JPS58196828A - Desulfurization and denitration of exhaust gas from sintering machine - Google Patents

Abstract

PURPOSE:To effectively carry out desulfurization and denitration in an optimum temp. region, by a method wherein the exhaust gas of the first half part in a sintering process is subjected to low temp. denitration treatment while the exhaust gas of the latter half part in said sintering process is subjected to desulfurization treatment to make efficient use of characteristics of the exhaust gas from a sintering machine. CONSTITUTION:The exhaust gas of a sintering machine 21 is separated into a low SO2 concn. exhaust gas near to an ore supply side (wind boxes 1-9) and a high SO2 concn. exhaust gas near to an ore discharge side (wind boxes 10-16) while the former is taken out at about 100 deg.C to be introduced into a denitration apparatus 24 where subjected to denitration by activated carbon, while NH3 is injeted, to be exhausted from a chimney 25. The latter is cooled to 120-160 deg.C in a waste heat boiler 22 and, after dust is removed therefrom, the dust removed gas is subjected to desulfurization in a desulfurization apparatus 23 by activated carbon.

Description

[Detailed description of the invention] The present invention relates to a refreshing method for desulfurization and denitration of sintering machine exhaust gas.

Conventionally, the mainstream method for making iron has been the blast furnace method, which uses sintered ore powder as raw material for p-steel making, but the exhaust gas emitted during the sintering process contains dust, sulfur oxides, and nitrogen oxides (hereinafter l'SOx, NOx, respectively
When the water (referred to as J) is washed away, it is purified by dust collectors, desulfurization/denitrification equipment, etc., and released into the atmosphere to protect the soil environment.

However, these environmental protection equipment costs and operating costs are comparable to those of the sintering machine itself, and have been a major factor deteriorating the economic efficiency of the sintering-blast furnace method.

For this reason, various improvement measures have been proposed from the viewpoint of desulfurization ability, denitrification ability, economic efficiency, etc.

For example, a desulfurization device (Jitto No. 1296507) that can selectively desulfurize the exhaust gas from the wind box of the high-concentration SOx generation part on the discharge side of the sintering machine, and a device similar to the above, have a high 80x concentration. A method (Japanese Patent No. 1019857) has been proposed in which exhaust gas is dehumidified and then supplied to the feed side of the sintering machine to reduce the total amount of exhaust gas and perform desulfurization. However, all of these proposals relate only to desulfurization and do not propose denitrification.

On the other hand, in the above-mentioned method, a method of denitrification and sulfur removal instead of dehumidification (%Kitsuki No. 1065092) has been proposed, but the denitrification ability is not particularly sufficient.

The cause of this is thought to be largely due to the a-state of the exhaust gas as described below.

FIG. 1 shows an example of actually measured values of the 801-NOx 111g distribution in the exhaust gas and the exhaust gas temperature distribution, which are frequently generated in each wind hox of a moving bed sintering machine.

(However, each Windhox is numbered from the ore supply side to the ore discharge side.) As is clear from this figure, 802 degrees are highly concentrated in the ore discharge 11C sintering layer (m*half). However, the NOx concentration is distributed throughout, and is high in the center excluding both ends. The exhaust gas temperature is high on the ore discharge side, and is around 100°C from the ore feed side (the first half of the sintering process). Although these characteristics differ somewhat depending on the sintering machine, it is safe to assume that they have similar trends.

The desulfurization and denitrification methods described above do not take full advantage of these characteristics, and judging from the NOx concentration distribution shown in Figure 1, approximately half of the NOx is discharged untreated. I couldn't do that. Furthermore, all of the conventional methods have four disadvantages economically.

The present invention takes into consideration the above points, takes advantage of the characteristics of sintering machine exhaust gas, provides a suitable temperature range for desulfurization and denitrification, effectively performs desulfurization and denitration, and provides an economically advantageous sintering machine exhaust gas. With the aim of providing a desulfurization and denitrification method, the present inventors have conducted extensive studies and have completed the present invention.

That is, the present invention performs sintering by dividing the exhaust gas generated during the sintering process of iron ore into the exhaust gas from the first half of the sintering process, which has a low 5OxQ degree, and the exhaust gas from the second half of the sintering process, which has a low SOx degree of 0. I
The exhaust gas of the tI period sintered filter is 90% in the presence of N)i.
Denitration treatment is carried out at a temperature range of ~120°C, and after the sintering process, the exhaust gas in the middle part is denitrated as it is or in the presence of NH.
It is characterized by desulfurization treatment in a temperature range of 160°C.

Conventionally known desulfurization methods include the sub-cocoon method and the lime/cocoon method.
There are the limestone/gypsum method and the activated carbon method, and the catalytic reduction method uses Kinne oxide or activated carbon as a catalyst as a deionization method.
The active member method is known as a simultaneous desulfurization and denitrification method.

Among these, dry methods are suitable for desulfurization and denitrification because they do not cause a drop in exhaust gas temperature and do not increase moisture in the exhaust gas from the viewpoint of energy conservation, etc.; I get headaches when I sit there.

A low-temperature denitrification (desulfurization) method using activated carbon under injection of ammonia (%Gan Sho 54-127693, 4
131181sO-28674)>E is known, but all of these are aimed at simultaneous desulfurization and denitrification.
It is reported that under normal SOx coexistence, a denitrification rate of only 40% can be obtained.

However, the inventors have conducted numerous tests and found that when the SOX concentration is below 250 ppm, the space velocity t(s
V) a o o ~ 800 hr-', gas temperature 145
℃, NOx i1 degree, and 200 ppm, a high denitrification rate was obtained as shown in the wJ2 diagram. The cause is coexistence SO
Due to the low concentration of carbon, the surface of activated carbon is
It is presumed that the catalytic oiliness persists because it is not covered by the catalytic acid ammonium salt, etc.).

As is clear from FIG. 1, the exhaust gas in the first half of the sintering process fully satisfies the above-mentioned SOX content condition.

Therefore, the exhaust gas from the first half of the sintering process is denitrified, and the sintering*
It is suitable to desulfurize the exhaust gas in the second half after about 1 hour.

Furthermore, this makes it possible to carry out the process in a low &A temperature range suitable for each treatment.

Next, the present invention will be explained based on FIG. 3, taking as an example a case where a moving bed type sintering machine having a wind box is used.

As the supplied nine ores move from the supply side to the discharge side of the sintering machine 21, IIA consolidation progresses. is generated. In particular, we focused on the concentration distribution of SO1, focusing on the exhaust gas with a low concentration of SO1, the exhaust gas with a low SO1 concentration (wind box 1 to 9), and the exhaust gas with a high SO2 chain concentration (wind box 1 to 9). Boxes 10 to 16) are divided into two parts, and each type of exhaust gas is processed according to its properties.

The latter SO, 6 degree high exhaust gas is processed by the waste heat boiler 22.
After cooling to 60° C. or lower and collecting dust, it is supplied to JN sulfur in a desulfurization device 23. In this case, lower temperatures are better for desulfurization purposes, but low I! The temperature is set at 120°C or higher in consideration of corrosion, etc. -r When injecting ammonia, there is no problem of low-temperature corrosion, but if the temperature is set in the range of 140 to 160°C in hopes of simultaneous denitrification, the average NOx concentration will be relatively low, as shown in Figure 1. Coupled with the effect, even in the coexistence of SOx, the
It has the advantage of providing a relatively high denitrification effect with a maple degree of ~40%.

In addition, the exhaust gas from the wind box near the ore supply side is SO.
#1 is taken out at a temperature of about 100° C.me, containing almost no X, and after being denitrified in the denitrification device 24, is discharged from the chimney 25.

In this case, the exhaust gas temperature at the ore feed side to be denitrified is
Although the temperature f of conventional low-temperature denitrification treatment (approximately 150°C) is lower, the 80X concentration is sufficiently low that denitrification can be effectively carried out at 90 to 120°C using activated carbon while injecting ammonia. . Further, it is preferable that the activated carbon has a relatively low SV (space velocity).

If you want to increase the exhaust gas temperature on the feed side to some extent, the exhaust gas temperature should be high (80x exhaust gas at the end of the sintering process with low concentration (exhaust gas from the wind box 16 in Figs. 1 and 3)). It is best to mix this with the exhaust gas near the ore feed side for denitration treatment.

In the figure, 26.26' indicates an electric industrial appliance, and 27.27' indicates a boiler.

Through the above operations, all of the exhaust gas from the wind box is desulfurized and denitrated, resulting in a high overall removal rate.

Activated carbon subjected to desulfurization and denitrification is regenerated by heating and reused. In FIG. The following is an example of a flow sheet for carrying out all of the above in one go. In this way, if activated carbon is recycled all at once, the equipment cost will be lower and the site area will be reduced.

The desorbed SOt gas is recovered by a by-product recovery device 29.

In the explanation of the present invention, activated carbon is used as a representative adsorbent for Iwao element, while semi-formed coke and charcoal are used to refer to those made by supporting gold X oxides or activated carbon to support metal oxides. But you can get the same effect.

Hereinafter, the effects of the present invention will be clarified through examples.

Example A fixed-bed bench test device with an active return capacity of 1 dia. was used as the desulfurization device and the denitrification device.
Desulfurization and denitrification were performed using the process shown in the figure.

The results are shown in the table below, together with the properties and processing conditions of the exhaust gas from the ore discharge side of the sintering machine (the latter half of the sintering process) and the exhaust gas from the ore feed side (the first half of the sintering process).

As is clear from the results, an excellent desulfurization and denitrification effect was obtained.

[Brief explanation of the drawing]

Figure 1 shows an example of actual measured values of SQ, NOx concentration distribution and exhaust gas temperature distribution in the exhaust gas generated from each wind box of a moving bed sintering machine, and Figure 2 shows the influence of SO2 concentration on the denitrification rate. FIG. 3 illustrates an embodiment of the present invention. FIG. 4 is a flow sheet showing an example of adsorbent regeneration. 21...Sintering machine 23...Denitrification device 26...
・Desulfurization equipment patent applicant Sumitomo Heavy Industries, Ltd.

Claims (1)

[Claims] 1. The waste gas generated during the sintering process of iron ore is divided into two parts: waste gas from the first half of the sintering process with a low SOx concentration of 0, and waste gas from the second half of the sintering process with a high SOx concentration. In the method of desulfurizing and denitrating using a solid adsorbent, the sintered
AI! The exhaust gas in the t1 half is 90 to 120 in the presence of NH.
The exhaust gas from the latter half of the sintering process is denitrified at a temperature range of 120-160°C in the presence of NH or NH.
A desulfurization and denitrification method for sintering machine exhaust gas characterized by desulfurization treatment at a temperature range of 0