Siderite, Spathic Iron Ore, FeCo3

Containing 30 to 40% Fe, siderites are relatively easy to reduce; they mostly contain lime and manganese and are low in phosphorus. Variations of spathic iron ore arise as a result of contamination with clay (argillaceous iron ore) and coal (carbonaceous ironstone or black band). The famous ore mountain in Steiermark (Styria) Austria, consists of spathic iron ore. Deposits of siderites no longer have any major economic importance.

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(Текст та методична розробка В. Коркішко)

Commercial Classification, Types and Specification of

Iron Ores

1. The important technical factors that determine the usability and thus the value of an iron deposit are:

1. iron content;

2. chemical composition other than iron;

3. physical characteristics;

4. amenability to concentration.

Ores averaging less than 50 per cent iron are usually upgraded by one or another concentration techniques.

2. The standard iron – ore classification is based on chemical composition and impurities. Impurities are present in all iron ores and are important cost factors in both concentrating and palletizing plants and in the blast furnace. In addition to increasing costs for their removing, some impurities are objectionable in the furnace operation while others affect the quality of the pig iron.

In general, impurities in direct shipping ores, concentrates or agglomerates may be classed as “enhancing” or as “deleterious”.Enhancing impurities either aid the blast – furnace processing or add value to the hot metal produced. They include manganese minerals and the fluxes such as lime, magnesia, and fluospar. Deleterious impurities include those which have adverse affects on the properties of the slag. Titania, for example, affects the fluidity of the slag. So certain impurities such as titanium and sulphur, even when present in small amounts may significantly decrease the value of an ore with high iron content.

3. Impurities react differently to the reduction conditions in the blast furnace and are commonly classified according to their response to the reduction reaction:

   1. Impurities which are never reduced in the blast furnace (and so do not affect the composition of the pig iron): aluminia, lime, magnesia, oxides of sodium and other alkali metals and others.

   2. Impurities which may be partially reduced in the blast furnase. These include silica, silicates, sulphur, titania, and other elements.

The behavior of sulpur compounds is just the opposite to that of silica compounds. A part of sulphur compounds introduced into the furnace enter the pig iron as ferrous or manganese sulphides. Most high sulphur ores (0,05 per cent or more) must be roasted or sintered before they can be used economically.

3. Impurities which are always reduced in the furnace and often alloy with the iron. These are all compounds of arsebic, phosphorous, nicel, copper, сadmium, tin, etc.

1. In addition to the consideration of impurities, there are several other chemical factors which are important in evaluating a ferrous burden for use in any specific blast furnace.

Basicity: The basiciti of a direct shipping ore or beneficiated burden provides a means to calculate the amount of limestone, or other flux, to be added to the blast – furnace burden to produce a slag of the proper composition and properties. The basicity of an ore may be calculated in one of two ways, depending on the practice used at a particular furnace and the nature of the ore:

1. СaO +MgO (ideally 1,4) ;

SiO2

b) СaO +MgO (ideally 1,1)

SiO2+Al2O3

5. Iron – Silica Ratio: The iron – silica ratio and the iron – acid ratio

6. ( Iron )

Silica +Alumina,

together with the basicity of the ore, determine the total amount of slag which will be produced from a ton of any given ferrous burden material when smelted in the blast furnace. The optimum ratio for each furnace is that which gives the minimum slag volume needed for desulphurization and for elimination of the other impurities present in the burden, while at the same time permitting the highest iron content possible.

For many years blast – furnace operators preferred an ore containing 7 to 8 per cent SiO2 wits an iron – silica ra of about 7 : 1. However, in resent years, silica requirements for desulphurisation of the hot metal have gradually decreased, particularlu with the use of higt – grade low – sulphur iron ores and pellets and low – sulphur coke, so that now about four per cent silica is often sufficient to provide the necessary volume of slag. Hence ores with a ratio of 10 : 1. or higher, are now considered desirable.

1. ferrous burden – железосодержащая шахта

2. fluxstone – флюс

3. screened ore – грохоченная руда

4. beneficiated ore – обогащенная руда

5. pellet – окатыш

6. hydrous oxides – гідроокиси

7. сhemical composition other than iron – химический состав пустой породы

8. amenability to concentration – обогатимость

9. ores averaging – руды со средним содержанием

10.еnhancing or as deleterious - положительные и отрицательные (примеси)

11.to add value – улучшать качество (чугуна)

12.lime - известь

13.fluxes - флюсы

14.fluospar – плавиковый шпат

15.titania – диоксит титана

16.flulidity - жидкотекучесть

17.oxides of sodium – oкись натрия

18.alkali metals – щелочные материалы

19.silica - кремнезем

20.соmpounds of arsenic – соединения мышьяка, олова

21.tolerance limit – допустимый предел

22.basicity - основность

23.iron – silica ratio – отношение железа к кремнезему

24.iron – acid ratio - отношение железа к кислотным окислам

25.frigh – grade low – sulphur iron ores - высококачественные низкозернистые железные руды

26.volume of slag – объем шлака

II. Find in the – text English equivalents of the following Russian sentences.

1. Руды со средним содержанием железа ниже 50 % обычно обогащают с помощью того или иного способа. 2. Положительные примеси либо способствуют доменной плавке, либо улучшают качество чугуна. 3. Примеси содержащиеся во всех железных рудах и являются существенными факторами как при обогащении, так и при окомковании, а также при использовании в доменной печи. 4. Часть сернистых соединений, загружаемых в доменную печь, поступает в чугун в виде сульфидов железа или марганца.

Check up your comprehension of the text

I. Try and complete the sentences listed below by a suitable variant.

1. The standard iron – ore classification is based on...

а) the quality of pig iron;

1. cost factors;

с) chemical composition and impurities.

2. The chemical composition of an ore is determined by ...

а) chemical analysis;

b) its amenability to concentration;

2. its mineralogy.

3. Impurities are present in all iron ores and...

а) are objectionable in the furnace operation;

2. affect the quality of the pig iron;

3. are important cost factors in both concentrating and palletizing plants and in the blast furnace.

1. In general, impurities in direct shipping ores, concentrates or agglomerates may be classed as...

а) which are never reduced in the blast furnace;

2. which may practically reduced in the blast furnace;

3. enhancing or as deleterious.

II. Point out which of the sentences below contains the information related to the text.

1. The principal raw materials consumed in the blast furnace are the ferrous burden, сoke and fluxstone.

2. The trend of the industry has industry has been at least to remove and to agglomerate the natural fuels prior to charging to the blast furnace.

3. Iron is one of the most abundant elements in the earth, constituting about 5 per cent of the earth’s crust.

4. Although there are many iron – bearing minerals, only a few are important commercially.

5. Impurities react differently to the reduction conditions in the blast furnace and are commonly classified according to their response to the reduction reaction.

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