Combine onion, celery, and 1/4 cup water in a pot over medium-high heat. Saute until tender, about 5 minutes. Stir in yams, tomatoes, garlic, ginger, cumin, coriander, salt, and pepper. Cover with 5 cups water; bring to a boil. Reduce heat to low. Simmer, stirring occasionally, until yams are fork-tender, about 25 minutes. Stir in beans and kale; cook until flavors combine, about 10 minutes more.