How to run refined search using refinementtoken, keywordquery

I am using keywordquery with refinement. I am able to retrieve the refinmenttoken back from refinementtable but they looks like numbers format, not base 64. And when I pass the token back with RefinementFilters not result is returned,sometimes error out.

Have been looking for days but not able to find any example using keywordquery and refinementoken. Any idea? thanks in advance.