Valmet’s family of paper machine ventilation processes and products goes under one name – OptiAir. The OptiAir family is a complete energy-efficient set-up for paper and board machine process ventilation. The family consists of the OptiAir Hood, OptiAir Recovery and OptiAir Environment processes and products.
In paper and board making processes, resources such as raw materials, water and energy, must be used in a more efficient way than today. A spotlight has been put on energy consumption – energy will continue to be a significant factor, influencing overall production costs. Any improvement in decreasing energy consumption will immediately pay back as a more profitable operation and decreased CO2 emissions. OptiAir process ventilation solutions provide excellent opportunities for reducing costs and increasing the profitability, of both new and old machines.
The energy used in the paper drying and evaporation process is bound in the exhaust air. After that, the process ventilation and heat recovery functions practically define the total energy efficiency of the machine.
Once a huge amount of energy has been used for drying, the energy doesn’t disappear. The energy in the steam used in the cylinders is released by condensing the steam. Then this energy is transferred through the cylinder cell into the paper sheet. The steam energy will be bound in the evaporated water and finally all the evaporated water with energy from the steam will be in our exhaust air. Actually, we have more energy in the exhaust system than in the steam flow into the cylinders, because there is already quite a lot of energy in the incoming supply air flow. In a modern paper or board machine, over 50 MW of heat can be recovered. It is important to utilize this energy efficiently.
Significant energy content exists not only in the dryer section but also in other process exhausts such as the vacuum system exhaust and the exhaust air of coating dryers. In practice, there is enough energy in the process exhausts for all water and process air heating. Machine hall heating in cold regions can be also done with this secondary energy.
From the results of energy analyses, we can separate out the various actions and their impact on steam consumption.
Global targets have been set for energy saving, the reduction of carbon dioxide and better energy efficiency. Energy is also one of the biggest costs in paper and board making, but we have good news for paper makers! There is still a lot of potential for saving energy.
Process ventilation systems provide exciting new opportunities for reducing costs and carbon footprint and increasing profitability. However, these opportunities need to be investigated – simply because the systems are running, making paper, do not assume that they are running efficiently. You have to look for the opportunities, they are there!
In 2019, Ajin P&P decided to rebuild its paper machine PM 2 with a target to increase the mill’s production and improve the end-product quality. The rebuild was delivered by Valmet and it included OptiAir Recovery mist remediation to reduce and eliminate mist and enable the increase of heat recovery capacity.
In a modern paper or board machine, the effect of heat reclaimed from dryer section exhaust air can translate to over 40 MW of energy saved during periods of peak heating. But the benefits of effective heat recovery are by no means restricted only to such cases, since, in practice, notable savings can be reached at all times. A recent heat recovery system rebuild at SCA Packaging’s Obbola PM 1 kraftliner machine in Sweden yielded energy savings of over 11 MW.
“Working together with Valmet we improved the energy efficiency of coating machine 3,” says Matti Korhonen, Assistant Process and Quality Manager. “We have been very pleased with the results. We are now using close to 20% less gas-generated energy for drying coating than before.”