Method of starting up a direct heating system for the flameless combustion of fuel and direct heating of a process fluid

A method of starting up a direct heating system comprising a fuel introduction zone, a combustion zone and a process zone that is in heat exchange relationship with said combustion zone, said method comprises:

• passing a hot oxidant fluid through said combustion zone for a warm-up time period sufficient to raise the temperature of said direct heating system to a desired temperature;
• after said desired temperature is reached, passing a process stream comprising a process fluid through said process zone for a second time period sufficient to raise the temperature of said direct heating system to a second desired temperature;
• and
• after said second desired temperature is reached, passing a fuel fluid comprising a fuel through said fuel introduction zone.

A method of starting up a direct heating system comprising a fuel introduction zone, a combustion zone and a process zone that is in heat exchange relationship with said combustion zone, said method comprises:

• passing a hot oxidant fluid through said combustion zone for a warm-up time period sufficient to raise the temperature of said direct heating system to a desired temperature;
• and
• after said desired temperature is reached, passing steam through said process zone for a second time period sufficient to raise the temperature of said direct heating system to a second desired temperature;
• and
• after said desired temperature and said second desired temperature are reached, passing a fuel fluid comprising a fuel through said fuel introduction zone.

A method of starting up a direct heating device, said method comprises:

• providing a direct heating device having a fuel introduction zone, a combustion zone and a process zone that is in heat exchange relationship with said combustion zone;
• prior to the introduction of a fuel fluid into said combustion zone, passing an oxidant fluid, having a high temperature, through said combustion zone for a warm-up time period sufficient to raise the temperature of said direct heating device to a desired temperature;
• passing superheated steam through said process zone;
• prior to the introduction of said fuel fluid into said fuel introduction zone, passing steam through said fuel introduction zone;
• introducing said fuel fluid at an incrementally increasing rate into said fuel introduction zone with said steam to a desired fuel fluid introduction rate and, thereafter, ceasing said passing of said steam through said fuel introduction zone;
• and
• passing a process fluid with said superheated steam through said process zone and, thereafter, ceasing said passing of said superheated steam through said process zone.