The Condebelt drying process was patented in 1975. The Condebelt drying process was originally created to increase drying rates of paper. Condebelt drying produces approximately 10-15 times higher drying rates than conventional cylinder drying. These higher drying rates are achieved by higher contact temperatures, higher pressing between the hot surface and paper and relatively low thermal resistance between steam and paper in the Condebelt drying process.
According to Retulainen (2001), three features of the technology warranted further investigation after the first pilot tests:
- Improved strength and other quality characteristics
- Increased drying rates
- Possible energy savings
Despite being patented in 1975 and being proven to have several advantages over conventional cylinder drying, the Condebelt process and machinery are still in the development phase. As such, the information on Condebelt drying is scarce.
Figure 1: Lab-scale Condebelt dryer. Source: Timofeev, Ilomaki & Kuusela, 2004
Feasibility of technology and operational necessities
Figure 2: Condebelt drying process. Source: Lae Lee, Jung Yuon & Min Jung, 2000
The essential feature of the Condebelt process is the use of the cold belt as a condensing belt.
The conventional cylinder dryer uses a large ventilation system. This is not required in the Condebelt drying process, as evaporation energy is transferred to the cooled belt by means of vapor diffusion and condensation inside the closed drying chamber.
Figure 3: Effect of Condebelt Drying on Core Board (300–550 g/m2). Source: Retulainen, 2001
The Condebelt drying process enhances web consolidation, which results in an increase in paper density and strength as seen in Figure 3. Condebelt-dried sheets have extremely good smoothness on the side which is in contact with the hot metal surfce.
Status of the technology and its future market potential
The results obtained from the first mill scale applications have clearly exceeded the early expectations put on the paper properties. Retulainen (2001) concludes that while the technology has not become a success story yet, it has the capacity and advantages to become one.
How the technology could contribute to socio-economic development and environmental protection
Figure 4: Improvements in compression strength due to Condebelt drying: Edge crush test (ECT) values of corrugated board and Box compression strength (BCT) values of corrugated containers. Source: Retulainen, 2001
The Korean installation has shown that the corrugated containers made of Condebelt dried board show remarkable improvement in edgewise and box compression strengths (Retulainen, 2001). The improved compression strength of the board has made it possible to substitute conventional triple wall board with double wall Condebelt dried board. This is a considerable advantage for the converter. The better printability and dimensional stability has been verified both by pilot scale tests (Retulainen et al., 2000) and mill experience. The experience indicates that the advantages can be best utilized within a integrated company containing pulp, board and converting operations. Many of the potential advantages proposed by the laboratory and pilot scale tests (Retulainen, 1997), such as reduction of basis weight, using higher yield pulp, increasing the amount of recycled pulp, or producing completely new board grades have hardly yet been utilized in practice.
Financial requirements and costs
Moreover, Retulainen (2001) notes that the technology provides the possibility to reduce raw material costs by using lower quality raw material or using lower basis weight board due to the increased strenght and performance of the end product. In addition, the faster drying rates of the Condebelt process might result in financial advantages as more paper and pulp can be dried within the same time period.
However, more investigation and research is required to establish the financial aspects of the Condebelt drying process.
Clean Development Mechanism market status
- Timofeev, O.N., J. Ilomaki, J. Kuusela (2004). Effect of process parameters on paper temperature in condebelt drying. Drying 2004 - Procceedings of the 14th International Drying Symposium (IDS 2004) Sao Paolo, Brazil, 22-25 August 2004, Vol. B, pp. 1327 -1334. Document can be found at: www.feq.unicamp.br/~ids2004/volB/pp%201327-1334.pdf
- Lae Lee, H., H. Jung Yuon & T. Min Jung (2000) Improvement of linerboard properties by Condebelt drying. Tappi Journal peer reviewed . paper. Document can be found at: http://www.tappi.org/Bookstore/Technical-Papers/Journal-Articles/TAPPI-JOURNAL/Archives/2000/July/Improvement-of-linerboard-properties-by-condebelt-drying-TAPPI-JOURNAL-July-2000-Vol-837.aspx
- Retulainen, E., (2001). Key development phases of Condebelt: Long journey from idea to commercial product. Drying Technology, 19: 10, 2451 — 2467. Document can be found at either DOI: 10.1081/DRT-100108248 or URL: http://dx.doi.org/10.1081/DRT-100108248
- Retulainen, E., Kangas, J., Kunnas, A. and Oittinen, P., 2000, Printability of Condebelt dried linerboard. The 54th Appita Annual Conference Melbourne, Australia. 3–6-April 2000. Proceedings, Volume 2, 3A22 pp. 403–408.