Abstract: The method is for separation of lignin from original black liquor (BLIN) having a first precipitation phase (PR1/PR2) for precipitation of lignin by a first acidification using acidifier, CO2, at alkaline conditions, then separating a lignin cake with subsequent suspension of the lignin cake in a strong acid to leach our metals from the lignin followed by dewatering and obtaining a clean lignin product LP. The acidic liquid phase (FL1) subjected to a sulphur removal process wherein a calcium containing compound is added to the acidic liquid phase, whereby sulphur in the acidic liquid phase is reacting with the calcium compound forming solid gypsum which could be separated and bled off from the process. The remaining acidic liquid could then be returned to the recovery process without negatively affecting the sulphur balance of the mill.

Abstract: The method is for separation of lignin from original black liquor. Lignin is precipitated in a first acidification stage followed by dewatering a first lignin suspension while forming a first filter cake. The first lignin filter cake is suspended in a second acidification stage whereupon a second lignin suspension is obtained. The second lignin suspension is dewatered to form a second filter cake. The second filter cake is washed and the washed second lignin cake is dewatered to obtain a lignin product. Waste gases from the second acidification stage is recirculated back to the first acidification stage and mixed with the original black liquor.

Abstract: The method is for separation of lignin from original black liquor (BLIN) and has the following phases in sequence. A first precipitation phase (PR1) for precipitation of lignin by a first acidification of the original black liquor by adding a first acid or mixture of acids (G1a) followed by a first storage phase wherein precipitated lignin particles are allowed to increase in size, followed by a second precipitation phase (PR2) for precipitation of lignin by a further acidification of the original black liquor by adding a second acid or mixture of acids (G1b). By retaining the acidified black liquor for at least 25 minutes in the storage phase are the precipitated lignin particles allowed to grow in size and the filterability is improved considerably.

Abstract: The improved method and arrangement are for cooling torrefied lignocellulosic material. By adding water in controlled amounts to the torrefied material in a grinder at exit from a roaster the entire volume of torrefied material could be cooled down to a temperature well below the critical temperature without increasing the water content of the final product.

Abstract: The method and equipment are for the evaporation of hot black liquor obtained from a digestion process during the production of cellulose pulp. The black liquor is led to a multistage evaporation line with at least five evaporation stages. The black liquor that is to undergo evaporation in the evaporation line is cooled in at least one heat exchange process in a heat exchanger (HE1) against the partially evaporated black liquor that has undergone evaporation in at least one stage (I). The black liquor that is to undergo evaporation is cooled and the partially evaporated black liquor is heated by at least 5-10° C. The risk for the formation of foam and the separation of methanol are reduced. The greater part of the evaporation takes place at low temperature and at the lowest level of dry matter content in the liquor, which also suppresses encrustation in the stage.

Abstract: An insert tube is used for the repair or improvement of a pre-heating tube for air arranged in an exhaust gas pathway of a fuel burner. A pre-determined radial gap exists between the outer surface of the insert tube and the inner surface of the pre-heating tube for air such that the insert tube can be slid into the pre-heating tube for air. The insert tube is provided in the vicinity of each end with at least one groove that runs around its circumference. In the groove there is arranged at least one sealing ring of an elastic material. The sealing ring mounted in the groove has an external diameter that exceeds the internal diameter of the preheating tube for air. The sealing ring forms a seal against the inner surface of the pre-heating tube for air and prevents leakage through the sealing ring.