JPH0742182B2 - Aggregation method of slaked calcareous particles - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for agglomerating slaked lime particles, and more particularly, to improve the runoff of slaked lime particles and suppress dust generation to prevent environmental pollution. TECHNICAL FIELD The present invention relates to a method for aggregating slaked calcareous particles in which fine particles of polytetrafluoroethylene are captured and aggregated by a web in the form of a spider web.

[0002]

BACKGROUND OF THE INVENTION Generally, calcareous compositions have a large number of uses such as neutralizers for acidic substances, fertilizers, bactericides or disinfectants, materials for civil engineering and construction, and chemical reaction agents. As an example of these, a calcareous fertilizer will be described, for example. Calcareous fertilizer is applied for the purpose of correcting soil acidity. The types thereof can be roughly classified into three types: calcium carbonate fertilizer obtained by crushing limestone, dolomite, etc., quick calcareous fertilizer having a grain size adjusted by calcination at about 1000 ° C, and slaked calcareous fertilizer obtained by hydrating quick lime.

These forms of fertilizer are used properly depending on the purpose of use. For example, the solubility in water is calcium carbonate (CaCO ₃ ), which is 1.4 to 1.5 mg / 100 g.
(20 ° C.), slaked lime (Ca (OH) ₂ ) is 126 mg / 100 g (20 ° C.), and there is a great difference in solubility.

The difference in solubility appears as the rate of neutralization reaction with acidic components in soil. Therefore, when comparing the calcium carbonate neutralizing agent and the slaked lime neutralizing agent, even if the particles are of the same degree, the slaked lime completes the neutralization reaction much faster.

On the other hand, quick calcareous fertilizer has almost the same reaction rate as slaked calcareous fertilizer if it has the same particle size as the former. However, for ease of handling, the particle size is generally in the form of granules or agglomerates having a size of about 1 to 5 mm.

[0006]

Granular quicklime is hydrated by the water content in the soil and changes to slaked lime. At this time, the water required for hydration is present in a much larger amount, so the slaked lime produced is not pulverized. Will be in an aggregated state. Slaked lime containing water undergoes a carbonation reaction almost simultaneously with hydration to produce calcium carbonate.

[0007] From this, the neutralization reaction rate of quicklime fertilizer is slower than that of powdered slaked lime fertilizer. In other words, slaked calcareous fertilizer has a higher rate of soil acidity correction than other forms of calcareous fertilizer, so it shows the effect almost as the theoretical value, but on the other hand, because of its high solubility, leaching due to rainwater etc. is severe, and the plant growth period Medium, it is not possible to maintain a suitable acidity.

For this reason, in the case of strongly acidic soil, it is customary to first use slaked lime to correct the target acidity, and then add or simultaneously fertilize other forms of calcareous fertilizer.

In general, since the slaked lime composition is a fine powder, it is easily scattered and has a high dust generation property. When it is handled, it may adhere to clothes, skin, etc., or may be inhaled into the respiratory system. However, it has problems such as causing alkali damage.

As a means for solving the above-mentioned problems, the present inventors have found that a slaked lime composition in which hydrated lime or calcined dolomite hydrate particles are trapped in a reticulated state by fibrillated PTFE and agglomerated is washed out. It has been found that it shows an excellent effect on the improvement, but in order to fibrillate PTFE, fibrillating PTFE is added to the powder by adding fibrillating PTFE, mixing and heating the mixture to apply compression / shearing force. In order to form PTFE, it requires an external heating device and heating energy for the powder mixture and, if not heated, requires a long compression / shear time for fibrillation of PTFE, Or PTF
There is a problem that it is necessary to increase the amount of E added.

[0011]

The present invention is a method for solving the above-mentioned various problems, and the gist of the invention is that the hydrated lime particles do not impair the rapid acidity improving ability and sharply improve the acidity. Solid particles of polytetrafluoroethylene are dispersed in quick lime or calcined dolomite or a mixture of both and water in an amount required for the hydration exothermic reaction in order to reduce the property and dust generation and to maintain the durability. The dispersion is added to quicklime or calcined dolomite or a mixture of both and stirred, and the polytetrafluoroethylene particles are fibrillated by the compression / shear action by the heat of hydration reaction and stirring, and the slaked lime particles produced by the fibrils are respectively generated. It is a method of agglomerating slaked calcareous particles, which is captured by a web of webs and agglomerated lightly.

The PTFE used in the present invention has a property that when added to a fine powder and subjected to an appropriate operation, the PTFE itself finely fibrillates without changing the chemical properties of the fine powder, and preferably PTFE. PTFE
An aqueous dispersion of colloidal particles is used.

When hydrating any one of quick lime and dolomite quick lime or a mixture thereof, a sufficient amount of water to hydrate all of the raw materials slaked lime and dolomite quick lime to form hydroxide. Alternatively, PTFE may be dispersed in advance, or an aqueous dispersion of PTFE colloidal particles may be added to a sufficient amount of water to form part of the hydroxide, and the shortage of water may be added by another system. May be. In short, PT
The FE particles should be uniformly dispersed in the raw material.

By hydrating quicklime using this PTFE colloidal aqueous dispersion, the hydration reaction heat and P
TFE can be fibrillated, and the produced slaked lime fine particles and unreacted raw material particles can be confined in the web of spider webs of the fibrils to form aggregates of slaked lime and unreacted raw material particles as described above. , In this case, the heating operation uses reaction heat, so it is more energy-saving than the case of adding PTFE directly to slaked lime described above, and since the dispersion of PTFE is extremely uniform and carried out in a short time, the amount added In addition, this is an advantageous method that requires less processing time.

The slaked lime composition obtained by the method of the present invention is capable of confining fine particles of slaked lime with a spider web of fine PTFE fibrils, which is also confirmed by an electron microscope. This apparently has the effect of making the slaked lime aggregate, so that it seems that the fine powder particles are confined in the net made of fine fibrils, not just the fine agglomeration of fine powder like granulation. Since it is an extremely light powder aggregate in a stable state, it has almost the same effect as slaked lime not treated with PTFE, and obtains a slaked lime composition that prevents dusting and runoff. Can be done.

[0016]

EXAMPLES Examples of the present invention and comparative examples for understanding the superiority of the present invention will be described below.

Example 1 An aqueous suspension of PTFE (PTF) was added to 500 g of slaked lime.
0.17 g and 0.83 g (containing PTFE in an amount of 0.01% by weight and 0.05% by weight in terms of PTFE solid content) were added, and after lightly mixing in a mortar, It was heated at 100 ° C. for 3 hours, directly kneaded in a mortar for 5 minutes, and compressed / shearing force was applied to fibrillate PTFE to obtain a product in which slaked lime had cohesiveness. These products were subjected to a soil acidity correction test with slaked lime not subjected to PTFE treatment as a symmetry. 7.5 g of the above slaked lime was added to 7 kg of air-dried soil, and the mixture was mixed for 20 mm per day.
Water is sprayed every day at a rate of 1 / cm ² for 1 day, 3 days, 7 days, 14
After 28 days, the pH of the soil and its replaceable calcium were measured. The results are shown graphically in FIGS. 1 and 2, respectively. From this figure, the one with PTFE added is
It was confirmed that the acidity correction power was the same as that of the conventional one, and the loss due to water sprinkling was small, and the acidity correction power of the soil was exhibited for a long time. In the figure, ⊚ mark indicates no treatment, ○ mark indicates that 0.01% PTFE was added, and △ mark indicates PTFE0.0.
5% addition is shown. Example 2 10.0 kg of quicklime was put into a super kimisa, and PTF was added.
A hydration reaction was carried out using a liquid obtained by suspending 21.7 g of an aqueous suspension of E (containing PTFE as a solid content of 30% by weight) in 4.5 kg of water. In this case, PTFE is 0.065% by weight with respect to quicklime (0.05% by weight with respect to slaked lime). During the reaction, mixing and stirring were performed twice for 1 to 2 seconds intermittently.
When the temperature of the slaked lime decreased to 90 ° C., 13 kg of a dust-free slaked lime product having an appropriate aggregation effect could be obtained by simply applying a compression / shearing force for 30 seconds at a low speed.

Therefore, it was found that the amount of PTFE required for appropriately improving the coagulation of the slaked lime particles produced by this treatment method is remarkably small as compared with the comparative examples shown below.

Comparative Example 1 13.0 kg of slaked lime was heated to 50 ° C.
Pour into a 0 l super mixer (Kawata Manufacturing Co., Ltd.), add 6.5 g of powdered PTFE (0.05% by weight to slaked lime), stir for 30 seconds, and apply compression / shear force.
The degree of fibrillation of E was small and almost the same as that of ordinary slaked lime was not recognized. After stirring for another 3 minutes in the same manner, no change was observed. Then PTFE
19.5 g (total of 26 g, 0.2% from the beginning) was added, and the mixture was stirred for 1 minute to obtain a slaked lime product aggregated to a degree. Therefore, this treatment method requires a large amount of PTFE in order to moderately improve the aggregation of the slaked calcareous particles.

[0020]

As described above, the method for agglomerating slaked calcareous particles according to the present invention is a method in which solid particles of polytetrafluoroethylene are mixed with quicklime or calcined dolomite or a mixture of both in an amount required for hydration exothermic reaction. Disperse in water, add the dispersion to quicklime or calcined dolomite or a mixture of both and stir, fibrillate the polytetrafluoroethylene particles by compression / shear action by heat of hydration reaction and stirring, and by this fibril, Since the generated slaked lime particles are respectively captured and aggregated by the web of spider webs, fine slaked lime particles are particularly fine PTF.
Confine in the cobweb-like net made of fibrils of E, that is, the produced slaked lime fine particles and unreacted raw material particles are confined in the fibril's cobweb-shaped net and the slaked lime and unreacted raw material particles It is possible to form an aggregate, thereby achieving an excellent effect that it is possible to efficiently produce a slaked lime composition that prevents dusting and runoff while achieving energy saving without applying heat from the outside. Play. Further, when using the slaked calcareous composition obtained by the method of the present invention, for example, as a fertilizer, neutralization of acidic substances, sterilizing and disinfecting agents, lime stabilization treatment of soft soil and solidification, etc. It is especially effective in terms of preventing environmental pollution and safety to the human body.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between pH and the number of days elapsed.

FIG. 2 is a graph showing the relationship between the number of elapsed days and the amount of replaceable lime.

[Figure 1]

[Fig. 2]

Claims (1)

[Claims] 1. Solid particles of polytetrafluoroethylene are dispersed in quick lime or calcined dolomite or a mixture of both in water in an amount required for an exothermic hydration reaction, and the dispersion is mixed with quick lime or calcined dolomite or a mixture of both. In addition to the above, the polytetrafluoroethylene particles are fibrillated by the heat of hydration reaction and the compression / shearing action by stirring, and the slaked lime particles produced by these fibrils are captured and aggregated by a web of webs. A method for aggregating slaked calcareous particles, comprising: