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Solubility of Sodium Salts in Kraft Black Liquor and the Impact on Evaporator Fouling.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Solubility of Sodium Salts in Kraft Black Liquor and the Impact on Evaporator Fouling./
作者:	Khafhafera, Ahmed Naser.
面頁冊數:	1 online resource (166 pages)
附註:	Source: Dissertations Abstracts International, Volume: 84-09, Section: B.
Contained By:	Dissertations Abstracts International84-09B.
標題:	Engineering. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30242981click for full text (PQDT)
ISBN:	9798377616122

Solubility of Sodium Salts in Kraft Black Liquor and the Impact on Evaporator Fouling.
Khafhafera, Ahmed Naser.

Solubility of Sodium Salts in Kraft Black Liquor and the Impact on Evaporator Fouling. - 1 online resource (166 pages)

Source: Dissertations Abstracts International, Volume: 84-09, Section: B.

Thesis (Ph.D.)--University of Toronto (Canada), 2023.

Includes bibliographical references

The evaporation of black liquor is a key step in the chemical recovery cycle of kraft pulp mills. Black liquor is concentrated stepwise by evaporating water in multiple effects evaporators (MEE). The majority of the scaling and fouling instances during black liquor evaporation are attributed to sodium salts. The focus of this thesis is to obtain the necessary solubility data for sodium oxalate and sodium carbonate-sodium sulfate salts and thus generate empirical models for sodium salt solubility that can be applied in mills to help reduce evaporator scaling. Sodium oxalate solubility was studied in the temperature range of 50 °C to 140 °C and a dry solids range of 14% to 70% dry solids. Four mill liquors were studied for the work done below 100 °C, and sodium oxalate solubility was not found to be liquor-dependent but rather depended only on the concentration of sodium, concentration of oxalate, and temperature. Two different empirical formulas were developed for solubility below 100 °C and solubility above 100 °C. These formulas were applied by a mill with sodium oxalate scaling in several of their evaporator effects. Double salts of sodium carbonate and sodium sulfate precipitate in the evaporation sets of all kraft pulp mills. Most of the solubility work focused on the transitions between the different salt species and the solubility of the carbonate-rich salts, about which there is relatively little data in the present literature. Empirical formulas were developed for use by mills and were utilized in the following studies with electrostatic precipitator (ESP) ash.Electrostatic precipitator (ESP) ash is used by the pulp and paper industry in two different ways to try and reduce sodium salt scaling. The first is to dissolve it in black liquor so that a sulfate-rich double salt precipitates first rather than carbonate-rich salts, which causes more severe scaling. The second approach is to add the ash above the solubility limit to increase the crystal surface area for precipitating salts to precipitate onto. The experiments showed that ash added below the solubility limit dissolves quickly, reaching saturation as fast as 10 min. It also found that ash, when added to carbonate-rich black liquor above the solubility limit, remains as burkeite and sodium sulfate and, within 24 h, does not undergo dissolution and re-precipitation to a carbonate-rich salt. This may help explain the varied success of using precipitator ash to reduce sodium salt scaling in kraft black liquor evaporators.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798377616122Subjects--Topical Terms:

586835
Engineering.
Subjects--Index Terms:

Sodium saltsIndex Terms--Genre/Form:

542853
Electronic books.

Solubility of Sodium Salts in Kraft Black Liquor and the Impact on Evaporator Fouling.
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520 $a The evaporation of black liquor is a key step in the chemical recovery cycle of kraft pulp mills. Black liquor is concentrated stepwise by evaporating water in multiple effects evaporators (MEE). The majority of the scaling and fouling instances during black liquor evaporation are attributed to sodium salts. The focus of this thesis is to obtain the necessary solubility data for sodium oxalate and sodium carbonate-sodium sulfate salts and thus generate empirical models for sodium salt solubility that can be applied in mills to help reduce evaporator scaling. Sodium oxalate solubility was studied in the temperature range of 50 °C to 140 °C and a dry solids range of 14% to 70% dry solids. Four mill liquors were studied for the work done below 100 °C, and sodium oxalate solubility was not found to be liquor-dependent but rather depended only on the concentration of sodium, concentration of oxalate, and temperature. Two different empirical formulas were developed for solubility below 100 °C and solubility above 100 °C. These formulas were applied by a mill with sodium oxalate scaling in several of their evaporator effects. Double salts of sodium carbonate and sodium sulfate precipitate in the evaporation sets of all kraft pulp mills. Most of the solubility work focused on the transitions between the different salt species and the solubility of the carbonate-rich salts, about which there is relatively little data in the present literature. Empirical formulas were developed for use by mills and were utilized in the following studies with electrostatic precipitator (ESP) ash.Electrostatic precipitator (ESP) ash is used by the pulp and paper industry in two different ways to try and reduce sodium salt scaling. The first is to dissolve it in black liquor so that a sulfate-rich double salt precipitates first rather than carbonate-rich salts, which causes more severe scaling. The second approach is to add the ash above the solubility limit to increase the crystal surface area for precipitating salts to precipitate onto. The experiments showed that ash added below the solubility limit dissolves quickly, reaching saturation as fast as 10 min. It also found that ash, when added to carbonate-rich black liquor above the solubility limit, remains as burkeite and sodium sulfate and, within 24 h, does not undergo dissolution and re-precipitation to a carbonate-rich salt. This may help explain the varied success of using precipitator ash to reduce sodium salt scaling in kraft black liquor evaporators.
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650 4 $a Thermodynamics. $3 517304
650 4 $a Chemical engineering. $3 560457
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653 $a Evaporator fouling
653 $a Temperature range
653 $a Electrostatic precipitator
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