EP2665624A1

EP2665624A1 - Mobile fuel delivery unit for compressed natural gas, method of distributing natural gas using a mobile fuel delivery unit for compressed natural gas

Info

Publication number: EP2665624A1
Application number: EP12702327.3A
Authority: EP
Inventors: Wilhelmina Walthera Cornelia Van Seumeren-Aussems
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-01-19
Filing date: 2012-01-18
Publication date: 2013-11-27
Also published as: WO2012099469A1; NL2006033C2

Abstract

Mobile fuel delivery unit for compressed natural gas, comprising : a storage tank for liquid natural gas, a gas delivery system for compressed gaseous natural gas, a feed conduit from storage tank to gas delivery system, which feed conduit is provided with an inlet valve, wherein the gas delivery system comprises at least the following components: an evaporator, a high-pressure pump, a gas dispensing unit downstream of evaporator and high-pressure pump, wherein the components are connected in series to each other by conduits, and wherein the assembly of storage tank and gas delivery system forms an integrated whole, this assembly being suitable for transport.

Description

Mobile fuel delivery unit for compressed natural gas, method of distributing natural gas using a mobile fuel delivery unit for compressed natural gas

The present invention relates to a mobile fuel delivery unit for compressed natural gas.

In the context of this invention compressed natural gas is understood to mean: natural gas in gaseous state and with an increased pressure of 100 bar or higher. In the field this form of compressed natural gas is also referred to with the international term 'compressed natural gas' and

abbreviated to CNG. Both terms will be used in the

following, and have the same meaning here unless otherwise stated. It is noted for the sake of completeness that methane gas forms the main constituent of natural gas.

In the 1970s and 1980s CNG began to be applied as alternative fuel for combustion engines in vehicles. A distribution system for CNG is applied here which is based on supplying liquid natural gas (LNG) using tankers and delivering LNG to filling stations, wherein the filling station is provided with an installation in which LNG is converted to CNG, which is then stored under high pressure.

The supply of natural gas to filling stations is economically most advantageous when the natural gas is transported in liquid form (LNG) in a cryogenic storage tank. LNG has a considerably higher energetic value per unit of volume than CNG. The drawback of LNG however is that filling stations must be provided with quite an extensive installation in which LNG is evaporated and in gas form compressed to CNG with a high pressure of 100 bar or higher.

An alternative is to fill gas cylinders with CNG at a central point and distribute these cylinders using trucks. It is thus not necessary to place a conversion installation at every delivery point. The drawback does then arise that transport becomes relatively expensive. Applicant therefore began researching a fuel delivery system for compressed natural gas which provides a solution to the above stated drawbacks and can moreover also be utilized for applications other than filling stations.

In order to achieve this object the invention relates, according to a first aspect thereof, to a mobile fuel delivery unit for compressed natural gas, comprising:

a storage tank for liquid natural gas,

a gas delivery system for compressed gaseous natural gas,

a feed conduit from the storage tank to the gas delivery system, which feed conduit is provided with an inlet valve,

wherein the gas delivery system comprises at least the following components:

an evaporator,

a high-pressure pump,

a gas dispensing unit downstream of evaporator and high-pressure pump,

wherein the components are connected in series to each other by conduits,

and wherein the assembly of storage tank and gas delivery system forms an integrated whole, this assembly being suitable for transport.

The storage tank for LNG is by definition a cryogenic storage tank. It has been found possible to provide such a complete fuel delivery unit, including an LNG storage tank, in mobile manner and suitable for transport on for instance a truck or a truck with trailer. The transport means themselves do not in principle have to undergo major modifications for this purpose.

The fuel delivery unit is preferably mounted on a support frame which can be placed directly onto the transport means. The support frame can more preferably be placed in lockable manner on the transport means. The above outlined drawbacks to delivery of CNG at filling stations are thus obviated. The delivery unit according to the invention moreover also provides an

economically advantageous way of delivering CNG for purposes other than for filling stations.

It is otherwise noted that in the context of the invention use can also be made of biogas, or of a mixture of natural gas and biogas, instead of natural gas. Biogas provides the additional advantage that use is made of a more environmentally-friendly and durable variant of methane gas, compared to natural gas. Compressed biogas is often referred to in this respect with the acronym CBG, and liquid biogas with the acronym LBG.

The evaporator according to the invention is an

expansion chamber which, with heat exchange, allows supplied liquid natural gas to expand and transpose to the gas phase. The heat exchange takes place by heat conduction via the walls of the expansion chamber, whereby heat exchange takes place between the interior of the expansion chamber and the exterior of the expansion chamber. The walls preferably have a high specific surface area on the inner side, for instance in the form of fins or a honeycomb. On the outside the walls are in contact with a surrounding area which can supply heat, for instance ambient air or heated cooling liquid from a combustion engine. The supplied heat supports the

evaporation of liquid natural gas in the expansion chamber.

The high-pressure pump according to the invention can also be designated a compressor.

The mobile fuel delivery unit according to the

invention preferably also comprises:

a liquid delivery system for liquid natural gas, a feed conduit from the storage tank to the liquid delivery system, which feed conduit is provided with an inlet valve,

wherein the liquid delivery system comprises at least the following components: a low-pressure pump,

a liquid dispensing unit downstream of the low-pressure pump,

wherein the components are connected in series to each other by conduits.

Both liquid natural gas and gaseous natural gas can thus be delivered using the delivery unit. This provides advantages of efficiency when both forms of natural gas must be delivered in a region or at a single location.

In the mobile fuel delivery unit according to the invention the feed conduit to the gas delivery system and the feed conduit to the liquid delivery system are more preferably combined into one feed conduit system, and wherein the inlet valve is embodied as a three-way valve. The unit as a whole thus has a simpler construction.

In the mobile fuel delivery system according to the invention it is additionally recommended that the liquid dispensing unit is adapted to dispense liquid natural gas, and the gas dispensing unit is adapted to dispense

compressed gaseous natural gas. The gas dispensing unit for instance comprises a flexible hose with an outlet at the outer end which can withstand a pressure of a minimum of 100 bar, particularly of 300 bar or more. The liquid dispensing unit for instance comprises a flexible hose with a

dispensing nozzle at the outer end which can withstand a pressure of 20 bar or more.

A variant of the mobile fuel delivery unit according to the invention is further provided with a control unit for performing measurements on and for operating the gas delivery system and/or the liquid delivery system. The quality of the CNG or LNG can thus be monitored and

optionally adjusted as required before the fuel is delivered via the dispensing unit.

It is recommended here that the control unit of the mobile fuel delivery unit according to the invention is provided with a telemetry function for transmitting information between the control unit and a remote information-processing station. The telemetry function is for instance based on a transmitter/receiver of a GSM-modem type. It is thus possible at a central information- processing station to track the progress of distribution of LNG/CNG from the storage tank for the purpose of the

coordinating logistical process.

In a subsequent variant of the mobile fuel delivery unit according to the invention the high-pressure pump for compressing gaseous natural gas is suitable for compression up to a pressure of at least 100 bar. CNG can thus be delivered under a commonly used high pressure. The

compressor can preferably compress the natural gas up to a pressure of 200 bar, and more preferably a pressure of 300 bar. Natural gas can thus be stored with the highest

possible energetic value per unit of volume. The nominal capacity is preferably 25-50 litres/minute.

In the mobile fuel delivery unit according to the invention a measuring unit is with special preference placed at the position of one or both dispensing points for the purpose of measuring properties of the dispensed fluid flow. This measuring unit is preferably coupled to the control unit. Such measurements are important for recording the amount of fuel delivered by the fuel delivery unit (for the purpose of the logistic distribution process) and for monitoring the quality of the delivered CNG or LNG, as well as the temperature and the pressure of the delivered fuel.

In a subsequent variant of the mobile fuel delivery unit according to the invention an injector system for an odorant is coupled to the gas dispensing unit.

Tetrahydrothiophene is preferably used here as odorant. This is a commonly used odorant which is added to gaseous natural gas to enable immediate detection of an undesirable leakage. The CNG delivered by the system according to the invention can thus be detected in the same manner and thereby complies with the same safety requirements as usual natural gas supplied from a natural gas network.

In the mobile fuel delivery unit according to the invention natural gas with a methane content of 95% by volume or higher is more preferably present in the storage tank. The methane content is preferably at least 96% by volume, more preferably at least 97% by volume, most preferably at least 98% by volume. As noted above, the natural gas can also be replaced here by biogas, or a mixture of both.

Owing to the increased methane content the compressed natural gas (CNG) delivered by the fuel delivery unit has a high calorific value such that the CNG forms a realistic alternative to the generally used LPG as fuel for heating purposes. In this respect the CNG is also referred to as ^igh-calorific natural gas' because it has a 20% higher calorific value than is usual for naturally obtained natural gas. Such an application of natural gas under high pressure for heating purposes has not previously been considered in the field.

According to a preferred embodiment of the mobile fuel delivery unit according to the invention the high-pressure pump is disposed upstream of the evaporator, or the

evaporator is disposed upstream of the high-pressure pump. The first disposition requires a high-pressure evaporator and a high-pressure pump for liquids of the plunger type. The second disposition requires a low-pressure evaporator, and a high-pressure pump for gases.

Both dispositions have their advantages and

disadvantages:

A high-pressure pump for gas consumes more energy than a high-pressure pump for liquids, and for this reason the disposition of a high-pressure pump with a high-pressure evaporator downstream can be recommended. On the other hand, a better control of the temperature of the gas carried to the gas dispensing unit can be achieved with a low-pressure evaporator and a high-pressure pump for gas arranged

downstream thereof. This control of the delivery temperature is more difficult from a high-pressure evaporator and requires more modifications, i.e. control and measuring equipment. One of these two dispositions will thus be chosen subject to the above stated considerations.

The high-pressure pump for liquids preferably produces an output pressure of 100 bar or higher, preferably higher than 300 bar. The nominal capacity is preferably 25-50 litres/minute.

In the mobile fuel delivery unit according to the invention the gas delivery unit is preferably suitable for gas dispensing of CNG with a maximum pressure of 300-380 bar, at a maximum dispensing capacity of 25-50

litres/minute. The maximum dispensing capacity is preferably 25 litres/minute.

The gas dispensing preferably takes place at ambient temperature or the equilibrium temperature inherent to the obtained volume of gas in the evaporator at a given pressure (according to Boyle's Law) . If desired, the temperature during gas dispensing can also lie between these two values.

In the mobile fuel delivery unit according to the invention the liquid delivery unit is more preferably suitable for liquid dispensing of LNG with a maximum

pressure of 10-30 bar, at a maximum dispensing capacity of 100-300 litres/minute. The maximum dispensing capacity is preferably 200 litres/minute, and the maximum pressure is preferably 20 bar.

The liquid dispensing preferably takes place at the equilibrium temperature inherent to the obtained volume of liquid at a given pressure. This temperature can correspond to what is usual for already known systems.

According to a second aspect, the invention relates to a method for distribution of natural gas, wherein compressed gaseous natural gas is delivered making use of a mobile fuel delivery unit according to the invention. Such a method makes it possible to perform the distribution of compressed gaseous natural gas more efficiently than in the methods known from the prior art. The associated advantages can moreover be achieved using the measures described above as preferred embodiments of the system.

The invention preferably relates to a method for distribution of natural gas, wherein liquid natural gas is also delivered making use of a mobile fuel delivery unit according to the invention. The advantages specifically elucidated above for the combined distribution of CNG and LNG are achieved with this method.

The invention will be elucidated herein below with reference to the accompanying figures, in which:

Figure 1 shows a side view of a truck on which a fuel delivery unit is placed according to an embodiment of the invention;

Figure 2 shows a side view of a trailer associated with a truck-trailer combination on which a fuel delivery system is placed according to an alternative embodiment of the invention;

Figure 3 is a schematic representation of the fuel delivery unit according to an embodiment of the invention;

Figure 4 is a schematic representation of the fuel delivery unit according to an alternative embodiment of the invention .

Fig. 1 shows a truck 1 provided with the main

components of the fuel delivery unit according to the invention, i.e. a storage tank 3 for LNG, an evaporator 5, a pump system 7, a combined dispensing unit 9 and a CNG storage 11. The components are connected serially to each other via conduits (not shown) . Further details of the relative arrangement of the components are further shown in fig. 3 and 4. The pump system comprises a high-pressure pump for CNG and a low-pressure pump for LNG (not shown) . Dispensing unit 9 comprises both a liquid dispensing unit and a gas dispensing unit. CNG storage 11 comprises

cylinders filled with CNG which serve as storage for distribution and as fuel storage for the engine of truck 1, which has been made suitable for CNG. This embodiment is explained with reference to LNG and CNG but is of course also suitable for LBG and CBG, or mixtures of both forms of methane gas. The same variation also applies to the figures described below.

Fig. 2 shows a trailer 20 as part of a truck-trailer combination. The trailer is provided with the same

components as already described for fig. 1, which are shown with the same numbering.

Fig. 3 shows a schematic flow diagram of a fuel delivery unit 30 in which the above described components retain the same numbering. Feed conduits 32 are provided with a three-way valve 34 and lead to a high-pressure pump of the plunger type 7A or to a low-pressure liquid pump 7B. By means of three-way valve 34 LNG can be carried from tank 3 to a gas delivery system (upper route beginning at pump 7A) or a liquid delivery system (lower route beginning at pump 7B) . Natural gas flows through both delivery systems from left to right as indicated with arrows.

The gas delivery system comprises the following components, which are connected in series by means of conduits 34: a high-pressure pump 7A, a high-pressure evaporator 5, a gas dispensing unit 9A. Gas dispensing unit 9A comprises: a gas pressure regulator 36, an odour injector system 38, a measuring system 40 for gas dispensing (type: Coriolis CNG 50) and a hose 42 provided with an outlet (not shown) such as a CNG nozzle. Inside the gas delivery system diverse components are electronically connected to control unit 50 via connections 45. In the control unit the data sent from measuring systems of components are on the one hand processed, and control signals are on the other hand generated to the components. The connections 46 are signals coming from the LNG tank and relate to the pressure in the tank and the amount of fuel present in the tank.

The liquid delivery system comprises the following components: a low-pressure LNG liquid pump 7B, a conduit 60 and a liquid dispensing unit 9B . The liquid dispensing unit 9B comprises a measuring system 62 for gas dispensing (type: Coriolis CMF 100) and a hose 64 provided with an outlet (not shown) such as a dispensing nozzle.

Fig. 4 shows a schematic flow diagram of a fuel

delivery unit 70 having largely the same construction as described above for fig. 3, in which the same components retain the same numbering. The only difference with fig. 3 is that the serial disposition of the evaporator and the high-pressure pump is reversed in the gas delivery system: when feed conduit 34 is followed from three-way valve 34, a low-pressure evaporator 75 into which LNG is introduced in gas form is first reached in the upper route, and a high- pressure gas pump 77A is then reached via conduit 34.

The components of the fuel delivery unit according to the invention preferably meet the following specifications:

Storage tank for LNG: cryogenic pressure container with a volume of 13, 000 litres and an internal pressure of up to 12.6 bar .

Inside the unit the liquid pump for the liquid delivery system (for LNG) is placed at a position about a metre lower than the suction height in the storage tank. Sufficient hydrostatic overpressure (about 0.1 bar overpressure) is thus ensured.

The invention preferably comprises a hydraulic drive with a power of 40 kW per pump.

Claims

1. Mobile fuel delivery unit for compressed natural gas, comprising :

a storage tank for liquid natural gas,

a gas delivery system for compressed gaseous natural gas ,

wherein the gas delivery system comprises at least the following components:

an evaporator,

a high-pressure pump,

- a gas dispensing unit downstream of evaporator and

high-pressure pump,

wherein the components are connected in series to each other by conduits, and wherein the assembly of storage tank and gas delivery system forms an integrated whole, this assembly being suitable for transport,

also comprising:

wherein the liquid delivery system comprises at least the following components:

a low-pressure pump,

a liquid dispensing unit downstream of the low-pressure pump,

wherein the components are connected in series to each other by conduits.

2. Mobile fuel delivery unit as claimed in claim 1, wherein the feed conduit to the gas delivery system and the feed conduit to the liquid delivery system are combined into one feed conduit system, and wherein the inlet valve is embodied as a three-way valve.

3. Mobile fuel delivery unit as claimed in any of the foregoing claims, wherein the liquid dispensing unit is adapted to dispense liquid natural gas, and the gas

dispensing unit is adapted to dispense compressed gaseous natural gas. 4. Mobile fuel delivery unit as claimed in any of the foregoing claims, provided with a control unit for

performing measurements on and for operating the gas delivery system and/or the liquid delivery system. 5. Mobile fuel delivery unit as claimed in claim 4, wherein the control unit is provided with a telemetry function for transmitting information between the control unit and a remote information-processing station. 6. Mobile fuel delivery unit as claimed in any of the foregoing claims, wherein the high-pressure pump for compressing gaseous natural gas is suitable for compression up to a pressure of at least 100 bar. 7. Mobile fuel delivery unit as claimed in any of the foregoing claims, wherein a measuring unit is placed at the position of one or both dispensing units for the purpose of measuring properties of the dispensed fluid flow. 8. Mobile fuel delivery unit as claimed in any of the foregoing claims, wherein an injector system for an odorant is coupled to the gas dispensing unit.

9. Mobile fuel delivery unit as claimed in any of the foregoing claims, wherein natural gas with a methane content of 95% by volume or higher is present in the cryogenic storage tank.

10. Mobile fuel delivery unit as claimed in any of the foregoing claims, wherein the high-pressure pump is disposed upstream of the evaporator, or the evaporator is disposed upstream of the high-pressure pump. 11. Mobile fuel delivery unit as claimed in any of the foregoing claims, wherein the gas delivery unit is suitable for gas dispensing of CNG with a maximum pressure of 300-380 bar, at a maximum dispensing capacity of 25-50

litres/minute .

12. Mobile fuel delivery unit as claimed in any of the foregoing claims, wherein the liquid delivery unit is suitable for liquid dispensing of LNG with a maximum

pressure of 10-30 bar, at a maximum dispensing capacity of 100-300 litres/minute.

13. Method for distribution of natural gas, wherein compressed gaseous natural gas is delivered making use of a mobile fuel delivery unit as claimed in any of the foregoing claims.

14. Method for distribution of natural gas as claimed in claim 13, wherein liquid natural gas is also delivered making use of a mobile fuel delivery unit according to any of the foregoing claims 1-12.