The best way to refine searches is to use the filters in the right column, both to narrow down the ingredient search and to exclude ingredients. The filters are a direct match to the database ingredient whereas the word search looks for the word in recipe title, book title, author name and ingredients. For example a search by chicken in word search will also show recipes containing chicken stock, chicken sausages, etc whereas selecting chicken pieces under Poultry in filters will only show recipes containing chicken thighs/breasts/etc).There are also filters for all the category tags such as ethnicity, recipe type, special diet, etc. You can learn more about filters in Tutorial #4, accessed from the green Need Help? button at bottom right (not available on phones). There is also this Help section.
So in your search you want to exlude green beans but include dried beans. You would select Long beans under Green vegetables then exclude them by clicking the + to turn it to a -. Then you would select Beans under Grains & pasta (I know beans are neither but it was sometimes difficult to apportion ingredients into a limited number of top level sections). If you ever aren't sure which filter an ingredient will fall under enter the name in the green search box then see which filter has the highest number (the recipes that match that name). This is those filters applied to the Library Online Recipes. You can then apply further filters to reduce the number down e.g. Soups under Recipe types/Dish types or Salads under Recipe types/Side dishes. And don't forget about using the Sort options to mix up what appears at the top - my favorite Sort is Buzz which shows the recipes with the most Notes and Ratings at the top.