What is the pH of black liquor?
What is the pH of black liquor?
pH 13 to 14
The pH of black liquor is rather high (pH 13 to 14), and the phenolic groups on lignin molecules are ionized, making the lignin soluble in a water solution.
What is the relation between viscosity and solid percentage of black liquor?
The viscosity rises rapidly with concentration above 50%, with softwood black liquors being more viscous than hardwood black liquors. Black liquor is usually fired at 65%–70% solids content.
What is BPR in evaporator?
• BL boils at temps above water boiling point. • Boiling point rise (BPR) increases with solids.
Is black liquor harmful to humans?
Inhalation: Inhalation may cause respiratory tract irritation, difficulty breathing, and respiratory tract damage. Symptoms may include coughing, burning, difficulty breathing and shortness of breath. Remove exposed person to fresh air.
How is black liquor recovered?
The black liquor is concentrated in several stages through evaporation, by heating with steam, until it consists of approximately 66% solids. The concentrated black liquor is then burned in the recovery boiler.
What is evaporator efficiency?
Thermal efficiency of evaporators The measure of thermal efficiency of an evaporator train is called the steam economy (unit of water evaporated per unit of steam used) and the steam economy is directly related to the number of thermal effect in the train. Modern evaporators typically have 6 or 7 thermal effects.
Is there a black liquor?
The black liquor is an aqueous solution of lignin residues, hemicellulose, and the inorganic chemicals used in the process. Cellulose and hemicellulose is degraded to aliphatic carboxylic acid soaps and hemicellulose fragments. The extractives gives tall oil soap and crude turpentine.
How is black liquor used?
Pulp mills have used black liquor as an energy source since the 1930s. At pulp mills today, black liquor is burned in so-called Tomlinson recovery boilers to generate steam and recover pulping chemicals for re-use.
What is black liquor used for?
What is Black Liquor? “Black Liquor” is a by-product of pulp from mills that make products from trees, such as paper. It is currently used to recover cooking chemicals and produce high-pressure steam used in the pulp and paper-making process.
How to calculate the specific gravity of black liquor?
Black Liquor Specific Gravity •Important for performance calculations •ºBaumé (hydrometer up to 50% solids), must be corrected for temperature SG of BL @ 60ºF / water @ 60ºF = 145/(145 – ºBé) •Solid content inferred from ºBaumé, but correlation changes with wood species! Slide 16 Black Liquor Density Correlations •Correlation for ≤50% BLS, T ≤100ºC
What is the solids content of black liquor?
Black liquor is evaporated from 15–18% to 60–85% solids content through a series of five to seven evaporators with multiple effects. The first evaporator effect is fed by low- or medium-pressure steam.
How is the evaporator capacity of black liquor affected?
•Evaporator capacity can be affected by changes in viscosity, e.g. wood species –Viscosity up 5 fold, U value down 50% Slide 22 Black Liquor Boiling Point Rise •BL boils at temps above water boiling point •Boiling point rise (BPR) increases with solids •BPR depends on inorganic content of liquor
What are the thermal properties of black liquor?
Black Liquor Density Correlations •Correlation for ≤50% BLS, T ≤100ºC ρ, g/cm3 = 1.007 + 0.006*(%S) – 0.000495* (TºC) •Ex: 15% BLS, 82oC (180oF) > 1.06 g/cm3 •Ex: 49% BLS, 93oC (200oF) > 1.26 g/cm3 •Non-linear behavior at high solids •Extrapolation to firing conditions ± 10% 9 Slide 17 Black Liquor Thermal Properties