JPS5948160B2 - Dehydration method for muddy substances - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for dewatering muddy water materials with high water content, such as sewage sludge.

Currently, with the enhancement of water quality in public water bodies and the development and conversion of industry, the amount of water purification is increasing, and as a result, the amount of sludge as a byproduct is steadily increasing.

Generally, the combustible content of organic sludge is in the form of cellulose30
It has a calorific value of 00 to 4,500 (kcal/kg' organic content), which is comparable to that of coal.Despite this, more than 90% of the total amount of sludge generated ends up being dumped into the ground or the ocean.

However, untreated sludge contains a large amount of water and is putrefactive.
Dumping is restricted for environmental hygiene reasons because of the foul odor it produces, and large-scale disposal sites in large cities and surrounding cities are now saturated.

Therefore, with regard to the treatment and disposal of sludge materials, effective use and reuse have been advocated in terms of resource conservation, and both local governments and manufacturers are working hard to develop such methods, but there is still no decisive solution.

Conventionally, in order to dehydrate and solidify sludge containing organic components, some kind of conditioning agent is added to the sludge, and after conditioning, equipment such as gravity dehydration, vacuum dehydration, centrifugal dehydration, belt press, filter press, etc. is used alone or However, due to dehydration interference such as capillarity between water-containing powders and clogging of filter cloth, the water content after dehydration was in the 70 to 80% range, and various types of furnaces, including multi-stage furnaces, It was not possible to dehydrate it to the level that nature could in an incinerator.

Dehydration to the level of sludge and self-combustion is important from the perspective of resource conservation.

Here, it is necessary that the moisture content of the tranquil zone is about 65% or less.

For this reason, drying in the sun or by circulating combustion gas has been conventionally performed to evaporate water after dehydrating and solidifying the muddy material.

However, in the conventional method, 930 to 40% per ton of sludge cake
0! It required external fuel, which was uneconomical and caused many problems in terms of equipment.

The present invention solves the above-mentioned problems and provides a dewatering method that can dewater sludge materials to the extent that the water content can be reduced to the extent that nature allows and further energy can be created.

Therefore, the dehydration method of the present invention involves adding a dehydration aid to the primary dehydrated muddy material and granulating it to an appropriate particle size, and then secondary dehydrating the granulated material to reduce the moisture content to 60% or less. There are some that are characterized by

In a desirable implementation of the present invention, secondary dehydration is performed under pressure to reduce the water content to 50% or less.

The present invention will be explained in detail step by step.

In the primary dehydration of the present invention, muddy materials containing organic components collected from waterways, rivers, sedimentation ponds, etc. are processed using a dewatering machine such as gravity dehydration, vacuum dehydration, centrifugal dehydration, belt press, or filter press. Reduce the moisture content of the water to 82% or less.

For example, if you use a belt press, 2 to 3 kg/c
It is possible to dehydrate up to 75% moisture content by gravity and squeezing action at an operating pressure of m', and a centrifugal dehydrator can dewater up to 75%
Dehydration to the same <75% water content is possible by centrifugal force at an operating pressure of 0 G.

However, what you should be careful about here is to choose an appropriate operating pressure for each dehydrator.

However, unnecessarily increasing the operating pressure will cause the sludge to become compacted, making it impossible to drain the water, and will even lead to the opposite effect, such as clogging of the r-cloth.

The sludge that has been primarily dehydrated in this way is put into a rotary cylindrical mixer, etc., and crushed, and at least one of diatomaceous earth, slaked coal, calcium carbonate, incinerated ash, pulverized coal, sawdust, dried pulp, and soil is used as a dehydration aid. is added in an amount of 10 to 100% based on the dry weight of the original sludge solid content, and is granulated to an appropriate particle size.

Among the dehydration aids, incineration ash is relatively easy to obtain, such as sewage treatment sludge ash, sewage treatment sludge ash, industrial wastewater treatment sludge ash, municipal waste incineration ash, and industrial waste incineration ash, and has industrial reuse value. It is desirable to use a thin one.

In particular, it is most desirable to circulate and use a portion of the incineration ash produced by incinerating the dehydrated product produced in the practice of the present invention.

The granulation method is carried out using a mixer such as a rotary mixer, a set of screws, or a vibrating mixer, by pulverizing and mixing the above-mentioned dehydration aid so that it does not sink into the sludge and is dug up.

By refining the sludge and granulating it in this way, it is possible to granulate the sludge without destroying its fine structure.

This granulation method is extremely important in implementing the present invention.

In order to maintain the fine structure of the sludge and not impair its water permeability, the sludge is granulated in a manner similar to digging up the sludge, that is, cutting the sludge, so that the sludge is not kneaded during the granulation and mixing. Mix with auxiliary agent and sprinkle with auxiliary agent.

This allows the slurry to be granulated while preventing oscillation changes (chickentropy).

By granulating the sludge in this manner, the surface of the sludge granules is covered with the dewatering aid.

At this time, if the sludge is kneaded and shaken, the fine structure of the sludge will be broken and its water permeability will be reduced, resulting in a so-called clay-like state, making it extremely difficult to dewater.

If there is frequent cross-talk and oscillation changes occur, the water permeability of the sludge port body will decrease, and
Even if a dry dewatering aid is used, the water in the sludge will moisten the aid during this crosstalk, making the mixed layer on the surface of the sludge particles thicker, and the dry dewatering aid layer will become thinner. .

The particle size after granulation should be 20 mm or less in diameter, especially if the diameter is 1.
It is desirable that 70% or more of the particles by weight are distributed in the range of ~lQmm.

As in this invention, when a dewatering aid is added and the sludge material is granulated to an appropriate particle size, the surface of the sludge is always covered with the dewatering aid during the process of thinning the sludge material. Therefore, even if the sludge has a slightly high water content, it is possible to prevent the sludge granules from adhering to each other again.

By granulating in this way, the particle size of the granulated product is well-aligned.

This granular sludge material is again dehydrated (
Secondary dehydration) to reduce the water content to 60% or less,
Its capacity can be increased by more than 50% compared to the first one.

Further, this secondary dehydration is performed by squeezing, and the initial pressure and pressurization are performed separately.

By performing two-stage compression, the moisture content is reduced to 50% and the volume is reduced to 60% or less.

This initial pressure is 30 kg/cm' or less, preferably 15-2
5 kg/cm' and the time is preferably 2 minutes or less.

Further, the main pressurization is performed at 50 to 100 kg/cm'', preferably 60 to 80 kg/cm'' for 1 to 3 minutes.

Next, the present invention will be explained in detail based on experimental examples.

Sludge material A containing organic matter and having a water content of approximately 98% is collected by a mud pump and is supplied to a belt press.

At this time, the water content of the muddy material B was approximately 96%, as the water content decreased slightly during recovery.

This muddy substance B is subjected to primary dehydration using a belt press, and a solid muddy substance O condensed into a disk shape with a thickness of 1Q mm or less is taken out.

This solid mud material C is crushed in a rotating cylindrical mixer, and blended and mixed while adding incineration ash in the incinerator in a range of 0 to 200%.

The crosstalk time is about 20 to 40 seconds.

During this time, each time the muddy material O is turned over in the mixer, it is divided into quarters and mixed with the incinerated ash and rolled, resulting in a granular muddy material having a dry outer shell and having a diameter of 5 mm or less.

This granular slurry material is placed in a pressing device for secondary dehydration, and a pressing operation is performed by initially applying a pressure of 20 kg/cm'' for 1 minute.

Thereafter, pressurization is applied to apply a pressure of 70 kg/cm' for 2 minutes.

Through this operation, the granular mud material becomes mud material E with extremely low water content.

Further, this muddy substance E is crushed by a crusher to form a solid muddy powder F.

This solid muddy powder F can also be completely burned in an incinerator, and a part of the resulting incinerated ash can be used as a dehydration aid for addition and circulated back into the mixer.

Note that the 96% water-containing mud substance B may be formed into a 70% water-containing mud substance B' using a filter press, and the amount of incineration ash added in the mixer may be set to 30% or less to facilitate compression dehydration.

Next, the experimental results of this experiment will be explained.

Figure 1 shows the relationship between the amount of added incinerated ash and the water content of dehydrated sludge when incinerated ash is added as a dehydrating aid to the primary dehydrated sludge, mixed and granulated for secondary dehydration.

From this figure, as shown in graph a, when the water content before secondary dehydration is 98%, the water content after secondary dehydration remains constant until the amount of dehydration aid added reaches 100% or more, and then rapidly decreases. ,
It stabilizes at around 150%.

This moisture content was 40%.

Next, if the water content before secondary dehydration is 80%, graph B, and the water content after secondary dehydration is 4.
It became 0%.

When the amount of the dehydration aid is 30 to 50%, the water content after secondary dehydration is stabilized.

Next, if the water content is 75% before secondary dehydration (graph 0),
The process is almost the same as in the case where the water content is 80%, but it can be seen that the water content drops to 40% when the amount of auxiliary agent added is 20%.

As you can see from the above, the dehydration aid is 130% in both cases.
If more is added, the water content will be 60% or less.

However, if the moisture content before secondary dehydration is 98%, the moisture content will not reach 50% or less unless a dehydration aid of 150% or more is added.

On the other hand, for 80% and 75% products, the water content can reach 40% by adding only 20% of the dehydration aid.

In this way, it is desirable to reduce the water content as much as possible in the first dehydration process, but considering the functions of a normal dehydrator,
It is considered that a level of 2% or less is sufficient.

With this content, the dehydration aid can be attached to the surface of the granulated powder.

If the water content is higher than this, the dehydration aid will be consumed during granulation and a large amount of the aid will be required.

Next, in this experiment, the initial sludge material, the state of the sludge material after the primary dewatering, and the state of the sludge material after the secondary dewatering had a water content of 98% and 75%, respectively.
, 30%.

FIG. 2 shows a comparison of the weights of these.

For example, if the total weight of sludge with a moisture content of 98% is 1 kg at the beginning, after primary dewatering, if the moisture content is 75%, it will weigh approximately 1 kg.
80g, and 10g of dehydration aid after secondary dehydration.
Even if the weight of the water is 30%, the total weight will be reduced to 42g.

Comparing the water content weight: 980g, 60g, 12g respectively
and decrease.

The sludge material secondary-dehydrated in this way has a water content of 50 to 60.
% or less, it becomes a solid state with no surface moisture and has a calorific value of 2000 to 2500 kcal/kg as it is.

Next, the left diagram in Figure 3 is the granular muddy material before primary dehydration, and the right diagram is an imagined organization diagram of the combustible muddy material after secondary dehydration.

In the left figure, muddy material 1, sludge solids 12, and pore water 1
3. It is composed of capillary rising water 14, surface adhesion water 15, internal water 16, and surrounding free water 17, and everything except the solid sludge is water.

Of the above moisture, only internal water 16 exists inside the solid content 12 and has a strong binding force and is compressible, so it is difficult to mechanically remove water.
3, capillary rising water 14, surface adhering water 15, etc.) can be relatively easily dehydrated by adding a dehydration aid or mechanical dehydration.

It is assumed that the bay-shaped material after the secondary dewatering is deformed into a flat shape along with the sludge solids 12, as shown in the right figure, and almost all of the bound water other than the internal water 16 is excluded.

The above results are obtained because the drying aid 18 added before the secondary dehydration adheres to the outer skin of the bay-shaped material.
First, the affinity of the water 15 adhering to the surface is weakened.

It is thought that this is because the squeezing action is added, and the shell of the granular sludge material is crushed, and at the same time, the sludge solids are crushed, and bound water, etc., which has no place to escape, is drained to the outside through the voids between the particles.

Finally, FIG. 4 shows the moisture content of sludge materials in the conventional dewatering method and the dewatering method according to the present invention, and the thermal characteristics in each water content state.

As shown in this figure, in the current multistage furnace, 930 to 40 g of external combustion fuel is consumed per ton of sludge cake in order to dry the sludge material to a natural state.

Therefore, increasing the self-combustion level in various incinerators is being considered, but it is difficult to create a natural incinerator with a moisture content of 65% or more.

By the dewatering method of the present invention, the moisture content of sludge is reduced to 60% or less, preferably 50% or less, making it possible not only to burn the sludge as it is, but also to generate energy.

As explained above, the present invention has succeeded in reducing the water content to a level that enables self-combustion without wasting the advanced thermal properties of sludge material containing organic components, and in addition, the sludge material after dewatering has The capacity was reduced to less than 50%.

It is also possible to use the heat from combustion and convert it into useful energy such as power generation.

As described above, the present invention is a very effective method for dewatering sludge materials in these days when there is a demand for effective use and reuse of industrial waste from the viewpoint of resource conservation.

[Brief explanation of drawings]

Figure 1 shows the relationship between the amount of incinerated ash added and the water content of dehydrated sludge material, and Figure 2 shows the weight ratio of water and sludge solids for the initial sludge material, after primary dewatering, and after secondary dewatering. Figure shown, 3rd
The figure shows an imagined organization diagram of sludge material before dehydration and after secondary dehydration.
FIGS. 4a and 4b are diagrams showing the water content and thermal characteristics in each water content state in the conventional dewatering method of sludge material and the dewatering method according to the present invention. 1... Sludge substance, 12... Curved sludge solid substance, 13
... Waterproofing between songs, 14 ... Capillary rising water, 15 ...
Water adhering to curved surface, 16... Internal water, 17...
... Free water, 18... Bending drying aid.

Claims (1)

[Claims] 1. In dehydration of muddy materials, a dehydration aid is added to the muddy materials that have been primarily dehydrated, and the granules are granulated to an appropriate particle size while preventing fluctuation of the muddy materials. A method for dehydrating a muddy substance, which comprises covering the surface with a dehydration aid and subjecting the granulated material to secondary dehydration to reduce the water content to 60% or less. 2. A method for dewatering a muddy material according to claim 1, characterized in that the addition of a dehydration aid to the muddy material is carried out while the muddy material is being granulated. 3. A method for dehydrating a muddy substance according to claim 1 or 2, characterized in that the secondary dehydration is performed under pressure to reduce the water content to 50% or less. 4. In the method according to any one of claims 1 to 3, the water content of the slurry material is reduced to 8 in the primary dehydration.
A dehydration method characterized by reducing water to 2% or less. 5. In the method according to any one of claims 1 to 4, diatomaceous earth, slaked lime,
A method for dewatering muddy substances, characterized by using one or more of calcium carbonate, incineration ash, pulverized coal, soil, bone meal, sawdust, and dried pulp. 6. A method for dewatering muddy substances as set forth in claim 5, characterized in that incineration ash is used. 7 In claim 6, the incineration ash is sewage treatment sludge ash, frozen urine treatment sludge ash, industrial wastewater treatment sludge ash, municipal waste incineration ash, industrial waste incineration ash, or a mixture thereof. A method for dehydrating muddy substances characterized by: 8 In claim 1 or 2, the amount of the dehydration aid added is 10 to 10
A method for dehydrating muddy substances, characterized in that the amount of water is 0%. 9. A method for dewatering muddy substances according to claim 1 or 2, characterized in that the particle size after granulation is 20 mm or less in diameter. 10 In claim 9, a diameter of 1 to 10
A method for dewatering muddy material, characterized in that 70% or more of particles by weight are distributed in a particle size band of mm. 11 Claim 3 is characterized in that the pressurization method is direct pressurization or indirect pressurization using either a vertical or horizontal dehydrator, and 2' is a two-stage compression process in which pressurization is applied after initial pressure. Method for dewatering muddy substances. 12. Claim 3 is characterized in that the initial pressure is 30 kg/cm or less for 2 minutes or less, and the pressure is 50 to 100 kg/cm' for 1 to 3 minutes. A method for dehydrating muddy substances.