KR20010059374A - Sulfur dioxide reduction method using ammonium bicarbonate at the process of iron ore sintering - Google Patents

Abstract

PURPOSE: A method for reducing sulfur dioxide using ammonium carbonate hydrogen in a sintering process of an iron ore is provided to remove sulfur dioxide formed as ammonium sulfate by using a dust collector, thereby easily reducing sulfur dioxide discharged to the atmosphere. CONSTITUTION: An ammonium carbonate hydrogen is included in sintered compound material formed of powder iron ore, limestone, and powder coke in a Dwight-Lloyd type sintering machine and supplied to a sintering machine truck, so that ammonium gas generated by pyrolysis reaction of the ammonium carbonate hydrogen reacts to sulfur dioxide gas generated by oxidation of sulfur component included in cokes for converting sulfur dioxide into ammonium sulfate.

Description

Sulfur dioxide reduction method using ammonium bicarbonate at the process of iron ore sintering}

In the present invention, in the iron ore sintering method using a dwight-lloyd type sintering machine, ammonium bicarbonate (NH ₄ HCO ₃ ) is added to a sintered blend material composed of a mixture of powdered iron ore, limestone and powdered coke. When the sintered compound raw material is burned on the sintering tank and the sintering reaction occurs, the ammonia (NH ₃ ) gas generated by pyrolysis of ammonium bicarbonate mixed in the sintered compound material reacts with sulfur dioxide (SO ₂ ) contained in the sintered exhaust gas. The present invention relates to a method for reducing sulfur dioxide contained in the reaction flue gas.

The feature of this method is that it does not require a separate sulfur dioxide treatment device in the iron ore sintering process, and by adding a small amount of ammonium bicarbonate to the sintered compound, sulfur dioxide generated during the sintering process of iron ore can be effectively removed.

The structure of a general Dwight-Lloyd iron ore sintering machine 1 is shown in FIG. 1. The sintering machine 1 is composed of a sintering machine bogie 2 composed of endless tracks, and the sintering compound raw material is supplied onto the sintering machine bogie 2 through the raw material supply device 5. The sintered compound raw material forms a sintered raw material layer having a constant height on the sintered bogie 2, and when the sintered bogie 2 passes through the ignition furnace 6, the upper end of the sintered raw material layer is placed in the ignition furnace 6 It is ignited and the sintering reaction through combustion is started. As the sintering reaction proceeds, the sintered raw material layer forms a sintered layer composed of a sintered ore, a combustion zone, a drying zone, and a water condensation zone. After the sintering reaction is completed, only a blocky sintered ore remains. As shown in Figure 2, the bottom of the sintering tank bogie 2 is composed of a grate (3) so that the air required for the sintering reaction can pass through the sintering layer, the lower part of the sintering bogie (2) The main air pipe 7 to which the air intake 8 of the structure as shown is connected is connected. The air sucked from the top of the sinter bed by the air inhaler 8 is used to burn fuel coke mixed with the sinter blend material in the sinter bed.

On the other hand, coke used as a fuel for combustion of a sintered blend raw material contains a sulfur component of about 0.5 to 0.6 wt%. Therefore, when coke is burned in the sintered layer, sulfur contained in the coke is also burned to generate sulfur dioxide gas. In general, the sintering flue gas having a sulfur dioxide concentration of about 100 to 200 ppm is emitted in the existing sintering process, which is known as a representative air pollutant causing urban smog and acid rain.

Recognizing this problem, various methods for removing sulfur dioxide gas contained in sintered flue gas have been proposed. Among them, the concentration of sulfur dioxide contained in sintered flue gas using selective catalytic method or wet method before sintered flue gas is discharged into the atmosphere. However, considering the enormous amount of sintered flue gas discharged from the sintering process, the investment cost and the operating cost are excessive, and the economical situation is questioned at present.

In order to solve the above-mentioned problems, the present invention adds and mixes ammonium bicarbonate to the sintered blending material and loads it into the sintering machine to generate ammonia gas and react with sulfur dioxide generated by the combustion of sulfur components of the ammonia gas. This aims to reduce the concentration of sulfur dioxide in the reaction flue gas.

FIG. 1 is a schematic view showing the structure of a sintering apparatus and a sintering apparatus of the Dwight-Lloyd type composed of an endless track sintering apparatus bogie.

2 is a perspective view schematically showing the sintering machine bogie of FIG.

Figure 3 is a block diagram showing a sintering pot tester used to demonstrate the effect of the present invention.

4 is a graph showing the results of experiments demonstrating the effects of the present invention.

Explanation of symbols for main parts

1: sintering machine, 2: sintering machine

3: grate, 4: sintering pot

5: raw material supply device, 6: ignition furnace

7: main exhaust pipe, 8: air intake

9: gas analyzer

Sulfur dioxide reduction method using ammonium bicarbonate in the iron ore sintering process according to the present invention for achieving the above object is supplied to the sintering machine bogie consisting of a mixture of powdered iron ore and limestone and powdered coke in the sintering machine of the Dwight-roid type Ammonium bicarbonate is further included in the sintered blend so that the ammonium gas generated by the pyrolysis of the ammonium bicarbonate is reacted with the sulfur dioxide gas produced by the oxidation of the sulfur component contained in the coke to convert sulfur dioxide into ammonium sulfate. It is made to include.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

According to the present invention, by further including ammonium bicarbonate in the sintering blending material required for the sintering of iron ore, sulfur dioxide which may be generated due to the presence of sulfur components contained in the coke as fuel necessary for the sintering of the iron ore is characterized. It is done.

Ammonium bicarbonate mixed in the sintered blend material is thermally decomposed during sintering to generate ammonia gas, which reduces the amount of sulfur dioxide released into the atmosphere by reacting with sulfur dioxide in the sintered bed. Ammonia can be removed by electrostatic precipitators before reacting with sulfur dioxide to form ammonium sulfate and release it into the atmosphere. A process of converting ammonium bicarbonate to ammonium sulfate by reacting with sulfur dioxide is described by using a chemical reaction equation.

S + O ₂ → SO ₂

NH ₄ HCO ₃ + heating → NH ₃ + CO ₂ + H ₂ O

2NH ₃ + 2H ₂ O → NH ₄ OH

2NH ₄ OH + SO ₂ + 1 / 2O ₂ → (NH ₄ ) ₂ SO ₄ + H ₂ O

That is, one molecule of ammonium bicarbonate is decomposed into one ammonia molecule, carbon dioxide and one water molecule by heat. Ammonia decomposed from ammonium bicarbonate is dissolved in water in the water condensation zone in the sintered layer and is present in the ammonium hydroxide state. Here, ammonium hydroxide reacts with sulfur dioxide generated in the upper combustion zone to form ammonium sulfate in the solid state, and most of the ammonium sulfate thus produced is collected by an electrostatic precipitator or the like before being discharged into the atmosphere.

Ammonium bicarbonate is a white crystal and has nontoxic properties and easily decomposes at about 36 ° C to 60 ° C to release ammonia gas. In addition, since ammonium bicarbonate is widely used industrially and is an inexpensive and effective source of ammonia gas, it is possible to reduce the sulfur dioxide concentration in the sintered flue gas simply and efficiently by adding a small amount to the iron ore sintered blended material without additional equipment. Has the advantage.

The ammonium bicarbonate may be included in the range of 0.05 to 0.2% by weight based on the total sintered blended material, and particularly preferably in the range of 0.10 to 0.15% by weight. It may be included, and may also be added after the completion of the formulation of the sintered blend raw materials. However, in order to include the ammonium bicarbonate evenly, it is preferable to include the ammonium bicarbonate during the blending of the sintered blending material.

Specific embodiments of the present invention will be described below.

Example

In order to prove the effect obtained by the present invention, the following experiment was performed using a sintering pot tester as shown in FIG. 3. The sintering port here corresponds to a sintering machine bogie in a mass production dwight-roid type sintering machine. Through a series of raw material assembly processes, the standard sintered blended raw materials (powdered iron ore as the raw material, powdered limestone as the raw material, and iron ore blended raw material of powder coke as fuel) are loaded into the sintering plant of the Pohang Works. It prepared by the compounding ratio of Table 1. As an example, 50 g of ammonium bicarbonate was evenly mixed with 41 kg of the sintered blended raw material, and the sintered blended raw material was charged into a sintering pot. Then, using the sintering furnace 6 to sinter under the sintering test conditions shown in Table 2, the upper portion of the sintered blended raw material was ignited at 1,100 ° C. for 2 minutes. Thereafter, the air inhaler was operated to continuously suck air necessary for sintering from the top of the sintered compound material layer to the bottom. Sintered flue gas discharged during sintering was collected by a commercialized gas analyzer (Testo 33, Fuel Cell type) (9), and sulfur dioxide concentration in the flue gas was investigated. In addition, in order to investigate the effect of the addition of ammonium bicarbonate on the productivity and quality of the sintered ore, the sintering productivity, the sintered light intensity and the recovery value were investigated, and the results are shown in Table 3 and FIG. 4.

<Table 1> Sintered Experimental Blends

Raw material and fuel Compounding ratio (% by weight) ironstone 80.42 Limestone 12.07 Serpentine 2.24 Quartz 0.69 quicklime 0.93 cokes 3.65

<Table 2> Sintering Experiment Conditions

Sintered Layer Diameter 240 mm Sintered Bed Height 500 mm Ignition temperature 1,100 ℃ Air suction pressure 1500 mmH ₂ O

<Table 3> Sintering pot test results

Total amount of sulfur dioxide emitted Sintered Productivity Sintered Light Intensity Sinter Recovery Rate Example 17ℓ 25.7t / m ² / d 80.2% 77.7% Comparative example 47ℓ 25.7t / m ² / d 79.8% 76.0%

Comparative example

Except that ammonium bicarbonate was not added to the sintered blended material, the same process as in Example was performed, and the results are also shown in Table 3 and FIG. 4.

Referring to the results shown in Table 3 and FIG. 4, in the case of the comparative example in which ammonium bicarbonate was not added to the sintered blended raw material, the total amount of sulfur dioxide was 47 L. In this case, total sulfur dioxide emissions were 17ℓ. On the other hand, as a result of investigating the effect on the sintering productivity and sintered light quality when the ammonium bicarbonate was added to the sintered blended raw materials, it was found that there is no significant difference when comparing the results of the examples according to the present invention with the comparative examples. .

Therefore, according to the present invention, by adding a small amount of ammonium bicarbonate to the sintered blend material charged on the sintering tank bogie, ammonia produced by pyrolysis of ammonium bicarbonate mixed in the sintered blend material during the sintering process is combined with sulfur dioxide contained in the sintered flue gas. By reacting in the sintered layer to form ammonium sulfate, sulfur dioxide can be effectively reduced without adversely affecting the sintering productivity and the quality of the sintered ore.

Claims (5)

Ammonium gas produced by pyrolysis of ammonium bicarbonate by further including ammonium bicarbonate in the sintered blended raw material supplied to the sinter mill bogie consisting of a mixture of powdery iron ore, limestone and powdery coke in a dwight-type sintering machine A method for reducing sulfur dioxide using ammonium bicarbonate in an iron ore sintering process comprising converting sulfur dioxide into ammonium sulfate by reacting with sulfur dioxide gas generated by oxidation of sulfur component contained in coke. The method of claim 1, The method of reducing sulfur dioxide using ammonium bicarbonate in the iron ore sintering process, characterized in that the amount of ammonium bicarbonate contained in the sintered blended material is included in the range of 0.05 to 0.2% by weight relative to the total sintered blended raw material. The method of claim 2, The method of reducing sulfur dioxide using ammonium bicarbonate in the iron ore sintering process, characterized in that the amount of ammonium bicarbonate contained in the sintered blended material is included in the range of 0.10 to 0.15% by weight based on the total sintered blended raw material. The method of claim 1, The method of reducing sulfur dioxide using ammonium bicarbonate in the sintering process of the iron ore, characterized in that the ammonium bicarbonate is included in the blending of the sintered blending material. The method of claim 1, The method of reducing sulfur dioxide using ammonium bicarbonate in the sintering process of the iron ore, characterized in that the ammonium bicarbonate is added after the completion of the blending of the sintered blending raw material.