Abstract: An apparatus and method to control a process to replace natural gas with vaporized fuel oil whereby fuel oil is mixed with a gaseous diluent and partially vaporized, liquids separated out, superheated and burned in a natural gas burner without major modification to the burner is disclosed. The control system is:1. a liquid level controller sensing the liquid level in the separator to automatically control the flow of the fuel oil to the vaporizer,2. a ratio flow controller sensing the flow of the fuel oil and of the diluent to the vaporizer to automatically control the flow of the diluent to a set ratio of the flow of the fuel oil,3. a pressure controller sensing the pressure at the vaporizer outlet and downstream overhead to automatically control the heat input to the vaporizer and optionally,4. a flow control valve set to automatically control the flow of the separator overhead to the burner; also,5.

Abstract: A method to replace natural gas with vaporized fuel oil is disclosed. The method, in general, is mixing the fuel oil with a diluent, such as steam, then vaporizing a portion of the mixed fuel oil in a vaporizer, then separating the liquid from the vapor, then maintaining the vapor at from about 50.degree. to 300.degree. F. above the dew point of the mixed vapor and diluent and preferably maintaining the pressure of the mixed vapor and diluent at about 75 to 150 psig, above the pressure downstream of a valve controlling flow of the vapor mixed with diluent, and burning the vapor in a burner designed for natural gas without major modifications to the burner. The temperature and pressure can be maintained by heat from the vaporizer or by adding heat from a superheater.