My Ceiling Fan is running very slow with 220 v ac power supply. I have replaced its 2.2 uf capacitor with 3.5 uf capacitor, now it is running fast, my question is that: Is it safe to use this 3.5 uf capacitor instead of a 2.2 uf (company original fitted) capacitor, in my ceiling Fan.

I would try to get something closer like 2.5uf or 3uf.

Ceiling Fan Capactors - Troubleshooting and Resources - Ceiling Fans 'N More (http://www.ceiling-fans-n-more.com/ceiling-fan-capacitors.php)