Method of and an arrangement for transferring a process liquid, an industrial facility and a method of simplifying the layout of such
The present invention relates to a method of and an arrangement for transferring a process liquid from a washing and thickening device to a subsequent process stage. In accordance with an advantageous embodiment of the present invention, the method and the arrangement are applicable, for example, in transferring fibre suspensions or pulps from washing and thickening device to a subsequent process stage in pulp and paper making industry such that the dilution of pulp after a washing and thickening device is performed in a stand pipe ( 18 ) below the surface level control range.
1. A method of transferring a fiber suspension from a washing and thickening device to a subsequent process stage, the method comprising the steps of:
discharging the fiber suspension in a consistency of 20-50% from a washing and thickening device,
taking the fiber suspension to a stand pipe,
diluting the fiber suspension to a second consistency, i.e. to a MC-consistency,
providing the stand pipe with means for measuring the surface level of the fiber suspension in the stand pipe, the measuring means having a surface level control range with an upper surface level control limit, and a lower surface level control limit for maintaining, when in use, the surface level of the fiber suspension between the upper and the lower surface level control limits,
discharging the fiber suspension in the second consistency from said stand pipe by means of a pump arranged in flow communication with a discharge outlet opening provided in the stand pipe,
characterized by the further step of
providing the fiber suspension in the surface level control range in the stand pipe with an average consistency, i.e. a third consistency, the third consistency being at least 1.5 times the second consistency.
2. The method as recited in claim 1 , wherein the third consistency is at least 2 times the second consistency.
3. The method as recited in claim 1 , characterized by performing the dilution of the fiber suspension to the second consistency in the stand pipe below the lower surface level control limit of the surface level control range.
4. The method as recited in claim 3 , characterized by performing the dilution by means of one of a rotary device having one or more blades or paddles and a rotary device feeding the fiber suspension towards the discharge outlet opening.
5. The method as recited in claim 4 , characterized in that the surface level measuring means are one of a rotary device having one or more blades within the surface level control range, gamma ray and process tomography.
6. The method as recited in claim 1 , wherein the second consistency is between 6 and 15%.
7. The method as recited in claim 1 , characterized by at least one of heating the fiber suspension by means of the dilution liquid and adding a chemical to the fiber suspension by means of the dilution liquid.