It cannot be considered a valid divorce since you never had the slightest intention of divorce. It is not different from actions of a person who is not in full possession of his senses. The Prophet, peace be upon him, is reported to have said, “There is no divorce if a person is in a state of mental blockage”. Anger can lead to such a state, leading a person to do things he never intended to do in the first place. Therefore, based on the rulings of Imams such as Ibn al-Qayyim, Ibn Abideen, etc. these thoughtless words do not constitute divorce.

Having said this, I must also point that you need to ask forgiveness of Allah and firmly resolve to never use the word of talaq again. It is akin to playing with the Laws of Allah. You may also do well to give some charity by way of compensation (like feeding ten poor people). If you are not able to deal with anger, it will be an excellent idea to take an anger management course; or ask a professional counselor to advice you on this matter. Your family physician may advise you where to get help. In the meantime, never fail to turn to Allah for help by offering the following supplications:

allaahumma innee as’aluka al-thabaata fi al-amri wa al-‘azeemata ala al-rrushdi; allaahumma yaa muqalliba al-quloobi thabbit qalbee alaa al-haqqi

(O Allah, I ask of You to keep me steadfast (on the straight path), and grant me firm adherence to the right conduct (in words and actions); O Allah, You are the twister/turner of hearts; so make my heart firm on the truth).

Also never forge to pray in these blessed days:

Allaahumma innaka afuwwun tuhibbu al-‘afwa fa’fu annee

(O Allah, You are Forgiving; You love to forgive, and so forgive (my sins) for me).