JP3050950B2 - Cellulose waste liquid partial combustion method - Google Patents

Abstract

The present invention relates to a process for partial combustion of cellulose spent liquors using a burner connected to a reactor while adding an oxygen containing gas, maintaining a temperature of more than 700 DEG C within the reactor and that at least half of the non-fuel related amount of oxygen which shall be added to the reactor to partially combust the cellulose spent liquor added through the burner, is added to the reactor as a hot oxygen containing gas added through a channel arranged coaxially around a liquor lance provided for the addition of said cellulose spent liquor, whereby the weight ratio between the oxygen of the oxygen containing gas and the cellulose spent liquor solids is in the range of 0.1-0.7:1. <IMAGE>

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a method for the partial combustion of cellulose waste from the cellulose industry in a burner connected to a reactor, the burner being provided with a centrally located nozzle for applying liquid to its front end. A burner gun or liquid lance, and a tubular channel coaxially disposed around the liquid lance, wherein an oxygen-containing gas is added to the channel to support partial combustion, whereby the oxygen-containing gas is confined to the coaxially disposed channel. The vortex movement is given before entering.

[0002]

It is an object of the present invention to facilitate partial combustion of cellulosic waste liquor by using a burner that produces a stable autoignition flame at a low air / fuel ratio.

[0003] The cellulose industry produces waste liquids of different compositions depending on the delignification method used. Within the sulfate pulp manufacturing industry, the waste liquor, commonly referred to as black liquor, contains energy in the form of valuable chemicals and flammable carbon compounds. At present, these chemicals and energy are typically recovered in recovery boilers where the black liquor is completely burned.

[0004] The partial combustion of black liquor in a gasification reactor as in the present invention produces flammable gases containing H ₂ , CO, CO ₂ and droplets of molten inorganic chemicals.

[0005] With the bleaching of the pulp, a dilute liquor containing organics and sodium salts is obtained. Groundwood pulp and semi-chemical pulp manufacturing processes also produce dilute liquors of various compositions. These, as well as other waste products and effluents generated in the cellulose industry, can be used as feedstock in the process of the present invention after concentration.

The following description describes the invention as applying to black liquor, but the invention does not limit its application to only this particular liquid.

[0007] The mechanism for the partial combustion of black liquor is fairly well understood, especially applied to the lower part of a soda recovery boiler. However, there is a significant difference between the burner of the present invention and the liquid burner of the soda recovery boiler, particularly due to the low atomization of the liquid and the lack of a well-defined liquid flame, especially in the burner of the recovery boiler.

The main difference between the burner of the present invention and a conventional oil burner is that a stable flame is generated by the use of a fairly low amount of air or oxygen carrier.

As exemplified below, black liquor as a fuel is characterized by a relatively low calorific value and a high water and ash content.

[0010] The amount of heat generated by the dry substance 13 GJ / ton dry substance (D
S) Elemental composition C ₂₉ H ₃₄ O ₂₀ Na ₉ S ₂ Dry solids content 65% Viscosity at 100 ° C. 100 cSt The presence of sodium compounds in the black liquor and its inherent high oxygen content make the black liquor very reactive Fuel, which means that if a suitable burner design is at hand, the carbon conversion is already high in the flame zone, despite the fact that combustion is substoichiometric. Means

[0011]

SUMMARY OF THE INVENTION The spiral burner described in the present invention provides high combustion efficiency and flame stability using black liquor as fuel in a relatively small reactor volume. The temperature of the reactor is above 700 ° C, preferably around 900 ° C. The molten inorganic chemicals, substantially sodium carbon and sodium sulfide, are separated from the process gas in a quench dissolver connected to the reactor. The process gas consists essentially of carbon monoxide, carbon dioxide and hydrogen. The volume ratio of carbon monoxide to carbon dioxide is 0.8: 1 in the process gas.
〜1.8: 1, and is governed, for example, by the amount of oxygen added.

[0012] The flow pattern near the burner is significantly affected by the level of vortices that can be controlled, for example, by adjusting the swirl vane arrangement. The emission flow rate of the oxygen-containing gas is significantly affected by the maintained axial flow rate. The main principle of the spiral burner is to recirculate a part of the gas through the internal recirculation zone towards the liquid lance. This internal recirculation zone promotes combustion and stabilizes the flame, and the recirculated hot gas adds energy to the combustion of the liquid spray. The internal recycle zone also serves as a reservoir for heat and reactive gas components.

The mixing of the liquid spray with the combustion air is supported by a turbulent shear surface between the recirculation zone and the discharged gas and liquid droplets.

However, an outer recirculation zone, which is less important for flame stability, is also created. Its shape is more affected by the reactor geometry than by the burner geometry.

The degree of atomization of the liquid is very important to obtain a stable black liquor flame, flame spread and high carbon conversion. The rheological properties of the black liquor are of significant importance to the degree of atomization that can be achieved with a given nozzle. The viscosity of the black liquor is affected, for example, by heating and / or the addition of additives, and usually black liquor is used for the present invention.
Heated above 0 ° C. The viscosity of the black liquor at the moment of atomization should preferably be less than 200 cSt. Atomization of the black liquor is further promoted by rapidly flowing the black liquor into the reactor. In this case, the black liquor is preheated above the boiling point under the operating pressure of the reactor.

Although several types of atomizing nozzles are available, only a few are suitable in the present invention for atomizing cellulose liquor, such as black liquor.

A "twin-fluid" nozzle is optimal for use with the burner of the present invention. A common feature of "bi-fluid" nozzles is that relatively high gas flow rates are required to provide energy for atomization.
Another important feature of these nozzles is that the size of the droplets decreases as the density of the atomized gas increases. Depending on how the two fluid phases coalesce, several mechanisms for droplet formation, such as interligament shearing, liquid droplet sphere binding and formation, and high turbulent decomposition of liquid sprays, Can be expected.

Although the present invention describes a method for efficient substoichiometric combustion of cellulosic waste liquor using a burner connected to the reactor, the present invention provides a method for reducing the black liquor added by the burner. At least half of the amount of oxygen added to the reactor for partial combustion other than that required for medium combustion is added to the reactor in the form of a hot oxygen-containing gas, which is used for the addition of the cellulose waste liquor. is added through arranged distribution <br/> location tubular channels in the channel coaxially provided in the liquid lance into the liquid lance, 100 ° C. or higher, which is added by a burner, preferably 300 ° C. or less
The weight ratio between the amount of oxygen of the oxygen-containing gas preheated above and the amount of solids of the added cellulose waste liquor is between 0.1 and 0.
It is characterized by being in the range of 7: 1, preferably 0.15 to 0.5: 1.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings show a spiral burner and two different "dual fluid" nozzles.

FIG. 1 shows a swirl burner 1 placed in a combustion chamber 22 and a channel 2 for the purpose of adding air.
3 schematically shows a vortex generator 24 arranged in 3. The solid line in FIG. 1 is the spatial distribution of the inner recirculation-the dashed-dotted line indicates the inner recirculation zone, and the dashed line is the limit of the return flow, ie the limit along which the recirculation changes (axial zero velocity line). )
Is shown. The dashed line at the bottom of FIG. 1 also shows the outer recirculation limit. The vortex generator 24 is positioned substantially behind the lower part of the liquid lance 1, which means that the combustion air added to the outside of the nozzle encounters the atomized black liquor around the liquid lance 1 before transporting it. It means to circulate. Vortex generator 24
By properly arranging the conic curve rotation surface (toroi
A flame with a swirl of dai) is developed. This has important advantages for flame stability and partial combustion development.

FIGS. 2 and 3 show that liquid and gas are mixed,
Shown is a twin-fluid nozzle which is then pushed under high pressure by several symmetrically arranged circular openings 3.
These openings consist of two tubes 4 and 5, the so-called Y
The end of a jet spray nozzle, the former being in contact with an outer tube 6 for the purpose of adding black liquor, the latter for the purpose of adding atomizing gas such as air or steam. It is in contact with the inner concentric annular tube 7. The plurality of openings 3 diverge and diffuse to create an atomized jet that diffuses from the lower portion 2 of the liquid lance 1. Body of liquid lance 1
The hood 9 fitted in 0 holds the Y-jet atomization unit 8 at a fixed position. The fuselage 10 surrounds concentric annular tubes 6 and 7. Black liquor passes through the suction pipe 20 and air passes through another suction pipe 21 to the liquid lance 1.
Will be introduced.

FIGS. 4 and 5 show three concentric annular tubes 11,
1 shows an embodiment of a burner gun having 12 and 13. Air is supplied through outer and middle tubes 11 and 13 while black liquor is supplied through middle tube 12. The air is divided by the eighteen symmetrically distributed holes 14 and 15 shown in the figure, while the black liquor is forced through the annular gap 16. The holes 14 are obliquely oriented in one direction and the holes 15 are obliquely oriented in the opposite direction. Black liquor meets the edge 17 which is fed through the gap 16 and pushes it inward. The black liquor, now in the form of a thin film, passes through the holes 16 and encounters the incoming air and is atomized. This initial air-black liquor mixture meets additional air outside the rim 17 and creates a diffusing jet of finely dispersed black liquor. Black liquor passes through the suction pipe 20 and air flows through the suction pipe 2.
1 and each is added to the burner.

Although air has been used in the above description, the present invention is not limited to air, but also uses other gases, such as steam, nitrogen or oxygen-enriched air, as atomizing gas. Can be.

When designing a burner, great attention must be paid to the weight relationship between air and added fuel.

The black liquor described herein is a fuel with unusual properties, and burners that will provide a stable flame must be designed accordingly.

Different fuels contain different amounts of chemically bound oxygen. Bituminous coal usually contains 4 to 10% bound oxygen. Fuel oils contain less than 1% bound oxygen.

The black liquor dry solids contain about 35% by weight of bound oxygen, calculated on dry matter. This affects the design of the burner for black liquor combustion because only a small amount of oxygen, air or oxygen-enriched air needs to be added to the burner to obtain the desired level of combustion.

The air / fuel ratios (weight ratios) of some fuels in stoichiometric combustion are exemplified below: anthracite air / fuel 10-12: 1 ethyl alcohol 〃9: 1 black liquor 〃4-5 : 1 diesel oil / heavy oil １３ 13-15: 1 The burner for partial combustion of black liquor according to the present invention is 0.5 to 3:
Designed for one order of air / fuel solids. This is therefore much lower than the stoichiometrically applied ratio, as well as the substoichiometric combustion of most other fuels. About 23 air
The black liquor burner of the present invention has a content of 0.1% by weight of oxygen.
Designed for added oxygen / added black liquor solids ratio in the range of 1-0.7: 1. Air must be at least 100 to compensate for the low air / fuel ratio and achieve reasonable gas velocities.
C., preferably 300.degree. C., and should be provided with a swirling motion. Air preheating adds energy to the immediate vicinity of the burner and further supports flame stability. Most of the oxygen required for partial combustion is added by channels coaxially arranged around the liquid lance, which also terminates in the reactor as diffuser burner tiles. The oxygen portion required for the partial combustion can be added to the combustion zone through a spray nozzle and optionally through a second air port at the top of the reactor.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a spiral burner with a recirculation zone.

FIG. 2 is an axial cross-sectional view of one embodiment of a “bi-fluid” nozzle.

FIG. 3 is a front view of a nozzle section taken along line III-III in FIG. 2;

FIG. 4 is an axial sectional view of a second embodiment of a “dual-fluid” nozzle.

FIG. 5 is a front view of a nozzle section taken along line VV in FIG. 4;

[Explanation of symbols]

 1 spiral burner 23 channels

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) D21C 11/12

Claims (1)

(57) [Claims] 1. A method for partial combustion of a cellulose waste liquid using a burner connected to a reactor while adding an oxygen-containing gas, wherein a temperature of 700 ° C. or more is maintained in the reactor and the cellulose added by the burner is used. Necessary for medium combustion of oxygen added to the reactor to partially combust waste liquid
A channel provided in a liquid lance for addition of the cellulose waste liquid, at least half of the amount other than the required amount;
Coaxially above 100 ° C. which is added through a channel arranged in the liquid lance, pre preferably above 300 ° C.
Cellulose characterized by being added to the reactor as a heated hot oxygen-containing gas, whereby the weight ratio of oxygen of the oxygen-containing gas to solids of the cellulose waste liquid is in the range of 0.1 to 0.7: 1. Partial combustion method of waste liquid.