Dust disposal in electric arc furnace

Contents

contents

DESIGN ASSIGNMENT

PAPER

LIST OF GRAPHIC DOCUMENT SHEETS

INTRODUCTION

1. OVERVIEW OF LITERARY SOURCES

2. PROCESS PART

2.1. Description of smelting technology

2.1.1. General description of arc furnace

2.1.2. Charge materials

2.1.3. Steel smelting in main furnace

3. DESIGN PART

3.1. Screw Conveyor Screw Calculation

3.2. Calculation of screw conveyor drive

3.3. Vertical Screw Conveyor Screw Calculation

4. SAFETY OF LIFE

4.1. Microclimate

4.2. Dust and gas protection

4.3. Production noise

4.4. Production vibration

4.5. Radiation protection

4.6. Production lighting

4.7. Safety precautions

4.8. Electrical safety

4.9. Fire safety

4.10. Lifting and transportation works

4.11. Civil defense

5. ENVIRONMENTAL MANAGEMENT AND ENVIRONMENTAL MANAGEMENT

6. ECONOMIC PART

6.1. Capital Cost Calculation

6.2. Lost profit of the enterprise

6.3. Calculation of actual working time

6.4. Demand Program Calculation

6.5. Calculation of the number of workers and wages

6.6. Calculation of planned cost of production

6.7. Profit calculation

6.8. Calculation of notional-annual savings

6.9. Product profitability calculation

6.10. Payback Period

CONCLUSION

BIBLIOGRAPHIC LIST

Paper

The explanatory note contains 106 pages, 30 pages, 22 tables, 16 Fig.

The present work includes an overview of the methods of dust disposal in various industries according to literature sources, the selection of the most optimal method of processing dust-like materials, as well as the development of the design of the electric arc plant. Performed: calculation of the capacity of the screw conveyor, the speed of the screw screw, the drives of the conveyors and their individual elements are calculated.,

Introduction

Iron losses in blast furnace production with pile dust and sludge are up to 70 kg/t of cast iron. Given the raw material value of these wastes, it is appropriate and relevant to return them to technological limits, as a result of which the economic situation in enterprises and the environment as a whole improves.

Waste management is important not only in terms of its use as an alternative source of raw materials, but also in terms of environmental protection.

All this sharply increased the relevance of the problem of the complex utilization of blast furnace sludge and dust, the transition to waste-free metallurgical production schemes.

The most acceptable not only from an environmental point of view, but also from an economic point of view is the disposal of waste in-house, as this allows them to be used in the form of relatively cheap raw materials, which contributes to a significant reduction in charge costs, an increase in the quality and competitiveness of products, and most importantly, a decrease in the cost of finished products.

The main purpose of the work is to select and calculate the equipment of the electric arc plant for organizing the resource-saving technology of blast furnace production .

The novelty lies in the fact that the work proposes a universal scheme for processing pulverized materials from blast furnace wastes with the aim of their subsequent processing at the plant.

The main objectives of the work are as follows:

- to consider the main methods of dust disposal, their peculiarities.

- Develop a process line for processing iron-containing waste

- to determine the environmental economic effect based on the recycling of blast furnace dust.

Process Section

2.1. Description of smelting technology

2.1.1. General description of electric arc unit

Arc furnace consists of working space (furnace itself) with electrodes and current leads and mechanisms ensuring furnace inclination, retention and movement of electrodes.

Steel is melted in working space limited from above by domed arch, from below by spherical hearth and from sides by walls. Refractory masonry of hearth and walls is enclosed in metal casing. Removable vault is assembled of refractory bricks resting on support ring. Through three holes symmetrically located in the arch, current-conducting electrodes are introduced into the working space, which can move up and down using special mechanisms. The furnace is powered by three-phase current.

Charge materials are loaded on the furnaces, after they are melted, a layer of metal and slag is formed in the furnace. Melting and heating is carried out due to heat of electric arcs occurring between electrodes and liquid metal or metal charge.

Ready steel and slag are discharged through steel outlet and trough by inclination of working space. The operating window closed by the shutter is designed to monitor the progress of melting, repair of the hearth and loading of materials.

2.1.2. Charge materials

The main component of the charge (75-100%) of electric smelting is steel scrap. Scrap shall not contain non-ferrous metals and shall have a minimum amount of nickel and copper; preferably, the phosphorus content of the scrap does not exceed 0.05%. with a higher phosphorus content, the melting time increases. Scrap should not be highly oxidized (rusty). With rust (iron oxide hydrate), a lot of hydrogen is introduced into the metal. Scrap must be heavy-weight so that the charge is loaded in one take (one badge). With lightweight scrap, after partially melting the first portion of the charge, it is necessary to reopen the furnace and plant the charge, which increases the melting time.

Recently, the use of metallized pellets and sponge iron, products of direct reduction of enriched iron ores, has been expanding. They contain 85-93% Fe, the main impurities are iron oxides, SiO2 and Al2O3. A distinctive feature of this raw material is the presence of carbon from 0.2-0.5 to 2% and a very low content of sulfur, phosphorus, nickel, copper and other impurities usually found in steel scrap. This makes it possible to melt steel, which is distinguished by increased purity from impurities. Remelting the waste of alloyed steels saves expensive ferroalloys. These wastes are sorted by chemical composition and used in smelting steels containing the same alloying elements as wastes.

To increase the carbon content in the charge, cast iron, coke and electrode scrap are used. The main requirement for cast iron is the minimum content of phosphorus, therefore, in order not to add a lot of phosphorus to the charge of small (< 40 tons) furnaces no more than 10% of cast iron, and in heavy trucks no more than 25%.

Lime, limestone, melting spar, bauxite, chamotte battle are used as slag-forming in the main furnaces; in acidic furnaces - quartz sand, chamotte battle, lime. Iron ore, rolling scale, agglomerate, iron pellets and oxygen gas are used as oxidizing agents. Slag-forming and oxidizing agents are subject to the same requirements as in other steelmaking processes: lime must not contain more than 90% CaO, less than 2% SiO2, less than 0.1% S and be freshly equipped so as not to introduce hydrogen into the metal. Iron ore should contain less than 8% SiO2 because it reduces the basicity of slag, less than 0.05% S and less than 0.2% P; it is desirable to use ore with a size of 40-100 mm, since such pieces easily pass through the slag layer and directly react with metal. In the smelting spar used for slag liquefaction, the CaF2 content should exceed 85%.

In the electric steel smelting industry, almost all known ferroalloys and alloying alloys are used for doping and deoxidation.

Environmental management and protection

5.1. Introduction

The high energy intensity of metallurgical industries with a constant increase in prices for fuel and energy resources puts the problems of resource energy conservation at the forefront.

The efficiency of energy and resource consumption is characterized by technical re-equipment of production, the use of energy-saving technologies, as well as the use of secondary raw materials.

The following are identified as priority areas in the system of use of secondary resources:

- Negotiable use;

- restoration of secondary materials;

- Restriction of the formation and safe deposit of waste for the environment and human beings.

The key principles of clean production are resource conservation, recycling of waste, reduction of emissions into the atmosphere. Recycling is one of the priority principles of organizing environmental protection in metallurgy. Recycling is a system that allows you to cope with large material flows and related environmental impacts. It helps to achieve stabilization and improve the environmental situation with an increase in production volumes. The improvement of the environmental situation consists in the creation and development of low-waste and waste-free technological processes and industries, in the processing of waste, as well as in the neutralization and safe disposal of unused waste. [8]

Non-waste technology is developing in four main areas:

- creation and implementation of fundamentally new processes of production on the basis of complex processing of raw materials with extraction and use of all valuable components and maximum possible use of potential of energy resources. At the same time, waste generation and negative impact on the environment are significantly reduced or practically excluded;

- creation and implementation of various types of closed industrial water supply systems on the scale of individual industries, workshops, enterprises, industrial hubs and regions as a whole on the basis of existing, introduced and promising methods of wastewater treatment, their inclusion in the production water supply and non-use of surface and groundwater as fresh water sources; [7]

- development and development of territorial production complexes (TPK) having a closed structure of material flows of raw materials and secondary material resources. TPK create conditions for industry cooperation of production based on processing and recycling of secondary resources;

- Development and implementation of regional systems for decontamination and processing of all types of production and consumption wastes, which are considered as secondary material resources. [8]

The problem of pollution of cities and regions where metallurgical production is concentrated is of great complexity. The significant concentration of sources of harmful substances in metallurgical centers leads to such strong local pollution within a radius of 30-50 km from their source that metallurgical enterprises largely determine the pollution of these regions. A particularly high concentration of harmful substances is constantly recorded in the atmosphere of Novokuznetsk, Magnitogorsk, Nizhny Tagil. In Nizhny Tagil, the dysfunctional state of atmospheric air is determined primarily by emissions from such enterprises as the Nizhny Tagil Metallurgical Plant, Vysokogorsky Mining and Processing Plant, Uralkhimplast JSC, Uralvagonzavod NPK, Kotelnoradiator Plant. In the atmospheric air of the city, in addition to the main pollutants (carbon monoxide, sulfur dioxide, nitrogen dioxide, dust emissions of various chemical and particle size distribution), there are such pollutants as benzopyrene, formaldehyde, phenol, ammonia, carbon sulfide, hydrogen sulfide and volatile organic compounds. [4]

5.2. Environmental situation in the foundry of NTMK OJSC

The sources of emissions in the workshop are molding plants, two drying furnaces, waggons, an electric arc furnace, sand blasting chambers, chop separation, abrasive cutting and sandwiches.

The main emissions in the workshop that pollute the environment are emissions in the form of harmful gases and dust. During operation of electric furnaces and wagons, gases containing nitrogen dioxide, nitrogen oxide, sulfur dioxide, carbon dioxide are formed.

Mixing compartments are sources of quartz dust, sulphite liquor and sand.

When making molds and rods, toxic vapor-gas mixtures containing phenol, formaldehyde, furyl and methyl alcohols, ammonia, benzene, sulfuric acid vapors are released into the air medium.

Significant amounts of metal dust containing silica are formed in the chopping and casting compartment.

When working on sandwiches, abrasive dust and suspended substances are released.

5.3. Protection of the atmosphere from pollution

Natural and local plenum - exhaust ventilation is used in the shaped foundry shop. Contaminated and heated air is ejected outside through the upper aeration lights of the building. To eliminate dust releases, aspiration systems with an extensive network of air ducts and gas cleaning equipment are used.

Aspiration (dusting ventilation) is designed to remove dusted air from under the shelters of transport and technological equipment and the working area. Aspiration silos are cleaned of dust 2 times a year.

To ensure normal operating conditions in the area of the furnaces operation, local, air strangling and installation of mobile fans are used. To clean air from dust of mixing and molding and casting compartments, groups of cyclones of TsN15 grade, fans VDN12.5 and CPU 740 are installed, cleaned air enters the environment through a chimney. To clean electric furnaces gases, an umbrella with mechanical exhaust of gases is installed, which completely covers the furnace roof. After that, the gases enter the hose filter of the FRO600 model, in which the gases are cleaned. The sleeve filter consists of a welded, sheet casing, inside of which there is a system of filtering fabric hoses and an electric vibrator for shaking the hoses during their cleaning from dust. Cleaning is performed as dust accumulates in filters. The bag filter is also used to clean gases from annealing and drying furnaces. Cleaning of air from dust supplied from the knock-out grate is carried out through the UECHM gas flushing device, VDN12.5 fan, then through a candle, purified air is released into the atmosphere [7].

5.4. Protection of surface and groundwater from pollution.

The foundry is a water consumer, uses water from the city water supply for technical (cooling of the electric arc furnace, production of a molding mixture, dilution of non-stick coatings) and household needs. Drinking water is imported water.

To provide cooling water to the FLC electric arc furnace, a recirculation cycle using a settling tank is planned in the water supply system.

Heated water from the electric arc furnace is supplied for cooling to the fan cooling tower, from where it is again supplied to consumers by the pump. Make-up of the recycled system for replenishment of process losses and losses on the cooling tower is carried out by fresh technical water coming from the plant's CHP. The recycle cycle is blown by clarified water (after quartz anthracite filters) entering the industrial storm sewer, then to the pond blower . [4]

The contaminated water is clarified in a 4-section horizontal settling tank. Sludge removal from sumps takes place at dewatering site, after which sludge is supplied to disposal compartment, and water is returned to recycle cycle [7].

5.5. Solid waste

FLC solid waste includes slag, scale, mercury lamps, household and wood waste, oils, waste refractories.

During the operation and repair of metallurgical furnaces, refractory scrap is formed, which is a valuable secondary material resource. Such scrap includes parts of products from shamot, dinas, magnesite, suitable for reuse in the charge in the manufacture of new refractories.

Chemical waste is disposed of and disposed of at a special landfill for the centralized collection, disposal and disposal of toxic waste (mercury-containing, arsenic-containing inorganic solid waste).

The slag of electric furnaces is taken off and processed in the CPSH of NTMK OJSC.

Metal scrap usually goes to repeated redistribution, being the most important component of the charge of steelmaking furnaces.

Sand contaminated with oils is processed at TsPTO of NTMK OJSC.

5.6. Fuel-energy-raw material complex.

For more complete use of energy resources, it is customary to use the potential energy of various production wastes, which is not used in the main technological unit, but can be used to meet the need for energy in adjacent installations, heating systems and other processes of the national economy. This is the heat of combustion products, fuel, steam heat, hot water; heat transferred through furnace masonry, through walls of water-cooled elements, potential energy of electric arc furnace gases. To do this, various recuperators, regenerators are used. [8]

The following options are used for maximum heat utilization in the shaped foundry:

- passing the exhaust hot gases through the recovery boiler to produce steam;

hot gases are used to preheat scrap metal before loading into the furnace;

- organize heat transfer of hot gases to air or gas supplied to the combustion furnace (use of heat exchangers of regenerative and recuperative types).

5.7. Environmental validity of VKR

Increasing the level of use of secondary material and energy resources leads to a decrease in material and energy intensity of products, as well as savings in primary resources. Dumps and sludge accumulators have an extremely negative impact on the environment: there is dusting, pollution of soils and reservoirs, up to the complete disruption of landscape ecosystems. At the same time, enterprises incur significant costs for the maintenance of dumps, while losing valuable secondary raw materials.

This work proposes the design of an electric arc plant for the remelting of pulverized materials under the conditions of FLC of NTMK OJSC.

Work can be recognized as ecologically reasonable as represents a method of utilization of domain dust (composition of domain dust: Fe - 54%, SiO2 - 1%, Mn - 0.5%, Zn - 7%, CaO - 2%, MgO - 4%, S - 2%. Recycling of secondary resources is a priority in solving environmental problems.

Dust is melted in electric arc plant in volume of 20 tons per day, which allows to obtain 5 tons of cast iron. This is cost-effective (see economic rationale).

Conclusion

With the introduction of an electric arc installation for the remelting of pulverized materials in the FLC, there will be an increase in the cost savings of the enterprise due to the processing of secondary raw materials, as well as a decrease in costs for waste emissions and dumps.

With the use of an electric arc plant, the recycled use of blast furnace dust occurs - that is, the recycling of raw materials. It is also possible to note a decrease in the impact on the environment.

The introduction of this diploma project will increase production volumes and reduce the cost of production.

The introduction of the electric arc plant is economically profitable and expedient.