Coking of coal into different types of products as a method of processing is in demand by many industries. This trend will continue in the near term.
However, further development of the method of coking is associated with a number of problems of technical and economic nature.
First, there are relatively limited reserves of coking coals, i.e. coals suitable to produce metallurgical coke. In the structure of balance reserves (202 billion tons) [1] proportion of all grades of coking coal is 18%, and most valuable brands– 17%. Second, the production costs of coking coal are higher than that of coal that can be used for coke production with improved technological base of the coking (low-caking coals). Third, prices for coking coal are really high. The price of scarce types of coal ranges from 1100 to 1600 rubles/ton, while the price of low-baked coals is in the range of 600-700 rubles per ton.
These circumstances suggest the need to find ways of involving into commodity balance of coke plants less scarce ranks (low-caking) of coal. This can be achieved by applying of new technologies (technical solutions) on different stages of the production cycle.
In the list of such technologies specialists include thermal preparation of charge, selective crushing, compacting of the coke charge and inclusion in the composition of charge of organic caking additives. Let us consider the content of these technologies and their impact on the coking process.
Thermal preparation of the charge before coking. The method of thermal treatment (drying, heating) can significantly increase bulk density of the coking mixture, since deleting from it the moisture it condenses, which creates favorable conditions for sintering. In result we got adequately strong coke from low-caking coal. Thermal method has found commercial use in France, England, Japan, USA, South Africa and other countries. In Russia on the West-metallurgical plant experimental-industrial installation for thermal preparation of charge for coking was built and is in the stage of development now.
Selective crushing of coking coal. Coals that are included in the composition of the charge before coking are of different size. Different size of articles affects sintering behavior of the charge and, consequently, the quality of coke. The technical solution of the task involved in bringing the charge of coal to a uniform size proposed by French experts. This method is based on selective crushing of coals the dimensions of which is more than required for effective sintering.
Compacting of the coke charge before coking. The expansion of the resource base of coking can be achieved through the application of methods of compacting of coal charge by tamping, the use of briquettes. In this case, bulk density and share of low-caking coal increases and the performance of coke ovens improves. These technologies are implemented in the Czech Republic and Poland [2].
The use of mixture of oil additives in charge. Application of this method allows partial replacement in charge’s composition of well fusible grades of coal by less scarce ones. To improve caking property of the charge the organic additives, for example, oil sludge are added. The proportion of additives in the total weight of the charge structure depends on the grades of coal used, and ranges from 3 to 8%. The introduction of additives to the charge does not require changing the technology of its preparation (crushing, dosage) and loading into the coke oven.
Implementation of these technologies in an industrial environment will allow the following:
- increase the share of low-caking coal used for coke production, which reserves are much more significant than the same rate for deficient grades of coal;
- reduce the cost of the charge used for coke production by increasing the share of low-caking coal in the composition of charge, which have lower price than the well-caking;
- reduce expenses on iron smelting, as in most cases, increased strength of the coke leads to cost reduction in the blast furnace.
- increase the productivity of coke ovens by increasing the density of the charge. Without input of new capacities enterprises are able to increase the production of coke significantly by using pre-mixed charge. When increasing the volume of production and having constant current costs (in annual terms), «economies of scale» occurs, the essence of which consists in the reduction of fixed costs («Salary», «Depreciation» and «Plant costs») per unit of product.
Let us consider the effect of the use of low-caking coals on variable costs of production of coke, through its basic component «Cost of raw materials». This article accounts for up to 70% in the cost structure of coke production [3].
To perform this task, you must enter a number of assumptions: the company production of main products has a typical capacity of 2 million tons of coke per year; the consumption of coal for production of 1 t of coke, regardless of their grade composition is equal to 1,63 t; calculation of the cost of coal of each brand to be considered on current prices.
Under these conditions, the cost of coal with different methods of preparation at the stage of carbonization is characterized by the figures presented in Table 1.
Table 1.
The impact of technology of preparation of the charge on its value
|
Technology |
Cost |
Ratio, %
|
|
| Mil rubl | rubl/t coke | ||
| Classic | 3876 | 1938 | 100,0 |
| New technologies | |||
| — thermal preparation | 3070 | 1535 | 79,0 |
| — selective crushing | 3408 | 1704 | 87,0 |
| — compacting charge | 3092 | 1546 | 79,0 |
| — the inclusion of oil additives | 3540 | 1770 | 91,0 |
Based on the data presented in Table 1, we can formulate the following conclusion: the application of methods of preparation of the charge before coking will increase the use of low-caking coals as raw materials for industry and thereby expand the resource base for coke production, improve the qualitative parameters of metallurgical coke and economic indicators of production.
The list of references
- Krasnyansky G.L. Ugol v ekonomike Rossii. Moskva: Ekonomika, 2010. – 383 c.
- Kuzmina T.I. Napravleniya sovershenstvovaniya tehnicheskoy bazy koksovaniya ugley i ih ekonomicheskaya otsenka. Materialy V Mezhd. nauch.- prakt.konf. «Aktual’nye vozmozhnosti budushego». Praga, 2009.
- Kuzmina T.I. Ekonomika kompleksnogo ispolzovaniya ugley. Moskava: Izdatelstvo MGOU, 2010. – 283 c.[schema type=»book» name=»ECONOMIC EVALUATION OF TECHNOLOGIES OF PREPARATION OF CHARGE FOR COKING COALS» description=»The comparative economic evaluation of technologies of preparation of the charge before coking.» author=»Kuzmina T.I.» publisher=»БАСАРАНОВИЧ ЕКАТЕРИНА» pubdate=»2017-01-22″ edition=»ЕВРАЗИЙСКИЙ СОЮЗ УЧЕНЫХ_28.11.15_11(20)» ebook=»yes» ]