Pulp and Paper

Oxygen delignification is a proven technology widely used to remove 40-50% of the residual lignin in non-bleached pulp. Use of oxygen reduces operating costs by reducing the amount of bleaching chemicals required in subsequent processing by targeting the easily oxidized lignin molecules. Oxygen also serves to reduce the emission of chlorinated byproducts and lowers the organic load and toxicity of the resulting wastewater. Additionally, it can be used in extended oxygen delignification (EOD) to increase the efficiency of the fiber lines.

The introduction of oxygen to alkaline extraction is a proven method used for kraft bleaching. Oxygen, added during the alkaline extraction stage, serves to remove additional residual lignin, increases brightness and saves on bleaching chemicals, reducing environmental impact.

Ozone is generated from electrical discharge on an oxygen gas stream. It is unstable at ambient temperatures and must be generated from oxygen on-site. The use of ozone provides efficient delignification with reduced consumption of bleaching chemicals and effluent load.

The white liquor oxidation process uses oxygen to oxidize sodium sulfide and sodium sulfate. Heat generated during this exothermic process can be recuperated. The process produces an economical alkali source used in bleaching and deliginfication processes and helps to reduce caustic purchases, while providing better control of the plant's chemical balance.

The black liquor oxidation process uses oxygen to oxidize sodium sulfate to sodium thiosulfate, alleviating recovery boiler bottlenecks. BLO can help to reduce sulfur losses that occur during the multiple effect evaporation and reduce odor emissions in processes with direct contact evaporators.

Oxygen enrichment of the lime kiln is a proven technique to achieve a number of benefits for captive lime production in a paper mill. These benefits include: production increases of up to 20%, fuel savings, reduced need for make up CaO, reduced sulfur compound emissions (TRS), and improved operational flexibility and kiln stability. Increased kiln throughput allows more lime to be recovered and less waste sent to landfills. The economics of lime kiln enrichment can have very short paybacks.

Nitrogen has several inerting and blanketing uses within pulp and paper mills, including tanks and piping, silos for plants with pneumatic ash handling, and chlorine rail cars.

Carbon dioxide (CO₂) can be used to increase production in pulp washing and to reduce corrosion in paper machines by replacing acids for pH control. In wastewater treatment, CO₂ is used for pH control and oxygen is used for odor control as well as secondary water treatment, where it significantly improves performance versus air-based treatment processes.