Canadian Forest Service Publications

The effect of varying air injection rates on tall oil soap skimming efficiency for low fatty acid/resin acid ratio soaps produced by pulping mountain pine beetle-infected wood. 2009. Uloth, V.; Guy, E. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, BC. Mountain Pine Beetle Working Paper 2009-27. 11 p.

Year: 2009

Issued by: Pacific Forestry Centre

Catalog ID: 31185

Language: English

Series: Mountain Pine Beetle Working Paper (PFC - Victoria)

Availability: Order paper copy (free), PDF (download)

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Trials on the evaporator soap skimmer at a British Columbia Interior mill were conducted to assess the impact of higher air injection rates on skimmer performance. Those tests indicated that the mill now has very poor skimming efficiencies: only 13%-38% of the total soap in the feed liquor was skimmed for low acid number (114-118) and low fatty acid/resin acid ratio (0.73-0.83) soap. In addition, there were extended periods over the two-day trial when soap skimming stopped completely and the soap levels in the skimmed liquor equalled or exceeded those in the feed liquor. Higher air injection rates were observed to have little beneficial impact on soap-skimming efficiency. As expected, the higher air injection rates decreased the soap density by about 8% and increased black liquor entrainment in the skimmed soap by nearly 35%. As high percentages of black liquor can cause high H2S emissions during soap acidulation, and the precipitated lignin can hinder tall oil separation, the use of higher air-injection rates cannot be recommended.