In a slow cooker, combine the beans, andouille, celery, ham shank, onions, bell peppers, chili powder, cumin, garlic powder, cayenne, onion powder, paprika, brown sugar and 2 teaspoons salt. Add the chicken stock and 2 cups water and stir to mix.
Cook on the high setting until the beans are tender, 6 to 8 hours. Season with salt. Serve with rice, topped with scallions.