JP5417925B2 - How to use biomass - Google Patents

Description

  The present invention relates to a biomass utilization method in which biomass charcoal produced by pyrolyzing biomass by dry distillation is used in an iron making process.

In recent years, reducing CO ₂ emissions is an urgent issue from the viewpoint of preventing global warming. As a method of reducing CO ₂ emissions, technological developments such as reducing the amount of input carbon, recovering output CO ₂ , and replacing conventional coal and oil with carbon-free carbon sources are being carried out. . Biomass is known as a carbon-free carbon source. Biomass includes timber waste generated by demolishing houses, wood-based waste generated by sawmills, pruning waste in forests, agricultural waste, and the like. As the processing and utilization methods, landfill, neglect, incineration, fuel, etc. are the main ones.

  On the other hand, in the steel industry, the ironmaking process is a process of reducing iron ore using coal as a reducing material. In the steelmaking process, heat necessary for scouring is supplied by coal or the like. Therefore, the use of carbon sources is essential in the steel industry. On the other hand, biomass consists of carbon, oxygen, and hydrogen, but it itself has a high water content and low waste heat (for example, moisture 15 mass%, calorific value 16.2 MJ / kg-dry basis) It is not advantageous in terms of efficiency. Therefore, there is a method in which biomass is subjected to dry distillation, treatment such as dehydration and decarboxylation is performed, moisture is removed, and the amount of heat generation is increased to be used in the iron making process. Dehydration and degassing (decarbonation, demethanization, tar generation, etc.) occur by dry distillation, and carbon content in biomass is generated as gas and tar content, so that the carbon content (biomass coal) remaining as a solid is small. In order to efficiently use the carbon content remaining as a solid after dry distillation as biomass coal as an alternative to coal in the iron making process, it is necessary to produce biomass coal in a high yield.

  As a method for dry distillation (or pyrolysis) of biomass, conventionally, various furnaces such as a batch system (for example, refer to Patent Documents 1 and 2), a rotary kiln system (for example, refer to Patent Document 3), a fluidized bed system, and the like are used. The method used is known.

  As a heating heat source, it is known that the generated gas and tar obtained by biomass dry distillation are combusted and the combustion heat is used as the heat source. As a heating method, biomass is heated directly with a high-temperature gas such as the combustion gas (hot air circulation type), indirectly heated from the furnace such as a rotary kiln (external heating type), or gas generated inside the furnace. There is a system (internal heat type) that burns and directly heats the gas.

  In the batch method described in Patent Document 1, wood is filled in a furnace body of a box-shaped furnace, and generated gas is separately burned by a combustion apparatus and supplied to the box-shaped furnace. The temperature of the whole wood is raised to 700 ° C. or higher to promote carbonization. In Patent Document 2, a batch-type furnace includes a box-shaped furnace main body having a raw material supply port and a charcoal discharge port, and a carbonization chamber installed in the main body, and wood is filled in the carbonization chamber. Air is blown into the upper space of the furnace body, the combustible gas generated by the dry distillation of wood is combusted, the combustion gas flows between the furnace body and the carbonization chamber, and the wood in the carbonization chamber is 400-800 ° C. through the bricks of the carbonization chamber. Is carbonized.

  In Patent Document 3, which is a rotary kiln system, wood is heated at 300 to 1000 ° C. and an oxygen concentration of 10% or less with a rotary kiln or rotary dryer, and the gas generated by the heating is burned in a combustion furnace connected to the rotary kiln or the rotary dryer. Let In addition, the gas blowing port of the combustion furnace is installed at a position higher than the gas discharge port of the rotary kiln or rotary dryer, the gas generated by heating is burned at 800 to 1000 ° C., and the body portions at both ends of the rotary kiln or rotary dryer It is described that a cover for preventing inflow of intake air is installed in the gap of the mantle part, and the heated material outlet of the rotary kiln or rotary dryer has a double damper structure.

  Patent Document 4 discloses the following technique. By heating the ore containing crystal water (bonded water) and dehydrating the crystal water as water vapor, a porous ore in which the ore is made porous is generated. Next, the porous ore is brought into contact with a dry distillation gas (organic gas) obtained by dry distillation of an organic material such as wood or an organic liquid such as coal tar. Organic compounds such as tar contained in dry distillation gas or organic liquid adhere to the surface of the porous ore. Next, the porous ore to which the organic compound is adhered is heated to 500 ° C. or more, and an ore in which a part of the oxide of an element such as iron contained is reduced by carbon in the organic compound is generated. It is said that the porous ore to which the reduced ore or the organic compound adheres can more easily reduce oxides of elements such as iron in the refining of iron making or steel making.

Japanese Patent Laid-Open No. 03-122191 JP 2007-146016 A JP 2002-241762 A JP 2008-95175 A

  The conventional techniques described in the above Patent Documents 1 to 3 have the following problems (a) to (d).

  (A) Both the batch method and the rotary kiln method are methods for carbonizing biomass only by controlling the heating temperature, atmospheric conditions, and the like. The yield of carbonized biomass (biomass charcoal) is about 25 mass% in the batch system and about 20 mass% in the rotary kiln system, and it is difficult to improve the yield of biomass charcoal more than that.

  (B) When the generated gas and tar are combusted and used as a heat source for biomass dry distillation, the gas and tar cannot be recovered as biomass charcoal. It is desirable to actively convert the generated tar into biomass coal.

  (C) In the batch systems of Patent Documents 1 and 2, since it is not a continuous process, carbonization requires 5 hours or more, which is not economical.

  (D) In the biomass dry distillation product, pyroligneous acid and heavy hydrocarbon (tar) components are also generated in addition to the light gas, and management of the air ratio, temperature, etc. is necessary to completely burn the tar components. Further, in order to use the dry distillation product separately without performing the combustion treatment, an exhaust gas treatment such as tar removal is required.

On the other hand, in the iron and steel industry, high-grade hematite ore with a high iron content is used as a raw material for iron making, but the amount of its resources is decreasing, and therefore, low-grade iron ore with abundant resources. It is an urgent task to find an efficient usage method. Low grade iron ore has a high gangue component such as Al ₂ O _{3 and a} large amount of water of crystallization, so when used in a blast furnace, it increases the use of reducing materials such as coke and pulverized coal, It becomes a factor which obstructs air permeability. Further, when used as a sintering raw material in a sintering machine, quality such as strength of sintered ore is lowered. Therefore, it is necessary to increase the coagulant such as coke. Therefore, by pre-processing such low-grade iron ore, if the water of crystallization is removed and even a portion of the iron oxide can be reduced, it is possible to reduce the reducing material ratio when used in a blast furnace. Conceivable.

  However, the technique described in Patent Document 4 that removes crystal water by heating and reduces part of the ore has the following problems (e) to (h).

  (E) When obtaining a porous ore from an ore having bound water, a separate heat treatment is required.

  (F) Since the method in which the biomass carbonization and the organic liquid or organic gas containing the organic compound to the iron ore are contacted is performed separately or in a series of steps (series), separate devices are required and heat loss Etc. are concerned, and external heat supply is required.

  (G) Further, the carbonization of the biomass carbonization and the porous ore is carried out in separate apparatuses, that is, the efficiency of the carbon deposition is low because the biomass carbonization product (tar, gas) and the porous ore are not close to each other. bad.

  (H) It is conceivable to use a method in which biomass and iron ore are mixed, filled, and dry-distilled in advance in a vertical furnace in order to carry out with one apparatus, but physical properties such as the density of biomass and iron ore. Therefore, it is difficult to segregate at the time of charging and to mix biomass and iron ore uniformly.

  As described above, it is difficult for the conventional technology to positively improve the yield of biomass charcoal, and iron ore is efficiently produced using an organic liquid or organic gas containing an organic compound generated by dry distillation of biomass. It is also difficult to modify.

  Therefore, the object of the present invention is to solve such problems of the prior art and improve the yield of biomass coal when carbonizing biomass to produce biomass coal, and improve low-grade iron ore. It is to provide a method of using biomass that can be used in the steelmaking process.

The features of the present invention for solving such problems are as follows.
(1) A biomass utilization method using biomass charcoal produced by dry distillation of biomass in an iron making process, pulverizing biomass to obtain a pulverized biomass, and pulverizing iron-containing material to iron-containing material A step of obtaining a pulverized product, a step of mixing the biomass pulverized product and the pulverized iron-containing material to obtain a mixture, and dry-distilling the mixture to produce a mixture of biomass charcoal and a carbon-deposited iron-containing material. And using the mixed dry-distilled product in an iron making process.
(2) The method further comprises a step of classifying the mixed carbonized product into biomass charcoal and carbon precipitated iron-containing material, and the classified biomass charcoal and carbon precipitated iron-containing material are used in an iron making process. (1) The method for using biomass according to (1).
(3) The method for using biomass according to (2), wherein the classified carbon-deposited iron-containing material is molded and used in an iron making process.
(4) The method for using biomass according to any one of (1) to (3), wherein an average particle size ratio between the pulverized biomass and the pulverized iron-containing material is 3 or more.

  According to the present invention, it is possible to improve the yield of biomass coal produced by dry distillation of biomass. In addition, as for the iron-containing material, biomass-derived carbon adheres in the dry distillation furnace and a part of the iron content is reduced, so that the iron-containing material can be modified. As a result, even a low-grade iron-containing substance can be used efficiently in the iron making process, contributing to coal reduction and the like.

Explanatory drawing of one Embodiment of this invention. Schematic which shows one Embodiment of the rotary kiln used at a carbonization process. The graph which shows the thermal mass measurement result of the iron ore used in the Example. The graph which shows the relationship between the heat processing temperature and specific surface area of the iron ore used in the Example.

  In the present invention, the biomass and the iron-containing material are heat-treated at the same time, the biomass charcoal obtained by dry distillation is used as a reducing material in the iron making process, and the heat-treated iron-containing material is used as an iron source in the iron making process. Biomass and iron-containing material are heat-treated at the same time to produce biomass charcoal by dry distillation, and the dry distillation product (gas, tar) generated from biomass charcoal during dry distillation is brought into contact with the iron-containing material located nearby at high temperature The carbon in the dry distillation product derived from this is precipitated and part of the iron content is reduced, so that the iron-containing material can be efficiently reformed to a high-quality one.

  Biomass is a general term for a certain amount of accumulated animal and plant resources and wastes originating from them (excluding fossil resources). The biomass used in the present invention includes agricultural, forestry, livestock, and fisheries. Any biomass that is pyrolyzed to produce carbide, such as a system or a waste system, can be used. It is preferable to use biomass having a high effective calorific value, and it is preferable to use woody biomass. Woody biomass includes papermaking by-products such as pulp black liquor and chip dust, lumber by-products such as bark and sawdust, forest land remnants such as branches, leaves, treetops, and end mills, cedar, cypress, pine, etc. Forest products such as thinned timber, edible fungi from special forest products such as hodwood, firewood charcoal such as shii, konara, pine, forestry biomass such as willow, poplar, eucalyptus, pine, etc. General waste such as pruned branches of garden trees in private houses, pruned branches of country and prefectures, pruned branches of garden trees of companies, industrial waste such as construction and building waste, and the like. Agricultural biomass is classified as agricultural biomass, such as rice husk, wheat straw, rice straw, sugarcane cass, palm palm, etc., which originates from waste and by-products, and rice biomass, rapeseed, soybean, etc., which originates from energy crops. The part can also be suitably used as woody biomass.

  Biomass dry distillation is the thermal decomposition of biomass, which is heated by shutting off or restricting the supply of air (oxygen) to produce gas (also called wood gas), liquid (tar), or solid (charcoal) products. Is the technology to get A black-brown, highly viscous liquid material obtained by separating and removing a brown transparent liquid (vinegar liquid) by standing or distilling a liquid obtained by pyrolyzing biomass may be called tar. The liquid in which acetic acid is mixed is called tar.

The iron-containing material used in the present invention is preferably iron ore such as hematite, limonite, magnetite, siderite, sulphite, iron oxalate minerals, etc. Can be used in the present invention. Preferred has crystal water, expressing the increase in pore and specific surface area with the elimination of water of crystallization, a iron ore low grade, iron content specific surface area after heating is 10 m ² / g or more It is a contained material.

  An embodiment of the present invention will be described with reference to FIG. The biomass 1 and the iron-containing material 2 are crushed (pulverized) in the crushing steps 3 and 4 to a size that enters the mixing step 5, and mixed uniformly in the mixing step 5. The range of the mass mixing ratio of biomass / iron ore can be appropriately set whenever necessary. The more iron ore, the greater the apparent biomass coal yield. The mixed mixture of the biomass 1 and the iron-containing material 2 is supplied to the dry distillation step 6, heated in an inert atmosphere, and simultaneously heat-treated. At that time, the biomass 1 is subjected to dry distillation treatment, and biomass charcoal and dry distillation gas tar are generated. On the other hand, in the iron-containing material 2, the adsorbed water and the crystal water are dehydrated with heating, generating pores and increasing the specific surface area. A dry distillation gas or tar generated from biomass comes into contact with this iron-containing substance, and the dry distillation gas and tar adhere, and the carbon component is deposited. Part of the deposited carbon is donated to reduce the iron-containing material. The mixed charcoal, which is a mixture of biomass charcoal and carbon-deposited iron-containing material obtained in the carbonization process 6, is classified in the classification process 8 depending on the difference in specific gravity or particle size, and biomass charcoal 9 (carbide) and carbon-deposited iron-containing substance. 10 and separated. The biomass charcoal 9 is supplied to the iron making process by processing such as pulverization and granulation (not shown), and is used as a reducing material. On the other hand, the carbon-deposited iron-containing material 10 is used as it is or as necessary, after being formed in the forming step 11 and supplied to the iron making process.

  The biomass charcoal and the carbon-precipitated iron-containing substance can be used for the iron making process after being pulverized or molded as a mixed dry distillate without being classified.

In the present invention, the lower limit of the heating / drying temperature in the dry distillation step 6 is equal to or higher than the desorption temperature of crystallization water contained in the iron-containing substance (350 ° C or higher), and is equal to or higher than the temperature at which dry distillation gas tar is generated from biomass (400 ° C). Or more). Biomass dry distillation gas and tar contain biomass adhering moisture or moisture generated by decomposition. This moisture reacts with carbon and / or biomass coal deposited on the iron-containing material to produce CO and H ₂ . The present invention aims to improve the recovery rate of carbon contained in biomass, and the heating / drying temperature in the dry distillation step 6 is preferably a temperature at which the reaction occurs remarkably, and the upper limit is 800 ° C. It is preferable. More preferably, dry distillation is performed at 450 to 750 ° C. The end point of the dry distillation is preferably the time when the mass reduction of the biomass of the raw material has become sufficiently small. In practice, the residence time may be appropriately determined for each dry distillation temperature. For example, the necessary mass reduction does not proceed after 30 minutes at 400 ° C. In the dry distillation process 6, the mixture of the pulverized biomass and the pulverized iron-containing material is heated in an inert atmosphere to dry-distill the biomass. It is appropriate to call it a process.

  In the carbonization step 6, it is preferable to use an apparatus having a stirring and mixing function in the apparatus, and specifically, it is preferable to use a rotary furnace such as a rotary kiln system. In a rotary kiln, biomass and iron-containing materials can be mechanically mixed by rotation. Furthermore, when impurities that melt at a low temperature other than biomass are contained, for example, plastic is mixed in the biomass and melts in the rotary kiln and agglomerates or adheres to the inner wall of the kiln to generate a kiln ring. Although there is a possibility, agglomeration and adhesion can be prevented by mixing an iron-containing substance that does not melt within the dry distillation temperature range. On the other hand, when a vertical moving bed type furnace such as a fixed bed is used, biomass and iron-containing substances may be segregated during charging. When using a fluidized bed type furnace, the mixture of biomass and iron-containing material is fluidized and stirred by the gas supplied from the lower part of the apparatus, but the density difference between biomass and iron-containing material is different. There is a risk of segregation.

  The particle size after crushing of biomass and iron-containing materials in the crushing processes 3 and 4 is determined from the viewpoint of efficient tar and gas adhesion on the iron-containing materials and precipitation of carbon in the tar and gas. The average particle size ratio with the pulverized product (biomass pulverized product / iron-containing material pulverized product) is preferably 3 or more, more preferably 5 or more. The larger the particle size ratio, the better the contact with the iron-containing material on the biomass surface. In the classification step 8 after the carbonization step 6, classification is easier as the particle size ratio is larger. The particle diameter evaluation method may be determined as appropriate, but in the present invention, the particle diameter is 50%. This method is also recommended.

  The molding step 11 is usually used for rolling granulation performed on an inclined rotating dish, extrusion molding extruded from a cylindrical die, a compression molding machine of a briquetting roll for supplying powder to a mold on the surface of a rotating roll, and the like. What is necessary is just to perform using the molding machine which is.

  The generated gas 7 generated in the dry distillation process 6 is a gas after carbon content in the dry distillation gas and tar is deposited on the iron-containing material, and is obtained by removing heavy tar and being lightened. The generated gas 7 may be processed by a normal exhaust gas processing apparatus (for example, a combustion furnace), but can also be used as a heat source for the dry distillation process 6.

  The heat source of the dry distillation process 6 may be obtained by combustion of the generated gas 7 as described above, but fuel gas such as heavy oil or propane may be burned and used as a heating gas. Moreover, you may heat by electric heating other than the method of burning fuel gas. In the case of electric heating, it is possible to control the temperature by dividing the dry distillation step 6.

  The biomass charcoal 9 and the carbon-precipitated iron-containing material 10 recovered from the carbonization process 6 have a high processing temperature and are discharged at a high temperature, and therefore are cooled with an inert gas or the like in consideration of safety such as ignition. It is preferable. The temperature of the cooling gas may be about 200 ° C., more preferably 100 ° C. or less.

  Next, an embodiment of the present invention in the case where an external heating type rotary kiln furnace is used in the dry distillation process will be described with reference to FIG.

  In FIG. 2, the apparatus main body 21 of the rotary kiln furnace 20 includes an outer tube 22 and an inner tube 23. The inner tube 23 is arranged concentrically with the outer tube 22 in the inner longitudinal direction of the outer tube 22. The inside of the inner pipe 23 constitutes a passage 24 (treatment space) for biomass and iron-containing material, and the space between the outer pipe 22 and the inner pipe 23 constitutes a heating gas passage 25.

  When the mixture of biomass and iron-containing substance is dry-distilled using the apparatus of FIG. 2, the screw feeder for supplying the material from the one end side of the rotary kiln main body 21 is mixed with the biomass and iron-containing substance 18 crushed in advance. 29 to the processing space 24. The heated gas (hot air) 19 is supplied to the heated gas space 25 through the hot air conduit 31. 27 is a fixed supply device for the material to be processed, 28 and 30 are drive motors, 32 is a discharge port for the heated gas, and 26 is a discharge port for the processed material to be processed and the generated gas.

  The heated gas supplied to the heated gas passage 25 heats the entire inner tube 23, and the biomass and the iron-containing material are heated through the tube wall and dry-distilled. The heated gas flowing through the heated gas passage 25 is discharged from the discharge port 32 on the other end side of the apparatus main body 21.

  On the other hand, the biomass and the iron-containing material supplied to the processing space 24 inside the inner pipe 23 are heated while being transported through the processing space 24 while being mixed by the rotation of the inner pipe 23, and the adhering water and crystals of the iron-containing material are heated by this heating. Water and moisture contained in the biomass are desorbed, and the biomass is dry-distilled as it moves, becoming biomass charcoal and generating dry-distilled gas and tar. The generated dry distillation gas and tar come into contact with the adjacent iron-containing material, and hydrocarbon gas and tar are attached. Further, the adhering hydrocarbon-based gas / tar content undergoes a dehydrogenation reaction on the iron-containing material, and is deposited as carbon on the iron-containing material.

  Thus, the biomass charcoal and the carbon precipitated iron-containing material 33 that have been subjected to the heating and carbonization treatment in the carbonization process are discharged from the discharge port 26 of the apparatus main body 21, and the generated gas 34 from which heavy tar has been removed is also discharged. Is done.

  In the carbonization step, the rotary kiln shown in FIG. 2 was used to heat the biomass and the iron-containing material.

The rotary kiln configuration is
Inner tube: Inner diameter 150 mmφ × 1500 mmL,
Outer tube: inner diameter 450mmφ × 1200mmL,
Overall device tilt: 1 degree,
Kiln rotation speed: 2.0 rpm,
Heating method: three-part electric heating,
Met. Nitrogen was bubbled as a carrier gas as an internal standard for gas yield calculation (30 L / h).

  The composition of biomass (cedar waste wood) used in the test is shown in Table 1, and the composition of iron ore (iron ore A and iron ore B) used as the iron-containing substance is shown in Table 2. Iron ore A is a low-grade ore with a high water content, and iron ore B is a high-grade ore with a low water content.

  The thermal mass measurement result of the iron ore A used for the test is shown in FIG. According to FIG. 3, desorption of crystal water is confirmed at 350 ° C. FIG. 4 shows the relationship between the heat treatment temperature and specific surface area of the iron ore used in the test. It can be seen that the specific surface area of iron ore A increases by heating.

  [Invention Examples 1 to 4] In the same flow as shown in Fig. 1, biomass and iron ore A were dry-distilled and classified to produce biomass charcoal and carbon deposited iron ore.

  Pre-ground biomass and iron ore were mixed and used for testing. The residence time in the rotary kiln is about 56 minutes. The feed rate of the mass ratio 1 mixture of biomass and iron ore to the rotary kiln was 2.0 kg / h. The gas yield was calculated from the amount of nitrogen used as the carrier gas and the gas analysis result by gas chromatograph, and the tar yield and water yield were calculated from the mass recovered from the trap (ice-cooled) after the rotary kiln (not shown). The solid yield was the difference between the gas yield and the tar and water yield. In addition, regarding the amount of carbon deposited on the iron-containing material, the mixed dry distillate of the obtained biomass coal and carbon deposited iron ore was separated by specific gravity (in water), and the amount of carbon deposited on biomass coal and iron ore was analyzed. . Table 3 shows test conditions and analysis results together.

  [Invention Example 5] As Invention Example 5, iron ore B was used and tested in the same manner as in Invention Example 1. Table 3 shows test conditions and analysis results together.

  [Invention Example 6] As Invention Example 6, iron ore A was used and tested in the same manner as in Invention Examples 1 and 3 under the condition of a biomass / iron ore particle size ratio of 1.0. Table 3 shows test conditions and analysis results together.

  [Comparative Example 1] As Comparative Example 1, a test was conducted using only biomass without mixing iron ore. Table 3 shows test conditions and analysis results together.

  According to Table 3, it turns out that the yield of biomass charcoal improves by mixing with iron ore and carrying out dry distillation. Carbon deposits on iron ore, and low-grade iron ore A with a high water content has a larger specific surface area and larger pore volume than iron ore B. Therefore, it is better to use low-grade iron ore A. Compared with the case where high-grade iron ore B is used, the amount of deposited carbon is increased. The larger the biomass / iron ore particle size ratio, the greater the yield of biomass coal and the amount of carbon deposited. Further, as a result of analysis using GC-MS (a mass spectrometer directly connected to a gas chromatograph), the tar content was found to be lighter.

DESCRIPTION OF SYMBOLS 1 Biomass 2 Iron content substance 3 Crushing process 4 Crushing process 5 Mixing process 6 Dry distillation process 7 Generated gas 8 Classification process 9 Biomass charcoal (carbide)
DESCRIPTION OF SYMBOLS 10 Carbon precipitation iron-containing substance 11 Molding process 18 Biomass, iron-containing substance 19 Heating gas 20 Rotary kiln furnace 21 Rotary kiln main body 22 Outer pipe 23 Inner pipe 24 Processing space 25 Heating gas space 26 Outlet 27 Constant supply apparatus 28 Drive motor 29 Screw feeder Reference Signs List 30 Drive motor 31 Hot air conduit 32 Heated gas outlet 33 Biomass charcoal, carbon precipitated iron-containing material 34 Generated gas

Claims (3)

A method of using biomass, in which biomass charcoal produced by carbonizing biomass is used in an iron making process,
A step of pulverizing biomass to obtain a pulverized biomass,
Pulverizing the iron-containing material to obtain a pulverized iron-containing material;
Mixing the biomass pulverized product and the iron-containing material pulverized product to obtain a mixture;
Dry-distilling the mixture to obtain a mixed dry-distillate that is a mixture of biomass charcoal and a carbon-precipitated iron-containing material ;
Classifying the mixed dry distillate into biomass charcoal and carbon precipitated iron content-containing material ,
A method for using biomass, characterized in that the classified biomass charcoal and carbon-deposited iron-containing material are used in an iron making process. The method for using biomass according to claim 1 , wherein the classified carbon-deposited iron-containing material is molded and used in an iron making process. The method for using biomass according to claim 1 or 2, wherein an average particle size ratio between the pulverized biomass and the pulverized iron-containing material is 3 or more.

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