Reading large Excel files

I need to import a relatively large .xlsx file (40,000 rows, 15 columns) into my database.
I tried the PHPExcel library, but it gives a memory error.
I've found a library that should be able to read a big file row by row: Spout.

I created a folder named "spout" in application/third_party.
In that folder, the directory structure of Spout looks like this:
Autoloader
Common
Reader
Writer

In the application/libraries folder, I created a file named Spout.php, with this contents:

PHP Code:

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
 
require_once APPPATH . '/third_party/spout/Autoloader/autoload.php';
use Box\Spout\Reader\ReaderFactory;
use Box\Spout\Common\Type;    
        
class Spout { 
    public function __construct() { 
    
    } 
} 


In my Import.php controller, I have this:

PHP Code:

$this->load->library('spout');
$reader = ReaderFactory::create(Type::XLSX); // for XLSX files 


But CI gives an error:

Code:

A PHP Error was encountered
Severity: Error
Message: Class 'ReaderFactory' not found
Filename: controllers/Import.php
Line Number: 346

I'm making some fundamental mistake, I guess. Who can help me to get this working?