Effect of polysulfide pulping process on the energy balance of softwood and hardwood 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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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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Study on Experimental Device of Removing TRS Gas with ClO2

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.834-836.1710 ◽

2013 ◽

Vol 834-836 ◽

pp. 1710-1717

Author(s):

Xue Ping Song ◽

Qiu Xia Xie ◽

Dong Hua Liang ◽

Wei Qiang Zhou ◽

Kai Huang ◽

...

Keyword(s):

Kraft Pulp ◽

Removal Rate ◽

Pulp Mill ◽

Sulfur Cycle ◽

Experimental Device ◽

Pulp Mills ◽

Kraft Pulp Mill ◽

Emission Standards ◽

Kraft Pulp Mills ◽

Designed Experiment

In order to remove the malodorous pollutants of total reduced sulfur (TRS) produced by kraft pulp mill, the experimental device was designed to remove the TRS gases in accordance with the principle of ClO2oxidizing TRS gases. After ClO2oxidizes TRS gases, the substances produced are absorbed by lye, which achieve the purpose of removing TRS gases. At the same time, these alkali absorber can be reused to the sulfur cycle of kraft pulp mills. With the self-designed experiment apparatus, the removal rate of H2S and CH3SH are 99.40% and 99.8% respectively, the concentration of H2S reduces from 1.275g/m3to 0.137mg/m3, the concentration of CH3SH reduces from 1.457g/m3to 0.032 mg/m3, which both reach national grade iii emission standards.

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

TAPPI Journal ◽

10.32964/tj19.3.139 ◽

2020 ◽

Vol 19 (3) ◽

pp. 139-148

Author(s):

MARYAM SADEGH MOUSAVI ◽

NIKOLAI DEMARTINI

Keyword(s):

Kraft Pulp ◽

Pulp Mill ◽

Field Studies ◽

Kraft Pulping ◽

Pulp Mills ◽

Recovery Cycle ◽

Green Liquor ◽

Green Liquor Dregs ◽

Kraft Pulp Mills ◽

Negative Effect

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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Consequences in a softwood kraft pulp mill of initial high alkali concentration in the impregnation stage

Nordic Pulp & Paper Research Journal ◽

10.1515/npprj-2018-0026 ◽

2019 ◽

Vol 34 (1) ◽

pp. 28-35 ◽

Cited By ~ 2

Author(s):

Elisabet Brännvall ◽

Ida Kulander

Keyword(s):

Kraft Pulp ◽

Pulp Mill ◽

Alkali Concentration ◽

Pulp Yield ◽

Kraft Pulp Mill ◽

White Liquor ◽

High Initial Concentration ◽

Softwood Kraft Pulp ◽

High Alkali ◽

Energy Balances

Abstract Impregnation with high initial concentration is fast and efficient, leading to a homogeneous delignification in the subsequent cook, resulting in improved screened pulp yield. To obtain high initial alkali concentration, the white liquor flow needs to be significantly increased. The moisture content of the wood chips and the alkali concentration of the white liquor limit the initial alkali concentration of the impregnation liquor that can be reached. It is therefore of interest to evaluate the possibility to implement high alkali impregnation (HAI) industrially and the consequences this would have on the mill system. The effect of HAI on mass and energy balances in a kraft pulp mill has been studied using mill model simulations. The sensitivity to disturbances in important parameters for process control has been compared to impregnation scenarios used industrially. It was shown that high initial alkali concentration can be achieved on industrial scale by increased white liquor flow. HAI has a positive effect on recovery flows and reduces the need for make-up chemicals. The HAI concept is less sensitive to variations in process parameters, such as chip moisture and white liquor concentration, thus diminishing the risk of alkali depletion in chip cores.

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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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99/01948 Performance and preliminary economics of black liquor gasification combined cycles for a range of kraft pulp mill sizes

Fuel and Energy Abstracts ◽

10.1016/s0140-6701(99)97718-4 ◽

1999 ◽

Vol 40 (3) ◽

pp. 201

Keyword(s):

Kraft Pulp ◽

Black Liquor ◽

Pulp Mill ◽

Kraft Pulp Mill ◽

Combined Cycles

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Effects of integrating a bioethanol production process to a kraft pulp mill

Nordic Pulp & Paper Research Journal ◽

10.3183/npprj-2010-25-02-p233-242 ◽

2010 ◽

Vol 25 (2) ◽

pp. 233-242 ◽

Cited By ~ 9

Author(s):

Jesse Kautto ◽

Kaj Henricson ◽

Herbert Sixta ◽

Mikaela Trogen ◽

Raimo Alén

Keyword(s):

Production Process ◽

Ethanol Production ◽

Kraft Pulp ◽

Black Liquor ◽

Pulp Mill ◽

Simulation Software ◽

Kraft Pulp Mill ◽

Excess Power ◽

Energy Balances ◽

Wood Consumption

Abstract The integration of an ethanol production process based on prehydrolysis of softwood chips to a kraft pulp mill is discussed. A simulation model of this biorefinery has been created with WinGEMS simulation software to calculate the mass and energy balances of the biorefinery and to examine the effects of the integration on the operation of the pulp mill. Integrating the prehydrolysis process to the modeled pulp mill producing 1000 Adt/day of pine pulp would increase the wood consumption by 16%. With the increased wood consumption, 40 t/day of ethanol could be produced, and the excess power production could be increased by 460 MWh/day. The integration of the ethanol production process to a pulp mill would have considerable effects on the operation of the pulp mill. The coupling of hydrolyzate evaporation with black liquor evaporation would require major modifications in the evaporation plant. Due to the burning of organic residue from the ethanol process and to the increase in the heating value of black liquor, the load on the recovery boiler would increase by 31%.

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Effects of added materials on black liquor combustion

TAPPI Journal ◽

10.32964/tj15.7.479 ◽

2016 ◽

Vol 15 (7) ◽

pp. 479-486

Author(s):

LIMING ZHAO ◽

DANIELLY CORTES ◽

HONGHI TRAN

Keyword(s):

Systematic Study ◽

Sodium Sulfate ◽

Kraft Pulp ◽

Black Liquor ◽

The Other ◽

Pulp Mills ◽

Combustion Behavior ◽

White Liquor ◽

Other Hand ◽

Kraft Pulp Mills

Black liquor is often mixed with various types of materials before being burned in a recovery boiler to meet specific needs of kraft pulp mills. A systematic study was conducted using a thermogravimetric combustor to examine how added materials might affect the combustion behavior of black liquors obtained from several pulp mills. The results show that adding soap, caustic, white liquor, and sawdust significantly reduces the liquor swelling tendency, thereby requiring a longer time for the liquor to burn completely. Adding makeup saltcake, precipitator ash, sodium sulfate, and biosludge, on the other hand, has little or no effect on the liquor combustion behavior.

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