JPH0662296B2 - Reclaimed metal oxide treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention efficiently recovers metal oxides such as iron oxide, iron ore, alumina, and bauxite in an alkali recovery plant that performs causticization directly in a fluidized bed furnace. In addition, the present invention relates to a method for treating recycled metal oxides which is effectively and circulated for reaction and operation.

[Conventional technology]

A conventional technique will be described by way of example for soda pulp production. As shown in FIG. 3, the pulp raw material chips supplied to the cooking facility 1 are 200 to 300 which are cooking chemicals.
It is mixed and heated with an aqueous solution (referred to as white liquor) of caustic soda and sodium carbonate (converted to Na ₂ O) and a self-circulating waste liquid to be cooked and separated into pulp and cooking waste liquid. The cooking waste liquor is a dilute waste liquor containing about 15 to 20% solid content (organic content such as lignin, inorganic matter such as NaOH and Na ₂ CO ₃ ) and is stored in the dilute waste solution storage tank 2. Next, the diluted waste liquid is guided to the evaporator 3.

The evaporating can 3 is a 5-6 heavy-effect can, with 6 in the final stage.
Waste liquid with a concentration of 0 to 70%. This is supplied to the fluidized bed recovery boiler 4, and is put into the fluidized bed together with iron oxide. In the fluidized bed, organic components such as lignin are burned into high temperature gas, and heat is recovered as steam in the boiler. On the other hand, the ash containing Na compound as a main component reacts with Fe ₂ O ₃ to generate sodium ferrate (Na ₂ Fe ₂ O ₄ ). This combustion reaction zone also needs to function as a fluid medium for Fe ₂ O ₃ to form a fluidized bed. In this case, a particle size and particle size distribution suitable for flow are required. When iron ore is used in it, the particle size is 0.2-2.0 mm, and when powdered iron oxide is granulated, a particle size of 0.2-5.0 mm is suitable. Due to the combustion of organic substances, the reaction of forming inorganic substances such as sodium ferrate, the fluidized medium becomes powdered sodium ferrate in which 20 to 40% is powdered,
It is discharged from the fluidized bed together with combustion gas. This is collected by a dust collector or the like. The granular sodium ferrate remaining in the fluidized bed without being pulverized is directly taken out from the fluidized bed.

The recovered sodium ferrate is guided to the extraction device 5 that regenerates the white liquor. Here, the white liquor and the extraction residue are separated. Since a large amount of white liquor is mixed with the regenerated iron oxide in the extraction residue,
This is led to the continuous washing and dehydrating device 6. This washing and dewatering is repeated several times, but as shown in the figure, it is desirable that the washing liquid and the extraction residue be in counterflow. The filtrate obtained at any stage is called weak liquid and contains components such as NaOH and Na ₂ CO ₃ . The regenerated iron oxide that has been washed and dehydrated in the final stage is introduced into the drying device 7 as a cake containing 20 to 35% of water and heated and dried. If the water content is high, an incomplete dried product in the form of dumplings is likely to be formed, and therefore in order to pulverize and dry it again, it is necessary to circulate the dried product in the drying device (not shown). Drying is performed up to about 5% water, and the regenerated iron oxide powder and the regenerated iron oxide powder are classified by the classifier 8. Since these regenerated iron oxides do not contain a binder, when they are dried, they almost have the original particle diameter, that is, the same as a state in which they are separated into a granular material and a powdery material in a fluidized bed recovery boiler. The granular regenerated iron oxide is directly returned to the granular moving bed recovery boiler 4.

The regenerated iron oxide powder is granulated by the granulating device 9. In this case, the concentrated waste liquid obtained from the evaporator 3 is generally added as a binder in several%.

[Problems to be Solved by the Invention]

However, the above conventional method has the following problems.

(1) The regenerated iron oxide after hydrolysis is washed with a washing and dewatering device such as a belt filter, but in order to keep the concentration of white liquor high, there is a limit to the amount of washing water, and the washing is insufficient, so that the cake There is a large amount of residual Na component in it, which is returned to the fluidized bed recovery boiler as it is, resulting in poor efficiency.

(2) The waste liquid supplied as a binder in the granulation process is
In order to improve the diffusion of the binder during kneading, it is necessary to add 5 to 10% of a relatively thin waste liquid having a concentration of 50%.

(3) Powdered iron oxide that enters the granulation process must be dried to a surface water content of approximately 5% or less.

(4) Iron oxide that has just been washed with water will hardly undergo self-granulation even if it is dried and not put into the granulating device.

(5) With a belt filter alone, a large amount of water remains in the cake, which requires a large amount of heat for drying.
There is also a large amount of Na, which is the same as in item (1).

The present invention has been made in view of the above points, in an alkali recovery plant for directly causticizing with a fluidized bed furnace,
An object of the present invention is to provide a method for efficiently treating regenerated metal oxides such as iron oxide, iron ore, alumina and bauxite.

[Means and Actions for Solving Problems]

A method for treating a regenerated metal oxide according to the first invention of the present application is a waste liquid containing pulp, caprolactam (lactam of aminocaproic acid) waste liquid, waste liquid containing alkali metal such as organic soda, organic potassium, sodium carbonate or potassium carbonate. Is concentrated and burned in a fluidized bed furnace to directly recover caustic soda or caustic potash and the like, and metal oxides such as iron oxide, iron ore, alumina and bauxite are used as the fluidizing medium and reaction medium in the fluidized bed furnace. In the method of repeatedly using this metal oxide, by mixing the regenerated metal oxide after extracting caustic substances such as caustic soda or potassium hydroxide by hydrolysis with a dilute waste liquid having a concentration of 10 to 20%, After replacing the residual adhered water in the regenerated metal oxide with the waste liquid, and then dehydrating, then drying and partially self-granulating And classified to provide a particulate regeneration metal oxide to the fluidized bed furnace was granulated by the addition of concentrated waste liquid ungranulated powdery play metal oxides, it is characterized by feeding into the fluidized bed furnace.

The method for treating regenerated metal oxide according to the second invention of the present application is
Pulp waste liquor, caprolactam waste liquor, waste sugar condensate and other waste fluids containing alkali metals such as organic soda, organic potassium, sodium carbonate or potassium carbonate are concentrated and directly burned in a fluidized bed furnace to recover caustic soda or caustic potash. As the fluidized medium and reaction medium of the fluidized bed furnace, metal oxides such as iron oxide, iron ore, alumina and bauxite are used.
In the method of repeatedly using this metal oxide, granular metal oxides among regenerated metal oxides after extraction of caustic substances such as caustic soda or caustic potash by hydrolysis are supplied to a fluidized bed furnace to obtain powder metal oxides. , 10 to 20% of the unconcentrated dilute waste liquid was mixed to replace the water in the powdery metal oxide with the waste liquid, which was then dehydrated, then dried and partially self-granulated. After that, it is characterized in that the granular regenerated metal oxide is classified and supplied to the fluidized bed furnace, the concentrated waste liquid is added to the ungranulated powdery regenerated metal oxide to granulate, and then the granular regenerated metal oxide is supplied to the fluidized bed furnace.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. However, the names, formats, shapes, relative positions, etc. of the constituent devices described in this embodiment are not intended to limit the scope of the present invention to only those unless particularly specified. It is just an example of explanation.

Example 1 FIG. 1 shows a flow in Example 1. Number 1
Since the flow around the device shown in to 6 is the same as that in the case of FIG. 3 described above, the description thereof will be omitted.

In FIG. 1, the moisture from the continuous washing device 6 is 20 to 3
The regenerated iron oxide cake containing 0% is guided to the slurry forming device 10, where the diluted waste liquid is introduced from the dilute waste liquid storage tank 2 into the slurry forming device 10 so as to have a weight equivalent to or greater than the weight of the solid matter. The mixture is mixed so that it can be transferred by the slurry pump 11. During this mixing, most of the water or weak liquid component in the acidic iron oxide cake is replaced with the dilute black liquor to form a slurry. This slurry is pressure-fed to the press filtration dehydrator 12 by the slurry pump 11. Pressure is 3
~ 7 kg / cm ² g is desirable. In the squeeze filter dehydrator 12, the pressure of the pump, the squeezing force from the outside of the filter cloth, and if necessary, compressed air or steam is passed through to dehydrate (deliver). By using a press filter dehydrator having a good dehydration property such as a press filter, it is possible to enhance the dehydration property and reduce the load on the dryer.

By the above dehydration, the residual water content can be dehydrated to 15 to 18%.
By introducing a sufficiently large amount of dilute waste liquid into the slurry-forming device 10 with respect to the water content of the water-containing regenerated iron oxide cake, the liquid solid content in the liquid-containing regenerated iron oxide cake is made substantially equal to that of the waste liquid. . Therefore, the waste liquid solid content in this cake is about 2.0 to 3.5%, which means that the binder amount necessary for granulation is provided. The filtrate discharged from the compression filtration dehydrator 12 is the same as the dilute waste liquid and is returned to the dilute waste liquid storage tank 2. Therefore, the filtrate is effectively concentrated in the evaporator 3 or works effectively as a diluent in the digestion equipment 1.

The waste liquid regenerated iron oxide cake is sent to the drying device 7 and dried to the extent that it does not interfere with the subsequent classification step. In this case, the surface water content may be 5% or less. Screen with a classifier 8 of 0.5 mm and 5 mm mesh screen to 0.5
What has fallen through mm is made into a predetermined particle size by the granulating device 9,
It is supplied to the fluidized bed recovery boiler 4. The binder need only contain a few percent of the concentrated waste liquid obtained from the evaporator. In the classifying device 8, granules having a particle size exceeding a predetermined size are crushed by a crusher (not shown) attached to the classifying device 8 or the drying device 7.

Embodiment 2 FIG. 2 shows a flow in Embodiment 2. The cooking equipment 1, the dilute waste liquid storage tank 2, the evaporator 3, and the fluidized bed recovery boiler 4 are the same as in the first embodiment. After the fluidized bed recovery boiler 4, powdered sodium ferrate (40 to 20% by weight, most of which has a particle size of 200 μm or less) and granular sodium ferrate (60 to 8) are used.
At 0% by weight, most of the particles have a particle size of 200 μm or more) and the particle size is separated into two types. The particle diameters of these particles hardly change even after the extraction step and the dehydration step. Therefore, the granular regenerated iron oxide obtained from the granular material can be returned to the fluidized bed recovery boiler 4 with the same particle size. Moreover, this granular regenerated iron oxide has good washing and dewatering properties, and even with a continuous washing and dewatering device such as a simple belt filter,
About 8 to 22% of dehydrated cake is obtained. This can be easily dried, and in some cases, can be returned to the fluidized bed recovery boiler 4 as a cake by the bypass line 13 shown by a broken line. The particulate matter discharged from the boiler 4 can be returned to the fluidized bed recovery boiler 4 through the granular sodium ferrate extractor 5a, the granular reclaimed iron oxide continuous washing and dehydration apparatus 6a and the granular regenerated iron oxide dryer 7a. it can.

On the other hand, if the particle size of the regenerated iron oxide powder remains as it is, the performance of the fluidized bed recovery boiler 4 deteriorates, and the water content in the cake is 28
Since it becomes about 35%, it is necessary to return to the fluidized bed recovery boiler through the same steps as those shown in the first embodiment. That is, the powdery sodium ferrate extractor 5b, the powdery regenerated iron oxide continuous washing and dehydration device 6b, the slurrying device 10b, the slurry pump 11b, the squeezing filter dehydrator 12b, and the powdery regenerated iron oxide drying device 7b are dried. Self-granulating by the device 7b is selected by the classifying device 8b, and regenerated iron oxide having a predetermined particle size is returned to the fluidized bed recovery boiler 4. Only the powdered regenerated iron oxide is introduced to the granulating device 9b, the concentrated waste liquid is used as a binder for granulation, and then returned to the fluidized bed recovery boiler 4.

In the method according to the second embodiment, the processing amount of the subsequent process after passing through the continuous washing and dehydrating device is reduced, and the compression filtration dehydrator 1 is used.
Since the installed capacity after 2b is halved and the slurry is made with only fine powder, the compression filtration dehydrator 12b
Performance is improved, and operation and maintenance are very easy.
Due to the above-mentioned improvement in performance, a smaller capacity of the granulation equipment is sufficient. This can provide an excellent system that can greatly help save power. Whether to select the first embodiment or the second embodiment depends on the overall equipment scale. Note that the extraction device and the continuous washing / dehydration device surrounded by the one-dot chain line in FIG. 2 have two series of the granular material and the granular material, but this is such that the granular material and the granular material are treated separately. As long as it is equipped with the same equipment, white liquor and weak liquid may be treated with common equipment. Therefore, this part may have a mechanical structure in which the respective systems are integrated.

In the above examples, the case where iron oxide is used as the fluid medium and the reaction medium has been described, but metal oxides such as iron ore, alumina, and bauxite or those containing metal oxide as the main component can be used.

Further, instead of the pulp waste liquid, it is possible to use a caprolactam (lactam of aminocaproic acid) waste liquid, an organic waste liquid containing an alkaline earth metal such as waste sugar concentrate.

〔The invention's effect〕

Since the present invention is configured as described above, it has the following effects.

(1) The residual liquid in the cake discharged from the continuous washing and dehydrating device is completely replaced by the waste liquid by the slurry mixing of the waste liquid and the cake, and the water can be effectively separated and removed from the cake by squeezing filtration.

(2) By replacing the waste liquid with the residual water content in the cake, the water discharged as the filtrate is returned to the dilute waste liquid storage tank 2 side, and the water can be efficiently separated in the multiple-effect evaporator 3. Further, some of them can be used as a diluent for cooking.

(3) The waste liquid in the cake after filtration contributes to the granulation in the subsequent step, and since it is uniformly dispersed in the cake, a high-quality granulated product can be easily formed.

(4) The solid content of the waste liquid in the cake after filtration can be used as the fuel and the chemical raw material itself of the fluidized bed recovery boiler 4.

(5) Since it is squeezed and dehydrated in the filtration process, this squeezing
The waste liquid in the cake acts to granulate a part of the regenerated iron oxide, and when this is dried in the drying step, a granulated product having the optimum strength for the fluidized bed is formed. The granulated and dried product by classification can be directly supplied to the fluidized bed furnace. As a result, the equipment for the granulation process can be downsized and the granulation power can be saved.

(6) Although the dilute waste liquid is slightly more viscous than the water or the water in the cake, the dilute waste liquid retains the heat of cooking and actually has a temperature of 50 to 80 ° C. This works effectively in the case of squeezing and dehydrating by appropriately lowering the viscosity of the liquid. The temperature also contributes to the evaporation of residual water after dehydration.

(7) Moderate viscosity of dilute waste liquid and alkali components in dilute waste liquid,
The organic component has a property of being well compatible with the metal oxide and is well mixed in the slurry forming step. Therefore, the conveyance to the squeezing filtration dehydrator 12 becomes extremely good, and troubles such as clogging and abrasion of the conveyance pipe due to solid-liquid separation are eliminated.

(8) The properties described in the above item 7 are as follows in the press filter dehydrator.
The solid content is evenly distributed to the filter cloth, prevents the blow-through when compressing blows with steam, compressed air, etc., and effectively filters and dehydrates the steam, compressed air, etc. It significantly reduces consumption and contributes to effective filter dehydration.

(9) For washing the filter cloth (back washing) in the squeezing filtration dehydrator 12, the dilute waste liquid itself used for slurrying can be used. This allows the entire system according to the invention to be effectively squeezed and dehydrated without adding any excess water.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an example of an apparatus for carrying out the method for treating a regenerated metal oxide of the present invention, FIG. 2 is a flow sheet showing another example of an apparatus using the method of the present invention, and FIG. It is a flow sheet which shows an example of the apparatus which implements the processing method of the regenerated metal oxide in the conventional direct causticizing method of alkali pulp. 1 ... Cooking equipment, 2 ... Diluted liquid storage tank, 3 ... Evaporator, 4
...... Fluidized bed recovery boiler, 5, 5a, 5b …… Extractor,
6, 6a, 6b ... Continuous washing and dehydrating device, 7, 7a, 7b
... Drying device, 8, 8b ... Classifying device, 9, 9b ... Granulating device, 10, 10b ... Slurrying device, 11, 11
b …… Slurry pump, 12, 12b …… Squeeze filter dehydrator, 13 …… Bypass line

Claims (2)

[Claims] 1. A waste liquor containing an alkali metal such as pulp waste liquor, caprolactam waste liquor, waste sugar-tightened organic soda, organic potassium, sodium carbonate or potassium carbonate is concentrated and directly burned in a fluidized bed furnace to directly remove caustic soda or caustic potassium. A metal oxide such as iron oxide, iron ore, alumina, and bauxite is used as a fluid medium and a reaction medium of a fluidized bed furnace for recovering caustic substances, and in the method of repeatedly using this metal oxide, caustic soda or caustic potash is used. The regenerated metal oxide after extraction of the caustic substance by hydrolysis is
The residual adhering water content in the regenerated metal oxide is replaced with the waste liquid by mixing with the dilute waste liquid before concentration at a concentration of 10%, and then dehydration is performed, followed by drying and partial self-granulation, followed by classification. And then supplying the granular regenerated metal oxide to the fluidized bed furnace, adding the concentrated waste liquid to the ungranulated powdered regenerated metal oxide to granulate, and then supplying the regenerated metal oxide to the fluidized bed furnace. Processing method. 2. A waste liquid containing an alkali metal such as pulp waste liquid, caprolactam waste liquid, waste sugar-tightened organic soda, organic potassium, sodium carbonate or potassium carbonate is concentrated and directly burned in a fluidized bed furnace to directly remove caustic soda or caustic potassium. A metal oxide such as iron oxide, iron ore, alumina, and bauxite is used as a fluid medium and a reaction medium of a fluidized bed furnace for recovering caustic substances, and in the method of repeatedly using this metal oxide, caustic soda or caustic potash is used. Among the regenerated metal oxides after extraction of the caustic substance by hydrolysis, granular metal oxides are supplied to the fluidized bed furnace, and powdered metal oxides
By mixing with the undiluted dilute waste solution at a concentration of 20%,
Substituting the waste water with the water content in the powdery metal oxide, and then dehydrating, then after drying and partially self-granulating, classify and supply the granular regenerated metal oxide to the fluidized bed furnace,
A method for treating a regenerated metal oxide, which comprises adding a concentrated waste liquid to an ungranulated powdered regenerated metal oxide, granulating the mixture, and then supplying the mixture to a fluidized bed furnace.