Doing ab workouts can help you burn belly fat but just doing ab workouts by itself won't burn much belly fat even though it's a very helpful part of exercising to lose belly fat.
To lose belly fat by doing ab workouts you must also do a combination of aerobic exercises and resistance training, such as lifting weights in order for your body to be able to burn off calories and speed up your bodies metabolism which in turn helps you burn the belly fat.
So as long as you're doing the other exercises with the ab workouts you should be able to quickly burn off the belly fat pretty quickly as long as you stick to the exercise.