Method for heating a blast furnace stove

Abstract

A method for heating a blast furnace stove having a combustion chamber with a combustion zone therein, includes causing combustion gases to flow through and be exhausted from refractory material in the stove for heating said material, supplying and adding an oxidant comprising an oxygen content of at least 85% into the combustion chamber for recirculating the combustion gases including said oxidant into the combustion zone, wherein the recirculating the combustion gases is from a location inside the combustion chamber, but outside an area of the combustion chamber occupied by the combustion zone, and the supplying the oxidant to the combustion zone is at high velocity through at least one lance, thereby entraining the combustion gases into the combustion zone, diluting a mixture of the fuel and the oxidant with the recirculated combustion gases, and flamelessly combusting said mixture in the combination zone.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to a method for heating a blast furnace stove for use with a blast furnace.[0002]The combustion air supplied to a blast furnace is typically preheated using a stove, comprising refractory material which is heated using a burner. When the material is hot enough, combustion air is passed through the stoves to pre-heat it before injection into the blast furnace. Usually, several stoves are operated in parallel and cyclically so that at least one stove is operated for heating combustion air while the refractory material of at least one stove is heated.[0003]Conventionally, the top gas leaving the blast furnace has a temperature of around 110-120° C. and contains about 20-25% each of CO and CO2. Typically, 3-5% H2 and some H2O will also be present, but the other major constituent of the top gas is N2 (typically 45-57%). The gas constitutes a low grade fuel, having a relatively low heating value, and is commonly used to fuel t...

AI Technical Summary

Benefits of technology

The patent is about a method for heating a blast furnace stove by combusting a fuel with a low heating value in a combustion chamber. The fuel is combined with an oxidant made up of at least 85% oxygen, and the combustion gases are recirculated back into the combustion zone to dilute the mixture of fuel and oxidant and make the combustion flameless. This technique results in a more efficient use of the fuel and reduces emissions of harmful pollutants.

Problems solved by technology

The combustion of such additional fuel leads to larger overall emissions of carbon dioxide from the plant, and is therefore not desirable.

Such methods may in some cases render peak flame temperatures high enough to damage the refractory material of the stove, and it may be necessary for example to supply an excess air rate to suppress the flame temperature.

All the above-described methods add complexity to the process and require costly equipment.

It is approaching the limits of thermodynamic efficiency, which is why it is difficult to reduce energy consumption relative to current best operating practices.

Furthermore, the energy consumed in iron making is the dominant factor determining the carbon consumption of the integrated steel making process, and therefore the emissions of carbon dioxide.

However, such separation is relatively expensive.

In addition to the problem of high peak temperatures mentioned above, too low flame temperatures or heat input rates will lead to long heating cycles, which is undesirable.

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