Brief Overview of Pulp & Paper Sector
The Indian paper industry accounts for about 3.7% of the world’s production of paper. The industry employs more than 0.5 million people directly, and 1.5 million people indirectly. Most paper mills have been in operation for a long time, with their technology spectrum ranging from the oldest to the most modern equipment. Indian paper industry is a de-licensed sector and 100% FDI inflow is allowed on the automatic route. The sector attracted 54.93 million US dollar FDI investment in FY 2019. The industry structure comprises of more than 861 paper units, with an installed capacity of nearly 27.15 million tonnes out of which 4.72 million tonnes are lying idle. As of date, around 526 mills are in operation with a total operating capacity of around 87%. Total production for the year of 2019-20 stood at 20.614 exhibiting an increase of 6.4% on YoY basis.
The paper industry is broadly classified into three segments namely Writing & Printing (W&P), Newsprint and Paperboard & Industrial Packaging (Paperboard). Paperboard is the largest segment, accounting for 45% of total domestic paper demand, followed by W &P (35%) and Newsprint (20%). The mills use a variety of raw materials, viz., wood, bamboo, recycled Fiber, bagasse, wheat straw, rice husk, etc. Presently, in the total production, the share of wood, agro and wastepaper-based mills stand at 20%, 8% and 72%, respectively. During the year 2019-20, a total of 2.192 million tons of paper and paperboard was imported.In India, per capita consumption of paper is about 15.75 kg, which is far lower than the world average (57 kg. in 2019).
Manufacturing Process & Energy Consumption:
The pulp and paper industry converts fibrous raw materials into pulp, paper, and paperboard products. Pulp mills manufacture only pulp, which is then sold and transported to paper and paperboard mills. A paper and paperboard mill may purchase pulp or manufacture its own pulp in house; in the latter case, such mills are referred to as integrated mills. The major processes employed in the pulp and paper industry include raw materials preparation, pulping (chemical, semi-chemical, mechanical, and wastepaper), bleaching, chemical recovery, pulp drying, and paper making.
Currently, about 31% of the raw material requirement is met from forest product including wood and bamboo. Logs typically arrive at the mill on trucks. Debarkers are used to remove bark from logs prior to chipping, since bark is a contaminant in the pulping process. After debarking, the logs are sent to a chipping machine (most commonly a radial chipper). Agro/Agro-waste based mills use varieties of raw vmaterials including stalks, straw and sticks. Cutters/shearing machines are used for the preparation of such materials for pulping. Increasingly, most of the mills are also using some secondary fibre in the production of pulp. Wastepaper is currently the major source for secondary fibre.
The primary goals of pulping are to free fibres in wood from the lignin that binds these fibres together, and then to suspend the fibres in water into a slurry suitable for paper making. The three main processes for producing wood pulp are mechanical pulping (includes thermo-mechanical process), chemical pulping (includes kraft and sulfite pulping also), and semi-chemical pulping.
Mechanical pulping is the oldest form of pulping. The process employs mechanical energy to weaken and separate fibres from wood and waste paper feedstock via a grinding action. The advantage to mechanical pulping is that it produces much higher yields than chemical pulping processes (up to 95%). However, because this process does not dissolve lignin, the fibre strength and age resistance of the resulting pulp are low. The weakness of the resulting pulp is compounded by the fact that the mechanical grinding process also produces shorter fibres.
In the thermo mechanical pulping (TMP) process, wood chips are first steamed to soften them before being ground in the same manner as the RMP process. The TMP process generates the highest grade mechanical pulp but is also a high energy intensity process due to its steam use.
Chemo-thermo-mechanical pulping (CTMP) involves the application of chemicals to wood chips prior to refiner pulping. The process begins with an impregnation of sodium sulphite and chelating agents. The mixture is then preheated to 120-130 ºC and ground in the refiner.
Raw pulp can range in color from brown to crème due to the remaining lignin that was not removed during the pulping process. For paper products for which brightness and resistance to color reversion are important, such as office and printing paper, the pulp must be whitened by a bleaching process prior to the paper making phase.
The papermaking process can be divided into three basic stages: (1) stock preparation, (2) “wet end” processing where sheet formation occurs, and (3) “dry end” processing where sheets are dried and finished.