RU2667566C1 - Method of preparation of galvanic sludge for its utilization - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to the preparation of galvanic sludge – hydroxides of heavy metals, which are formed during the purification of waste waters of galvanic areas, for their subsequent disposal. Galvanic sludge is mixed in the reactor with a reducing agent of oxidized metals. Prior to mixing, dewatering of galvanic sludge is carried out on vacuum filters or filter presses. It is stirred at the normal temperature for 20–25 minutes. As the reducing agent waste of technical carbon is used, which is introduced in the preparation of galvanic sludge in the amount of 15–100 % of the dry matter of galvanic sludge. At the same time, 80–100 % of the dehydrated galvanic sludge is fed to the reactor before loading of carbon black waste, and the carbon black waste during the mixing time is introduced in three parts – immediately after the loading of carbon black, 5–10 minutes from the beginning of mixing and then after 5–10 min at the stopped agitator.

EFFECT: method provides for the reduction of oxidized metals and their recovery for reuse.

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Description

The invention relates to the field of preparation of galvanic sludge-hydroxides of heavy metals generated during wastewater treatment of galvanic sections, for subsequent disposal.

The problem of disposal of galvanic sludge is an interdisciplinary one, since galvanic shops and sites are available at most large enterprises, but it is most pronounced in mechanical engineering, where a wide range of galvanic operations (pickling, chromium plating, nickel plating, zinc plating, copper plating, etc.) are widely used. going for cleaning in various ways give rise to a difference in the quantitative and qualitative composition of galvanic sludge for heavy metal ions.

But even in the presence of landfills, the disposal of galvanic sludge is not rational, since they consist of compounds possessing valuable properties related to exhaustible natural resources.

A known method of preparing galvanic sludge for agglomeration and disposal [A.S. 1581758 USSR, IPC С22В 1/00. A method of preparing sludge for agglomeration. [Bull. Discoveries. Inventions 1990.28. S. 118]. It is based on the use of lime waste and the implementation of the process of extinguishing it due to moisture sludge.

The disadvantages and bottlenecks of the method can be noted the possibility of its use for preparing sludge for disposal only with limited humidity (not more than 15-20%), due to the excessively high costs of expensive lime and the unsuitability of the resulting composite for the subsequent heat-reduction process of galvanic sludge compounds to metals , while the actual humidity of galvanic sludge after dehydration is not less than 45%.

A known method of preparing sludge for agglomeration [Application No. 98122482/02 of 12/15/98. IPC S22I 1/14, C02F 11/14. A method of preparing sludge for agglomeration]. It differs from the previous method in that air-dry peat is used as a moisture-absorbing agent. According to this method, the process is carried out under stirring with the supply of sludge to peat, taken in an amount of 50-80% of the moisture content of the sludge.

However, the indicated peat consumption in excess of 50% of the sludge moisture value reduces the practical significance of the project due to the need to use significant quantities of exhaustible natural raw materials in an unconventional direction.

Closest to the claimed is a method of preparing galvanic sludge for agglomeration and disposal. [RF patent No. 2535110. Published December 10, 2014 Bull. Number 34. IPC С22В 7/00 (2006.01) С22В 5/04 (2006.01)] The process is carried out under conditions of mixing the components taken in the ratio: 0.43 mass accounted for the single-mass fraction of sludge. fractions of cassiterite concentrate (36% SnO), 0.49 mass. fractions of coal, 0.49 mass. fractions of sodium carbonate, 0.3 mass. fraction of sodium chloride.

However, the method (prototype) has a number of significant drawbacks: 1) All components of the resulting mixture are scarce and expensive materials; 2) Their dosage is taken based on one mass fraction of sludge, which indicates the need for large quantities of all components currently used in other traditional areas; 3) The significant particle sizes of cassiterite concentrate and coal compared with galvanic sludge hydroxide nanoparticles do not provide close contact between the interaction surfaces during the heat-reduction process of oxidized metals; 4) The process is conducted at high temperature for a long time.

The objective of the present invention is to reduce the scarcity, cost and reduce the time of preparation of galvanic sludge for utilization due to the use of large-tonnage, readily available production wastes, which are fine carbon black waste, to recover heavy metal ions contained in them.

This object is achieved by the fact that the proposed method of preparing galvanic sludge for disposal, including mixing the galvanic sludge in the reactor with a reducing agent of oxidized metals. Before mixing, dehydration of the galvanic sludge is carried out on vacuum or press filters, after which the mixing is carried out at normal temperature for 20-25 minutes, while carbon black waste, which is introduced in the preparation of galvanic sludge in the amount of 15-100% of the dry substance of galvanic sludge, is reduced as a reducing agent In this case, 80-100% of dehydrated galvanic sludge is fed into the reactor before loading carbon black waste, and carbon black waste is introduced in three parts during mixing - immediately after loading carbon, after 5-10 minutes from the start of mixing and then after 5-10 minutes with the stirrer stopped. This results in a homogeneous, free-flowing or thixotropic, non-dusting composite.

Studies on the formation of granular or thixotropic composite agglomerate from dehydrated galvanic sludge were carried out in laboratory conditions. As a unit for mixing, a homogenizer with a volume of 1.5 dm ³ with a mixer was used (rotation speed 100 rpm).

At the mixer rotation speed of 20 revolutions per minute, the entire galvanic sludge was loaded into the homogenizer, after which the rotation speed of the mixer increased to 100 revolutions per minute. At the time of the first third of the total carbon black waste, the mixer stopped, and after loading, the rotation speed increased to 100 rpm and was maintained until the second load in 5-10 minutes after the first was fully completed. In the same way, the third portion was loaded after 10-15 minutes with the stirrer stopped. The total mixing time at 100 rpm was 20-25 minutes, not counting the time to load the carbon black waste.

The resulting composite was discharged into a container. Depending on the dosage of carbon black waste within 15-100% of the dry matter of the galvanic sludge, the composite was a loose or thixotropic mass. Achieving the maximum degree of homogeneity of the composite structure over a specified mixing time was determined analytically by determining the minimum spread of cation concentration in samples taken in different microvolumes of the obtained composite.

The composite is suitable for subsequent thermal recovery utilization as an additive in the metallurgical charge, depending on the cationic composition of the galvanic sludge.

The method includes dewatering galvanic sludge on vacuum or press filters (performed by the owners of galvanic sludge) and mixing it in a reactor with a stirrer with carbon black waste, ensuring the recovery of oxidizing metals and their return for reuse [Waste of carbon black formed during its production (Federal Waste classification catalog - FKKO, Code 3.12.112.91.29.3 “Estimated technical carbon in its production”), carbon black waste in its preparation for production new mixtures (FKKO, Code 3.31.055.12.40.4), carbon black waste in the form of dust in the manufacture of rubber compounds (FKKO, Code 3.31.115.11.42.4), carbon black dust during gas cleaning in the production of rubber mixtures (FKKO, Code 3.31.713.11 .42.4)].

The resulting homogeneous, non-dusting composite is suitable for further heat treatment with the reduction of oxidized galvanic sludge metals.

Millions of tons of annually generated non-utilizable galvanic sludge containing toxic heavy metals pose a threat to the population due to their uncontrolled distribution across regions that do not have landfills that comply with SNiP 2.01.28-85 and SanPiN 2.1.7.1322-03 “Hygienic requirements for placement and disposal production and consumption waste

At the same time, the solution to the problem of the disposal of galvanic sludge is associated with the social effect of improving the human environment and the economic effect of the absence of the enormous costs for the construction of landfills - repositories that are environmentally hazardous, saving of natural resources due to the transformation of galvanic sludge into a product demanded by society - recovered metals. In essence, the galvanic sludge dry residue is an agglomerate - a mixture of various ores, which must be prepared in the least expensive way for a heat recovery process. At the request of sanitary rules and norms, the owner of the waste - galvanic sludge is obliged to dehydrate them, turning them into paste, that is, the owner of the galvanic sludge must have a vacuum or press filter. Unfortunately, the disposal of galvanic sludge was not widespread, since the proposed technologies were very complex and costly, which forced the owners of this type of waste to look for workarounds.

Claims (1)

A method of preparing galvanic sludge for disposal, including mixing the galvanic sludge in a reactor with an oxidized metal reductant, characterized in that before mixing the dehydrated galvanic sludge is dehydrated using vacuum or pressure filters, after which the mixing is carried out at normal temperature for 20-25 minutes, while as a reducing agent use carbon black waste, which is introduced in the preparation of galvanic sludge in an amount of 15-100% of the dry matter of the galvanic sludge, while 80-100% of dehydrated galvanic sludge they are fed into the reactor before loading the carbon black waste, and the carbon black waste is introduced in three parts during mixing — immediately after loading the carbon black, 5-10 minutes from the start of mixing and then after 5-10 minutes with the mixer stopped.