Investigation of KP Operational Conditions in Japanese KP Mills. Phase 3. Chemical Recovery Process (Black Liquor Evaporator, Recovery Boiler, Recausticizing, Lime calcining).

At many mills, biosludge, which has a high nitrogen content, is added to black liquor and burned in kraft recovery boilers. The aim of this work was to determine the fate of biosludge nitrogen in the high solids black liquor concentrators and in the recovery boiler. Specifically, does biosludge addition result in higher nitric oxide (NO) and cyanate formation during black liquor combustion? To obtain this information, samples were collected from the chemical recovery cycle of a Finnish kraft pulp mill along with relevant process data. Laboratory combustion experiments clearly showed an increase in NO formation for the mill black liquor with biosludge, but no clear increase in nitrogen oxide emissions was detected in the recovery boiler after biosludge addition. Analysis of the green liquor samples from the dissolving tank showed a significant increase in nitrogen exiting the recovery boiler as cyanate. This finding was supported by laboratory tests studying cyanate formation. The increased cyanate results in increased ammonia formation in the recausticizing cycle, which can lead to higher NO emissions, as seen in the noncondensible gas incinerator at the mill.

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Modeling fine particles and alkali metal compound behavior in a kraft recovery boiler

TAPPI Journal ◽

10.32964/tj11.7.9 ◽

2012 ◽

Vol 11 (7) ◽

pp. 9-14 ◽

Cited By ~ 2

Author(s):

AINO LEPPÄNEN ◽

ERKKI VÄLIMÄKI ◽

ANTTI OKSANEN

Keyword(s):

Alkali Metal ◽

Computational Models ◽

Fine Particles ◽

Black Liquor ◽

Melting Behavior ◽

Metal Compound ◽

Effect Of Temperature ◽

Particle Model ◽

Boiler Furnace ◽

Recovery Boiler

Under certain conditions, ash in black liquor forms a locally corrosive environment in a kraft recovery boiler. The ash also might cause efficiency losses and even boiler shutdown because of plugging of the flue gas passages. The most troublesome compounds in a fuel such as black liquor are potassium and chlorine because they change the melting behavior of the ash. Fouling and corrosion of the kraft recovery boiler have been researched extensively, but few computational models have been developed to deal with the subject. This report describes a computational fluid dynamics-based method for modeling the reactions between alkali metal compounds and for the formation of fine fume particles in a kraft recovery boiler furnace. The modeling method is developed from ANSYS/FLUENT software and its Fine Particle Model extension. We used the method to examine gaseous alkali metal compound and fine fume particle distributions in a kraft recovery boiler furnace. The effect of temperature and the boiler design on these variables, for example, can be predicted with the model. We also present some preliminary results obtained with the model. When the model is developed further, it can be extended to the superheater area of the kraft recovery boiler. This will give new insight into the variables that increase or decrease fouling and corrosion

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EXERGETIC ANALYSIS OF A CHEMICAL RECOVERY BOILER IN THE PULP AND PAPER INDUSTRY

10.26678/abcm.encit2020.cit20-0342 ◽

2020 ◽

Author(s):

Magno Salgado ◽

Vinícius Trindade ◽

Rogério José Silva

Keyword(s):

Paper Industry ◽

Pulp And Paper Industry ◽

Pulp And Paper ◽

Chemical Recovery ◽

Recovery Boiler ◽

Exergetic Analysis

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Biosludge Incineration in a Recovery Boiler

Water Science & Technology ◽

10.2166/wst.1999.0712 ◽

1999 ◽

Vol 40 (11-12) ◽

pp. 195-200 ◽

Cited By ~ 6

Author(s):

P. Harila ◽

V.-A. Kivilinna

Keyword(s):

Black Liquor ◽

Pulp Mill ◽

Effluent Treatment ◽

Attractive Alternative ◽

Net Energy ◽

High Moisture ◽

Primary Sludge ◽

Start Up ◽

Combustion Emissions ◽

Recovery Boiler

An activated sludge process is an effective tool against effluent emissions in a pulp mill. It has only a few features which can be regarded deficiences. One of them is that effluent treatment of a modern pulp mill creates some 10-20 tonnes dry solids of biosludge per day. This sludge is difficult to burn due to its high moisture content. The most common way is to mix biosludge with primary sludge, to dewater the mixture in presses and finally to burn it in a solid fuel boiler. This type of sludge treatment incurs rather high costs and does not produce any net energy. Also combustion emissions vary depending on the boiler type. The Metsä-Botnia Kemi Pulp Mill was the first mill in the world to burn biosludge in a recovery boiler. The system start-up was in 1993 and it has been in operation ever since. Mechanically dewatered biosludge is mixed with weak black liquor and concentrated in a conventional evaporation plant equipped with a pressurized superconcentrator unit. In a modern recovery boiler, firing conditions are well controlled and monitored. Better emission control than in most bark fired boilers is achieved. Accumulation of nonprocess elements, corrosion, plugging, scaling and some other operational problems were expected. A lot of experience has been gathered during the years of operation and reviewed in this presentation. The achieved benefits of the system are discussed. Disposal of biosludge in a recovery boiler offers an economically and environmentally attractive alternative. Probably the best evidence from this is the fact that Metsä-Botnia has applied the same process solution in the recent reconstruction of the recovery departments at the Jouteno Mill.

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