A B777 flight crew reported declaring a fuel emergency when they were sent around on approach.

Narrative

ATC directed a missed approach outside of FAF. No reason given due to ATC workload. After the missed approach; ATC initially vectored us for immediate return. ATC then directed a frequency change and we were then given vectors to regain the arrival. We declared minimum fuel due at 11.9k LBS. ATC then directed a climb from 4k to 6k with additional vectors away from the field. Once back on the arrival; we stabilized at 9.0k fuel. Shortly thereafter we received a low fuel EICAS which we accomplished directing us to land with flaps 20. Captain declared emergency fuel at approximately 8.9k remaining when ATC vectored us away from the airport. ATC then told us we could expect a turn to final in two miles. Turn was given and we were cleared for the approach. Changing frequencies we were told if we could not slow to 150kts we would be broken out of sequence. We reminded new Controller that we were emergency aircraft. They came back and told us we would not be broken out but they might have to send another aircraft around. We were now approximately 15 miles out; with @8.5k remaining. Controller switched us to Tower. Checking in with Tower; he told us to slow to 150 for spacing. We reminded him that we were an emergency aircraft and he said this was the first he had heard of it and told us there was another emergency fuel aircraft on a 1.5 mile final. We were cleared to land following another aircraft who was cleared to land after the other emergency fuel plane. At that point we lowered the gear and accomplished an uneventful 20 Flap; 2 engine landing. We touched down with 7.9k fuel remaining. I was pleasantly surprised by the significantly lower fuel burn during final approach while landing with 20 flaps as compared to 25 or 30 Flaps and can see why the irregular procedure directs landing with 20 Flaps.