Patent ID: 6039879
Filing Date: 2000-03-21
Classification: B01D

Abstract:
A method for separating and recovering an objective component from a crude liquid by a membrane in time-lagged multi-stage washing operation, comprising:at least two stages which comprise steps as follows:a mixing step of mixing a washing liquid continuously or intermittently into a crude liquid stored in a container to form a mixture of said crude liquid and said washing liquid in each stage;a separating step of separating said mixture in each stage into a permeated liquid and a residual liquid by passing said mixture through a membrane; anda returning step of returning said residual liquid to said container in each stage;wherein said separating step, and returning step are performed simultaneously;wherein successive ones of said at least two stages are separated by a time lag; andwherein successive ones of said at least two stages use washing liquids at different concentrations, in descending order, of the objective component concentration;obtaining a first permeated liquid by the separating step in a first stage of said at least two stages of a cycle of the time-lagged multi-stage washing operation;obtaining a final residual liquid by the separating step in a final stage of said at least two stages using a final washing liquid which has an objective component concentration of essentially zero; andusing a permeated liquid obtained by a membrane treatment other than the first permeated liquid, as a washing liquid in a later cycle performed on another crude liquid;wherein said later cycle has the same number of stages as in said cycle, andwherein said step of using a permeated liquid is carried out in a last stage of said later cycle.