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Abstract

Содержание

Introduction

With the increasing market value of the fuel for Ukrainian industrial enterprises an important economic task is the reduction of natural gas consumption. First of all, it is important for the most energy-intensive industries country-industry. In a smelter problem arises mixing of various gases in order to obtain relevant thermophysical haraktekristik mixed gas and the full use of gases generated in the plant. The largest application received binary mixtures: koksodomennaya prirodnodomennaya mixture and mix.

Steam generators are used in the steel plants were designed to operate on natural gas. Now, however, due to the high price of fuel it replaces prirodnodomennoy mixture, which sometimes requires reduction in steam production units. If a plant is planned to switch to burning natural mixture. Need to study the effect of the percentage of low calorific fuels in the mix, as well as the impact that the percentage of content in the fuel mixture in the furnace gas zharoproizvoditelnost fuel mixture and the temperature of the flue gases at the outlet of the boiler furnace.

In this paper, we study the effect of the content of blast furnace gas prirodnodomenny mix served for combustion in boilers BKZ-75-39 FB installed on CHP-SA JSC "Donetsk Metallurgical Plant".

1. Theme urgency

One of the areas in the solution of this problem is the efficient use of secondary energy resources of their own, in including blast furnace gas. Inefficient use of blast furnace gas due to its low calorific value and high humidity. Work energy and technological units blast furnace gas is characterized by significant loss of heat from flue gases, chemical incomplete combustion and unstable burning torch. Problems with consumption of the blast furnace gas, it leads to the formation of excess resources in enterprises (12% from total output), the candles are burned.

Efficiency gas furnace can be increased by high-temperature heating gas and air in self-contained regenerative heaters with a bulk head. According to this, the actual practical task is the development of devices for high-temperature heating furnace gas and air, as well as process flow diagrams, enables collaboration of these devices with existing energy and technology units.

2. The influence of the chemical composition of the fuel on the emissivity of the combustion products

For the Ukrainian metallurgy important task is to reduce the consumption of natural gas in the first place, through the sustainable use of its own secondary fuel energy, particularly gas furnace. In the energy balance of metallurgical enterprises the share of blast furnace gas from the heat of 30-45%.ineffective the use of blast furnace gas due to its low calorific value and high humidity. combustion heat blast furnace gas, due to the presence of flammable components (dioxide СО, hydrogen Н and hydrocarbons СmHn) is 3150-3800 kJ/m3, and gas 33000-40000 kJ/m3. The disadvantage of the blast furnace gas is a high content of ballast in the form of nitrogen N2 = 46-69% and carbon dioxide СО2 = 7,5-20%. High humidity gas furnace (35-200 g/m3) complicates the conditions of its ignition and contributes to the formation of chemical incomplete combustion.Because of the small amount of hydrocarbon gas furnace torch almost missing pixel. The share of natural gas in the domain-domain mixture is determined by the formula;

Изменение степени черноты природно-доменной смеси газов с увеличением низшей теплоты сгорания смеси,
де Qнрпр -net calorific value of natural gas, MJ/m3; Qнрсм-net calorific value of natural gas mixtures blast, MJ/m3; Qнрд-net calorific value of blast furnace gas, MJ/m3. The calculations are given in the table.

Composition Table-natural-gas mixture domain
Qнр 8 10 12 14 16 18 20
Part of blast furnace gas 0,84384 0,77976 0,71569 0,65161 0,58753 0,52346 0,45938
Of the natural gas 0,15616 0,22024 0,28431 0,34839 0,41247 0,47654 0,54062

The emissivity of radiation of combustion products is the sum of the degrees of blackness RO2 = CO2 + SO2 і H2O, that is
Ег=ЕRO2 + B·EH2O,
and В-The correction coefficient of.

The figure shows the calculated curve E = E (Q), built to blast natural gas mixture at the combustion temperature 1100 ° C

Изменение степени черноты природно-доменной смеси газов   с увеличением низшей теплоты сгорания смеси

Figure 1 - Change of emissivity of natural-gas blast mixture with increasing lower the heat of combustion of the mixture

As a result of these calculations, we can conclude that with the increase of natural gas increases the amount of hydrocarbons in the mixture and hence flame lit brighter at the same time share the domain gas decreases, and decreases ballast incombustible component in the mixture. All this affects the increase in productive luminosity of the flame.

3. The use of blast furnace gas as fuel

In the blast furnace top gas output depends on the basic flow diagram of the process of production of pig iron, the type and scale of energy used in the furnaces, the composition of the charge materials and pig iron, capacity and structural features furnaces. The share of different processes in the total metal production is the main factor on which depend the blast furnace gas resources, and the extent of his participation in the energy balance of industrial enterprises.

So, to avoid burning natural gas, which is costly to have to burn large CHP of blast furnace gas, which are constantly changing. Efficient burning it with great difficulty. The fact that the combustion of blast furnace gas sharply changes his usual steam. Due to the low heat combustion of blast furnace gas (4000-4500 kJ/m3) high and inert ballast gas therein (56%, N2 и 14% СО2) steam temperature in the furnace is greatly reduced; in addition, the luminosity of the combustion products Blast furnace gas is low, all degrade the performance of the radiation heating surfaces. Increases the mass flow rate of flue gases through the steam generator at the same steam it increases the superheat steam temperature increases Flue gases are transferred exhaust fans, etc. A marked circumstances conventional steam generators steam when translated to the blast furnace gas is reduced to 70-75% rated.When co-combustion of blast furnace gas to another fuels, especially coal with low reactivity is significantly reduced efficiency steam. Of course, the possibility of increasing the efficiency of boilers fired by blast furnace gas, rises in recent times. One solution, for example, is a heating furnace gas. It is shown that the pre-heating furnace gas is an effective direction of increasing productivity CHP boilers for heating only blast furnace gas. Increasing the temperature of blast furnace gas per 100 °C will increase performance on 3,5-4%.

In this paper, we study the effect of the content of blast furnace gas in the natural domain mixture, which is used for burning in boilers BKZ-75-39 FB

4. Features of robots with a domain and natural gas

In this paper we assume the possibility of changing the characteristics of burning a mixture of natural gas and blast furnace. products Combustion of natural gas are high in water vapor. Their dew point, i.e. the temperature at which the Condensation of this vapor may be below 60 ° C. Therefore, the steel pipes in cold water may condense steam. In these conditions there is a gradual corrode metal moisture and carbon dioxide. To prevent this phenomenon is carried out thermal insulation of the lower part of the chimney. In addition, their status is periodically checked by inspection and tapping.

When the furnace or blast furnace gas to the combustion of a mixture of blast furnace and natural gas is necessary to monitor for gas pressure in gas boiler to regulatory dampers. Care should be taken that the gas and air evenly distributed to the burners, and that there was no thermal distortions in the furnace and flue pipes kotla.With co-firing blast furnace and natural gas to monitor the work of the furnace. In the case of blue flames in the area superheater, indicating poor performance furnace gas burners, it is necessary to adjust the flow domain gas and air on each burner. At the same load in the boiler supply increases the furnace top gas is grow and temperature of superheated steam. It is necessary to reduce it to a normal temperature.

Conclusion

Found that the closer the calorific value of natural-blast fuel mixture close to the heat of combustion blast furnace gas, the greater the influence of the heating temperature is on the final fuel combustion temperature at the outlet of the combustion chamber, and the heat of combustion of the fuel mixture at least 10 MJ /m3 is advisable to use pre-heating fuel.

In writing this essay master's work is not yet complete. Final completion: December 2013. Full text of the work and materials on the topic can be obtained from the author or his manager after that date.

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