Doing this in a microflow in version 2.4 of the framework is really hard. Make a Java action that takes a string as parameter and returns a string as well. Put this code between BEGIN USER CODE and END USER CODE:
return inputString.replaceAll("[\\d]", "");
Or upgrade to version 2.5 and do it in a microflow :)
In a microflow:
replaceAll($yourvalue, '[0-9]', '')
Or, if you want to remove integers at the beginning of your string only:
replaceAll($yourvalue, '$[0-9]', '')