A practical approach to eliminating rapid sodium carbonate - sodium sulfate scaling in black liquor concentrators

TAPPI Journal ◽  
2015 ◽  
Vol 14 (7) ◽  
pp. 431-437
Author(s):  
W.J. (JIM) FREDERICK ◽  
DANIEL D. EUHUS
Keyword(s):  
Sodium Carbonate ◽  
Sodium Sulfate ◽  
Black Liquor ◽  
Double Salt ◽  
Practical Approach ◽  
Solution Design ◽  
And Behavior

Black liquor concentrators perform as crystallizers as well as evaporators, producing up to 200 kg of sodium carbonate - sodium sulfate double salt (Na2CO3+Na2SO4) crystals per o.d. metric ton of pulp produced. One of these salts, sodium sulfate dicarbonate, rapidly fouls many concentrators as it crystallizes from solution. Design and operation of black liquor concentrators to manage its crystallization can eliminate or substantially reduce sodium sulfate dicarbonate scaling. Older equipment installed before sodium sulfate dicarbonate was discovered in 2002 would benefit the most. This paper explores options for reducing rapid sodium sulfate dicarbonate scaling in black liquor concentrators by applying today’s knowledge of sodium sulfate dicarbonate crystallization characteristics and behavior during crystallizing evaporation.

Evaporation of Na2CO3-Na2SO4 solutions: A method to evaluate the distribution between bulk and surface crystallization

TAPPI Journal ◽  
2011 ◽  
Vol 10 (3) ◽  
pp. 17-24 ◽  
Author(s):  
MATHIAS GOURDON ◽  
LARS OLAUSSON ◽  
LENNART VAMLING
Keyword(s):  
Heat Transfer ◽  
Sodium Carbonate ◽  
Sodium Sulfate ◽  
Crystallization Process ◽  
Black Liquor ◽  
Crystallization Rate ◽  
Bulk Solution ◽  
Surface Crystallization ◽  
Falling Film ◽  
Bulk Crystals

Precipitation of sodium salts in black liquor evaporators causes problems by forming scales on the evaporator surface, reducing heat transfer and cleaning intervals. Most problems are connected with the crystallization of sodium carbonate and sodium sulfate. As the solubility of these salts is exceeded, a crystal mass must form somewhere. Crystallization can occur either in the bulk solution, on the heat transfer surface, or on other surfaces. It is always desirable to create bulk crystals. If crystals form and remain on the surfaces, a layer of scales will build up with time. A method for estimating the distribution of crystal masses between the bulk and on surfaces has been developed in this work. The method is primarily based on inline density measurements combined with inline measurements of the system’s water mass. It has been applied to aqueous solution of sodium carbonate and sodium sulfate in a research black liquor falling film evaporator. Experiments have proven that the method gives valuable information on the crystallization process. It shows where crystals are formed during primary nucleation, as well as during the subsequent continuous crystallization. In an industrial black liquor evaporator, the metastable limit can be passed if it is operated under non-steady-state conditions. During evaporation, upon passing the metastable limit, the experiments showed that the surface crystallization is as high as or higher than the bulk crystallization. During the subsequent crystallization process, when concentration is further increased, the crystallization rate is higher in the bulk solution than on the surfaces.

Sodium salt scaling in black liquor evaporators and the effects of the addition of tall oil brine

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Erik Karlsson ◽  
Anders Åkesjö
Keyword(s):  
Sodium Carbonate ◽  
Sodium Salt ◽  
Black Liquor ◽  
Sodium Sulphate ◽  
Salt Solutions ◽  
Tall Oil ◽  
Sulphate Content ◽  
Inhibition Effect ◽  
Salt Scaling ◽  
Primary Nucleation

AbstractSodium salt scaling, i. e. the formation of doubles salts comprised of sodium, carbonate and sulphate on the heat transfer surfaces, is a common problem that occurs during black liquor evaporation. In this study, experimental results are presented that provide new insights into the formation and composition of such scales and how they are influenced by the addition of tall oil brine. It was found that increased content of sodium carbonate and sodium sulphate in the black liquor increased scaling, while the ratio between carbonate and sulphate had a lesser influence than reported in other studies. Black liquor created loose clay-like scales comprised of aggregated crystals and black liquor, whereas salt solutions created hard mineral-like scales. The scales formed by both the black liquor and the salt solution showed a tendency to fall off during formation after primary nucleation. It was also found that both tall oil soap and alkalized tall oil brine could inhibit the formation of scales. The inhibition effect is stronger if adding the soap or brine just before scaling starts, but also depends on the amount added, the sodium carbonate and sodium sulphate content in the liquor as well as other factors.

scholarly journals Influence of sodium carbonate addition on weight loss of bagasse alkaline black liquor during pyrolysis

BioResources ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. 2428-2441
Author(s):  
Xusheng Li ◽  
Jinlong Wang ◽  
Derong Yan ◽  
Yongjun Yin ◽  
Shuangfei Wang
Keyword(s):  
Activation Energy ◽  
Weight Loss ◽  
Sodium Carbonate ◽  
Black Liquor ◽  
Reduction Reaction ◽  
Loss Ratio ◽  
N2 Atmosphere ◽  
Microscopic Morphology ◽  
Weight Loss Ratio

To understand the effects and the mechanism of sodium carbonate (Na2CO3) addition on the bagasse alkaline black liquor (BABL) pyrolysis, the reaction variables such as temperature, heating rate, and amount of Na2CO3 addition into BABL-solids were investigated under N2 atmosphere from 50 °C to 1000 °C by thermogravimetic analysis (TGA). Scanning electron microscopy (SEM) and the Coats–Redfern method (CRM) were employed for surface microscopic morphology observations and kinetic analysis, respectively. The results showed that Na2CO3 plays an inhibiting and promoting role during devolatilization (200 °C to 650 °C) and the reduction stages (650 °C to 1000 °C), respectively. Adding Na2CO3 into BABL-solids tends to increase the thickness of the salt layer covering the BABL-solids surface, which increases the activation energy and reduces the weight loss ratio of BABL-solids pyrolysis within 200 °C to 650 °C. Adding Na2CO3 into the BABL-solids tends to increase the number of alkaline compounds or the active site of the reduction reaction, which reduces the activation energy and increases the weight loss ratio of BABL-solids pyrolysis within 650 °C to 1000 °C. The role of Na2CO3 as an additive could be well understood by studying the influence mechanism of Na2CO3 on BABL-solids pyrolysis.

scholarly journals Dephosphorization Reaction by Sodium Carbonate and Sodium Sulfate

1979 ◽  
Vol 65 (13) ◽  
pp. 1838-1847 ◽  
Author(s):  
Ryo INOUE ◽  
Hideaki SUITO
Keyword(s):  
Sodium Carbonate ◽  
Sodium Sulfate

scholarly journals Alkali-Activated Hybrid Cements Based on Fly Ash and Construction and Demolition Wastes Using Sodium Sulfate and Sodium Carbonate

Molecules ◽  
2021 ◽  
Vol 26 (24) ◽  
pp. 7572
Author(s):  
William Valencia-Saavedra ◽  
Rafael Robayo-Salazar ◽  
Ruby Mejía de Gutiérrez
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Portland Cement ◽  
Sodium Carbonate ◽  
Sodium Sulfate ◽  
Room Temperature ◽  
Ordinary Portland Cement ◽  
Mechanical Performance ◽  
Construction And Demolition Wastes ◽  
Alkali Activated

This article demonstrates the possibility of producing alkali-activated hybrid cements based on fly ash (FA), and construction and demolition wastes (concrete waste, COW; ceramic waste, CEW; and masonry waste, MAW) using sodium sulfate (Na2SO4) (2–6%) and sodium carbonate (Na2CO3) (5–10%) as activators. From a mixture of COW, CEW, and MAW in equal proportions (33.33%), a new precursor called CDW was generated. The precursors were mixed with ordinary Portland cement (OPC) (10–30%). Curing of the materials was performed at room temperature (25 °C). The hybrid cements activated with Na2SO4 reached compressive strengths of up to 31 MPa at 28 days of curing, and the hybrid cements activated with Na2CO3 yielded compressive strengths of up to 22 MPa. Based on their mechanical performance, the optimal mixtures were selected: FA/30OPC-4%Na2SO4, CDW/30OPC-4%Na2SO4, FA/30OPC-10%Na2CO3, and CDW/30OPC-10%Na2CO3. At prolonged ages (180 days), these mixtures reached compressive strength values similar to those reported for pastes based on 100% OPC. A notable advantage is the reduction of the heat of the reaction, which can be reduced by up to 10 times relative to that reported for the hydration of Portland cement. These results show the feasibility of manufacturing alkaline-activated hybrid cements using alternative activators with a lower environmental impact.

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