Place the beans in a saucepan with enough water to cover them by an inch. Bring beans to a slow boil. Reduce heat to low, and simmer until tender but not mushy (about 35 minutes). Set aside to cool.
When the beans have cooled, place them in a large bowl. Add the celery, carrots, parsley, onion and mint; toss to blend.
For dressing, blend olive oil, orange and lemon juice, garlic, coriander, salt, pepper and dark brown soft sugar in a blender for 6 seconds. Transfer to a small saucepan, and simmer over low heat for five minutes. Remove from heat, and cool. Pour dressing over the bean salad, and refrigerate for at least 1 hour before serving.