Remove active user to console - HELP

Hello
I have a RB that also use as a fts server
I have notice that sometime a remote unit doesn’t shutdown the connection in a good way and it said that the user is still online
how can I remove them ?? (and not by reboot the unit?)
is there any rule I can make in firewall to remove\close users after 20 min whule using ftp?
all my ftp connection shuld not take more them 5 min top

as you can see it “save” me many ftp connection from more then 1 month - I don’t need this
and now new connection can’t be created

 0    mar/27/2017 15:45:45 admin   80.187.105.155                                
 1    mar/27/2017 15:47:43 admin   80.187.105.155                                
 2    mar/27/2017 15:49:44 admin   80.187.105.155                                
 3    mar/27/2017 15:51:43 admin   80.187.105.155                                
 4    mar/27/2017 15:53:44 admin   80.187.105.155                                
 5    mar/27/2017 15:55:43 admin   80.187.105.155                                
 6    mar/27/2017 15:57:43 admin   80.187.105.155                                
 7    mar/27/2017 15:59:44 admin   80.187.105.155                                
 8    mar/27/2017 16:01:45 admin   80.187.105.155                                
 9    mar/27/2017 16:03:44 admin   80.187.105.155                                
10    mar/27/2017 16:05:44 admin   80.187.105.155                                
11    mar/28/2017 17:30:50 admin   80.187.101.92                                 
12    mar/28/2017 17:32:50 admin   80.187.101.92                                 
13    mar/28/2017 17:34:50 admin   80.187.101.92                                 
14    mar/28/2017 17:36:50 admin   80.187.101.92                                 
15    mar/28/2017 17:38:49 admin   80.187.101.92                                 
16    mar/28/2017 17:40:49 admin   80.187.101.92                                 
17    mar/28/2017 17:42:50 admin   80.187.101.92                                 
18    mar/28/2017 17:44:49 admin   80.187.101.92                                 
19    mar/28/2017 17:46:49 admin   80.187.101.92                                 
20    mar/28/2017 17:48:49 admin   80.187.101.92

Thanks ,