EP3093549A1

EP3093549A1 - Vehicle comprising an internal combustion engine, at least one storage vessel and a cooling chamber and/or an air condition unit

Info

Publication number: EP3093549A1
Application number: EP15167069.2A
Authority: EP
Inventors: Mathias WEICKERT; Lena Arnold; Ulrich Mueller; Stefan Marx
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2015-05-11
Filing date: 2015-05-11
Publication date: 2016-11-16
Also published as: WO2016180807A1

Abstract

The invention is related to a vehicle comprising an internal combustion engine (8), at least one storage vessel (1) and a cooling chamber (10) and/or an air condition unit (12), wherein a sorption medium is disposed in the at least one storage vessel (1) and the at least one storage vessel contains a fuel for the internal combustion engine (8), the combustion engine (8) and the at least one storage vessel (1) are connected by a pipe for conducting the fuel, and the at least one storage vessel is thermally coupled with the cooling chamber (10) and/or the air condition unit (12). The invention is further related to a process for operation of a vehicle.

Description

The present invention relates to a vehicle comprising an internal combustion engine, at least one storage vessel and a cooling chamber and/or an air condition unit, wherein a sorption medium is disposed in the at least one storage vessel and the at least one storage vessel contains a fuel for the internal combustion engine. The invention is further related to a process for operation of the vehicle.
Referring to an energy source storage system for the drive of vehicles apart from conventional fuels, adsorbed natural gas (ANG) has the potential to replace compressed natural gas (CNG) in mobile storage applications such as in vehicles. In ANG-applications a solid, such as activated carbon or metal organic framework material, is packed in a vessel to increase the storage density, enabling lower pressure operation with the same capacity or higher amounts of stored gas at the same pressure.
Such ANG-storage vessels comprise sorption media, which is also referred to as adsorbent medium, adsorbent, adsorber or absorber. The gas is stored by adsorption on the sorption medium, in the cavities between individual particles of the sorption medium and in parts of the vessel, which are not filled with sorption medium. Alternatively or additionally the gas can be absorbed by the sorption medium. The filled storage vessel can be pressurized or non-pressurized. Selection of a suitable vessel depends on the applied maximum pressure. The higher the storage pressure the more gas can be stored per volume.
Due to their large surface areas, in particular metal-organic framework materials (MOFs) are of interest for applications in gas storage. Advantageously, pulverulent materials are processed to compact shaped bodies. These can be handled more conveniently and especially in a safer manner. Shaped bodies allow better exploitation of volumes available in apparatuses or vessels and reduce pressure drops. Prerequisite for a successful use for shaped bodies are preliminarily a high loading capacity, adequate thermal and mechanical stability and high abrasion resistance.
Sorption, which can be adsorption and/or absorption, is an exothermic process. Any sorption or desorption, as well as any compression and decompression, is accompanied by temperature changes in a storage system. The heat of sorption has a detrimental effect on performance during both charge- and discharge cycles of storage vessels, especially when the storage vessel comprises a sorption medium. The way of filling a storage system at a fuel station influences strongly the total fuel amount in the storage vessel that is available from the storage vessel at the end of a filling process. The fuel temperature in the storage vessel increases due to the heat of compression and/or sorption. For CNG-systems without sorbent material the temperature in the storage vessel increases during filling to approximately 50°C above ambient temperature due to the heat of compression. For ANG-systems the temperature in the storage can further increase to an absolute temperature of approximately 90°C due to the additional heat of sorption.
In the aim of a maximal exploitation of the storage space, the temperature profile established in the storage vessel during the filling procedure has to be taken into consideration. An efficient sorption allows a reduced filling time as the same amount of gas can be stored in a shorter time period. Hence, the maximum amount of stored gas can be increased when the available filling time is limited. During filling the storage vessel with gas two sources are relevant for a temperature increase in the vessel. These are the heat due to compression of the gas and the heat liberated as a result of the exothermic sorption. The amount of generated heat directly depends on the amount of sorbed gas. The more gas is sorbed on the sorption medium, the more heat is liberated. And with an increasing sorbed amount of gas on the solid, the sorption rate, defined as amount of gas sorbed per unit of time, is reduced.
The temperature increase constitutes a limitation especially for the ANG technique as for example carbon fiber tanks are presently only approved to operate at temperatures to up to 80°C. A charge cycle normally will be performed in a fuel station, at least for mobile applications, where the released sorption heat can be removed. In turn, desorption is an endothermic process and heat has to be supplied when gas is taken from the storage vessel. Contrary to the charge cycle, the rate of discharge is dictated by the energy demand of the application. Heat management is therefore of great importance when storage vessels with sorption medium are used. Heat management systems have to be optimized with regard to a minimum of required space and a minimum of additional weight in mobile applications, a minimum of additionally required electrical power and limited costs.
WO 2009/071436 A1 discloses a method for storing gaseous hydrocarbons in a sorption reservoir. The temperature of the stored hydrocarbons when the desorption reservoir is full is lower than room temperature and higher than the evaporation temperature of the hydrocarbon. The sorption reservoir contains zeolith, activated carbons or metal-organic framework compounds. For emptying of the sorption reservoir, the temperature in the sorption reservoir is increased with decreasing gas content so that a given minimal pressure is maintained in the sorption reservoir. The reservoir further comprises a heating element.
DE 10 2008 043 927 A1 describes a device for the storage of gas and a process for discharging a gas from a sorption reservoir. Gas is discharged from the sorption reservoir at a constant discharge temperature and after reaching a given working pressure, gas withdrawn from the sorption store at a pressure being lower than the working pressure is compressed.
Further, for gas storage systems a complete emptying of the storage vessel is not possible and a residual amount of gas always remains in the storage vessel when a minimum gas pressure level is required for example for the operation of a combustion engine of a vehicle. This residual amount of gas is higher for storage systems comprising sorption media than for storage systems without sorption media. Further, the residual amount of gas strongly depends on temperature.
Adsorption refrigeration/heating modules can be part of a refrigeration/heating machine or themselves be such a machine. They are based on the principle that heat energy is liberated or withdrawn as a result of sorption and desorption processes, so that they can be used for cooling and/or heating. An adsorption heat-exchange module which has a moisture-absorbing layer composed of an organic polymer is described, for example, in EP-A 1 840 486 . Sorption refrigeration/heating modules mean that the heating or cooling is brought about by the sorption or desorption process of a working medium onto or from desorption medium.
The use of zeolites in heating and cooling storage systems is described in EP-A 1 652 817 . Specific zeolites in a sorption apparatus for heating and cooling gas streams are described in DE-A 100 28 030 . Such an adsorption refrigeration/heating module is described as adsorption machine in DE-A 10 2006 011 410 .
DE-A 10 2006 059 504 describes a heat pump having elements which can be stacked. EP-A 0 412 161 describes a cryogenic adsorption refrigeration machine and also a method of cooling an object by means of this refrigeration machine. EP-A 0 840 077 likewise describes an adsorption refrigeration machine.
An adsorption heat pump is described in EP-B 1 279 908 . Containers in the form of a flask or packaging having a self-cooling module are described in EP-A 1 647 786 and US-B 7,213,401 .
Refrigerating vehicles of the state of the art typically comprise a compressor for the generation of coldness in a cooling chamber, where goods to be transported can be stored. These compressors are in general electrically driven. In case of electrically driven compressors, the electricity has to be provided by the generator of the vehicle. Refrigerating vehicles have an enhanced fuel consumption. Fuel consumption is also increased when a vehicles provides an air condition unit for cooling the passenger compartment.
It is an object of the present invention to provide a vehicle comprising a cooling chamber and/or an air condition unit with a reduced fuel consumption. Further, the residual amount of fuel present in the storage vessel when the minimum storage pressure is reached is to be reduced.
This object is achieved by a vehicle comprising an internal combustion engine, at least one storage vessel and a cooling chamber and/or an air condition unit, wherein a sorption medium is disposed in the at least one storage vessel and the at least one storage vessel contains a fuel for the internal combustion engine, the combustion engine and the at least one storage vessel are connected by a pipe for conducting the fuel, and the at least one storage vessel is thermally coupled with the cooling chamber and/or air condition unit.
The object is further achieved by a process for operation of the vehicle comprising

a. a filling step, wherein
1. i. the at least one storage vessel is filled with the fuel,
2. ii. the fuel is contacted with the sorption medium,
3. iii. the fuel is filled into the at least one storage vessel until a loading with fuel of 250 g/L, referring to the total inner volume of the at least one storage vessel, is reached and
4. iv. during filling, the at least one storage vessel is cooled and a maximum temperature T_max, referring to a spatial maximum, in the at least one storage vessel does not exceed 85°C
  and/or, after filling is completed, the maximum temperature T_max is decreased to less than 35°C and
b. a driving step, wherein
1. i. part of the fuel, filled in the at least one storage vessel, is conducted from the at least one storage vessel to the internal combustion engine and combusted in the internal combustion engine,
2. ii. the cooling chamber and/or the air condition unit is cooled by transferring heat from the cooling chamber and/or the air condition unit to the at least one storage vessel.

The cooling chamber is a refrigerator storage space of the vehicle, wherein temperature-sensitive goods like milk products, fruit etc. can be transported. The term "vehicle" includes but shall not be limited to cars, trucks, ships, airplanes and the like. Cars and trucks are preferred. The typical volume of the cooling chamber in for example trucks is in a range from to 5 to 50 m³.
Alternatively or additionally, a space of the vehicle to be cooled can be the passenger compartment of the vehicle, which is typically effectuated by means of the air condition unit.
When the internal combustion engine of the vehicle is running in order to drive the vehicle, fuel is taken from the at least one storage vessel by desorption which leads to a temperature decrease in the at least one storage vessel. By means of the invention, this temperature decrease is transferred to the cooling chamber and/or the air condition unit.
The thermal coupling between the at least one storage vessel and the cooling chamber and/or the air condition unit can be effectuated by a pipe, which is flowed through by a heat transfer fluid.
Preferably, the at least one storage vessel is thermally coupled with the cooling chamber and/or the air condition unit by a heat exchanger comprising a first heat transfer medium and a second heat transfer medium.
In case, a heat exchanger is provided between the at least one storage vessel and the cooling chamber and/or the air condition unit, preferably the first heat transfer medium circulates between the at least one storage vessel and the heat exchanger. This first heat transfer medium preferably comprises, more preferably consist of, part of the fuel stored in the at least one storage vessel, which is taken out of the at least one storage vessel, conducted to the heat exchanger and conducted back to the at least one storage vessel in recirculation. The second heat transfer medium preferably circulates between the heat exchanger and the cooling chamber and/or the air condition unit. Preferably, the second heat transfer medium is selected from the group consisting of propane, propene, water, glycol and brine.
In a preferred embodiment, the vehicle comprises a compressor for recirculation of the first heat transfer medium, comprising part of the fuel, wherein a discharge side of the compressor is connected with the at least one storage vessel. The discharge side of the compressor can also be described as pressure side, as the fuel is repressurized by the compressor before being recycled into the at least one storage vessel from the heat exchanger or from the location, where the heat transfer between the fuel and the cooling chamber and/or the air condition unit is taking place. The heat transfer from and to the fuel, respectively is typically effectuated at a pressure in a range from 1 bar to 80 bar.
Preferably, the compressor is a screw compressor, which is applicable for initial pressures in the range from 2 to 80 bar.
Typically, the compressor ensures a pressure level of the fuel of at least 150 bar, more preferably at least 200 bar and most preferably at least 220 bar, after the at least one storage vessel was filled up at a filling station. Subsequently, the pressure, corresponding to the current fill level, is ensured.
As defined according to the inventive process, already the method of filling the at least one storage vessel with the fuel is relevant for an effective exploitation of the temperature decrease in the at least one storage vessel due to desorption.
The maximum sorption capacity depends on the type of fuel and the type of sorption medium but often, at least for preferred fuels and sorption media, the loading with fuel of 250 g/L corresponds to at least 80 % of the maximum sorption capacity at a storage pressure of 250 bar, taking into account that the sorption capacity of the at least one sorption medium cannot further be increased at pressure levels of preferably more than 80 bar, often more than 100 bar. Once this pressure level is reached, additional fuel can only be stored within the at least one storage vessel by compression and further storage pressure increase therein, wherein no further fuel can be stored on the surface of the sorption medium.
Consequently, when the loading of 250 g/L, often corresponding to a storage pressure between 80 bar and 100 bar, is reached, no further relevant amount of heat is liberated due to sorption, preferably adsorption.
According to the present invention, the filling can be accompanied by a cooling of the at least one storage vessel, wherein a maximum temperature of 85°C, is not exceeded. When the at least one storage vessel is not cooled during filling, damages, especially concerning materials of the storage vessel wall, can occur. Alternatively or additionally, heat is removed from the at least one storage vessel after completion of the filling step to such an extent that the maximum temperature in the at least one storage vessel is below 35°C. This can be achieved by cooling during filling and/or cooling after filling or also by merely waiting for temperature equalization between the at least one storage vessel and the environment after filling.
Maximum temperatures T_max, referring to a spatial maximum, means that in all volume elements in the at least one storage vessel, the temperature is not higher than the maximum temperature T_max.
When the vehicle is driven, part of the fuel, which was filled in the at least one storage vessel is led to the internal combustion engine to produce drive energy. In contrast to the sorption process during filling, the desorption during discharge of the fuel from the at least one storage vessel leads to a temperature decrease in the at least one storage vessel, which is used to cool the cooling chamber and/or the air-condition unit as soon as the maximum temperature T_max in the at least one storage vessel of less than 35°C is reached.
Preferably, in the filling step (a) during filling the maximum temperature T_max in the at least one storage vessel does not exceed 80°C. Further, it is preferred that in the filling step (a) a flow-through is established in the at least one storage vessel, wherein a flow of the fuel out of the at least one storage vessel exceeds 0 kg/h, more preferably 50 kg/h, and most preferably 100 kg/h. The flow-through regime is further described in WO 2014/057416 and comparable to the recirculation of the first heat transfer medium between the heat exchanger and the at least one storage vessel for transferring heat into the at least one storage vessel during driving. Here, during filling, this recirculation is used to cool the fuel that is conducted out of the at least one storage vessel and circulated back to the at least one storage vessel. This cooling can also be effectuated in the heat exchanger.
Preferably, in the filling step (a) at least 90 % of the maximum sorption capacity of the sorption medium, referring to the fuel, is reached at an adsorption pressure in the at least one storage vessel in a range from 80 bar to 100 bar. This preferred relation between maximum sorption capacity and storage pressure is for example the case for the MOF materials MOF A520, MOF Z377 and MOF C300. The sorption capacity of the adsorbent media, defined by the ratio of the mass of the adsorbed fuel to the mass of the adsorption medium, strongly depends on temperature pressure and is reduced with increasing temperature and decreasing pressure. The maximum sorption capacity is the sorption capacity, which cannot be exceeded even with further increase in pressure for a given temperature.
Further preferably, in the filling step (a) the fuel is filled into the at least one storage vessel until an absolute pressure of at least 200 bar in the at least one storage vessel is reached.
In a preferred embodiment at least one pressure sensor and at least one temperature sensor are disposed in the interior of the at least one storage vessel. Sensors commonly used in the art and known for example from the CNG technique can be used for this purpose. The position of the at least one pressure sensor can be freely selected at and/or in the at least one storage vessel as the pressure is equally distributed in the system. In a preferred embodiment, the at least one temperature sensor is disposed in the at least one storage vessel in a position characterized by a temperature from which the average temperature of the interior of the at least one storage vessel is deducable. It is further preferred to provide a temperature sensor in a location in the at least one storage vessel, where maximum temperatures are expected. This is typically the case in a highest position at the storage vessel wall.
The vehicle can comprise more than one storage vessel. When the vehicles comprises more than one storage vessel, it is preferred that at least one of the storage vessels in the filling step (a) is filled with the fuel only until not more than 98 %, more preferably, not more than 95 % and most preferably not more than 90%, of the maximum sorption capacity of the sorption medium is occupied by the fuel. This means that in the case, where the vehicle comprises several storage vessels with sorption medium, part of the storage vessels can be filled to a saturation level corresponding to approximately the maximum sorption capacity of the sorption medium, which is typically about 100 bar. This is advantageous, as already from the first portion of fuel taken from this storage vessel leads to a relevant temperature decrease in the storage vessel, as at a lower pressure level the desorption process begins directly and desorption is not preceded by only decompression of the fuel surrounding the sorption medium. Remaining storage vessels can be filled up to 250 bar, these can be used later for cooling or fuel can be transferred from these storage vessels to the storage vessels with lower filling level.
In the case, where the vehicle comprises more than one storage vessel, preferably, fuel is taken initially from only one of the storage vessels and then the remaining storage vessel can be emptied in parallel or in series. A serial discharge is preferred, when a high cooling power is required. A discharge in parallel is preferred, when the requirement in cooling power is less. Starting the discharge from only one of the storage vessels has the advantage that a higher cooling power can be provided compared to a discharge, wherein more than one storage vessel is opened at the same time as the pressure decrease in the first storage vessel is faster and the desorption process becomes predominant earlier.
When more than one storage vessel is present in the vehicle, all storage vessels comprise the sorption medium and all storage vessels are filled up to 250 bar, it is also possible to cool only one of the storage vessels during filling with the fuel. Here it is preferred to start the heat transfer from the cooling chamber and/or the air condition unit with the cooled storage vessel, whereas the remaining storage vessels can be used for cooling afterwards, when the enhanced filling temperature is already equilibrated against the environmental temperature.
It is further possible to combine at least one storage vessels comprising the sorption medium with at least one storage vessels without sorption medium. A vehicle can for example comprise one storage vessel with a sorption medium and one storage vessel without sorption medium, both filled at the gas station to typically 250 bar. In this case, it is preferred that fuel is first taken from the storage vessel without sorption medium, especially when no cooling, over the air condition unit for example, is currently required. When later, cooling is required, fuel can be transferred from the storage vessel with sorption medium to the storage vessel without sorption medium, which is already partly emptied, thus desorption occurs, even when no fuel is consumed at that instance, and the cooling power can be used.
Preferably, the vehicle comprises the compressor and in the driving step (b) the fuel is recirculated from the at least one storage vessel to the compressor and back to the at least one storage vessel.
Preferably, the vehicle comprises a second compressor and in the driving step (b) the second compressor is used to compress the fuel before being conducted to the combustion engine when the absolute pressure in the storage vessel is less than 10 bar, which is the typical storage pressure level which has to be provided for a combustion engine.
Alternatively to the application of two different compressors, only one compressor can be used for both, recirculation of the fuel and supply of the fuel at a sufficient pressure level to the internal combustion engine.
Nevertheless, it is advantageous to apply two different compressors for recirculation of the fuel and conveying the fuel to the combustion engine, as the discharge pressure level of the two options is differing. For the combustion engine a pressure level of 10 bar has to be ensured, whereas for fuel recirculation a pressure of up to 250 bar is required.
In a further preferred embodiment, the fuel comprises a gas selected from the group consisting of natural gas, shale gas, town gas, methane, ethane, hydrogen, propane, propene, ethylene, carbon dioxide and combinations thereof. In a particularly preferred embodiment, the fuel comprises methane and/or hydrogen to an extent of more than 70 % by volume. Generally, the storage vessel can comprise any fuel that is suitable for combustion in the internal combustion engine, and which is adsorbed or absorbed by the sorption medium. The fuel is generally present in the storage vessel in a gaseous form and in a sorbed state. Due to compression, also small amounts of liquid can occur. For the purpose of the present invention, the term "gas" is used in the interest of simplicity, but gas mixtures are likewise encompassed.
In a further preferred embodiment, the storage vessel is a pressure vessel for the storage of fuel at a pressure in the range of up to 500 bar, preferably in a range of 1 bar to 400 bar, most preferably in the range of 1 bar to 250 bar. In other embodiments, also the range of 1 bar to 100 bar can be preferred. Depending on the installation space available and the maximum permissible pressure in the storage vessel, different cross-sectional areas are suitable for the storage vessel, for example circular, elliptical or rectangular. Irregularly shaped cross-sectional areas are also possible, e. g. when the storage vessel is to be fitted into a hollow space of a vehicle body. It is also possible to divide the total storage volume into more than one storage vessel. For higher pressure above about 100 bar, circular and elliptical cross-sections are particularly suitable. The vessel size varies according to the application. Diameters of the vessel of approximately 50 cm are typical for tanks in trucks and approximately 20 cm for tanks in cars, respectively. In cars, typically, total inner volumes of the storage vessel between 20 liters and 40 liters are provided, whereas storage vessels of a volume between 500 liters and 3000 liters can be found in trucks.
The at least one storage vessel, especially the wall of the at least one storage vessel, can be made from any material as for example metal, steel, fabric, fiber, plastic or composite material. Fiber composite material and steel are preferred. The wall of the storage vessel can be configured as a double wall comprising a third heat transfer medium for heat transfer.
In a further preferred embodiment, the wall of the storage vessel comprises at least one outlet and at least one inlet. More preferably, the at least one inlet and the at least one outlet are provided at the same half of the storage vessel. The half can also be named as side or end. The at least one inlet and the at least one outlet can be located in the same position and/or combined in one constructional part or adapter. The close arrangement of the at least one inlet and the at least one outlet is especially advantageous in order to establish the flow-through regime during filling or for recirculation of the fuel between the at least one storage vessel and the heat exchange.
Typically, a diameter of the at least one inlet is smaller than the diameter of the at least one vessel by a factor of 5 to 10. Preferably the diameter of the at least one inlet is smaller than 50 cm, often the diameter of the mouth of the storage vessel has a standardized size as usually applied in tanks for vehicles.
The sorption medium can generally be disposed in the at least one storage vessel in form of powder, pellets, shaped bodies or at least one monolith or combinations thereof.
As pellets extrudates are preferred. When the sorption medium is present as a bed of pellets, the ratio of the permeability of the pellets to the smallest pellet diameter is between 1·10^-11 m²/m and 1·10^-16 m²/m, preferably between 1·10^-12 m²/m and 1·10¹⁴ m²/m, and most preferably 1·10^-13 m²/m.
Preferably, the sorption medium is present in form of at least one monolith and the at least one monolith has an extension in one direction in space in a range from 10 cm to 100 cm. Typically, this extension in one direction in space is the radial diameter, referring to the at least one storage vessel, having preferably a cylindrical shape, with a longer axial extension than radial extension. A monolith is understood to be a shaped body with a greater size compared to known sizes of typical shaped bodies like pellets.
In case where the at least one storage vessel comprises only one monolith, the monolith has a longest first extension in radial direction, and a longest second extension in longitudinal axial direction, wherein the longest first extension is smaller than the longest second extension. Axial and radial referring to the at least one storage vessel. In a preferred embodiment, the longest first extension of the monolith is in a range from 10 cm to 100 cm and the longest second extension of the monolith is in a range from 20 cm to 300 cm. In a further preferred embodiment, applicable for example for cars, the longest second extension of the monolith is in the range from 20 cm to 120 cm, more preferably from 70 cm to 90 cm, and the longest first extension of the monolith is in a range from 10 cm to 60 cm, more preferably from 30 cm to 50 cm. In another further preferred embodiment, applicable for example for trucks, the longest second extension of the monolith is in the range from 100 cm to 300 cm, more preferably from 150 cm to 200 cm and the longest first extension of the monolith is in a range from 30 cm to 100 cm, more preferably from 40 cm to 60 cm.
Preferably, in a radial cross-sectional view, the form of a circumference of the storage vessel corresponds to the form of a circumference of the monolith. In a further preferred embodiment, the at least one storage vessel has a cylindrical shape and also the monolith has the form of a cylinder.
In an alternative embodiment, at least two monoliths made of the sorption medium are provided in the at least one storage vessel. For this embodiment, a ratio between a longest first extension of each of the at least two monoliths in radial direction, and a longest second extension of each of the at least two monoliths in axial directions, is equal to or greater than 5, axial and radial referring to the at least one storage vessel.
In a preferred embodiment, the longest first extension in radial direction of each of the at least two monoliths is in a range from 10 cm to 100 cm. In a further preferred embodiment, applicable for example for cars, the longest first extension of each of the at least two monoliths is in a range from 10 cm to 60 cm, more preferably from 30 cm to 50 cm. In another further preferred embodiment, applicable for example for trucks, the longest first extension of each of the at least two monoliths is in a range from 30 cm to 100 cm, more preferably from 40 cm to 60 cm. In a further preferred embodiment, the longest second extension of each of the at least two monoliths in axial direction, which can also be described as the thickness of each of the at least two monoliths, is less than 10 cm, preferably less than 2 cm and more preferably in a range from 0.5 cm to 1.5 cm, most preferably in a range from 0.8 cm to 1.2 cm. If the second extension is too large and the thickness of each the at least two monoliths is too large, respectively, no effective heat transfer can be established within each of the at least two monoliths. Further an inner surface of the porous solid might be destroyed by producing monoliths with a higher thickness. Preferably, the at least one storage vessel has a cylindrical shape, each of the at least two monoliths has a disk-like shape and the at least two monoliths are arranged one next to the other in longitudinal axial direction of the at least one storage vessel. Preferably, in a radial cross-sectional view, the form of the circumference of the at least one storage vessel corresponds to the form of the circumference of each of the at least two monoliths.
Independent of the number of monoliths present in the at least one storage vessel and assuming a longitudinal central axis of the at least one storage vessel, the at least one monolith comprises an opening in axial direction, axial referring to the central axis of the at least one storage vessel. Preferably, the at least one monolith is completely traversed by the opening. Further, the at least one monolith comprises preferably in addition to the opening hollow channels in axial direction and a cross-sectional area of each hollow channel is smaller than a cross-sectional area of the opening.
Preferably, the longest diameter of the opening is in the range from 0.3 % to 20 % of the longest diameter of the radial cross-sectional area of the at least one storage vessel. It is further preferred when the opening in the at least one monolith is arranged centrally with respect to the at least one storage vessel.
The at least one monolith can comprise at least one spacer providing an open space or void space, which is free of the sorption medium, between the at least one monolith and/or the storage vessel wall or between two of the at least two monoliths.
The sorption medium is preferably selected from the group consisting of activated charcoal, zeolites, activated aluminia, silica gels, open-pore polymer foams, metal hydrides, metal-organic frameworks (MOF) and combinations thereof.
Zeolites are crystalline aluminosilicates having a microporous framework structure made up of AlO₄ and SiO₄ tetrahedra. Here, the aluminum and silicon atoms are joined to one another via oxygen atoms. Possible zeolites are zeolite A, zeolite Y, zeolite L, zeolite X, mordenite, ZSM (Zeolites Socony Mobil) 5 or ZSM 11. Suitable activated carbons are in, particular, those having a specific surface area above 500m² g^-1, preferably about 1500m² g^-1, very particularly preferably above 3000m² g^-1. Such an activated carbon can be obtained, for example under the name Energy to Carbon or MaxSorb.
Metal-organic frameworks (MOF) are known in the prior art and are described for example in US 5,648,508 , EP-A 0 700 253 , M. O'Keeffe et al., J. Sol. State Chem., 152 (2000), , H. Li et al., Nature 402, 1 (1999), page 276, M. Eddaoudi et al., Topics in Catalysis 9, (1999), pages 105 to 111, B. Chen et al., Science 291, (2001), pages 1021 to 1023, DE-A 101 11 230 , DE-A 10 2005 053430 , WO-A 2007/054581 , WO-A 2005/049892 and WO-A 2007/023134 . The metal-organic frameworks (MOF) mentioned in EP-A 2 230 288 A2 are particularly suitable for storage vessels. Preferred metal-organic frameworks (MOF) are MIL-53, Zn-tBu-isophthalic acid, AI-BDC, MOF 5, MOF-177, MOF-505, MOF-A520, HKSUST-1, IRMOF-8, IRMOF-11, Cu-BTC, Al-NDC, Al-AminoBDC, Cu-BDC-TEDA, Zn-BDC-TEDA, Al-BTC, Cu-BTC, Al-NDC, Mg-NDC, Al-fumarate, Zn-2-methylimidazolate, Zn-2-aminoimidazolate, Cu-biphenyldicarboxylate-TEDA, MOF-74, Cu-BPP, Sc-terephthalate. Greater preference is given to MOF-177, MOF-A520, KHUST-1, Sc-terephthalate, Al-BDC and Al-BTC.
Apart from the conventional method of preparing the MOFs, as described, for example, in US 5,648,508 , these can also be prepared by an electrochemical route. In this regard, reference may be made to DE-A 103 55 087 and WO-A 2005/049892 . The metal organic frameworks prepared in this way have particularly good properties in respect of the sorption and desorption of chemical substances, in particular gases.
Particularly suitable materials for the adsorption in storage vessels are the metal-organic framework materials MOF A520, MOF Z377 and MOF C300.
MOF A 520 is based on aluminum fumarate. The specific surface area of a MOF A520, measured by porosimetry or nitrogen adsorption, is typically in the range of from 800 m²/g to 2000 m²/g. The adsorption enthalpy of MOF A520 with regard to natural gas amounts to 17 kJ/mol. Further information on this type of MOF may be found in "Metal-Organic Frameworks, Wiley-VCH Verlag, David Farrusseng, 2011 ". MOF Z377, in literature also referred to as MOF 177, is based on zinc-benzene-tribenzoate. The specific surface area of a MOF Z377, measured by porosimetry or nitrogen adsorption, is typically in the range from 2000 m²/g to 5000 m²/g. The MOF Z377 typically possesses an adsorption enthalpy between 12 kJ/mol and 17 kJ/mol with respect to natural gas. MOF C300 is based on copper benzene-1,3,5-tricarboxylate and for example commercially available from Sigma Aldrich under the trade name Basolite® C300.
WO-A-03/102000 describes in general terms the conversion of metal-organic framework powder into shaped bodies like pellets with a resistance to pressure in the range from 2 to 100 N. In an example pellets which have a resistance to pressure of 10 N are made by means of eccentric press.
To form shaped bodies or monoliths several routes exist, among them molding the pulverulent material alone or in combination with a binder and/or other components into a shaped body or monolith, for example by pelletizing. In the context of the present invention, the term "molding" refers to any process known to the expert in the field by which a porous material, i.e. any powder, powdery substance, array of crystallites etc., can be formed into a shaped body or monolith that is stable under the conditions of its intended use.
While the step of molding into a shaped body or monolith is mandatory, the following steps are optional. The molding may be preceded by a step of mixing. The molding may be preceded by a step of preparing a paste-like mass or a fluid containing the porous material, for example by adding solvents, binders or other additional substances. The molding may be followed by a step of finishing, in particular a step of drying.
The step of molding, shaping or forming may be achieved by any method known to a person skilled in the art to achieve agglomeration of a powder, a suspension or a paste-like mass. Such methods are described, for example, in Ullmann's Enzyklopädie der Technischen Chemie, 4th Edition, Vol. 2, p. 313 et seq., 1972, whose respective content is incorporated into the present application by reference.
In general, the following main pathways can be discerned: briquetting or tableting, i.e. mechanical pressing of the powdery material, with or without binders and/or other additives, granulating (pelletizing), i.e. compacting of moistened powdery materials by subjecting it to rotating movements, and sintering, i.e. subjecting the material to be compacted to a thermal treatment. The latter is limited for the material according to the invention due to the limited temperature stability of the organic materials.
Specifically, the molding step is preferably performed by using at least one method selected from the following group: briquetting by piston presses, briquetting by roller pressing, binderless briquetting, briquetting with binders, pelletizing, compounding, melting, extruding, co-extruding, spinning, deposition, foaming, spray drying, coating, granulating, in particular spray granulating or granulating according to any process known within the processing of plastics or any combination of at least two of the aforementioned methods. Briquetting and/or pelletizing are in particular preferred.
A mixture comprising the porous material can be prepared in a mixer such as intensive mixers, rotary plates, marumerizers, and any other equipment known by a person skilled in the art. Preferred mixers are selected from the group consisting of intensive mixers, rotary plates, ball formers and marumerizers.
The molding can be carried out at elevated temperatures, for example in the range from room temperature to 300°C, and/or at superatmospheric pressure, for example in the range from atmospheric pressure to a few hundred bar, and/or in a protective gas atmosphere, for example in the presence of at least one noble gas, nitrogen, dry air with a relative humidity of preferably less than 45 % or a mixture of two or more thereof. The shaped bodies or monoliths can be formed for example in an excenter press. A compacting force is preferably between 1 kN and 3000 kN, more preferably between 1 kN and 300 kN and most preferably between 10 kN and 150 kN. For higher forces the permeability of the shaped bodies or monoliths is unnecessarily reduced and for smaller forces no stable shaped bodies or monoliths are obtained. The smaller the shaped body or monolith, the higher the applied force can be chosen.
Preferably, the shaped body or monolith is produced with a pressing pressure in a range from 100 bar to 1000 bar, more preferably from 400 bar to 600 bar. The applied press can comprise an upper punch for compaction or it can compact from both sides with an upper punch and a lower punch. Further, the pressing can be performed under vacuum in order to avoid damaging the porous solid.
The step of molding can be performed in the presence of binders, lubricants and/or other additional substances that stabilize the materials to be agglomerated. As to at least one optional binder, any material known to an expert to promote adhesion between the particles to be molded together can be employed. A binder, an organic viscosity-enhancing compound and/or a liquid for converting the material into a paste can be added to the pulverulent material, with the mixture being subsequently compacted.
Suitably binders, lubricants or additives are, for example, aluminum oxide or binders comprising aluminum oxide, as described, for example, in WO 94/29408 , silicon dioxide, as described, for example, in EP 0 592 050 A1 , mixtures of silicon dioxide and aluminum oxide, as described, for example, in WO 94/13584 , clay minerals as described, for example, in JP 03-037156 A , for example montmorillonite, kaolin, bentonite, hallosite, dickite, nacrite and anauxite, alkoxysilanes as described, for example, in EP 0 102 544 B1 , for example tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, or, for example, trialkoxysilanes such as trimethoxysilane, triethoxysilane, tripropoxysilane, tributoxysilane, alkoxytitanates, for example tetraalkoxytitanates such as tetramethoxytitanate, tetraethoxytitanate, tetrapropoxytitanate, tributoxytitanate, or, for example, trialkoxytitanates, such as trimethoxytitanate, triethoxytitanate, tripropoxytitanate, tributoxytitanate, alkoxyzirconates, for example tetraalkoxyzirconates such as tetramethoxyzirconate, tetraethoxyzirconate, tetrapropoxyzirconate, tetrabutoxyzirconate, or, for example, trialkoxyzirconates such as trimethoxyzirconate, triethoxyzirconate, tripropoxyzirconate, tributoxyzirconate, silica sols, amphiphilic substances, copper, graphite, ascorbyl palmitate, expanded natural graphite (ENG), silicon carbide, polysaccharides, fatty acids, alcyl silicon resins , metal-organic framework materials, where the metal-organic framework has a layer composition, or mixtures thereof.
Suitable binders are for example commercially available under trade names like Pural® SB (aluminum oxide), Ludox® AS 40 (colloidal silica), or Silres® MSE100 (methyl and methoxy groups containing polysiloxane).
Preferred binder, lubricants or additives are graphite, stearic acid, magnesium stearate, copper platelets, silicon carbide, expanded natural graphite (ENG), ascorbyl palmitate, polysaccharides, for example commercially available as Zusoplast PS1, aluminium oxide, for example commercially available as Pural SB or mixtures thereof.
In a preferred embodiment, the shaped body or monolith comprises at least 1 % by weight of a binder and/or lubricant, which are selected from the group consisting of inorganic oxide, clay, concrete and graphite. Preferably the shaped body or monolith comprises less than 10 % by weight of a binder and/or lubricant and most preferably, the shaped body or monolith comprises between 1.5 % and 5 % by weight of a binder and/or lubricant and most preferably between 2.5 % and 3.5 %. Alternatively, no binder or lubricant is used.
Further additives which can be used are, inter alia, amines or amine derivatives such as tetraalkylammonium compounds or amino alcohols and carbonate-comprising compounds, e.g. calcium carbonate. Such further additives are described, for instance, in EP 0 389 041 A1 , EP 0 200 260 A1 or WO 95/19222 . Further, pore-forming agents such as organic polymers, preferably methylcellulose, polyethylene oxide or mixtures thereof can be added. Preferably, the shaped body or monolith comprises from 1 % to 50 % by weight of further additives and more preferably from 3 % to 20 % by weight. Alternatively, no further additives are used.

Brief description of the drawings

The present invention is described in more detail at hand of the accompanying drawings, in which:

Figure 1: shows a vehicle according to the invention;
Figure 2: shows a storage vessel of the vehicle according to the invention and
Figure 3: shows a block diagram concerning a vehicle according to the invention.

Figure 1 shows a vehicle 2 according to the invention comprising a storage vessel 1, an internal combustion engine 8, a cooling chamber 10, an air condition unit 12, a heat exchanger 16 and a compressor 18. The storage vessel 1 comprises a sorption medium and fuel for the internal combustion engine 8 is stored by adsorption in the storage vessel 1. The storage vessel 1 is connected with the internal combustion engine 8 by a pipe 14, through which the fuel is conducted. During driving the fuel is conducted from the storage vessel 1 to the internal combustion engine 8 to be combusted in order to drive the vehicle 2. Part of the fuel is led through the heat exchanger 16 as a first heat transfer medium. Before being recirculated into the storage vessel 1 the fuel is recompressed in the compressor 18 to the pressure level, which is the actual pressure level within the storage vessel 1. The temperature of the fuel increases by passing the heat exchanger 16. The temperature of the fuel at its entrance to the heat exchanger 16 is low as the fuel taken from the storage vessel 1 desorbs from the sorption medium, which is an endothermic process.
In the heat exchanger 16, heat is transferred from the cooling chamber 10 and from the air condition unit 12 to the fuel and thus to the storage vessel 1. The cooling chamber 10 and the air condition unit 12 are thereby cooled. The temperature decrease due to desorption in the storage vessel 1 is used at least partly instead of further fuel consuming cooling equipment usually required for the cooling chamber 10 and the air condition unit 12.
Figure 2 shows details of the storage vessel 1 with a total inner volume 22, which is mounted in an elongated horizontal position to the vehicle 2 according to the invention. Two monoliths 3 present in the storage vessel 1, a first monolith 4 and a second monolith 6, are shown in figure 2. The monoliths 3 have a disk-like shape and they are arranged in a parallel to each other. Typically, more than the represented two monoliths 3 are disposed in the storage vessel 1. Preferably, the storage vessel 1 is filled with monoliths 3 over the complete length of its complete central axis 9.
A wall 5 of the storage vessel 1 provides an inlet 7 and an outlet 24 at one end of the storage vessel 1. The fuel can enter the storage vessel 1 through the inlet 7 and further flow in parallel to the central axis 9 through openings 21 of the different monoliths 3. On one lateral surface 23 of each monolith 3 four first spacers 25 are provided in an equal distance to each other. Due to the first spacers 25 a distance 37 is provided between the monoliths 3. As the monoliths 3 possess a disk-like shape, a longest first extension 11 in a radial direction, referring to the storage vessel 1, is clearly larger than a longest second extension 15 in an axial direction 17, referring to the storage vessel 1. The axial direction 17 is parallel to the center axis 9 and a radial direction 13 is any rectangular direction referring to the central axis 9. The radial direction 13 is here further parallel to the lateral surfaces 23.
Apart from lateral surfaces 23 each monolith 3 possesses a peripheral surface 35 which, in this embodiment, is rectangular to the lateral surfaces 23 and facing to the wall 5 of the storage vessel 1 for each monolith 3. The longest first extension 11, which corresponds for the disk-like monoliths 3 to a diameter of the monoliths 3, is smaller than a diameter of the represented cylindrical storage vessel 1. The position of the monoliths 3 in relation to the wall 5 is fixed by means of four second spacers 33 provided at each monolith 3.
Figure 3 shows a block diagram concerning a vehicle 2 according to the invention. A storage vessel 1, comprising monoliths made of a sorption medium, is connected with an internal combustion engine 8 by a pipe 14. The pipe 14 comprises a first valve 45 and an additional compressor 19. The additional compressor 19 is used, when the storage pressure in the storage vessel 1 is lower than the pressure level required by the internal combustion engine 8. In this case, fuel taken from the storage vessel 1 is compressed by the additional compressor 19 until the required pressure level, which is typically 10 bar, is reached. By the valve 45, the amount of fuel reaching the internal combustion engine 8 can be controlled.
The fuel taken from the storage vessel 1 is not completely conducted to the internal combustion engine 8. Part of the fuel withdrawn from the storage vessel 1 is led to a heat exchanger 16 and from the heat exchanger 16 over a compressor 18 back into the storage vessel 1. The compressor 18 is applied in order to maintain the current storage pressure in the storage vessel 1 even when the fuel is recirculated over the heat exchanger 16. The fuel being withdrawn from the storage vessel 1 has a comparatively low temperature due to the desorption process occurring within the storage vessel 1. Heat, which is removed is from a cooling chamber 10 and an air condition unit 12, is transferred to the fuel which by passing part of the fuel through the heat exchanger 16. In this block diagram a second valve 47 is represented, which can be used optionally for filling the storage vessel 1 with the fuel at a gas station.

Comparative example

A truck with a total weight of 12 tons has a cooling chamber with a volume of 1224 liters. In order to maintain a temperature of - 20°C in the cooling chamber, when the surrounding ambient temperature is 20°C, a cooling power of 8.9 kw is required.

Example

The truck described in the comparative example now comprises a storage vessel filled with a monolith providing 600 g/L of the MOF material C300 as sorption medium. The storage vessel has an inner volume of 1224 liters and is filled with fuel, which is natural gas, to a storage pressure of 80 bar, corresponding to the maximum sorption capacity of the sorption medium. By desorption of the fuel from the sorption medium in order to be combusted in an internal combustion engine of the truck, sufficient cooling power is generated for maintaining the required temperature in the above described cooling chamber over three hours.

Reference numerals

1: Storage vessel
2: Vehicle
3: Monolith
4: First monolith
5: Wall
6: Second monolith
7: Inlet
8: Combustion engine
9: Central axis
10: Cooling Chamber
11: Longest first extension
12: Air condition unit
13: Radial direction
14: Pipe
15: Longest second extension
16: Heat exchanger
17: Axial direction
18: Compressor
19: Additional compressor
21: Opening
22: Total inner volume
23: Lateral surface
24: Outlet
25: First spacer
33: Second spacer
35: Peripheral surface
37: Distance
45: First valve
47: Second valve

Claims

A vehicle (2) comprising an internal combustion engine (8), at least one storage vessel (1) and a cooling chamber (10) and/or an air condition unit (12), wherein a sorption medium is disposed in the at least one storage vessel (1) and the at least one storage vessel (1) contains a fuel for the internal combustion engine (8), the combustion engine (8) and the at least one storage vessel (1) are connected by a pipe (14) for conducting the fuel, and the at least one storage vessel (1) is thermally coupled with the cooling chamber (10) and/or the air condition unit (12).
The vehicle (2) according to claim 1, wherein the at least one storage vessel (1) is thermally coupled with the cooling chamber (10) and/or the air condition unit (12) by a heat exchanger (16) comprising a first heat transfer medium and a second heat transfer medium.
The vehicle (2) according to claim 2, wherein the first heat transfer medium circulates between the at least one storage vessel and the heat exchanger and the first heat transfer medium comprises part of the fuel.
The vehicle (2) according to claim 2 or 3, wherein the vehicle (2) comprises a compressor (18) for recirculation of the first heat transfer medium, wherein a discharge-side of the compressor (18) is connected with the at least one storage vessel (1).
The vehicle (2) according to any of claims 1 to 4, wherein the sorption medium is present in form of at least one monolith (3) and the at least one monolith (3) has an extension (11) in one direction in space in a range from 10 cm to 100 cm.
The vehicle (2) according to any of claims 1 to 5, wherein the at least one storage vessel (1) comprises at least one inlet (7) and at least one outlet (24).
The vehicle (2) according to any of claims 1 to 6, wherein the at least one storage vessel (1) comprises a wall (5) made of carbon fibre composite material.
The vehicle (2) according to any of claims 1 to 7, wherein the sorption medium is selected from the group consisting of activated charcoals, zeolites, activated aluminia, silica gels, open-pore polymer foams, metal hydrides, metal-organic frameworks (MOF) and combinations thereof.
The vehicle (2) according to any of claims 1 to 8, wherein the fuel comprises a gas selected from the group consisting of natural gas, shale gas, town gas, methane, ethane, hydrogen, propane, propene, ethylene, carbon dioxide and combinations thereof.
A process for operation of a vehicle (2) according to any of claims 1 to 9, comprising
a. a filling step, wherein
i. the at least one storage vessel (1) is filled with the fuel,

ii. the fuel is contacted with the sorption medium,

iii. the fuel is filled into the at least one storage vessel (1) until a loading with fuel of 250 g/L, referring to the total inner volume (22) of the at least one storage vessel (1), is reached and

iv. during filling, the at least one storage vessel (1) is cooled and a maximum temperature T_max, referring to a spatial maximum, in the at least one storage vessel (1) does not exceed 85°C
and/or, after filling is completed, the maximum temperature T_max is decreased to less than 35°C and

b. a driving step, wherein
i. part of the fuel, filled in the at least one storage vessel (1), is conducted from the at least one storage vessel (1) to the internal combustion engine (8) and combusted in the internal combustion engine (8),

ii. the cooling chamber (10) and/or the air condition unit (12) is cooled by transferring heat from the cooling chamber (10) and/or the air condition unit (12) to the at least one storage vessel (1).
The process according to claim 10, wherein in the filling step (a), during filling, the maximum temperature T_max in the at least one storage vessel (1) does not exceed 80°C.
The process according to claim 10 or 11, wherein in the filling step (a) a flow-through is established in the at least one storage vessel (1), wherein a flow of the fuel out of the at least one storage vessel (1) exceeds 0 kg/h.
The process according to any of claims 10 to 12, wherein in the filling step (a) at least 90% of the maximum sorption capacity of the sorption medium, referring to the fuel, is reached at an absolute pressure in the at least one storage vessel (1) in a range from 80 bar to 100 bar.
The process according to any of claims 10 to 13, wherein in the filling step (a) the fuel is filled into the at least one storage vessel (1) until an absolute pressure of at least 200 bar in the at least one storage vessel (1) is reached.
The process according to any of claims 10 to 14, wherein the vehicle (2) comprises more than one storage vessel (1) and at least one of the storage vessels (1) is in the filling step (a) filled with the fuel only until not more than 98% of the maximum sorption capacity of the sorption medium is reached.
The process according to any of claims 10 to 15, wherein the vehicle (2) comprises the compressor (18) and in the driving step (b) the fuel is recirculated from the at least one storage vessel (1) to the compressor (18) and back to the at least one storage vessel (1).