Fuel tank ullage pressure reduction

A method of reducing the pressure in a fuel tank ullage having a higher pressure than atmospheric pressure comprising the steps of

• detecting the pressure in the fuel tank ullage,
• when the pressure exceeds a threshold, heating a catalyst to a temperature at which it catalyzes volatile hydrocarbons,
• withdrawing vapor and air from the fuel tank ullage by means of the pressure differential between the tank ullage and atmospheric pressure by opening a valve in communication with an outlet,
• directing the withdrawn vapor and air to the catalyst for oxidation of the vapor to carbon dioxide and water, and
• discharging the oxidation products and withdrawn air to the atmosphere.

An apparatus for reducing the pressure in a fuel tank ullage having a higher pressure than atmospheric pressure comprising

• a conduit adapted to be connected to the fuel tank ullage and equipped with a controllable valve,
• a pressure sensor adapted for mounting to detect the pressure in the fuel tank ullage,
• a catalyst module having
• an inlet connected to said conduit,
• a catalyst in said module,
• an outlet separated from said inlet by said catalyst,
• a heater disposed to heat said catalyst, and
• a temperature sensor to detect the temperature of said catalyst, and
• a controller adapted to receive inputs from said pressure sensor and said temperature detector and output control signals to said heater to heat said catalyst when said pressure sensor indicates the pressure in the ullage exceeds a threshold and to open said controllable valve to permit withdrawing of volatile hydrocarbons and air from the ullage to said catalyst for oxidation of the volatile hydrocarbons after said temperature sensor indicates said catalyst has reached a temperature at which it catalyzes the oxidation of volatile hydrocarbons to water and carbon dioxide, thereby reducing the pressure in the ullage by oxidation of the volatile hydrocarbons to water and carbon dioxide and release of the water and carbon dioxide and air to atmosphere wherein the volatile hydrocarbons are transported from the fuel tank ullage to the catalyst module by the pressure differential between the tank ullage and atmospheric pressure.

A service station installation comprising

• a fuel storage tank,
• a plurality of fuel dispensers operatively connected to said storage tank to withdraw liquid fuel from the storage tank and each having a vapor recovery system including a vapor recovery pump to return vapors to an ullage in said storage tank, and
• an apparatus for reducing the pressure in said fuel tank ullage including a conduit connected to the fuel tank ullage and equipped with a controllable valve,
• a pressure sensor mounted to detect the pressure in the fuel tank ullage,
• a catalyst module having
• an inlet connected to said conduit,
• a catalyst in said module,
• an outlet separated from said inlet by said catalyst,
• a heater disposed to heat said catalyst, and
• a temperature sensor to detect the temperature of said catalyst, and
• a controller adapted to receive inputs from said pressure sensor and said temperature detector and output control signals to said heater to heat said catalyst when said pressure sensor indicates the pressure in the ullage exceeds a threshold and to open said controllable valve to permit withdrawing of volatile hydrocarbons and air from the ullage to said catalyst for oxidation of the volatile hydrocarbons after said temperature sensor indicates said catalyst has reached a temperature at which it catalyzes the oxidation of volatile hydrocarbons to water and carbon dioxide, thereby reducing the pressure in the ullage by oxidation of the volatile hydrocarbons to water and carbon dioxide and release of the water and carbon dioxide and air to atmosphere.

A method of dispensing fuel comprising

• storing fuel in a fuel storage tank,
• dispensing fuel from one of a plurality of fuel dispensers operatively connected to said storage tank including withdrawing liquid fuel from the storage tank while returning fuel vapor through a vapor recovery pump in the dispenser to an ullage in said storage tank, and
• reducing the pressure in a fuel tank ullage comprising the steps of
• detecting the pressure in the fuel tank ullage,
• when the pressure exceeds a threshold, heating a catalyst to a temperature at which it catalyzes volatile hydrocarbons,
• withdrawing vapor and air from the fuel tank ullage,
• directing the withdrawn vapor and air to the catalyst for oxidation of the vapor to carbon dioxide and water, and
• discharging the oxidation products and withdrawn air to the atmosphere.