Kev siv lub hnab ntim valve:

alve hnab yog tsuas yog siv rau ntim khoom noj hmoov, tshuaj hmoov, chiv, khoom siv hluavtaws, nplej, ntsev, minerals thiab lwm yam khoom siv hmoov lossis granular thiab cov khoom siv tau yooj yim. Nws yog tshwj xeeb tshaj yog haum rau export lag luam thiab tuaj yeem txhim kho qib ntim ntawm cov khoom.