JPS5939487B2 - Low NOx sintering operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for suppressing the production of nitrogen oxides (NOx) during the process of producing sintered ore using a downward suction sintering machine.

In recent years, methods for reducing NOx in the exhaust gas of sintering machines have been studied for environmental conservation from various angles, and the methods for reducing this include (1) reduction of input N, and (2) reduction of NOx during the sintering process. This can be roughly divided into (3) suppression of conversion rate, and denitrification of exhaust gas.

The present invention relates to (2), and maintains the quality and productivity of sintered ore at the current high level, and provides an economical low NO
The present invention aims to provide an X-sintering method.

Furthermore, it has the advantage that it does not require securing a low-N carbon material or high-temperature deN treatment of the carbon material as in the case of (1), or that it does not require the treatment of a huge amount of exhaust gas as in the case of (3).

NOx generated during the sintering process is caused by the oxidation of N in the carbonaceous fuel used, such as coke, semi-coke, coal, etc. The degree of oxidation (NOx conversion rate) depends on the CO concentration on the surface of the fuel particles. As the CO concentration increases, the NOx conversion rate decreases; when the CO concentration decreases, the NOx conversion rate decreases.
Ox conversion rate becomes high.

Therefore, the NOx conversion rate varies depending on the combustion state.

Based on the above idea, the present inventors believe that if iron powder including metallic iron powder, such as metallic iron, scale, and converter sludge (hereinafter simply referred to as iron powder) coexists with carbonaceous material, metallic iron can be produced. The CO on the surface of carbonaceous particles is reduced by the transition to a reducing atmosphere through oxidation of
This is due to the fact that the concentration increases, the NOx conversion rate decreases, and NOx can be suppressed, and the apparent surface area of the carbonaceous material increases by pseudo-granulating the carbonaceous material with a binder such as Cab1 bentonite, cement, and sulfite pulp waste liquid. It has been found that NOx can be suppressed by reducing the NOx conversion rate by improving the combustibility of charcoal.

The present invention relates to a method of uniformly coexisting iron powder or iron powder and a binder in powdered carbon material for sintering and using the dirt as a sintering fuel.

Possible methods for coexisting iron powder uniformly in powdered coal material and for granulating coke powder include mixed granulation using a disk pelletizer or a drum mixer.

However, the above-mentioned method requires an additional step in the normal sintering process, resulting in problems such as increased equipment costs and complication of the process.

The present invention involves the addition of iron powder during the process of normal sintering operations, that is, the crushing process of crushing carbonaceous material to produce powdered carbonaceous material for sintering, and combining the carbonaceous material and iron powder as necessary. This is a low NOx sintering operation method in which various binders such as CaO, bentonite, cement, and sulfite pulp waste liquid are added for the purpose of strengthening the sintering process, and carbonaceous materials and iron powder are uniformly coexisted, and this is used as a sintering fuel.

Examples Raw materials were prepared according to the mixing ratios shown in Table 1, and a sintering experiment was conducted using a 50 kg sintering experiment pot.

The type of carbon material used (coke was used here) is shown in Table 2.

Table 3 shows the particle size of the coke used, and Table 4 shows the sintering test results.

Symbols A to G correspond to Tables 2 to 4.

As shown in Table 4, each test was conducted twice.

Normally, the NOx conversion rate is as high as 30 to 31 when using coke alone, but coke with scale powder, converter sludge, and/or CaO and bentonite has a NOx conversion rate that is as high as 30 to 31. This is lower than in the case of , and the effect of NOx suppression is clearly visible.

On the other hand, product yield and productivity have been maintained.

As is clear from the above examples, by adding iron powder to coke in the fuel coke crushing process, N
Suppression of NOX by reducing the Ox conversion rate, product yield, and sinterability of productivity can be maintained at a high level, or by using a binder (
CaO bentonite is used here) to suppress NOx and improve product yield and productivity by reducing the NOx conversion rate through pseudo-graining of coke (reducing the proportion of grains smaller than 0,251 m). It can be expected that it will be maintained.

As described above, the effects of the present invention are significant.

Claims (1)

[Claims] 1. In the process of crushing carbonaceous material to make powdered carbonaceous material for sintered fuel, iron powder, or iron powder and Cab, bentonite,
A NOx sintering operation method characterized by adding an inorganic or organic binder such as cement or sulfite pulp waste liquid, crushing it, and using it as a sintering fuel.