RU2324525C1 - Method of hydroblasting of deviating blast-furnace gases - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: when applied, the method of hydroblasting of deviating blast-furnace gases includes deliverance of these gases inside the hydroblasting aggregate, their processing by means of finely-sprayed liquid via atomizer, removal of slime from the hydroblasting aggregate and passing of the purified gas into the network gas pipe line. Additionally, one must measure the gas' remaining dust content after having thoroughly cleaned it. The remaining moisture content should also be appropriately measured. For that purpose, with the aid of a selected tune one has to take a certain gas sample after it has passed via the hydroblasting aggregate. Then the gas' quantity has to be accurately determined and sent inside a dust and drop catcher. Thereafter one ought to measure the quantities of dust and moisture found in the measuring device set behind the dust and drop catcher. Then, depending upon the results obtained, one must regulate an amount of water to be delivered to the atomizers. The gas' quantity in the selected sample should be defined by way of aligning of the gas' static pressure in the network gas pipe line at the point of choosing. This should provide equality of the gas' speeds in the gas pipe line and the selected tube. Herewith, the indicators of a correlation of pressure must be reflected by the registering device. The gas' sample must be chosen on account of its pressure in the gas pipe line after it has been thoroughly cleaned.

EFFECT: increases in the quality of cleaning and saving of water.

3 cl, 1 dwg

Description

The invention relates to the metallurgical industry, in particular to methods for purifying exhaust blast furnace gases from dust and moisture.

There is a method of purification of exhaust gases by countercurrent supply of gases and milk of lime circulating in the absorber tank system and supplied to the absorber at different levels, spraying and absorbing harmful impurities from the gases, with lime milk supplying a certain amount of water to the upper tier of the absorber [1 ].

The disadvantage of this method is the lack of determination of solid particles of dust and moisture in the exhaust gas. The lack of moisture control makes it impossible to regulate the water supply, which leads to a decrease in the economic performance of the gas treatment plant.

Known closest to the proposed method of wet cleaning of gases, including the supply of gases to the device in the form of a spiral scroll, where they are treated with liquid sprayed by irrigators. As a result of spraying the liquid into the gas stream, a dust-gas mixture is formed, which is sent in a spiral along the cylindrical part of the body to the sludge outlet. Gases purified from dust are removed, and water in the form of sludge is removed [2].

The disadvantage of this method is the lack of control of solid particles of dust and moisture in the exhaust gas. According to the safety rules in the gas industry of metallurgical and coke chemical enterprises and industries, the dust content of blast furnace gas should not exceed 4 mg / m ³ . Lack of control does not allow fulfilling safety requirements for such toxic gas as blast furnace gas. The lack of dust control makes it impossible to regulate the water supply, which leads to a decrease in the economic performance of the gas treatment plant.

The objective of the invention is the possibility of its use both for determining dust and for determining the humidity of a gas stream, including toxic, under pressure, the possibility of implementing the method in a stationary installation.

The technical result achieved in the claimed invention is to improve the quality of treatment and save water supplied to the gas purification of blast furnace gas, by regulating its supply depending on the dust and moisture content in the exhaust gas.

The technical result consists in the fact that in the method for wet cleaning of exhaust blast furnace gases, which includes supplying gases to the cleaning unit, treating the gases sprayed with liquid through nozzles, removing sludge from the cleaning unit, removing the purified gas into the network gas pipeline, the residual dust content of the gas after cleaning is additionally measured at the same time and residual moisture, for which, using a selective tube, a specific gas sample is taken after the cleaning unit, its amount is determined and sent to a dust collector, after which measure the amount of dust and moisture in the measuring device installed after the dust collector, then, depending on the result, regulate the flow of water supplied to the nozzles. The amount of gas in the sample taken is determined by equalizing the static gas pressures in the sampling pipe and in an additional pipe, which is installed in the network gas pipeline at the sampling location to ensure equal gas velocities in the gas pipe and the sampling pipe, while the pressure ratio is displayed on a recording device. A gas sample is taken due to its pressure in the gas pipeline after purification.

The proposed method is implemented in a wet gas purification device (see drawing), which consists of two stages - a wet nozzle scrubber 1 and a Venturi pipe 4. In the scrubber 1 from the blast furnace bottom gas flows at a pressure of 0.2-0.3 MPa, temperature 250 -270 ° C and dust content of 10-30 g / m ³ . Irrigation water flows from above, sprayed upwards by nozzles 2 to create a larger volume of contact between dust particles and water drops. The flow rate of irrigation water to the scrubber 1 can be changed by valve B1. Contaminated water (sludge) accumulates in the lower part of the scrubber 1 and through the valve B2 is constantly discharged into the sewer channel to discharge it to the sump. The cleaned blast furnace gas, which has residual dust, drip moisture and one hundred percent humidity with a temperature of 50-70 ° C, passes through the throttle gas pipeline 6 through a throttle group or GUBT 14 to the blast furnace gas network 15. According to the technical conditions (according to the Safety Rules in the gas industry metallurgical and coke chemical enterprises and production) dust content of blast furnace gas should not exceed 4 mg / m ³ .

The degree of purification of blast furnace gas depends on the quantity and quality of spraying with nozzles of irrigation water. Moreover, deepening the cleaning below the established norm is associated with unjustified additional water costs and associated costs. In addition, excess moisture in a blast furnace gas reduces its quality as a fuel, reducing heat dissipation, which in turn leads to a deterioration in the quality of air heating in blast furnace heaters and a decrease in the productivity of blast furnaces themselves and excessive consumption of coke.

To optimize the operation regimes of blast furnace gas purification, it is required to control the residual dust content and humidity of the gas in order to ensure the minimum required flow rate of irrigation water without reducing the required quality of treatment.

The control of the residual dust content and humidity of the blast furnace gas after gas purification is based on sampling a certain amount of gas from the gas pipeline, followed by precipitation and measurement of moisture and dust in it. A gas sample due to pressure in the gas pipe 6 is taken by a tube 7 and sent to a cyclone type dust collector 12, where due to the outflow through the nozzle the gas lowers its temperature (up to negative values), which contributes to the condensation of moisture and its separation with dust from the stream. Condensate with dust flows down the walls of the dust collector 12 to the lower part, from where it is supplied through the valve B4 to the measuring device 13. In the measuring device 13, the weighted amount of dust and moisture is determined. From the dust collector 12, the sampled gas sample is discharged behind the throttle group or HUBT 14 into the network gas pipeline 15.

In order to more deeply condense the moisture from the sampled sample, a nozzle is installed at the outlet of the tube in the dust collector 12, which ensures, as a result of sudden expansion, a decrease in the temperature of the sampled gas to negative values.

Since the dust content of the gaseous medium should be attributed to a unit of its volume, a gas sample is taken with its known quantity.

The method for determining the amount of gas to be taken is based on balancing the gas velocity in the inlet of the sampling tube 7 with the gas velocity in the main gas pipeline 6, in which it is known, by the gas flow rate in it and its diameter. This method is known as isokinetic. The balancing of speeds is as follows.

Taken together, the tubes 7 and 8 represent a known pressure tube for determining the velocity (dynamic) head R _d , which can be measured by a differential pressure gauge 10 with closed valve B3, as the difference between the total pressure P _p and the static P _c , i.e. R _d = R _p -R _s , which will be reflected by the recording device 11. This velocity head is formed due to the gas velocity in the main gas pipeline and, in fact, displays it. The gas velocity in the input section of the selection tube will be equal to zero.

When valve B3 is opened, the gas sample is moved and taken through the sampling pipe 7 due to the pressure difference in the gas pipelines 6 and 15. In this case, the gas velocity in the inlet section of the sampling pipe increases, and the reading of device 11 decreases, since the pressure head R _d dust collector 12. By changing the flow rate of the sampled gas by valve B3, such a flow rate and, consequently, a gas velocity at which the reading of the device 11 will be equal to zero are achieved. This state corresponds to the fact that the gas velocity in the tube 7 becomes equal to the gas velocity in the gas pipeline 6 or, in other words, the difference in static pressures at the sampling point in the gas pipeline and the sampling tube at the point of connection of the impulse tube 9 will be zero. To ensure isokinetics inside the selection tube, its cross section from the sampling point to valve B3 is constant. The impulse tube 9 is connected to the selection tube 7 with the conditions of the requirements when measuring static pressure.

Regulation of water flow for gas purification of blast furnace gas is as follows.

Dust collection in a wet scrubber 1 is carried out by water droplets formed by nozzles. In this case, the more drops of water moisture falls on one particle of dust, the greater the likelihood of its capture by this drop and precipitation with it. Therefore, the amount of water supplied and the quality of its spray (droplet diameter) are determining parameters that affect the degree of gas purification. But at the same time, the initial dust content of the top gas and its consumption are those factors that also affect the degree of purification. And since residual dust is not controlled at gas purifications, the water flow to it is supplied with a margin of intuitive experience, which in turn leads to its unjustified overspending, inefficient use and additional costs.

The proposed method for controlling the residual dust content of a blast furnace gas allows, through valve B1, to adjust the water supply to the gas purification in such a way that its residual dust content, measured by the proposed method, is maintained.

The proposed method for wet cleaning of exhaust blast furnace gases has the following advantages:

- a device for implementing the method is simple in manufacture and installation;

- there are no scarce and expensive materials and equipment;

- allows you to separately determine the amount of dust, drip and steam moisture in the gas;

- reliable, as does not have flow meters;

- accurate, since due to the equality of velocities there are no distortions of velocity fields in the sampling section;

- It can be fully automated.

The proposed method allows you to simultaneously determine the dust and humidity of the exhaust gas stream, including toxic, under pressure, this method can be implemented in a stationary installation. The method allows to improve the quality of treatment and save water supplied to the gas purification of blast furnace gas, by regulating its supply depending on the content of dust and moisture in the exhaust gas.

Literature

1. Patent No. 2201791 "Method for purification of exhaust gases", IPC B01D 53/14, B01D 47/06, publ. 04/10/2003

2. Patent No. 2239487 “Device for the wet cleaning of gases”, IPC B01D 47/06, B04C 5/23, publ. November 10, 2004

Claims (3)

1. The method of wet cleaning of exhaust blast furnace gases, including the supply of gases to the purification unit, the treatment of gases sprayed with liquid through nozzles, the removal of sludge from the purification unit, the removal of purified gas into a network gas pipeline, characterized in that they also simultaneously measure the residual dust content of the gas after purification and residual moisture, for which, using a selective tube, a specific gas sample is taken after the cleaning unit, its amount is determined and sent to a dust collector, after which the amount of dust is measured and moisture in the measuring device installed after the dust collector, then, depending on the result, regulate the flow of water supplied to the nozzles. 2. The method according to claim 1, characterized in that the amount of gas in the sample is determined by equalizing the static gas pressures in the sampling pipe and in an additional pipe, which is installed in the network gas pipe at the sampling location to ensure equal gas velocities in the gas pipe and the sampling pipe, while the pressure ratio readings are output to a recording device. 3. The method according to claim 1, characterized in that the gas sample is taken due to its pressure in the gas pipeline after purification.