Abstract: A method of and an apparatus for controlling the height of a material column in a vessel upstream of a pump, in which method material is conveyed into an upper portion of the vessel, electrical signals are provided on the basis of the presence of material at predetermined measuring levels of the vessel by using a first sensor set disposed at a first measuring level at the upper portion of the vessel and a second sensor set disposed at a second measuring level at the lower portion of the vessel, and material is extracted at a controlled flow speed from a lower portion of the vessel by the pump, wherein the provided electrical signals are used to infer weighting factors of measuring level presence functions, and the flow speed is controlled on the basis of the weighting factors of the measuring level presence functions.

Abstract: A method of and an apparatus for controlling the height of a material column in a vessel upstream of a pump, in which method material is conveyed into an upper portion of the vessel, electrical signals are provided on the basis of the presence of material at predetermined measuring levels of the vessel by using a first sensor set disposed at a first measuring level at the upper portion of the vessel and a second sensor set disposed at a second measuring level at the lower portion of the vessel, and material is extracted at a controlled flow speed from a lower portion of the vessel by the pump, wherein the provided electrical signals are used to infer weighting factors of measuring level presence functions, and the flow speed is controlled on the basis of the weighting factors of the measuring level presence functions.

Abstract: A method of and apparatus for controlling the efficiency of mixing of a mixer, comprising injecting a chemical into a process fluid flowing in a pipe, mixing the chemical with the process fluid with a mixer operating at a first operation rate, wherein the method comprises further steps of measuring an efficiency of mixing of the chemical and the process fluid within the pipe downstream of the mixer, comparing the measured efficiency of mixing with a predetermined efficiency of mixing range, controlling the operation rate of the mixer so as to adjust the efficiency of mixing to the predetermined efficiency of mixing range. The efficiency of mixing is preferably measured by using a set of electrodes disposed on the periphery of the pipe, and the efficiency of mixing is preferably obtained by the use of electrical impedance tomography.