JP7165349B2 - Sludge drying method - Google Patents

Description

The technology disclosed in the present specification relates to a sludge drying method .

Patent Documents 1 and 2 disclose techniques for producing solid fuel using sludge with a high water content and an odor. Patent Literature 1 discloses a method of adding coffee grounds and organic precipitated sludge to activated sludge having a high water content and drying the sludge in order to eliminate odors. In Patent Document 1, coffee grounds having a moisture content of 50 to 80% are mixed and stirred at a weight ratio of 0.5 to 2 times that of activated sludge. As the organic sedimentation sludge, the sludge generated when waste water containing emulsion or latex is subjected to coagulation sedimentation treatment is used. This organic precipitated sludge effectively promotes drying of the activated sludge.

The solid fuel production method disclosed in Patent Document 2 is as follows. Granular dry matter is added to a mixture of high-moisture organic sludge and food waste, which is then stirred and dried to obtain a solid fuel. The dried granules to be added are obtained by previously mixing high water content organic sludge and food waste with the same composition, and then drying to make granules having a water content of 20% or less and a particle size of 5 mm or less. Food waste includes coffee grounds, wheat bran, rice bran, dried bean curd refuse, and the like. When using coffee grounds as food waste, the mixing ratio of high water content organic sludge and food waste is as follows: high water content organic sludge: food waste (moisture content 60%) = 1: 0.4 to 1.0 (weight ratio) is preferred. In the case of dried coffee grounds, a ratio of high water content organic sludge:food waste (dry)=1:0.2 to 0.5 (weight ratio) is said to be preferable.

Patent document 2 proposes to return part of the resulting dried granules to the drying step of the next formulation (mixture of high water content organic sludge and food waste). The ratio of the blend to the dry granules to be returned is blend: dry granules = 1:0.1 to 1.5 (weight ratio). Patent Document 2 also states that it is preferable to add organic sedimentation sludge generated when waste water containing emulsion or latex is subjected to coagulation sedimentation treatment.

JP 2012-122044 A JP 2014-185307 A

The inventors of Patent Literatures 1 and 2 have further conducted tests and studies, and have endeavored to improve the technique for more easily treating sludge. In Patent Literature 1, food waste (coffee grounds) and organic precipitated sludge function as a drying accelerator that accelerates the drying of sludge. In Patent Document 2, the dried granules (mixed and dried organic sludge with a high water content and food waste (coffee grounds)) function as a drying accelerator that speeds up the drying of the sludge. In Patent Documents 1 and 2, coffee grounds (containing water) is mixed at a weight ratio of about twice that of sludge. In the case of dried coffee grounds, it is mixed at a weight ratio of about 0.5 times the sludge (Patent Document 2).

The inventors of the present application have found that by using a larger amount of coffee grounds as a drying accelerator for the sludge, it is possible to dry the sludge beyond expectations.

The sludge targeted by the present invention is organic sludge and livestock manure. Combining these two together, it is a huge amount of waste that accounts for about 50% of all industrial waste (120 million tons/year of organic sludge and 100 million tons/year of livestock manure). If the average processing cost at present is about 10 yen (processing cost and transportation cost), the scale of the processing business is about 2 trillion yen. The inventors have conducted studies on the market to reduce the volume of various organic sludges and livestock manure and to improve the added value of excreta using the technology based on the previous inventions (inventions of Patent Documents 1 and 2). rice field. As a result, the following points became clear. The number of business establishments that discharge organic sludge is enormous. Moreover, the amount of sludge discharged per day ranges from about 5 kg/day to 100 tons/day. They are roughly classified into three types according to their scale. In other words, it is classified into small-scale facilities (1 ton or less), medium-scale facilities (1 to 10 tons), and large-scale facilities (10 tons or more) according to the daily discharge amount. Among them, small-scale facilities occupy more than 95% of the total. In those small-scale facilities, it is not possible to invest in sludge treatment due to the investment effect. Therefore, they are processed at extremely high processing and transportation costs (20-35 yen/kg).

Why is this happening? This is because the conventional sludge treatment technology is only intended for medium- and large-scale facilities and requires a huge capital investment. As an example, in the case of sewage treatment plants, there are more than 10 locations nationwide (all of which are large-scale facilities that generate more than 50 tons of sewage sludge per day), and large-scale drying and carbonization of sewage sludge mainly using carbonization treatment systems. A system has been introduced to turn sewage sludge into solid fuel. The Japanese Industrial Standards (JIS) for solid fuel from sewage sludge has also been enacted, and it is believed that capital investment will continue to advance, centering on sewage sludge mass discharge facilities (50 tons/day or more). However, the equipment cost is on the order of several billion yen to eight billion yen.

On the other hand, 95% of the facilities that discharge organic sludge are small-scale facilities that discharge less than 1 t/day of sludge per day. Taking chemical facilities as an example, facilities that manufacture emulsion/latex adhesives and paints (both water-based), as well as automobile, electrical, chemical, and other facilities that use these water-based adhesives and water-based paints. A large amount of washing water is generated from washing, etc., after using adhesives and paints from various businesses such as lumber. There are a large number of business establishments throughout the country that generate tens of kg to 1 t/day of wastewater treatment sludge by treating it.

However, the reality is that no means, including treatment methods, have been developed for the sludge discharged from these facilities. This is because it is not possible to make a large investment in these facilities, and instead of investing in equipment, it costs a waste disposal company as industrial waste (processing and transportation costs are about 25 to 40 yen/kg). It was common to think that it would be better to take out the waste and have it processed. However, in recent years, it has become inevitable that processing costs will increase in the future due to various problems such as excess compost and limited use of cement. For this reason, if sludge discharge facilities cannot stably treat sludge in the future, it may affect the survival of the company.

Based on these current situations, the inventors of the present application tried to change the way of thinking. It would be epoch-making if we could apply the technology we have developed so far, not only for large-scale facilities but also for small-scale facilities with analog-like facilities, which can process with low investment and can reduce processing costs. I decided that it would be a scheme. For that reason, inexpensive analog equipment for small-scale facilities was a very important point in completing the invention. We tried to examine various commercially available batch-type agitators (equipment). The following six points are criteria for selection. (1) It should be inexpensive. (2) the facility functions as a container for the input; (3) It should be a simple facility that can be used with just an ON-OFF operation. (4) Drying of the granules is accelerated by agitation, not kneading. (5) Equipment should be used with as little powdering as possible. (6) It should be able to quickly disperse and mix the slurry by adding it to the dried granules. As a result of examination, as a result of examination, the one corresponding to the smallest scale facility that satisfies these six criteria is a horizontal basin type with stirring blades (e.g. mortar mixer), and if the scale becomes larger, , a ribbon-type mixer (with ribbon-shaped blades) was selected as the most suitable stirring equipment, satisfying the six criteria. By using these facilities as stirring dryers, it is possible to provide a system that can be applied to small-scale facilities (sludge volume of 1 t/day or less), and a scheme that can be applied to general facilities from small to large scale. can be provided.

The inventors have so far developed a technology for obtaining solid fuel by efficiently drying high water content sludge using coagulating sedimentation sludge and coffee grounds generated when emulsion or latex-containing wastewater is coagulated ( Patent Documents 1 and 2). The target sludge is sewage sludge, livestock manure treatment sludge, food sludge and coagulated sedimentation sludge discharged from various factories, grease trap sludge and paper sludge generated in kitchens related to eating and drinking, etc. occur in large numbers. These sludges have a very high moisture content (70% or more) and are accompanied by an odor, making them difficult to handle. Such sludge has hitherto been requested to be collected by a specialized trader, requiring a considerable cost for treatment. A survey of market needs revealed that although it would be effective to increase the value of sludge as a solid fuel, there was a greater need for a technology that rapidly reduced the volume of sludge at a low cost.

The inventors investigated whether drying could be accelerated without using coagulated sedimentation sludge. Sludge is discharged daily. Rather than storing odorous sludge and processing a large amount of it at once, it is better to dry the sludge generated on the same day (or in a short period of time) to reduce the volume and make it odorless, even if it is a small amount. Business establishments that generate sludge continue to generate an almost constant amount of sludge every day. These items are stored at the business site until they are collected by a disposal company. Accumulating muddy matter with a strong odor on the premises is not good from an environmental or sanitary point of view. The inventors set up the above-mentioned stirring dryer (mortar mixer or ribbon mixer) for the sludge generated every day, and simply throw the generated sludge into it, and the sludge can be treated automatically by natural drying. Assumed system. An attempt was made to develop a drying accelerator that can be used in such a method.

When considering the drying accelerator, the focus is usually on how the object (sludge) can be dried with a small amount of the drying accelerator. On the other hand, the amount of coffee beverages sold in the market is enormous, and a large amount of coffee grounds is discharged. Along with this, a large amount of coffee grounds is discharged as industrial waste all over the country. Moreover, no other effective recycling process has been established for coffee grounds. Some say that it has a deodorant function and uses fuel, but in reality, most coffee grounds are discharged as waste (negative raw materials) to processing companies and processed with compost, etc. is the reality. Moreover, some problems have been pointed out regarding the use as compost, and at present, even the manufacturers of discharged drinking water do not have effective recycling prescriptions. Therefore, the inventors reversed the idea and tried to dry a small amount of sludge using a relatively large amount of coffee grounds relative to the amount of sludge, although it was presumed that it would be inefficient.

The inventors have found that when sludge with a high water content of 1/3 or less by weight is mixed and stirred with a drying acceleration material mainly composed of coffee grounds, it can be dried in a short time and the mixture after drying is good. We found that it can be reused as a drying accelerator. If it is more than 1/3, the water content immediately after mixing becomes high, and a long period of stirring is required to reduce the water content of the mixture to 25% or less. As a result, the consumption of electrical energy required for stirring is greatly increased, resulting in an increase in processing costs. When the sludge is 1/3 or less, the normal stirring time is 8 hours, and when the sludge is 1/3 or more, it takes 12 hours or more. It is naturally expected that the drying will be accelerated as the ratio of sludge to coffee grounds is reduced, but the idea of using the drying accelerator in an amount three times or more that of the sludge is not common sense. This is because the amount of sludge exceeds the area of "promoter", and it is presumed that the sludge can be treated with less than half the capacity of the stirring dryer (for example, mortar mixer or ribbon mixer), resulting in poor efficiency.

However, as mentioned earlier, it is better to be able to treat even small amounts of sludge daily. The inventors repeated trial and error in search of a lower-cost drying method, and found that if the amount of sludge mixed with the drying accelerator is reduced to 1/3 or less by weight, it is possible to simply stir without adding heat. It has been found that the mixture can be dried to a moisture content of 25% or less in a short period of time. A moisture content of 25% is a moisture content that can be reached by natural drying. There is no occurrence or decomposition, and it is sufficient for volume reduction. In particular, drying by the natural drying method can be almost odorless when the dry matter is dried to 25% or less. Moreover, the dried mixture can be newly used as a drying accelerator. That is, a predetermined amount of sludge can be added on the next day after drying the mixture by adding 1/3 or less of the weight of the sludge to the drying accelerator. There is no need to modify the dried mixture, just add new sludge every day and stir and mix.

It is presumed that if the amount of the drying accelerator is much larger than that of the sludge, the sludge will be finely dispersed during agitation, and the drying will be accelerated due to the moderate cohesion and water resistance of the coffee grounds. Furthermore, the agitation causes the particles to be dispersed and granulated, and the diffusion effect further promotes drying. The dried mixture becomes granules of 3-5 mm or less. The proportion of coffee grounds decreases each time the mixture obtained by mixing, stirring, and drying the sludge and the drying accelerator is reused as a new drying accelerator. However, the sludge dries quickly because the sludge is widely spread in a large amount of particulate material (ie, drying accelerator). As a result, the drying efficiency is improved by repeatedly drying a small amount of sludge in a large amount of drying accelerator.

The dried mixture cannot be reused as a drying accelerator forever, but if the amount of sludge input is adjusted, the sludge can be dried continuously 15 times or more without adjusting the composition. That is, the drying accelerator disclosed in the present specification is a mixed dried product obtained by mixing and drying sludge with a high water content at a weight ratio of 1/3 or less with respect to the initial drying accelerator. It can be reused at least 15 times as an accelerator. Assuming that there are about 25 working days from 30 days a month to 25 days excluding holidays, the sludge is dried every day with only component adjustments (including replacement with new drying accelerators) less than twice a month. be able to.

The drying accelerator disclosed in the present specification contains coffee grounds as a main component and has a moisture content of 25% or less. The drying accelerator disclosed in the present specification is preferably coffee grounds alone or a mixture of coffee grounds and sludge containing coffee grounds at a solid content weight ratio of 30% or more. The solid content weight ratio of 30% means that 30% or more of the total weight of the solid content of the coffee grounds and the solid content of the sludge is coffee grounds.

The drying accelerator disclosed in the present specification is a mixture obtained by mixing and stirring sludge with a high water content at a weight ratio of 1/3 or less with respect to the drying accelerator and drying the sludge as a new drying accelerator. Reusable 15 times or more. That is, it is possible to continue adding new sludge to the initial drying accelerating material every day and drying it for one month.

The present specification provides a method for drying sludge using the drying accelerator described above. First, sludge with a high water content is mixed with the drying accelerator disclosed in the present specification at a weight ratio of 1/3 or less and stirred to reduce the water content to 25% or less (first step). Next, fresh sludge is mixed with the dried mixture obtained in the first step at a weight ratio of ⅓ or less and stirred to reduce the moisture content to 25% or less (second step). From the second step onwards, part or all of the dried mixed material obtained in the previous step is further mixed and stirred with new sludge at a weight ratio of 1/3 or less to reduce the moisture content to 25% or less. repeat. Here, after the second step, adjust the amount of another new sludge so that the solid content weight ratio of coffee grounds in the mixture of sludge and coffee grounds does not fall below 30%, or add a new drying accelerator. Good. By keeping the solid content of the coffee grounds at a weight ratio of 30% or more, the sludge does not form clumps, and when stirred, the sludge is finely dispersed. guessed.

More specifically, considering it as a box that can treat sludge every day as described above, an open stirring dryer (mortar mixer, ribbon mixer, etc.) is filled with a drying accelerator in advance, and the weight ratio is 1/3 or less of the drying acceleration material is put in and dried by stirring and drying. The mixed dried product after drying can be reused at least 15 times or more as a new drying accelerator. When using a stirring dryer, it is not necessary to apply heat for drying, and the only energy required is electric energy for stirring (of course, drying by heating is not denied).

In order to prevent the solid content weight ratio of coffee grounds from falling below 30%, it is preferable to adjust the amount of another new sludge or add a new drying accelerator. In addition, since the capacity of the stirring device is also limited, it is advisable to periodically remove a predetermined amount from the mixture obtained in the previous step. In the process, the solid content of the sludge remains in the dryer due to the continuous input of sludge, so the weight of the mixed dried matter (drying accelerator) in the dryer gradually increases. Therefore, in order to adjust the amount of the mixed dried matter (drying accelerating material) in the dryer, the mixed dried matter (drying accelerating material) is extracted from time to time, so that the mixed dried matter (drying accelerating material) in the dryer be maintained in an appropriate amount. Furthermore, as the number of continuous sludge inputs increases, the solid content weight ratio of the sludge and coffee grounds in the mixed dry matter continuously changes. That is, as the number of sludge inputs increases, the solid content weight ratio of the coffee grounds decreases and the solid content weight ratio of the sludge increases. At that time, when the solid content weight ratio of the coffee grounds is less than 30%, the drying acceleration function is gradually lowered. If this happens, either add new coffee grounds to restore the drying acceleration function, or replace the entire drying acceleration core material. As a result, fine particle dispersion of sludge, which functions as a drying accelerator, is restored, and drying is accelerated in combination with appropriate cohesion and water resistance of coffee grounds.

Details and further improvements of the technique disclosed in this specification are described in the following "Mode for Carrying Out the Invention".

It is a figure explaining the drying method of an Example. It is a table of test results. It is a graph of test results. 10 is a graph of another test result; It is a graph of a comparative example. It is a table|surface which shows the test result of 2nd Example.

The sludge to be dried includes sewage sludge, livestock manure sludge, food sludge and coagulated sedimentation sludge discharged from various factories, grease trap sludge and paper sludge generated in kitchens related to eating and drinking. These sludges are difficult to handle because they have a very high moisture content (usually 70% to 90%) and are accompanied by an odor. Such sludge has hitherto been requested to be collected by a specialized trader, requiring a considerable cost for treatment.

INDUSTRIAL APPLICABILITY According to the present invention, sludge can be dried quickly and inexpensively by using coffee grounds, which are industrial waste, as a drying accelerator. Other than coffee grounds, no effective recycling process has been established. Some say that it has a deodorant function and uses fuel, but in reality, most coffee grounds are discharged as waste (negative raw materials) to processing companies and processed with compost, etc. is the reality. Moreover, some problems have been pointed out regarding the use as compost, and at present, even the manufacturers of discharged drinking water do not have effective recycling prescriptions.

A dried mixture of coffee grounds and sludge (dried mixture) can be reused as a new drying accelerator. By repeating the process of mixing and stirring the sludge with the drying accelerator and mixing and stirring the resulting dry mixture with new sludge, it becomes possible to treat the sludge at a lower cost. As the process is repeated, the proportion of coffee grounds in the dry mixture decreases. Fresh sludge can be dried in general comparable to higher proportions. Of course, the drying accelerator cannot be reused infinitely, but by adding a new drying accelerator (that is, dried coffee grounds) every time the reuse cycle is repeated several times to several tens of times, it can be reused. The drying promotion effect returns. As will be described later, tests have shown that it can be repeated at least 15 times.

Although the drying accelerator of the present invention can be reused, it is preferable that the first drying accelerator to be added is mainly composed of coffee grounds having a water content of 25% or less. All of the drying accelerator may be coffee grounds, or it may be a mixture of sludge and coffee grounds, and the ratio of coffee grounds to the total solid weight of coffee grounds and sludge is 30% or more in solid content weight ratio. I hope you are. When sludge with a high water content is mixed and stirred at a weight ratio of 1/3 or less with respect to such a drying accelerator, not only the sludge dries quickly, but also the dried mixture can be used as a new drying accelerator about 25 times. can be reused. Due to the use of coffee grounds, odors are also eliminated in the dried mixture.

An embodiment of the sludge drying method will be described with reference to FIG.

(First step) A new drying acceleration material 3 is put into the mixer 2 (A). As the mixer, for example, a general-purpose mixer such as a mortar mixer or a ribbon mixer may be used, but it is desirable that the mixer is an open type in which the inlet is always open. The drying accelerating material 3 containing coffee grounds as a main component has a moisture content of 25% or less and is in the form of granules with a size of about 3 mm. A high water content sludge 4 having a weight ratio of 1/3 or less of the drying acceleration material 3 is put into the mixer 2 (B). A mixture of the drying acceleration material 3 and the sludge 4 is mixed and stirred by the mixer 2 to reduce the moisture content to 25% or less (C). Since the weight of the drying accelerator 3 is at least three times greater than the weight of the sludge 4 to be fed, the sludge diffuses into the drying accelerator 3 as the mixing and agitation is started, and becomes granular due to the cohesive force and water resistance of the coffee grounds. become. When the sludge becomes kneaded, it adheres to the blades of the mixer 2, resulting in a significant decrease in drying efficiency. The sludge is quickly granulated by using a large amount of the drying accelerator 3 compared to the sludge to be fed. The sludge is dried to a moisture content of 25% or less in one day.

(Second step) New sludge 4 with a high water content is added to the mixture with a water content of 25% or less obtained in the first step, and mixed and stirred. This step consists of the step (C) in FIG. 1 and the subsequent step (B). That is, the mixed dried product obtained in the previous first step is reused as a new drying accelerator. The amount of the sludge 4 to be introduced here is a weight ratio of 1/3 or less of the mixed dry matter having a moisture content of 25% or less obtained in the first step. Compared to the first step, the proportion of coffee grounds in the new drying accelerator is reduced, but the weight of the drying accelerator is large relative to the high water content sludge 4, so the sludge 4 can be dried It diffuses into the accelerator and granulates instead of kneading. In the second step as well, the newly added sludge and the drying accelerator are mixed and stirred until the moisture content of the mixture becomes 25% or less (from (B) to (C) in FIG. 1). Also in this case, the water content decreases to 25% or less in one day.

(Third step) New sludge 4 with a high water content is further added to the dried mixture having a water content of 25% or less obtained in the second step, and the mixture is stirred. This third step is a repetition of the second step. The amount of the sludge 4 to be added here is also the weight ratio of 1/3 or less of the mixed dry matter obtained in the previous step (second step), as in the case of the second step.

Thereafter, the third step is repeated. That is, (B) and (C) of FIG. 1 are repeated. However, if this is left as it is, the capacity of the mixed dry matter in the mixer 2 will increase. Before the volume of the mixed dry matter in the mixer 2 exceeds the allowable value of the mixer 2, the high water content sludge 4 is added after removing the appropriate amount of mixed dry matter from the mixer 2. This process corresponds to moving from (C) to (B) via (D) in FIG.

Further, when the third step is repeated, the proportion of coffee grounds in the drying accelerator decreases. The third step cannot be repeated infinitely. After determining the degree of dryness of the mixture of sludge and drying accelerator, add a new drying accelerator 6 (containing coffee grounds with a moisture content of 25% or less in a solid content weight ratio of 30% or more) at an appropriate timing, and mix and stir. . This process corresponds to moving from (B) to (C) via (E) in FIG.

A large amount of sludge can be dried as a result by repeating mixing and stirring after adding a drying accelerating material of 3 times or more by weight to the sludge with high water content.

2 and 3, test results of the drying method disclosed herein are shown. FIG. 2 is a table showing test results, and FIG. 3 is a graph showing changes in moisture content and air temperature on the next day of a mixture obtained by mixing and stirring sludge and a drying accelerator. 30 [kg] of the drying accelerator was added to the mixer on the first day. The sludge to be fed is food sludge and has a moisture content of 90%. The 3rd and 10th days corresponded to Sundays, and no new sludge was added.

Every day except Sunday, 6 [kg] of sludge is added and mixed and stirred. The stirrer used was a mortar mixer with a capacity of 100 [kg] or more, so the mixture was not taken out until the 11th day.

Since the added dried sludge increases, the solid content weight ratio between the sludge and the drying accelerator increases day by day. The weight ratio of the sludge after one day and the drying accelerator was sludge:drying accelerator=0.1:5. The weight ratio after 11 days was sludge:drying accelerator=1:5. The solid content of the added sludge remains in the drying accelerator, but the water evaporates.

Since the average temperature was low on the second day, the moisture content rose to 23.38 [%] the next day, but on the other days, the moisture content the next day was generally 20 [%] or less. Up to the 11th day, 6 [kg] was added every day except Sunday, but the moisture content on the day after the final day was 19 [%], indicating that the effect of the drying accelerator was not reduced.

Another test result is shown in FIG. FIG. 4 shows the results of a test in which sludge was mixed with a dryness promoting agent of coffee grounds alone at a ratio of drying promoting agent/sludge=3/1 and stirred every day. The graph shows the component ratio (weight ratio of coffee grounds solids to sludge solids) after drying to a moisture content of 25% or less. FIG. 5 is a comparative example, and shows the results when the initial drying accelerating agent used had a solid content weight ratio of sludge and coffee grounds of sludge/coffee grounds=74/26. The leftmost "initial" graphs in FIGS. 4 and 5 show the ratio of sludge/coffee grounds in the drying accelerator before the sludge to be dried is added. FIG. 5 also shows the results of a test in which the drying accelerator/sludge was mixed and stirred at a ratio of 3/1 every day. That is, the comparative example in FIG. 5 shows the results when using a drying accelerating agent with a solids content of coffee grounds of less than 30%. In the comparative example, the limit of the number of times that it could be used repeatedly as a drying accelerator was 5 times. At the fifth stage, the solid content ratio of coffee grounds to the total weight of solids in the drying accelerator was 21.6%. From the 6th time, the moisture content became 26% or more, and the drying property decreased.

On the other hand, when coffee grounds alone was used as the initial drying accelerator (Fig. 4), there was no change in performance as a drying accelerator even when sludge was added continuously for 25 days. % or less was achieved. Furthermore, the particle size of the dry matter did not increase. The particle size after the 25th drying was 92% with a particle size of 3 mm or less. At the start, the particle size of 3 mm or less is 100%.

From the above results, coffee grounds with a water content of 25% or less and a content (solid content ratio) of 30% or more exhibit good performance as a drying accelerator and can be used repeatedly. Then, if a drying accelerator is added so that the content of coffee grounds with a moisture content of 25% or less does not fall below 30%, the sludge can be dried/reduced continuously every day (or every few days). becomes possible.

As another example, test results with a ribbon mixer are shown (FIG. 6). In this example, 50 kg of flocculated sludge was treated per day.

The test conditions are as follows.
・Agitating and drying equipment: Ribbon type mixer of 0.8 m ³・Drying accelerating material: 200 kg input ・Sludge input amount: 50 kg of coagulated sedimentation sludge with a sludge moisture content of 79% per day ・Agitation and drying time: per day 8 hours

Here, the coagulated sedimentation sludge is, more specifically, coagulated sedimentation sludge generated when emulsion or latex-containing wastewater is subjected to coagulation sedimentation treatment.

The measurement and check items are as follows.
・Measurement of moisture content: Measured on the day after input, before adding the sludge of the day ・Outside temperature: Continuous measurement with logger ・Measurement of weight: Measurement of weight inside agitator (once a week)
・Measurement period: 1 month (21 inputs)

In addition, the temperature in the table of FIG. 6 is the average temperature for 24 hours. With an increase in the number of times, generation of powders of 0.1 mm or less was hardly observed, and it became clear that the ribbon mixer does not powder as much as the mortar mixer. Sludge was put in once a day (21 times in total) every day except Saturdays and Sundays. It didn't cause any problems at all. That is, it was possible to suppress the water content to approximately 25% or less only by stirring for 8 hours per day each time.

The drying accelerator disclosed in the present specification is mainly composed of coffee grounds, which is an industrial waste, and can be obtained at a low cost. Moreover, no other effective recycling process has been established for coffee grounds. Some say that it has a deodorant function and uses fuel, but in reality, most coffee grounds are discharged as waste (negative raw materials) to processing companies and processed with compost, etc. is the reality. Moreover, some problems have been pointed out regarding the use as compost, and at present, even the manufacturers of discharged drinking water do not have effective recycling prescriptions. The drying accelerator disclosed in the present specification can be reused as a new drying accelerator by mixing and agitating sludge that is less than its weight.

In the case of reuse, the mixture can be reused many times by mixing and stirring less than the same weight ratio of sludge with respect to the drying accelerator. After each reuse, or after a specified number of reuses, a portion of the mixture may be removed to keep the total mixture below a predetermined tolerance. Also, while monitoring the particle size of the dried product, it is advisable to add a new drying accelerator (mainly composed of dried coffee grounds) at an appropriate number of times of reuse.

The following effects can be expected from the drying accelerator disclosed in the present specification and the sludge drying method using the same.
(1) In-facility treatment in small-scale facilities becomes possible at sites where sludge is generated.
(2) Since it can be treated at the sludge generation site, there is no need to carry out the sludge to the outside.
(3) Conversion to dry matter by volume reduction at the site of sludge generation (handling becomes easier and odor is improved).
(4) Waste is reduced by sludge volume reduction (can be reduced to about 1/3 to 1/4).
(5) Room-temperature drying is possible (heating cost is unnecessary), and odors in facilities are also improved.
(6) By continuously (every day) treating the generated sludge, it is hygienic because it does not need to be stored as sludge.
(7) The discharged dried matter can be effectively used as a drying accelerator. The discharged dried matter can be used as fuel, compost, etc.
(8) Equipment is simple and very inexpensive, and treatment costs can be reduced even in small-scale facilities.
(9) It is an energy-saving system and has the effect of reducing carbon dioxide.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or in the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims as of the filing. In addition, the techniques exemplified in this specification or drawings can simultaneously achieve a plurality of purposes, and achieving one of them has technical utility in itself.

Claims (5)

A drying accelerator for sludge, which is mainly composed of coffee grounds and has a water content of 25% or less , is mixed with sludge with a high water content in a weight ratio of 1/3 or less, and the water content is 25% or less. a first step of lowering to
A second step of mixing and stirring fresh sludge with the mixed dried product obtained in the first step at a weight ratio of 1/3 or less to reduce the moisture content to 25% or less;
After the second step, a part or all of the mixed dried product obtained in the previous step is further mixed and stirred with new sludge at a weight ratio of 1/3 or less, and the water content is 25 A sludge drying method that repeats lowering to % or less. After the second step, add new coffee grounds or switch to a new drying accelerator so that the solid content weight ratio of the coffee grounds in the mixed dried product does not fall below 30%. The sludge drying method according to claim 1 . After the second step, the weight of the mixed dried matter in the dryer increases due to the continuous introduction of sludge, so that a predetermined amount of dried matter is sometimes extracted from the dryer so that the stirring drying efficiency does not decrease. 2. The sludge drying method according to 2. 2. The sludge drying method according to claim 1, wherein the drying accelerating material is coffee grounds alone or a mixture of coffee grounds and sludge containing coffee grounds at a solid content weight ratio of 30% or more. The mixed dried product after mixing and drying the sludge with a high water content at a weight ratio of 1/3 or less with respect to the drying accelerator can be reused at least 15 times or more as a new drying accelerator. 5. The sludge drying method according to Item 1 or 4.

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