JP2015140287A - Production method of aqueous suspension of calcium hydroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of lime milk having a similar viscosity or the like to a conventional one, even when the use amount of coke and the amount of middle pressure steam to be used for preparing warm water to be reacted with quicklime are reduced.SOLUTION: In a production method of an aqueous suspension of calcium hydroxide, limestone is thermally decomposed with combustion heat of coke in a limekiln to produce quicklime, which is reacted with warm water to produce an aqueous suspension of calcium hydroxide. The amount of the coke to be used for thermal decomposition of the limestone is reduced from a conventional use amount of 12.5 pts.wt. relative to 100 pts.wt. of the limestone by 3.0-8.0 wt.%, and the temperature of the warm water to be reacted with the quicklime is lowered to 50-70°C.

Description

  The present invention relates to a method for producing a calcium hydroxide aqueous suspension capable of reducing the amount of coke used. This calcium hydroxide aqueous suspension has a low viscosity, facilitates pipe transportation, neutralization treatment, etc. These various processes can be performed efficiently. Therefore, the high-concentration calcium hydroxide aqueous suspension of the present invention is suitably used as a neutralizing agent for various acidic substances, particularly acidic wastewater, and other agents for preventing adhesion of molten metal from a melting furnace to a tray. It is also useful as an anti-adhesive agent for metal surfaces other than the welded portion of the molten metal scattered during electric welding, as a filler for paints and plastics, a wall material for construction, and a ground improvement material.

  The aqueous calcium hydroxide suspension first burns limestone and coke in a lime furnace, decomposes the limestone into quick lime (CaO) and carbon dioxide, and mixes the hot lime particles with hot water in the reactor, It is manufactured by reacting (see, for example, Patent Document 1).

  When limestone and coke are burned in a lime furnace, if the brands of coke are different, the quality of quicklime will vary, the specific surface area of the quicklime will increase, and excess hot water will be mixed and reacted with the quicklime particles. The high concentration calcium hydroxide aqueous suspension (3 mol / L or more) obtained in this manner has an increased viscosity and makes it difficult to transport the suspension by piping. Therefore, the amount of coke used is 10 parts per 100 parts by weight of limestone. In addition to a large amount of ~ 15 parts by weight, limestone is pyrolyzed, so-called “hard-fired quicklime” is produced to suppress variations in quicklime quality.

Japanese Patent Laid-Open No. 10-291820

  The present invention provides a method capable of producing a desired aqueous calcium hydroxide suspension (3 mol / L or more) even when the amount of coke used is reduced.

  Even if the amount of coke used in the lime furnace is reduced to produce a so-called “soft calcined lime” and a diluted calcium hydroxide aqueous suspension (3 mol / L or more), the viscosity is so much. When the temperature of mixing and reacting in the reactor is lowered from the conventional 75 ° C. to 50-70 ° C. when the hot lime particles are reacted with the hot lime particles, the calcium hydroxide can be used. Can suppress the viscosity increase of aqueous suspension, reduce the amount of steam used to produce hot water to be supplied to the reactor, suppress the increase in viscosity of lime milk in the reactor, and enable stable operation As a result, the present inventors have completed the method for producing an aqueous calcium hydroxide suspension (3 mol / L or more) according to the present invention.

  That is, the present invention relates to a method of producing quick lime by pyrolyzing limestone with the combustion heat of coke in a lime furnace, and reacting the quick lime with warm water to produce an aqueous calcium hydroxide suspension. The amount of coke used for pyrolysis is reduced by 3.0 to 8.0% by weight (11.5 to 12.1 parts by weight) with respect to 12.5 parts by weight of the conventional amount with respect to 100 parts by weight of limestone. In addition, the present invention relates to a method for producing an aqueous calcium hydroxide suspension characterized in that quick lime and hot water are reacted at 50 to 70 ° C.

  Hereinafter, the aqueous calcium hydroxide suspension is abbreviated as lime milk.

  A method for producing lime milk (3 mol / L or more) will be described with reference to FIG.

First, limestone and coke are simultaneously charged into the lime furnace, combustion air is supplied, and the limestone is decomposed into quick lime (CaO) and carbon dioxide (CO ₂ ) at a temperature of about 1000 ° C. by the coke combustion action. Produces quicklime.

  Quicklime is supplied to the next reactor, and industrial water is mixed with warm water heated with steam to react to produce lime milk.

  High-concentration lime milk (3 mol / L or more) produced in the reactor is stored in a tank, and unreacted quicklime and impurities are discarded through a separate disposal line.

  Limestone having a size of 20 to 100 mm is used as the limestone supplied into the lime furnace, and coke having a small particle diameter of several mm to 50 mm with good combustion efficiency is used.

  The size of the lime furnace, the input amount of limestone into the lime furnace, and the input amount of coke are determined by the production amount. Usually, when the furnace inner diameter is 4 to 8 m and the height is 30 to 50 m, The input amount is several hundred tons / day, and the input amount of coke is several tens tons / day.

  The material of the lime furnace is usually refractory bricks inside and covered with steel plates on the outside.

  The produced quicklime is discharged from the lower part of the lime furnace to the outside of the furnace and sent to the reactor.

  In the quick lime manufacturing method, the ratio of limestone and coke put into the lime furnace is usually 10 to 15 parts by weight of coke with respect to 100 parts by weight of limestone, but the cost of coke is a large proportion of the total quick lime manufacturing cost. It is desired to reduce the amount of coke used.

  Then, in the manufacturing method of this invention, the amount of coke used for the thermal decomposition of limestone is 3.0 to 8.0 weight% with respect to 12.5 weight part of conventional usage with respect to 100 weight part of limestone. It is characterized by reducing (11.5 to 12.1 parts by weight).

  When the amount of coke input is reduced, Ig-Loss (%), CaO content (%), and calcining degree (%) of quicklime are not changed, but the viscosity of lime milk produced by the reaction between quicklime and hot water is almost the same. It will not rise and trouble will not occur in piping transportation.

  The reduction rate of the amount of coke used in the present invention is 3.0 to 8.0% by weight. The reason for this is that if the amount is less than 3.0% by weight, the reduction effect is small, and if it exceeds 8.0% by weight, the quick lime inlet of the reactor is blocked and the number of operations corresponding to this trouble increases, which increases the labor cost. This is because it is undesirable.

  When warm water is reacted with quicklime particles, the temperature of mixing and reaction in the reactor is lowered from the conventional 75 ° C. to 50 to 70 ° C.

  If it is less than 50 ° C., the reaction rate of quick lime in the reactor is too low, which is not preferable. If it exceeds 70 ° C., the viscosity of lime milk increases, and not only the inlet of lime milk in the reactor is blocked. The amount of steam used to produce hot water supplied to the reactor increases, and the reaction rate of quick lime in the reactor is too high, making it difficult to control the reaction rate.

  According to the method for producing lime milk of the present invention, even if the amount of coke used in the lime furnace is reduced by 3.0 to 8.0% by weight, lime milk having the same viscosity as that of conventional lime milk can be produced. Steam for producing hot water that not only suppresses the increase in viscosity of lime milk but also reduces the viscosity of lime milk by mixing the quick lime and water and reducing the reaction temperature from the current 75 ° C. to 50 to 70 ° C. The amount of use can be reduced.

It is a process figure which manufactures the lime milk of this invention. It is a figure which shows the lime furnace which manufactures quicklime.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples.

Reference example 1
Lime milk was produced in a conventional manner.

  The structure of the lime furnace is shown in FIG.

  Limestone and coke are charged into the furnace hopper (1) at the top of the lime furnace at a ratio of 12.5 parts by weight of coke to 100 parts by weight of limestone. A rotatable shooter (2) is attached to the lower part of the furnace hopper (1), and limestone and coke are uniformly supplied to the lime furnace body (3) by the shooter (2).

  The upper part of the lime furnace body (3) is a preheated part (4). When the temperature on the furnace reached 170 ° C., limestone and coke were simultaneously charged into the lime furnace body (3). When the coke reaches several hundred degrees Celsius in this preheating portion (4), it ignites, descends while burning, and reaches the firing portion (5).

  When the temperature of the calcining part (5) reaches 900 ° C. or more due to the combustion of coke, the limestone begins to decompose into quick lime and carbon dioxide, and the calcining part (5) reaches an average temperature of about 1000 ° C.

  Quick lime is generated in the calcined part (5).

  The produced quicklime exchanges heat with the air sent from the furnace bottom (6) of the lime furnace, descends the air cooling part (7) of the lime furnace while being cooled, and reaches the furnace bottom (6).

  The quicklime that has reached the furnace bottom (6) is supplied to the reactor through a stone discharging device.

  In the reactor, quick lime and 75 ° C. warm water were reacted to separate lime milk, unreacted quick lime and impurities.

  The concentration of lime milk at this time was 3.0 mol / L.

  At this time, it was difficult to adjust the viscosity of the lime milk because the reaction rate was high, and the lime milk inlet of the reactor was often blocked due to an increase in the viscosity of the lime milk, making long-term stable operation difficult.

Example 1
The amount of coke used is 11.9 parts by weight with respect to 100 parts by weight of limestone (the coke use reduction rate is 4.3% with respect to the conventional amount of use of 12.5 parts by weight with respect to 100 parts by weight of limestone). And the lime milk was manufactured by the same method as the reference example 1 except having set the hot water temperature made to react with quicklime to 70 degreeC.

  As the temperature of this hot water is reduced from 75 ° C. in Reference Example 1 to 70 ° C., the steam intensity per ton of lime milk is reduced from 0.216 tons (Reference Example 1) to 0.208 tons, The reduction rate was 3.7%.

  In the reactor, quick lime and 70 ° C. warm water were reacted to separate lime milk, unreacted quick lime and impurities.

  The concentration of lime milk at this time was 3.0 mol / L.

  The viscosity of this lime milk did not increase as in Reference Example 1 above, and long-term stable operation was possible.

Example 2
The amount of coke used is 11.8 parts by weight with respect to 100 parts by weight of limestone (the coke use reduction rate is 5% with respect to the conventional amount of use of 12.5 parts by weight with respect to 100 parts by weight of limestone), Lime milk was produced by the same method as in Reference Example 1 except that the temperature of the hot water reacted with quicklime was 70 ° C.

  As the temperature of this hot water is reduced from 75 ° C. in Reference Example 1 to 70 ° C., the steam unit per ton of lime milk is reduced to 0.208 tons as in Example 1, and the reduction rate is 3 It was 7%.

  In the reactor, quick lime and 70 ° C. warm water were reacted to separate lime milk, unreacted quick lime and impurities.

  The concentration of lime milk at this time was 3.0 mol / L.

  The viscosity of this lime milk did not increase as in Reference Example 1 above, and long-term stable operation was possible.

Example 3
The amount of coke used is 11.7 parts by weight with respect to 100 parts by weight of limestone (the coke use reduction rate is 6% with respect to the conventional amount of use of 12.5 parts by weight with respect to 100 parts by weight of limestone), Lime milk was produced by the same method as in Reference Example 1 except that the temperature of the hot water reacted with quicklime was 70 ° C.

  As the temperature of this hot water is reduced from 75 ° C. in Reference Example 1 to 70 ° C., the steam unit per ton of lime milk is reduced to 0.208 tons as in Example 1, and the reduction rate is 3 It was 7%.

  In the reactor, quick lime and 70 ° C. warm water were reacted to separate lime milk, unreacted quick lime and impurities.

  The concentration of lime milk at this time was 3.0 mol / L.

  The viscosity of this lime milk did not increase as in Reference Example 1 above, and long-term stable operation was possible.

Example 4
The amount of coke used is 11.5 parts by weight with respect to 100 parts by weight of limestone (the coke use reduction rate is 8% with respect to the conventional amount of use of 12.5 parts by weight with respect to 100 parts by weight of limestone), Lime milk was produced by the same method as in Reference Example 1 except that the temperature of the hot water reacted with quicklime was 70 ° C.

  As the temperature of this hot water is reduced from 75 ° C. in Reference Example 1 to 70 ° C., the steam unit per ton of lime milk is reduced to 0.208 tons as in Example 1, and the reduction rate is 3 It was 7%.

  In the reactor, quick lime and 70 ° C. warm water were reacted to separate lime milk, unreacted quick lime and impurities.

  The concentration of lime milk at this time was 3.0 mol / L.

  The viscosity of this lime milk did not increase as in Reference Example 1 above, and long-term stable operation was possible.

  The method for producing lime milk of the present invention can suppress an increase in viscosity of lime milk to be produced even if the amount of coke used is reduced, and the temperature of hot water to be reacted with quick lime is lowered and used for hot water adjustment. The amount of steam to be used can be reduced, the energy cost of lime milk production can be reduced, and it can be widely used in the lime milk production field.

1: Furnace hopper 2: Shooter 3: Lime furnace body 4: Preheating part 5: Firing part 6: Furnace bottom 7: Air cooling part

Claims (1)

Coke used for pyrolysis of limestone in a method of producing limestone by pyrolyzing limestone with the heat of combustion of coke in a lime furnace and reacting the quicklime with hot water to produce an aqueous calcium hydroxide suspension The amount is 11.5 to 12.1 parts by weight with respect to 100 parts by weight of limestone, and the resulting quick lime and hot water are reacted at 50 to 70 ° C. Method.

Images