CodeIgniter: Session re-created after page reload

I have a system where a session is created for the user after login, the problem is that every access I make to the site a new session is created and the data recorded are deleted, I configured the session as autoload and the settings are :

$config['sess_driver'] = 'files';
$config['sess_cookie_name'] = 'nomequalquer';
$config['sess_expiration'] = 7200;
$config['sess_save_path'] = NULL;
$config['sess_match_ip'] = FALSE;
$config['sess_time_to_update'] = 300;
$config['sess_regenerate_destroy'] = FALSE;

This is the login code:

$user = $this->user_model->doLogin($_POST);
if($user != false){
    $this->session->set_userdata(array('logged' => true, 'user' => $user));
    $_SESSION['sess_id'] = session_id();
    echo json_encode(array('1', $_SESSION));
}else ...

I send session data to record them on the chrome console, redirection is done here:

...
function(data, status, jqXHR){
    if(status == 'success'){
        ...
        var result = JSON.decode(data);
        //debugging
        console.log(result[1]);
        //redirecionamento
        windows.location.replace = <?php echo "'" . base_url(array('admin/usuarios')) . "'"; ?>;
        ...
    }
}
...

On page some/page I put a button that accesses the following code on the server:

$_SESSION[session_id()] = 'hello!';
var_dump($_SESSION);

You can see that the session id changes at all times and the data entered in the login no longer exists. What would be the reason for this?