Vehicle-mounted ammonia hydrogen production system

Abstract

The invention discloses a vehicle-mounted ammonia hydrogen production system, belongs to the technical field of vehicle-mounted ammonia hydrogen production, and solves the technical problems that the existing vehicle-mounted ammonia hydrogen production method cannot fully recycle high-pressure ammonia energy and cannot use air energy. The system comprises a liquid ammonia tank, an ammonia hydrogen production heat exchange catalytic reactor, an engine and a controller, the liquid ammonia tank is connected with the ammonia hydrogen production heat exchange catalytic reactor through an ammonia gas pipe, the engine is connected with the ammonia hydrogen production heat exchange catalytic reactor through an exhaust pipe, and the ammonia gas pipe is sequentially provided with a control valve, a first heat exchanger, a turbine generator, a large-area heat exchanger and a second heat exchanger. The turbine generator is electrically connected with the vehicle-mounted storage battery, the large-area heat exchanger is connected with a variable-frequency air blower through an air pipe, the engine is connected with the first heat exchanger through a cooling water pipe, and the ammonia hydrogen production heat exchange catalytic reactor is connected with the second heat exchanger through a nitrogen hydrogen pipe. High-pressure ammonia gas energy and air energy can be fully recycled and used through the turbine generator and the large-area heat exchanger.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle-mounted ammonia hydrogen production, and more particularly, to a vehicle-mounted ammonia hydrogen production system. Background Art

[0002] The principle of on-board ammonia-to-hydrogen production is that liquid ammonia stored in a liquid ammonia tank is reduced in pressure by a pressure reducing valve and then converted into hydrogen and nitrogen through a high-temperature ammonia-to-hydrogen heat exchange catalytic reactor. Currently, the entire process is achieved by heating the ammonia using high-temperature engine cooling water and the ammonia-to-hydrogen heat exchange catalytic reactor using engine exhaust.

[0003] However, the existing technology has the following problems: 1) It fails to utilize the energy in the air, especially the energy of high-temperature air in summer; 2) It fails to utilize the energy of ammonia from a high-pressure state (liquid ammonia tank pressure is as high as 10 bar) to a low-pressure state (1 bar atmospheric pressure), and this part of energy is lost in vain. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art. The purpose of the present invention is to provide an on-vehicle ammonia hydrogen production system that can fully recover high-pressure ammonia energy and use air energy.

[0005] The technical solution of the present invention is: a vehicle-mounted ammonia hydrogen production system, comprising a liquid ammonia tank, an ammonia hydrogen production heat exchange catalytic reactor, and an engine and a controller. The liquid ammonia tank is connected to the ammonia inlet of the ammonia hydrogen production heat exchange catalytic reactor through an ammonia pipe, and the engine is connected to the exhaust inlet of the ammonia hydrogen production heat exchange catalytic reactor through an exhaust pipe. The ammonia pipe is sequentially provided with a control valve, a first heat exchanger, a turbine generator, a large-area heat exchanger, and a second heat exchanger from one end of the liquid ammonia tank to one end of the ammonia hydrogen production heat exchange catalytic reactor. The turbine generator is electrically connected to an on-board battery, the large-area heat exchanger is connected to a variable-frequency blower through an air pipe, the engine is connected to the first heat exchanger through a cooling water pipe, the nitrogen-hydrogen outlet of the ammonia hydrogen production heat exchange catalytic reactor is connected to the second heat exchanger through a nitrogen-hydrogen pipe, and the controller is electrically connected to the control valve and the variable-frequency blower.

[0006] As a further improvement, the air pipe at the output end of the large-area heat exchanger is connected to a cooling coil, and the cooling coil is installed at the air outlet of the automobile air-conditioning system.

[0007] Furthermore, a second temperature sensor and an auxiliary electric heating tube are provided in the ammonia-to-hydrogen heat exchange catalytic reactor, and the controller is electrically connected to the second temperature sensor and the auxiliary electric heating tube.

[0008] Furthermore, the exhaust pipe is provided with a bypass pipe connected in parallel with the ammonia-to-hydrogen heat exchange catalytic reactor, the bypass pipe is provided with a bypass regulating valve, and the controller is electrically connected to the bypass regulating valve.

[0009] Furthermore, the heat transfer capacity of the large-area heat exchanger through convection is calculated as follows:

[0010] Q = α·A·ΔT (Formula 1)

[0011] In formula 1, Q is the heat transfer rate of convection heat transfer; α is the convection heat transfer coefficient between air and radiator; A is the heat transfer surface area of ​​radiator; ΔT is the temperature difference, that is, the temperature difference between low-temperature ammonia and normal temperature air.

[0012] Furthermore, the turbine outlet temperature and turbine work of the turbine generator are calculated as follows:

[0013] The calculation formula for the turbine outlet temperature is:

[0014]

[0015] Wherein, T1 is the inlet temperature, T2 is the outlet temperature, P1 is the inlet pressure, P2 is the outlet pressure, γ is the specific heat ratio, γ = 1.3;

[0016] The calculation formula for turbine work is:

[0017]

[0018] W=W 理论 ×k (Formula 4)

[0019] Among them, W 理论 is the theoretical work of the turbine, h1 is the specific enthalpy of ammonia inlet, h2 is the specific enthalpy of ammonia outlet, is the mass flow rate, W is the work done by the turbine, k is the efficiency, k=60%.

[0020] Furthermore, the air heat exchange outlet temperature of the large-area heat exchanger is calculated as follows:

[0021] Air outlet temperature:

[0022] T air out =T air in +j×(T nh3 in -T air in ) (Formula 5)

[0023] Ammonia outlet temperature:

[0024] T nh3 out =T nh3 in +j×(T airin -T nh3 in ) (Formula 6)

[0025] Air demand:

[0026] m air =m nh3 ×Q nh3 ÷(C p air ×ΔT air ) (Formula 7)

[0027] Among them, T airout is the air outlet temperature, T nh3out is the ammonia outlet temperature, m air is the air demand, m nh3 is the ammonia demand, Q nh3 is the heat absorbed by ammonia through a large area heat exchanger, C pair is the specific heat capacity of air, T airin is the air inlet temperature, T nh3in is the ammonia inlet temperature, ΔT air =T airin -T airout , j is the heat exchange efficiency, j = 0.85.

[0028] Beneficial effects

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. Compared with the prior art of reducing the pressure of liquid ammonia to gasification through a pressure reducing valve, the present invention reduces the pressure of high-pressure ammonia to low-pressure and low-temperature gas-liquid two-phase ammonia through a turbine generator, which can fully recover the energy released by the high-pressure ammonia during the pressure reduction process.

[0031] 2. Compared with the prior art of directly heating ammonia with high-temperature engine cooling water, the present invention first uses ambient air through a large-area heat exchanger to heat the low-temperature ammonia, and then heats the ammonia with high-temperature engine cooling water, which can fully utilize the thermal energy in the air. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a diagram of the architecture of the present invention;

[0033] Figure 2 This is a schematic diagram of providing a cooling water bypass pipe in the cooling water pipe of the present invention.

[0034] Among them: 1-liquid ammonia tank, 2-ammonia hydrogen production heat exchange catalytic reactor, 3-engine, 4-ammonia pipe, 5-exhaust pipe, 6-control valve, 7-turbine generator, 8-large area heat exchanger, 9-first heat exchanger, 10-second heat exchanger, 11-on-board battery, 12-air pipe, 13-variable frequency blower, 14-cooling water pipe, 15-first temperature sensor, 16-nitrogen-hydrogen pipe, 17-cooling coil, 18-second temperature sensor, 19-auxiliary electric heating pipe, 20-bypass pipe, 21-bypass regulating valve, 22-cooling water bypass pipe, 23-cooling water bypass regulating valve. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the specific embodiments in the accompanying drawings.

[0036] See Figure 1-Figure 2 A vehicle-mounted ammonia-to-hydrogen system includes a liquid ammonia tank 1, an ammonia-to-hydrogen heat exchange catalytic reactor 2, an engine 3, and a controller, which is an ECU or onboard computer. The liquid ammonia tank 1 is connected to the ammonia inlet of the ammonia-to-hydrogen heat exchange catalytic reactor 2 via an ammonia pipe 4, and the engine 3 is connected to the exhaust inlet of the ammonia-to-hydrogen heat exchange catalytic reactor 2 via an exhaust pipe 5. The ammonia pipe 4, running from one end of the liquid ammonia tank 1 to one end of the ammonia-to-hydrogen heat exchange catalytic reactor 2, is equipped with a control valve 6, a first heat exchanger 9, a turbine generator 7, a large-area heat exchanger 8, and a second heat exchanger 10, in this order. The turbine generator 7 is electrically connected to an onboard battery 11, and the large-area heat exchanger 8 is connected to a variable-frequency blower 13 via an air pipe 12. The onboard battery 11 provides power to the variable-frequency blower 13. The engine 3 is connected to the first heat exchanger 9 via a cooling water pipe 14, and the nitrogen-hydrogen outlet of the ammonia-to-hydrogen heat exchange catalytic reactor 2 is connected to the second heat exchanger 10 via a nitrogen-hydrogen pipe 16. The controller is electrically connected to the control valve 6 and the variable frequency blower 13 .

[0037] During actual operation, the controller sends a control signal to the control valve 6, the control valve 6 opens, and the high-pressure liquid ammonia passes through the first heat exchanger 9 to obtain high-pressure ammonia gas. The high-pressure ammonia gas passes through the turbine generator 7 and is converted into low-pressure and low-temperature ammonia gas. The low-pressure and low-temperature ammonia gas passes through the large-area heat exchanger 8 to exchange heat with the heat in the air, and the temperature of the ammonia gas increases. The ammonia gas is then heated by the second heat exchanger 10 and then enters the ammonia-hydrogen heat exchange catalytic reactor 2. The high-temperature exhaust gas of the engine 3 (the exhaust gas temperature is as high as 300°C to 600°C) enters the ammonia-hydrogen heat exchange catalytic reactor 2 for heating, so that the ammonia gas is converted into nitrogen-hydrogen product gas. The hydrogen production reaction needs to be carried out at a high temperature (350-450°C).

[0038] Furthermore, the air temperature is greatly reduced after heat exchange, and a cooling coil 17 can be connected to the air pipe 12 at the output end of the large-area heat exchanger 8, that is, the air pipe 12 is connected to the cooling coil 17 through a three-way valve or a reversing valve. The cooling coil 17 is installed at the air outlet of the automobile air-conditioning system. In summer, it can be used to cool the air-conditioning system of the entire vehicle, further reducing the energy consumption of the entire vehicle. In winter, when cooling is not required, the low-temperature air does not pass through the cooling coil 17 and is directly discharged.

[0039] Furthermore, a second temperature sensor 18 and an auxiliary electric heating tube 19 are provided within the ammonia-to-hydrogen heat exchange catalytic reactor 2. The controller is electrically connected to these two elements, and the onboard battery 11 provides power to the auxiliary electric heating tube 19. When the temperature detected by the second temperature sensor 18 is lower than the temperature required for the catalytic reaction, such as when the engine 3 is idling for an extended period or operating at low load, resulting in a low exhaust temperature, the auxiliary electric heating tube 19 can heat the ammonia-to-hydrogen heat exchange catalytic reactor 2 to the temperature required for the ammonia catalytic reaction, thereby ensuring the normal operation of the ammonia catalytic reaction.

[0040] Furthermore, exhaust pipe 5 is provided with a bypass pipe 20 connected in parallel with ammonia-to-hydrogen heat exchange catalytic reactor 2. Bypass pipe 20 is equipped with a bypass regulating valve 21, and the controller is electrically connected to bypass regulating valve 21. When engine 3 operates at high load for a long time, the exhaust temperature is too high (exhaust temperature can reach up to 600°C), which may damage ammonia-to-hydrogen heat exchange catalytic reactor 2. In this case, the controller controls the opening of bypass regulating valve 21 through PID regulation. Under the premise of ensuring the temperature required for the catalytic reaction, it prevents some exhaust gas from passing through ammonia-to-hydrogen heat exchange catalytic reactor 2, thereby preventing damage caused by excessive temperature.

[0041] Furthermore, the cooling water pipe 14 at the output end of the first heat exchanger 9 is provided with a first temperature sensor 15, the cooling water pipe 14 is provided with a cooling water bypass pipe 22 connected in parallel with the first heat exchanger 9, the cooling water bypass pipe 22 is provided with a cooling water bypass regulating valve 23, and the controller is electrically connected to the cooling water bypass regulating valve 23, as shown in FIG. Figure 2 As shown, since the heat of the engine 3 cooling system is utilized, in order to ensure the stable operation of the engine 3, the controller obtains the water temperature output from the cooling water pipe 14 in real time through the first temperature sensor 15. Based on the water temperature, the controller controls the opening of the cooling water bypass regulating valve 23, allowing some high-temperature cooling water to pass through the cooling water bypass pipe 22 and merge with the cooling water that has undergone heat exchange, so that the water temperature is within the set range.

[0042] The heat transfer of the large-area heat exchanger 8 through convection is calculated as follows:

[0043] Q = α·A·ΔT (Formula 1)

[0044] In formula 1, Q is the heat transfer rate of convection heat transfer; α is the convection heat transfer coefficient between air and radiator; A is the heat transfer surface area of ​​radiator; ΔT is the temperature difference, that is, the temperature difference between low-temperature ammonia and normal temperature air.

[0045] The turbine outlet temperature and turbine work of the turbine generator 7 are calculated as follows:

[0046] The calculation formula for the turbine outlet temperature is:

[0047]

[0048] Where T1 is the inlet temperature, T2 is the outlet temperature, P1 is the inlet pressure, P2 is the outlet pressure, γ is the specific heat ratio, Defined as constant pressure specific heat C p and constant volume specific heat C v In this embodiment, γ=1.3.

[0049] For example, liquid ammonia flow rate: 100 kg / h; inlet state: 10 bar (1 MPa), 25°C (compressed liquid); outlet pressure: 1 bar (0.1 MPa), it can be calculated from Formula 2 that T2 = -99°C.

[0050] The calculation formula for turbine work is:

[0051]

[0052] W=W 理论 ×k (Formula 4)

[0053] Among them, W 理论 is the theoretical work of the turbine, h1 is the specific enthalpy of ammonia inlet, h2 is the specific enthalpy of ammonia outlet, is the conversion factor, W is the turbine work, k is the loss coefficient, k=60%.

[0054] According to the specific enthalpy of ammonia, the specific enthalpy of the inlet (10 bar, 25 ° C) is h1 = 332.5 kJ / kg, and the specific enthalpy of the outlet (1 bar, -99 ° C) is h2 ≈ 1200 kJ / kg. According to formula 3, W 理论 =100×(1200-332.5)=24.1kW. That is, the theoretical work capacity is 24.1kW.

[0055] Considering that the process is not completely isentropic and there are losses in resistance, heat transfer, and efficiency, the actual work can be conservatively estimated as 60% (i.e., k = 60%). The actual work of this process is expected to be W = 24.1 × 60% = 15 kW. Affected by efficiency and heat transfer, based on empirical evaluation, the outlet temperature is increased from -99°C to -80°C.

[0056] Based on the simplified heat exchanger efficiency calculation formula T h,in is the inlet temperature of the hot fluid,

[0057] T h,out is the outlet temperature of the hot fluid, T c,in is the cold fluid inlet temperature, and the air heat exchange outlet temperature of the large area heat exchanger 8 is calculated as follows:

[0058] Air outlet temperature:

[0059] T air out =T air in +j×(T nh3 in -T air in ) (Formula 5)

[0060] Ammonia outlet temperature:

[0061] T nh3 out =T nh3 in +j×(T air in -T nh3 in ) (Formula 6)

[0062] Air demand:

[0063] m air =m nh3 ×Q nh3 ÷(C p air ×ΔT air ) (Formula 7)

[0064] Among them, T airout is the air outlet temperature, T nh3out is the ammonia outlet temperature, m air is the air demand, m nh3 is the ammonia demand, Q nh3 is the heat absorbed by ammonia through the large-area heat exchanger (8), C pair is the specific heat capacity of air, T airin is the air inlet temperature, T nh3in is the ammonia inlet temperature, ΔT air =T airin -T airout , j is the heat exchange efficiency. In this embodiment, j=0.85.

[0065] Known: Air inlet temperature T airin =25℃(normal temperature), ammonia inlet temperature Tnh3in = -80℃, assuming the heat exchange efficiency of the heat exchanger is 85%, the outlet temperatures of air and ammonia in the air heat exchanger are:

[0066] Air outlet temperature: T airout =T airin +0.85×(T nh3in -T airin )=-64℃.

[0067] Ammonia outlet temperature: T nh3out =T airint +0.85×(T airin -T nh3in )=9℃.

[0068] Known: the flow rate of ammonia is 100kg / h, the inlet and outlet temperature difference of air ΔT air =T airin -T airout =25-(-64)=89℃, the temperature difference between the inlet and outlet of ammonia ΔT nh3 =T nh3in -T nh3out =-80-9=-89℃.

[0069] Unit heat absorption of ammonia: Under 1 bar pressure, ammonia heats from -80℃ to 9℃, and undergoes three processes: liquid heating stage (-80℃→-33.3℃), vaporization stage (-33.3℃ saturated liquid→saturated gas), and gas heating stage (-33.3℃→9℃). The heat absorption of the three stages is Q nh3 =1682.6kJ / kg.

[0070] According to the basic properties of the substance, the specific heat capacity of air is C pair ≈1.005kJ / (kg·K). Based on the law of conservation of energy, m air ×C pair ×ΔT air =m nh3 ×Q nh3 , we can deduce m air =m nh3 ×Q nh3 ÷

[0071] (C pair ×ΔT air )=1880kg / h.

[0072] At a wind pressure of 800 Pa and an efficiency of 65%, the power of the variable frequency blower 13 required for an air flow of 1880 kg / h is about 0.7 kW, which is much lower than the work of the turbine generator 7 of 15 kW.

[0073] Considering the power generation efficiency and the battery charge and discharge efficiency, the power generation power P of the turbine generator 7 is 发电 =15×0.9=13.5kW. After deducting the power of the variable frequency blower 13 (0.7kW), there is still 12.8kW available to drive the entire vehicle electrical appliances (for example, in a hybrid vehicle, this part of the electricity can also drive the vehicle).

[0074] Innovation:

[0075] 1) The present invention uses a turbine generator 7 to generate electricity, reducing the ammonia pressure from high to low, thereby recovering energy from the ammonia pressure reduction process. In contrast, in conventional on-board ammonia hydrogen production systems, a pressure reducing valve is installed at the ammonia tank outlet, which reduces the outlet pressure from 10 bar to 1 bar through the principle of throttling, resulting in significant energy loss.

[0076] 2) Utilizing the turbine generator 7 to significantly reduce ammonia temperature. The ammonia cooling method of the present invention differs from traditional throttling methods in that: when the working fluid passes through a traditional throttling valve, no work is performed (the amount of work performed is 0), energy conservation manifests itself as constant enthalpy, and the temperature change caused by changes in physical properties due to changes in pressure differentials is extremely limited. In the turbine generator 7, however, high-pressure ammonia drives the blades to rotate, performing external work (mechanical work). According to the first law of thermodynamics (conservation of energy), the internal energy of the system decreases (change in internal energy = amount of work performed), resulting in a significant temperature drop (internal energy and temperature are strongly correlated).

[0077] 3) Based on the basic principle of convective heat transfer, with only minor modifications, the addition of a large-area heat exchanger 8 can improve the efficiency of air energy utilization. In addition, the low-temperature air can be used in the vehicle's air conditioning system, reducing the vehicle's energy consumption.

[0078] 4) The power generated by the turbine generator 7 is much higher than the power consumption of the variable frequency blower 13. The excess power can be stored and used to drive the vehicle's electrical appliances. In hybrid vehicles, it can also be used to drive the entire vehicle.

[0079] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A vehicle-mounted ammonia-to-hydrogen system, comprising a liquid ammonia tank (1) and an ammonia-to-hydrogen heat exchange catalytic reactor (2), characterized in that: The invention also includes an engine (3) and a controller. The liquid ammonia tank (1) is connected to the ammonia inlet of the ammonia-to-hydrogen heat exchange catalytic reactor (2) through an ammonia pipe (4). The engine (3) is connected to the exhaust inlet of the ammonia-to-hydrogen heat exchange catalytic reactor (2) through an exhaust pipe (5). The ammonia pipe (4) is provided with a control valve (6), a first heat exchanger (9), a turbine generator (7), a large-area heat exchanger (8), The second heat exchanger (10) is electrically connected to the on-board battery (11), the large-area heat exchanger (8) is connected to the variable-frequency blower (13) through an air pipe (12), the engine (3) is connected to the first heat exchanger (9) through a cooling water pipe (14), the nitrogen-hydrogen outlet of the ammonia-to-hydrogen heat exchange catalytic reactor (2) is connected to the second heat exchanger (10) through a nitrogen-hydrogen gas pipe (16), and the controller is electrically connected to the control valve (6) and the variable-frequency blower (13).

2. The vehicle-mounted ammonia-to-hydrogen system according to claim 1, characterized in that: The air pipe (12) at the output end of the large-area heat exchanger (8) is connected to a cooling coil (17), and the cooling coil (17) is installed at the air outlet of the automobile air-conditioning system.

3. The vehicle-mounted ammonia-to-hydrogen system according to claim 1, characterized in that: A second temperature sensor (18) and an auxiliary electric heating tube (19) are provided in the ammonia-to-hydrogen heat exchange catalytic reactor (2), and the controller is electrically connected to the second temperature sensor (18) and the auxiliary electric heating tube (19).

4. The vehicle-mounted ammonia-to-hydrogen system according to claim 3, characterized in that: The exhaust pipe (5) is provided with a bypass pipe (20) connected in parallel with the ammonia-to-hydrogen heat exchange catalytic reactor (2), the bypass pipe (20) is provided with a bypass regulating valve (21), and the controller is electrically connected to the bypass regulating valve (21).

5. The vehicle-mounted ammonia-to-hydrogen system according to claim 1, characterized in that: The heat transfer capacity of the large-area heat exchanger (8) through convection heat transfer is calculated as follows: Q = α·A·ΔT (Formula 1) In formula 1, Q is the heat transfer rate of convection heat transfer; α is the convection heat transfer coefficient between air and radiator; A is the heat transfer surface area of ​​radiator; ΔT is the temperature difference, that is, the temperature difference between low-temperature ammonia and normal temperature air.

6. The vehicle-mounted ammonia-to-hydrogen system according to claim 1, characterized in that: The turbine outlet temperature and turbine work of the turbine generator (7) are calculated as follows: The calculation formula for the turbine outlet temperature is: Wherein, T1 is the inlet temperature, T2 is the outlet temperature, P1 is the inlet pressure, P2 is the outlet pressure, γ is the specific heat ratio, γ = 1.3; The calculation formula for turbine work is: W=W 理论 ×k (Formula 4) Among them, W 理论 is the theoretical work of the turbine, h1 is the specific enthalpy of ammonia inlet, h2 is the specific enthalpy of ammonia outlet, is the mass flow rate, W is the work done by the turbine, k is the efficiency, k=60%.

7. The vehicle-mounted ammonia-to-hydrogen system according to claim 1, characterized in that: The air heat exchange outlet temperature of the large-area heat exchanger (8) is calculated as follows: Air outlet temperature: T airout =T airin +j×(T nh3in -T airin ) (Formula 5) Ammonia outlet temperature: T nh3out =T nh3in +j×(T airin -T nh3in ) (Formula 6) Air demand: m air =m nh3 ×Q nh3 ÷(C pair ×ΔT air ) (Formula 7) Among them, T airout is the air outlet temperature, T nh3out is the ammonia outlet temperature, m air is the air demand, m nh3 is the ammonia demand, Q nh3 is the heat absorbed by ammonia through the large-area heat exchanger (8), C pair is the specific heat capacity of air, T airin is the air inlet temperature, T nh3in is the ammonia inlet temperature, ΔT air =T airin -T airout , j is the heat exchange efficiency, j = 0.85.

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