If this trash can icon is disappeared you can take following steps to get it back:
1. Login to blogger then check.
2. For firefox browser go to Tools > Clear recent history > Clear cache.
3. Use another web browser.
4. Temporary disable firewall and other security settings on your PC.
5. Change Template.
If above procedure is not working then follow surely working procedure.
Create delete comment link for blogger post without trash can icon!
1. Getting blog ID.
Create the new post on the blog from where you want to delete the comments. Check the address bar. There is the blog ID. e.g. http://www.blogger.com/post-create.g?blogID=5143535933889549339
Here blog ID is 5143535933889549339
Go to the comment you want to delete. Bellow the name of the commenter there is the "timestamp" of that comment Right click on it and select Copy Link Location or Copy Shortcut and paste it to Notepad file.
Here Comment ID is 5071702384565967848
3. Creating Delete Comment Link
Copy and paste following code to Notepad.
Delete amp; from above link.
Now copy and paste this link to your browser and delete the comment easily.