JPH0573707B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an accelerating agent for cold pellets, and more particularly to an accelerating agent for cold pellets, which is one of the methods for processing fine iron ore (hereinafter referred to as fine ore) generated during mining. . [Prior art] In recent years, the amount of iron ore used has increased rapidly, the reserves of high-quality iron ore have decreased, and the development of ore processing technology has made it possible to obtain high-grade fine ore.
Pelletizing methods have rapidly become popular. The mainstream of making fine ore pellets was to use a drum-type or pan-type granulator with an appropriate moisture content, and then granulate and then fire the pellets. However, from the viewpoint of energy saving and environmental protection, the firing process Instead, a cold pellet method using ordinary Portland cement as a binder is used. [Problems to be solved by the invention] Normally, the minimum strength when carrying pellets horizontally (primary handling strength) is approximately 5 to 20 kgf/cm ² , and the minimum strength when charging pellets to the blast furnace (secondary handling strength) is approximately 30 to 20 kgf/cm 2
100Kgf/cm ² is required. However, when Portland cement is used as a binder, a curing period of 7 to 14 days is required until a predetermined strength is obtained, and the pellets are often pulverized while being held horizontally. [Means for Solving the Problems] The present inventors have conducted various studies in order to develop pellet strength in a short time and solve the above problems, and have finally completed the present invention. That is, the present invention is a quick setting agent for cold pellets comprising calcium aluminate, divalent metal hydroxide, and monovalent metal carbonate. The present invention will be explained in detail below. Calcium aluminates (hereinafter referred to as CA) used in the present invention include 3CaO・Al ₂ O ₃ , 12CaO・
7Al ₂ O ₃ , CaO・Al ₂ O ₃ , CaO・2Al ₂ O ₃ and CaO・
Examples include crystalline and amorphous materials such as 6Al ₂ O ₃ . When the CaO/Al ₂ O ₃ molar ratio in CA is high, rapid setting is strong;
When the CaO/Al ₂ O ₃ molar ratio is low, the rapid setting becomes weak.
Therefore, the CaO/Al ₂ O ₃ molar ratio is preferably 0.5 to 4.0, more preferably 1.0 to 2.5. Divalent metal hydroxide (hereinafter referred to as M(OH) ₂ )
Examples include calcium hydroxide, magnesium hydroxide, iron hydroxide, zinc hydroxide, manganese hydroxide, etc. Calcium hydroxide is economically preferred. The amount of M(OH) ₂ added is 10 parts by weight of CA100.
-200 parts by weight is preferred, and 50-150 parts by weight is more preferred. Monovalent metal carbonates (hereinafter referred to as M ₂ CO ₃ ) include sodium carbonate, potassium carbonate, etc., but sodium carbonate is preferred from the economic standpoint. The amount of M ₂ CO ₃ added is 10 to 100 parts by weight of CA.
100 parts by weight is preferred, and 20 to 50 parts by weight is more preferred. The reason why we decided to use CA, M(OH) ₂ and M ₂ CO ₃ together in the present invention is because the properties of pellets at high temperatures (hereinafter referred to as high temperature properties) are important when actually used in blast furnaces. ) becomes defective. That is, fine ore pellets need to have good pellet properties at room temperature and high temperature properties, and damage to the blast furnace becomes a serious problem especially when the alkali content in the ingredients is high. The alkaline content in cold pellets is approximately 0.1
It is preferable that the amount is less than % by weight. Furthermore, sulfur content such as SO ₃ and chlorine content both have a negative effect on the blast furnace. The present invention suppresses these harmful components as much as possible. A quick setting agent consisting of CA, M(OH) ₂ and M ₂ CO ₃ is used together with a hydraulic substance such as cement to granulate ore powder into cold pellets. Examples of the hydraulic substance include ordinary Portland cement, blast furnace cement, fly ash cement, silica cement, granulated blast furnace slag, and converter slag. From a physical standpoint, ordinary cement is preferable, but from an economic standpoint, it is preferable to use industrial by-products, and granulated blast furnace slag is even more preferable. The mixing ratio of the quick setting agent and the hydraulic substance of the present invention is preferably 1 to 20 parts by weight, more preferably 3 to 10 parts by weight, based on 100 parts by weight of the hydraulic substance. The amount of the hydraulic substance added is preferably 3 to 15 parts by weight, more preferably 5 to 12 parts by weight, per 100 parts by weight of fine ore. If the amount of the hydraulic substance added is less than this, the strength development will be poor, and if it is more than this, the content of the active ingredient will decrease and the benefits will decrease. The method of adding each component of the quick-setting agent and the hydraulic substance is not particularly limited, and the order of addition is not particularly limited. In order to improve the workability and strength properties of the kneaded product, commonly used cement water reducers, retarders and
Cement admixtures such as AE agents can be used together. In addition, monovalent sulfates, aluminates, hydrogen carbonates, phosphates, etc. can also be used in part. [Example] The present invention will be further explained in the following example. Example 1 The compositions were blended as shown in Experiment Nos. 6 to 15 in Table 1 and kneaded for 3 minutes using a mortar mixer (JISR-5201).
After that, it was poured into a 2 x 2 x 8 cm formwork and air-dried at 20°C. Handling time and compressive strength were measured. The results are shown in Table-2.

【table】

[Table] Note: Amounts are in parts by weight <Materials used> Ore powder: Hematite ore limestone: Commercial product Hydraulic substance A: Ordinary Portland cement, manufactured by Denki Kagaku Kogyo Co., Ltd. B: Granulated blast furnace slag
Brain 5020cm ² /g CA: Pulverized product Ca (OH) ₂ melted in an electric furnace, blown away and rapidly cooled. Calcium hydroxide, manufactured by Chichibu Lime Co., Ltd.
Slaked lime Na ₂ CO ₃ : Sodium carbonate, manufactured by Asahi Glass Co., Ltd., light ash

[Table] Next, the mixtures of Table 1 Experiment Nos. 7 and 10 were kneaded for about 3 minutes while adding water using a mortar mixer, and then a small amount of water was added using a pan-shaped granulator (inner diameter 60 cm). Pellets were granulated while dropping to obtain pellets with an outer diameter of 10 to 20 cm, and air-dried at 20°C for 7 days.
Put the granulated pellets into the crucible of the device shown in the drawing,
Reduction properties and shrinkage properties were measured at each temperature. The results are shown in Table-3. The measurement method is to put 200g of pellets into a crucible with an inner diameter of 4.8cm with ten 0.8cm holes drilled in the bottom, and about 30g of coke about 1.1cm in size to the top and bottom of the crucible.
Packed to cm thickness. The furnace was heated at a heating rate of 10°C/min in a nitrogen stream, held at 800°C for 10 minutes, and then a reducing gas of 30% CO and 70% N ₂ was flowed at 6.14 Nl/min at a rate of 5°C/min. The temperature was increased to 1500℃, and the temperature was kept constant at 1500℃ thereafter. The reduction rate was determined from the analysis values of CO and CO ₂ in the outlet gas.

〔Effect of the invention〕

As described above, when the cold pellet accelerating agent of the present invention is used, the process is extremely simple, as strength comparable to that of several days of curing can be obtained in a few hours compared to conventional cold pellets made only of ordinary Portland cement. It is economical and does not require much stockyard. In addition, it is expected that the high-temperature properties will be equivalent to or better than cold pellets made using ordinary Portland cement.

[Brief explanation of the drawing]

The drawing shows an example of an apparatus for measuring the high temperature properties of cold pellets. Code, 1...Gas flow meter, 2...Sampling box, 3...Thermocouple, 4...Reaction tube, 5...Graphite crucible, 6...Coke layer, 7...Cold pellet, 8...Contraction Meter, 9... Weight, 10... Differential pressure gauge, 11... Gas analyzer.

Claims (1)

[Claims] 1. Rapid setting agent for cold pellets consisting of calcium aluminate, divalent metal hydroxide, and monovalent metal carbonate.