Gas-based direct reduction ironmaking method and system for controlling nitrogen enrichment

Abstract

The invention discloses a gas-based direct reduction ironmaking method and system for controlling nitrogen enrichment. The process of the method comprises the following steps that (1) one part of top gas after direct reduction is subjected to pressure supplementation and then is converged with reduction process gas to participate in a reduction reaction again; (2) the other part of top gas after direct reduction is used for generating power by using residual pressure; the top gas generated after residual pressure power generation is combusted to be heated to generate steam; and flue gas discharged in the combustion process is discharged; and (3) part of the steam generated in the step (2) is subjected to steam power generation. According to the method, through two-step energy conversion, generated steam and electric power can be introduced into a direct reduction system for use; the quantity of the top gas drained for nitrogen removal can be flexibly adjusted, so that the nitrogen enrichment degree in the whole process circulating gas is effectively controlled, and the economic benefit of a factory is maximized; and the method has the characteristics of good nitrogen enrichment reduction effect, high energy utilization rate, energy conservation, emission reduction and the like.

Description

technical field [0001] The invention relates to a direct reduction ironmaking system and method, in particular to a method for rationally controlling the nitrogen enrichment degree in a gas-based direct reduction process. Background technique [0002] In the traditional direct reduction process using 100% natural gas, since the nitrogen content in the make-up gas is almost zero, there is no problem of nitrogen enrichment. However, in the direct reduction process using industrial synthesis gas (such as coal gas) or industrial tail gas (such as coke oven gas), since the reducing gas contains part of nitrogen, nitrogen does not participate in the reduction. In the process of recovery and recycling, nitrogen will be gradually enriched, so that the proportion of nitrogen in the process cycle gas will become higher and higher. [0003] The enriched nitrogen in the process cycle gas, on the one hand, will reduce the reducing gas (H 2 , CO) partial pressure, which affects the redu...

AI Technical Summary

Problems solved by technology

[0005] The first way will make the preparation process of the supplementary gas more complicated and increase its preparation cost

The second way is affected by the gas demand of the heating furnace itself. Directly replacing the heating furnace equipped with the original factory usually requires a smaller amount of gas than the total amount of process gas. The increase in nitrogen emission through this way is very limited.

[0006] Therefore, in view of the problem of nitrogen enrichment, there is still a lack of an effective gas-based direct reduction ironmaking method and system that can reasonably control the degree of nitrogen enrichment.

Images