JPS6134873B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for solidifying incinerated ash discharged from the incineration process of municipal garbage, sludge, sludge, etc., and fine powder waste such as dust generated from various gas processing processes. In general, direct landfilling and ocean dumping have been the mainstream methods for treating or disposing of these fine powder wastes, but since they are fine powders, they are difficult to handle, and they are prone to scattering and spilling during transportation and at landfill sites. There were some points that needed to be improved. In addition, various solidification technologies have been proposed to facilitate the handling of these fine powder wastes and prevent the elution of heavy metals, etc., but conventional solidification techniques involve adding solidification agents such as cement or asphalt. There were methods such as heating, melting, and then cooling and solidifying (melting method). Among these methods, the method of adding a solidifying agent is effective in containing harmful substances and improving the soil quality of a landfill, but the cost of the solidifying agent is high, and the method of adding a solidifying agent is effective in containing the hazardous substances and improving the soil quality of the landfill. It is difficult to do so. On the other hand, the melting method is an excellent method because the volume of the waste is significantly reduced and the waste becomes granular or lumpy, so it is easy to handle and can contain hazardous substances such as heavy metals. The problem is that it requires a large amount of energy to be heated. As described above, there are many problems that need to be solved with conventional waste solidification technologies, and the current situation is that there is an urgent need to develop new technologies from the viewpoint of resource and energy conservation. In view of the current situation, the present invention aims to provide an effective treatment method that can solidify fine powder waste in a low-cost and energy-saving manner, making it easier to handle and paving the way for reuse. That is. The present invention involves molding fine powder waste in the presence of a calcium component by adding and mixing at least one of a solidification accelerator and a cyclic agent as necessary, and then molding the waste in water at a temperature of 50°C or higher or at a temperature of 50°C or higher under atmospheric pressure. It is characterized by being left and cured in steam at a temperature of 50°C or higher for 3 days or more. The present invention was completed by clarifying that curing conditions are important in the solidification treatment of finely powdered waste. In other words, the inventors have found from numerous experimental results that steam or water is better for the curing atmosphere than dry air at a temperature of 50°C or higher.
It was also confirmed that a curing time of 3 days or more is preferable. In the present invention, the presence of a calcium component is an essential condition. If the fine powder waste contains a sufficient amount of calcium component, it is not necessary to add the calcium component, but if it is insufficient, It is preferable to add a calcium component in advance so that the calcium content in the mixture is 10% by weight or more (in terms of quicklime, hereinafter "%" is expressed on a weight basis) or more. In addition, as for the form of the calcium component to be added, calcium carbonate, quicklime, calcium sulfate, calcium chloride, slaked lime, etc. may be added singly or in combination, but among these, slaked lime is most suitable; It is also possible to use the residue obtained by incinerating various types of sludge that have been dehydrated using. In addition, if the calcium content is sufficient but hard to solidify, silicic acid materials such as diatomaceous earth, silica, silicate clay, silica stone, quartz, silicate glass, water glass, and sand can be used as a solidification accelerator as necessary. substances, clays such as kaolinite, bentonite, pearlite, zeolite, hallosite, aluminum compounds such as aluminum hydroxide and aluminum oxide,
Alternatively, it is effective to add an appropriate amount (for example, 1 to 30%, preferably 10 to 30%) of waste such as fly ash, red mud incineration ash, etc. containing the above substances singly or in combination. . Furthermore, when treating fine powder waste containing a large amount of hexavalent chromium as a heavy metal, it is also effective to add a reducing agent in advance. In this case, reducing agents include salts of divalent iron ions, sulfites or sulfites, quartz, carbon black, coke husks, organic carbons such as lignin, metals such as magnesium, calcium, zinc, etc., or wastes containing these. It is recommended to use one or more of the following. The amount added varies depending on the case, but is generally preferably about 0.5 to 20%. The fine powder waste whose chemical composition has been adjusted in this way is molded to increase the number of points of contact between the fine powders, and this molding method can use conventional techniques such as pressurization, rolling, extrusion, etc. . Depending on the molding method, a binder may not necessarily be necessary, but in the present invention, using water as a binder is advantageous for the solidification reaction. in this case,
The amount of water to be added is the optimum amount for each molding method, but in general, in the case of rolling granulation, 20 to 30
%, and in the case of compression molding, about 5 to 15% is effective. The thus formed waste material is heated to 50% at atmospheric pressure.
Solidifies if left in water at temperatures above ℃ or steam at temperatures above 50℃ for 3 days or more. The optimal curing temperature and curing time vary greatly depending on the composition of the waste, etc., but generally 60 to 80°C and 3 to 28 days are economically preferable conditions. In addition, in the present invention, curing in water and curing in steam may be performed together. The mechanism of the reaction that occurs during the curing process is not necessarily clear because it is difficult to identify and quantify the reaction products, but it is possible that calcium silicate hydrate or calcium aluminate hydrate is produced and that fine powders interact with each other due to this. It is thought that the development of strength based on bond progresses. As described above, in the present invention, after the fine powder waste is molded in the presence of a calcium component with addition and mixing of at least one of a solidification accelerator and a reducing agent as required, the pressure is atmospheric pressure and 50°C or higher. By leaving it in water or steam at a temperature of 50℃ or higher for more than 3 days,
It is possible to easily obtain a strong solidified product, improve the hand linkability of the powder, significantly reduce the amount of landfill space, and in some cases, make it possible to reuse it as roadbed material or aggregate. , post-processing can be simplified, and if the heat and steam generated from the waste incineration process are used for heating, it becomes a more energy-saving solidification method, which has an extremely useful effect in preventing pollution, and solves the problems of the past. It also has the advantage of being able to accurately eliminate waste materials, as well as being inexpensive and economical to dispose of. Next, examples of the present invention will be shown. Example 1 Sludge generated at a certain sewage treatment plant was dehydrated by adding slaked lime and ferric chloride, dried, and then incinerated. The composition of incinerated ash was as follows.

[Table] This incinerated ash was mixed with 15% water based on the weight of the incinerated ash, and compressed into a disk shape of 20 mm in diameter and 20 mm in length at a pressure of 1000 Kgf/cm ² , and steamed at various temperatures under atmospheric pressure. A solidified product was obtained by curing for two weeks. The strength of the obtained solidified product and the results obtained when it was left in dry air at each temperature are also listed for reference.

[Table] From the table above, it can be seen that the strength of the solidified material increases significantly when it is cured in steam at a temperature of 50°C or higher. Example 2 EP dust from a certain municipal waste incinerator was mixed with 10% slaked lime as a calcium component and 10% silica powder as a solidification accelerator, and a small amount of water was added and granulated using a rolling granulator to make it hydrated. Green pellets with a yield of 25% were obtained. Table 2 shows the results of curing these green pellets in water and steam at 50°C under atmospheric pressure, and the figure shows the change in solidified strength over time when curing in water at different temperatures. From Table 2, it can be seen that the strength increases in the same way if the curing time is 3 days or more in water or steam. Furthermore, it can be seen from the drawing that a solidified product with high strength can be obtained under curing conditions of 50°C or higher for 3 days or longer.

[Table] Example 3 The chemical composition of finely powdered incineration ash obtained by dehydrating, drying, and incinerating sludge discharged from a certain factory was as follows.

[Table] 0.5% ferrous sulfate as a reducing agent and water were added to this sample and granulated using a rolling granulator to obtain green pellets with a water content of 20%. Table 3 shows the strength of the solidified product obtained by leaving the green pellets in water at 70°C under atmospheric pressure for 3 days and the amount of hexavalent chromium eluted. Note that the strength was measured for those with a diameter of 8 to 12 mm.

[Table] Table 3 shows that adding a reducing agent and curing in water increases the strength of the solidified product and reduces the amount of hexavalent chromium eluted.

[Brief explanation of the drawing]

The drawing is a graph showing the results of an example of the present invention.

Claims (1)

[Claims] 1. Processing fine powder waste in the presence of a calcium component,
A fine powder that is characterized by being molded by adding and mixing a solidification accelerator and/or reducing agent as necessary, and then left and cured in water or steam at a temperature of 50°C or higher for 3 days or more under atmospheric pressure. Waste solidification treatment method. 2. If the molding process is performed in combination with water, the amount of water added is 20% to 30% of the dry weight of the waste in the case of rolling granulation, and 5% in the case of compression molding. % to 15%, respectively. 3. The solidification treatment method according to claim 1 or 2, wherein the treatment time of the curing step is 3 days to 28 days. 4 Adjust the amount of the reducing agent added to 0.5% or more of the waste.
20% (by weight) of claims 1 and 2
The solidification treatment method described in Section 3 or Section 3.