The process from wood - pulp - paper consumer is to a large degree closed. The cooking chemicals are recycled to 99%, the modern chemical pulp mill is energy-self-sufficient from biofuel and the paper products can be recycled, composted or used as energy. Not in any case is the global CO2 balance affected. The weak link of this chain is the process for manufacture of the pulp which emits SO2 and NOx to air and organic and inorganic substances to water. The emissions to air and water can be reduced to minimum levels by using modern process technology especially in the production of breached (and unbleached) chemical pulp. The problems with bleached pulp is substantially larger. The challenge is to more or less eliminate the emissions to water. In this project the emissions to water will be the main priority. Air emissions will be addressed if they are affected by system closure.
The different parts of the project are given below:
- trace elements (inorganic substances) in wood have to be purged in a controlled way from the system. The system should be designed in such a way that the steady-state concentration of non-process elements does not lead to process/product problems. More knowledge about the inorganic chemistry is one corner stone in this activity.
- organic substances, especially lignin and wood extractives, have to be handled in a proper way in order to minimize process/product problems due to build up in a closed cycle mill;
- the closed cycle pulp mill requires advanced process control. One challenge here is the handling of water especially as it seems unrealistic to use large buffer tanks as is standard today in the partially closed cycle mill;
- the project will focus on the modern modified versions of kraft cooking with high selectivity made possible by extended delignification without a loss of pulp quality and wook yield. Alternatives like sulfite cooking and solvent pulping processes under development will however also be included for comparison. One boundery restriction is that the product quality must not suffer compared to the level of semi and fully bleached softwook and hardwood kraft pulps.
Funding SchemeCSC - Cost-sharing contracts