US 5,398,497 A · Method using gas-gas heat exchange with an intermediate direct contact heat exchange fluid

Abstract

A method for burning slurry, liquid, or gaseous fuels at elevated pressures allows lower quality fuels to yield more energy and higher quality energy due to increased dew point temperatures in flue gases and high temperature heat exchange. The combination of elevated pressures and oxygen rich oxidant allows increased waste heat recovery, higher quality heat recovery, and substantially reduced air pollution. Turbochargers operated by flue gas and pressurized air, force the oxygen into the combustion chamber at increased pressures. Oxygen permeable membranes lower levels of nitrogen and reduce pollution by enhancing the stripping of pollutants from the flue gas and by the absolute reduction of flue gas exhaust. Latent heat recovery and water dilution of combustion mixtures are important aspects of the embodiments of this invention; both are enhanced by the vaporization of influent liquids while contacting influent gasses. High temperature heat exchange is facilitated by direct contact heat exchange means. Substantially reduced pollution levels allow operation in residential and downtown areas where cogenerated heat and coolant can be utilized. This method is particularly useful for converting garbage or sewage into electricity and for increased biomass combustion efficiency; however, advantages of this method can also be realized for most conventional fuels.

Claims8

Dependent claims

A high efficiency method using direct contact heat exchange for converting fuel into work, comprising the steps of:

compressing oxygen containing gas,
heating the said oxygen containing gas by direct contact of said oxygen containing gas with a heat exchange fluid containing less than 15 weight percent water and having a water-free partial vapor pressure of less than one atmosphere at 300 C.,
contacting said oxygen containing gas with said heat exchange fluid in a heat exchange vessel to provide a heated gas having a temperature at least 150 C. greater than said oxygen containing gas,
pumping said heat exchange fluid to a second heat exchange vessel,
mixing said heated gas with a fuel in an expectative amount to sustain a combustion reaction to provide a fuel mixture,
combusting said fuel mixture to-provide a reaction product gas having a greater temperature than said heated gas,
expanding said reaction product gas to provide shaft work and to provide a flue gas having less enthalpy than said reaction product gas,
cooling said flue gas by directly contacting said flue gas with a heat exchange fluid in a second heat exchange vessel, and
circulating said heat exchange fluid between said first heat exchange vessel and said second heat exchange vessel to increase the enthalpy of the said heat exchange fluid in said second vessel and to decrease the enthalpy of the said heat exchange fluid in the first heat exchange vessel.

6 more elements

Dependencies are inferred from the claim text.

Method using gas-gas heat exchange with an intermediate direct contact heat exchange fluid

Life of this patent

Method using gas-gas heat exchange with an intermediate direct contact heat exchange fluid

Life of this patent

Abstract

Claims8