If for some reason it were absolutely necessary to state the time in the 24-hour-clock way (like, say you're telling someone else what to print, and they have to use it), I suppose saying "nineteen hundred" would be the way to do it (assuming you both already know you are talking about time).
22:30 you'd say "twenty-two thirty", etc.
But again, this is in general completely unnatural.
I agree with the others nineteen hundred (hours). I worked in a non-military international environment and we used the 24 h clock, we said 1900hs gmt +or - 5. As you can see we had to be precise with varying time zones.
For what it's worth in the discussion, I think in English-speaking North America (in Quebec it's different), we encounter the 24-hour clock less frequently than you do in Europe. Train travel for instance is much less widespread here, and train timetables or bus schedules don't even necessarily use that notation in all cases.
Therefore, aside from an international work context like the poster above described, it does indeed feel rather "unnatural" to use it conversationally here, EVEN to resolve ambiguity (we simply use AM or PM for that).
It could still be used jokingly here, to put on a mock military tone, but even then I think we'd tend to do that more for morning hours (in the sense that you have to be up and ready early in the morning in the army) than for evening ones.
And by the way, in this context, 9:00 in the morning, 0900, would be pronounced "oh nine hundred hours".. but I'm not sure whether the insertion of "oh" is insisted on as part of the "joking" usage.
Adding"hours" might be correct in a military context, but not in ordinary British English. 21:43 is only read as "twenty-one forty-three", unless the speaker changes it to twelve-hour notation. I cannot speak for AmE usage, but it seems they don't use the 24-hour clock at all.
If 'hours' is acceptable here, it would only be in military contexts. Unless you are in one of the English speaking armed forces, don't add 'hours'. If you join one of these forces, you'll pretty quickly learn their way of telling the time.