Energies 2021 , 14 , 1161
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The remaining water is then removed from the paper in the drying part, and the fiber content is increased to 90–95% [17]. Drying is normally carried out with steam-heated cylinders enclosed in a hood. The dryer section consumes a large amount of energy in the form of steam (see Table 3 for the dryer section’s energy consumption for each paper type). However, all paper mills have installed heat recovery systems in the drying section to utilize the exhaust air (generally with the temperature 80 to 85 ◦ C and humidity 140 to 160g H 2 O /Kg DA ) and recover it in a heat exchanger [17]. Afterward, the paper can be subjected to finishing processes, namely coating and calendering. Coating is the application of chemicals to the paper to give it superior surface properties. It is only applied to some types of paper. The drying process can be divided into pre-coating drying and post-coating drying when the coating is needed. The calendering process consists of running the paper through a set of rolls, increasing surface smoothness, and improving its appearance. Finally, the paper is rolled and stored for delivery to market.
Table 3. Specific electricity and heat consumption of the paper processes in pulp and paper production.
Process
Specific Electricity Consumption (kWh/t paper ) Specific Heat Consumption (GJ/t paper ) Reference Newsprint
Forming and Pressing
422.0 29.31
0.0
[15,21] [15,21]
Drying
4.29
Printing (Coated) Paper
Forming and Pressing
527.5
0.0
[15,21]
Drying
29.3
5.48
[21]
Writing (Uncoated) Paper
Forming and Pressing
527.5 29.31
0.0
[15,21]
Drying
5.27
[21]
Tissue
Forming and Pressing
533.4
0.0
[15,21]
Drying
131.88
4.22
[21]
Packing paper
Forming and Pressing
269.6
0,0
[15,21]
Drying
14.7
4.22
[21]
While pulping (i.e., chemical peeling) is more energy self-sufficient, the energy needed for papermaking must be supplied from the grid.
2.2. Austrian Pulp and Paper 2.2.1. Overview of the Pulp and Paper Sector
Today, more than 90 million tons of paper are produced in about 900 pulp and paper mills in the EU [24]. With around 5 million tons of paper in 2017, Austria accounted for 5.3% of EU paper production [24]. The Austrian P&P sector consists of 21 companies with 24 mills [9]. According to the Association of the Austrian paper industry (Austropa- pier (https://austropapier.at/unternehmen, accessed on 30 November 2020)), the paper manufacturers’ production capacity and structure are not particularly equal. The three largest companies account for more than one-third (39% or 2280 kilo tons) of the annual production (pulp, market pulp, and paper). Eleven medium-sized mills account for 54% of total production, and the remaining smaller mills have a low production capacity of less than 7% (426 kilo tons) [25]. About 25% of pulp and 88% of paper production is exported, mainly to European countries such as Germany, Italy, and Slovenia [9]. The production processes of pulp and paper are quite heterogeneous: approximately 51% of the total pulp is produced from raw wood using mechanical (16%), chemical (62%, (approx. 75% kraft pulp and 25% sulphite pulp [14])), and textile (22%) pulp, and the rest of the pulp is RCF pulp from (de-inked and non-deinked) recovered paper (The paper recycling rate was 74% in 2017 in Austria [9]). Paper production is also divided into graphic
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