Pulp and paper manufacturing requires large amounts of energy. Especially, drying process in papermaking consumes over 50% of all the energy required. To reduce drying energy, we proposed a method to increase OCC solid content at the wet press by adding MDF fiber and inorganic materials such as GCC (grounded calcium carbonate) and diatomaceous earth in fiber furnishes. MDF fiber, GCC, and diatomaceous earth, which are defined as spacers in this paper, are used to increasing draining rate and bulk in fiber furnishes. The basic concept of this approach is to apply high wet pressing pressure to the bulky sheet, that contains spacers. The sheet containing spacers has equivalent or slightly lower solid content at the same wet pressing pressure, but after applying high enough pressure, the solid content of the sheet becomes higher depending upon how much higher pressure is applied. The crushing possibility at the wet press at the time of applying higher wet pressing pressure on the spacer containing sheet was not fully addressed in this study, and needed to be examined by future study.
The results of the study were summarized as followed;
1. Refined OCC containing MDF fiber increased 5% solid content without loss of other essential properties such as compression strength, compared to unrefined OCC at equivalent bulk by applying higher wet pressing pressure.
2. Refined OCC containing modified MDF fiber(which means refined MDF fiber with ozone treatment) increased 3% solid content with improvement of other paper properties such as bulk, drainage rate and strength compared to unrefined OCC by applying higher wet pressing pressure.
3. Refined OCC containing minerals such as GCC and diatomaceous earth increased 4% and 1.5% of solid content respectively without loss of other essential properties such as compression strength and bulk, compared to unrefined OCC by applying higher wet pressing pressure.