DonNTU   Masters' portal

Abstract

Content

Introduction

Domain technology since the operation of the first kiln paid serious attention to the process of combustion of fuels at the lances. The first studies of the combustion of coke in lances, as the VA Sorokin, refer to the 1838 One of the first (1841) description of processes in the lances made and J. Ebelman "the oxygen contained in the air is blown, it is rapidly converted into carbon dioxide, carbon monoxide, then, these two transformations are performed sequentially on a short distance of the lance ... ".

The most important area in the politics of energy and resources in iron smelting technology is the competition for savings of coke - the most expensive and scarce component of the domain of the charge. This policy reflects the development of promising technologies blast furnace due to the use of other fuels as substitutes for parts of coke, and about blast enriched with oxygen. This technology, known as applicationtion combined blast for the smelting of iron, is supported by the results of the blast furnaces in the last decades.

Combined called blast comprising additives in the form of oxidizing agents (oxygen, steam) and reducing (natural gas, coke oven gas, pulverized coal, fuel oil, etc.). The most commonly accepted combination of oxygen enrichment of the blast with the injection of natural gas or pulverized coal.

1. The purpose of the work and objectives of the study

The purpose of the evaluation is to determine the effectiveness of blast furnace technology using combined blast.

Objectives and methods:

  1. Analysis of published data.
  2. Calculation of indicators blast furnace.
  3. The study of factors affecting the combined blast.
  4. Establishment of the program, showing the dependence of the combined blast on various factors.
  5. Work on the study of the behavior of coke in the blast furnace tuyere zone at different ratios of the blast and the size of a piece of coke.

2. Features of theme and a brief analysis of the issue

2.1 General information about the combined blast

Combined blowing [combined blast] - hot, oxygen-enriched, for use with blown into the furnace gaseous, liquid or solid fuel additives or hot reducing gases. The term "combined blast", proposed by AN Ramm, became widespread only in the Russian technical literature. Oxygen enrichment of the blast air patented in 1876 by G. Bessemer. Widespread use it for melting pig iron became possible and feasible only by blowing into a blast furnace fuel additives, primarily natural gas (NG), which was first applied in 1957 by furnace number 4 of the plant. Petrovsky in Dnepropetrovsk. Enrichment of the blast with oxygen intensifies the combustion of fuel in a blast furnace and increases productivity by 2.5-3.5% for every additional 1% of the oxygen in the blast. Fuel additives are injected into the blast furnace coke to replace them. Coke substitution ratio fuel additives depending on their chemical composition and the carbon content of the coke and blast furnace on the conditions under which the fuel additives used and their flow. PG coke substitution ratio are 0.6-0.9 kg / (methane content in PG 93-96% in the coke and carbon 85-88%). Coke substitution ratio pulverized fuel strongly depend on the ash content and volatile vesch-in in an angle: 0.5-1.2 kg / kg. The injection of hot reducing gases has not yet found a permanent industrial applications. Since the 70's, in countries where the use of coal in blast furnaces economically profitable use of natural gas, more widespread pulverized coal injection (PCI). The achieved rate of pulverized coal in the blast furnace is 150-200 kg / t.

2.2 Conceptual framework of the combined blast in blast furnace.

In the blast furnace production of Ukraine combined blast has been used for over 50 years (since 1957). The technological concept of its implementation of the economic conditions of the former Soviet Union was that the mode is considered as the main way to intensify the process of saving and coke at the same time not to focus too much on the level of prices of coke or components combined blast - they were about the same throughout the USSR . The degree of enrichment of the blast with oxygen at a specific individual enterprise was determined, mainly, existing or planned capabilities for the balance of natural gas and process oxygen (the "oxygen"). When implementing a combined blast all used a single processing method - ensures the preservation of the theoretical combustion temperature by observing the constant ratio between the additional costs of natural gas and oxygen, equal to 0.65-0.70 m3/m3.

In current market conditions, with a significant increase in the cost of natural gas, oxygen and coke to the blast of the use of additives in the largest possible quantities are not consistent with the principle of profitability get rational functioning of a particular company, which provides a sufficient profitability and sustainability of production. In many cases, the use of combined blast of high parameters leads to a negative economic effect.

The essence of the new concept is that the use of natural gas and oxygen is limited, based on economic considerations, to obtain a well defined, predetermined in advance, the profitability of the enterprise, i.e. optimized efficiency combined blast to achieve appropriate profitability. This level of economic benefit can be designated as "rational effect of combined blast" (REKD). This figure is actually characterizes a minimum possible efficiency, which can provide the planned profitable operation of the enterprise. Proceeding from the measure REKD, efficient process conditions designed furnaces, primarily installed economical consumption of oxygen and natural gas in blast furnaces.

It should be emphasized that, with appropriate technical, economic and technological conditions and with the strategic development of the company it is possible to increase the level of oxygen enrichment of blast over the value determined REKD while suitably combined blast parameters increase.

3. The advantages of combined blast

Feasibility of injection into the blast furnace carbon-containing substances such as hydrocarbons, recognized in the last century. In 1838 Barnett proposed blown into a blast furnace gas containing hydrocarbons and resin. Then offered a blow oil and its products, coal dust, coal tar, coke oven, passing and natural (raw and converted) gases. However, the commercial development of fusion using extra fuel injected through lances, began in the 40s of this century in the Soviet Union. The experiments with the injection of pulverized coal into the furnace at the end of the 40s were held at the metallurgical plant them. Dzerzhinsky. From that time began a new kind of blast furnace process - on a combined blast.

The injection of natural gas into the furnace was a major technological undertaking that has brought significant benefits to the national economy of the USSR and has greatly intensified smelting. From the gas injection only during the years 1959-1966. the national economy of the USSR received 392 million rubles savings. The productivity of blast furnaces increased by 4 - 7%, coke consumption decreased by 7-14%. On a number of metallurgical enterprises have reached the natural gas flow of 140 m 3 / t of pig iron and above. Natural gas, as part of a combined blast and has the advantages that define its use in blast furnace technology. These advantages relative:

  1. simplicity and low cost technique for distribution of gas and injection lances in each tuyere;
  2. ease of controlling the flow of natural gas, whereby exposure is performed on the thermal state of the furnace, the temperature of combustion and the productivity of the blast furnace;
  3.  the ability to increase the concentration of hydrogen in the gas furnace attendant;
  4. purity gas from suspended impurities, contaminants serosoder containing gases component that provides low you move slag and sulfur coming into the blast furnace.

Injection of natural gas significantly changes the characteristics of the individual.

The problem of the application process oxygen in the domestic steel industry has become one of the most controversial in the last quarter of the last century. The use of oxygen in the domestic steel industry was due to the general course of economic development aimed at maximum intensification of blast furnace technology.

One advantage of using oxygen is that it forces blast furnace increases in intensity reduces harmful emissions into the environment.

The main disadvantages of the use of oxygen in the blast furnace is:

  1. its use is more expensive than the use of the hot blast;
  2. it reduces the heat coming from the blast;
  3. displays heated to a temperature of blowing nitrogen, thereby reducing the heat content.

At the moment, European businesses are trying to reduce the amount of oxygen used. Exceptions to the above may be some modes of production processes in which the use of process oxygen can change its temperature and thermal characteristics and a considerable saving scarce solid fuel. The sharp rise in energy consumption for the production of iron occurs when the volume content of oxygen in the blast furnace blowing in excess of 30%.

Therefore, special importance is the large-scale introduction of blast furnace smelting technology with injection into the furnace coal injection (PCI), prepared from a readily available and relatively inexpensive noncoking grades of coal with low sulfur and ash. Carbon advantages compared with other substitutes coke is its low cost, large stocks and high heat of combustion in the blast furnace tuyeres.

Currently pulverized coal as a component of combination bined blast furnaces ranked first, not only on the prevalence, but also in terms of application. For example, blast furnaces in Japan are using 35% of the world's coal fuel consumption, blast furnaces in China and Korea - 25%. The rest of the pulverized coal - about 40% consume blast furnaces in Europe, America and Australia. Stable expenses IFB at 150-200 kg / t of pig iron replacement provided 40-45% of coke.

In spite of some of the processes of preparation of pulverized coal, transport it to the furnaces and distribution lances, this kind of fuel additive is the most promotive. In most cases, the construction of new do main governmental ovens are oriented to be used as a fuel additive to a blast of pulverized coal.

Conclusion

Can be reasonably expected to argue that the combined blast in blast furnaces of Ukraine, even in conditions of a sharp rise in price of natural gas, oxygen, and other energy sources will be used in practice as a significant way to improve blast furnace performance. It is that by blowing gas along with the development of processes that provide immediate direct replacement of carbon-carbon coke gas, and the development in the recovery process FeO hydrogen significant technological advantages combined blast is to increase stability of operation of the furnace and its thermal state due to the significant increasing the hydrogen content in the blast furnace gas phase.

Increase in the price of coke acts positively on economic efficiency, while a similar increase in the cost of natural gas or process oxygen causes it to decline, with more than a rise in cost of coke - by about 25-40%, ie to maintain the efficiency rates of coke should be significantly increased in comparison with natural gas prices increase or technical oxygen. The formulas to determine the limit price of natural gas or oxygen-dependent primarily on the values ??of rates of coke and replacement rate.

The analytical study of the function of the combined blast and the main trends of its changes to the existing and expected conditions of blast furnace. Found that the assessment of the cost effectiveness of the combined advantageously carried out for the calendar period of time, more objectively reflect its economic value compared to the performance of specific (per 1 ton of pig iron).

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

References

  1. Ярошевский С.Л. Выплавка чугуна с применением пылеугольного топлива. – М.: Металлургия, 1988. – 176 с.
  2. Юсфин Ю.С., Черноусов П.И., Архипов Н.А.,Неделин С.В. Оценка энергоэффективности производства черных металлов в современных условиях // Сталь. 2000 №5. С. 88-94.
  3. Вегман Е.Ф., Жеребин Б.Н., Похвиснев А.Н., Юсфин А.С. и др. Металлургия чугуна. – М.: Металлургия, 1989. – 486 с.
  4. Полтовец В.В. «Доменное производство», М., - Металлургия, 1972-450 с.
  5. Литвинов Л.Ф., Ярошевский С.Л., Кузнецом А.М. Исследование и оптимизация технологии доменной плавки // Металл и литье Украины.– 2003.– №11–12.
  6. Бабич А.И., Ярошевский С.Л., Терещенко В.П. Интенсификация использования пылеугольного топлива в доменной плавке. – К.: Техника, 1993. – 200 с.
  7. Типовая технологическая инструкция по доменному производству. – Днепропетровск. – 1977 г.