Hi,
John is correct and there should be no limit to number of Instance.
Read
Consequently, an obvious way around this problem is to use multiple, named, instances on the same server. In doing so youll
need to potentially constrain access to processors (i.e., set affinity typically to distinct NUMA nodes for best results) and watch out for situations where you might run into IO contention, but, otherwise, the use of multiple instances CAN be one way to
get the most bang for your buck out of SQL Server Standard Edition licenses provided youre willing to babysit and tune your workloads as necessary.
and further check
http://sqlmag.com/blog/sql-server-standard-edition-licensing-limits