A320 FLT CREW HAS CONCERNS WITH ATC HANDLING OF ACFT IN MODERATE ICING CONDITIONS.

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WE WERE BEING VECTORED AT 9000 FT FOR THE APCH TO RWY 34R. THE CTLR TOLD US TO SLOW FROM 210 KTS TO 170 KTS. AT 210 KTS WE WERE PICKING UP MODERATE ICE (1/4 INCH IN ABOUT 5 MINS). I TOLD THE CTLR TO BE ADVISED WE WERE CARRYING A LARGE LOAD OF ICE AND 170 KTS WOULD REQUIRE FLAP EXTENSION WHICH REMOVES OUR ICE PROTECTION ON THE LEADING EDGE. HE TOLD US ROGER AD HANDED US OVER TO TWR AND TOLD US TO HOLD 170 KTS. WE WERE PICKING UP ICE RAPIDLY SO WE DID NOT SLOW UNTIL GS INTERCEPT. WE WERE QUERIED AGAIN TO SLOW AND I TRIED TO EXPLAIN WE WERE CARRYING A LARGE LOAD OF ICE (ABOUT 1/2 INCH NOW). HE HAD 3 MI ON THE PRECEDING ACFT BUT PULLED US OUT OF THE APCH AND VECTORED US BACK FOR ANOTHER APCH. THIS TIME WE LANDED NO PROB AND REMAINED AT 210 KTS CLEAN UNTIL GS INTERCEPT WITH WAI ON. WE LANDED WITH 5/8 INCH OF ICE OR MORE ON THE UNPROTECTED AREAS. I WOULD LIKE ATC TO BE ADVISED THAT OUR PROCS CALL FOR US TO REMAIN CLEAN AS LONG AS POSSIBLE TO PROVIDE WAI WHICH REQUIRES HIGHER VECTOR SPDS 200+ KTS AND MORE SPACING WITH PRECEDING ACFT (IF THEY ARE OPERATING AT SLOWER SPDS) WHEN IN MODERATE ICING CONDITIONS. SUPPLEMENTAL INFO FROM ACN 691020: WE WERE SWITCHED TO ANOTHER FREQ AND IMMEDIATELY TOLD TO SLOW TO 170 KTS; AND AGAIN WE ADVISED UNABLE DUE TO ICING CONDITIONS. ANSWER; 'FINE; WHEN YOU GET TO 3 MI; WE'LL BREAK YOU OUT.' AT THE TIME WE WERE CARRYING ABOUT 1/2 INCH OF ICE ON OUR PROBE; INDICATING MODERATE MIXED ICING. APCH BROKE US OUT AT 3 1/2 MI AND VECTORED FOR ANOTHER APCH AT 200 KTS; AND LANDED SUCCESSFULLY.