What is chemical recovery in paper industry?

What is chemical recovery in paper industry?

THE RECOVERY PROCESS The process has three main functions: i) minimizing the environmental impact of waste material (black liquor) from the pulping process; ii) recycling pulping chemicals, NaOH and Na2S; and iii) co-generating steam and power.

What is chemical recovery process?

The chemical recovery process involves concentrating weak black liquor, combusting organic compounds, reducing inorganic compounds, and reconstituting the cooking liquor.

What chemicals are used in the paper and pulp industry?

The chemicals used are (1) sulfite salts with an excess of sulfur dioxide and (2) caustic soda and sodium sulfide (the kraft process). The lignin of the wood is made soluble, and the fibres separate as whole fibres. Further purification can be accomplished by bleaching.

What are the chemicals used in the pulp digestion process?

The kraft pulping process (see Figure 10.2-1) involves the digesting of wood chips at elevated temperature and pressure in “white liquor”, which is a water solution of sodium sulfide and sodium hydroxide. The white liquor chemically dissolves the lignin that binds the cellulose fibers together.

How do you bleach pulp?

Alkaline hydrogen peroxide is the most commonly used bleaching agent for mechanical pulp. The amount of base such as sodium hydroxide is less than that used in bleaching chemical pulps and the temperatures are lower.

What is the technical difference between sulfate kraft process and sulfite process?

What is the technical difference between Sulfate(Kraft) Process and Sulfite Process? Ans: i)Sulfate process is an alkaline process whereasthe Sulfite process is an acidicprocess. ii) The pulp has to be bleached more in the Sulfate Process as compared to the Sulfite process.

What is the chemical process of making paper?

Paper makers must remove the lignin from the wood pulp. To accomplish this, one of the main chemical reactions used in industry is the Kraft process, in which wood chips are combined with a mixture of sodium hydroxide and sodium sulfide in water at high temperature and pressure.

How many chemicals are used in paper making process?

3000
While there are about 3000 or so different types of chemicals which “can be used” in papermaking, in practice only about 200 individual chemicals are typically used, each satisfying a specific need.

How many chemicals and elements are used in the paper making process?

While there are about 3000 or so different types of chemicals which “can be used” in papermaking, in practice only about 200 individual chemicals are typically used, each satisfying a specific need.

What are some chemical reactions used in the manufacture of paper?

What is bleached chemical pulp?

Pulp bleaching. Elemental Chlorine (EC) bleaching is the traditional method for bleaching pulp, using chlorine gas (elemental chlorine). This process produces large amounts of toxic chemical compounds called dioxins and furans.

What is the name of the chemical removed from paper pulp which then allows paper to be bleached white?

Chlorine dioxide (ECF technology) currently is the most important bleaching method worldwide. About 95% of all bleached Kraft pulp is made using chlorine dioxide in ECF bleaching sequences.

Why do we need to recover chemicals from pulp and paper?

With today’s increasingly high energy and chemical costs and stringent environmental regulations, the need for improved recovery of chemicals from the pulp and paper making process has become a critical economic factor in the industry.

What is the chemical recovery process in pulp mill?

The chemical recovery process dictates the quality and quantity of the white liquor, which in turn, limits pulp production and the profitability of the kraft pulp mill. There are numerous ways in which the economics, energy efficiency, and environmental protection associated with the recovery process can be improved.

What are the objectives of kraft pulping and recovery?

Kraft Pulping and Recovery: Overall Objectives •Chemical convert wood into cellulosic pulp •High quality, strong pulp for papermaking •Operate safely •Minimize impacts on air and water •Satisfy customer needs –Maximum product quality •Minimize cost Kraft Pulping Objectives •Use chemicals, heat, pressure to liberate fibers. •Operate safely.

What affects the quality of pulp produced by kraft mills?

The reliability and efficiency of recovery boilers, evaporators, causticizing plants and lime kilns have a direct impact on the quantity and quality of white liquor, and ultimately the quantity and quality of pulp produced by kraft mills.