ITR Processing Time

i filled itr for AY 2017-18 on 23/03/2018 after due date and e verified also but till date my return is not processed by cpc i have given graviance for the same cpc replied that wait till processing.
so my question is that is there any time limit for processing the return.
more than 1.5 year passed after itr filling but till date my return is pending at cpc
what should i do for that because there was refund claim aprox 50000/ -
pl guide me.