JPH0160537B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for efficiently desulfurizing flue gas generated when producing sintered ore used as a raw material for blast furnace charging. [Prior Art] Iron sand and powder ore produced by preliminary treatment of iron ore are valuable raw materials for steel, and sintered ore is a product that utilizes these materials. Sintered ore is often used as a raw material for blast furnace charging because its particle size, strength, and reducibility can be controlled. Generally, sintered ore uses powdered ore, iron sand, etc. as the raw material for sintering.
Coke, lime, water, etc. are added to this as necessary, and the mixture is kneaded and granulated using a drum mixer to make it coarse, and then it is charged into a sintering machine and exposed to high temperatures of around 1300℃ to sinter it. Let the reaction take place, then crush,
Manufactured by cooling. At this time, the high temperature gas that has passed through the sintered layer of the sintered raw material contains sulfur removed from the sintered raw material.
Contains in the form of SO ₂ . Therefore, such sintering machine exhaust gas is desulfurized by, for example, a lime plaster method. Specifically, flue gas is first introduced into a cooling tower, brought into contact with water, etc. to perform some degree of cooling and dust removal, and then supplied to an absorption tower. In the absorption tower
A liquid containing calcium compounds such as lime is sprayed and brought into contact with flue gas, and sulfur in the flue gas is captured in the absorption liquid in the form of calcium sulfite or calcium sulfate. In this way, the dust-removed, desulfurized, and cooled flue gas is discharged outside the system by the exhaust fan. [Problems to be solved by the invention] However, in the sintering machine flue gas desulfurization method using such a calcium compound-containing liquid, a part of the sprayed absorption liquid becomes a mist after coming into contact with the flue gas. It scatters and adheres to the wall surface and mist separator above the spray surface. As a result, these deposits are constantly in contact with relatively high temperature flue gas,
The moisture in the deposit evaporates and the deposit dries up. This dry deposit is composed of calcium silicate, gypsum,
Contains iron oxide, etc., and forms an extremely hard scale. On the other hand, the sprayed absorption liquid is collected at the bottom of the absorption tower and oxidized in the oxidation tower to produce gypsum, but even in this aqueous system, a large amount of scale is generated. Conventionally, in order to prevent the formation of such scale, there has been a method of adding a scale inhibitor such as polymerized phosphoric acid or a polymer compound to the absorption liquid. However, these scale inhibitors act effectively only in areas that are in contact with the absorbing liquid, and are not effective against the formation of scale due to deposits caused by adhesion of mist as described above. [Means for Solving the Problems] The present invention has been completed in order to solve the problems of the prior art described above. This invention provides a sintering machine flue gas desulfurization method in which flue gas discharged from a sintering machine is brought into contact with an absorbing liquid containing a calcium compound, in which a polyhydric alcohol compound and a scale inhibitor are added to the absorbing liquid. This is a unique method for desulfurizing sintering machine flue gas. Examples of the calcium compound used in this invention include slaked lime, calcium carbonate, and waste alkali. Usually, these calcium compounds are made into an aqueous solution or slurry to form an absorption liquid. The polyhydric alcohol compound used in this invention is a compound having multiple alcoholic hydroxyl groups in one molecule, and specifically includes ethylene glycol, glycerin, erythritol, propylene glycol, and ethylene oxide of the above polyols. An example is an adduct. Among these, the molecular weight of ethylene oxide or propylene oxide is preferably 10111 or less. In this invention, a scale inhibitor is used together with the above polyhydric alcohol compound, but the scale inhibitor used here is not particularly limited, and any known aqueous scale inhibitor can be used. Specifically, polymerized phosphoric acids or their salts such as tripolyphosphoric acid and hexametaphosphoric acid, phosphonic acids such as aminotrimethylphosphonic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetramethylphosphonic acid, phosphonobutanetricarboxylic acid, phosphonocarboxylic acids, or the like. and carboxylic acid-based polymer compounds. Carboxylic acid-based polymer compounds include homopolymers or salts thereof such as polyacrylic acid, polymethacrylic acid, polymaleic acid, and polyitaconic acid, or acrylic acid, methacrylic acid, maleic acid, maleic anhydride, and other polymerizable monomers. - Copolymers of acrylamide, isobutene, butene, hydroxymethacrylate, styrene, styrene sulfone, or salts thereof are exemplified. The molecular weight of these polymer compounds is approximately 500 to 100,000, preferably approximately 1,000 to 10,000. The amount of these polyhydric alcohol-based compounds or scale inhibitors added to the absorption liquid varies depending on the type of sintering raw material, but the standard amount is 1 to 100%.
mg/degree. [Function] In polyhydric alcohol compounds, each alcoholic hydroxyl group is strongly bound to water through hydrogen bonds, etc. Therefore, even if a part of the absorption liquid containing the polyhydric alcohol compound becomes a mist and adheres to the wall surface or the mist separator above the spray surface, the water evaporates slowly and forms a wet film. As a result, the suspended solids in the mist are prevented from drying and remain soft. On the other hand, the scale inhibitor in the absorption liquid is adsorbed on the surface of the scale-forming precipitates, inhibits crystal growth and aggregation of the precipitates, and prevents scaling. The present invention will be further explained below with reference to Examples. [Example] Example 1 6 in an acrylic absorption tower (60 mmφ x 1000 mmH)
% calcium carbonate aqueous solution (containing 50 g of gypsum), and a test piece was suspended in the absorption liquid and above the water surface. SO ₂ concentration from the bottom to this absorption tower
Air at a temperature of 60° C. and a flow rate of 450 mg/min was supplied as flue gas from the simulated sintering machine at a flow rate of 15/min. I drove 7 hours a day for 10 days. Next, a propylene oxide adduct of glycerin (molecular weight 700) is added to the absorption liquid as a drug and as a polyhydric alcohol compound.
The operation was carried out under exactly the same conditions as above, except that 60 mg of sodium phosphonobutanetricarboxylate and 5 mg of sodium phosphonobutanetricarboxylate were added. Each of these operations was repeated twice, and after both operations were completed, the scale adhesion rate was determined from the amount of gypsum adhering to the test piece. The results for the test piece on the water surface are shown in Table 1, and the results for the test piece in the absorption liquid are shown in Table 2.

【table】

〔Effect of the invention〕

According to the method of this invention, the generation of dry solids due to mist adhesion in the absorption tower in the sintering machine flue gas desulfurization equipment, for which there was an effective countermeasure in the past, can be greatly reduced, and the adhesion itself is soft. It can be easily peeled off by simple means such as spraying high-pressure water. In addition, troubles caused by scale formation in the absorption liquid circulation system are greatly reduced, and maintenance and management of the desulfurization equipment is greatly facilitated.

Claims (1)

[Claims] 1. A sintering machine flue gas desulfurization method in which flue gas discharged from a sintering machine is brought into contact with an absorption liquid containing a calcium compound, in which a polyhydric alcohol compound and a scale inhibitor are added to the absorption liquid. A sintering machine flue gas desulfurization method characterized by adding. 2. The desulfurization method according to claim 1, wherein the polyhydric alcohol compound is one or more selected from the group consisting of ethylene glycol, glycerin, erythritol, and their ethylene oxide or propylene oxide adducts. 3. The desulfurization method according to claim 1 or 2, wherein the scale inhibitor is one or more types selected from the group consisting of polymerized phosphoric acid, phosphonic acid, and polymer compounds.