After an order or decision has been made by the Commission any party to the proceedings may within ten days after service of notice of the entry of the order or decision apply for a rehearing in respect to any matter determined in such proceedings and specified in the application for rehearing, and the Commission may, in case it appears to be proper, grant and hold such rehearing. The Commission shall either grant or refuse an application for rehearing within twenty days, and a failure by the Commission to act upon such application within that period shall be deemed a refusal thereof. If the application be granted the Commission’s order shall be deemed vacated, and the Commission shall enter a new order after the rehearing has been concluded.