Crossflow filtration of green liquor for increased pulp production, improved green liquor quality, and energy savings

A new green liquor filtration system has been installed and commissioned at the Ence pulp mill in Pontevedra, Spain. The filtration system is based on microfiltration and was developed in collaboration with the KTH Royal Institute of Technology in Stockholm, Sweden. The patented method for efficient purification of green liquor decreases the non-process element (NPE) content by providing more efficient solids/liquid separation, reducing energy and chemical consumption in pulp mills and increasing production capacity by eliminating certain capacity bottlenecks. The process has been continuously tested at the Aspa Bruk Mill outside Askersund, Sweden, since 2013. The technology has proven to create nearly particulate-free green liquor during the purification process. The technology can also be used to polish white liquor to provide higher pulp quality. To provide for a simple and cost-effective installation, the system was designed as a skid-mounted unit that is pre-piped, instrumented, and tested before shipment. The system is modular and allows for easy expansion of capacity. This paper discusses the process design, process integration, and startup of the new system, along with experiences from the first months of operation.

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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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A Process Integration Method for Total Site Cooling, Heating and Power Optimisation with Trigeneration Systems

Energies ◽

10.3390/en12061030 ◽

2019 ◽

Vol 12 (6) ◽

pp. 1030 ◽

Cited By ~ 11

Author(s):

Khairulnadzmi Jamaluddin ◽

Sharifah Rafidah Wan Alwi ◽

Zainuddin Abdul Manan ◽

Khaidzir Hamzah ◽

Jiří Jaromír Klemeš

Keyword(s):

Energy Savings ◽

Process Integration ◽

Data Extraction ◽

Cost Effective ◽

Energy System ◽

Optimal Size ◽

Integrated Energy Systems ◽

Heating And Cooling ◽

Analysis Technique ◽

Utility Distribution

Research and development on integrated energy systems such as cogeneration and trigeneration to improve the efficiency of thermal energy as well as fuel utilisation have been a key focus of attention by researchers. Total Site Utility Integration is an established methodology for the synergy and integration of utility recovery among multiple processes. However, Total Site Cooling, Heating and Power (TSCHP) integration methods involving trigeneration systems for industrial plants have been much less emphasised. This paper proposes a novel methodology for developing an insight-based numerical Pinch Analysis technique to simultaneously target the minimum cooling, heating and power requirements for a total site energy system. It enables the design of an integrated centralised trigeneration system involving several industrial sites generating the same utilities. The new method is called the Trigeneration System Cascade Analysis (TriGenSCA). The procedure for TriGenSCA involves data extraction, constructions of a Problem Table Algorithm (PTA), Multiple Utility Problem Table Algorithm (MU PTA), Total Site Problem Table Algorithm (TS PTA) and estimation of energy sources by a trigeneration system followed by construction of TriGenSCA, Trigeneration Storage Cascade Table (TriGenSCT) and construction of a Total Site Utility Distribution (TSUD) Table. The TriGenSCA tool is vital for users to determine the optimal size of utilities for generating power, heating and cooling in a trigeneration power plant. Based on the case study, the base fuel source for power, heating and cooling is nuclear energy with a demand load of 72 GWh/d supplied by 10.8 t of Uranium-235. Comparison between conventional PWR producing power, heating and cooling seperately, and trigeneration PWR system with and without integration have been made. The results prove that PWR as a trigeneration system is the most cost-effective, enabling 28% and 17% energy savings as compared to conventional PWR producing power, heating and cooling separately.

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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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Implications of converting a kraft pulp mill to a dissolving pulp operation with a hemicellulose extraction stage

TAPPI Journal ◽

10.32964/tj12.2.29 ◽

2013 ◽

Vol 12 (2) ◽

pp. 29-38 ◽

Cited By ~ 9

Author(s):

ENRIQUE MATEOS-ESPEJEL ◽

THEODORE RADIOTIS ◽

NACEUR JEMAA

Keyword(s):

Kraft Pulp ◽

Paper Industry ◽

Production Capacity ◽

Pulp Mill ◽

Dissolving Pulp ◽

Operating Conditions ◽

Pulp Mills ◽

Kraft Pulp Mill ◽

Efficiency Measures ◽

Recovery Boiler

Global demand for dissolving pulp has been increasing at a remarkable pace over the last few years. A shortage in cotton and the expansion of the textile, hygiene, and health product markets are behind this booming demand. The Canadian pulp and paper industry has entered these markets by converting several paper-grade pulp mills to dissolving pulp producers. In the kraft process, part of the hemicellulose remains with the pulp after cooking and the rest is burnt in the recovery boiler to produce energy. In dissolving pulp mills, most of the hemicellulose must be removed from the wood chips in a pre-hydrolysis stage before pulping. Hemicellulose hydrolysis and its subsequent extraction will affect energy and chemical balances. In addition, the new operation will require large capital expenditures. The objective of this work was to study the conversion of a kraft pulp mill to a dissolving pulp operation and the extraction of hemicelluloses from the process. The effects of hemicellulose extraction on mill energy balance, equipment requirements, and new operating conditions were analyzed. Computer simulations of the process and thermal pinch analysis were used. The existing bottlenecks (digesters, lime kiln, and recovery boiler) to increasing the dissolving pulp production capacity were identified before and after the conversion. In addition, energy efficiency measures were identified to decrease the energy consumption of the new process.

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Concentrated sulfuric acid production from non-condensable gases and its effect on alkali and sulfur balances in pulp mills

Nordic Pulp & Paper Research Journal ◽

10.1515/npprj-2020-0049 ◽

2020 ◽

Vol 0 (0) ◽

Author(s):

Andrés Mahecha-Botero ◽

Rohan Bandekar ◽

Isabel M. C. L. Sêco ◽

Igor Aksenov ◽

C. Guy Cooper ◽

...

Keyword(s):

Sulfuric Acid ◽

Paper Industry ◽

Production Capacity ◽

Pulp Mill ◽

Chemical Recovery ◽

Pulp Mills ◽

Process Technology ◽

Process Improvements ◽

Sulfuric Acid Production ◽

Technical Features

AbstractThe pulp and paper industry often encounters challenges that require process improvements to remain competitive. These challenges may include the requirement to meet more stringent environmental regulations, stricter energy policies, or the need to improve product quality, increase production capacity and profitability. As a result, the pulp mills of today have to focus on becoming more efficient by possessing an effective chemical recovery system and reducing chemical losses. The high degree of closure is beneficial for environment, water consumption and mill economy but can upset the Na/S balance and increase the build-up of non-process elements in the system. Installing an acid plant to convert the sulfur containing Non Condensable Gases (NCG) into sulfuric acid will eliminate the NCG as a sulfur input to the recovery cycle, eliminate purchases of sulfuric acid, reduce caustic purchases, and produce additional steam that will positively impact the mill’s heat balance. This paper provides an overview of the OptimumAcid™ technology required to produce sulfuric acid in a pulp mill from NCG, presents some of the unique challenges related to feed variability, and discusses some of the technical features of NORAM’s sulfuric acid OptimumAcid™ process technology and equipment.

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Mineral/microfibrillated cellulose composite materials: High performance products, applications, and product forms

TAPPI Journal ◽

10.32964/tj17.09.507 ◽

2018 ◽

Vol 17 (09) ◽

pp. 507-515 ◽

Cited By ~ 1

Author(s):

David Skuse ◽

Mark Windebank ◽

Tafadzwa Motsi ◽

Guillaume Tellier

Keyword(s):

Composite Materials ◽

High Performance ◽

Aqueous Suspension ◽

Production Capacity ◽

Cost Savings ◽

Cost Effective ◽

New Materials ◽

Wet Strength ◽

Product Forms ◽

Cellulose Composite

When pulp and minerals are co-processed in aqueous suspension, the mineral acts as a grinding aid, facilitating the cost-effective production of fibrils. Furthermore, this processing allows the utilization of robust industrial milling equipment. There are 40000 dry metric tons of mineral/microfbrillated (MFC) cellulose composite production capacity in operation across three continents. These mineral/MFC products have been cleared by the FDA for use as a dry and wet strength agent in coated and uncoated food contact paper and paperboard applications. We have previously reported that use of these mineral/MFC composite materials in fiber-based applications allows generally improved wet and dry mechanical properties with concomitant opportunities for cost savings, property improvements, or grade developments and that the materials can be prepared using a range of fibers and minerals. Here, we: (1) report the development of new products that offer improved performance, (2) compare the performance of these new materials with that of a range of other nanocellulosic material types, (3) illustrate the performance of these new materials in reinforcement (paper and board) and viscosification applications, and (4) discuss product form requirements for different applications.

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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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Respect for the Environment is Part of Competitiveness - Best Available Technology Applied to an Old Pulp Mill at Kaskinen

Water Science & Technology ◽

10.2166/wst.1999.0713 ◽

1999 ◽

Vol 40 (11-12) ◽

pp. 201-206

Author(s):

I. Reilama ◽

N. Ilomäki

Keyword(s):

Process Development ◽

Continuous Production ◽

Production Capacity ◽

Pulp Mill ◽

Process Technology ◽

Line Production ◽

Nutrient Emissions ◽

Best Available Technology ◽

Available Technology ◽

Process Solutions

Oy Metsä-Botnia Ab's Kaskinen mill produces ECF and TCF bleached softwood and hardwood pulp on a single continuous production line. Production capacity has been raised from 250,000 tonnes to 420,000 tonnes a year after the commission in 1977. The basic process solutions date mainly from the 1970s. However, process technology has been gradually modernised. With systematic and well-timed process development investments the mill has remained competitive and among frontrunners in terms of environmental protection. Today, Kaskinen represent the best available technology (BAT) applicable to old mills. Effluent loading in general and nutrient emissions in particular has diminished during the development projects of the mill. Comparison to other mills shows that as far as effluent emissions are concerned, Kaskinen is one of the best pulp mills in Finland and Scandinavia. In this presentation, Kaskinen is also compared to Metsä-Rauma, the first greenfield TCF mill in the world, which was started up in 1996. Kaskinen's pioneering work on TCF technology was used as a basis for process solutions in the Rauma greenfield project.

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