Is there a way in photoshop to convert k values to alpha values?

This is i found from Internet

You can load the luminosity of an image as a selection, then create a mask and invert the mask. It sounds to me like you really want luminosity, not "white" data.

1. Command/Ctrl the RGB Channel Thumbnail in the Channels Panel. To load a selection. (This essentially loads the L channel from the L*A*B data)
2. Highlight the image layer in the Layer Panel
3. Click the Add Mask button at the bottom of the Layers Panel
4. Choose Image > Adjustments > Invert to invert the mask

Done. You can then use some Levels or Curves adjustments to fine tune the mask.