Fossil-free mills with lower NOx emissions
Purified methanol from pulp mills is a renewable, high-quality fuel. It is produced naturally from the incoming wood and can be used instead of oil. Better use of it can therefore help pulp mills to reduce their use of fossil fuels.
Purified methanol has other benefits as well. Since most of the nitrogen is removed, fuel NOx is practically eliminated and emissions of NOx are lower.
The Valmet methanol purification technology is designed as an upgrade to existing methanol plants. The first step in the upgrade is to install a low-NOx module upstream from the methanol plant. The low-NOx module mainly removes nitrogen and water from the stripper off gas.
A methanol plant with upgrade for production of purified methanol
Methanol for production of chlorine dioxide has to be free from compounds like ethanol and acetone. These compounds can be removed with a distillation technology similar to the one used in traditional methanol plants.
If the upgraded methanol plant is further upgraded with two distillation columns, the flow of purified methanol becomes one flow of distilled methanol and one flow of purified methanol. The distilled methanol is extremely pure and can be used in several processes that require the methanol to be of very high quality.
Using purified methanol can help the mill to reduce the use of fossil fuels and could also help to lower emissions of NOx. But there are also other mill processes where methanol can be used.
Chemical consumption and sulfur recovery
The Valmet methanol purification process uses sulfuric acid to convert ammonium into ammonium salts and promote separation of sulfur components. The extracted oil (red oil) contains sulfur and can be incinerated in the recovery boiler. The cost of chemicals is very low compared to the financial benefits of locally produced methanol.