Fate of phosphorus in the recovery cycle of the kraft pulping process

The accumulation of nonprocess elements in the recovery cycle is a common problem for kraft pulp mills trying to reduce their water closure or to utilize biofuels in their lime kiln. Nonprocess elements such as magne-sium (Mg), manganese (Mn), silicon (Si), aluminum (Al), and phosphorus (P) enter the recovery cycle via wood, make-up chemicals, lime rock, biofuels, and process water. The main purge point for these elements is green liquor dregs and lime mud. If not purged, these elements can cause operational problems for the mill. Phosphorus reacts with calcium oxide (CaO) in the lime during slaking; as a result, part of the lime is unavailable for slaking reactions. The first part of this project, through laboratory work, identified rhenanite (NaCa(PO4)) as the form of P in the lime cycle and showed the negative effect of P on the availability of the lime. The second part of this project involved field studies and performing a mass balance for P at a Canadian kraft pulp mill.

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Formation of pirssonite in green liquor handling systems

TAPPI Journal ◽

10.32964/tj12.7.33 ◽

2013 ◽

Vol 12 (7) ◽

pp. 33-41 ◽

Cited By ~ 7

Author(s):

TASNUVA ZAKIR ◽

HONGHI TRAN ◽

VLADIMIROS G. PAPANGELAKIS

Keyword(s):

Sodium Carbonate ◽

Kraft Pulp ◽

Pulp Mill ◽

Pulp Mills ◽

Hard Scale ◽

Kraft Pulp Mill ◽

Green Liquor ◽

Kraft Pulp Mills ◽

Alkali Salts

The formation of pirssonite is commonly believed to be the cause of hard-scale buildup in green liquor handling systems in kraft pulp mills. The precipitation occurs when the concentration of sodium carbonate in the liquor exceeds the solubility of pirssonite. A laboratory study was conducted to systematically determine the causticizing conditions under which pirssonite precipitates. The results confirmed literature data showing that the solubility of pirssonite increases with temperature but decreases with increased concentrations of sodium carbonate and other sodium salts present in the green liquor. The solubility data obtained were used to create a database for pirssonite formation in OLI, a thermodynamic program for predicting phase stabilities of alkali salts in aqueous solutions. The OLI program, with the newly created database, was subsequently used to generate a series of pirssonite solubility curves in terms of saturated total titratable alkali that can be used as operational guidelines to prevent pirssonite precipitation and hard-scale formation in green liquor handling systems. A case study was performed using these solubility curves to explain the occurrence of the pirssonite deposition problem at a kraft pulp mill.

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The solubility of calcium carbonate in green liquor handling systems

TAPPI Journal ◽

10.32964/tj18.10.595 ◽

2019 ◽

Vol 18 (10) ◽

pp. 595-602

Author(s):

ALISHA GIGLIO ◽

VLADIMIROS G. PAPANGELAKIS ◽

HONGHI TRAN

Keyword(s):

Calcium Carbonate ◽

Systematic Study ◽

Kraft Pulp ◽

Thermodynamic Simulation ◽

Solubility Data ◽

Pulp Mills ◽

Persistent Problem ◽

Green Liquor ◽

Kraft Pulp Mills ◽

Salt Systems

The formation of hard calcite (CaCO3) scale in green liquor handling systems is a persistent problem in many kraft pulp mills. CaCO3 precipitates when its concentration in the green liquor exceeds its solubility. While the solubility of CaCO3 in water is well known, it is not so in the highly alkaline green liquor environment. A systematic study was conducted to determine the solubility of CaCO3 in green liquor as a function of temperature, total titratable alkali (TTA), causticity, and sulfidity. The results show that the solubility increases with increased temperature, increased TTA, decreased causticity, and decreased sulfidity. The new solubility data was incorporated into OLI (a thermodynamic simulation program for aqueous salt systems) to generate a series of CaCO3 solubility curves for various green liquor conditions. The results help explain how calcite scale forms in green liquor handling systems.

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Mill experience of calcium carbonate scale formation in green liquor pipelines

TAPPI Journal ◽

10.32964/tj19.8.387 ◽

2020 ◽

Vol 19 (8) ◽

pp. 387-397

Author(s):

ALISHA GIGLIO ◽

HONGHI TRAN ◽

MARIA BJORK ◽

RICKARD WADSBORN ◽

HAL LAGIMODIERE ◽

...

Keyword(s):

Kraft Pulp ◽

Temperature Drop ◽

Metal Substrate ◽

Scale Formation ◽

Operating Conditions ◽

Pulp Mills ◽

Green Liquor ◽

Kraft Pulp Mills ◽

High Degree ◽

Calcium Carbonate Scale

Experience of hard calcite (CaCO3) scale formation in green liquor pipelines at four kraft pulp mills was systematically investigated to determine if there is any correlation between the severity of the scaling problem at each mill and the design and operating conditions of its causticizing plant. The results show that the high degree of supersaturation of calcium ions (Ca2+) in the liquor is the main contributing factor. Mills that operate at a lower green liquor total titratable alkali (TTA), higher causticity, and a larger liquor temperature drop are more likely to pro-duce a green liquor that is supersaturated with Ca2+, and thus experience more severe scaling problems. In order to minimize CaCO3 scaling, the green liquor handling equipment should be operated as steady as possible to avoid conditions that allow Ca2+ to be supersaturated. The strategies include minimizing variations in liquor TTA, insulating the green liquor pipelines to reduce temperature gradients, and adding lime mud to weak wash to provide seeds for precipitation to occur on mud particles instead of on metal substrate.

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Method for analysis of ClO2 and Cl2 air emissions from pulp mill

Nordic Pulp & Paper Research Journal ◽

10.1515/npprj-2018-0012 ◽

2019 ◽

Vol 34 (1) ◽

pp. 19-27

Author(s):

Kimona Häggström ◽

Magnus Gunnarsson ◽

Katarina Bremert-Jirholm ◽

Nina Simic

Keyword(s):

Chlorine Dioxide ◽

Analytical Method ◽

Kraft Pulp ◽

Pulp Mill ◽

Air Emissions ◽

Pulp Mills ◽

Limit Of Quantification ◽

Regulatory Standards ◽

Low Concentrations ◽

Kraft Pulp Mills

Abstract Chlorine dioxide is commonly used as a bleaching agent in kraft pulp mills. Scrubbers are required to remove any remaining ClO2 from the plant tail gases. To control the air emissions of chlorine compounds, chlorine dioxide and chlorine contents must be monitored to ensure that the strict regulatory standards are met. However, the currently used analytical method is not suitable for detection of low concentrations of chlorine and chlorine dioxide. A new method for measuring chlorine dioxide and chlorine emissions was developed, which ensures compliance with the stringent requirements imposed by the authorities. The two species could be measured separately with a limit of quantification of 3 ppm. The method was robust and easy to use in the pulp mill environment and it was validated both in the laboratory and the field. The specificity of the method was demonstrated, Cl2 analysis was not sensitive to the presence of ClO2 and vice versa. The uncertainty (±2×RSD) of the analytical method in the field was estimated from duplicate measurements performed in the range of 3–500 ppm for ClO2 and 3–300 ppm for Cl2, and was found to be ±20 % and ±10 %, respectively. Possible interferences in the analytical method are also discussed.

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Some Toxic Constituents of Chlorination-Stage Effluents from Bleached Kraft Pulp Mills

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f81-100 ◽

1981 ◽

Vol 38 (7) ◽

pp. 739-743 ◽

Cited By ~ 23

Author(s):

A. B. McKague

Keyword(s):

Gas Chromatography ◽

Rainbow Trout ◽

Kraft Pulp ◽

Pulp Mill ◽

Salmo Gairdneri ◽

Pulp Mills ◽

Juvenile Rainbow Trout ◽

Bleached Kraft Pulp ◽

Toxic Materials ◽

Kraft Pulp Mills

Constituents responsible for the toxicity of a sample of bleached kraft chlorination-stage effluent to juvenile rainbow trout (Salmo gairdneri) were investigated. Tetrachlorocatechol, 3,4,5-trichlorocatechol, and 2,6-dichlorohydroquinone were identified and evidence was obtained for the presence of other chlorodihydroxybenzenes in toxic acidic fractions of the sample. Concentrations of 0.46 mg/L 3,4,5-trichloro- and 0.74 mg/L tetrachloro-catechol were estimated in the sample by analytical gas chromatography. Toxic materials in the nonacidic fraction were not identified although the nontoxic dichloromethyl methyl sulfone was isolated.Key words: chlorination-stage effluent, toxicity, pulp mill, chlorocatechols, chlorodihydroxybenzenes

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Cleavage of acetyl groups from northeast hardwood for acetic acid production in kraft pulp mills

TAPPI Journal ◽

10.32964/tj12.2.57 ◽

2013 ◽

pp. 57-67 ◽

Cited By ~ 7

Author(s):

RAVIKANT PATIL ◽

JOSEPH M. GENCO ◽

HEMAND PENDSE ◽

ADRIAAN VAN HEININGEN

Keyword(s):

Acetic Acid ◽

Kraft Pulp ◽

Ion Concentration ◽

Alkali Concentration ◽

Extraction Temperature ◽

Pulp Mills ◽

Hydroxide Ion ◽

Green Liquor ◽

White Liquor ◽

Kraft Pulp Mills

This study identified the optimum conditions for cleavage of acetyl groups from wood hemicelluloses for possible conversion to salts of acetate or to acetic acid in kraft pulp mills. Acetyl groups in wood hemicelluloses can be hydrolyzed by either OH- (hydroxide) or H+ (hydronium) ions. Experimental data are presented for the extraction of industrial northeast hardwood chips using alkali streams that are available in the kraft pulp mills: caustic, green liquor, and white liquor. The effects of extraction time, chip soaking temperature, alkali concentration, and extraction temperature on cleavage of acetyl groups were investigated. Soaking at elevated temperature was found to be more effective than no soaking or soaking at room temperature. The rate of cleavage of acetyl groups from wood hemicelluloses was proportional to the initial hydroxide ion concentration in the liquor. Both white liquor and 0.5 N sodium hydroxide had higher rates of hydrolysis of acetyl groups compared to green liquor, which contained fewer hydroxide ions. The initial hydroxide ion concentration in the liquor also determined the mechanism by which acetyl groups were hydrolyzed from the hemicellulose backbone. If the extraction liquor contained excess hydroxide ions, then most acetyl groups were directly hydrolyzed from the xylan polymer to form sodium acetate, and the xylan remained in the wood, provided the temperature was low. The extraction temperature had a negligible effect on rate of cleavage of acetyl groups if the liquor contained excess hydroxide ions.

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Inorganic Waste Generated in Kraft Pulp Mills: The Transition from Landfill to Industrial Applications

Applied Sciences ◽

10.3390/app10072317 ◽

2020 ◽

Vol 10 (7) ◽

pp. 2317 ◽

Cited By ~ 2

Author(s):

Margarida J. Quina ◽

Carolina T. Pinheiro

Keyword(s):

Kraft Pulp ◽

Construction Materials ◽

Industrial Process ◽

Pulp Mill ◽

Industrial Applications ◽

Raw Material ◽

Pulp Mills ◽

Waste Products ◽

Kraft Pulp Mills ◽

Inorganic Waste

Kraft pulp mills produce the main raw material for paper, while several waste products are generated in large quantities in the process. This review study addresses four of the main inorganic wastes formed by this industry, namely green liquor dregs (GLD), slaker grits (SG), lime mud (LM) and boiler fly ash (BFA), which are still mostly discarded in landfills. A brief overview of a typical industrial process was included to outline the waste generation points. The main chemical and physical properties are indicated for highlighting the most relevant characteristics to determine which applications may be considered in each case. An in-depth literature review allowed the identification of the main applications that have been tested mainly at the laboratory scale and some at an industrial scale. The applications are grouped into construction materials, geotechnical, environmental, agricultural and others. This assessment shows that the circular economy and the sustainable development goals of the UN are important issues for organizations in general, and the pulp mill in particular. In fact, this industry has managed to close the chemicals loops, recover energy and reduce water consumption in the process. However, the current situation of inorganic waste can still be improved if industrial applications are developed to avoid landfill.

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Effect of polysulfide pulping process on the energy balance of softwood and hardwood kraft pulp mills

Nordic Pulp & Paper Research Journal ◽

10.1515/npprj-2021-0026 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Satu Lipiäinen ◽

Katja Kuparinen ◽

Esa Vakkilainen

Keyword(s):

Kraft Pulp ◽

Energy Use ◽

Process Development ◽

Black Liquor ◽

Pulp Mill ◽

Electricity Production ◽

Pulp Yield ◽

Pulp Mills ◽

Kraft Pulp Mill ◽

Kraft Pulp Mills

Abstract Polysulfide pulping is a method to increase the pulp yield in a kraft pulp mill. Higher production is in the core of pulp mill process development, but modifications in cooking raise questions on their effects on the other parts of the process. This study focuses on the impacts of polysulfide pulping on the energy use and production of kraft pulp mills. The impacts are estimated by calculating and analyzing the steam and electricity balances of reference softwood and hardwood mills. Energy generation using residual biomass is an essential part of the operation of a kraft pulp mill, and often a notable source of income. The results show that implementation of polysulfide cooking affects both energy consumption and production. Higher hemicelluloses content of pulp cooked using polysulfide liquor means that less organic material ends up in the black liquor. Subsequently, the recovery boiler energy production suffers. The reduced steam production together with increased steam consumption decreased electricity production, corresponding to a decline in sellable electricity of 22.4 % in the hardwood mill and 28.4 % in the softwood mill. The study shows that increasing the pulp production by investing in polysulfide cooking in stand-alone kraft pulp mills can be economically feasible.

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The feasibility of utilizing existing process streams in kraft pulp mills as a source of chemicals for lignin extraction

BioResources ◽

10.15376/biores.16.1.1009-1028 ◽

2020 ◽

Vol 16 (1) ◽

pp. 1009-1028

Author(s):

Jonas Kihlman ◽

Christer Gustavsson

Keyword(s):

Kraft Pulp ◽

Pulp Mill ◽

Kraft Pulping ◽

Raw Material ◽

Pulp Mills ◽

Chemical Balance ◽

Lignin Extraction ◽

Wet Gas ◽

Lignin Recovery ◽

Carbon Dioxide Co2

Lignin is a sustainable raw material with a high potential for use in the production of renewable products. While the market for lignin is slowly growing, lignin recovery via acid precipitation during the kraft pulping process requires the addition of chemicals that will impact the chemical balance of the pulp mill. This negatively affects both the environmental and business operations. Utilizing existing process streams as a source of chemicals will allow the mill to close the chemical loop and reduce emissions, which will have positive environmental impacts. This study investigated the internal production of sulphuric acid (H2SO4) and carbon dioxide (CO2) for use in lignin separation (also called extraction) at a Swedish kraft pulp mill. The process simulation tool CHEMCAD was used to model and analyze the wet gas H2SO4 (WSA) process to produce H2SO4. The chemical absorption process using monoethanolamine (MEA) to capturing CO2 was also analyzed. The utilization of the sulphur-containing gases to produce H2SO4 can generate an amount that corresponds to a significant lignin extraction rate. The CO2 available in the flue gases from a mill well exceeds the amount required for lignin extraction.

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Sources, collection, and handling of noncondensible gases in modern kraft pulp mills

TAPPI Journal ◽

10.32964/tj18.5.297 ◽

2019 ◽

Vol 18 (5) ◽

pp. 297-305

Author(s):

KIRSI HOVIKORPI ◽

ESA VAKKILAINEN

Keyword(s):

Kraft Pulp ◽

Pulp Mill ◽

Pulp Mills ◽

Kraft Pulp Mills ◽

Odor Emissions ◽

Process Disturbances

This work describes and discusses sources of noncondensible gases (NCG) in modern kraft pulp mills and modern NCG collection from process units where odor emissions can occur if these gases are released to the surroundings. A mill-wide overview of NCG sources and collection in modern pulp mills is provided. Using modern practices, malodorous gases can be collected to the extent that a pulp mill is essentially odor free. The key to limiting complaint-causing odors is prevention of these emissions during process disturbances, equipment malfunctions, operator errors, and other unforeseen occurrences.

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