Dear

You can to use heat treatment at 93 C for 5 min and filtration by paper filter 

This is Q about separate whey protein no casein proteins. The heat is very best for precipice of whey protein  

Can I use micro filtration of pore size 0.45 micrometer, after that ultra filtration of 10 kDalton and repeated ultra filtration several times? Or any other easy procedure, do you know? Actually my target is to produce Whey protein free milk and use to make yoghurt.

i think  the using method for ppt casein (in dr. hamada answer) can be used as protein in milk is combination between whey and casein protein so why not we get rid of casein and take the supernatent which consider whey protein

The method of WP separation from reconstitue milk shall depend on the milk pretreatment procedure prior to milk spry drying. Depending on the method of milk bacetriological 'preservation' - either by MF + low heat pasteurisation (72-74 deg.C) or simple high temerature pasteursation (applied by the most of the producers.) you can use membrane or thermal +membrane method.

To find out which product you have you shall analyze the content of denaturated whey proteins in your reconstitute milk. The higher the Insolubility Index is the higher temperature had been applied to the milk prior to the spry drying. For more information on the influence of preheating temp. and holding time of the milk before spry drying look at:  http://www.sciencedirect.com/science/article/pii/S0958694604002237 

If you find out that your reconstitute milk is a high temp. pasteursized one that would mean that most of the WP are denatureted and shall be easily retained by MF or centrifugation. You may expect however that these methods would retain also part of the casein particles. For MF I would suggest 0,8 um than 0,45um membranes as 0,45 will cause 40-60 % retention of casein, which means unacceptable product loss. 

If you have low heat milk powder then the easiest way in my opinion would be high temp. pasteurisation of reconstitute milk and further MF/centrifugation. I would avoid using low porosity MF for separation of whey proteins from casein. There is an exisiting techology for >95% separation of whey proteins form casein using ceramic memrbanes  but  this refers fresh skimm milk rather than reconstitute milk. I am afraid that for the reconstitute milk there will be membrane fouling observed as I can not imagine that even low temp. pasterurisation of milk before spry drying does not cause partial denaturation of whey proteins, especially immunoglobulines,which  are the most temperature unstable proteins in milk.