Slow Cooker Black Bean Soup

1 TB olive oil
1 cup chopped onion
2 carrots, chopped
2 celery, chopped
1 green pepper, chopped
2 cloves garlic, chopped
2 (15 oz) cans black beans, drained & rinsed
1 can (15 oz) diced tomatoes
4 cups vegetable broth
2 bay leaves
1 tsp cumin
1 tsp thyme
cayenne to taste

Stir all ingredients into slow cooker; cook on low 8 hours.  Remove bay leaves.  In blender, puree 2 cups of soup solids; stir back into slow cooker & serve