Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/58—Cooling; Heating; Diminishing heat transfer
  • F04D29/582—Cooling; Heating; Diminishing heat transfer specially adapted for elastic fluid pumps
  • F04D29/584—Cooling; Heating; Diminishing heat transfer specially adapted for elastic fluid pumps cooling or heating the machine
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
  • F04B49/007—Installations or systems with two or more pumps or pump cylinders, wherein the flow-path through the stages can be changed, e.g. from series to parallel
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
  • F04D27/02—Surge control
  • F04D27/0269—Surge control by changing flow path between different stages or between a plurality of compressors; load distribution between compressors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/58—Cooling; Heating; Diminishing heat transfer
  • F04D29/582—Cooling; Heating; Diminishing heat transfer specially adapted for elastic fluid pumps
  • F04D29/5826—Cooling at least part of the working fluid in a heat exchanger

Definitions

• the present invention relates to the process of compression of natural gas for automotive use and more particularly to a high-energy efficiency automotive methane compression plant.
• the current technique in the sector of automotive methane compression plants envisages a pressure increase from the pressure found in the pipeline (which ranges from 4 bar to approx 40 bar) to 280 bar, required for filling operations, using a multistage compressor with intercooler.
• the system entails the construction of a compressor with suitable capacity for the requirements of the plant, related to the dispensing capacity commonly required once in operation.
• a cooling phase is needed between stages to lower the initial temperature of the compressed gas in each stage, thus reducing energy consumption, and to protect the compressor's seal parts.
• These systems therefore require single-acting or double-acting multi-cylinder compressors designed so that the respective volumes are appropriate for the density variations in a capacity that must be identical in each individual stage.
• Cooling requires large and consequently expensive systems, which considerably influence final plant cost, hi fact they need to cool the gas predominantly with air or with water circuits, hi addition, the compressor is subject to continuous starts and stops in relation to the gas withdrawn with each customer use. This is one of the principal factors affecting reliability, and requires appropriate overdimensioning in the design stage.
• a primary object of the present invention is to overcome the drawbacks of known plants by providing a plant operating with significantly higher energy efficiency.
• a second object of the invention is to provide plants capable of achieving the pressure changes enabled by known plants, using a much simpler and consequently less expensive design and one that is more reliable compared with similar known designs.
• An additional object of the invention is plants with a smaller compressor.
• a further object is to provide plants with compressors designed for continuous operation, more reliable than traditional compressors operating intermittently. In line with the invention such obj ects are met by a plant that - under claim 1 and/or any of the directly or indirectly dependent claims- uses a one-stage compressor and suitable intermediate storing systems at different pressures, placed in a cooled environment. From the pipeline pressure the gas is brought to low pressure via a single compression stage, it is stored, brought to medium pressure and finally to the final pressure.
• the pressure changes are achieved by the same compressor through a switch of delivery with suction.
• the compressor achieves the different pressures via different delivery periods according to the amount of gas stored in the cylinders.
• the customer's vehicle will be supplied first with low-pressure methane, then with medium-pressure and finally with maximum-pressure gas. This will provide for the total mass of gas required to achieve maximum pressure to be delivered into the vehicle's tanks or cylinders, thus saving the energy that would be needed to bring the whole mass to maximum pressure.
• - figure 2 is a functional diagram of the plant fed at ca. 20 bar showing the different pressure levels
• - figure 3a is a functional diagram of the stage where the low-pressure cylinder is fed by gas from the pipeline;
• FIG. 3b is a functional diagram of the stage where the medium-pressure cylinder is fed by gas from the low-pressure cylinder;
• FIG. 3c is a functional diagram of the stage where the high-pressure cylinder is fed by gas from the medium-pressure cylinder;
• FIG. 4 is a functional diagram of the customer dispensing stage, with multiple, successive fillings from the three different cylinders;
• FIG. 5 is a basic drawing of a plant constructed according to the disclosed invention, endowed with a stage of adjustment to pipeline suction pressure.
• 1 indicates a gas compression plant of the type endowed with a gas compressor 2 and a cylinder casing 3.
• the compressor 2 is a one-stage apparatus that is fed natural gas from the pipeline through a suction conduit 9 which channels the compressed gas to a feed conduit 10.
• the pipeline gas enters the suction conduit 9 of the compressor 2 at an initial pressure of ca. 20 bar and exits the feed conduit 10 at a maximum pressure of ca. 290 bar.
• the pressure change from initial to final pressure is achieved by the compressor 2 in three successive compression stages, among which the total pressure difference is appropriately divided.
• the cylinder casing 3 is comprised of as many cylinders 4 as the compression steps or stages, each cylinder 4 storing compressed gas substantially at the maximum pressure achieved in each of the stages into which the total pressure difference has been subdivided.
• the plant 1 also includes means to feed the compressor 2, before the execution of each of said consecutive stages, with gas from the cylinder 4 that has been filled last. This is shown in greater detail in figures 3a, 3b and 3c, where the functional diagrams of the three phases of compression and storage are illustrated.
• the gas from the feed line 14 is compressed from the initial pipeline pressure [ca. 20 bar] to a low pressure LP of ca. 49 bar.
• the gas is compressed to the medium pressure MP of ca.
• Compression of the natural gas in the compressor 2 is achieved by sucking gas from the low-pressure LP cylinder 4, keeping open valve 12 and a valve 17 placed on a tract 20 of the conduit that connects the LP cylinder 4 to the suction conduit 9 of the compressor 2.
• the compression is achieved by sucking gas from the medium-pressure MP cylinder
• valves 17 and 18 open.
• a valve 22 placed on a tract 23 of the conduit that connects the medium-pressure MP cylinder 4 to the suction conduit 9 of the compressor 2 via tract 20 and an inlet valve 24 to the high-pressure HP cylinder 4 positioned on a third branching 25 of the feed conduit 10 are also open.
• the filling of a vehicle's storage cylinder is represented in figure 4. Operations begin with filling the vehicle' s storage cylinder with gas at a pressure slightly greater than the pressure found inside it, by keeping open an interception valve 26 of a dispensing hose 28 and an outlet valve 27 of the low-pressure LP cylinder 4. Once the low pressure has been achieved, the cylinder of the vehicle is filled from the medium-pressure MP cylinder 4, with valve 26 and an outlet valve 29 of the medium- pressure MP cylinder 4 being open.
• the plant 1 comprises cooling means 5 of the gas stored in the cylinders 4.
• the system can be embodied in a conventional cooling system with a compressor 31, whose function can be performed by the same compressor 2 compressing the natural gas.
• the cooling system can be provided with motors to power the compressor 31. These can be either separate or be the same as the motor 6 powering the natural gas compressor 2.
• the motors can be indifferently electrical or thermal.
• cooling can be provided by a high-thermal capacity fluid spraying system associated with the cylinders 4 in the cylinder casing 3.
• the cylinder s, stacked on racks can be sprinkled from above with a refrigerated water and ethyl alcohol solution by a system of nozzles; the solution, collected in a tub, can then be sucked by a pump that returns it to the cooling system to be cooled again.
• the system requires a casing for the racks and the tub.
• An alternative embodiment is one where cooling is provided by a tub containing a high-thermal capacity fluid in which the cylinders 4 are immersed.
• the cylinders 4, however packaged shall be placed into large, water-tight steel vessels filled with a water and ethyl alcohol solution from the cooling system: as in the case mentioned above, the fluid is returned to the fridge to be cooled again.
• filtered well water circulated periodically can be used as an alternative to the cooling system.
• the plant 1 is fitted with sensor means 8, operatively associated with compressor 2 and with the cylinders 4.
• said sensor means 8 switch off gas inlet into the compressor 2, by activating its connection to the downstream cylinder 4 and switch on the suction of the compressor 2 by activating its connection to the upstream cylinder 4 filled in the previous compression stage.
• the pressure of the individual stages is defined by customer habits.
• the minimum pressure in the storage cylinder of a vehicle at a filling station is about 30 bar. This dictates the low-pressure value, which will reasonably exceed 30 bar; a value of about 50 bar is considered suitable.
• the medium pressure is approx. 120 bar. Since a single compressor is used, a proper 49- 120-294 progression is achieved by a constant compression ratio, equal to 2.45, starting from a pipeline pressure of 20 bar. For higher pipeline pressures a suitable compression ratio is calculated and the pressure progression is adjusted. For lower pipeline pressures, a pressure adjustment stage shall be required to reach 20 bar, with a storage and a cooling stage.
• FIG. 5 A basic drawing of such a plant is reported in figure 5; it envisages a pipeline pressure of 4 bar, common in Italy and requires an additional compressor with a compression ratio of 5.
• One additional advantage is that a single compressor 2 and a single compression stage subserve the storage of gas at intermediate pressures by acting only on the pressure difference between stages and only on a limited amount of gas, Le. the amount of gas delivered to the cylinder casing 3.
• the overall lower compression ratio required of the compressor 2 enables use of small compressors 2, with lower plant and operating costs.
• the continuous operation design of the compressor 2 entails the additional advantage of greater plant 1 reliability .
• a further advantage is that the cylinders 4 can also serve as coolers.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Filling Or Discharging Of Gas Storage Vessels (AREA)
• Processing Of Solid Wastes (AREA)
• Compressor (AREA)
• Preparation Of Compounds By Using Micro-Organisms (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Applications Claiming Priority (2)

Publications (2)

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• 2007
  • 2007-12-04 IT IT000063A patent/ITAN20070063A1/it unknown
• 2008
  • 2008-12-01 WO PCT/IT2008/000736 patent/WO2009072160A2/fr not_active Ceased
  • 2008-12-01 EP EP08857951A patent/EP2232076B1/fr not_active Not-in-force
  • 2008-12-01 BR BRPI0820001-7A patent/BRPI0820001A2/pt not_active IP Right Cessation
  • 2008-12-01 AT AT08857951T patent/ATE513994T1/de not_active IP Right Cessation
  • 2008-12-01 CN CN2008801193269A patent/CN101889142A/zh active Pending
  • 2008-12-01 ES ES08857951T patent/ES2368107T3/es active Active

Non-Patent Citations (1)

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