Remove files the sessions

Hello,

About removing files in the folder sessions? How is it done automatically? Here it is not working. The sessions folder is big.

$config['sess_driver'] = 'files';
$config['sess_cookie_name'] = 'ci_sessions';
$config['sess_expiration'] = 2000;
$config['sess_expire_on_close'] = FALSE;
$config['sess_save_path'] = FCPATH.'application/sessions';
$config['sess_match_ip'] = TRUE;
$config['sess_time_to_update'] = 300;
$config['sess_regenerate_destroy'] = FALSE;

Thanks.