JPS62268882A - Treatment of iron acid soda - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a direct causticizing fluidized bed system in which caustic soda is recovered from pulp cooking waste liquor (also called black liquor) using iron oxide as a causticizing agent. The present invention relates to a method for efficiently circulating and treating sodium ferrate collected by a device.

[Conventional technology]

BACKGROUND ART Conventionally, the lime method has been put into practical use when recovering caustic soda from pulp cooking waste liquid (hereinafter referred to as valve waste liquid) generated when wood chips are digested. However, this lime method has drawbacks such as a complicated process, the production of waste, which requires measures against odor and drainage, and a poor causticization rate.

In order to eliminate these shortcomings, the
As shown in Publication No. 4, the alkaline waste liquid substantially free of sulfur compounds discharged from the process of cooking and bleaching cellulose materials is concentrated, then combusted with the addition of iron oxide, resulting in sodium ferrate ( A method has been proposed in which caustic soda is directly recovered as an extracted aqueous solution by pouring sodium ferrate) into water, and the iron oxide obtained as an extraction residue is recycled and reused. In this method, the generation of caustic soda from the alkaline wastewater is probably caused by the combustion of the wastewater, which decomposes the remaining organic matter contained in the wastewater, and the resulting products are soda carbonate and/or soda oxide, which are It is thought that sodium ferrate is produced by reacting with iron oxide as shown in equations +11 and (2), and by treating this in water, caustic soda and iron oxide are obtained as shown in equation (3).

NazCOi +F6!03 = NatFezOn
+COt [1) Na! 0+Fe2O, l-4Na
tFet04(2)NalFetOa + HzO=
2NaOH+ Petos [3] However, when applying the above method to a fluidized bed furnace, in the direct causticizing method, the basic principle is to recycle and reuse iron oxide (iron ore), and to remove carryover from dust collectors, etc. Replenish only (
The replenishment rate is on the order of a few percent at most), while granular iron ore, which is a causticizing reactant as well as a fluidized bed maintenance agent, becomes more powdered in the furnace as the number of recycled uses increases ( Approximately 10% of the iron ore is pulverized), and some pulverization is also seen during iron ore handling in the feeder, causticizing process, etc. Furthermore, since the fluidized bed method basically uses a granular causticizing agent, it is not possible to set the reaction molar ratio Fe/Na close to 1.0 (as shown in reaction formulas (1) and (2), On the other hand, powdered causticizing agents have the problem that they immediately jump out of the furnace, making it impossible to expect the reaction to proceed sufficiently.

In order to solve the above problems, the present inventors causticized powdered sodium ferrate collected in a fluidized bed boiler, cyclone, and electric industrial dust machine, and then dried the powdered iron oxide powder. Developed a technology to granulate part or all of it using black liquor as a binder and feed it again as granules to a fluidized bed furnace, and filed a patent application as Japanese Patent Application No. 58-'167927 (Japanese Unexamined Patent Publication No. 60-59190). are doing.

[Problem that the invention seeks to solve]

However, the above conventional method has the following problems.

+11 Cyclone collected material and industrial dust machine collected material have small particle sizes, easily absorb moisture as powder, and have poor handling properties such as a large angle of repose, leading to bridging and clogging in hoppers and piping. easy.

(2) Since the cyclone collection material and the electrical industry dust collection material are fine powders, it is difficult to efficiently perform caustic soda extraction in the causticizing process and dehydration in the drying process, which means that residual sodium and residual moisture are large. , the amount supplied to the fluidized bed furnace increases.

(3) The causticization rate of the cyclone collected material and the industrial dust machine collected material is low.

The present invention was made in view of the above points, and it facilitates handling by supplying the cyclone-collected material and/or the industrial dust machine-collected material to the granulation process as it is without causticizing it. The object of the present invention is to provide a method that can efficiently perform a causticizing step and a drying step and can improve the causticizing rate.

Means and operation for solving the problems c] The method for treating sodium ferrate of the present invention involves concentrating the valve waste liquid, adding iron oxide as a causticizing agent and a fluidized bed maintenance agent, and burning it in a fluidized bed furnace. Then, the product is poured into water to recover caustic soda and iron oxide, and after the fluidized bed furnace exhaust gas is heat recovered in a boiler, it is introduced into a dust collection device such as a cyclone or electric dust machine to collect it. In this method, the collected material from the dust collector downstream of the boiler is directly treated without being causticized.
It is characterized by being supplied to the granulation process.

A cyclone such as a multi-cyclone, an electric industrial dust machine, etc. are used as a dust collection device after the boiler, and the cyclone collected material, electric industrial dust machine collection material, or electric industrial dust machine ura collection material is granulated. Supply to Engineering 1j. In addition, granulation is
Compression granulation is preferred.

〔Example〕

Embodiments of the present invention will be described in detail below by way of example based on the drawings. However, unless there is a specific description, the arrangement of the component devices described in this embodiment is not limited thereto, and is merely an illustrative example.

The dilute black liquor is introduced into the thin film evaporator 1, evaporated and concentrated to make a 50-60% black liquor, and then introduced into the disk evaporator 2 to make a 70-80% 2474 liquid, and this concentrated black liquor is fluidized. It is supplied to the floor furnace 3. On the other hand, granular iron oxide is supplied to the fluidized bed furnace 3 from the granular iron ore storage tank 4 . The bed temperature of the fluidized bed furnace 3 is 700 to 1100°C, preferably 900 to 100°C.
The temperature is set to 0°C, and Fe/Na is set to be 1.0 or more.

a. Pure iron, iron ore (FeJi, Fe
1Oa), sintered ore, reduced pellets, granulated iron-based dust, and other granular iron-based granular compounds are used. In this example, iron ore is used as the iron oxide, and granular iron ore is used for replenishment. 5 is a fluidized bed, 6 is an air distribution plate,
7 is a wind box.

The ferric acid soda from the fluidized bed furnace 3 is introduced into the first causticizing device 8 and extracted and separated into a caustic soda aqueous solution and recovered iron oxide,
After drying the recovered iron oxide using combustion exhaust gas or the like in a first drying device 10, it is charged into an iron ore storage tank 4.

On the other hand, the powdered material collected in the boiler 11 is introduced into the second causticizing device 12 where it is extracted and separated into a caustic soda aqueous solution and recovered iron oxide. After drying, the iron ore is granulated in a granulator 16 using black liquor as a binder to form granular iron oxide, which is then charged into the iron ore storage tank 4.

The fine powder collected by the cyclone 14 and the electrostatic precipitator A15 is directly processed into the granulation device 16 without causticizing it.
Here, the iron ore is granulated using black liquor as a binder, and then put into an iron ore storage tank 4 as granular iron oxide for reuse.

Note that there are cases where only the finest electrostatic precipitator-collected material is sent as it is to the granulator 16 for granulation without being causticized. In this case, the cyclone catch is supplied to the second causticizing device 12.

FIG. 2 shows another example of an apparatus for carrying out the method of the present invention. In this example, dry iron oxide obtained in the first drying apparatus 10 is separated into granular iron oxide and powdered iron oxide in a classifier 17. The granular iron oxide is charged into a granular iron ore storage tank 4, and the powdered iron oxide is supplied to a granulator 16 for granulation. In addition, when mixing the cyclone collected material or the electrostatic precipitator collected material with the recycled iron oxide after drying, the sensible heat of the collected material can be used to prevent the regenerated iron oxide from reabsorbing moisture (regenerated iron oxide Although it depends on the storage period, it tends to re-absorb moisture during storage). Other configurations and operations are the same as those in FIG. 1.

〔Effect of the invention〕

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

(1) Since the cyclone collection material and/or the electrostatic precipitator collection material, which has a poor causticization rate, is granulated without being causticized and then burned and recycled, an increase in the causticization rate can be expected. , it is possible to improve the quality of recovered caustic soda.

(2) Efficient operation and operation of the causticizing process and drying process becomes possible (equipment such as a talarifier can be simplified).

(3) Handling of the generated powdered sodium ferrate becomes easier.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing an example of an apparatus for implementing the method of treating sodium ferrate of the present invention, and FIG. 2 is a flow sheet showing another example of an apparatus for implementing the method of the present invention.

Claims (1)

[Claims] 1 After concentrating the valve waste liquid, add iron oxide as a causticizing agent and fluidized bed maintenance agent and combust it in a fluidized bed furnace.Then, the product is poured into water to recover caustic soda and iron oxide, and the fluidized bed furnace exhaust gas is In a method in which heat is recovered in a boiler and then introduced into a dust collector such as a cyclone or an electrostatic precipitator to collect dust, the collected material from the dust collector downstream of the boiler is directly produced without being causticized. A method for treating sodium ferrate characterized by supplying it to a granulation process.