Pulp and Paper
Historically the pulp and paper industry has had little need for desalination and reuse – not least because the majority of production is located near water sources. Four things are changing this state of affairs:
• The move towards recycling means that production in mills located in “urban forest” areas is rising. These facilities face higher water costs than green forest located mills, and have a greater interest in water efficiency.
• The fastest growing market for pulp and paper is in China, where raw water sources are both limited and impaired, and water technologies which can address these challenges are at a premium.
• The new generation of efficient boilers used in the industry require higher quality feedwater than the traditional boilers, and as existing production facilities are refitted, there will be greater demand for ultrapure water treatment lines than have historically been the case.
• Regulators are becoming more proactive about controlling effluent from the pulp and paper industry: this is especially true in the case of China, where environmental protection has not been a priority.
The pulp and paper industry represents a group of industries that produce different grades of pulp and paper for various purposes, such as cardboard, tissues and newspapers. Water plays a dominant role in the pulp and paper making process: it is used in various steps of the process, as well as a medium for transporting the fibres (raw material) through the paper machine. A typical 1,000 t/d pulp and paper plant would use up to 70,000 m³/d of water. Water and the paper product are so intertwined during the paper production process that, for example, at the beginning of the process, the stock solution is typically 99% water and 1% fibre, while the final product may be around 5% water and 95% fibre.
Process description: Pulping and paper manufacturing process
The following figure depicts the main steps in the paper making process, along with the water and wastewater aspects involved.
Historically, pulp and paper facilities were located in close proximity to water sources, and there was little need for water reuse. However, the situation is changing, with the use of advanced technologies coming into favour as a result of the following:
There is an old saying in the industry – paper doesn’t travel well, but pulp travels very well. Paper mills are therefore being built in places where there is growth in paper consumption per capita. In the emerging markets, the consumption of paper per capita is still increasing in the BRIC countries (Brazil, Russia, India and China). In the traditional, mature markets, such as North America and Western Europe, the case is quite the opposite – the consumption of paper per capita is decreasing.
Process water requirements
Water requirements for modern pulp and paper mills can vary considerably, depending on the pulping process, water availability, the bleaching sequence, and the restrictions on wastewater discharge. Water quality is very important in some cases because it has a direct influence on the quality of the pulp and paper product (especially in the case of bleached pulp).
Wastewater characteristics in the pulp and paper industry can differ significantly based on mill processes and material inputs. To a large degree, the type of chemicals used in processes determines the wastewater treatment needs. The major contaminants in the wastewater, resulting from various steps in the pulp and paper making process, are shown in the following figure.
Supply chain analysis
There are various ways an equipment supplier can approach a pulp and paper client. In a situation where the pulp and paper company wants to develop a mill, it is very common for the pulp and paper company to contract a consultant, as they themselves usually do not have the structure to develop the mill on their own. Different approaches can be summarised as follows:
The water and wastewater treatment market for the pulp and paper industry is relatively flat. It will show a small amount of growth but nothing drastic, as shown in the following figure.