RU2031162C1 - Method for processing wastes of bimetallic composition of steel-bronze (copper) having open steel surface - Google Patents

Abstract

FIELD: metallurgy. SUBSTANCE: method involves solution of steel base, the process is carried out till steel content is 60-62 % of its initial value. Thus prepared residue is additionally mixed with fresh portion of wastes. EFFECT: improves efficiency of the method.

Description

 The invention relates to the field of metallurgy, in particular to hydrometallurgical methods for processing waste of a bimetallic composition, such as steel-bronze, steel-copper, with an open steel surface.

 Hydrometallurgical methods are known in which copper or a copper alloy is initially removed from the bimetallic compositions, and the steel base remains basically unchanged. Among them, a method of removing a cladding (tompak) layer from a steel-copper bimetallic composition (tompak) by treatment with an alkaline ammonia solution of carbon dioxide; copper or copper alloy dissolves with the formation of complex compounds of copper and zinc, which are removed from the process, the steel base remains unchanged.

 The disadvantages of this and similar methods are the high losses of non-ferrous metals associated with the need for independent technological redistribution for each non-ferrous metal (copper, zinc, tin, etc.), which is part of the copper alloy; environmental pollution of the process (ammonia emissions and wastewater); low commercial value of the steel product.

 There is also known a method of initial removal of a steel base from a steel-copper bimetallic composition (bronze, brass) by anodic treatment of the composition in an aqueous solution of inorganic acid salts with alkali metal or iron cations.

 The disadvantages of this method are: the complexity of the electrochemical process associated with the need to orient in the interelectrode space of the steel surface of the composition for the initial dissolution of steel (otherwise joint dissolution of steel and copper alloy occurs), the low corrosion rate of the steel base of the composition in a solution of iron salts without anode potential (example 5).

 As a prototype, a method of processing iron (steel) scrap (waste) into a yellow iron oxide pigment (iron oxide hydrate) having a high commercial value has been selected. The method consists in the corrosion dissolution of steel waste in a solution of iron sulfate, the acidic environment of which (pH 2.5-4.0) is supported by the hydrolytic decomposition of iron sulfate (+3) in the presence of atmospheric oxygen.

 The disadvantage of this method, used to remove the steel base from the steel-bronze bimetallic composition (copper), is the loss of copper (copper alloy), which dissolves when the steel base is removed (the copper layer loses tread protection).

 The objective of the invention is to reduce losses of non-ferrous metals, increasing the degree of iron removal of the bronze (copper) residue.

 The problem is solved in such a way that in the method of processing waste steel-bronze bimetallic composition (copper) with an open steel surface containing corrosive dissolution of a steel base in a solution of iron sulfate in the presence of oxygen (an oxidizing agent), the dissolution of the steel base is carried out before the steel content in the processed waste 60-62% of the original, and then sew up the residue with a fresh portion of the waste.

 The essence of the proposed method is as follows. Wastes (product rejects, die cutting, stamping, trimming, shavings) of the steel-bronze (copper) bimetallic composition are loaded into the reactor, where a solution of iron sulfate and oxygen (air) are supplied. There is an oxidation of iron sulfate; oxidized iron (Fe + 3) hydrolyzes at pH 2.2 or more with the release of free sulfuric acid, which is spent on the corrosion dissolution of the steel substrate of the bimetallic composition with the formation of a solution of iron sulfate. As the proportion of the steel base in the waste decreases to 60-62%, the reaction mixture is flashed with a fresh portion of the waste. If necessary, a pure bronze (copper) residue is separated on an electromagnetic separator with the return of iron-containing waste into the process.

With this method of conducting the process, the conditions for the tread (electrochemical) protection of copper (copper alloy) from oxidation by oxygen and dissolution by reactions are achieved:
4Cu + O ₂ = 2Cu ₂ O
Cu ₂ O + H ₂ SO ₄ = CuSO ₄ + Cu + H ₂ O
Cu + Fe (SO ₄ ) ₃ = CuSO ₄ + 2FeSO ₄
The tread protection of the bronze layer (the least conductive) is achieved by removing the steel layer to a distance of not more than 6-8 mm. Flashing with a fresh portion of the waste provides tread protection conditions. Moreover, the bronze (copper) layer does not oxidize, does not dissolve. The absence of an oxidized film on the surface of the bronze (copper) residue can improve its washing from a solution of iron sulfate and reduce the iron content in regenerated bronze (copper) to 0.3% (consumer requirement).

PRI me R 1. For the experiment using a bimetallic composition of steel grade 08Yu with a deposited layer of lead bronze (the content of Pb over 22 %%). 10 kg of die-cutting bimetallic plates 20 x 40 x 2.8 mm in size were loaded into the reactor; the thickness of the bronze layer was 0.5 mm. As used corrosive environment of ferrous sulfate solution (80 g / l FeSO ₄₎ through which air was blown at a rate of 12 l / min, with a solution temperature of 40-50 ^C. By the hydrolytic decomposition of iron sulfate (3) supports the necessary acidity solution (pH 3.0). The forming suspension of iron oxide hydrate was removed from the solution, and in return a clarified solution of iron sulfate was supplied. After removal of 38% by weight of steel, inspection and measurement of the residues of the bimetallic composition were performed. The bronze layer retained its geometric dimensions (plates 20 x 40 x 0.5), had a shiny surface. The steel base decreased in thickness to 1.2 mm and decreased in size, moving away from the edges of the plates by 6-8 mm. The bronze layer is provided with 100% tread protection (no loss).

 PRI me R 2. In the conditions of example 1 after dissolving 50 wt.% Steel and examining the samples revealed that the steel base has decreased in thickness to 1.0 mm and in size, moving away from the edges of the bronze plates by 8-9 mm. The corners of the bronze plates (size 20 x 40 x 0.5) were covered with a dark coating of copper oxide, that is, these places lost tread protection and began to dissolve (loss ≈ 1%).

 PRI me R 3 (according to the prototype method). In the conditions of example 1, after removing 100 wt.% Steel and examining the samples revealed that the steel base was completely dissolved. On the bronze plate, a shiny spot 8-10 mm in size from the last portion of the dissolved steel is visible. The edges of the bronze plate are slightly dissolved (loss of 3.5 wt.%), Covered with a dark coating of copper oxide. The washed and dried sample of the bronze residue showed the presence of 0.76% iron (iron reject).

 Example 4. In the conditions of example 1, after removal of 38 wt.% Of the steel, the residue was blasted with a fresh portion of the waste to the original amount of waste (10 kg). Two more times 38% of the mass of steel was dissolved and two times were freshly mixed with fresh portions of waste. After that, steel-bronze wastes were separated on an electromagnetic separator into ironed wastes that were returned to the reactor, and into a non-magnetic fraction of the bronze residue. The bronze residue was a shiny plate (size 20 x 40 x 0.5 mm) of bronze. The iron content in bronze was 0.27%. Bronze recovery 99.8%.

 PRI me R 5. In the conditions of example 4 were three processes with the removal of 40 wt. % steel. The extraction of the bronze residue was 99.6%, the iron content in bronze was 0.29%.

 PRI me R 6. In the conditions of example 4 were four processes with the removal each time of 30 wt.% Steel. The extraction of the bronze residue was 99.9%, the iron content in bronze was 0.26%.

 PRI me R 7. Used samples of a bimetallic composition in the form of scraps (marriage) of bimetallic pipes with an outer diameter of 43.5 mm, a height of 10-30 mm The wall thickness of carbon steel is 3 mm (st 50 GOST 1054-74), the thickness of the inner bronze layer is 1 mm. Tin bronze of the BrOF grade 6.5-1.5 (GOST 5017-74). The mass of waste is 10 kg. The conditions for the corrosion dissolution of the steel base are similar to those described in example 1. After dissolution, 28 wt. % of steel (determined by the amount of iron oxide hydrate extracted from the process) bimetallic waste was flashed with bimetallic shavings (formed when cutting bimetallic pipes) to the initial weight (10 kg). The hemming operation was repeated three more times. The remainder is separated on an electromagnetic separator. The magnetic fraction is returned to the process. The non-magnetic fraction was a shiny bronze residue in the form of pipe scraps (1 mm thick) and in the form of a powder (residue from chip dissolution). In the washed and dried bronze residue, the iron content did not exceed 0.3%. Extraction of bronze 99.6%.

 PRI me R 8. Used waste bimetallic composition in the form of trimming pipes with an outer diameter of 22 mm, a height of 5-40 mm with a wall thickness of 2.0 mm, the thickness of the inner copper layer of 0.7 mm For cladding, copper of the MZr brand (GOST 859-66) was used. The outer steel layer is st 10 (GOST 1050-74). The conditions for the corrosion dissolution of the outer steel wall are similar to those described in Example 1. After dissolving 40 wt.% Of the steel, a fresh batch of waste was ground. The trimming process was carried out two more times. The magnetic fraction is separated on the magnetic separator, which is returned to the process, and the non-magnetic fraction is separated - the copper residue in the form of shiny rings that retain the shape and dimensions of the clad copper layer. In the washed and dried copper residue, the iron content was 0.24%. Copper recovery 99.9%.

The proposed method is characterized by the following technical effectiveness:
loss of bronze (copper) is 0.1-0.4%;
the iron content in secondary bronze (copper) is 0.26-0.30%.

 To implement the proposed method, standard equipment is used - chemical protected reactors, filters, repulpators, electromagnetic separators, metering hoppers, turbo-gas blowers, a drying chamber, etc., as well as well-known technological methods: weighing, loading, dissolving, draining, filtering, washing, separation, drying, packing, chemical analysis.

 The industrial applicability of the method is not in doubt, which is confirmed by pilot tests of the method at the Dimitrovgrad auto-aggregate plant (PO AvtoVAZ).

 The method involves the separation of a bimetallic composition (steel-bronze, steel-copper waste) to produce two valuable products - a yellow iron oxide pigment (iron oxide hydrate) according to GOST 18172-80 and secondary bronze (copper) according to GOST 1639-78, cl. A. T. e. Low-quality non-ferrous metal waste class. L (bimetals) turn into high-quality materials with non-waste processing technology.

 The feasibility study of the process shows that in the processing of 1000 tons / year of steel-bronze waste (DAAZ), the recoupment of the costs for the development of production will be 2.3 years.

Claims (1)

 METHOD FOR PROCESSING WASTE OF THE BIMETAL METAL COMPOSITION STEEL - BRONZE (COPPER) WITH OPEN STEEL SURFACE, including the corrosion dissolution of the steel base in the solution of iron sulfate in the presence of oxygen (oxidizing agent), characterized in that the dissolution of the steel base is carried out to the content of steel 60 in the process - 60 % of the initial, after which the residue is bridged with a fresh portion of the waste.