Information about hygiene paper
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General description
Although there are a wide variety of paper products and different process layouts in paper mills almost all types of paper- and board-making processes have the following basic units:
- stock preparation;
- approach flow system;
- a paper and board machine consisting of:
- a headbox that introduces the suspension of fibres to the wire and creates a uniform dispersion of fibres across the total width of the wire belt,
- a wire section that drains paper web to around 12 – 20 % solids,
- a press section that removes more water out of the web by pressing down to about 50 % moisture content,
- a drying section that removes the rest of the moisture by heating the web with drying cylinders,
- a reeler that reels the paper web into a roll;
- on-line aggregates (e.g. calender, sizer, coater);
- depending on the paper and board grade, there are additional process units (optional) like calenders, sizer, coaters, a coating colour kitchen, winders, rewinders, sheeting plant and a roll wrapping station
Overview
Schematic overview of subsystems to consider when comparing energy balances of pulp and paper mills
Mass stream overview of a paper mill
Energy consumption and efficiency
In order to reduce fuel and energy consumption in pulp and paper mills, BAT is to use technique (a) and a combination of the techniques given below.
Technique (c): simultaneous generation of heat energy and electrical and/or mechanical energy in a single process, referred to as a combined heat and power plant (CHP). CHP plants in the pulp and paper industry normally apply steam turbines and/or gas turbines. The economic viability (achievable savings and payback time) will depend mainly on the cost of electricity and fuels.
Tissue paper
In the table below consumption and emission levels for typical tissue mills are compiled. Emissions are given as typical values after flue-gas and waste water treatment. The main difference between virgin and secondary fibre mills is solid waste. While virgin fibre mills generate 10 – 40 kg waste/t of paper (100 % DS), amounts of 400 – 600 kg waste/t of paper result from recycled fibre processing (see Section 6.2.2.6). Some of the value ranges in Table 7.4 are quite wide because they cover:
- different tissue-making processes (conventional, TAD, hybrid);
- small and large tissue mills;
- old and new paper machines;
- mills with and without cogeneration (higher natural gas consumption);
- mills with many grade changes (more stop-start);
- mills with many colour changes (higher water consumption for cleaning);
- mills in different geographical locations (no water restrictions in Nordic countries).
Consumption and emission levels for typical tissue mills
Source: Best Available Techniques (BAT), Reference Document for the Production of Pulp, Paper and Board,2015
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