Siloxy -- Opportunities -- Cotton Linter

a NORAM company


	Cotton Linter Rice Straw Wheat Straw Bagasse

Nonwood Pulp Mills – Cotton Linter

Background

Cotton linters are processed into high-quality cellulose feedstock by a process of chemical pulping and bleaching. In the chemical pulping step, the linters are cooked in a solution of sodium hydroxide which strips away fats and other contaminants that are soluble in the alkaline cooking liquor. The "spent" liquor has a low calorific heating value which makes it impossible to use a traditional recovery boiler to recovery heat and chemicals. The liquor also has a high tendency to create foam when evaporated, which makes it difficult, if not impossible, to use standard multiple-effect evaporator processes. As a result, cotton linter spent liquor is commonly treated by biological means, resulting in high aeration costs and the loss of valuable cooking chemicals.

Opportunity

The combination of both the Siloxy evaporation and oxidation processes makes the recovery of cotton linter spent liquor possible.

Developed specifically for the cotton linter spent liquor application, the new Siloxy evaporator system avoids the generation of foam during evaporation.

The Siloxy oxidizer is ideally suited for the recovery of the spent pulping liquor. The use of high-purity oxygen makes the combustion of low calorific heating value liquor possible. Eighty-five percent (85%) of the heat of combustion is recovered as process steam. Plus, the sodium in the spent liquor is recovered in a sodium carbonate solution which is causticized to produce sodium hydroxide. The sodium hydroxide solution, white liquor, replaces purchased sodium hydroxide

Benefits

Environmental

	Eliminates the spent liquor biological oxygen demand (BOD) and chemical oxygen demand (COD) load to the wastewater treatment plant.

	Significantly lowers the discharge of sodium into the effluent receiving water.

	Lowers the release of volatile organic compounds into the atmosphere from the aerobic wastewater treatment system.

	Substantially lowers the consumption of water and effluent discharge by recycling condensate from the multiple-effect evaporator system.

	Lowers greenhouse gases emissions by converting the energy from the combustion process into steam and by reducing the electrical power needed to produce sodium hydroxide.

	Lowers SOx, NOx and particulate emissions by displacing steam production from fossil fuels.

Economic

	Substantially lowers the purchase of costly sodium hydroxide by recovering the valuable chemical from the black liquor.

	Lowers the consumption of fossil fuel (e.g., coal) by displacing steam produced in a steam generator (boiler).

	Substantially lowers the power requirement of the wastewater treatment system.

	Reduces the capital cost (size) of the wastewater treatment plant (new installations).