelting furnace smelting red clay nickel ore according to claim 1 coexistence, it is characterized in that, described step 2) pretreatment technology comprises kiln process or sintering process.

3. the method for chromium slag is put in ore-smelting furnace smelting red clay nickel ore coexistence according to claim 2, it is characterized in that, described step 3) in smelting parameter in ore-smelting furnace comprise: in ore-smelting furnace smelting temperature control 1500 ~ 1650 DEG C, the slag ternary basicity content that controls FeO between 0.55 ~ 0.7, in slag controls at below 1wt%.

4. the method for chromium slag is put in ore-smelting furnace smelting red clay nickel ore coexistence according to claim 3, it is characterized in that, Cr in slag ₂o ₃below content 0.15wt%.

5. the method for chromium slag is put in ore-smelting furnace smelting red clay nickel ore according to claim 4 coexistence, it is characterized in that, when described pretreatment technology is kiln process, step 3) described in the calcining mode that loads ore-smelting furnace adopt the mode of hot delivery and hot charging.

6. the method for chromium slag is put in ore-smelting furnace smelting red clay nickel ore according to claim 4 coexistence, it is characterized in that, when described pretreatment technology is sintering process, step 3) described in agglomerate first cool rear screening after load ore-smelting furnace.

7. put the method for chromium slag according to the arbitrary described ore-smelting furnace smelting red clay nickel ore coexistence of claim 5 or 6, it is characterized in that, described chromium cinder ladle draws together chromic salts chromium slag, stainless steel slag, Stainless steelmaking dust and analogue thereof.

8. the method for chromium slag is put in ore-smelting furnace smelting red clay nickel ore according to claim 7 coexistence, it is characterized in that, described red soil nickel ore butt can adopt and be obtained cylinder kiln drying is dry by the red soil nickel ore of state of nature.

9. the method for chromium slag is put in ore-smelting furnace smelting red clay nickel ore coexistence according to claim 8, and it is characterized in that, the heat source of described rotary kiln and sinter machine adopts calorific value to be the coal of 5000 ~ 6000kCal.

10. the method for chromium slag is put in ore-smelting furnace smelting red clay nickel ore coexistence according to claim 9, and it is characterized in that, described coal comprises bituminous coal, brown coal.