Coffee grounds used as fuel for cement production

Abstract

To provide a method for processing coffee grounds, which are a type of waste, from a viewpoint of resource saving and energy saving, wherein the coffee grounds are treated so as to lessen impact on cement production and make effective use of a heat quantity, are used as a substitute for coal, and are dried during air transportation to improve handleability.SOLUTION: Coffee grounds are fed either alone or together with pulverized coal or waste plastic through a burner into the firing system in a cement clinker manufacturing facility equipped with a preheater 5, a rotary kiln 3, a calciner 4 and a cooler 7.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for treating coffee grounds, in which the coffee grounds are supplied to a calcination system of a cement clinker production facility. [Background technology]

[0002] The cement industry is a mass production and mass consumption industry, and resource and energy conservation are continuing to be top priorities. The production of cement clinker involves a firing process using a kiln, and the effective use of this kiln for waste disposal contributes to resource circulation. Another type of waste is coffee grounds, which have a calorific value similar to that of coal, and so it is desirable to treat them effectively.

[0003] Various methods for processing coffee grounds have been proposed. For example, Patent Document 1 describes a method in which waste containing coffee grounds is processed while still in garbage bags into a cement raw material or as part of a fuel to produce cement clinker. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-191059 A

[0005] The method of Patent Document 1 is an extremely useful technology from the viewpoint of industrially reusing waste materials including coffee grounds, but there are still problems to be solved in order to effectively treat the waste materials.

[0006] In general, the treatment of wastes etc. using a kiln has two aspects: one is aimed at treatment from the viewpoint of saving resources and energy, and the other is aimed at treatment itself. The method of the above-mentioned Patent Document 1 is to burn wastes including coffee grounds as a cement raw material or part of fuel in a rotary kiln of a cement clinker production facility, and it is described that the wastes including coffee grounds are supplied to the bottom of the kiln or the calciner. This is carried out for the purpose of treating the coffee grounds itself, and since the coffee grounds are charged from the bottom of the kiln like the raw cement, there are concerns about the impact on the quality and production efficiency of the cement clinker. In addition, there are problems such as not being able to effectively utilize the calorific value of the coffee grounds and not being able to use them as an alternative fuel to coal. Furthermore, when coffee grounds are discarded, they contain moisture, and in this state, they are poor in handling, as they adhere to the walls of the equipment. Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a method for processing coffee grounds, which is a type of waste, in a manner that minimizes the impact on the quality and production efficiency of cement clinker and allows for effective utilization of its heat, while also using it as a substitute for coal, and drying the moisture in the coffee grounds to improve their handleability, thereby enabling processing that is resource- and energy-saving. [Means for solving the problem]

[0008] According to the present invention, there is provided a method for treating coffee grounds, in which coffee grounds are supplied to a burning system of a cement clinker production facility and combusted, comprising the steps of: There is provided a method for treating coffee grounds, characterized in that the coffee grounds are dried and then fed to the roasting system through a burner.

[0009] In the production method of the present invention, (1) supplying the coffee grounds mixed with pulverized coal to the firing system through the burner; (2) supplying the coffee grounds mixed with waste plastic to the firing system through the burner; (3) The coffee grounds and the like are dried using gas discharged from the cement clinker production facility, and the temperature during the drying is 250°C or less; (4) The coffee grounds, etc. are dried by air currents in the air conveying line for conveying the waste plastics to the burner. Here, the coffee grounds and the like refer to coffee grounds, a mixture of coffee grounds and pulverized coal, and a mixture of coffee grounds and waste plastic. Effect of the Invention

[0010] In the present invention, the coffee grounds are supplied to the calcination system through a burner. In other words, the coffee grounds are used as part of the fuel, which reduces the impact on the quality of the cement clinker and production efficiency, and enables effective use of the heat. Furthermore, in the present invention, the coffee grounds are supplied to the calcination system through a burner, so the calorific value of the coffee grounds is effectively utilized for heating the system. Coffee grounds have a calorific value close to that of coal, and by serving as fuel for combustion, the high calorific value of the coffee grounds can be effectively utilized for cement calcination. Furthermore, the amount of coal used as fuel has been reduced compared to the past. By using coffee grounds as part of the fuel for combustion in the burner, it is possible to reduce the amount of coal used in the past. Furthermore, in the present invention, the coffee grounds can be dried using exhaust gas discharged from a cement clinker unit before being fed into the calcination system. By using the exhaust gas for drying, it becomes possible to effectively utilize the heat in the calcination system. Furthermore, in the present invention, the coffee grounds can be dried by the air current for pneumatic transport in the pneumatic transport line for transporting waste plastics to the burner. This process eliminates the need for a dryer or other process in advance. Furthermore, in the present invention, the coffee grounds are used in a dried state due to the drying process, which prevents them from adhering to equipment or piping, improves the handling of the coffee grounds, and makes them suitable for supply from a burner. Coffee grounds are originally uniform in particle size, less than 3 mm, and simply drying them greatly improves their handling. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a cement clinker production facility used in the present invention. [Diagram 2] FIG. 1 is a diagram showing a coffee grounds treatment process according to the present invention, in which a burner dedicated to coffee grounds is provided, and the coffee grounds are dried separately and then supplied to a roasting system through the burner dedicated to coffee grounds. [Diagram 3] This is a diagram showing how, in the coffee grounds treatment process of the present invention, the coffee grounds are dried separately, then supplied to a line for pulverized coal that has been dried and crushed in a coal dryer, and then supplied together with the pulverized coal to the firing system through a pulverized coal burner. [Figure 4] In the coffee grounds treatment process of the present invention, the coffee grounds are dried separately, then mixed with crushed waste plastics, and supplied together with the waste plastics through a waste plastic burner to the firing system. [Diagram 5] In the coffee grounds treatment process of the present invention, the coffee grounds before drying are mixed with coal, and the mixture is dried and crushed in a coal dryer, and then supplied to the firing system through a pulverized coal burner. [Figure 6] In the coffee grounds treatment process of the present invention, the coffee grounds before drying are mixed with crushed waste plastic, the coffee grounds are dried in the pneumatic transport line by the air flow for pneumatic transport, and are supplied to the firing system together with the waste plastic through a waste plastic burner. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In the present invention, dried coffee grounds are fed to a calcination system through a burner and serve as part of the fuel for cement clinker production.

[0013] [Cement clinker manufacturing facility] The cement clinker production facility used in the present invention is one that has been conventionally used in cement clinker production, and has, for example, the structure shown in FIG.

[0014] The cement clinker production facility 1 includes a rotary kiln 3, a preheater 5, a calciner 4, and a cooler 7, and is generally called a firing system.

[0015] The preheater 5 consists of multiple cyclones. The raw materials are supplied to the cyclones at the top of the preheater 5, where they are preheated by heat exchange with the high-temperature exhaust gas from the rotary kiln 3. In the rotary kiln 3, the raw materials are burned at high temperatures while rotating using burners 9b or 9c located in front of the kiln. In the rotary kiln 3, the side connected to the preheater 5 is called the kiln end, and the side connected to the cooler 7 is called the kiln front. The cooler 7 is used to cool the high-temperature burnt material (clinker) discharged from the kiln front.

[0016] In the present invention, the above-mentioned coffee grounds are supplied to the burning system through a burner using the cement clinker production equipment having the above-mentioned structure, and a representative example of the process is shown in Figures 2 to 6. That is, in the cement clinker production equipment, the coffee grounds are supplied to the burning system through a burner, either alone or mixed with pulverized coal or waste plastics.

[0017] [Coffee grounds] Coffee grounds are the residues left over from hot water extraction of roasted coffee beans. Coffee grounds are discarded while still wet, and generally contain a very large amount of water, with a moisture content of 65 wt% or more, and are known to be unsuitable for incineration. In addition, the particle size of the coffee grounds used in the present invention is preferably 3 mm or less in terms of ease of handling and combustibility. Coffee grounds usually have a uniform particle size of 3 mm or less, and can be used as is after drying without the need for grinding.

[0018] The calorific value of the coffee grounds used in the present invention is close to that of coal (about 6500 cal / g) and waste plastic (about 2000 to 10000 cal / g), and therefore can be used as a substitute for coal, etc. Specifically, the calorific value of the coffee grounds is preferably 5000 to 5500 cal / g. Coffee grounds usually have a calorific value of 5000 to 5500 cal / g, and can be used as is after drying.

[0019] Coffee grounds contain water when discarded, and must be dried before use as fuel. Because coffee grounds pose a risk of catching fire when heated above 250°C, the drying temperature for the coffee grounds of the present invention is preferably 250°C or lower. Furthermore, the drying temperature is more preferably 190 to 210°C. Although it depends on the grain size of the coffee grounds (grind size of the coffee beans), it is preferable to dry the coffee grounds so that the moisture content is 5 wt% or less, and more preferably 3 wt% or less. Note that this moisture content is the value at the time the burner is installed.

[0020] The coffee grounds may be supplied to the baking system through a burner alone, or may be supplied to the baking system through a burner together with pulverized coal or waste plastics, which will be described later. If coffee grounds contain moisture, problems such as adhesion to equipment and piping can occur. Coffee grounds are usually uniform in particle size, less than 3 mm, so this problem can be solved by simply drying them, and handling is greatly improved. Furthermore, because coffee grounds have a high calorific value, they can be supplied to the roasting system by themselves through the coffee grounds burner 9a.

[0021] [Pulverized coal] Pulverized coal is made by drying and pulverizing coal with a coal dryer to reduce the particle size. Dried coffee grounds can be supplied to the firing system through burner 9b together with the pulverized coal. Coal is usually stored in a wet state to prevent spontaneous combustion, and is dried before use as fuel. In addition, from the viewpoint of combustion efficiency and transportation efficiency, the coal is pulverized and sent to burner 9b so that it becomes pulverized coal when it is burned.

[0022] [Waste plastic] The waste plastics consist of, for example, used plastic packaging materials, PET bottles, and sheets. Dried coffee grounds can be fed to the firing system through a burner together with the waste plastics. When the waste plastics are brought into the factory, they are in various states, such as balers, rolls, bulk, and ASR (Automobile Shredder Residue). A baler is a block of multiple pieces of waste plastic compressed together. A roll is a rolled up sheet of waste plastic. Bulk is waste plastic that has not been compressed or otherwise processed, and each piece of waste is in a loose state. ASR is the residue that remains after shredding end-of-life automobiles.

[0023] The waste plastic is crushed to a specified size by a primary crusher and a secondary crusher. First, the waste plastic is put into the hopper of the primary crusher. Inside the primary crusher, a two-shaft rotary blade is attached, and the plastic is crushed to a size of about 200 mm. The waste plastics crushed by the primary crusher are fed into the hopper of the secondary crusher. The secondary crusher is equipped with a rotary blade, a fixed blade, and a pusher, and the waste plastics in the hopper are pushed by the pusher and crushed by being compressed between the rotary blade and the fixed blade. This crushing by compression is repeated until the particle size of the waste plastics becomes 30 mm or less. The waste plastics processed in this way are discharged from the secondary crusher into the air conveying line described later.

[0024] The process of supplying coffee grounds to the roasting system through a burner will be described below, although the present invention is not limited to these embodiments.

[0025] [burner] In the present invention, the burners for blowing the dried coffee grounds into the roasting system can be a burner 9a dedicated to coffee grounds, a pulverized coal burner 9b, or a waste plastic burner 9c. When the coffee grounds are supplied to the roasting system by themselves through a burner, the burner 9a dedicated to coffee grounds is used. When the coffee grounds are supplied to the roasting system together with pulverized coal through a burner, the pulverized coal burner 9b is used, and when the coffee grounds are supplied to the roasting system together with waste plastic through a burner, the waste plastic burner 9c is used.

[0026] The coffee grounds burner 9a, the pulverized coal burner 9b, and the waste plastic burner 9c are installed in front of the rotary kiln 3 and in the calciner 4. Furthermore, they may be installed in each cyclone constituting the preheater 5 above the calciner 4. At each of the above locations, a coffee grounds burner 9a, a pulverized coal burner 9b, or a waste plastic burner 9c can be installed. Also, multiple burners of the same type may be installed at the same location, or there may be locations where no burners are installed.

[0027] [Drying equipment and drying heat source] Coffee grounds contain water when discarded, and therefore need to be dried before combustion if they are to be used as fuel. Methods for drying coffee grounds are described below, but these drying methods may be carried out alone or in combination.

[0028] (When drying coffee grounds alone) The coffee grounds can be dried by a coffee grounds dryer alone. As the coffee grounds dryer, a cylindrical dryer, a fluidized bed dryer, a vibration dryer, or the like, which are generally used in factories, can be used. As the heat source for this coffee grounds dryer, it is preferable to use the exhaust gas 11 from the cooler 7. Also, the exhaust gas from the top of the preheater 5 may be used, or an independent heat source other than the heat generated from the roasting system may be used for drying. When using the exhaust gas from cooler 7, the exhaust gas may be directly brought into contact with the coffee grounds inside the dryer, or the exhaust gas and the coffee grounds may be isolated by a wall or the like and heat may be continuously exchanged through the wall or the like to indirectly dry the coffee grounds.

[0029] When drying is performed using exhaust gas from the cooler 7 or exhaust gas from the top of the preheater 5, it is preferable to dry the coffee grounds near the cement clinker production equipment so that the temperature of the exhaust gas does not drop significantly, but this is not necessary when an independent heat source is used. For example, the coffee grounds may be dried in advance at the coffee manufacturer and then transported to the cement plant. In this case, the total weight of the coffee grounds is lighter because the moisture has evaporated, which has the advantage of reducing transportation costs. When using coffee grounds that have been dried in advance at the coffee manufacturer, the drying step of the present invention is deemed to have been carried out. When this drying method is adopted, the dried coffee grounds can be blown in separately from the coffee grounds burner 9a, or can be mixed with waste plastics or pulverized coal and fed into the firing system through the waste plastic burner 9c or pulverized coal burner 9b. When mixed with waste plastics or pulverized coal, the dried coffee grounds can be added at an appropriate point in the transport line.

[0030] When fuel such as pulverized coal or waste plastic is injected into the burner, a constant injection amount is generally provided in the fuel flow path a little before the burner, consisting of a temporary storage tank and a constant injection feeder (not shown). When dried coffee grounds are mixed with pulverized coal or waste plastic, it is preferable to add the coffee grounds upstream of the constant injection feeder. A constant injection feeder is also provided when using a burner 9a dedicated to coffee grounds.

[0031] (When drying coffee grounds with a charcoal dryer) Coal stored in a wet state is dried and pulverized in a coal dryer to produce fine coal with small particle size. Coffee grounds before drying are put into the coal dryer together with coal, and dried and pulverized to obtain a mixture of dried fine coal and coffee grounds. As the coal dryer, a cylindrical dryer, a fluidized bed dryer, a vibrating dryer, etc., which are generally used in factories, can be used, and the coal dryer can perform drying and pulverization at the same time. The heat source for the coal dryer is usually exhaust gas from the cooler 7, but if necessary, exhaust gas from the top of the preheater 5 can be used, or an independent heat source other than the heat generated by the firing system can be used for drying. Even in this state of a mixture of coffee grounds and coal, the coffee grounds have a uniform particle size, so there is no need to grind them, and they are supplied to the coal dryer only for drying. When this drying method is adopted, the dried coffee grounds are mixed with pulverized coal and fed into the burning system through the pulverized coal burner 9b.

[0032] (When drying coffee grounds in a fuel air transport line) Fuels such as pulverized coal and crushed waste plastics as mentioned above are often air-transported to the burner (usually via a constant-volume feeder on the way). During air-transport, a large amount of air flows at a fairly high speed, and this airflow can be used to dry the coffee grounds. In particular, the piping (air-transport line) that transports the crushed waste plastics to the burner has a long flow path, making it more suitable for drying.

[0033] For example, waste plastic discharged from the secondary crusher is pneumatically transported to the waste plastic burner 9c through a pneumatic transport line. Although not shown, a fixed-volume supply device is provided near the waste plastic burner 9c. In the pneumatic transport line for waste plastic, a large amount of air (atmosphere) at about room temperature is pressurized by a compressor or the like and flows through the piping to transport the crushed waste plastic from the secondary crusher to the temporary storage tank. In the case where the pneumatic transport line is a long distance, such as several hundred meters, if the undried coffee grounds are supplied to a position upstream of this pneumatic transport line, the coffee grounds are air-dried during transport by the large amount of air flowing through the piping. This embodiment has the advantage that the pre-drying process of the coffee grounds can be omitted. When this drying method is adopted, the dried coffee grounds are mixed with waste plastic (or pulverized coal) and fed into the firing system through the waste plastic burner 9c (or pulverized coal burner 9b).

[0034] [Exhaust gas after drying] When exhaust gas 11 from cooler 7 is used as the drying heat source for the coffee grounds dryer, it is preferable to return the exhaust gas used for drying to the exhaust gas line (extraction line) that supplies the exhaust gas from cooler 7 to calciner 4. In other words, even after the coffee grounds are dried, if there is residual heat, this heat can be utilized even more effectively. Note that exhaust gas 11 from cooler 7 is usually sent to rotary kiln 3 or preheater 5 so that it is effectively utilized as a fuel supporting gas (oxygen source) in addition to utilizing heat, but since it still has the above-mentioned residual heat even after being used to dry the coffee grounds and oxygen has not been consumed, it can be utilized effectively in the same way. Furthermore, when exhaust gas from the cooler 7 is used as a heat source for drying a mixture of coffee grounds and coal in a coal dryer, the exhaust gas can be effectively utilized as heat or as a supporting gas for combustion by treating it in the same manner.

[0035] In a coffee grounds dryer, when the exhaust gas is directly contacted with the coffee grounds to dry them, the gas after use may have a coffee aroma. If this gas with a coffee aroma were to be discharged as is, it could cause pollution such as a bad odor. Therefore, by returning the exhaust gas to the extraction line, the aroma components in the exhaust gas are exposed to combustion, and the aroma components can be eliminated. In order to reliably obtain such an effect, the exhaust gas after being used for drying may be led into the inside of the rotary kiln 3.

[0036] When the exhaust gas from the top of the preheater 5 is used as the drying heat source, the exhaust gas can be sent to a dryer for cement raw materials, coal, etc., and used again for drying. Since the exhaust gas contains a large amount of fine powder, it is removed using an electric dust collector, a bag filter, etc., and then released into the atmosphere from a chimney.

[0037] The present invention can be carried out by appropriately combining the above-mentioned coffee grounds drying method, the burner used for blowing and its position, etc., but particularly preferred embodiments are shown in Figures 2 to 6. The present invention is not limited to these embodiments.

[0038] In the embodiment shown in Fig. 2, a coffee grounds dedicated burner 9a, a pulverized coal burner 9b, and a waste plastic burner 9c are provided in front of the rotary kiln 3, and the coffee grounds dedicated burner 9a and pulverized coal burner 9b are provided in the calciner 4. In the embodiment shown in Fig. 2, a coffee grounds dryer is used to dry the coffee grounds alone, and then the coffee grounds are supplied to the firing system through the coffee grounds dedicated burner. The heat source for drying is exhaust gas 11 from the cooler 7, and the gas used for drying is returned to the exhaust gas line (extraction line) that supplies the exhaust gas from the cooler 7 to the calciner 4.

[0039] In the embodiment shown in Fig. 3, a pulverized coal burner 9b and a waste plastic burner 9c are provided in front of the rotary kiln 3, and a pulverized coal burner 9b is provided in the calciner 4. In the embodiment shown in Fig. 3, the coffee grounds are dried separately in a coffee grounds dryer, and the dried coffee grounds are supplied to a line for pulverized coal after being dried and pulverized in a coal dryer, and are supplied together with the pulverized coal to the firing system through the pulverized coal burner 9b in front of the rotary kiln 3 and in the calciner 4. The heat source for drying is exhaust gas 11 from the cooler 7, and the gas used for drying is returned to the line for exhaust gas supplied from the cooler 7 to the calciner 4.

[0040] In the embodiment shown in Fig. 4, a pulverized coal burner 9b and a waste plastic burner 9c are provided in front of the rotary kiln 3, and the calciner 4 is also provided with a pulverized coal burner 9b and a waste plastic burner 9c. In the embodiment shown in Fig. 4, the coffee grounds are dried separately in a coffee grounds dryer, and then the dried coffee grounds are supplied to a pneumatic conveying line for crushed waste plastics, and then supplied together with the waste plastics to the firing system through the front of the rotary kiln 3 and the waste plastic burner 9c of the calciner 4. The heat source for drying is exhaust gas 11 from the cooler 7, and the gas used for drying is returned to the exhaust gas line that supplies the gas from the cooler 7 to the calciner 4.

[0041] In the embodiment shown in Fig. 5, a pulverized coal burner 9b and a waste plastic burner 9c are provided in front of the rotary kiln 3, and a pulverized coal burner 9b is provided in the calciner 4. In the embodiment shown in Fig. 5, coffee grounds before drying are fed into a coal dryer together with coal, and dried and pulverized to obtain a mixture of dried pulverized coal and coffee grounds, which is then supplied to the firing system through the pulverized coal burners 9b in front of the rotary kiln and in the calciner. Although not shown, the heat source for drying is exhaust gas from the cooler 7, and the gas used for drying is returned to the exhaust gas line that supplies the gas from the cooler 7 to the calciner 4.

[0042] In the embodiment shown in Fig. 6, a pulverized coal burner 9b and a waste plastic burner 9c are provided in front of the rotary kiln 3, and a pulverized coal burner 9b and a waste plastic burner 9c are also provided in the calciner 4. In the embodiment shown in Fig. 6, undried coffee grounds are directly supplied to the pneumatic conveying line for the waste plastic, dried in the pneumatic conveying line by the air flow for pneumatic conveying, and supplied to the firing system together with the waste plastic through the waste plastic burner 9c.

[0043] The burners shown in the calciners in Figs. 1 to 6 represent a plurality of burners arranged in a circular shape. [Industrial Applicability]

[0044] The coffee grounds processing method of the present invention is extremely useful from the perspective of resource and energy conservation, has little impact on cement production, and can be processed by utilizing the heat value of the coffee grounds. In addition, by using coffee grounds as fuel, the amount of coal used can be reduced, and a processing method with improved handleability can be provided. [Explanation of symbols]

[0045] 1: Cement clinker manufacturing facility 11: Exhaust gas flow 4: Calcination furnace 5: Preheater 3: Rotary kiln 7. Cooler 9a: Coffee grounds burner 9b: Pulverized coal burner 9c: Waste plastic burner 13: Bleed line

Claims

1. A method for treating coffee grounds, comprising the steps of: supplying coffee grounds to a burning system of a cement clinker production facility and burning the coffee grounds; After drying the coffee grounds, the coffee grounds are fed to the roasting system through a burner; A method for treating coffee grounds, characterized in that the exhaust gas used in the drying is returned to the extraction line.

2. 2. The method of claim 1, wherein the coffee grounds are fed to the firing system through the burner in a mixture with pulverized coal.

3. A method for treating coffee grounds, comprising supplying the coffee grounds to a burning system of a cement clinker production facility and burning the coffee grounds, After drying the coffee grounds, the coffee grounds are mixed with waste plastic and fed to the firing system through a burner; A method for treating coffee grounds, characterized in that the coffee grounds, etc. are dried by an air current for pneumatic transport in a pneumatic transport line for transporting the waste plastic to the burner.

4. 4. The method according to claim 1, wherein the coffee grounds or the like are dried using a gas discharged from the cement clinker production facility, and the temperature during the drying is 250° C. or lower.

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