Black liquor properties and evaporation Fundamentals of Industrial

Black liquor properties and evaporation Fundamentals of Industrial Energy Engineering EEN-E 3001 Presentation by: Juan Arroyo Asensio & Esther Oladele

Learning objectives. What is black liquor ? How is black liquor obtained? Composition of black liquor The use and burning of black liquor Properties of black liquor Purpose of evaporation Evaporation Unit Evaporation Process Improvement of evaporators 13. 2. 2022 2

Black liquor properties 13. 2. 2022 3

Quick recap from last lecture White Liquor - Na. OH + Na 2 S - Dissolves & fragment lignin - Peeling & chain scisson of polysaccharides 13. 2. 2022 4

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Different names of Black liquor. Between the washing plant and the recovery boiler, black liquor goes by several different names depending on its dry solid concentration or location in the process: - Weak black liquor or washing liquor - Burn liquor - Feed liquor - Firing liquor - Intermediate liquor - Strong black liquor - Heavy black liquor 13. 2. 2022 6

Birch black liquor composition. 0% 1% 5% 1% 9% Lignin saccharine acids(carbohydrates, lignin) Aliphatic acids (lignin, carbohydrates) 4% 38% 2% Fat and resinous acids (extractives) Polysaccharides(celluloce and hemicelluloces) 3% Na. OH Na. HS Na 2 CO 3 and K 2 CO 3 Na 2 SO 4 15% Na 2 S 2 O and Na 2 S Na. Cl others(Si, Ca, Mn, Mg etc) 23% 13. 2. 2022 7

The use and burning of black liquor - Separate organic and inorganic matter contained within the liquor - Recover heat value in the organic matter - Rodium and sulfur chemicals recovery 13. 2. 2022 8

Properties of black liquor - Density Viscosity Thermal conductivity Specific heat Boiling point rise Surface tension. 13. 2. 2022 9

Evaporation 13. 2. 2022 10

Purpose of evaporation Source: https: //www. mdpi. com/1996 -1073/5/7/2288 Chemical recovery Line: • Recovery of unreacted chemical • Use the heat energy from wood substances Evaporation process: • High solid content on the liquor • Liquor as clean as possible (Byproducts) 13. 2. 2022 11

Evaporation Unit Source: https: //lcicorp. com/en/articles/selecting-evaporators-for-process-applications 13. 2. 2022 12

Evaporation Unit: Types Rising Film (RF) • Liquor is fed on the bottom • Liquor vapor pulls up the stream • Condensation of vapour occurs on the outside of the tubes • Needs high ∆T • Low solid content (High viscosity) 13. 2. 2022 13

Evaporation Unit: Types Falling Film (FF) • Plate heat exchanger are used (Lamella) • Condensation of vapour is on the inside of the plates. • Liquor is fed on the top (Circulation pump) • Some RF has been modernized to FF 13. 2. 2022 14

Evaporation Process Source: https: //www. convergencetraining. com/blackliquor-evaporators-introduction. html By-products • Soap Two-stages process Precipitation 30 -50 kg/t pulp to none • Methanol Condensed Burned for energy or liquified • Turpentine Separated in cooking gases 8 -12 kg/t pulp 13. 2. 2022 15

Evaporation Process: Types • • Multiple-effect evaporators Vapor compression evaporators Supplied energy is used several • Used when steam is not available times. • It compresses the stream Liquor is evaporated in counterreleased & feeds it back current to steam. • Steam compression Number of units: 5 – 7 Ejector 5 -effect plant: Compressor 550 k. J/kg of steam. Blower • Blower limited to pre-evaporation/ used in series 13. 2. 2022 16

Improvement on The Process Concentrators and preheaters Liquor Heat Treatment • Increase temperatures. • High temperature (190 ºC) for 20 minutes. • Decrease the viscosity of the solid & increase solid content. • Decrease viscosity. • Use of medium-pressure steam. • Possibility to use of low-pressure steam. • Stores in pressurized tanks. • Possibility to use non-pressurized storage 13. 2. 2022 17