Master DonNTU - Ageeva Julia I.

Theme of masters work:

"Investigation of the effectiveness of increasing the proportion of low-calorific blast furnace gas in thermal units of metallurgical enterprises"

Supervisor: Professor, Engineering Thermophysics, Ph.D. Kurbatov J L

Investigation of the effectiveness of increasing the proportion of low-calorific blast furnace gas in thermal units of metallurgical enterprises

The modern economy is characterized by high consumption of energy. One of the most energy-intensive production is ferrous metallurgy.

The energy component in the cost of production of pig iron up to 30%. This component consists of both energy resources is directly tied to the process of smelting iron (electricity, natural gas, blown into the furnace, blast furnace gas, burned in Blast Furnace), and energy resources coming from the (domain blast and thermal energy of steam supplied under the furnace throat). One way to reduce the cost of energy coming from the use of secondary energy for steel making. A secondary resource of metallurgical (blast furnace) production is the blast furnace gas. Blast furnace gas in its composition is combustible components in the form of SB 30%, 8% H2,% of other combustible gases. The composition and calorific blast furnace gas depends on the used in the production of raw materials, grades of coke, pig iron regime and other factors.

If we analyze the balance of receipt and use of blast furnace gas at the plant, it will be seen that the company has reserves of low-calorific fuel - blast furnace gas in the form of nonnormable losses at the candles. These losses can be used in the production cycle company for heat.

One of the main consumers of blast furnace gas at the plant is a CHP plant. At the CHP blast furnace gas is burned in boilers in conjunction with other fuel gases in order to obtain superheated steam.

The resulting steam is used to turbovozduhoduvnyh units for the blast for blast furnaces and as steam for technological needs of shops of the plant, particularly a blast furnace.

Boilers installed in CHP, is an aggregate average pressure with the classical U-shaped layout. Productivity boilers is 150t / h. The boilers are designed for the incineration of three types of gaseous fuels - natural, coke oven and blast furnace gas.

For disposal of surplus blast furnace gas received in the blast shop and reduce the cost of pig iron by reducing the energy costs of CHP boiler were carried out major repairs to reconstruction.

The reconstruction had been dismantled to separate burner combustion of various fuels and installed combined ploskofakelnye has changed form the bottom of the furnace - instead of cold funnel mounted horizontally under the screen. Alterations were screens, air ducts to the burners and gas pipelines. The work performed helped to increase the thermal fraction of blast furnace gas at 35,5%.

The main innovative idea of reconstruction of boilers for disposal of surplus blast furnace gas is the installation of combined ploskofakelnyh burners.

A method of burning fuel, which includes supply of gaseous fuel and oxidizer, education toplivnokislorodnogo stream, its offset relative to the longitudinal axis of the flux and twist around her, with the root flare stream is divided into inner and outer layers, which swirled in opposite directions.

This method is characterized by high chemical unburning fuel and high air flow caused by the slight path length of burning fuel, as a torch in the workspace firebox extends linearly.

Also known method of burning fuel in the form of a mixture of gases in the furnace of the boiler, including the filing of the furnace of the boiler with its opposite sides by two streams of dense gases flow into the furnace of the boiler by two parallel streams of low-calorie gas, perpendicular to the flow of dense gases, and supply flow with a corresponding decrease in air flow in the streams of air-fuel mixture. Burning a mixture of gases in this way reduces the size of the torch, the appearance of zones with low temperature on the cross section of the furnace, the deterioration of fuel combustion with an increase in the proportion of chemical unburning. This increases the rate of air flow to maintain the completeness of fuel combustion.

In ploskofakelnyh burners implemented method of burning a mixture of gases, including the filing of the furnace and boiler, two streams of low-calorie gas from its opposite sides and two streams - dense gases, and air flow into the furnace of boiler. Energy-dense gas is lower flows, which go up at an angle of 30 - 35 0 to the transverse axis of the furnace, and low-calorie gas is transferred from opposite sides of the furnace upper streams, which send down an angle of 30 - 35 0 to the transverse axis of the furnace, with air serving together streaming gases. This flow of gases and air curled in various directions, and their mixing occurs at the exit of the burner nozzle.

In the collision-gas streams directed at an angle to each other form a flat jet, which has a high degree of turbulence and large surface area, thus allowing for intense combustion of fuel in the entire volume of the furnace. At the same time by changing the cost of gas and air through the upper and lower streams can adjust the position of the torch vertical furnace. So if necessary, to reduce the position of the torch in the furnace increases the air supply through the upper streams and simultaneously decreases the air supply through the bottom. This zone is the nucleus of the torch is reduced and the redistribution of temperature fields on the cross section of the furnace.

Implementation of the proposed method provides a reduction in heat loss from the chemical unburning by improving the mixing of gases with the air, increasing the length of the combustion gases, increasing the degree of filling of the furnace torch, a reduction in the flow of air, which ultimately makes it possible to increase the efficiency of the boiler. When you use a boiler with sold as a useful model boiler efficiency increased from 78 to 86%.

Other things being equal (performance boiler, feed water flow rate, purge) the cost of thermal energy to the reconstruction amounted to 280.54 UAH / Gcal. After the reconstruction cost was equal to 148.50 UAH / Gcal. The difference amounts to 132.04 UAH / Gcal. The annual economic effect repair with reconstruction of burners in the annual operating hours of boiler 7900 hours of 10587.6 thousand UAH. The cost of repair with reconstruction burner is 18,746 thousand UAH. Thus, the payback period of capital repair is 1,8 years.

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