Separation and Purification Technology, Vol.215, 329-334, 2019
Scale-up of ceramic nanofiltration membranes to meet large scale applications
Ceramic nanofiltration (NF) membranes have been used in many small and medium scale applications (10-100 m(2)/plant) to clean and recycle hot water from partial waste water streams of industrial processes. A couple of large scale applications came up where the membrane will not be economically feasible due to the high membrane and module costs. The increase of the membrane surface per membrane element is the best option to reduce the costs, due to the reduced handling as well as the reduced amount of stainless steel. Final target is to use honeycomb supports with a membrane area of 10 m(2)/element instead of 0.25 m(2)/element (conventional 19-channel tubes). The scale-up was performed in 3 stages: 1.3 m(2)/element, 4.5 m(2)/element, 10 m(2)/element. All stages required new handling technologies in all included processing steps due to the size and weight of the elements. In addition, the supports and intermediate layers had to be developed to the same quality level as of the 19-channel tubes to enable the reproducible and defect-free NF-coating. The sol-gel synthesis and membrane inspection had to be scaled up as well. The scale-up to 1.3 m(2)-elements (151 channels) was successful and has already been transferred to production. A pilot plant containing 180 membrane elements and a total membrane area of 234 m(2) has been in operation since January 2017 to clean oily water from oil sand refinery. The scale-up to 4.5 m(2)-elements (559 channels) was demonstrated in lab-scale in 2017. First pilot tests with single elements are in operation. The scale-up to 10 m(2)-elements started in April 2017. With about 1200 channels, it will no longer be possible to get the permeate out from the inner channels. That is why a part of the channels will be plugged on the feed and retentate sides and slit on the permeate side.