| abstract |
In the method, spent digestion liquid, which originates from digestions of cellulosic vegetable material by means of organic solvents at elevated temperature and elevated pressure, is subjected to flash evaporation. In order to avoid precipitation of the lignin degradation products during the cooling involved in flashing in the form of viscous and tarry products, which are difficult to transport, and, furthermore, occlude substantial quantities of solvent, and to improve the degree of recovery of the digesting agent, the vaporisable constituents of the digestion liquid are completely removed by a single-stage flash evaporation with heat supply and separated by distillation, and the non-vaporisable residue is recovered in a solid form. <IMAGE> |