KR20060125636A - A new solid fuel like bituminous coal from organic sludge and preparation method thereof - Google Patents

Abstract

A new solid fuel containing sewage sludge, or organic sludges discharged from plant wastewater and livestock wastewater as a principal component and a manufacturing method of the solid fuel are provided to treat various organic sludges in an economic and eco-friendly manner and improve supply ratio of alternative energy remarkably. A manufacturing method of a solid fuel having physical properties similar to those of bituminous coal by using organic dewatered sludges comprises: a step(S11) of mixing 70 wt.% or more of organic sludge with 30 wt.% or less of at least one carbon-based additive selected from the group consisting of coke, coal and soot after weighing the organic sludge and the carbon-based additive; steps(S12,S13) of agitating the mixture while spraying at least one deodorizer selected from the group consisting of pyroligneous liquor, bamboo liquor and enzyme onto the mixture in an amount of 5 to 100 ppm of the mixture; and steps(S14-S17) of drying the mixture to a moisture content of 15% or less to obtain powder, and storing the obtained powder as it is, or storing the molded powder after molding the obtained powder.

Description

A solid fuel like bituminous coal from organic sludge and preparation method

1 is a sewage sludge thermal analysis curve

2 is a thermal analysis curve of bituminous coal

3 is a thermal analysis curve of solid fuel made by mixing sludge and anthracite coal

4 is a thermal analysis curve of solid fuel made by mixing sludge and coke

5 is a thermal analysis curve of a solid fuel made by mixing sludge and two kinds of carbon-based additives

6 is a sludge fueling process diagram of drying after mixing the sludge and additives

7 is a process diagram for fueling by mixing the additives after the first sludge drying

Sewage sludge, industrial wastewater sludge and livestock wastewater sludge, which are used as starting materials for producing the new solid fuel to be obtained in the present invention, are generated in the form of a dehydrated cake having a water content of 70 to 85% in an actual sewage and wastewater treatment plant. Based on the solids other than water, organic matters are contained in a small amount of 30% to as high as 70% or more, so that the calorific value of solids has a relatively high calorific value of 2,000kcal / kg to 5,000kcal / kg. Therefore, such organic sludge has been classified as a low carbon fuel in the academic field. In Korea, it generated 6.5 million tons per year as of 2004. Currently, most of the sludge is not supplied. Marine dumping or incineration. However, when the sludge treatment method was recognized as causing various social problems including environmental issues, the government banned sludge disposal of marine sludge until February 2011, and announced the principle of land treatment through recycling. It is very urgent to develop and distribute appropriate recycling technologies. Therefore, if the technology for fueling and recycling sludge is supplied, it is expected that groundbreaking electricity will be prepared not only for treating sludge but also for supplying alternative energy. Particularly, in order to recycle through sludge fuel treatment, the sludge has been thoroughly analyzed for physical properties, and based on this, carbonaceous additives of appropriate type are added thereto to produce solid fuel having properties similar to that of bituminous coal, which is the most commonly used fuel in the industry. The development and dissemination of this method is very important for sludge treatment and recycling as fuel. At present, Korea is an energy importing country with insufficient energy, and even though it has the lowest penetration rate of renewable energy among OECD countries, it does not use dry sludge with high caloric value of 2,000 to 5,000kcal / kg as fuel, and 75% of the amount generated. Given that dumping is being dumped at sea, landfilled or incinerated, it is urgent to spread the feasibility technology that is realistically possible.

Although efforts to recycle sludge have been made as an alternative fuel so far, generally, dewatered sludge contains 70 to 85% of water, which is a major obstacle to fueling, and sludge solid obtained through drying In the case of, the volatile content and the fixed carbon content, which are most important for determining the physical properties of the fuel, are composed in the opposite ratio of the existing coal-based fossil fuels. There is a lot of difficulty to overcome this situation.

[Table 1] Calorie and Components of Sewage Sludge, Livestock Sludge and Plant Wastewater Sludge

In order to examine the characteristics of sludge generated in Korea, Table 1 presents the calories and industrial analysis results for various sludge solids from the sewage, wastewater, and livestock wastewater treatment plants in six regions in Korea. This shows that the calories are distributed between 2,510 and 5,040 kcal / kg, and the content ratio of volatile matter to fixed carbon is distributed between 4.0 and 8.1. As shown in Table 2, the volatile matter / fixed carbon of fossil fuels is shown. The ratio of is in the range of 0.1 to 0.2, which is relatively high at the level of 0.7 in the case of bituminous coal having a relatively high volatile content, but this also shows a large difference in the level of 1/6 compared to the value of the sludge solids.

[Table 2] Calorie and Components of Carbon Fossil Fuels

The combustion curve of sewage sludge shown in FIG. 1 shows that the ignition temperature of sewage sludge starts in the region of 250 ° C., and the combustion peak is clearly separated into two in the region of 300 ° C. and 450 ° C. In the short combustion section of the low temperature range of 300 ℃, incomplete combustion occurs due to the release of a large amount of volatiles, and it does not lead to combustion in the 450 ℃ region where the second combustion peak is generated due to lack of oxygen and calories, and thus it is not suitable for use as a sole fuel. impossible. At the high temperature of 400 ℃ or higher, where most fossil fuels are burned and continuously supplying heat, combustible volatiles are volatilized at the same time and enter the combustion furnace.In the existing combustion system, the combustion process is impossible due to the lack of oxygen and the combustion process is stopped. Very likely to be. In order to overcome this, even in advanced Europe, when used in thermal power plants or cement kilns, only 3% or less of dry sludge is used as the main fuel.

Recently, in Korea, in order to recycle various sludge as fuel, combustible domestic waste and oil discharged from the city in sludge are mixed with auxiliary fuel, and clay or sand is mixed to manufacture existing coal briquettes or briquette model coal coal to improve formability. In addition, cases of solid fuels by mixing a large amount of coke and coal in sludge have been announced.

For example, Korean Patent Laid-Open Publication No. 94-14200 discloses a method and apparatus for extracting water from sludge using heated oil which dehydrates sludge and then splashes it in oil to use as fuel. No. 1084 discloses a solid fuel prepared by mixing pulp sludge with paraffin wax and then press molding with hexaamine potassium permanganate. Korea Patent Publication No. 94-204040 discloses a method for manufacturing solid fuel produced by molding, and various combustibles prepared by mixing calcium carbonate, zeolite and binder with wastes such as wood, waste paper sludge, etc., and then pressing them with a compression molding machine. A method of making charcoal from waste has been disclosed. In addition, Korean Patent Application Publication No. 99-74336, Korean Patent Publication No. 10-0319803, and Korean Patent Registration Publication No. 10-0419189 disclose methods for fueling waste by adding coal powder or petroleum coke to sewage sludge. have.

However, the conventional techniques are not only difficult to meet the optimum conditions of combustion because the materials of very different physical properties are mixed with each other, due to the large amount of pollution emissions due to incomplete combustion, etc., and the addition of an incombustible molding agent in excess, utilized as a self-containable fuel It is so difficult to do that it has not been put into practical use at all. In addition, in the method of adding coal powder or petroleum coke powder as a calorific reinforcing material, an additive is added in excess of the sludge from 25% to as much as 900% by weight to increase the calorific value of the sludge. Since 80% of the sludge has only 20% of solids, the amount of coal or petroleum coke added as a calorific enhancer is less than 1.25 to 45 times the amount of solids of the sludge. Rather than doing so, the country is adding sludge to coal and petroleum coke. That is, the existing patents consist of a much larger amount of additives than the sludge solids, and are mixed to be a fuel that uses sludge as an additive rather than a solid fuel containing sludge as a main component, and also adds excess coal or coke. In spite of this, the problem of odor generated in sludge is still not solved. As described above, fuels including sludge described in the existing patents can be said to be a technology that is practically difficult to spread on site due to cost burden and environmental odors caused by the use of excessive additives.

The present invention relates to a new solid fuel mainly composed of organic sludge discharged from sewage sludge, plant and livestock wastewater sludge, and a method for manufacturing the same, thereby solving various sludge treatment problems, and by adding a minimum amount of carbonaceous additives, In addition, it is intended to provide solid fuel with self-extinguishment and to solve the odor problem of the solid fuel resulting from the sludge to improve practicality. Solid fuel produced by the present invention can be said to be a solid fuel of a new concept that can replace the existing coal by having properties similar to the existing bituminous coal, and in the conventional sludge fuelization technology to add excess coal or coke To solve the odor problem that had been difficult to use solid fuel in the field by adding a deodorant such as wood vinegar. In other words, through the solid fuel production method proposed herein, to prepare a way to treat various organic sludge economically and environmentally friendly, and to provide an opportunity to dramatically improve the rate of alternative energy diffusion.

In the present invention, in order to achieve the above object, the main composition of the sludge solids obtained during the drying process during the process for fuelizing the organic dehydration sludge generated from sewage sludge, factory and livestock wastewater sludge, and volatilized condensed properties of the fuel The ratio of and fixed carbon is very important. It is more efficient to convert organic sludge to bituminous carbon and lactic acid properties due to the characteristics of constituents that are much higher than fixed carbon. In the present invention, additives such as coke, chute or coal may be used as a component that can increase the fixed carbon content before drying the sludge in order to match the physical properties of the final solid fuel prepared with sludge as the starting material. The mixture was mixed so as to be 30% or less by weight ratio to sludge. At this time, when the distinctive double-burning combustion curve, which is a characteristic of sludge, does not disappear, it is difficult to solve only one of the above additives. Bituminous coal and lignite are additives to fill the temperature region in which volatile components burn and the area in which fixed carbon burns. Alternatively, petroleum coke is mixed and dried to form a solid fuel.

In general, as shown in Table 1 and Figure 1, the characteristics of the sludge are 4 to 8 times higher than that of fixed carbon, which is mainly burned in the low temperature range. It has two combustion peaks, and when combustion starts near 200 ° C, excess volatiles are discharged before the sludge temperature rises sufficiently, resulting in incomplete combustion due to lack of oxygen, which is immediately discharged as soot. In order to solve this problem, when an excessive amount of combustion air is injected, the interior of the furnace is cooled, causing incomplete combustion, or in severe cases, the combustion process is stopped. Therefore, in order to convert sludge into solid fuel capable of self-sufficiency, the combustion peaks near 300 ° C and the combustion peaks formed near 420 ° C are connected to each other. Additives are needed to reinforce calories. As a material having such physical properties, lignite or bituminous coal, which is ignited at around 300 ° C. and generates the highest heat at 500 ° C., is most useful. However, most of them have a high volatile content similar to that of fixed carbon. Difficulties in controlling the carbon ratio Therefore, it is desirable to further add coke, chute or anthracite as an additive to reinforce the fixed carbon content of the sludge. Some coke or anthracite is ignited in the range of 400 ~ 450 ℃, and mainly burns at 500 ~ 700 ℃. When the fixed carbon content of sludge is too low compared to volatiles, only another combustion peak is formed as shown in FIG. Continuous combustion of the fuel may not be possible, and when the fixed carbon content of the sludge is high or the main combustion temperature of the fixed carbon reinforcement is located near the second combustion peak of the sludge, the combustion peak is somewhat as shown in FIG. Continuous fueled products can be obtained, but they are not considered perfect, and to further compensate for these shortcomings, it is necessary to further improve the combustion characteristics in the region of 350 to 500 ° C. As an additive to supply heat, additives composed of bituminous coal, lignite and petroleum coke are put together. As shown in Fig. 5, it is possible to manufacture a new solid fuel that can supply heat through continuous combustion from around 200 ° C at which combustion starts to 600 ° C at which combustion is completed, and the combustion characteristics of the solid fuel are shown in FIG. Combustion characteristics are very similar to those of the typical bituminous coal shown in.

However, these combustion characteristics cannot solve all the problems of combustion occurring in the combustor. In order to use the sludge fueled products in the combustion system using solid fossil fuel, the existing fuel and combustion conditions are Since they should be as similar as possible, an additional consideration to be made is the ratio of volatiles to fixed carbon. This ratio makes the supply of air necessary for the combustion process of fuel and the continuous combustion characteristics at high temperature similar to that of conventional fossil fuels, and operates by minimizing the change of combustion conditions in the existing fossil fuel combustion furnace or kiln. It can be said to be a very important factor to utilize solid fuel as an alternative fuel. In general, organic volatiles are high enough to account for 50 to 70% of the sludge solids. Therefore, in order to prepare them as the fuel having the bituminous coal and the aborted physical properties, which are the most used industrial fuels, the volatile content of the sludge solid fuel is 25 to 40%. Lower the fixed carbon content to 40 to 60%. Therefore, in order to satisfy this, the additives must be selectively mixed, and it is necessary to adjust the amount of the additive so that the weight ratio of the final fixed carbon to specific volatiles is about 1 to 0.4. By using the above method, the sludge solid fuel having a composition ratio similar to that of bituminous coal can be manufactured while making the most of the volatile content of the sludge while reinforcing fixed carbon components as necessary. It is possible to manufacture solid fuel which can be used in the existing furnace without significant change of combustion conditions. Therefore, a relatively low volatile content, a high fixed carbon content additive is required, and the higher the fixed carbon content, the higher the fixed carbon content of the sludge can be increased. Suitable candidates for such additives may include chutes or high caloric anthracite coals collected from coke, cogeneration or coal-fired power plant dust collection facilities. It is preferable to add a mixture of lignite or petroleum coke.

Carbon-based additives are generally added in the form of a powder of 2 mm or less in consideration of adsorption of the sludge with particles, and in order to homogeneously mix them with the sludge, it is preferable to provide a mixing step before the drying step. In addition, when these carbon-based additives are mixed, the viscosity of the sludge is lowered, thereby reducing the load of the dryer as compared to simply drying the sludge, so that the drying speed is about 20 to 40% faster. The fuelization process using this advantage is shown in FIG. In general, in the process of drying the sludge, the viscosity of the sludge is rapidly increased in the range of 50 to 30% of the sludge, there is a difficulty in conveying the sludge in the dryer and drying itself. In order to solve this problem, after first drying until the water content of sludge reaches 40 to 50%, when the carbon-based additives are mixed, the water content decreases to 30% or less, and the viscosity decreases rapidly. Drying is also possible, and additional drying may be omitted depending on the amount of additives, which can drastically reduce the energy required for drying. The related process is shown in FIG. 7.

In addition, one of the characteristics of fuels using sludge is odor problem. In particular, in the present invention mainly composed of sludge solids, the odor problem occurring in the sludge itself is more serious than the conventional method of mixing excess additives. And further processing is required to remove it. For this purpose, one or two deodorants selected from wood vinegar, bamboo vinegar liquor and enzyme are mixed as deodorant in the sludge and carbon-based additive mixing process as shown in FIGS. 6 and 7 and mixed at a ratio of 5 to 100 ppm relative to the mixture. In this process, the major odor components such as ammonia, hydrogen sulfide, and mercaptan contained in the sludge are changed into nonvolatile salts by organic acids or alcohols such as acetic acid contained in the deodorant, or by microorganisms. As it decomposes, it fundamentally blocks odors. Therefore, the odor problem of the sludge fueled product, which has not been completely solved even in the prior art, can be solved by this additional process, and the usability of the sludge solid fuel can be further improved due to the affinity of the solid fuel.

<Example 1>

An additive for reinforcing fixed carbon in 90.9% by weight of sludge with 87% water content collected from the sewage treatment plant at "A", a chute having a heat capacity of 7,410 kcal / kg, and 6,990 kcal / to fill the volatile combustion section and the fixed carbon combustion section. kg calorie coal was mixed at a ratio of 7.3% by weight and 1.8% by weight, and the amount of wood vinegar was mixed to about 50 ppm, and the calorie content of the dried sample was analyzed at 5,920 kcal / kg, and the volatile matter for fixed carbon was analyzed. The content ratio of was 0.8, which showed a similar value to that of bituminous coal with a volatile content ratio of 0.7 to fixed carbon.

[Table 3] Solid fuel conversion of sludge with 87% water content generated in sewage treatment plant

The final calorific value of solid fuel made by the above process by adding 8,680 kcal / kg of petroleum coke instead of chute as fixed carbon reinforcement was measured at 6,350 kcal / kg, and the ratio of volatile matter to fixed carbon was 0.8 It has been shown that both formulations can produce solid fuels with a high calorific value of 6,000 kcal / kg even at a mixing ratio of 90.9 wt% sludge to 9.1 wt% additives.

<Example 2>

Sludge with 85% water content generated in the livestock wastewater treatment plant at "A" was 4,610 kcal / kg of dry solids and 7.3 volatil to fixed carbon, which is higher than general sewage sludge. As shown in Table 4, 80.6 to 87% by weight of dehydrated sludge is mixed as a fixed carbon additive in a chute, coke, anthracite coal in a range of 8.7 to 17% by weight and in a range of 0 to 6.5% by weight of bituminous coal. The calorific value of the solid fuel made by mixing 30ppm of the mixture and drying it was obtained with a calorie value of at least 5,712kcal / kg to a maximum of 6,925 kcal / kg.

[Table 4] Solid fuel conversion of sludge with 85% moisture content generated in livestock wastewater treatment plant

The ratio of volatile matter to fixed carbon was obtained from 0.6 to 0.9. Petroleum coke contains about 15% of volatile matter in itself, and the sludge itself has a high volatile content. A high value of 0.9 was obtained. Although it is somewhat combustible, even if it is mixed with 83% by weight of sludge in the ratio of 17% by weight of petroleum coke, the volatile matter to fixed carbon ratio is 0.6.

[Table 5] Solid fuelization of sludge with a water content of 80% generated in the city's sewage treatment plant

<Example 3>

The water content of sewage sludge dewatering cake was about 80%, and the calorie content of solids was 3,810kcal / kg, which is similar to the value of sewage sludge produced in most sewage treatment plants in Korea. 83.3 to 87% by weight of this sludge is mixed with coke, chute, or anthracite in a coke, chute, or anthracite coal in an amount of 8.7 to 12.8% by weight and bituminous coal at a ratio of 1.7 to 4.3% by weight. After mixing, the calorific value of the dried solid fuel was obtained from 5,041 kcal / kg to 5,980 kcal / kg. At this time, the ratio of volatile matter to fixed carbon was maintained at 0.7 to 0.8 of bituminous coal and lactic acid. . In the case of solid fuel made by mixing 83.3 wt% of sludge, 12.5 wt% of coke and 4.2 wt% of bituminous coal, it is possible to produce solid fuel having a calorific value close to 6,000 kcal / kg even though the total amount of additive is 16.7 wt%. In the case of mixing 13% by weight of coke to 87% by weight of sludge, 5,615 kcal / kg of high-calorie solid fuel could be prepared.

<Example 4>

80% to 89.3% by weight of dehydrated sludge having a water content of 72% to the sewage treatment plant at the time of "bottle" is mixed with a fixed carbon additive in a chute, coke and bituminous coal at a mixing ratio of 1.8 to 17%, respectively, and wood vinegar is mixed. The calorific value of solid fuel produced by spraying, mixing, and drying to obtain 10 ppm was obtained at 4,510 to 5056 kcal / kg, and the ratio of volatile matter to fixed carbon was about 0.6 to 0.8, similar to that of bituminous coal. In order to obtain fuel, solid fuel having a high calorific value of 5,000 kcal / kg or more while maintaining the ratio of volatile matter to fixed carbon within the range of 0.6 to 0.8 can be obtained by mixing about 17% by coke alone. In this case, the ratio of fixed carbon is too high, which is impossible, and must be mixed with bituminous coal. In order to make solid fuel 5,500 kcal / kg or more high-calorie fuel, the content of additives is increased and mixed with 77% by weight of sludge, 12.3% by coke and 10.7% by bituminous coal, the amount of volatile matter for fixed carbon is 5,615 kcal / kg. A solid fuel with a ratio of 0.7 was obtained.

[Table 6] Solid fuel conversion of sludge with 75% water content generated in sewage treatment plant

The present invention is a new solid fuel which is economically and spontaneously combustible by mixing dehydration sludge generated after sewage treatment, plant wastewater treatment or livestock wastewater treatment, and a small amount of carbon-based additives therein, especially for volatile carbon for fixed carbon. The ratio of cobalt is similar to that of bituminous coal, which is the most used industrially, so that it can be used as a cheap solid fuel instead of bituminous coal in the existing bituminous coal. In addition, by solving the odor problem that could not be solved in the conventional sludge solid fuel treatment method, it is possible to eco-friendly fuel treatment, providing a revolutionary electricity as a realistic treatment method for the sludge treatment problem that is currently struggling with bulk treatment. It is expected to contribute greatly to the energy dissemination rate.

Claims (5)

Solid fuel composition made of organic dewatered sludge generated in sewage or wastewater treatment plant, the ratio of 70% by weight or more of the sludge, 30% by weight or less of one or more carbon-based additives selected from the group consisting of coke, coal and chute Solid fuel composition having a physical property similar to bituminous coal, including 5 to 100 ppm of one or more deodorants selected from the group consisting of wood vinegar, bamboo vinegar, and enzyme in a mixture consisting of The solid fuel composition according to claim 1, wherein the final weight ratio of the carbon-based additive to the solid content of the organic dewatered sludge is 1.5 or less. The solid fuel composition according to claim 1, wherein the weight ratio of volatile matter to fixed carbon of the mixture is 0.4 to 1. At least 70% by weight of organic sludge and at least 30% by weight of one or more carbon-based additives selected from the group consisting of coke, coal and chute (S11) and from the group consisting of wood vinegar, bamboo vinegar and enzyme Stirring (S12) while spraying (S13) at least one selected deodorant to 5-100 ppm of the mixture, and storing the powder obtained by drying (S14) the mixture at a moisture content of 15% or less (S15). Or, a solid fuel production method similar to bituminous coal using organic dewatered sludge, characterized in that it is produced by the step of storing through molding (S16) The method of manufacturing a solid fuel according to claim 5, further comprising a step (S21) of drying in advance so that the moisture content of the organic dewatered sludge is 30 to 50% before adding the carbonaceous additive and the deodorant.

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