You see, if your wife is not interested to have any physical relationship despite having the opportunity to do so, it means, in my opinion, her impotency in respect of you. The impotency may not be universal in her case and also it may not be physical problem. Still, she may have got certain psychological problems qua (in respect of) you in consumation. If that is the case, instead of going to "divorce" you can opt for "annulment" of marriage. This annulment will take away the burden of providing maintenance to her and also gives you opportunity to file a case within one year of the solemnization of marriage.
If you opt for divorce, you have to wait atleast one year from the date of marriage to file a case under "cruelty" ground.
The time that will take depend upon the case log of the particular court, where you file the case. Generally, it will not be less than 3 years.