Any government in a democracy has to live with the realities of...

Any government in a democracy has to live with the realities of politics ACB and slugging everyone with a tax without compensation would see them tossed out at the next election.
It would also IMO place a greater burden on low income earners on the breadline than wealthy individuals who will barely notice it so not good socially.
It's important to remember though that both rich and poor can minimize the amount of carbon tax they pay by consuming less carbon based energy.
As to what happens with tax left over after compensation I saw in the media a figure of about two billion being bandied around as what is likely to be available for developing greener fuels etc. I would hope that this money will be tied to only being spent on such things, we will have to await the release of the plan to find out.
Dave R.