JPS5936793A - Method and apparatus for recovering soda from pulp waste liquor - 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 The present invention provides improvements to pulp waste soda recovery methods and devices;
In particular, it concerns measures to streamline the causticization process for recovered chemicals.

The conventional alkali pulp production method will be explained using δ, which is a schematic explanatory diagram showing the entire alkali pulp production process shown in FIG.

In Figure 1, 1 is for pulp cooking, 2 is a blow tank for pulp material, P is for pulp, 5 is an evaporator for concentrating waste liquid, 4 is a chemical recovery boiler (hereinafter referred to as recovery boiler), and 5 is for smelt dissolution. 6 is a causticizing tank, 7 is a rotary kiln, 8 is a white liquor tank, and 9 is an electrostatic precipitator.

Pulp cooking chemicals are supplied to the digester 1 or causticizing tank 6, followed by the blow tank 2, evaporator 5, recovery boiler 4, smelt dissolving tank 5, causticizing tank 6, and white liquor tank 8. It circulates through the circulation system PL. The calcium carbonate produced in the causticizing tank 6 is transferred to the rotary kiln 7.
It is calcined to form calcium oxide and recycled for causticization pJJ16. In addition, some of the chemicals in the recovery boiler 4 (part of the flue) are scattered as dust (most of which is collected by the electrostatic precipitator 9 and returned to the black liquor line). Don't send it, it will be roasted hot.

In the conventional method, the alkaline waste liquid is combusted in a recovery boiler 4. The smelt produced here is dissolved in water in a smelt dissolving tank 5 to produce a sodium carbonate aqueous solution. This sodium carbonate is Oa (
OHI 2 (also r, 10aO and 1(20) are brought into contact and causticized with caustic soda, which is a cooking chemical, as shown in the following formula: 0 Na200. + Ca(OH)2 −+
2NaOH+ CaCO3 On the other hand, 1cac○3 produced in the causticizing tank 6 is calcined in the rotary kiln 7 and converted to C
aO, quenched with water to produce Ca(OH1z'l), and circulated in the causticizing tank 6 for one cycle.

The disadvantage of the above conventional method is that the CaCO3 generated in the causticizing tank 6
The present invention saves energy in the firing of CaCO3 slurry produced in the causticizing tank 6, and streamlines the causticizing process for the I-reggie and recovered chemicals. The purpose is to provide a waste soda recovery method and device, in which powder containing mainly CaCO3 is supplied to the pulp waste liquid combustion section of a recovery boiler, QaO is fired in the recovery boiler furnace, and QaO is fired in the same furnace. The main purpose of this method is to guide most of the OaO that is produced along with the smelt flowing down the furnace wall to the soda dissolving tank at the bottom of the recovery boiler and recover soda and calcium. CaCO3 in the causticizing equipment
The unfired powder can be fed into the recovery boiler combustion section. Therefore, the CaCO3 burning means, for example, a rotary kiln, can be eliminated and fuel costs can be saved.The first aspect of the present invention is that when pulp waste liquid is spray-combusted in a soda recovery boiler, carbon dioxide is added to the pulp waste liquid/combustion section of the recovery boiler. Powder containing mainly calcium is supplied and calcium oxide is calcined in the recovery boiler furnace, and most of the calcined calcium oxide in the furnace is dissolved in soda at the bottom of the recovery boiler along with smelt flowing down the furnace wall. The second invention is a soda recovery boiler that sprays and burns pulp waste liquid, and is arranged so as to open into the pulp waste liquid combustion section of the recovery boiler. The method and apparatus of the present invention are characterized by comprising a supply port for powder mainly containing carbonate, and a soda dissolving tank disposed at the bottom of a recovery boiler to recover waste soda and calcium. This invention is effective when applied to a valve steam jVR chemical recovery boiler in a paper and pulp mill, which is an energy-intensive industry.Hereinafter, the present invention will be explained with reference to FIG. 2.In the figure, 10 is the recovery boiler body. , the lower part is tilted in the shape of a funnel and has a tension formed so that the smelt can easily flow down. 011 is the boiler bank part connected to the flue, 12 is the pulp waste liquid, 'coote, 15 and 14 are each 1 Secondary and secondary air supply ports, 15 (l″j: Powder mainly containing calcium carbonate, such as limestone CaCO3, dolomite CjaCO
3. This is the supply port for MSFCO3, etc. Note that the above powder may be added to the pulp waste liquid supply system. 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 white liquid take-out pipe 19 is the same white liquid take-out pipe 18.
20 is a white liquor supply pipe connected to the white liquor tank 19, and 21 is a calcium carbonate slurry take-out pipe connected to the bottom of the soda dissolving tank 16.

In such a configuration, highly concentrated alkaline pulp waste liquid is stored in the bottom of the furnace, which is the pulp waste liquid combustion part of the zero recovery boiler 10, which will explain the operation of the present invention.
The primary and secondary components are sprayed in fine particles from 2 and supplied to the bottom of the furnace.
Next, smelt (mainly Na2C03) is burned at high temperature with heated air supplied from air supply pipe 15.14 'fr:
generate. At this time, the bottom of the furnace is tilted in the shape of a funnel as shown in the figure, so that the flow of the smelt is favorable. .

Furthermore, powder containing calcium carbonate as the king at the bottom of the furnace,
For example, limestone CaCO3 powder is injected into the furnace from the supply port 15. Calcination in a furnace (CaCO3→cao + CO2
) Most of the dissolved CaO is carried on the smelt flowing down the furnace wall and is caused to flow down into the soda dissolving tank 16 at the bottom. Inside the soda dissolving tank 16, the water is supplied from the water supply pipe 17.
When smelt (Na2CO3, Ca0) is dissolved in water, the following reaction occurs.

Na2003 + OaO+ H2O-) 2NaOH
+ NaOH which is a cooking chemical like CaCO3
On the other hand, the NMOH generated in the soda dissolving tank 16 is led to the white liquor tank 19 from the white liquor outlet 18), and from the white liquor supply pipe 20, the NMOH produced in the soda dissolving tank 16 is fed to the white liquor cooking chemicals as shown in Fig. 1. The O a CO3 sent to the circulation system PL and the O a CO3 generated in the soda dissolving tank 16 are sent to the calcium carbonate slurry outlet 21
taken from.

The present invention provides the following effects.

(2) In the method of the present invention, in a soda recovery boiler that sprays and burns pulp glue, powder containing mainly calcium carbonate is supplied to the pulp waste liquid combustion section of the recovery boiler, and calcium oxide is completely burned in the recovery boiler furnace. By applying high temperatures in the furnace to causticize the product, there is no need for heating in a rotary kiln, which requires a large amount of fuel compared to conventional methods, and this has the advantage of significantly reducing fuel costs. be.

(b) Most of the calcium oxide calcined in the furnace is guided to the soda dissolving tank at the bottom of the recovery boiler together with the smelt flowing down the furnace wall. Soda dissolving tank - Stream 1: Can be stirred.The decomposition reaction of CaCO3 proceeds only by heating to about 890-900°C, so soda and calcium can be effectively recovered.

ri) Since there are few technical problems, it can be implemented with reasonable effort.

GT knee) The device of the present invention is a soda recovery boiler that spray-combusts pulp waste liquid, in which a supply port for supplying powder mainly containing calcium carbonate is provided so as to open into the pulp waste liquid combustion section of the recovery boiler, and a supply port is provided in the lower part of the recovery boiler. Since a soda dissolving tank is installed to recover soda and calcium, the smelt dissolving tank, causticizing tank, and rotary kiln can be eliminated compared to conventional equipment, which has the advantage of reducing manufacturing costs (i7).

(6) The furnace structure of the recovery boiler is almost the same as that of the alkaline pulp waste liquid recovery boiler, and the technology 1i11 has the advantage that the absorption is limited to a part of the bottom of the furnace.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a conventional alkali pulp manufacturing process a; Fukudaibe 1 person 1) February de, 1981. Commissioner of the Japan Patent Office Kazuo Wakasugi1, Indication of the case Patent Application No. 142137 of 19822, Name of the invention Pulp waste liquid soda recovery method and apparatus 3, Relationship with the person making the amendment Patent applicant address Chiyoda-ku, Tokyo Marunojiju-chome 5-1 i"'
(62o) Mitsubishi Heavy Industries, Ltd. (Name: Souyu Representative: Kaede Yano 4!x Agent address: 2nd Okada Building, 24-11 Toramon-chome, Minato-ku, Tokyo Phone: (504) 1894 Name:
Patent attorney (7179) 111
Akira (and 1 other person) 2. Contents of the amendment in column a of “Detailed Description of the Invention” of the specification subject to the amendment

Claims (1)

[Claims] n) When pulp waste liquid is spray-combusted in a soda recovery boiler, powder containing mainly carbonate is supplied to the pulp waste liquid combustion section of the recovery boiler, and calcium oxide is produced in the recovery boiler furnace. Pulp waste liquid soda is characterized in that most of the calcium oxide calcined in the furnace is guided along with smelt flowing down the entire furnace wall to a soda dissolving tank at the bottom of a recovery boiler to recover soda and calcium content. Collection method. (2) In a soda recovery boiler that spray-combusts valve waste liquid, there is a supply port for powder mainly containing calcium carbonate located right at the opening in the pulp waste liquid combustion section of the recovery boiler, and a soda recovery boiler located at the bottom of the recovery boiler. Pulp waste liquid soda recovery equipment 0, which has all the features of a soda dissolving tank and a soda dissolving tank that recovers the calcium content.