What is sulphate pulping process?
The kraft process (also known as kraft pulping or sulfate process) is a process for conversion of wood into wood pulp, which consists of almost pure cellulose fibers, the main component of paper. It is the dominant method for producing paper.
Which raw material is used in sulfite process?
The first sulphite pulping plant was built in Sweden in 1874. This pulping method is low in cost and low in production cost because the main chemical raw materials used are sulfur and limestone. The resulting pulp is lighter in color and can be used directly to produce many varieties of paper without bleaching.
What is Sulphited pulp?
The sulfite pulping liquid is prepared by absorbing sulfur dioxide (prepared by burning sulfur with a controlled excess of oxygen and quickly cooling the product gas to around 200°C to prevent further oxidation to sulfur trioxide) into different bases. The reactions are: (1) (2)
What is sulfite process?
: an alkaline process for making pulp from wood chips in which the cooking liquor contains chiefly sodium hydroxide together with considerable amounts of sodium sulfide derived from the reduction of sodium sulfate added during the recovery process.
What does sulfite paper mean?
Sulphite is a process that extracts the lignin from wood chips and produces pure cellulose fibers. This means that sulphite paper is a smooth, white and inexpensive drawing paper that is perfect in any art room or home-school environment.
What is the difference between construction paper and sulphite paper?
Sulphite Paper is also referred to as construction paper, but don’t be confused. It’s not the cheap construction paper found in craft stores. Sulphite is a process that extracts the lignin from wood chips and produces pure cellulose fibers.
What is sulfite paper used for?
Sulfite pulp remains an important commodity, especially for specialty papers and as a source of cellulose for non-paper applications. It is used to make fine paper, tissue, glassine. and to add strength to newsprint.
What is the range of pH required in acid sulfite process?
1.5-2
What is the range of pH required in Acid sulfite process? Explanation: The acid sulfite process uses a cooking liquor that is strongly acidic (pH 1.5-2, and, therefore, has a preponderance of free SO2 in solution), with a pulping temp. of 125-145 degree celcius.
What is the temperature condition of digester in sulfite process?
iii) For Sulfate process, digestion time is 2-5hrs at temperature 170-176°C and pressure 660-925kPa whereas for Sulfite process, time required is 6-12hrs at temperature 125-160°C and pressure 620-755kPa.
What are sulphites?
Sulphites are naturally occurring minerals that have a long history of use in foods. They naturally occur in some foods but are widely used as a food additive to prevent microbial spoilage and preserve colour. Cordials, dried fruit, sausages and wine are some of the foods that commonly contain sulphites.
What are the chemicals used in the pulp digestion process?
Chemical wood pulping involves the extraction of cellulose from wood by dissolving the lignin that binds the cellulose fibers together. The 4 processes principally used in chemical pulping are kraft, sulfite, neutral sulfite semichemical (NSSC), and soda.
What is spent cooking liquor from sulfite pulping called?
The spent cooking liquor from sulfite pulping is usually called brown liquor, but the terms red liquor, thick liquor and sulfite liquor are also used (compared to black liquor in the kraft process). Pulp washers, using countercurrent flow, remove the spent cooking chemicals and degraded lignin and hemicellulose.
What are the processes used in chemical pulping?
The 4 processes principally used in chemical pulping are kraft, sulfite, neutral sulfite semichemical (NSSC), and soda. The first 3 display the greatest potential for causing air pollution.
What are the intermediates in the sulfite pulping process?
Most of the intermediates involved in delignification in sulfite pulping are resonance-stabilized carbocations formed either by protonation of carbon-carbon double bonds or acidic cleavage of ether bonds which connect many of the constituents of lignin.
How long is the pulp in contact with the chemicals?
The pulp is in contact with the pulping chemicals for 4 to 14 hours and at temperatures ranging from 130 to 160 °C (266 to 320 °F ), again depending on the chemicals used.