Method for producing cellulose pulp in a continuous digester in an energy-efficient manner
a technology of cellulose pulp and digester, which is applied in the direction of digesters, textiles and papermaking, finely divided material pretreatment, etc., can solve the problems of liquid added in the supply line that can give rise to blockage at the top of the digester, and achieve the effect of reducing the heating requiremen
Inactive Publication Date: 2008-09-04
METSO FIBER KARLSTAD AB
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Benefits of technology
[0009]A first object of the present invention is to reduce the requirement of heating with steam at the top of the digester.
[0010]A second object of the present invention is to be able to heat the chips before the cooking process using a temperature of the hot liquid that is higher than that which is possible when the heating is carried out at the transfer flow.
[0011]A third object of the present invention is to avoid clogging at the top separator in a steam phase digester.
Problems solved by technology
One limitation of this method is that the temperature of the black liquor that is added should not be too high, since this would then introduce the risk of steam implosion.
One risk with this solution is that the liquid that is added in the supply line can give rise to blockage at the top of the digester since the added liquid can risk flushing the chips in a backwards direction.
Method used
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Embodiment Construction
[0023]FIGS. 1 and 4 show a first preferred embodiment of a method for producing cellulose pulp in a continuous digester system in an energy-efficient manner. Cellulose chips are fed continuously to an impregnation vessel 10 in order to be impregnated in an impregnation liquid in the impregnation vessel 10.
[0024]Once the impregnation is finished, the impregnated chips are fed with a transfer liquid in a transfer line 11 to a top separator 20 arranged at the top of a digester 30, for the separation of free liquid from the cellulose chips, where the digester 30 is a steam phase digester.
[0025]The transfer line 11 is connected to the bottom of the top separator 20 and the chips are thus fed upwards through the top separator.
[0026]In accordance with FIG. 4, the top separator 20 has a rotating upwardly feeding screw 22 that is arranged vertically. The top separator 20 has also a screening surface 23, which is surrounded by an impenetrable wall 24 for the formation of an intermediate withd...
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Abstract
The method is for producing cellulose pulp in a continuous digestion system in an energy-efficient manner. Cellulose chips are fed continuously with a transfer liquid in a transfer line to a top separator arranged at the top of a digester, for the separation of free liquid from the cellulose chips. The top separator has a withdrawal space in which free liquid collects. At least a fraction of the free liquid that has separated, with a temperature Tout, is led in a return line from the withdrawal space of the top separator to a position to be used as transfer liquid. At least one pressurised withdrawal of black liquor is carried out in the digester essentially at the cooking temperature of at least 135° C. An additive liquid with a temperature Tin is added at the withdrawal space of the top separator, where the temperature Tin is greater than the temperature Tout.
Description
PRIOR APPLICATION[0001]This patent application claims priority from Swedish patent application number SE 0602675-1, filed 13 Dec. 2007, now Swedish Patent number 529 573.TECHNICAL AREA[0002]The present invention concerns a method for producing cellulose pulp in a continuous digester in an energy-efficient manner.BACKGROUND AND SUMMARY OF THE INVENTION[0003]In conventional continuous digesters, chips are impregnated with impregnation liquid in an impregnation vessel. The impregnated chips are subsequently cooked in a digester, whereby the impregnation vessel and the digester are coupled to each other by means of a transfer circulation. The transfer circulation consists not only of a transfer line that feeds the chips from the outlet end of the impregnation vessel to the top of the digester for the separation of free liquid in a top separator, but also of a return line that feeds separated liquid from the top of the digester to the outlet end of the impregnation vessel in order to be ...
Claims
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IPC IPC(8): D21C3/24
CPCD21C1/00D21C3/00D21C7/14D21C7/00D21C3/22D21C3/24D21C7/06
Inventor SNEKKENES, VIDAR
Owner METSO FIBER KARLSTAD AB