Method for processing clayey sludge

Abstract

The present invention adds quicklime to clayey sludge as an additive that produces a water absorption effect and a heat generation effect. The clayey sludge is sludge which contains about 20 wt% water, specifically 15 to 25 wt% water, has an adherence property, and is difficult to disintegrate. The amount of quicklime added is at least 3 wt% or more. Then, the clayey sludge with the quicklime added is loaded into a vibratory kneading apparatus (1) comprising a drum (2) in which a rod (3) is housed, and the drum (2) is caused to generate a circular vibration with a vibration acceleration of 3 to 8 G, whereby the clayey sludge is efficiently disintegrated, fine-grained, and dewatered into a granular material or an agglomerated material.

Description

Method for treating clayey sludge.

[0001] The present invention relates to a method for treating clayey sludge.

[0002] Sludge includes clayey sludge, which contains approximately 20% water by weight, specifically 15% to 25% by weight, and is sticky and difficult to crush. Clayey sludge is generated, for example, during the solid phase recovery process of slurry, as described below. Water treatment typically involves large amounts of water in factories, earth and stone quarries and storage sites, and sewage treatment plants, generating large amounts of slurry. Slurries are also generated when dry powder dust collected by dust collectors undergoes water treatment. The solid phase of the slurry is diluted to improve transportability. To recover the solid phase, the slurry is poured into a settling pit, where it settles to the bottom and is separated into a high-solids slurry and a supernatant liquid. Settling pits typically have partitions with overflow weirs between them. The solid phase settles sequentially from coarse to fine particles upstream, and the sediment is collected by particle size between multiple pits. Coarse-grained sediments drain easily, so simply lifting them up and placing them in a draining area reduces their moisture content, making them suitable for handling by heavy machinery and transportation. However, fine-grained sediments settle slowly in pits and require prolonged settling and settling before they can be concentrated. Furthermore, the supernatant liquid that does not settle completely in the pit alone is further transferred to thickeners, settling tanks, lagoons, etc., where it is left standing for a long period of time to promote the settling and settling of fine particles. High-concentration fine-grained slurries concentrated in these pits or thickeners are transported by specialized vehicles such as vacuum trucks for direct use. However, since direct use is limited, they are further dewatered for transport by truck or belt conveyor and reuse. Dewatering machines such as filter presses are used for dewatering. Alternatively, a method that does not require a dewatering machine can be used: dredging the muddy sludge that has accumulated at the bottom of a pit or settling tank, lifting it into a draining area, and allowing it to dry naturally in the sun (air drying). The resulting dewatered cake and sun-dried sludge are clayey sludge. This clayey sludge is sticky and difficult to break down, so if it is transported as is by truck or belt conveyor, the clayey sludge will not only stick to the conveyor and adhere to the body of the machine, but some of it will also fall off the conveyor, contaminating the transport route.In addition, there is the problem that the clayey sludge does not meet the moisture acceptance standards of landfill sites as it is.Furthermore, even in factories that use the clayey sludge after transportation, its stickiness makes handling operations such as shoveling difficult, and it also causes the sludge to adhere to the walls of storage tanks and cutting openings at processing plants, making processing operations difficult.

[0003] Due to the above-mentioned problems, there is a need to reduce the moisture content of clayey sludge. Generally, as an industrial method for quickly and steadily drying, there is a heat drying method using a heat drying oven (for example, Patent Document 1). However, the heat drying method requires equipment costs, energy, and manpower, and has a large environmental impact, requiring dust collection of the exhaust gas and NOx removal from the combustion exhaust gas. X This requires the installation and operation of environmentally friendly equipment such as carbon dioxide removal, which places a heavy burden on the economy. Furthermore, clayey sludge is often generated in multiple locations in large factories, necessitating the installation of multiple heating and drying furnaces, which increases the economic burden and makes installation difficult. To avoid the economic burden and environmental impact of heating and drying, sun drying is widely used. This method involves leaving the sludge to dry for long periods of time, over weeks or months, at the treatment plant. This requires a large storage area. The drying rate slows, especially in winter. Furthermore, rain during the drying process can cause the sludge to rehydrate, regardless of the season. Furthermore, when attempting to dry the interior of the pile, the sun drying method can result in the surface layer becoming too dry, which can cause dust to fly from the surface in the wind, creating a dust source. Furthermore, both heating and sun drying methods tend to result in coarse solidification during the drying process. The solidified material obtained is then sieved and sized for different uses. However, due to the low strength of the agglomerates, they tend to break down during handling, making their reuse difficult. Furthermore, the particle size of the agglomerates changes depending on the drying method, making it difficult to meet the particle size requirements for reuse. To reuse them as agglomerates, it is necessary to create particle sizes appropriate for the intended use and ensure strength that can withstand handling. Furthermore, since powdered materials are often used for reuse, it is necessary to sift the solidified material and crush and pulverize it using a crusher, etc., which poses the problem of extra effort and cost.

[0004] To address the above-mentioned issues, a method of adding a flocculant has been proposed as a moisture reduction promotion technology for the sun drying method (see, for example, Patent Document 2). However, some flocculants can be expensive, and even with this method, several days of sun drying are still required to reduce the moisture content to a level where the material is no longer sticky, so the fundamental issues of the sun drying method remain unresolved. Furthermore, depending on the purpose of reuse, this method may result in the formation of coarse aggregates or the flocculant component of the additive may be a hindrance.

[0005] Another improvement over the non-calcination method is the use of oxidative exothermic sludge (see, for example, Patent Document 3). This method involves blowing air or preheated air up from the bottom of a pile of oxidative exothermic agents, efficiently reducing moisture through oxidative heat generation. However, the availability of the necessary oxidative exothermic sludge is limited, making this a technology that cannot be universally applied. Furthermore, blowing up the sludge raises environmental concerns due to dust generation from the surface. This method also generates coarse, solidified particles in the dried product, which necessitates sieving, crushing, and pulverization before reuse.

[0006] Another improvement over the non-calcination method is the addition of quicklime to sludge to reduce moisture content through the effects of quicklime absorption and heat evaporation (see, for example, Patent Documents 4, 5, and 6). Adding quicklime is a widely used technique not only in industry but also in the civil engineering and construction industries, and is an effective means of reducing moisture content. However, when quicklime is mixed using a conventional shovel or kneading machine, the stickiness cannot be eliminated unless the moisture content is reduced to 10% by weight or less through sun drying (see Patent Document 6). This is thought to be because conventional mixing methods make it difficult to crush and refine clayey sludge, and the interior of the coarse particles is not dehydrated, resulting in water seeping out of the lumps during handling, preventing the stickiness from being eliminated. Therefore, the coarse particles must be thoroughly dried, and after mixing, they are dried over time by sun drying or in a heated drying oven to reduce the moisture content to 10% by weight or less. Furthermore, if additional drying is carried out without sufficient crushing, the material will solidify into large pieces, and the problem remains that it cannot be reused unless it is sieved, crushed, or pulverized.

[0007] As described above, when applying known techniques and their improved techniques to the treatment of clayey sludge, there remain issues that need to be improved not only in terms of treatment efficiency, economy, and environmental impact, but also in terms of the properties of the dried product.

[0008] JP 11-6019 JP 2016-109324 JP 2019-98327 JP 6-238299 JP 9-316 513 Publication JP 2000-237512 JP 2016-141826 JP 2-169080 JP 4-193749

[0009] As mentioned above, clayey sludge treatment methods include heat drying and sun drying, with the addition of sieving and crushing / pulverization of the dried product. However, heat drying poses economic and environmental challenges due to equipment costs and heating energy consumption, as well as the need for secondary processing, such as crushing and sieving of the dried product. Sun drying, a non-calcination treatment method that improves on these issues, requires a long drying time and a large space, and also poses the problem of dust generation from the surface of the drying pile. Furthermore, proposals to shorten the sun drying period have been made as an improvement, but while effective in shortening the drying time, the final stage still requires sun drying, and the dried product still requires sieving, crushing, and pulverization. Furthermore, to reuse the solidified material obtained by drying as a lump, it is necessary to create particle sizes appropriate for the intended use and ensure strength sufficient for handling. In order to obtain agglomerates with sufficient strength, a technique has been proposed in which the dried material is crushed to a particle size suitable for granulation (for example, about 40 μm or less), and then a binder and water suitable for granulation are added to granulate (Patent Documents 8 and 9). However, such a method requires a great deal of equipment and work for agglomeration, resulting in a high cost burden.

[0010] The present invention has been made in consideration of the above points, and aims to provide a processing method that solves the problems associated with the heat drying method and the sun drying method, efficiently crushes and refines clayey sludge, reduces the moisture content, and turns it into powder or granules.

[0011] The method for treating clayey sludge of the present invention is characterized by comprising the steps of: adding an additive to the clayey sludge that provides moisture absorption and heat generation; and loading the clayey sludge with the additive added into a vibratory kneading device equipped with a drum containing a rod or a mill, and converting the clayey sludge into powder or granules by causing the drum to vibrate circularly with a vibration acceleration of 3 G or more and 8 G or less.

[0012] According to the present invention, it is possible to provide a processing method that solves the problems associated with the heat drying method and the sun drying method, efficiently crushes and refines clayey sludge, reduces the moisture content, and turns it into powder or granules.

[0013] FIG. 1 is a diagram illustrating a method for treating clayey sludge according to an embodiment. FIG. 2A is a diagram illustrating the relationship between the moisture content of sludge and the state of moisture in interparticle gaps (pendular state). FIG. 2B is a diagram illustrating the relationship between the moisture content of sludge and the state of moisture in interparticle gaps (fungular state). FIG. 2C is a diagram illustrating the relationship between the moisture content of sludge and the state of moisture in interparticle gaps (capillary state). FIG. 2D is a diagram illustrating the relationship between the moisture content of sludge and the state of moisture in interparticle gaps (immersion state). FIG. 3 is a diagram illustrating the results of Test Example A. FIG. 4 is a diagram illustrating the results of Test Example B. FIG. 5 is a diagram illustrating the results of Test Example C. FIG. 6 is a diagram illustrating the results of Test Example D. FIG. 7 is a diagram illustrating the results of Test Example E.

[0014] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. [First Embodiment] Fig. 1 is a diagram illustrating a method for treating clayey sludge according to an embodiment. Clayey sludge is sludge that contains approximately 20% by weight of water, specifically 15% to 25% by weight, and is sticky and difficult to disintegrate. Quicklime is added to the clayey sludge as an additive that provides moisture absorption and heat generation. The amount of quicklime added is at least 3% by weight. The clayey sludge to which quicklime has been added is then charged into a vibratory mixer 1 equipped with a drum 2 containing a rod 3. In this embodiment, the clayey sludge is converted into powder by subjecting the drum 2 to circular vibration with a vibration acceleration of 3G to 8G.

[0015] A vibration mixer 1, also known as a high-speed stirring rod mill, is disclosed in, for example, Patent Document 7. Patent Document 7 describes it as a vibration granulator, but its official name is a vibration kneading granulator. While this device can also function as a granulator if the moisture content is increased to the appropriate range for granulation, in this application, it is referred to as a vibration mixer because it is used as a device that performs a kneading function for the purpose of reducing moisture content. As shown in FIG. 1 , the vibration mixer 1 includes a drum 2 containing several dozen rods 3 therein, a vibration source 4 including a vibration motor mounted on the outer periphery of the drum 2 to generate a circular vibration in the drum 2, and a suspension device 6 on a frame 5 supporting the drum 2. The vibration source 4 is composed of two rotary weight-type vibrators and generates a circular vibration in the drum 2 with a vibration acceleration of 3G to 8G. Clay-like sludge is extracted from a clay-like sludge tank 7, and quicklime is extracted from a quicklime tank 8. The clay-like sludge to which quicklime has been added is then introduced into the drum 2 via a conveyor 9. When the vibration source 4 (two rotary weight vibrators) is activated, the rod 3 inside the drum 2 moves in a direction counter to the rotation of the vibration source 4. This movement, which resembles a combination of rotation and revolution, crushes and kneads the clayey sludge containing quicklime added, which is placed in the drum 2, into a powder. The processed powder is transported from the drum 2 via a conveyor 10 to a storage location (e.g., an indoor yard or a storage tank) for storage. In this way, clayey sludge containing quicklime added is loaded into the vibrating kneader 1, and the drum 2 is subjected to circular vibration with a vibration acceleration of 3G to 8G. This system crushes and refines the clayey sludge and quicklime, bringing them into intimate sliding contact with each other. This causes the quicklime to absorb moisture, which is then evaporated by the heat generated by the slaked lime reaction. This rapidly and uniformly reduces the moisture content of the clayey sludge, resulting in a powder that is easy to transport and reuse.

[0016] The inventors of the present application noticed that when the moisture content of sludge reaches about 20% by weight, the drying rate drops significantly, and that this slow drying leads to stickiness. They believed that in order to solve the problems of the existing technology, it was necessary to clarify the reason why dewatering stagnates, and also to clarify the root cause of the formation of coarse aggregates during the drying process in conventional methods, and to resolve this cause. Figures 2A to 2D are diagrams explaining the relationship between the moisture content of sludge and the state of moisture in the gaps between particles. They speculated that the main reason dewatering stagnates when the moisture content of sludge reaches about 20% by weight is the capillary water filling structure between the gaps between sludge particles, and conducted further research. Based on basic knowledge of powder engineering, it can be inferred that once the moisture content in the powder packing reaches approximately 20% by weight, the interconnected structure of capillary water (funicular phase diagram: see Figure 2B) changes to a bridged structure of capillary water (pendular state: see Figure 2A), the interconnected structure of the pore water is broken, air becomes interconnected, a meniscus forms in the water bridging between particles, water retention increases, and the dehydration mechanism changes. The particles that make up clayey sludge are fine particles of several tens of micrometers or less, making it difficult for the pore water to move and evaporate. Incidentally, when the pore water is in an immersed state (see Figure 2D), it is in a slurry state. The reason why dehydration proceeds relatively smoothly using a dehydrator or sun drying is thought to be because it is in a capillary state (see Figure 2C). In these states, the capillary water is interconnected and in the same evaporation state as the free water surface, equivalent to the evaporation rate from a general water surface. Therefore, when the moisture content reaches approximately 20% by weight, the capillary water between particles forms a bridge structure, and it becomes suddenly difficult to evaporate, especially for fine particle sludge, causing the drying speed to drop sharply and causing sun drying to stagnate.

[0017] The thermal drying method promotes evaporation by increasing the saturated vapor pressure of pore water through heating, which causes drying stagnation in the pendular state. However, it is uneconomical and has many issues, such as energy consumption and environmental problems. Therefore, a non-calcination method is preferable, but the sun drying method requires a long time for evaporation due to dehydration stagnation at room temperature. Based on the above considerations, we conducted experiments to identify the causes of dehydration stagnation in existing technologies and to efficiently resolve dehydration stagnation. Quicklime is known to be an effective moisture absorbent, and technologies applied to sludge dehydration are shown in Patent Documents 4, 5, and 6, and are considered effective. However, even the methods described in Patent Documents 4, 5, and 6 have not completely resolved dehydration stagnation, and sun drying has not yet been completely eliminated. To investigate the cause, we first examined the changes in the pore water filling structure during the dehydration process when mixing quicklime using the widely used shovel method. The results showed that the clayey sludge was not sufficiently crushed and refined, leaving many coarse particles. Although quicklime was in contact with the surface of the coarse particles, the interior of the particles contained no quicklime. While there was some surface absorption, it was limited, and the sludge remained in a state close to its original high moisture content. In this dry state, handling the coarse particles resulted in water seeping out of the particles, preventing the stickiness from being resolved. This was one of the reasons why long-term sun-drying was required even after mixing. In fact, careful crushing of the coarse particles with a transplant trowel accelerated drying, and it was confirmed that stickiness was resolved even when the average moisture content was 10% or more by weight. For clayey sludge, enhancing crushing and refinement are crucial. Mixing quicklime without leaving coarse particles behind is thought to promote uniform drying, efficiently resolve caking, and simultaneously eliminate agglomerated coarse particles in the dried product.

[0018] Based on the above findings, we investigated a method for crushing and refining clayey sludge while uniformly mixing it with quicklime. While a shovel is the most economical and practical method, as mentioned above, it has poor crushing and refining capabilities. Even with careful and repeated mixing, there is a limit to how much finer the sludge can be broken down, and coarse particles remain. Therefore, we investigated a method to increase the crushing and refining power of clayey sludge. Mechanical mixing methods include axial compression mixers. Axial compression mixers have more pressing force than a shovel, but they have limited crushing and refining power and require more power. Experiments were conducted using a vibration mixer 1, which is known to have both strong pressing force and sliding crushing power. After various experiments, we found that applying a circular vibration to the drum with a vibration acceleration of 3G to 8G exhibited superior crushing and refining capabilities, distinct from known mixing methods, significantly reduced moisture content, eliminated adhesion, and made the sludge ready for use immediately after processing. This is because the vibration mixer 1 uses a vibration force based on the centrifugal force of high-speed rotation at around 1000 rpm to crush the clayey sludge and quicklime by forcing them between the rods and against the drum wall at high acceleration with a pressing force not found in conventional mixers. The strong sliding force caused by the rotation also creates a mixing contact action, which is thought to further break down the capillary water bridge structure of the meniscus formed between the fine particles of the sludge, increasing the opportunity for contact with the quicklime. As a result, the opportunity for contact between the quicklime and sludge particles becomes closer than ever before, resulting in improved efficiency. Furthermore, the high degree of freedom of rod movement prevents overload like that of axial compression mixers, reducing power consumption and making the system more economical.

[0019] Next, in addition to the unique effects described above, we found that this method significantly enhances uniform mixing by adding other additives to clayey sludge and quicklime. For example, when attempting to mix dry powder with clayey sludge, the clayey sludge is jelly-like and plastic, making uniform mixing difficult. The moisture reduction load decreases in proportion to the amount of dry powder added, enhancing the sludge dehydration effect, but this effect is achieved by achieving uniform mixing. By applying this method, dry powder can be uniformly dispersed into the clayey sludge while mixing and kneading. Note that a low moisture content of dry powder is preferable; if it is too high, the moisture reduction effect is reduced accordingly. In locations where inexpensive dry powder is readily available, this method can be used to more efficiently reduce moisture and also serve as a dust treatment for the dry powder.

[0020] In addition, the addition of a heat-generating agent is expected to be effective in dewatering clayey sludge, but it was difficult to achieve uniform mixing using conventional mixing methods.By applying this method, the additive can be dispersed uniformly, and the heat-generating effect can be achieved efficiently.

[0021] Among clayey sludges, those containing oil tend to be very sticky and are particularly difficult to dewater. By applying this method, clayey sludge containing oil can achieve the same treatment effect as regular sludge, but the dewatering efficiency tends to be lower than that of regular sludge, which is thought to be because the presence of oil has the effect of delaying the reduction of moisture.

[0022] Therefore, we investigated a solution. When quicklime is added to oil-containing clayey sludge, it not only exhibits its inherent water absorption and heat-generating evaporation properties, but also dehydrates the sludge, decomposing the oil and destroying the oil film covering the particles. This method uses high-speed mixing, and the processing time is very short, ranging from a few minutes to 10 minutes, which is too short for the quicklime to react with the oil. Therefore, it is considered necessary to allow time for the quicklime and oily clayey sludge to react and to allow a curing period. In fact, we found that when the sludge was premixed with a shovel or other device, left for a predetermined period of time, and then pre-cured, and then processed using the vibratory mixer 1, the moisture content was reduced more efficiently than when pre-curing was not performed.

[0023] It is also known from Patent Document 5 and other sources that if an alkali agent is added to the oil after pre-curing, the reaction between the alkali and quicklime is further accelerated. However, unlike quicklime, the reaction time of the alkali agent is short, so it is not necessary to add it during pre-curing, and it can be added directly when charging the oil into the vibration mixer 1. When this method is applied, the kneading force is stronger than in conventional methods, so the de-oiling effect of adding alkali is more pronounced than in conventional methods.

[0024] This method can also treat even more sticky sludge, such as clayey sludge containing oil generated in steel mills. This type of sludge is generated during the wastewater treatment of water used for cooling and cleaning steel products and equipment cooling in steelworks continuous casting, hot rolling, and cold rolling plants. It contains several to several dozen weight percent of oil, making the sludge even more sticky, even if the moisture content of the sludge remains the same. This method is also effective for treating particularly sticky clayey sludge. Furthermore, dewatering can be further enhanced by combining it with a technology to promote oil decomposition. When treating clayey sludge containing oil, premixing the sludge with a shovel and curing it before processing can accelerate the moisture reduction effect. The pre-curing time depends on the reaction time of the quicklime to decompose the oil, and is usually several hours to a day. Furthermore, adding an alkali metal to the clayey sludge containing oil accelerates the moisture reduction rate by evaporating the water due to the oil decomposition and reaction heat. The amount of alkali added is roughly proportional to the oil content, but varies depending on the type of oil, etc.

[0025] As described above, clayey sludge can be quickly, efficiently, and economically reduced in moisture content without heat drying or sun drying, resulting in a non-sticky, easily workable powder. This eliminates issues such as contamination during transportation and handling, as well as issues with shoveling and sticking to the walls of raw material tanks and difficulty in excavating the sludge at recycling plants, making it possible to handle the sludge immediately after treatment. At the same time, this method eliminates the problem of the treated product containing large, agglomerated particles, which is often encountered with conventional heat drying and sun drying methods. This allows the treated product to be used directly without sieving, crushing, or grinding. In some cases, this method may even meet landfill acceptance regulations for dried sludge. Another advantage is that the moisture reduction level of the treated product can be freely adjusted. The final moisture content of the treated product can be easily controlled by adjusting the amount of moisture reduction accelerator, such as quicklime, and the operating conditions, such as the processing time of the vibratory mixer 1. While excessive dryness after drying can lead to dust generation, dust generation can be prevented by limiting the moisture content to a few weight percent.

[0026] As mentioned above, sludge that is highly sticky and difficult to disintegrate, such as clayey sludge, often becomes partially solidified when left to dry in the sun for a long period of time, but clayey sludge that is in the process of drying can also be treated with this technology. There are no particular restrictions on the physical properties, such as particle size, of the particles that make up the clayey sludge. However, since the particles of sticky lumps of sludge that are difficult to dewater are composed of fine particles, even if coarse particles are included, this is not a problem because the vibrating kneading device 1 has the crushing power. Furthermore, there are no restrictions on the chemical composition of the clayey sludge, as long as it does not contain any harmful components.

[0027] As described above, we have discovered unique benefits of using a vibration mixer 1 to generate circular vibrations in the drum 2 with a vibration acceleration of 3G to 8G. Any model can be used as long as it has the ability to break down clayey sludge into fine particles and apply strong pushing and sliding forces to the clayey sludge between the rods 3 and on the drum wall. Furthermore, the mixing media are not limited to rods, and can be in the form of balls or other media. Regarding vibration conditions, we found that vibration accelerations of 3G or less only produce effects similar to those of conventional mixing methods. Therefore, the vibration acceleration must be 3G or greater. The optimal vibration acceleration can be determined based on the particle size distribution, particle morphology, and oil content of the fine particles that make up the clayey sludge. Furthermore, for clayey sludge containing oil, vibration accelerations of 6G or greater tend to be ineffective. This is thought to be due to the destruction of the capillary water bridge structure caused by increasing the vibration acceleration. Furthermore, vibration accelerations of 8G or greater pose problems related to device specifications, mechanical durability, wear, and operating costs, reducing economic viability.

[0028] The chemical components of quicklime are such that the higher the quicklime concentration, the greater the effectiveness of use, and the amount added can be reduced. However, the type of quicklime used is selected based on cost-effectiveness. In addition to commercially available quicklime, by-products generated in quicklime plants and collected dust, etc., that contain quicklime can also be used cost-effectively. Furthermore, although less effective than quicklime, materials that absorb moisture and generate heat, such as calcined dolomite powder, can be used as a substitute, regardless of their components, provided they are not restricted by the reuse requirements. The amount of quicklime added must be at least 3% by weight in order for this method to be effective. The amount of quicklime required to be added is roughly proportional to the moisture content of the sludge, but it also depends on the particle size, particle size distribution, and particle size of the clayey sludge's constituent particles, as well as its heat generation, ease of steam evaporation, and specific heat. It also varies depending on the target moisture content of the final dried product and the target for improving handleability. Therefore, the appropriate amount of quicklime to be added can be determined appropriately depending on the type of clayey sludge to be treated. Commercially available fine-grained quicklime can be used for the particle size of quicklime. The finer the quicklime particles, the greater the moisture reduction effect. However, because the vibratory mixer 1 itself has a strong crushing power and can perform particle refining while the vibratory mixer 1 is operating, the advantage of this technology is that the effects of quicklime can be fully achieved even when using inexpensive, coarse-grained quicklime powder rather than expensive fine powder.

[0029] The present invention will be described in more detail below with reference to test examples. However, the present invention is not limited to these test examples. (Test Example A) As a comparative method, clayey sludge and quicklime were mixed using a shovel and then dried in the sun at a storage site. Furthermore, as a method applying the present invention, clayey sludge to which quicklime had been added was charged into a vibratory mixer and vibrated to form a powder. Figure 3 shows the results of Test Example A. A Vibro Explorer manufactured by Abe Iron Works Co., Ltd. was used as the vibratory mixer. The amounts of quicklime added were 15 wt%, 20 wt%, and 25 wt%, and the mixer was operated to generate a circular vibration of the drum with a vibration acceleration of 6G. The moisture content of the clayey sludge before treatment was 23.5 wt%. When quicklime was added and mixed with clayey sludge using a shovel, the moisture percentage immediately after treatment was higher in the shovel mixer than in the present method. With shovel mixing, there are large variations in moisture content within the pile of treated material, but it can be said that treatment with this method reduces the moisture content uniformly. There is also a significant difference in the particle size distribution of the treated material. This method makes it possible to crush and refine the clayey sludge, and this refinement is thought to have reduced the variations in moisture distribution and particle size distribution.

[0030] When handling the treated material, even with similar moisture levels, the powder processed using this method had good fluidity and no stickiness, whereas the sludge from shovel-mixed sludge stuck to the bucket. In the case of shovel-mixed sludge, handling immediately after processing likely resulted in moisture seeping out from the lumps, preventing the stickiness from disappearing. Therefore, to dry the lumps to their interior, it is believed that the total moisture content must be reduced to 10% by weight or less. This difference is likely due to differences in crushing and granulation, as well as the degree of dispersion of the quicklime. Observation of the surface of the pile immediately after processing clearly showed large differences in the particle size of the sludge composition and differences in the dispersion of the white quicklime. While the shovel-mixed sludge had relatively coarse quicklime, the sludge processed using this method was grayish-brown and uniformly dispersed. As described above, application of this invention can efficiently convert clayey sludge into a powder with good workability.

[0031] (Test Example B) Among clayey sludges, those containing oil tend to be highly adhesive and particularly difficult to dewater. Test Example B was a test example designed to further improve the performance of clayey sludge containing oil. Figure 4 shows the results of Test Example B. Even oily clayey sludge can be processed into a non-adhesive, easily workable powder by using a vibratory mixer under appropriate operating conditions, but dewatering efficiency tends to be poor. This is thought to be due to the presence of oil slowing the reduction of moisture. As the oil content increases from a few weight percent to several tens of weight percent, the sludge becomes even more adhesive, making processing more difficult and requiring the addition of large amounts of quicklime, for example. The passage time through a vibratory mixer is typically short, typically just a few minutes, which itself indicates excellent operating efficiency, but is thought to be too short for the quicklime and oil to react. It is generally known that quicklime has the effect of partially decomposing oil when it reacts with it, and that the reaction between quicklime and water generates steam, which evaporates the oil. However, it was thought that the reaction was slow to progress due to the short processing time of the vibratory mixer. Therefore, as a practical method to extend the reaction time, we mixed the oil-containing clayey sludge with quicklime in advance using a shovel and cured it, thereby increasing the reaction time, and we examined the improvement effect. Furthermore, it is known that adding alkali is effective in decomposing oil, and that this reaction time is short. This does not require curing time, and the processing time of the vibratory mixer is considered to be sufficient for the reaction, so we also tested this.

[0032] In Test Example B, 1 ton of clayey sludge containing 7% oil was treated with 20% quicklime by weight. As a comparison method, the conventional shovel-mixing method was used. In the present invention, the clayey sludge with added quicklime was charged into a vibrating mixer and vibrated to form a powder. The vibrating mixer used was a Vibro Explorer (VMP200) manufactured by Abe Iron Works Co., Ltd., and was operated to generate a circular vibration of drum 2 with a vibration acceleration of 7G. Three conditions were tested for this method: mixing the clayey sludge and quicklime in the vibrating mixer without curing; pre-mixing with a shovel followed by one-day curing followed by processing in the vibrating mixer; and pre-mixing with a shovel followed by one-day curing followed by processing in the vibrating mixer with the addition of an alkali agent. The alkali agent was a 48% caustic soda solution at 2% by weight of all samples. As shown in Figure 4, by pre-mixing and curing clayey sludge with quicklime, and by adding an alkaline agent, the decomposition of oil was promoted, although it was only partially decomposed anyway, and the stickiness was efficiently eliminated, and an improvement effect of promoting dewatering was observed.

[0033] [Second Embodiment] In the first embodiment, an example of producing a powdered or granular material was described. As shown in FIG. 3 , clayey sludge can be efficiently crushed and refined, and the moisture content can be reduced to approximately 10% by weight, depending on the type of clayey sludge. This results in a powdered or granular material with high fluidity, which can be reused, for example, as an injection material in steelmaking. In contrast, in the second embodiment, an example of producing a granulated material is described. The following description focuses on differences from the first embodiment, and omits commonalities. FIG. 1 is a diagram illustrating a method for treating clayey sludge according to an embodiment. Quicklime is added to the clayey sludge as an additive that provides moisture absorption and heat generation. The amount of quicklime added is at least 3% by weight. The clayey sludge to which the quicklime has been added is then charged into a vibratory mixer 1 equipped with a drum 2 containing a rod 3. A circular vibration of the drum 2 with a vibration acceleration of 3G to 8G is applied to produce a granulated material in this embodiment.

[0034] The present inventors focused on the adhesiveness of clayey sludge and investigated whether it could be utilized to produce granules of the desired particle size. First, they investigated the relationship between the moisture content of the sludge and its adhesiveness. As a result, they found that the adhesiveness of the sludge generally decreased as the moisture content decreased, i.e., as the sludge dried. As the sludge dried, it tended to become powdery, but some areas formed lumps due to the adhesiveness. When they investigated the causes of the difference between the formation of powdery particles and lumps, they found that one of the causes was the difference in drying rate depending on the location. Therefore, they conducted various studies to determine whether it was possible to homogenize the moisture content of the granulation raw material and produce granules of uniform particle size and strength sufficient for practical use, utilizing the technology described in the first embodiment for uniformly and efficiently reducing the moisture content of clayey sludge.

[0035] A clayey sludge containing added quicklime was charged into a vibratory mixer 1, and a circular vibration with a vibration acceleration of 3G to 8G was applied to the drum 2. A test was conducted by varying the amount of added quicklime. Figure 5 shows an example of the relationship between the amount of added quicklime and the average particle size of the granulated material. As the amount of added quicklime increased, the adhesiveness gradually decreased, and the particle size gradually became smaller. It was found that the particle size was approximately proportional to the granulation moisture content (the moisture content of the granulated material). The change in the granulation moisture content with the amount of added quicklime reflects the difference in the amount of moisture volatilized by the exothermic reaction of quicklime. In other words, the relationship between the granulation moisture content and the particle size is thought to be the result of the change in the powder binding strength of water due to the granulation moisture content, which in turn changes the adhesive strength. Although the amount of added quicklime was varied in this test, because the amount of added quicklime and the granulation moisture content are inversely proportional, the test was conducted with an increased moisture content in the pendular range. Although the binder effect weakens with the reduction in the amount of quicklime added in this range, the increased binding force of capillary water prevails, resulting in larger particle sizes. It is well known in engineering that the difference in the binding force of capillary water is due to the influence of interstitial water in the powder and the difference in the surface tension of free water trapped between particles. This is understood as follows: From zero moisture to approximately 20% moisture by weight, as the moisture content gradually increases, the surface tension of capillary water formed around interparticle junctions in the powder increases, acting as a powder binding force and promoting granulation. The granulation is in what is known as a pendular state in powder engineering (Figure 2A). The higher the moisture content, the stronger the binding force, resulting in larger granules. However, when the moisture content exceeds 20% by weight, the interconnected pore structure is broken, forming a interconnected structure of capillary water (funicular state (Figure 2B)). As the moisture content increases, the sludge becomes more slurried, increasing its fluidity and preventing granulation. The above results are believed to be due to the fact that the moisture content of the clayey sludge decreases in the pendular region with the addition of quicklime. In this way, when the granulation moisture content is reduced to 20% by weight or less, granules are produced.

[0036] However, when using conventional pelletizers or extruders, clayey sludge is difficult to shred and divide, and quicklime is not uniformly mixed with the clayey sludge, resulting in uneven moisture content, particle size, and strength. When clayey sludge and quicklime are vibrated in the pendular range as in this method, the clayey sludge and quicklime are pressed firmly between the rods and against the mill walls, resulting in finer quicklime and sludge particles. The rotation and sliding of the rods promotes uniform moisture and quicklime distribution, resulting in uniform moisture content and uniform particle size granules from the clayey sludge. Furthermore, the resulting strong compaction force improves strength and reduces strength variation. Thus, this method significantly reduces moisture content more uniformly than conventional quicklime mixing methods, while simultaneously improving binder binding strength. Furthermore, by adjusting the amount of quicklime added, particle size control of granules with practical strength can be achieved.

[0037] Next, considering that granule particle size varies depending on the granulation moisture content, we considered whether adding dry powder to the clayey sludge and quicklime to adjust the granulation moisture content and change the particle size. Therefore, we investigated the use of dry powder for moisture adjustment. Figure 6 shows examples of the relationship between the amount of quicklime added and the granulation moisture content, as well as strength (crushing strength), for cases with no dry powder, 10% dry powder mixed by weight, and 20% dry powder mixed by weight. Clayey sludge is jelly-like and plastic, but by applying this method, we were able to mix and knead the dry powder uniformly into the clayey sludge, thereby achieving granulation with minimal loss of strength. However, as the dry powder content increases, the amount of quicklime decreases, which tends to decrease the binder binding strength. Therefore, the dry powder content can be adjusted within the range allowed by the required granule strength.

[0038] Next, we conducted experiments using different combinations of operational factors and found that there exists a range in which a phenomenon called choking occurs, which causes clogging and makes it difficult to move the rod 3 of the vibration mixer 1 and discharge the granulated material. Because these optimum ranges vary depending on the characteristics of the clayey sludge and the model, it is not possible to quantitatively determine a range. However, we found that choking can be suppressed by adjusting, for example, the weight, amplitude, and frequency of the vibration source 4 of the vibration mixer 1. The particle size of the granulated material changes depending on the amount of quicklime added to the clayey sludge. As the amount of quicklime added decreases, the particle size of the granulated material increases, resulting in the production of coarse granulated material. However, when coarse granulated material with a particle size of approximately 10 mm or more is produced, the clayey sludge becomes too sticky, causing choking. Therefore, we investigated operating conditions within the operating range of this method that would allow stable production of coarse granulated material. As a result, it was found that there is an operating range in which choking can be suppressed and coarse granules can be stably produced without overload operation by adjusting the movement of the rod 3 of the vibration kneader 1. The movement of the rod 3 can be controlled, for example, by adjusting the weight of the plumb line, both amplitudes, and frequency of vibration. This is thought to be because the movement of the rod 3 changes depending on how the centrifugal force and rotational force are applied by the vibration kneader 1, which changes the compaction and sliding of the raw materials and the thixotropy of the viscous sludge.

[0039] As described above, granules with uniform particle size and adjustable particle size depending on the application can be produced from clayey sludge, and they have sufficient strength for practical use. This method eliminates pre-granulation processes such as drying, grinding, and moisture adjustment. Instead, clayey sludge is directly charged into the vibrating mixer 1, and particle size can be adjusted by adjusting the amount of quicklime added to produce granules. Furthermore, while conventional granulators often produce granules with a wide particle size distribution, requiring sieving before commercialization, this method produces granules with a uniform particle size, which may allow direct use without sieving. Furthermore, this method produces strong granules due to the synergistic effect of the quicklime and the vibrating mixer 1. The binding force of the quicklime is more efficiently exerted than in conventional granulators, potentially reducing the amount of quicklime added.

[0040] The granulation moisture content varies depending on the granule particle size, but the larger the granule particle size, the higher the optimum granulation moisture content tends to be. However, even the optimum moisture content for coarse granules with a particle size of 20 mm or more does not exceed 20% by weight. Therefore, since dehydrated cake and sun-dried clayey sludge contain approximately 20% by weight of moisture, there is no shortage of moisture required for granulation. The moisture content of the clayey sludge alone is sufficient for granulation.

[0041] Furthermore, if the granulation strength is within the range permitted for the intended use, dry powder may be used as a moisture adjuster in places where dry powder is easily available. By applying this method, the dry powder can reduce the need for expensive quicklime, allowing for economical and efficient moisture adjustment. As with clayey sludge, there are no restrictions on the dry powder components other than those limited to the intended use of the granulation material. While finer particle size is preferable, the inclusion of somewhat coarser particles is not a problem. However, adding dry powder tends to reduce the strength of the granulation material, so dry powder can be added only within the range of strength that is practical. Dry powder is an effective means of treating dust and other wastes.

[0042] The amount of quicklime added is adjusted according to the granule particle size, but the appropriate amount to be added varies depending on the type of clayey sludge to be treated, such as its heat generation, ease of steam evaporation, and specific heat.

[0043] The present invention will be described in more detail below with reference to test examples. However, the present invention is not limited to the following test examples. (Test Example C) In this method of applying the present invention, clayey sludge (converter sludge, sludge moisture content of 25% by weight before treatment) to which quicklime had been added was charged into a vibratory mixer and granulated by vibration. Figure 5 shows the results of Test Example C. As shown in Figure 5, the relationship between the amount of quicklime added and the average particle size of the granulated material was confirmed. A Vibro Explorer manufactured by Abe Iron Works Co., Ltd. was used as the vibratory mixer. By adjusting the amount of quicklime added to achieve a granulation moisture content of 15% by weight or more, coarse granules with a particle size of 10 mm or more could be produced. Furthermore, increasing the amount of quicklime added reduced the granulation moisture content, allowing for the production of fine granules. Furthermore, the drop strength index exceeded 80%, indicating that granules strong enough for practical use could be produced. Clayey sludge has a high iron content and is suitable for recycling in steelmaking, so the coarse granules can be reused as an auxiliary material for steelmaking, and the fine granules can be reused as raw material for sintered ore for blast furnaces.In both cases, the lime component is effectively utilized in steelmaking, so the economic benefits of using quicklime are realized.

[0044] (Test Example D) Test Example D is a test example in which dry powder was used to adjust the moisture content. Figure 6 shows the results of Test Example D. As shown in Figure 6, the relationship between the amount of quicklime added and the granulation moisture content, as well as the strength (crushing strength), was confirmed for each of the cases where no dry powder was added, where 10% by weight of dry powder was added, and where 20% by weight of dry powder was added. As the amount of dry powder added increased, the granulation moisture content decreased, resulting in a change in the granulation particle size. Furthermore, although the crushing strength was slightly lowered by adding dry powder, it was still within a range that could be handled, making it possible to economically granulate using dry powder with reduced quicklime.

[0045] (Test Example E) In this method, as the particle size of the granulated material increased, choking occurred in the vibration mixer, increasing the operating load and making it difficult to discharge the granulated material. Therefore, we investigated whether choking could be suppressed by adjusting both amplitudes of the vibration mixer. Figure 7 shows the results of Test Example E. As shown in Figure 7, the results are shown for varying both amplitudes within a vibration acceleration range of 4G to 7G. The clayey sludge was converter sludge, and the sludge moisture content was 21% by weight before treatment. For each vibration acceleration, the amount of quicklime added was varied by 8%, 11%, and 14% by weight. For example, when coarse granulation was performed with both amplitudes of 12 mm while maintaining a vibration acceleration of 6G, choking occurred, making discharge difficult. However, by changing the vibration frequency from 50 Hz to 60 Hz and both amplitudes to 8 mm, the difficult discharge condition was resolved and discharge became possible. This is thought to be because the rod motion changes due to differences in the way the centrifugal force and rotational force are applied in the vibration mixer, which changes the compaction and sliding of the raw materials and changes the thixotropy of the viscous sludge.In addition, when the vibration acceleration was in the range of 5G to 6G, if both amplitudes were in the range of 7mm to 8mm, the occurrence of choking could be suppressed and good granulation was possible.

[0046] Although the present invention has been described above with reference to the embodiments, the above embodiments are merely illustrative of specific examples of how the present invention can be implemented, and the technical scope of the present invention should not be construed as being limited by these embodiments. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features.

Claims

1. A process for adding an additive that has a water absorbing effect and a heat generating effect to clayey sludge, which is a sticky sludge containing 15% to 25% by weight of water; a step of loading the clayey sludge to which the additives have been added into a vibratory kneading device equipped with a drum containing rods or balls, and converting the clayey sludge into powder or granules by causing circular vibrations in the drum with a vibration acceleration of 3 G or more and 8 G or less.

2. 2. The method for treating clayey sludge according to claim 1, wherein the additive is quicklime.

3. 3. The method for treating clayey sludge according to claim 1, further comprising adding dry powder to the clayey sludge.

4. 3. The method for treating clayey sludge according to claim 1, further comprising adding a heat-generating agent to the clayey sludge.

5. 3. The method for treating clayey sludge according to claim 2, wherein, when the clayey sludge contains oil, the clayey sludge containing the oil is mixed with the quicklime, and the mixture is left for a predetermined period of time before being charged into the vibratory kneading device.

6. 6. The method for treating clayey sludge according to claim 5, further comprising adding an alkaline agent after leaving the sludge for the predetermined period of time.

7. 3. The method for treating clayey sludge according to claim 1, wherein the granulated material is produced by adjusting the moisture content to 20% by weight or less.

8. 8. The method for treating clayey sludge according to claim 7, wherein the granulated material has a particle size of 10 mm or more and the moisture content is adjusted to 15% by weight or more.

9. 3. A method for treating clayey sludge according to claim 1, wherein the occurrence of choking is suppressed by adjusting at least one of the weight, amplitude, and frequency of the weight of the vibration mixer when producing the granulated material.