RU2801974C1 - Method for removing zinc from zinc-containing electrometallurgical wastes - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: removal of zinc from the zinc-containing electrometallurgical wastes includes briquetting of wastes, heating them in a tube furnace reactor using hydrogen as a reducing agent, sublimation of zinc into the gas phase, cooling of exhaust gases and gaseous zinc. Waste briquetting is carried out together with coke dust in the amount of 10% and lignosulfonate (LST) binder in the amount of 3% by weight of the zinc-containing waste. Briquettes are heated in a tube furnace at a temperature of 800°C, holding time 4 h, furnace heating rate 20°C/min.

EFFECT: increased efficiency of extraction of zinc from waste, as well as iron content increase from 34.9 to 78.6%.

2 cl, 1 ex

Description

The invention relates to the field of metallurgy, in particular to methods for processing waste from metallurgical production, and can be used in the processing of zinc-containing dust from electric arc furnaces.

Waste class 4 includes sludge, which is formed in the furnace after steel smelting. The elemental composition of this type of dust contains oxides of various elements, and its structure is a fine powder. The result of this pollution is a negative impact on the health of the population, an increase in the incidence of the cardiovascular system, and a decrease in life expectancy. Today, this type of waste almost completely goes to dumps and sludge collectors. This is due to the high content of zinc in the composition of the sample.

Analogues of the developed technology can be divided into two categories: hydrometallurgical (leaching with the use of sulfuric acid or sodium hydroxide) and pyrometallurgical (dust treatment with the use of reducing agents at high temperatures). The efficiency of zinc removal by the hydrometallurgical method does not exceed 90%.

Pyrometallurgical processes, which also involve the use of reducing agents of various natures, can be classified as type 2 processes. As examples of processes of the second type, the Waelz process, as well as various foreign technologies, such as FASTMET, FASTMELT, Oxycup, PRIMUS, PaulWurth, etc., can be considered. The main principle of the processes under consideration is to conduct heat treatment at high temperatures, which is accompanied by the reduction of zinc-containing compounds with carbon , which is part of the charge, and subsequent sublimation of zinc, as well as the removal of vapors. These methods have a number of disadvantages that limit the possibility of application and wide implementation:

- significant specific consumption of the reducing agent

- high wear of the refractory lining of metallurgical units, caused by zinc sublimation processes

- change in the cross-section of pipelines caused by the processes of condensation of zinc vapors.

There is a known method for processing zinc-containing dust from electric arc furnaces (RU 2653394 C1, published on 05/08/2018), in which EAF dust is mixed with limestone in an amount that provides the addition of calcium oxide 70-110% of the content of iron oxide in the dust, and coke in the amount 1-2% by weight of dust. The mixture obtained is sent for pelletization to a plate granulator, into which water is supplied to ensure the moisture content of the granules is 12-14%. The pellets are loaded into the Waelz oven. Waelzation is carried out at a temperature in the reaction zone of 900-1000°C. Clinker is unloaded from the furnace with subsequent transportation to zinc leaching.

The disadvantages of this method are multi-stage, requiring further leaching of zinc; high consumption of calcium oxide in the amount of 70-110% of the content of iron oxide; process temperature reaching a value of 1000°C.

A known method for processing dust from metallurgical production (RU 2450065 C2, published on May 10, 2012). This process takes place in many stages, at the first stage the dust is agglomerated with the addition of a carbonaceous reducing agent, after which the agglomerated materials are dried. The samples obtained are heated and fired, and zinc is reduced and sublimated into the gas phase. When agglomerating dust, the material of the main composition with an MgO content of at least 70% is added to the charge; additionally, together with the agglomerated material, a carbon reducing agent is loaded into the furnace. Recovery roasting of the resulting briquettes is carried out at a temperature of 1200-1400°C.

The disadvantages of the known method are the high temperature of the process 1200-1400°C; multi-stage process, including dust agglomeration and drying of the obtained materials; high consumption of carbonaceous reducing agent.

The closest known technical solution to the claimed method is a method of dezincification and recovery (metallization) of iron oxide waste (RU 2240361 C2, published on November 20, 2004), including waste briquetting, heating them in a rotary tubular furnace using solid carbonaceous matter, afterburning furnace gases, cooling and dust collection containing zinc. To the zinc-containing mixture, carbon-containing crushed hard or brown coal is added, after which the resulting mixture is briquetted. The briquettes are fed into a once-through tube furnace heated from the loading side by oxy-fuel burners. Process temperature 800-1000°C.

The disadvantages of this method are the lack of binder additives in the manufacture of briquettes; incomplete removal of zinc; multi-stage process.

The claimed method for processing zinc-containing wastes from electrometallurgy has a number of advantages compared to existing analogues, in particular, a more complete removal of zinc with an efficiency of 99%, which is higher compared to hydrometallurgical methods, a lower process temperature not exceeding 800 ° C, which is significantly lower in terms of compared to similar technologies. Additional advantages of the process will be achieved due to the possibility of a single-stage implementation.

The technical objective of the invention is to increase the efficiency of extraction of zinc from waste, as well as to increase the iron content from 34.9% to 78.6%.

The technical result is achieved as follows.

The method for removing zinc from the composition of zinc-containing wastes of electrometallurgy includes briquetting of wastes, heating them in a tube furnace reactor using hydrogen as a reducing agent, sublimation of zinc into the gas phase, cooling of exhaust gases and gaseous zinc, and briquetting of wastes is carried out together with coke dust in an amount of 10% and binder LST (lignosulfonate) in an amount of 3% by weight of zinc-containing waste, and heating of briquettes in a tube furnace is carried out at a temperature of 800°C, holding time is 4 hours, the heating rate of the furnace is 20°C/min.

In addition, the diameter of the briquettes should not exceed 50 mm.

Humidity of hydrogen used for metallization of zinc-containing dusts of electric steelmaking should not exceed 2%.

The compressive strength of briquetted zinc-containing dust of electric steelmaking should be at least 3 MPa.

Humidity of the material in the manufacture of laboratory briquettes should be 13-14%.

Example.

They took 20 grams of zinc-containing waste, added 10% (2 g) of coke dust to it, 3% of the LST binder (0.6 g) was also added to the mixture. In the original sample, the Zn content is 17.5%, the Fe content is 34.9%. Water is added to the sample obtained, in the amount of 13% by weight of the sample (3 ml). At the next stage, briquetting is carried out on a hydraulic press, the compression pressure is 5 MPa. The diameter of the obtained briquettes is 3 cm. The briquetted sample is placed in a tube furnace reactor, which is continuously purged with a reducing gas, hydrogen. The hydrogen flow rate is 50 l/h. The temperature regime of the furnace is as follows: the heating rate is 20°C/min to 800°C, after which there is an exposure for 4 hours. Zinc that has passed into the gas phase, under the flow of the reductant gas, will enter the trapping system, which includes a water-cooled circuit in which further condensation of zinc occurs. In the reduced sample, the Zn content is 0% and the Fe content is 78%.

Claims (2)

1. A method for removing zinc from the composition of zinc-containing wastes of electrometallurgy, including briquetting of wastes, heating them in a tube furnace reactor using hydrogen as a reducing agent, sublimation of zinc into the gas phase, cooling of exhaust gases and gaseous zinc, characterized in that briquetting of wastes is carried out in conjunction with coke dust in an amount of 10% and a binder lignosulfonate (LST) in an amount of 3% by weight of zinc-containing waste, and the heating of briquettes in a tube furnace is carried out at a temperature of 800°C, holding time is 4 hours, the heating rate of the furnace is 20°C/min. 2. The method according to p. 1, characterized in that the diameter of the briquettes should not exceed 50 mm.