JPS5925759B2 - Calcareous fertilizer manufacturing method - Google Patents

Description

[Detailed Description of the Invention] This invention, when producing lime cake from lime cake discharged from a beet sugar manufacturing factory, mixes surplus sludge discharged from the wastewater treatment equipment of the same beet sugar manufacturing factory and composts it. The present invention relates to a method for producing calcareous fertilizer which is an additive in the state of the art.

In the production of beet sugar, sucrose, refined sugar, etc., in order to remove impurities from the sugar solution, milk of lime or calcium saccharate milk is added to make it alkaline, and carbon dioxide gas is blown into the solution to form precipitated carbonic acid. The so-called carbonation method, which generates lime and adsorbs and removes impurities, has been adopted.

The carbonated lime produced at this time is discharged as lime cake.

In addition, in beet sugar manufacturing factories, a large amount of wastewater is discharged due to the transportation and washing of the raw material sugar beet, and this is combined with wastewater from the manufacturing process to produce high BOD wastewater, so wastewater treatment is carried out using the activated sludge method. The excess sludge generated at that time is also discharged.

The amount of lime cake and surplus sludge are both large, and if left as they are, they will rot, so their disposal becomes an extremely big problem in factories.

For this reason, various methods have been proposed for the treatment of these wastes, such as drying lime cake and spreading it on fields to adjust acidity,
As described in No. 9-16307, lime cake is dehydrated and granulated to produce a calcareous fertilizer.

However, the former is scattered by the wind after being sprayed, causing secondary pollution.
The latter may collapse depending on storage conditions, or solidify due to repeated moisture absorption and drying, leading to loss of utility value.

Furthermore, surplus sludge has no particular use and is usually treated at a large amount of expense.In short, no method has been developed for completely effective use of the surplus sludge.

The inventors have spent many years researching the treatment of the above waste, and found that by mixing lime cake from a beet sugar factory with excess sludge, adjusting the moisture content and granulating it, and drying it, the sludge becomes a binder and becomes a strong solid. After learning about this, we produced granular limestone fertilizer from lime cake and excess sludge, and have been conducting research into a fertilizer that has long-term fertilizing effects without being blown away by the wind after being applied.

However, when lime cake is mixed with sludge and granulated and dried to form a solid granule, calcareous fertilizer is used in large quantities to correct the acidity of acidic soil. Fermentation occurs in the field, consuming oxygen in the rhizosphere and inhibiting root respiration, and organic acids produced during decomposition have defects that reduce the ability of plant roots to absorb nutrients.

For this reason, the inventors conducted further research in order to create a calcareous fertilizer from lime cake to which sludge without such defects was added, and added surplus sludge to lime cake, mixed it, and granulated it. This problem was solved by fermenting under aerated conditions before drying, composting the organic matter, and then drying it. Fermentation reduces the hardness of granules, but it is a practical problem for mixtures within a certain range. Also, if the solids ratio of the mixture is 100 to 100 to 100 to 100 to 400 for excess sludge, the composition will change due to fermentation, and the C2N ratio will be in the ideal range of 20 to 40. Also, the lime content makes it a good calcareous fertilizer that satisfies the conditions for a calcareous fertilizer.

The lime cake used in this invention is the dregs obtained during the first carbonation and the second carbonation, or a mixture thereof, and an analytical example thereof is shown in Table 1.

Table 1 (per solid content) Organic matter CaOP2O5K2O Total nitrogen 7.0% 49.4% 1.27% 0.30% 0.
36%The main component is carbonate lime, and when compared with agricultural carbonate lime, it is characterized by a high P2O5,20 and total nitrogen content.

Further, the surplus sludge to be added is obtained by concentrating sludge discharged from wastewater treatment equipment of a beet sugar manufacturing factory using a concentrator, and dewatering or not dehydrating the sludge, and usually has a water content of 75 to 98%.

An example of that analysis is shown in Table 2.

Table 2 (per solid content) Organic matter CaOP2O5K2O Total nitrogen 73.5% 9.6% 3.25% 4.08% 76
84%, which is a significantly higher amount of potash than sludge obtained from biological treatment of sewage or other industrial wastewater.

In this invention, the lime cake and the excess sludge are mixed, granulated, and then fermented.

For this reason, the moisture content is first adjusted so that granulation is easy during mixing and does not interfere with fermentation, but according to research by the inventors, the third
As shown in the table, the preferred moisture range was found to be 25-40%.

If the moisture content is less than 25%, fermentation will be poor and
If the moisture content is higher than 0%, the granules will be softened and deformed during fermentation, which will impede aeration.

The water content during the mixing may be prepared by drying either or both of the lime cake or excess sludge, or by adding sawdust, rice husk, etc. during mixing.

It is preferable to perform the above mixing at low speed, and suitable devices include a spiral mixer, kneader, ribbon mixer, dough mixer, etc., and devices for granulating after mixing include, for example, a screw extrusion type granulator. , blenders, granulators, and drum granulators can also be used.

When granulating, granules with a diameter of 2 to 10 mrn can be used, and 5 to 10 mrIL is particularly preferable. If the granules are too large, it will take time to compost to the inside, and if the granules are too small, ventilation during fermentation will be inhibited, so care must be taken. .

The mixing ratio of lime cake and excess sludge can be set to a desired ratio, but it must be determined by taking into account the fertilizer effect after fermentation. The amount of the former is preferably 100 to 10 to 40 of the latter in terms of solid matter.

Now, 100 parts of the lime cake solids are thoroughly mixed with 1 to 40 parts of the surplus sludge solids, granulated using a granulator, and then put into a fermentation tank and subjected to sedimentary fermentation while being aerated. Shown in the table.

As is clear from Table 4, if the amount of excess sludge added is too small, the hardness after fermentation will be low and it will become powder, making it difficult to spread.

However, when it exceeds 40%, the C/H ratio becomes extremely low.
Moreover, the lime content is reduced, reducing its value as a lime fertilizer.

Therefore, it is preferable that the amount of excess sludge solids is about 10 to 30 per 100 parts of lime cake solids.

When mixed in this way, after fermentation, the C/N will be in the range of 20 to 40, which is desirable for compost, and the lime content will also be 40.
% or more.

This means that even if it absorbs moisture from the atmosphere, the lime content is 35%.
% or more, satisfying the requirements for calcareous fertilizer.

Furthermore, the basic substitution capacity is 12 to 13 meq/100r,
Since the humic acid content is 3 to 4%, which is about 115% of that of general compost, most of the organic matter is composted through fermentation.

For the fermentation in this invention, sedimentary aeration fermentation is most suitable, and fermenters such as a stationary batch type, a screw set, a scoop type, and a rotary kiln type can be used.When carrying out the fermentation, the granules of the mixture are filled into the fermenter. 10 while ventilating
Fermentation is carried out both in and out of the day.

As fermentation progresses, the temperature of the product rises, and the initial moisture level increases by 10 to 3.
0% transpires and ripening is completed.

After ripening, it is dried to the desired moisture content, stored in a warehouse, and sprayed on fields as needed.The obtained product has good storage stability, for example, when stored for 40 days at 75% humidity, the hardness is 2.
20-2640 Yu/crl, humidity 100%, temperature 30
Even if stored at ℃ for 40 days, no mold will appear.

This will be explained below using examples.

Example Lime cake (50% moisture) produced as a by-product in the sugar beet manufacturing process
, an IS with a flow area of 0.62 m and a pressure of 15 kg/ffl.
The water was dehydrated by supplying 65 liters of water per hour to a D-type water filter (trade name; manufactured by Ishigaki Kiko).

The water content of the dehydrated cake obtained here was 35%.

It was air-dried at room temperature to a moisture content of 15%, and the composition was as shown in Table 5.

Add the excess sludge shown in Table 6 to the above lime cake at a solid content ratio of 100:20, totaling 20 kg.
And so.

This mixture was mixed and kneaded in a ribbon type mixing tank, and 18 kg of granules with a diameter of 8 mm were obtained using an extrusion type granulator.

The composition of this granule was as shown in Table 7. The granules were placed in a dewar bottle for physics and chemistry (180 mmφ
0mwH) and fill it with 10kg and use an air pump to 0.05
l 7 mm kg of air was introduced.

The dewar bottle had a cork stopper, and the stopper was equipped with an exhaust pipe and a thermometer.

The temperature reached a maximum of 60°C on the 2nd day after ventilation and 72°C on the 13th day, and gradually decreased from the 4th day to the 8th day.
On the 122nd day, the temperature reached room temperature.

The CO2 concentration in the exhaust gas reached a maximum value of 15% after one day.
It decreased to 5% by the 4th day, and then gradually decreased to 10%.
It became 0 on day 0.

On the 122nd day, the contents were taken out and dried, and the resulting product was found to be a calcareous fertilizer based on the Fertilizer Control Law, as shown in Table 8.

The above-mentioned product was suitable as a soil conditioner because it did not scatter due to the wind even when spread on the field.

Claims (1)

[Claims] 1. A method for producing limestone fertilizer by mixing lime cake and surplus sludge from a sugar beet manufacturing factory, in which the moisture content of the mixture is adjusted to be in the range of 25 to 40%, and the mixture is granulated. A method for producing calcareous fertilizer characterized by fermentation under aerated conditions. 2. The method for producing calcareous fertilizer according to claim 1, characterized in that the amount of excess sludge to be mixed with the lime cake is 100 to 40 for the latter in solids ratio.