JPS62268889A - Direct causticizing furnace and starting method therefor - 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] [Industrial Application Field] The present invention relates to a direct causticizing fluidized bed system in which caustic soda is recovered from pulp cooking waste liquor (also referred to as black liquor) using iron oxide as a causticizing agent. relates to a direct causticizing furnace equipped with an air dispersion plate with low pressure loss (hereinafter referred to as ΔP) and a method for starting the same.

[Conventional technology]

BACKGROUND ART Conventionally, a lime method has been put into practical use when recovering caustic soda from pulp cooking waste liquid (hereinafter referred to as pulp 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 alkaline waste liquid is probably caused by the combustion of the waste liquid, which decomposes the organic matter contained in the waste liquid, and the soda carbonate and/or soda oxide obtained as a product is expressed by the following formula (1). It is thought that sodium ferrate is produced by reacting with iron oxide as shown in equation (2), and by treating this in water, caustic soda and iron oxide are obtained as shown in equation (3).

Na1CO3+FezO3−' Na=FezOt”
Cot (1)NatO+ Fe103-” Naz
FexO* +21NaiF13zO*
+LO-' 2NaOH+FezO3 (31However, when applying the above method to a fluidized bed furnace, in the direct causticizing method, the basic principle is to recycle and use iron oxide (iron ore), and to prevent carryover from dust collectors, etc. (The replenishment rate is on the order of several percent at most.) On the other hand, granular iron ore, which is a causticizing reactant as well as a fluidized bed maintenance agent, is being pulverized in the furnace as the number of recycled uses increases. (approximately 10% is powdered), and some powdering is also observed during handling of iron ore in the feeder, causticizing process, etc.Furthermore, in the fluidized bed method, granular causticizing agent is basically used. Therefore, the reaction molar ratio Fe/Na cannot be set close to 1.0 (equimolar reaction as shown in reaction equations (1) and (2)). There were problems such as the reaction immediately jumping out from within, making it impossible to expect the reaction to proceed sufficiently.

In order to solve the above problems, the present inventors causticized the powdered sodium ferrate collected in a fluidized bed boiler, cyclone, and electrostatic precipitator, 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 published Japanese Patent Application No. 167927-1983 (Japanese Patent Application No. 59190-1982).
A patent has been applied for.

The fluidized bed furnace in the above conventional method has a porosity of 0.8 to 1.
．． When starting up with a 5% air distribution plate installed, the temperature is raised in a hot blast furnace, and then fuel is blown directly into the fluidized bed using an LPG burner or kerosene burner to raise the temperature to 600-700°C and black liquor. is being invested.

[Problem that the invention seeks to solve]

However, when black liquor is added in a low temperature range (below 850°C), it takes time to start up because the gasification and combustion speed of the black liquor is slow, and black liquor usually contains impurities. Since it is easy to form a eutectic mixture, there are problems in that it tends to cause deterioration of the fluidization state such as agglomeration in the fluidized bed. Note that the melting point of Na2COi in black liquor is 850°C.

On the other hand, the fluidized bed method has a high ΔP, so the fan power etc. are large and the power cost is high, so the ΔP of the air distribution plate is
is required to be as small as possible.

In bed burners for gaseous fuels and liquid fuels, when the ΔP of the conventional air dispersion plate with a porosity of 0.8 to 1.5% is in the normal range, the mixing and diffusion state of the fluidized bed is good. There is no problem with ignition, but as efforts are made to reduce ΔP in contrast to air dispersion, the problem arises that the mixing becomes poor and the fuel is not efficient for anything other than granular or lumpy solid fuels for which residence time can be secured.

The present invention was made in view of the above points, and has a porosity of 1.
By using a low ΔP air dispersion plate of 5-3.0%,
The object of the present invention is to provide a direct causticizing furnace and a method for starting (method for using) the same, which can reduce the ΔP of the air distribution plate to 20,001 (,0 or less) and thus reduce power costs.

[Means and effects for solving the problems] The direct causticizing furnace of the present invention has a wind box at the lower part of the furnace body, and a fluidized bed is formed above the wind box through an air distribution plate. In a fluidized bed type direct causticizing furnace in which a black liquor nozzle, an iron ore inlet, and a combustion gas outlet are provided above the fluidized bed, the porosity of the air distribution plate is set to 1.5 to 3.0%. It is characterized by

In addition, the method for starting the direct causticizing furnace of the present invention has a wind box at the lower part of the furnace body, a fluidized bed is formed above the wind box through an air distribution plate, and black is placed above the fluidized bed. A direct causticizing furnace is equipped with a liquid nozzle, an iron ore inlet, and a combustion gas outlet, and the aperture ratio of the air distribution plate is 1.5 to 3.09A. It is characterized by introducing hot air to raise the temperature of the fluidized bed to 400-500°C, and then adding solid fuel such as wood, coal, oil coke, etc. to the fluidized bed and raising the temperature to 850-1000°C. .

Note that as the wood, park, knot, chip, etc. are used.

The porosity of the air distribution plate in the present invention is defined by the following formula.

〔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).

In Fig. 1, 1 is a direct causticizing furnace, which has a wind box 2 at the bottom of the furnace body, and a fluidized bed 4 is formed above the wind box 2 via a low ΔP air distribution plate 3. A black liquor nozzle 5, an iron ore inlet 6, and a combustion gas output lower are provided above the fluidized bed 4. Reference numeral 8 designates a granular sodium ferrate extraction port for extracting overflowing granular sodium ferrate, 9 a fuel inlet, 10 an air intake, 11 a water cooling wall, 12 a fireproof wall, and 13 a water cooling pipe. Note that water cooling pipes may not be installed.

As shown in FIGS. 2 to 4, the low ΔP air dispersion plate 3 has a 0-dispersion nozzle 140 having a cylindrical portion having a large number of dispersion nozzles 14 with a large number of radial openings 15 provided in the cylindrical portion. Its upper end is closed and is provided with an anti-deposition plate 16 to prevent the flow medium from accumulating thereon.

It is preferable that the hole diameter of the opening 15 is 6 WM or more, and the angle θ of the opening 15 with respect to the horizontal is 30'' or more.

When starting up the direct causticizing furnace 1 configured as described above, first, hot air generated in a hot blast furnace using liquid fuel such as kerosene is introduced into the fluidized bed 4, and the temperature of the fluidized bed is raised to 400 to 500.
After raising the temperature to 00°C, solid fuel such as wood, coal, oil coke, etc. is charged into the fluidized bed 4 through the fuel input port 9.
After raising the temperature to 50 to 1000°C, concentrated black liquor is introduced from the black liquor nozzle 5 to cause combustion and reaction.

〔Effect of the invention〕

Since the present invention is configured as described above, ΔP of the air dispersion plate can be reduced, and therefore, power costs can be reduced. Also, when starting up, use solid fuel to
Since the black liquor is sprayed after the temperature is raised to 50 to 1000°C, there is an effect that there is no possibility of a eutectic mixture being formed in the fluidized bed.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the direct causticizing furnace of the present invention, FIG. 2 is an enlarged sectional view of the low ΔP air distribution plate in FIG. 1,
Figure 3 is an enlarged sectional view of the dispersion nozzle in Figure 2;
The figure is an enlarged sectional view taken along the line A-A in FIG. 3. 1...Direct causticizing furnace, 2...-Wind box, 3-Low ΔP air distribution plate, 4...Fluidized bed, 5...-Black liquor nozzle, 6. −
・Iron ore inlet, 7-Combustion gas outlet, 8-Grained sodium ferrate outlet, 9--Fuel inlet, 10-Air inlet, 11
-・Water-cooled wall, 12-Fireproof wall, 13--Water-cooled pipe, 14-'
Dispersion nozzle, 15--opening, 16--deposition prevention provisional Fig. 1 Fig. 4

Claims (1)

[Claims] 1. A wind box is provided at the lower part of the furnace body, a fluidized bed is formed above the wind box via an air distribution plate, and a black liquor nozzle and iron ore are introduced above the fluidized bed. In a fluidized bed type direct causticizing furnace equipped with a combustion gas outlet and a combustion gas outlet, the porosity of the air distribution plate is set to 1.
5 to 3.0% Direct causticizing furnace 2 A wind box is provided at the lower part of the furnace body, a fluidized bed is formed above the wind box through an air distribution plate, and the fluidized bed is A liquid fuel such as kerosene is used in a direct causticizing furnace with a black liquor nozzle, iron ore inlet, and combustion gas outlet installed above the layer, and an air distribution plate with an aperture ratio of 1.5 to 3.0%. The temperature of the fluidized bed is raised to 400-500℃ by introducing hot air generated in a hot-blast oven, and then solid fuel such as wood, coal, oil coke, etc. is introduced into the fluidized bed and the temperature is raised to 850-1000℃. A method for starting a direct causticizing furnace characterized by: