The question of the optimum input of natural gas

Summary

• 1. The specific inputs of natural gas in m³/ton of iron are determined by actual conditions of blast-furnace smelting in connection with which their numerical values for different plants vary within extremely broad limits; the optimum values achieved at certain plants cannot be unquestionably adopted in the practice of other plants.

• 2. As has been shown by statistical processing of production data, the lowest numerical values of the index of input of natural gas in m³/ton of iron correspond to the lowest specific inputs of coke, and vice versa. The highest numerical values of this index is observed in cases where for one reason or another the coke consumption remains relatively high. This dependence is confirmed by the relative constancy of the ratio of inputs of natural gas and blast.

• 3. The index of input of natural gas expressed in percent of natural gas in the blast is the most stable and to a greater extent corresponds to technological requirements in choosing the blast regime. For the majority of plants its optimum values lie in the interval 3.5–4.5% of atmospheric blast.

• 4. As shown by test data, when the blast is enriched with oxygen the numerical values of the index of naturalgas input (in m³/ton of iron) do not reach the estimated level; the index of input of natural gas expressed in percent of enriched blast rises in proportion to the degree of enrichment and amounts to 8–9% with 30% O₂ in the blast. These figures require confirmation by collection of production data for various smelting conditions.

• 5. As indicated by the practice of many plants, exceeding the optimum specific inputs of natural gas leads either to a reduction in the effectiveness of its utilization or (if it is accompanied by a rise in the temperature of the blast) to a drop in furnace productivity.

• 6. The apparent lack of correspondence between the input of natural gas and the increase in blast temperature coming from the generally adopted ideas concerning the relation of these parameters, as well as the divergence between the estimated and practically achieved indices of natural-gas input, can be explained if the classical principles of calculating the gas dynamics in volumes of the gas phase reduced to normal conditions are abandoned, and the gas-dynamical conditions in the blast furnace are determined from the actual temperatures and pressures.