If you have multiple IP addresses and you want to make curl request using non-default IP, you can do it by setting CURLOPT_INTERFACE option:
curl_setopt ($ch, CURLOPT_INTERFACE, '18.104.22.168');
This will work only if you really have that another IP. If you do not have extra IPs, and your only IP is banned already, you need proxies.
If you want to forge your IP address, curl is wrong tool, too.