JPS5954621A - Method and apparatus for recovering soda from waste liquid of pulp - Google Patents

Abstract

PURPOSE:To save the heat of calcination in the titled recovery method, by eliminating a rotary kiln, combining the soda recovery boiler with the fluidized bed calcination apparatus for CaCO3, supplying a part of the waste liquid to the calcination apparatus, and introducing the exhaust gas of the calcination apparatus to the downstream of the boiler. CONSTITUTION:A concentrate alkali pulp waste liquid is sprayed through the burner 12 to the bottom of the combustion furnace of the recovery boiler 10, and burnt at high temperature by the primary and secondary hot air supplied from the lines 13, 14 to form smelt. The smelt is transferred to the soda dissolution tank 16 and dissolved. Separately, the pulp waste liquid supplied through the line 31 is burnt in the fluidized bed calcination apparatus 22 by the hot air supplied through the line 34, to keep the fluidized bed 22A at a high temperature. CaCO3 is calcined at the temperature, and the produced CaO is introduced into the tank 16, and made to react with the smelt component Na2CO3 to form NaOH. The obtained NaOH is introduced into the tank 19, and the produced CaCO3 is returned to the apparatus 22. The hot gas generated in the apparatus 22 is introduced into the cyclone 25 to separate the solid particles and introduced to the downstream of the boiler 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides improvements to pulp waste soda recovery methods and devices;
In particular, it concerns the rationality of the causticization process for recovered chemicals and countermeasures against blooms.

□Figure □'1 is a schematic explanatory diagram showing the alkali pulp manufacturing process. The conventional alkaline pulp manufacturing method will be explained below with reference to FIG.

Kaoru In Figure 1, 1 is a pulp digester, 2 is a blue tank for pulp material, Ph pulp, 3 is an evaporator for concentrating waste liquid, 4 is a chemical recovery boiler (hereinafter referred to as recovery boiler), and 5 is a Smelt decomposition tank, 6 is a causticizing tank, 7 is a rotor □ rekiln, 8 is a white liquor tank, and 9 is filtrated with a moth air dust collector.

The chemicals with a pulp of mm are supplied to a digester and a causticizing tank 6, followed by a broken tank 2, an evaporator 5, a recovery boiler 4. ,, smelt dissolving tank 5, causticizing tank λ, white liquor tag 8) 'Lt'l'? Steam product circulation system PL
cycle. Calcium carbonate produced in the causticizing tank 6 is converted into an oxidizing power by a low-temperature kiln 7 and used for circulation in the causticizing tank 6, and the chemicals are recycled in the recovery boiler 4. Most of the dust is scattered from the flue, but most of it is collected by the electrostatic precipitator 9, returned to the black liquor 1, and sent to the recovery boiler 4 to be burned. In the conventional method, the 1 alkali valve waste liquid is combusted in a recovery boiler 4, and the smelt produced is dissolved in water in a smelt dissolving tank 5 to produce a sodium carbonate aqueous solution. This F
Acid soda is then converted into sodium chloride with species 6 and 0a (O
It is brought into contact with T()+ (or CnO and H2O) and causticized into caustic soda, which is a cooking chemical, as shown in the following formula.

Na2003 +0a(OH)2-+ 2NaOH+
CFLCO3 Meanwhile, Ca c03 produced in causticizing tank 6
is calcined in a rotary kiln 7 to form CaO, slaked with water to generate Ca(OR)2, and recycled to the causticizing tank 6.

' □ The disadvantage of the above □゛ secondary method is that the amount of fuel used when firing the CAAO3 slurry produced in the causticizing tank 6 in a kiln is large.

An object of the present invention is to provide a valve waste liquid soda recovery boiler device that can save energy in the firing of the cBao and slurry produced in the causticizing tank 6 and streamline the process of causticizing the recovered chemicals. The rotary kiln used in the past was abolished, and a pulp waste liquid soda recovery boiler and a fluidized bed calciner for calcining calcium carbonate were used in combination.A part of the pulp waste liquid was supplied to the fluidized bed calciner, and a part of the pulp waste liquid was supplied to the fluidized bed calciner. The main purpose of this method is to introduce the carbonate to the downstream part of the soda recovery boiler, thereby reducing the amount of heat compared to the case where a conventional rotary kiln type calcium carbonate calcining device is used.

The first aspect of the present invention is that, in pulp waste soda recovery, charcoal 11P/calcium from the soda dissolving tank at the bottom of the valve waste soda recovery boiler or from the causticizing device of the expansion device is transferred to the same boiler, The calcium carbonate calcining flow, the 7-unit calcining unit, and the 7-unit calcining equipment were supplied to the furnace, and the calcined and plated calcium oxide was introduced to the soda dissolving, dissolving, or causticizing equipment. The waste liquid of B1/L7 is supplied to both the soda recovery boiler and the n-motion IF4 calciner for charcoal, acid, and calcination, and burned, and the exhaust gas from the fluidized bed and calciner is recovered with soda. Boiler exhaust, gas, suto: merging, letting, ru, ef: Concerning the characteristic valve waste liquid soda recovery method, the second
5. In a soda recovery boiler that sprays and burns tit valve waste liquid. Is it the same as the 1lb 1 layer firing equipment installed in the soda recovery boiler? IE fluidized bed calciner - 2 units, carbonation power connected to soda melting fpIt at the bottom of the installed recovery boiler or a separate causticizing tank, lucium 9 supply "1", and the above fluidized bed calciner/
・A fuel supply port for auxiliary combustion, a pulp waste liquid supply port, and a means for guiding the outlet waste gas of the fluidized bed firing apparatus to the downstream part of the recovery boiler are provided. Characteristics of pulp waste liquid saw 5 times" It is related to the pain device.

In the present invention, a smelt melting tank, a causticizing tank, and a causticizing tank are installed next to the recovery boiler as in the conventional method, and the C! aO03, is introduced into the fluidized bed calcination equipment.
However, as shown in the specific example below, the smelt melting tank next to the recovery boiler and the fluidized bed sintering device are directly connected, and in the δ melt melting tank, OaO and N from the fluidized bed sintering device are directly connected.
It is preferable to react the 32003 aqueous solution to produce Oa CQ3 and send the Oa CQ3 to the fluidized bed combustion apparatus because the causticizing tank can be omitted.

The method and apparatus of the present invention are effective when applied to pulp cooking chemical recovery boilers in pulp and paper mills, which are energy-intensive industries.

The present invention will be explained below with reference to FIG.
.

In the figure, 10 is the main body of the recovery boiler, which is a normal so, -,
This is the configuration of a waste recovery boiler. Reference numeral 11 designates a hole connected to the flue, an ira bank section, 12 a pulp waste liquid purse, and 15 and 14 primary and secondary air supply ports, respectively. 16 is a soda dissolving tank disposed at the bottom of the recovery boiler 10, 17 is a water supply port disposed to open at the top of the soda dissolving tank 16, and 18 is a water supply port disposed to open to the soda dissolving tank 16. The installed white liquid extraction pipe, 19, is the same white liquid extraction pipe! 1
B is a white liquor tank connected to it, 20 is a white liquor supply pipe connected to the same white liquor link 19, and 21 is a calcium carbonate slurry take-out pipe connected to the bottom of the soda dissolving tank 16.

22 is a fluidized bed firing device for firing calcium carbonate slurry attached to the recovery boiler main body 10, 23 is an air distribution plate at the lower part of the fluidized bed 22A in the same fluidized bed firing device 22, and 24 is the upper part of the fluidized bed firing device 22. 25 is a cyclone for solid particle 1,000-year dust connected to the exhaust gas extraction Ill L pipe 24, and 26 is a connecting pipe connecting the upper part of the cyclone 25 and the downstream part of the recovery boiler.

27 is the lower part of the cyclone 25 and the soda dissolving tank 1
6, 28 is a take-out pipe for the particles fired in the fluidized bed 22A in the fluidized bed firing apparatus 22, 29 is a rotary valve for adjusting the flow rate disposed in the take-out pipe 28, 30
is a connecting pipe connecting the rotary valve 29 and the soda dissolving tank 16.

Reference numeral 31 designates a pulp waste liquid supply port which is arranged to open into the fluidized bed 22A in the fluidized bed firing apparatus 22, reference numeral '52 designates a calcium carbonate supply port, and reference numeral 33 designates a fuel supply port for starting and auxiliary combustion. Reference numeral 34 denotes a heated air supply port for fluidizing the fluidized bed 22A, which is disposed so as to open at the bottom of the air distribution plate 23 of the fluidized bed firing apparatus 22, and for burning the valve waste liquid and cod meat.

In such a configuration, the operation of the present invention will be explained. , At the bottom of the furnace which is the pulp waste liquid combustion part of the recovery boiler 10,
Highly concentrated alkaline pulp waste liquid is sprayed in the form of fine particles from the burner 12, and combusted at high temperature with heated air supplied from the primary and secondary air supply W16°14 supplied to the bottom of the furnace to form smelt (mainly N steam). 20 (13) li produced 1, this smelt flows down from the bottom of the furnace into the soda melting tank 16 and is melted.

On the other hand, the pulp retentate supply port 31 is connected to the fluidized bed cooling device 22.
The pulp waste liquid supplied from
is maintained at a high temperature of around 1000 Tl.

At this temperature, calcium carbonate is calcined to calcyano oxide as described below.

OFl, 003 →C! ao + co2 generated oxidizing power is taken out 7 pipes 28, rotary pulp 29,
Through the connecting pipe 30, soda melting 4.4. fl 16 and reacts with the aforementioned smelt component Na2003 to produce the following reaction.

N132003 +OnO+ N20-+ 2NaOH
+CaO03 Thus the cooking chemical N FI
Make OH.

NaOH generated in the soda M decomposition tank 16 is removed from the white liquor outlet 18.
From there, it is led to a white liquid tank 19, and from a white liquid supply pipe 20, it is sent to a valve chemical circulation system PL as shown in FIG.

In addition, Ca C03 (':l) generated in the soda dissolving tank 16
', % The calcium carbonate slurry is taken out from the outlet 21, and after preliminary dehydration is returned to the fluidized bed sintering apparatus 22 which becomes the calcium carbonate sintering apparatus.

On the other hand, the high-temperature gas generated 17 in the fluidized bed firing device 22 is discharged from the exhaust gas take-off pipe 24, solid particles are separated and collected by the particle-collecting cyclone 25, and then guided to the downstream part of the recovery boiler through the connecting pipe 26. . The solid particles collected by Zyclone 25 are conducted through connecting pipe 27 to soda dissolution tank 16 or conventional causticizing equipment.

The present invention provides the following effects.

(g) Is it possible to replace the rotary kiln for carbonic acid calcining with a fluidized bed calcining device that has good contact between gas and solid and has good heat transfer? , , N) (= Savings can be made.

(a) Since valve waste liquid is used as part of the fuel for the fluidized bed firing device, fuel consumption can be reduced.

(1) Calcium carbonate particles in the calcium carbonate slurry discharged from the soda dissolving tank or causticizing device are fine particles, so in the fluidized bed device, the particles are likely to fly out, which slows down the gas velocity. Although it is necessary to increase the diameter of the device, the present invention can produce suitable pulp.

Since waste liquid is added, granulation occurs in the fluidized bed with the waste liquid and the soni/da content acting as a binder, which reduces the scattering of fine particles and increases the gas flow rate, so the equipment can be small. If there is too much pulp waste liquid, the particles will stick to each other and stop moving in the entire fluidized bed, so it is necessary to adjust the amount of addition appropriately.Specifically, the supply carbonic power is 1V by weight. c vs.! ,6
The upper limit is considered to be about 0.5 for Pal 7' waste liquid with a concentration of 0%.

)? M, when added to the pulp waste liquid as fuel for the moving bed, t
Part 1: Fine particles of N and CO3 fly in the 'l' gas.
1 Although it cannot be released into the atmosphere, heat recovery and exhaust gas desorption can be performed simultaneously by placing it in a 1-point circuit flue. Calcium 1 accompanying the exhaust gas has no effect on the recovery boiler.

0) Flow! The Nn content in the pulp waste liquid added to the lll1 layer is mostly recovered as Na2003, adhering to the oxidized calcyano particles. Na200sl'J: Since it is returned to the soda dissolving tank together with Calcillano^, it is recovered to the soda dissolving tank in the same way as 14 a2003 from the recovery boiler. ,.

[Brief explanation of drawings]

FIG. 1 is a flow heat method showing a conventional alkali pulp fJv manufacturing process, and FIG. 2 is a schematic diagram showing the method and apparatus of the present invention. Within the sub-agent [l Akira. Sub-Agent Ryo Hagiwara - Figure 1 Figure 2 i20'

Claims (2)

[Claims] (1) In pulp waste soda recovery, the carbonate calcined cam from the soda dissolving tank at the bottom of the Nokulpu waste liquid soda recovery boiler or the separate causticizing equipment is transferred to the carbonate gong runum kiln attached to the same soda recovery boiler. The calcined calcium oxide is fed to the fluidized bed sintering device for sintering, and the calcined calcium oxide is guided to the soda dissolving tank or causticizing device, and the calcined calcium oxide is fed to the soda recovery boiler and the carbonate sintering device. 1
Pulp □ part, ・
The liquid is supplied and combusted, and the exhaust gas from the fluidized bed calciner □ is combined with the soda recovery boiler exhaust gas. f: Characteristic pulp waste liquid soda recovery method. (2) In a soda recovery boiler that spray-combusts pulp waste liquid, a fluidized bed calcination device for calcium carbonate calcination attached to the above-mentioned soda recovery boiler, and a lower part of the recovery boiler arranged and installed in the same fluidized bed calcination device. Soda dissolving tank □
are a lucium carbonate supply port connected to a separate causticizing tank, an auxiliary combustion fuel supply port and a bulb waste liquid supply port provided to the fluidized bed calcination device, and a □ of the fluidized bed calcination device. Outlet waste: A pulp waste liquid puda recovery device characterized by comprising means for guiding gas to a downstream section of the soda recovery boiler.