RU2372408C2 - Method of water recycling for steel degassing installations - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention elates to water recycling schemes and can be used in metallurgy. Method includes withdrawal of waste heated water from vacuum vessel into sedimentation tank, following filtration of settled water on filter plant, which is formed from pressure filters with granular filtering charging, grains diametre of which successively decreases top-down in the direction of flow of filtered water, and working pressure on inlet of which is kept at level 0.30-0.40 MPa at pressure difference on filter plant 0.04-0.12 MPa, after what filtrate is fed to cooling into cooling tower and then again to vacuum vessel. Additionally filters are in turn transferred into cleaning mode, at the first stage of which into filtering charging bottom-up it is fed compressed air, at the second stage bottom-up it is fed water.

EFFECT: at usage of invention it is provided increasing of effectiveness of steel degassing.

3 cl

Description

The invention relates to the field of water supply to heat exchange systems and can be used in metallurgy during water supply and cooling of technological equipment of steel vacuum installations.

The closest set of features to the claimed object is the prototype method of recycled water supply for steel vacuum installations, including the supply of source water to the vacuum of the steel vacuum installation, the discharge of heated wastewater from the vacuum tank to the sump, and the supply of settled purified water again to the vacuum tank ( Instructions and norms for technological design and technical and economic indicators of the energy sector of ferrous metallurgy enterprises. nological plants Sewage treatment plants and protection of water bodies -.. M., 1981. - T №14 -. P.44).

The proposed method of circulating water supply of vacuum systems of steel and prototype match the following essential features. Both methods include supplying the source water to the vacuum vessel of the steel evacuation unit, draining the waste heated water from the vacuum vessel to the sump, and supplying purified water as the source water again to the vacuum vessel.

Analysis of the technical properties of the prototype, due to its features, shows that the following reasons hinder the receipt of the expected technical result when using the prototype to provide recycled water supply to steel vacuum installations. The technological process of evacuation of steel is cyclical: within an hour, the operating time of the steel evacuation unit, which extracts harmful gases from the melt, is about 20 minutes. At the same time, the working medium of the vacuum degasser of the steel evacuation unit is saturated with harmful gases and a large amount of suspended solid particles with a size of mainly less than 1 μm. The calculated water flow rate to ensure the operability of one vacuum is quite high and amounts to 700-2200 m ³ / hour. Water heated to 50 ° C is discharged from the vacuum cleaner to the recycled water supply system for subsequent cooling and clarification in the sump. Wastewater from vacuum cleaners is characterized by the presence of very finely divided solid suspended particles in it, which makes it difficult to clarify it in sedimentation facilities. In the settled water, which is again fed to the degasser, the amount of suspended solids with a size of less than 1 μm is in the range of up to 100 mg / l, which negatively affects the operation of the degasser and reduces the efficiency of steel evacuation.

The claimed object is based on the task of creating such a method of circulating water supply for steel evacuation plants, in which an improvement by introducing new operations and operating conditions would allow using the method to achieve a technical result consisting in increasing the efficiency of steel evacuation.

The inventive method of circulating water supply for steel vacuum installations includes the supply of source water to the vacuum of the steel vacuum installation, the discharge of the heated heated water from the vacuum tank to the sump, and the supply of purified water as the source again to the vacuum tank. Before supplying purified water to a vacuum filter, it is filtered at a filter station, which is formed from pressure filters with a granular filter load, the grain diameter of which decreases from top to bottom in the direction of flow of filtered water. At the same time, the working pressure at the inlet of the filter station is maintained at 0.30-0.40 MPa with a pressure drop at the filter station of 0.04-0.12 MPa for the design capacity. After reaching the specified duration of the filtering cycle in the filtering process, the filters are switched to the cleaning mode one by one, in which compressed air is first supplied from the bottom to the top of the filtering stream against the direction of the filtered water flow to sparge granular filter material, and then water is supplied to wash the filtered solid particles. The filtrate obtained from the filter station is first fed to the cooling tower for cooling and then again to the vacuum degasser of the steel evacuation unit.

In particular cases of implementation of the claimed method is characterized by the following distinctive features from the prototype:

- as a granular filter load in the pressure filters of the filter station, a two-layer load of anthracite with a grain diameter of preferably 2.5-5.0 mm and silica sand with a grain diameter of preferably 1.0-1.8 mm is used;

- when cleaning each filter of the filter station, at the first stage, compressed air with an intensity of 10-14 l / (s · m ² ) per 1 m ^{2 of the} working area of the charge is fed from the bottom up for 10-15 minutes at the first stage, and then at the second stage for 10-15 minutes serves water with an intensity of 10-14 l / (s · m ² ) per 1 m ^{2 of the} working area of the load.

When using the claimed object, the achievement of a technical result is achieved, which consists in increasing the efficiency of evacuation of steel.

Between the set of essential features of the proposed method and the achieved technical result, there is the following cause-effect relationship. Filtration of the settled water before it is fed to the degasser using a filter station, which is formed from pressure filters with a granular filter load, the grain diameter of which decreases from top to down in the direction of the filtered water flow, and maintaining the working pressure at the inlet of the filter station at 0.30-0 , 40 MPa with a pressure drop at the filter station of 0.04-0.12 MPa for design performance provides filtering at higher speeds through the loading layer of a relatively high height When the filtered water flow direction from the load to the large grains finer grains. This prevents the formation of a surface layer of sediment with high resistance and helps to increase the retention capacity of the load when filtering water with very small suspended particles, less than 1 micron in size. The formation of a filter station from separate pressure filters allows, after reaching a predetermined duration of the filtering cycle in the filtering process, the filters alternately switch to the cleaning mode, while ensuring the constancy of the given filter station performance in the circulating water supply of steel vacuum installations and the given pressure drop at the filter station. The supply at the first stage of the compressed air purification regime to the filter charge from the bottom up to sparge granular filter material contributes to the separation of the filter load grains from conglomerates formed by these grains and very fine suspended particles deposited on them, as well as the preliminary separation of the deposited fine particles from the load grains. The subsequent supply of water under pressure at the second stage of the cleaning regime ensures the washing out of the filtered fine solid particles and the effective cleaning of the granular filter material from highly dispersed solid particles. At the same time, grains of filtering material suspended in an aqueous medium, due to different densities and different cross-sectional areas, are distributed over the loading height with a consequent decrease in their diameter from top to bottom. After stopping the supply of wash water, the grains of the filter material spontaneously precipitate with the formation of a granular filter charge, the grain diameter of which gradually decreases from top to down in the direction of flow of filtered water. This for a cleaned filter prevents the formation of a surface layer of sediment with high resistance and helps to increase the retention capacity of the load when filtering water with very small suspended particles less than 1 micron in size. The filtrate obtained from the filtering station is supplied to the cooling tower for a predetermined working pressure at the inlet of the filtering station and contributes to the further cooling of the filtrate and its degassing before being fed to the degasser. Thus, the quality of water, which is again supplied to the circulating water supply of the steel evacuation units, will be close to the quality of the initial water and the amount of suspended solids in it with a size of less than 1 μm will be significantly reduced, which will increase the efficiency of steel evacuation.

The indicated operating pressure range at the inlet of the filter station is 0.30-0.40 MPa, the differential pressure range at the filter station is 0.04-0.12 MPa for the design capacity, the preferred diameter of the grains of anthracite and quartz sand in a two-layer loading, the duration and the intensity of the air supply and water per 1 m ² area of the working load during purification phase of each filter filtering station determined experimentally and contribute to further enhance the filtering charge retention capacity etc. filtering the water with very fine suspended particles of less than 1 micron at higher speeds in vacuum water recycling installations of steel.

The method of circulating water supply of steel vacuum systems is as follows. To ensure the operability of the steel vacuum installations, the source chilled water is supplied to them. Hot contaminated water from the evacuators of the evacuation units via gravity pipelines enters the tank and is pumped to clarification in a radial sump. The clarified water after the radial sump is gravity-discharged through a pipeline and collected in the clarified water tank. Before supplying the settled water to the vacuum again, it is filtered at a filter station, which is formed from pressure filters with a granular filter load. In a specific example, in order to ensure the estimated productivity of reverse water supply for steel vacuum installations, for example 2100 m ³ / h, a filter station is formed of 10 parallel filters FN-3000M and FN-3400M with a capacity of 180 and 230 m ³ / h, respectively. Anthracite with a grain diameter of preferably 2.5 mm for the upper layer and silica sand with a grain diameter of preferably 1.8 mm for the lower layer are used as filter materials in these filters with two-layer loading. The height of the layers of anthracite and quartz sand is 1100 mm each. The diameter of the loading grains successively decreases from top to down in the direction of the flow of filtered water. The settled water is pumped to the filter station. The working pressure at the inlet of the filter station is maintained at 0.40 MPa with a pressure drop at the filter station of 0.05 MPa for design performance. The average filtration rate is 26 m / h. After reaching the specified duration of the filtering cycle in the filtering process, the filters are alternately switched to the cleaning mode. When cleaning each filter, at the first stage, compressed air with an intensity of 10 l / (s · m ² ) per 1 m ^{2 of the} working area of the charge is fed from the bottom to the top for 10 minutes at the first stage, and then at the second stage water is supplied for 10 minutes with an intensity of 10 l / (s · m ² ) per 1 m ^{2 of the} working area of the load.

At the same time, grains of filtering material suspended in an aqueous medium, due to different densities and different cross-sectional areas, are distributed over the loading height with a consequent decrease in their diameter from top to bottom. After stopping the supply of wash water, the grains of the filter material spontaneously precipitate with the formation of a granular filter charge, the grain diameter of which gradually decreases from top to down in the direction of flow of filtered water. The cleaned filter is again connected to the filter station, providing a given pressure drop at the filter station. The filtrate obtained from the filter station is first fed to the cooling tower for cooling and then pumped back to the vacuum degasser of the steel evacuation unit. The water purified in the filter station, which is supplied to the vacuum degasser of the steel evacuation unit, contains only 40 mg / l of solid suspended particles (instead of 100 mg / l), which improves the performance of the vacuum degasser and increases the efficiency of steel evacuation.

Claims (3)

1. The method of circulating water supply for steel vacuum installations, including the supply of source water to the vacuum of the steel vacuum installation, the discharge of spent heated water from the vacuum tank to the sump and the supply of purified water as the source again to the vacuum tank, characterized in that it is filtered before the purified water is fed to the vacuum tank at the filter station, which is formed from pressure filters with a granular filter load, the grain diameter of the material of which decreases from top to bottom in the flow direction water, while the working pressure at the inlet of the filter station is maintained at 0.30-0.40 MPa with a pressure drop of 0.04-0.12 MPa for the design capacity, and after reaching the specified duration of the filtering cycle in the filtering process, the filters are transferred one by one in the cleaning mode, in which at the first stage compressed air is supplied from the bottom to the top against the flow direction of the filtered water to bubble the granular filter material, then at the second stage water is supplied for washing about filtered solids, and the filtrate obtained from the filter station is initially first fed to the cooling tower for residual pressure and then fed back to the vacuum degasser of the steel evacuation unit. 2. The method according to claim 1, characterized in that as a granular filter load in the pressure filters of the filter station, a two-layer load of anthracite with a grain diameter of preferably 2.5-5.0 mm and silica sand with a grain diameter of preferably 1.0-1.8 mm. 3. The method according to claim 1, characterized in that when cleaning each filter of the filter station at the first stage, compressed air with an intensity of 10-14 l / (s · m ² ) is supplied from the bottom to the top for 10-15 minutes at the first stage 1 m ^{2 the} working area of the load, and then at the second stage for 10-15 minutes serves water with an intensity of 10-14 l / (s · m ² ) per 1 m ^{2 of the} working area of the load.