scholarly journals Effectiveness of magnesium oxide additives in mitigating fouling problems in kraft recovery boilers

TAPPI Journal ◽  
2013 ◽  
Vol 12 (6) ◽  
pp. 19-27
Author(s):  
LIMING ZHAO ◽  
HONGHI TRAN ◽  
F. DONALD MCCABE
Keyword(s):  
Magnesium Oxide ◽  
Systematic Study ◽  
Laboratory Tests ◽  
Coating Layer ◽  
Black Liquor ◽  
Oxide Content ◽  
Short Period ◽  
Kraft Recovery Boilers ◽  
Recovery Boilers ◽  
Laboratory Results

A systematic study was performed in the laboratory and in the field to examine the effect of magnesium oxide additive on deposit accumulation and removal. Laboratory results show that the additive has little effect on the amount of deposits collected on a probe, but it can make deposits easy to remove if a coating layer thicker than 30 μm can be effectively applied on the probe surface. The results also show that mixing the additive with black liquor or injecting it separately has no significant effect on deposit accumulation and removal. Tests performed in a recovery boiler where the additive was continuously injected show no evidence for the existence of the coating layer. The magnesium oxide content in the boiler deposits varied between 0.1 and 0.4 wt%, which is several times lower than the amount that was found to be effective in laboratory tests. Nonetheless, the additive was shown to be effective in facilitating deposit removal if it can form a coating layer on deposit/tube surfaces. This may be possible by periodically injecting a large amount of additive into the boiler for a short period and reducing the black liquor firing rate at the same time.

A novel method for determining the internal recycled dust load in kraft recovery boilers

TAPPI Journal ◽  
2014 ◽  
Vol 13 (8) ◽  
pp. 27-34
Author(s):  
MATHEUS ANTUNES GUIMARÃES ◽  
HONGHI TRAN ◽  
MARCELO CARDOSO
Keyword(s):  
Organic Carbon ◽  
Total Organic Carbon ◽  
Black Liquor ◽  
Organic Carbon Content ◽  
Kraft Recovery Boilers ◽  
Recovery Boilers ◽  
Boiler Operation ◽  
Novel Method ◽  
The Difference ◽  
Dust Load

In kraft recovery boiler operation, fly ash or dust generated from black liquor combustion is mixed with the virgin black liquor in a mix tank and returned to the boiler with the as-fired black liquor. This internal recycled dust stream varies widely from boiler to boiler and from time to time and can have a great impact on the as-fired black liquor flow and properties and, ultimately, on the boiler thermal performance. A new method has been developed to quickly and accurately determine the amount of internal recycled dust in recovery boilers. The method is based on the difference between the total organic carbon content of the virgin black liquor and that of the as-fired black liquor. Tests using the method were performed on recovery boilers at three of Fibria’s mills in Brazil. The results show that while the specific virgin black liquor solids produced at these mills were about the same, the internal recycled dust load varied widely, from as low as 4 wt% of as-fired black liquor solids fired in the boiler at one mill to as high as 15 wt% at another mill. Instead of total organic carbon values, heating values may also be used, but the result is not as accurate.

Fate of biosludge nitrogen in black liquor evaporation and combustion

TAPPI Journal ◽  
2012 ◽  
Vol 11 (9) ◽  
pp. 53-59 ◽  
Author(s):  
NIKLAS VÄHÄ-SAVO ◽  
NIKOLAI DEMARTINI, ◽  
MIKKO HUPA
Keyword(s):  
Black Liquor ◽  
Pulp Mill ◽  
Chemical Recovery ◽  
Process Data ◽  
Green Liquor ◽  
No Formation ◽  
Kraft Recovery Boilers ◽  
Recovery Boilers ◽  
Recovery Boiler ◽  
Clear Increase

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.

SANDVIK 3R12/4L7

Alloy Digest ◽  
1996 ◽  
Vol 45 (7) ◽  
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Carbon Steel ◽  
Black Liquor ◽  
Heat Treating ◽  
304L Stainless Steel ◽  
Design Load ◽  
Recovery Boilers ◽  
Major Application ◽  
Outside Diameter

Abstract Sandvik 3R12/4L7 is a composite tube consisting of type 304L stainless steel for corrosion resistance on the outside diameter and having carbon steel (A210 Gr. A1) as the inside component for both water wetted service and the design load. The major application is tubing to handle the corrosive conditions in black liquor recovery boilers. This datasheet provides information on composition, physical properties, microstructure as well as fatigue. It also includes information on forming, heat treating, and joining. Filing Code: SA-482. Producer or source: Sandvik.

Air port flow patterns in kraft recovery boilers

1996 ◽  
Vol 11 (2) ◽  
pp. 115-120
Author(s):  
D.C.S. Kuhn ◽  
T. Mao ◽  
H.N. Tran
Keyword(s):  
Flow Patterns ◽  
Kraft Recovery Boilers ◽  
Recovery Boilers

Evaluation of Uncertainty for the Determination of Magnesium Oxide Content in Limestone by the Atomic Absorption Spectrometry

2014 ◽  
Vol 707 ◽  
pp. 283-288
Author(s):  
Xiang Dong Wen ◽  
Zheng Zhou ◽  
Wen Yang Pan ◽  
Mei Shao
Keyword(s):  
Atomic Absorption Spectrometry ◽  
Atomic Absorption ◽  
Magnesium Oxide ◽  
Influence Factors ◽  
Absorption Spectrometry ◽  
Oxide Content ◽  
Standard Solution ◽  
The Mathematical Model

According to GB/T3286.1-2012(The determination of calcium oxide and magnesium oxide content in limestone and dolomite), the mathematical model of magnesium oxide content determination in limestone by atomic absorption spectrometry was established. The various uncertainty factors of different elements for a sample were discussed and compared in the testing process. The confidence interval for the measurement result was (0.74±0.03)%,k=2 in uncertainty evaluation .The results showed that the variability of working curve and accuracy of standard solution volume for working curve were main influence factors of uncertainty. It could effectively reduce the uncertainty from the perspective of the main factors,and improve the quality of analysis.

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