Systems and methods for supplying gaseous ammonia to serially-connected ammonia cracking units
The present invention relates, in general, to systems and methods for generating hydrogen from ammonia on-board vehicles, where the produced hydrogen is used as a fuel source for an internal combustion engine. The invention provides an expansion valve configured to maintain ammonia in a gaseous state prior to introduction into a cracking system that comprises a heat-exchange cracking unit and electric cracking unit coupled in series which enables reliable hydrogen generation under varying engine operating conditions.
1 . An on-board ammonia cracking system for supplying fuel to an internal combustion engine, the system comprising:
an ammonia tank containing ammonia;
an exhaust heat cracking unit coupled to the ammonia tank, the exhaust heat cracking unit having an exhaust inlet, an exhaust outlet, an ammonia inlet, and a gas outlet, wherein the exhaust heat cracking unit receives exhaust gas from the internal combustion engine via the exhaust inlet, wherein the exhaust gas exits the exhaust heat cracking unit via the exhaust outlet;
an electric cracking unit coupled in series to the exhaust heat cracking unit via only the gas outlet, the electric cracking unit comprising an electric heating element configured to draw electrical current to heat the electric cracking unit to a threshold temperature suitable to perform ammonia cracking;
a temperature control valve positioned upstream of the exhaust heat cracking unit;
a pressure control valve positioned upstream of the exhaust heat cracking unit;
a temperature sensor coupled to the electric cracking unit;
a pressure transducer configured to generate a pressure feedback signal corresponding to pressure of ammonia supplied to the exhaust heat cracking unit;
an injection system coupled to the internal combustion engine;
a supply line coupled between the ammonia tank and the injection system, the supply line providing ammonia from the ammonia tank to the injection system; and
an electronic controller coupled to the temperature control valve, the pressure control valve, the temperature sensor, the pressure transducer, and the electric cracking unit,
wherein, the electronic controller is configured to:
(i) selectively open the temperature control valve, based on a temperature reading from the temperature sensor, to allow downstream flow of ammonia toward the exhaust heat cracking unit, wherein the ammonia is pre-heated in the exhaust heat cracking unit to form pre-heated ammonia;
(ii) control the pressure control valve based on the pressure feedback signal from the pressure transducer; and
(iii) determine, based at least in part on current draw of the electric heating element in the electric cracking unit, whether ammonia exiting the exhaust heat cracking unit has been cracked in the exhaust heat cracking unit,
wherein, if the exhaust gas has reached a temperature sufficient to perform ammonia cracking, the pre-heated ammonia undergoes a cracking process in the exhaust heat cracking unit,
wherein, if the exhaust gas has not reached the temperature sufficient to perform ammonia cracking, the pre-heated ammonia exits the exhaust heat cracking unit via the gas outlet and flows to the electric cracking unit, and the pre-heated ammonia subsequently undergoes the cracking process in the electric cracking unit, and
wherein hydrogen resulting from the cracking process is supplied to the injection system for use as a co-fuel with ammonia from the supply line to power the internal combustion engine.
2 . The system of claim 1 , wherein the exhaust gas flows in a first direction through the exhaust heat cracking unit, and the ammonia flows in a second direction, opposite the first direction, through the exhaust heat cracking unit.
3 . The system of claim 1 , wherein the exhaust gas and the ammonia each flow in the same direction through the exhaust heat cracking unit.
4 . The system of claim 1 , wherein channels are formed in the exhaust heat cracking unit, and wherein discrete catalyst media is deposited in the channels.
5 . The system of claim 4 , wherein interior surfaces of the exhaust heat cracking unit are coated with a catalyst.
6 . The system of claim 1 , wherein the electronic controller is configured to regulate electrical current supplied to the electric heating element based on the temperature reading from the temperature sensor to maintain the electric cracking unit at the threshold temperature suitable to perform ammonia cracking.
7 . The system of claim 1 , wherein the exhaust heat cracking unit includes an exhaust gas channel and an ammonia channel, wherein the exhaust gas channel and the ammonia channel are oriented in a perpendicular fashion to one another.
8 . An on-board ammonia cracking system for supplying fuel to an internal combustion engine, the system comprising:
an ammonia tank containing ammonia;
an exhaust heat cracking unit coupled to the ammonia tank, wherein the exhaust heat cracking unit receives exhaust gas from the internal combustion engine and receives ammonia from the ammonia tank;
an electric cracking unit coupled in series via a single fluid path to the exhaust heat cracking unit, the electric cracking unit including an electric heater configured to draw electrical current to heat the electric cracking unit;
a temperature control valve configured to selectively permit the ammonia to flow downstream toward the exhaust heat cracking unit and the electric cracking unit;
a pressure control valve configured to regulate pressure of the ammonia supplied to the exhaust heat cracking unit;
a temperature sensor coupled to the electric cracking unit;
a pressure transducer configured to generate a pressure feedback signal;
an injection system coupled to the internal combustion engine;
a supply line coupled between the ammonia tank and the injection system, the supply line providing ammonia from the ammonia tank to the injection system; and
an electronic controller coupled to the temperature control valve, the pressure control valve, the temperature sensor, the pressure transducer, and the electric heater, wherein the electronic controller is configured to:
(i) selectively open the temperature control valve, based on a temperature reading from the temperature sensor, to allow downstream flow of the ammonia toward the exhaust heat cracking unit, wherein the ammonia is pre-heated in the exhaust heat cracking unit to form pre-heated ammonia;
(ii) control the pressure control valve based on the pressure feedback signal from the pressure transducer; and
(iii) determine that the exhaust heat cracking unit is performing ammonia cracking when current draw of the electric heater is below a threshold current draw, and determine that ammonia exiting the exhaust heat cracking unit is being cracked in the electric cracking unit when the current draw of the electric heater is above the threshold current draw,
wherein, if the exhaust gas has reached a temperature sufficient to perform ammonia cracking, the pre-heated ammonia undergoes a cracking process in the exhaust heat cracking unit,
wherein, if the exhaust gas has not reached the temperature sufficient to perform ammonia cracking, the pre-heated ammonia exits the exhaust heat cracking unit and flows to the electric cracking unit, and the ammonia subsequently undergoes the cracking process in the electric cracking unit, and
wherein hydrogen resulting from the cracking process flows to the injection system for use as a co-fuel with ammonia from the supply line to power the internal combustion engine.
9 . The system of claim 8 , wherein the ammonia flows in a first channel within the exhaust heat cracking unit and the exhaust gas flows in a second channel within the exhaust heat cracking unit, wherein the first channel and the second channel are oriented perpendicular to each other.
10 . The system of claim 8 , wherein when the ammonia undergoes the cracking process in the electric cracking unit, the ammonia has been pre-heated in the exhaust heat cracking unit before flowing to the electric cracking unit.
11 . The system of claim 8 , wherein the temperature sufficient to perform ammonia cracking ranges from 400° C. to 700° C.
12 . The system of claim 8 , wherein the electric heater is selected from a group consisting of an air process heater, a cartridge heater, a tubular heater, a band heater, a strip heater, an etched foil heater, a thin-film heater, a ceramic heater, a ceramic fiber heater, and a resistance wire.
13 . The system of claim 8 , wherein the exhaust gas flows in a first direction through the exhaust heat cracking unit, and the ammonia flows in a second direction, opposite the first direction, through the exhaust heat cracking unit.
14 . The system of claim 8 , wherein the exhaust gas and the ammonia each flow in the same direction through the exhaust heat cracking unit.
15 . An on-board ammonia cracking system for supplying fuel to an internal combustion engine, the system comprising:
an ammonia tank containing ammonia;
an exhaust heat cracking unit coupled to the ammonia tank, wherein the exhaust heat cracking unit receives exhaust gas from the internal combustion engine and receives the ammonia from the ammonia tank;
an electric cracking unit coupled in series to the exhaust heat cracking unit via a single fluid path such that exhaust gas does not flow from the exhaust heat cracking unit to the electric cracking unit;
a temperature control valve configured to selectively permit the ammonia to flow downstream toward the exhaust heat cracking unit and the electric cracking unit;
a pressure control valve configured to regulate pressure of the ammonia supplied to the exhaust heat cracking unit;
a temperature sensor coupled to the electric cracking unit;
a pressure transducer configured to generate a pressure feedback signal corresponding to pressure of ammonia supplied to the exhaust heat cracking unit;
an injection system coupled to the internal combustion engine;
a supply line coupled between the ammonia tank and the injection system, the supply line providing ammonia from the ammonia tank to the injection system; and
an electronic controller coupled to the temperature control valve, the pressure control valve, the temperature sensor, the pressure transducer, and the electric cracking unit,
wherein the electronic controller is configured to:
(i) selectively open the temperature control valve, based on a temperature reading from the temperature sensor, to allow downstream flow of ammonia toward the exhaust heat cracking, wherein the ammonia is pre-heated in the exhaust heat cracking unit to form pre-heated ammonia;
(ii) control the pressure control valve based on the pressure feedback signal from the pressure transducer; and
(iii) use current draw of the electric cracking unit to determine whether the ammonia exiting the exhaust heat cracking unit has undergone a cracking process in the exhaust heat cracking unit,
wherein the pre-heated ammonia undergoes the cracking process in the exhaust heat cracking unit if the exhaust gas has reached a temperature sufficient to perform ammonia cracking, and
wherein, if the exhaust gas has not reached the temperature sufficient to perform ammonia cracking:
(1) the pre-heated ammonia exits the exhaust heat cracking unit and flows to the electric cracking unit, and
(2) the pre-heated ammonia undergoes the cracking process in the electric cracking unit, and
wherein hydrogen resulting from the cracking process is supplied to the injection system for use as a co-fuel with ammonia from the supply line to power the internal combustion engine.
16 . The system of claim 15 , wherein the electric cracking unit includes an electric heater and wherein the electronic controller is configured to regulate electrical current supplied to the electric heater based on the temperature reading from the temperature sensor to maintain the electric cracking unit at the threshold temperature suitable to perform ammonia cracking.
17 . The system of claim 16 , wherein the electric heater is selected from a group consisting of an air process heater, a cartridge heater, a tubular heater, a band heater, a strip heater, an etched foil heater, a thin-film heater, a ceramic heater, a ceramic fiber heater, and a resistance wire.
18 . The system of claim 15 , wherein the electric cracking unit includes discrete catalyst media deposited within the electric cracking unit.
19 . The system of claim 15 , wherein the temperature sufficient to perform ammonia cracking ranges from 400° C. to 700° C.
20 . The system of claim 15 , wherein channels are formed in the exhaust heat cracking unit, and wherein discrete catalyst media is deposited in the channels.