PROCESSO PER LA PRODUZIONE DI CELLULOSE CHIMICHE E/O PASTE PER CARTE, NONCHE'IMPIANTO E RELATIVI COMPONENTI PER L'ATTUAZIONE DEL PROCESSO INDICATO

A process to produce pulp from vegetable, cellulose-containing fibrous material such as coniferous wood, hardwood, straw, bagasse etc., the fibrous material being treated in several stages. In a first stage the fibrous material is impregnated with a solution of sodium hydroxide, in which solution the material is soaked and partly disintegrated by mechanical working. In a second stage excess of alkaline solution is squeezed out to such extent that the content of sodium peroxide in the raw pulp amounts to at least 15 kgs per BD ton of pulp. In a third stage the pulp material is subjected to additional disintegration under supply of a solution of sodium carbonate so that a pumpable pulp suspension having a sodium carbonate content of 150-400 kgs per BD ton of pulp is obtained. In a fourth stage the pulp suspension is subjected to a cooking process at a temperature of at least 100`C during 1-4 hours and under stirring and supply of oxygen, whereupon the cooked pulp is washed.