Patent Publication Number: US-11396978-B2

Title: Refuelling method and device for supplying liquefied gases and the like

Description:
The present invention relates to a refuelling method and device for supplying liquefied gases and the like of the type as recited in the preamble of the independent claims. 
     In particular, the invention relates to a method and device for supplying LNG, i.e. liquefied natural gas. It is suitable to allow the refuelling of a vehicle such as preferably a ship. 
     As is well known, ship refuelling requires a tanker truck filled with LNG to be positioned on a quay near the ship to be refuelled; the connection of the reservoir to the tank of the ship and then the LNG feeding by a pump from the reservoir into the tank. 
     The prior art described above has some notable drawbacks. 
     A first important drawback lies in the fact that several reservoirs have to be used to fill a ship. In detail, this filling process involves the sequential use of reservoirs in order to avoid problems related to the flow of LNG and in particular to the pump operation control. 
     Therefore, the process is slow and particularly expensive. 
     Another important drawback is that, due to the tank emptying (with a consequent risk of pump cavitation) and/or the tank filling (with an increased duration of the operation), the conditions of the fluids in the reservoir and/or in the tank evolve constantly, thus making the pump regulation process very complex. 
     To overcome these problems, the reservoirs are provided with a vaporizer that draws LNG from the reservoir, vaporizes it and introduces it into the reservoir, by counterbalancing the pressure lowering. 
     However, the amount of steam produced by the vaporizer does not allow to rebalance the pressure loss due to the emptying of the reservoir, and it does not overcome this problem definitively. 
     In addition, the amount of vaporized LNG is not introduced into the tank and is therefore lost, which leads to increasing costs. 
     It should be noted that the drawback mentioned above is amplified by the operator&#39;s difficulties in managing the different pressures in the reservoirs. 
     In this context, the technical task underlying the present invention is to develop a refuelling method and device for supplying liquefied gases, able to substantially overcome at least some of the drawbacks mentioned above. 
     Within the sphere of said technical task one important aim of the invention is to provide a refuelling method and device for supplying liquefied gases, that is simple to control, fast and inexpensive. 
     The technical task and the specified aims are achieved with a refuelling method and device for supplying liquefied gases as claimed in the appended independent claims. Examples of preferred embodiments are described in the dependent claims. 
     Preferred embodiments are set forth in the dependent claims. 
     The features and advantages of the invention will be apparent from the following detailed description of preferred embodiments thereof, with reference to  FIG. 1  showing a diagram of the device for supplying liquefied gases according to the invention. 
     Herein, the measures, values, shapes and geometric references (such as perpendicularity and parallelism), when used with words like “about” or other similar terms such as “approximately” or “substantially”, are to be understood as except for measurement errors or inaccuracies due to production and/or manufacturing errors and, above all, except for a slight divergence from the value, measure, shape or geometric reference which it is associated with. For example, these terms, if associated with a value, preferably indicate a divergence of not more than 10% from said value. 
     Furthermore, when used, terms such as “first”, “second”, “higher”, “lower”, “main” and “secondary” do not necessarily identify an order, a priority relationship or a relative position, but can simply be used to distinguish more clearly the different components from each other. 
     Unless otherwise indicated, the measurements and data provided in this document are to be considered using International Standard Atmosphere ICAO (ISO 2633). Unless otherwise specified, as is apparent from the following discussion, terms such as “treatment”, “data processing”, “determination”, “calculation”, or the like, are understood to refer to the action and/or processes of a computer or similar electronic computing device which manipulates and/or transforms data represented as physical, such as electronic sizes of registers of a computer system and/or memories, into other data similarly represented as physical quantities in computer systems, registers or other storage, transmission or information display devices. 
    
    
     
       With reference to the Figures, reference numeral  1  globally denotes the device for supplying liquefied gases according to the invention. 
     
    
    
     The term liquefied gases identifies all liquids obtained by liquefaction of a gas, suitably combustible, so as to reduce, even by 600 times, the specific volume thereof, compared to standard conditions. In order to keep the gas in the liquid phase, the liquefied gas is stored at a liquefaction temperature (usually −160° C.) which is lower than the ambient temperature (the temperature at which the gas is in the gas phase). 
     The liquefied gas is preferably LNG. 
     The refuelling device  1  is adapted to use at least one refuelling reservoir  1   a  containing the liquefied gas to refuel one or more tanks  1   b , usually one or two tanks  1   b.    
     Preferably the refuelling device  1  is suitable to use more than one reservoirs  1   a , in particular working in parallel, to refuel simultaneously one or more tanks  1   b  (for example one or two). 
     Preferably the reservoirs  1   a  are between three and seven, more preferably four. One or more reservoirs  1   a  can be static, i.e. integrally fastened to the ground; and/or mobile and, for example, moveable by truck. 
     The tank  1   b  can be the tank of a vehicle and in particular of a ship. 
     If several tanks  1   b  are connected to the device  1 , the tanks  1   b  may be part of a single vehicle, and in particular of a single ship, or of several vehicles, and in particular of several ships. 
     The refuelling device  1  comprises a fluid feed system  2  from the at least one reservoir  1   a  to the at least one tank  1   b ; and preferably a pressurisation system  3  of the one or more reservoirs  1   a.    
     The feed system  2  is adapted to place at least a reservoir  1   a  in fluidic through connection with the at least one tank  1   b  thereby allowing the liquefied gas to pass from said at least one reservoir  1   a  to said at least one tank  1   b.    
     Preferably, the feed system  2  is adapted to place a plurality of reservoirs  1   a , appropriately four, in fluidic through connection with the at least one tank  1   b  at the same time so that the liquefied gas passes simultaneously from each reservoir  1   a  to one or more tanks  1   b.    
     The feed system  2  may comprise, for each reservoir  1   a , a withdrawal duct  21  for withdrawing liquefied gas from said reservoir  1   a.    
     The feed system  2  may comprise, for each reservoir  1   b , an inlet duct  22 , preferably only one, of the liquefied gas to the reservoir  1   b.    
     In the case of one withdrawal duct  21  and one inlet duct  22 , the ducts  21  and  22  are in direct fluidic through connection so that the liquefied gas passes from the withdrawal duct  21  directly to the inlet duct  22 . In this case, the ducts  21  and  22  can identify only one duct. 
     In the case of several withdrawal ducts  21  (i.e. several reservoirs  1   a ), the feed system  2  may comprise a collection manifold  23  placing the withdrawal ducts  21  simultaneously in fluidic through connection with the inlet duct  22 , thus placing the reservoirs  1   a  in parallel. 
     The collection manifold  23  is then adapted to convey the liquefied gas exiting from the withdrawal ducts  21  into the inlet duct  22 . It is interposed between the ducts  21  and  22 . 
     In the case of several tanks  1   b , the feed system  2  may comprise a distributor  24  placing the inlet duct  22  simultaneously in fluidic through connection with the tanks  1   b.    
     The distributor  24  can be provided with a flow regulating device  24   a  for each tank  1   b.    
     The flow regulating device  24   a  is adapted to regulate the flow entering a tank  1   b , for example, by allowing the device  1  to refuel or not the tank  1   b  connected to it. The flow regulating device  24   a  can be external to the device  1  and part of a tank  1   b.    
     The feed system  2  may comprise at least one pump  25  adapted to move the liquefied gas in the feed system  2  and, therefore, from the at least one reservoir  1   a  to the tank  1   b.    
     In the case of several reservoirs  1   a  the at least one pump  25  is adapted to simultaneously control the withdrawal of liquefied gas from all reservoirs  1   a  which are then emptied in parallel. 
     In detail, the feed system  2  may comprise one pump  25  suitably integrated in the inlet duct  22 . It is suitable for withdrawing the liquefied gas simultaneously from the reservoirs  1   a  as it is located downstream of the manifold  23 . 
     In this document, the terms “downstream” and “upstream” refer to the direction of advancement of the liquefied gas in the feed system  2  and of the filling gas (described below) in the pressurisation system  3 . 
     Alternatively, the feed system  2  may comprise a plurality of pumps  25 , one for each withdrawal duct  21 , such pumps being suitable to operate in parallel so as to withdraw the liquefied gas simultaneously from the reservoirs  1   a.    
     Each pump  25  is integrated in the withdrawal duct  21 . 
     Preferably the operating parameters of the pumps  25  are identical. 
     Since said pumps  25  are simultaneously in fluidic through connection with a single inlet duct  22 , they define substantially the same outlet pressure. Each pump  525  mutually influences the output pressure (described below) of all other pumps  25 . 
     Preferably the pumps  25  are the only pumps of the device  1 . 
     The feed system  2  may comprise for each pump  25   a  pressure gauge  26  for the inlet pressure of the liquefied gas in the pump  25 . 
     The pressure gauge  26  is upstream of the pump  25 . It is adapted to be interposed between the pump  25  and the reservoir  1   a.    
     It should be noted that, being measured upstream of the pump  25 , the inlet pressure can substantially correspond to that of the reservoir  1   a.    
     The pressure gauge  26  can be used to measure said inlet pressure of the liquefied gas in the inlet duct  22 . It is integrated in the inlet duct  22  (in the case of a single pump  25 ). 
     Alternatively, the pressure gauge  26  can be adapted to measure the inlet pressure in the withdrawal duct  21 . It is then integrated into the withdrawal duct  21 . In particular, in the case of several pumps  25 , the feed system  2  may comprise several gauges  26 , one for each withdrawal duct  21 . 
     The feed system  2  may comprise at least one pressure meter  27  for the outlet pressure of the liquefied gas exiting from at least one pump  25 . 
     The pressure meter  27  is downstream of the pump  25 . It is therefore suitable for interposing between the pump  25  and the tank  1   b.    
     The feed system  2  may comprise only one pressure meter  27  adapted to measure the outlet pressure in the inlet duct  22 . It is integrated in the inlet duct  22 . 
     Alternatively, the feed system  2  may comprise several pressure meters  27 . Each of them is adapted to measure said outlet pressure in a withdrawal duct  21  downstream of said pump  25  and then integrated in a withdrawal duct  21  ( FIG. 1 ). The feed system  2  may comprise at least one regulating valve  28  to regulate, suitably automatically, the flow of liquefied gas in at least the inlet duct  22  according to the inlet and/or outlet pressure and preferably to their difference. 
     The regulating valve  28  is downstream of the pump  25  and preferably of the pressure meter  27 . 
     The feed system  2  may comprise several regulating valves  28 , each integrated in a withdrawal duct  21  and adapted to regulate the flow of liquefied gas in a withdrawal duct  21  and consequently in the collection manifold  23  and in the inlet duct  22 . 
     Preferably, the feed system  2  comprises only one regulating valve  28  integrated in the inlet duct  22 . 
     The regulating valve  28  is adapted to regulate the operation of pump  25 , keeping it in the optimal operating range/curve. 
     In particular, it is adapted to adjust the flow downstream of the pump  25 , thus maintaining a constant difference between the outlet and inlet pressure. In accordance with said difference between the outlet and inlet pressures, the regulating valve  28  provides operating parameters for the pump  25  so as to keep it within the optimal operating range. 
     Preferably the regulating valve  28  is adapted to adjust the operating parameters of the pumps  25  keeping them equal to each other. 
     In  FIG. 1  the pressurization system  3  is shown—unlike the adduction system  2 —with a dotted line to facilitate the distinction between the two systems  2  and  3 . 
     The pressurisation system  3  is adapted to operate by counteracting the lowering of the pressure in the reservoir  1   a  due to the withdrawal of liquefied gas, preferably by keeping the pressure in the reservoir  1   a  almost constant during refuelling. 
     In particular, it is adapted to increase the pressure in one or more reservoirs  1   a  with a pressure lower than at least one tank  1   b.    
     The pressurisation system  3  can be adapted to perform this function by introducing into the reservoir  1   a  a filling gas, suitably steam. 
     The pressurisation system  3  may comprise a return line  31  adapted to withdraw the filling gas, for example, from an external apparatus such as a cylinder/external circuit of natural gas or other filling gas, preferably an inert gas. 
     The pressurisation system  3  may comprise, for each reservoir  1   a , a second duct  32  adapted to carry the filling gas from the return line  31  to a reservoir  1   a.    
     The second duct  32  is adapted to be placed in fluidic through connection with a reservoir  1   a.    
     In the case of several reservoirs  1   a , the pressurisation system  3  is adapted to provide parameters for the reservoirs  1   a  which are almost equal to each other. In particular, it may comprise a connecting member  33  adapted to place the reservoirs  1   a  in reciprocal fluidic through connection so as to place said reservoirs under the same pressure. 
     Preferably, the pressurisation system  3  is adapted to equalise the pressures of the reservoirs  1   a  by introducing a filling gas into them. It can thus comprise a return line  31 ; several conduits  31  (one for each reservoir  1   a ), and a connecting member  33  interposed between the return line  31  and the duct  32  so that the return line  31  is in fluidic through connection simultaneously with all the ducts  32 . 
     The pressurization system  3  may comprise a compressor upstream of the connection member  3  so as to place the member  33  and the ducts  32  under the same pressure. 
     Advantageously, the pressurization system  3  is devoid of compressors, i.e. it has a natural circulation. The passage of the filling gas from the at least one tank  1   b  to said one or more reservoirs  1   a  occurs through natural circulation and it is therefore controlled by the pressure drop of the reservoirs  1   a  during refuelling. 
     Preferably, the filling gas is the boil-off in at least one tank  1   b  (in this document the term boil-off identifies the portion of liquefied gas in the tank  1   b  which turned to the gaseous state) and the return line  31  is adapted to be placed in fluidic through connection with said at least one tank  1   b.    
     The pressurisation system  3  is adapted to place in flidic through connection said at least one tank  1   b  with said at least one reservoir  1   a.    
     As a result, the inlet and outlet pressures of the pump  25  can be reduced as much as possible and in particular adjusted keeping the pump in the optimal operating field/curve. 
     In the case of a single tank  1   b  the return line  31  can be identified as a duct. 
     In the case of several tanks  1   b  the return line  31  comprises a collection body  31   a  for the filling gas (the boil-off) exiting the tanks  1   b.    
     The collection body  31   a  is adapted to convey and then introduce the filling gas from the tanks  1   b  into the duct  32  in the case of one reservoir  1   a  or into the connecting member  33  in the case of several reservoirs  1   a.    
     In addition, in the case of several tanks  1   b , the return line  31  may comprise, in addition to the collection body  31   a , means of regulation  31   b  of the gas flow exiting each tank  1   b.    
     The means of regulation  31   b  are therefore only adapted to control the passage of filling gas from the tank  1   b  to the reservoir  1   a  if the pressure in the tank  1   b  exceeds a predefined threshold and in particular the pressure in at least one reservoir  1   a.    
     The means of regulation  31   b  may be external to device  1  and part of a tank  1   b.    
     Each duct  32  may comprise at least one closing block (not shown in the FIGURE) adapted to measure the pressure in a duct  32  and selectively allow the fluid to pass to the reservoir  1   a  only if the pressure in that reservoir  1   a  is less than tank  1   b.    
     A closing block may be external to the device  1  and part of a reservoir  1   a.    
     To selectively control the flow of fluid from the at least one tank  1   b  to the at least one reservoir  1   a  the pressurisation system  3  may comprise a flow control valve  34  in the pressurisation system  3 . 
     The control valve  34  can be integrated in a duct  32  or preferably in the return line  31 . 
     The control valve  34  can be integrated in a duct  32  or preferably in the return line  31 . 
     It is adapted to control the fluid flow only if the filling gas pressure upstream of the control valve  34  and therefore in the tank  1   b  is higher than the filling gas pressure downstream of the control valve  34  and therefore in the reservoir  1   a.    
     In order to control the opening and/or closing of the control valve  34 , the pressurisation system  3  may comprise a first sensor  35  adapted to measure the filling gas pressure upstream of the control valve  34 ; a second sensor  36  adapted to measure the filling gas pressure downstream of the control valve  34 . 
     The control valve  34  is therefore only adapted to control the passage of fluid if the pressure measured by the first sensor  35  is greater than the pressure measured by the second sensor  36 . 
     The refuelling device  1  may comprise a control unit for the operation of the device  1  described below. 
     It is adapted to control at least one regulating valve  28  and/or at least one pump  23  preferably according to the data collected by pressure gauge  26  and/or pressure meter  27  as described above. 
     The control unit is also adapted to control the control valve  34  according to the pressure in the reservoir  1   a  and/or in the tank  1   b.    
     It comprises a PLC. 
     The invention comprises a new refuelling method for supplying liquefied gases preferably implemented through the refuelling device  1  described above. 
     This method describes the operation of the refuelling device  1 . 
     The refuelling process is adapted to refuel at least one tank  1   b  (suitably one or two tanks  1   b ) using at least one reservoir  1   a  and preferably using several reservoirs  1   a  in parallel, simultaneously. 
     The refuelling process provides a refuelling step and a pressurization step. 
     Advantageously, the refuelling method requires that the refuelling and pressurisation steps are carried out simultaneously so that the filling gas counteracts the lowering of pressure in reservoir  1   a.    
     During the refuelling step, the liquefied gas is transferred from said reservoir  1   a  to said tank  1   b . In detail, the at least one pump  25  controls the exit from said reservoir  1   a  of the liquefied gas which thus passes through the withdrawal duct  21 , the inlet duct  22  and enters the tank  1   b.    
     This withdrawal of liquefied gas causes a lowering of the pressure of the reservoir  1   a.    
     Simultaneously, the pressurization step takes place. 
     This pressurisation step takes place only if between reservoirs  1   a  and tanks  1   b  meeting the requirement of having the pressure in at least one tank  1   b  greater than that in at least one reservoir  1   a.    
     In the pressurization step, the pressurization system  3  works by counteracting the lowering of the pressure in the reservoir  1   a  due to the withdrawal of liquefied gas. During the pressurisation step, a filling gas (preferably the boil-off in the at least one tank  1   b ) is introduced into the reservoir  1   a.    
     At this step, the filling gas, driven by a compressor or preferably only controlled by said lowering of the pressure in reservoir  1   a , passes through the pressurization system  3  to enter the reservoir  1   a  by counteracting the lowering of the pressure and preferably maintaining the pressure of the reservoir  1   a  substantially constant, despite the withdrawal of liquefied gas. 
     Advantageously, the filling gas is the boil-off which, through the pressurisation system  3 , passes from the one or more tanks  1   b  to one or more reservoirs  1   a.    
     The refuelling method for supplying liquefied gases is preferably adapted to refuel a tank  1   b  using several reservoirs  1   a  in parallel at the same time. 
     In this case, during the refuelling step, the liquefied gas is simultaneously withdrawn from all reservoirs  1   a  and transferred to the tank  1   b ; and during the pressurisation step, the filling gas (preferably the boil-off in tank  1   b ) is simultaneously introduced into all reservoirs  1   a.    
     In particular, during the filling step, at least one pump  25  withdraws simultaneously a liquefied gas flow from all reservoirs  1   a . Each flow of liquefied gases passes through a withdrawal duct  21  and reaches the collection manifold  23  where it joins the other flows, forming a single flow that enters the tank  1   b  through the inlet duct  22 . 
     In detail, the liquefied gas flows exiting the reservoirs  1   a  are all identical. 
     The withdrawal step is carried out at the same time as the filling phase in which the pressures of the reservoirs  1   a  are made uniform and therefore they are made/kept substantially equal to each other. 
     Preferably during the filling step the filling gas (preferably the boil-off of the tank  1   b ) passes through the return line  31 , divides in the connecting member  33  in sub-flows suitably equal to each other. Each sub-flow passes through a duct  32  thereby entering a reservoir  1   a.    
     It should be noted that the reservoirs  1   a  show pressures which are almost equal to each other, since they all simultaneously placed in a fluidic through connection. 
     The refuelling method and device  1  according to the invention achieve some important advantages. 
     In fact, they allow to use simultaneously more reservoirs  1   a , without complex and laborious devices, and therefore in parallel. 
     This aspect is increased by the possibility of regulating the flow according to the inlet and preferably outlet pressure, thus adapting the working conditions of the pump  4  to those of the liquefied gas flow. More in particular, it is obtained by keeping the difference between outlet and inlet pressure substantially constant. This aspect is also achievable thanks to the possibility to maintain the pressures of said reservoirs  1   a  substantially equal to each other and in particular constant. 
     In particular, this solution is made possible by using the boil-off of the tank  1   b  (currently dispersed by combustion in the environment) and then by creating, through the pressurization system  3 , a second fluidic through connection (in particular, gas) between reservoirs  1   a  and tank  1   b  which can be exploited to have a flow working in parallel and counteracting the withdrawal of liquefied gas from the reservoir  1   a.    
     In conclusion, the refuelling method and the device  1  allow the working conditions of the different reservoirs  1   a  to be uniform, thus making it extremely simple and inexpensive to control the flow of liquefied gas and therefore the one or more pumps  25 . 
     This uniformity of the reservoirs  1   a  is ensured throughout the entire refuelling process. 
     The invention is subject to variations without departing from the scope of the inventive concept as defined in the claims. All details may be replaced with equivalent elements and the scope of the invention includes all other materials, shapes and dimensions.