Impact and feasibility of a membrane pre-concentration step in kraft recovery

Emerging robust membrane systems can perform the first section of black liquor (BL) concentration by separating clean water from the black liquor stream using only mechanical pressure. By doing so, they can reduce the steam and energy required for BL concentration. Because of the high osmotic pressure of strong BL, a membrane system would not replace evaporators but would operate in series, performing the first section of BL concentration. In this work, we use a multi-effect evaporator (MEE) model to quantify the steam and energy savings associated with installing membrane systems of different sizes. When maintaining a constant BL solids throughput, we find that a pulp mill could reduce steam usage in its evaporators by up to 65%. Alternatively, a membrane system could also serve to increase BL throughput of the recovery train. We find that a membrane system capable of concentrating BL to 25% could double the BL solids throughput of a mill’s evaporators at the same steam usage. We also demonstrate that installing a membrane system before an MEE would minimally affect key operating parameters such as steam pressures and BL solids concentrations in each effect. This indicates that installing a membrane pre-concentration system would be nonintrusive to a mill’s operations.

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Addressing production bottlenecks and brownstock washer optimization via a membrane concentration system

TAPPI Journal ◽

10.32964/tj20.7.467 ◽

2021 ◽

Vol 20 (7) ◽

pp. 467-478

Author(s):

DIEGO F. RIVERA ◽

MAX KLEIMAN-LYNCH ◽

BRENT D. KELLER ◽

STEPHEN F. FRAYNE

Keyword(s):

Black Liquor ◽

Operating Cost ◽

Membrane System ◽

Wash Water ◽

Pulp Mills ◽

Membrane Systems ◽

Annual Operating Cost ◽

Production Increase ◽

The Impact ◽

Pulp Production

Advancements in membrane systems indicate that they will soon be robust enough to concentrate weak black liquor. To date, the economic impact of membrane systems on brownstock washing in kraft mills has not been studied and is necessary to understand the viability of these emerging systems and their best utilization. This study investigated the savings that a membrane system can generate related to brownstock washing. We found that evaporation costs are the primary barrier for mills seeking to increase wash water usage. Without these additional evaporation costs, we showed that our hypothetical 1000 tons/day bleached and brown pulp mills can achieve annual savings of over $1.0 MM when operating at higher dilution factors and fixed pulp production rate. We then investigated the impact of increasing pulp production on mills limited by their equipment. In washer-limited mill examples, we calculated that membrane systems can reduce the annual operating cost for a 7% production increase by 91%. Similarly, in evaporator-limited mill examples, membrane systems can reduce the annual operating cost for a 7% production increase by 86%. These results indicated that membrane systems make a production increase significantly more feasible for these equipment-limited mills.

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Biorefinery implementation for recovery debottlenecking at existing pulp mills- Part II: Techno-economic evaluation

TAPPI Journal ◽

10.32964/tj11.8.17 ◽

2012 ◽

Vol 11 (8) ◽

pp. 17-24 ◽

Cited By ~ 1

Author(s):

HAKIM GHEZZAZ ◽

LUC PELLETIER ◽

PAUL R. STUART

Keyword(s):

Cost Estimation ◽

Process Model ◽

Black Liquor ◽

Pulp Mill ◽

Value Added ◽

Economic Assessment ◽

Extraction Process ◽

Estimation Methods ◽

Precipitation Process

The evaluation and process risk assessment of (a) lignin precipitation from black liquor, and (b) the near-neutral hemicellulose pre-extraction for recovery boiler debottlenecking in an existing pulp mill is presented in Part I of this paper, which was published in the July 2012 issue of TAPPI Journal. In Part II, the economic assessment of the two biorefinery process options is presented and interpreted. A mill process model was developed using WinGEMS software and used for calculating the mass and energy balances. Investment costs, operating costs, and profitability of the two biorefinery options have been calculated using standard cost estimation methods. The results show that the two biorefinery options are profitable for the case study mill and effective at process debottlenecking. The after-tax internal rate of return (IRR) of the lignin precipitation process option was estimated to be 95%, while that of the hemicellulose pre-extraction process option was 28%. Sensitivity analysis showed that the after tax-IRR of the lignin precipitation process remains higher than that of the hemicellulose pre-extraction process option, for all changes in the selected sensitivity parameters. If we consider the after-tax IRR, as well as capital cost, as selection criteria, the results show that for the case study mill, the lignin precipitation process is more promising than the near-neutral hemicellulose pre-extraction process. However, the comparison between the two biorefinery options should include long-term evaluation criteria. The potential of high value-added products that could be produced from lignin in the case of the lignin precipitation process, or from ethanol and acetic acid in the case of the hemicellulose pre-extraction process, should also be considered in the selection of the most promising process option.

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Managing total reduced sulfur emissions at a Canadian kraft pulp mill

TAPPI Journal ◽

10.32964/tj15.4.265 ◽

2016 ◽

Vol 15 (4) ◽

pp. 265-272 ◽

Cited By ~ 1

Author(s):

ROHAN BANDEKAR ◽

JIM FREDERICK ◽

JAROSLAV STAVIK

Keyword(s):

Direct Contact ◽

Black Liquor ◽

Pulp Mill ◽

Packed Bed ◽

Average Value ◽

Emission Limit ◽

Total Reduced Sulfur ◽

Reduced Sulfur ◽

Air Ingress ◽

Solids Content

This study addresses the challenges a dissolving-grade pulp mill in Canada faced in 2014 in meeting its total reduced sulfur (TRS) gas emission limit. These emissions from the recovery boiler exit are controlled by passing the boiler exit gas through a TRS scrubber system. The mill employs a cyclonic direct contact evaporator to concentrate black liquor to firing solids content. The off-gases from the direct contact evaporator flow to the effluent gas control system that consists of a venturi scrubber, a packed bed scrubber, and a heat recovery unit. Emissions of TRS greater than the regulated limit of 15 ppm were observed for a 4-month period in 2014. The level of emissions measured during this period was significantly higher than about 12 ppm, the expected average value based on historic experience. The problem persisted from mid-June 2014 until the annual mill shutdown in October 2014. The main TRS components detected and the performance of the Teller scrubber in capturing them are examined. Other potential causes for these emissions are identified, including mechanical problems such as broken packing in the TRS packed bed scrubber, broken baffle plates in the scrubber, and cyclone evaporator leaks causing air ingress. Repairs were carried out during the mill shutdown, which eliminated the TRS emissions problem.

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Commissioning brownstock washing controls for an evaporator limited mill

TAPPI Journal ◽

10.32964/tj15.7.459 ◽

2016 ◽

Vol 15 (7) ◽

pp. 459-464

Author(s):

RICARDO SANTOS ◽

PETER HART

Keyword(s):

Control System ◽

Negative Impact ◽

Black Liquor ◽

Pulp Mill ◽

Control Program ◽

Separation Point ◽

Water Control ◽

Oxygen Delignification ◽

Percentage Points

An automated shower water control system has been implemented to reduce the volume and variability of weak black liquor being sent from the pulp mill to the evaporators. The washing controls attempt to balance the need for consistent and low soda carryover to the bleach plant with consistently high weak black liquor solids being sent to the evaporators. The washer controls were implemented on two bleachable grade hardwood lines (one with oxygen delignification, one without oxygen delignification) and one pine line. Implementation of the control program resulted in an increase in black liquor solids of 0.6 percentage points for the hardwood lines. Significant foam reduction was realized on the pine line since the pine black liquor solids were able to be consistently maintained just below the soap separation point. Low black liquor solids excursions to the evaporators were eliminated. Bleach plant carryover was stabilized and no negative impact on chemical consumption was noticed when controlling weak black liquor solids to recovery.

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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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De‐bottlenecking a pulp mill by producing biofuels from black liquor in 3 steps

ChemSusChem ◽

10.1002/cssc.202100496 ◽

2021 ◽

Author(s):

Joseph Samec ◽

Davide Di Francesco ◽

Christian Dahlstrand ◽

Joakim Löfstedt ◽

Alexander Orebom ◽

...

Keyword(s):

Black Liquor ◽

Pulp Mill

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Purification of pulp mill condensates by an adsorptive process on activated carbon

Holzforschung ◽

10.1515/hf-2018-0125 ◽

2019 ◽

Vol 73 (6) ◽

pp. 589-597 ◽

Cited By ~ 2

Author(s):

José A.F. Gamelas ◽

Sofia M. Rebola ◽

Margarita G. Evtyugina ◽

Valdemar I. Esteves ◽

Dmitry V. Evtuguin

Keyword(s):

Activated Carbon ◽

Volatile Compounds ◽

Water Cycle ◽

Black Liquor ◽

Pulp Mill ◽

Dimethyl Disulfide ◽

Pulp Mills ◽

Wide Range ◽

New Process ◽

Pseudo Second Order

Abstract In order to close the water cycle in pulp mills with condensates instead of fresh water, the malodorous/hazardous volatile compounds and colored substances have to be removed by appropriate efficient methods. In the present work, the condensate from the evaporation of black liquor (BL) from a kraft mill was purified by a batch adsorptive process by means of commercial activated carbon (AC). The effluent was found to contain a wide range of aromatic and organosulfur volatile compounds, including toluene, ethylguaicol, syringaldehyde, dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), 2,3-dimethylthiophene, benzothiol and benzothiophene derivatives. Methanol was the major volatile organic component in the condensate (201 mg l−1), which was, however, poorly adsorbed on the AC surface. Aromatics and organosulfur contaminants were adsorbed almost completely in 2–5 min at 23°C under the optimized AC load (900 mg l−1). The treatment allowed the elimination of up to 99% of the obnoxious odor, color and turbidity of the condensate. The adsorption equilibrium followed the Langmuir model and the pseudo-second-order kinetics. The new process could be incorporated in the pulp mill with relatively low additional reagent costs.

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Analysis of Pulp Mill Black Liquor for Organosulfur Compounds Using GC/Atomic Emission Detection

ENVIRONMENTAL FATE and EFFECTS of PULP and PAPER MILL EFFLUENTS ◽

10.1201/9780367812690-19 ◽

2020 ◽

pp. 195-202

Author(s):

I. Ya. Rod’ko ◽

B.F. Scott ◽

J.H. Carey

Keyword(s):

Black Liquor ◽

Pulp Mill ◽

Atomic Emission ◽

Organosulfur Compounds ◽

Atomic Emission Detection ◽

Emission Detection

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The polypeptides of rat liver nuclear envelope. II. Comparison of rat liver nuclear membrane polypeptides with those of the rough endoplasmic reticulum

Journal of Cell Science ◽

10.1242/jcs.43.1.269 ◽

1980 ◽

Vol 43 (1) ◽

pp. 269-277

Author(s):

J.C. Richardson ◽

A.H. Maddy

Keyword(s):

Endoplasmic Reticulum ◽

Rat Liver ◽

Rough Endoplasmic Reticulum ◽

Nuclear Membrane ◽

Relative Proportion ◽

Membrane System ◽

Membrane Systems ◽

Nuclear Membranes ◽

Cytoplasmic Surface ◽

Triton X

Nuclear envelopes are separated into pore-lamina and membrane sub-fractions by extraction in 2.0% Triton X-100 followed by pelleting of the pore-laminae. The polypeptides of these subfractions are then compared with those from isolated rough endoplasmic reticulum. The dispositions of individual polypeptides in the cytoplasmic surface of nuclear envelopes and rought endoplasmic reticulum were studied by lactoperoxidase-catalysed iodination. These studies show that although the nuclear membranes exhibit several homologies with the Triton-soluble polypeptides of the rough endoplasmic reticulum the relative proportion of individual polypeptides within the two systems are very largely different. The cytoplasmic surfaces of the 2 membrane systems show only 2 obvious homologies at 105 000 and 15 000 mol. wt and the overall impression is that, at least in rat liver, the outer nuclear membrane is very substantially differentiated from rough endoplasmic reticulum. It is concluded that the nuclear membranes may not be regarded as a mere continuum of the endoplasmic reticulum, but should be seen as a highly specialized membrane system in their own right.

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