Abstract:
A pressure reducing system for fuel gas and a natural gas dewaxing vehicle are provided. The pressure reducing system includes fuel gas pipelines which consist of successively connected a high pressure pipeline, a medium pressure pipeline and a low pressure pipeline in the flow direction of fuel gas. The tail end of the low pressure pipeline connects with a combustion apparatus. A high pressure relief valve, a high pressure air feed valve, a heat exchanger and a primary pressure reducing valve subassembly are connected on the high pressure pipeline. The heat exchanger is provided with a hot fluid inlet and a hot fluid outlet, where the hot fluid inlet connects with a hot water apparatus, and the hot fluid outlet connects with a water storage apparatus. The medium pressure pipeline is equipped with a medium pressure relief valve and a secondary pressure reducing valve.

Description:
The present application is the national phase of International Application No. PCT/CN2010/075903, titled “PRESSURE REDUCING SYSTEM FOR FUEL GAS AND NATURAL GAS DEWAXING VEHICLE”, filed on Aug. 11, 2010, which claims the benefit of priority to Chinese patent application No. 200910065745.5 titled “PRESSURE REDUCING SYSTEM FOR FUEL GAS AND NATURAL GAS DEWAXING VEHICLE”, filed with the Chinese State Intellectual Property Office on Aug. 12, 2009. The entire disclosure thereof is incorporated herein by reference. 
     TECHNICAL FIELD OF THE INVENTION 
     The present disclosure relates to a fuel gas pressure reducing system and a natural gas dewaxing vehicle employing the fuel gas pressure reducing system. 
     BACKGROUND OF THE INVENTION 
     The existing dewaxing vehicles in the market use the light diesel as fuel, which is relatively expensive and thus causes a relatively high use cost of the dewaxing vehicle. A Chinese patent application publication No. CN2596004 discloses a well-washing and dewaxing vehicle which can use the compressed natural gas as fuel to reduce the use cost of the dewaxing vehicle. However, when using the compressed natural gas, the compressed natural gas, due to relatively high pressure thereof, cannot directly satisfy the using requirements of the dewaxing vehicle, and thus the application of the dewaxing vehicle is limited. If using uncompressed natural gas, it is undoubted that the use cost of the dewaxing vehicle will be increased and thus the dewaxing vehicle is not applicable in practice. 
     SUMMARY OF THE INVENTION 
     The object of the present application is to provide a fuel gas pressure reducing system for reducing the pressure of the high pressure natural gas such that the pressure of the high pressure natural gas may meet the combustion condition. 
     For realizing the above objection, the fuel gas pressure reducing system provided by the present application includes a fuel gas pipeline, wherein along a flow direction of the fuel gas, the fuel gas pipeline includes a high pressure pipeline, a medium pressure pipeline and a low pressure pipeline which are successively connected. A tail end of the low pressure pipeline is connected to a combustion device, and a beginning end of the high pressure pipeline is connected to a gas storage device. The high pressure pipeline is provided therein with a high pressure relief valve, a high pressure gas supply valve, a heat exchanger and a first stage pressure reducing valve assembly. A hot fluid inlet of the heat exchanger is connected to a hot water device, and a hot fluid outlet of the heat exchanger is connected to a water storage device. The medium pressure pipeline is provided therein with a medium pressure relief valve and a second stage pressure reducing valve. The low pressure pipeline is provided therein with a low pressure relief valve and a third stage pressure reducing valve. 
     Due to the three-stage pressure reducing configuration, the fuel gas pressure reducing system provided by the present application may use the compressed natural gas as fuel safely, and may output the natural gas whose pressure meets the combustion requirements; at the same time, the fuel gas pressure reducing system provided by the present application does not need a large size gas storage device and may use the compressed natural gas without increasing the size of the vehicle, which reduces the use cost and the modification cost of the natural gas dewaxing vehicle. The heat exchanger provided in the high pressure pipeline may heat the fuel gas before reducing the pressure of the fuel gas, which ensures that the fuel gas pressure reducing system may output the natural gas whose temperature meets the predetermined requirements. In additional, the fuel gas pressure reducing system provided by the present application has a simple and compact structure and is easy to use, is highly applicable for using in the dewaxing vehicle. 
     As an improvement of the present application, a tail section of the low pressure pipeline is further connected to a combined solenoid valve assembly in series, and the combined solenoid valve assembly includes an overpressure cut-off solenoid valve and a flow regulating solenoid valve connected in series. Since the combined solenoid valve assembly includes the overpressure cut-off solenoid valve and the flow regulating solenoid valve connected in series, when the output pressure fluctuates and is greater than a predetermined safe pressure value, the overpressure cut-off solenoid valve will automatically cut off the pipeline to stop outputting the natural gas so as to avoid accidents. The flow regulating solenoid valve may adjust an output quantity of the natural gas in a unit time as required so as to satisfy the normal operating requirements of the combustion device under different conditions. 
     As a further improvement of the present application, the first stage pressure reducing valve assembly is provided with two pressure reducing valves connected in parallel, and it is provided in series a cut-off valve upstream and downstream of each of the pressure reducing valves, respectively. 
     It is provided in series a cut-off valve in the pipeline upstream and downstream of each of the pressure reducing valves respectively, such that gas paths passing through corresponding pressure reducing valve may be cut off by the cut-off valves so as to facilitating the routine adjustment and maintenance of the corresponding pressure reducing valve. Two pressure reducing valves are connected in parallel such that when one of the pressure reducing valves is adjusted, the other one of the pressure reducing valves may continue working. 
     As a further improvement of the present application, along the flow direction of the fuel gas, the medium pressure pipeline upstream of the medium pressure relief valve is provided therein with a blow-off valve. 
     The blow-off valve is provided to facilitate the discharging of the routine residual fuel gas in the fuel gas pipeline after the pressure reducing. 
     As a further improvement of the present application, along the flow direction of the fuel gas, the high pressure pipeline downstream of the high pressure relief valve is provided with a tee joint, and three gas ports of the tee joint are respectively connected to the gas storage device, the high pressure gas supply valve and a gas charging valve. A cut-off valve is connected between the gas charging valve and the tee joint in series. The high pressure pipeline between the tee joint and the high pressure gas supply valve is provided therein with a high pressure manometer. The high pressure pipeline between the high pressure gas supply valve and the heat exchanger is provided therein with a high pressure shut-off valve and a filter connected in series. The medium pressure pipeline between the medium pressure relief valve and the second stage pressure reducing valve is provided therein with a medium pressure manometer. The low pressure pipeline upstream of the low pressure relief valve is provided therein with a low pressure manometer. The low pressure pipeline between the low pressure relief valve and the third stage pressure reducing valve is provided therein with a low pressure gas supply valve and a flowmeter in series. 
     The tee joint is provided to facilitate the connection between the high pressure pipeline and the external gas storage device and the charging of the gas into the gas storage device via the gas charging valve. The cut-off valve may prevent the airflow from flowing back through the gas charging valve when the fuel gas pressure reducing system is in normal operation. The high pressure manometer, the medium pressure manometer and the low pressure manometer are provided to facilitate the monitoring of the pressure values of pipeline sections by the operator in operation. The filter may filter out impurities in the natural gas to ensure that the natural gas entering into the heat exchanger and supplied to the combustion device is purer and cleaner. The monometer is provided to facilitate the monitoring of the natural gas output quantity from the fuel gas pressure reducing system by the operator. 
     Another object of the present application is to provide a natural gas dewaxing vehicle employing the above fuel gas pressure reducing system. The natural gas dewaxing vehicle includes a vehicle chassis provided thereon with a bedplate on which a water supply system, a power mechanism, a combustion mechanism, a gas storage device and a fuel gas pressure reducing system connected to the gas storage device are provided. Along the flow direction of water, the water supply system includes a water tank, a water pump, a hot water device and a heat exchanger, which are successively connected via a water pipeline system, and discharged water of the heat exchanger flows back into the water tank. The combustion mechanism includes an air blower connected to a natural gas combustion device via an air outlet pipe, the natural gas combustion device is provided to heat the hot water device. The power mechanism includes a power device, and the power device is connected to the air blower and the water pump and provides power to the air blower and the water pump. Along the flow direction of natural gas, a gas supply system includes the gas storage device and the fuel gas pressure reducing system, and the fuel gas pressure reducing system includes a fuel gas pipeline. Along the flow direction of the fuel gas, the fuel gas pipeline includes a high pressure pipeline, a medium pressure pipeline and a low pressure pipeline which are successively connected. A tail end of the low pressure pipeline is connected to the natural gas combustion device, and a beginning end of the high pressure pipeline is connected to the gas storage device. The high pressure pipeline is provided therein with a high pressure relief valve, a high pressure gas supply valve, a heat exchanger and a first stage pressure reducing valve assembly. A hot fluid inlet of the heat exchanger is connected to the hot water device, and a hot fluid outlet of the heat exchanger is connected to the water tank. The medium pressure pipeline is provided therein with a medium pressure relief valve and a second stage pressure reducing valve, the low pressure pipeline is provided therein with a low pressure relief valve and a third stage pressure reducing valve. 
     The natural gas dewaxing vehicle provided by the present application may use the natural gas as fuel, which reduces the use cost. By employing the above fuel gas pressure reducing system, size of the vehicle will not be increased while ensuring the normal use of the natural gas, which reduces the cost and is suitable for modifying the existing vehicle. 
     As an improvement of the present application, a tail section of the low pressure pipeline is further connected to a combined solenoid valve assembly in series, the combined solenoid valve assembly includes an overpressure cut-off solenoid valve and a flow regulating solenoid valve connected in series. The first stage pressure reducing valve assembly includes two pressure reducing valves connected in parallel, and it is provided in series a cut-off valve upstream and downstream of each of the pressure reducing valves respectively. Along the flow direction of the fuel gas, the medium pressure pipeline upstream of the medium pressure relief valve is provided therein with a blow-off valve. The power device is an on-bedplate engine. The natural gas dewaxing vehicle further includes a control system provided on the bedplate, and the control system is connected to the natural gas combustion device, the water pump and the hot water device respectively. The blow-off valve is provided to facilitate the discharging of the routine residual fuel gas in the fuel gas pipeline after the pressure reducing. 
     The first stage pressure reducing valve assembly includes two pressure reducing valves connected in parallel, and it is provided a cut-off valve in series in the pipelines upstream and downstream of each of the pressure reducing valves, such that when one of the pressure reducing valves is adjusted, the other one of the pressure reducing valves may continue working. 
     As a further improvement of the present application, along the flow direction of the fuel gas, the high pressure pipeline downstream of the high pressure relief valve is further provided therein with a tee joint, and three gas ports of the tee joint are respectively connected to the gas storage device, the high pressure gas supply valve and a gas charging valve. A cut-off valve is connected between the gas charging valve and the tee joint in series. The high pressure pipeline between the tee joint and the high pressure gas supply valve is provided therein with a high pressure manometer. The high pressure pipeline between the high pressure gas supply valve and the heat exchanger is provided therein with a high pressure shut-off valve and a filter in series. The medium pressure pipeline between the medium pressure relief valve and the second stage pressure reducing valve is provided therein with a medium pressure manometer. The low pressure pipeline upstream of the low pressure relief valve is provided therein with a low pressure manometer. The low pressure pipeline between the low pressure relief valve and the third stage pressure reducing valve is provided therein with a low pressure gas supply valve and a flowmeter connected in series. The arrangement of the above devices is reasonable and compact thus the present application is suitable for using onboard. 
     As a further improvement of the present application, the hot water device is a heating furnace or a heater, the air blower is a centrifugal air blower, the gas storage device is a natural gas steel cylinder group. The natural gas steel cylinder group includes more than three natural gas steel cylinders which are connected via pipelines, a part of the natural gas steel cylinder group is provided on a top portion of the water tank, the other part of the natural gas steel cylinder group is provided on the bedplate behind the water tank. 
     The gas storage device is the natural gas steel cylinder group, the number of the natural gas steel cylinders may be increased or decreased according to different using needs, such that the natural gas dewaxing vehicle provided by the present application may applicable to various occasions having different gas consumptions. 
     As a further improvement of the present application, a carriage is provided in a region from a front end of the bedplate to a front portion of the water tank, a bottom portion of a front end of the carriage is fixedly connected to the bedplate, a bottom portion of a rear end of the carriage is fixedly connected to the top portion of the water tank. The carriage is provided to protect the devices, such as the on-bedplate engine, placed inside the carriage. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic view of the structure of a fuel gas pressure reducing system provided by the present application; 
         FIG. 2  is a schematic view of the structure of a natural gas dewaxing vehicle provided by the present application; and 
         FIG. 3  is a top view of the natural gas dewaxing vehicle in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIG. 1 , the fuel gas pressure reducing system provided by the present application includes a fuel gas pipeline having a predetermined length. Along a flow direction of fuel gas from a beginning end to a tail end, the fuel gas pipeline includes a high pressure pipeline  41 , a medium pressure pipeline  42  and a low pressure pipeline  43 . In use, a beginning end of the high pressure pipeline  41  is connected to an external gas storage device  9 , and a tail end of the low pressure pipeline  43  is connected to an external combustion device  7 . 
     Along the flow direction of fuel gas, the high pressure pipeline  41  is successively provided therein with a high pressure gas supply valve  21 , a high pressure shut-off valve  22 , a filter  23 , a heat exchanger  24  and a first stage pressure reducing valve assembly, which are connected in series. A high pressure relief valve  17 , a tee joint  44  and a high pressure manometer  20  are successively provided between the gas storage device  9  and the high pressure gas supply valve  21 . Three gas ports of the tee joint  44  are respectively connected to the gas storage device  9 , the high pressure gas supply valve  21  and a gas charging valve  19 . A cut-off valve  46  is connected in series between the gas charging valve  19  and the tee joint  44 . The gas charging valve  19  is provided to facilitate the charging of the natural gas into the gas storage device  9  via a gas charging station or via other ways when the fuel gas in the gas storage device  9  is consumed. 
     The first stage pressure reducing valve assembly includes two pressure reducing valves  25 A and  25 B provided in parallel. Cut-off valves  25 C and  25 D are respectively connected in series upstream and downstream of the pressure reducing valve  25 A, and cut-off valves  25 E and  25 F are respectively connected in series upstream and downstream of the pressure reducing valve  25 B. A hot fluid inlet  24 A of the heat exchanger  24  is connected to an external hot water device, and a hot fluid outlet  24 B of the heat exchanger  24  is connected to an external water storage device. The hot water device may be a heater (the heater may be a heater available from the market or a heater disclosed in the prior art), also may be a heating furnace which may be the heating furnace disclosed in a Chinese patent application No. 02208364.2 or other existing heating furnaces. 
     After passing through the first stage pressure reducing valve assembly, the pressure of the natural gas is reduced greatly, and the temperature of the pressure reduced fuel gas is lowered. The heat exchanger  24  is provided to heat the natural gas before reducing the pressure thereof so as to prevent the pressure reduced fuel gas from having a too low temperature. The cut-off valves  25 C,  25 D,  25 E and  25 F may cut off the gas lines passing through the first stage pressure reducing valve  25 A or  25 B so as to facilitate the routine adjustment or maintenance of the first stage pressure reducing valve assembly. 
     As shown in  FIG. 1 , along the flow direction of the fuel gas, the medium pressure pipeline  42  is provided therein with a blow-off valve  26  and a second stage pressure reducing valve  29  successively. Along the flow direction of the fuel gas, the medium pressure pipeline  42  between the blow-off valve  26  and the second stage pressure reducing valve  29  is provided therein with a medium pressure relief valve  27  and a medium pressure manometer  28  successively. The blow-off valve  26  is provided to facilitate the discharge of the routine residual fuel gas in the fuel gas pipeline after the pressure reducing. 
     As shown in  FIG. 1 , along the flow direction of the fuel gas, the low pressure pipeline  43  is successively provided therein with a low pressure gas supply valve  32 , a flowmeter  33 , a third stage pressure reducing valve  34  and a combined solenoid valve assembly  35  which are connected in series. The combined solenoid valve assembly may include an overpressure cut-off solenoid valve and a flow regulating solenoid valve provided in series. The fuel gas pipeline between the second stage pressure reducing valve  29  and the low pressure gas supply valve  32  is successively provided therein with a low pressure manometer  30  and a low pressure relief valve  31 . 
     The high pressure relief valve  17 , the medium pressure relief valve  27  and the low pressure relief valve  31  respectively provide overpressure protection to the high pressure pipeline  41 , the medium pressure pipeline  42  and the low pressure pipeline  43 . The high pressure manometer  20 , the medium pressure manometer  28  and the low pressure manometer  30  are provided to facilitate monitoring the pressures in the high pressure pipeline  41 , the medium pressure pipeline  42  and the low pressure pipeline  43  by the operator respectively. 
     In use, the fuel gas enters into the fuel gas pipeline from the gas storage device  9 , passes through the high pressure gas supply valve  21 , the high pressure shut-off valve  22  and the filter  23  successively and then enters into the heat exchanger  24  in which the fuel gas absorbs the heat of the hot fluid to reach a certain preheating temperature; and then the fuel gas enters into a proper pressure reducing valve in the first stage pressure reducing valve assembly, the second stage pressure reducing valve  29 , the low pressure gas supply valve  32 , the flowmeter  33 , the third stage pressure reducing valve  34  and the combined solenoid valve assembly  35  successively to reduce its pressure. When meeting the safe combustion condition of the natural gas, the fuel gas is output and supplied to the combustion device  7 . 
     As shown in  FIGS. 2 and 3 , a natural gas dewaxing vehicle provided by the present application includes a vehicle second-class chassis  1  and a bedplate  11  towed by the second-class chassis. A water supply system, a power mechanism, a combustion mechanism, the gas storage device  9  and a fuel gas pressure reducing system  6  connected to the gas storage device  9  are provided on the bedplate  11 . The fuel gas pressure reducing system may be the fuel gas pressure reducing system described above. 
     As shown in  FIGS. 1-3 , along the flow direction of the water, the water supply system includes a water tank  8 , a water pump  14 , a hot water device  12  and the heat exchanger  24  in the above fuel gas pressure reducing system, which are successively connected circularly via a water pipeline system  13 . Discharged water from the heat exchanger  24  flows back into the water tank  8 . 
     As shown in  FIGS. 2 and 3 , the combustion mechanism includes an air blower  3  connected to a natural gas combustion device  7  via an air outlet pipe  50 . The natural gas combustion device  7  is provided to heat the hot water device  12 . 
     As shown in  FIGS. 2 and 3 , the power mechanism includes an on-bedplate engine  2  as the power device. The on-bedplate engine  2  is connected to the air blower  3  via a coupling  16  and provides power to the air blower  3 , and the on-bedplate engine  2  is further connected to the water pump  14  via a driving and transmission case  15  and provides power to the water pump  14 . 
     As shown in  FIGS. 1-3 , along the flow direction of the fuel gas, the gas supply system includes the gas storage device  9  and the fuel gas pressure reducing system  6 . The fuel gas pressure reducing system  6  includes a fuel gas pipeline. Along the flow direction of the fuel gas, the fuel gas pipeline includes the high pressure pipeline  41 , the medium pressure pipeline  42  and the low pressure pipeline  43  which are successively connected. A tail end of the low pressure pipeline  43  is connected to the natural gas combustion device  7 , and a beginning end of the high pressure pipeline  41  is provided with the tee joint  44 . One gas port of the tee joint  44  is connected with the gas charging valve  19 , the other two gas ports of the tee joint  44  are respectively connected to the gas storage device  9  and the high pressure pipeline  41 . A cut-off valve  46  is connected between the gas charging valve  19  and the tee joint  44  in series, and the connecting pipeline between the gas storage device  9  and the tee joint  44  is provided with a high pressure relief valve  17 . 
     As shown in  FIGS. 1-3 , along the flow direction of the fuel gas, the high pressure pipeline  41  is successively provided therein with the high pressure gas supply valve  21 , the high pressure shut-off valve  22 , the filter  23 , the heat exchanger  24  and the first stage pressure reducing valve assembly, which are connected in series. The high pressure pipeline  41  between the tee joint  44  and the high pressure gas supply valve  21  is provided therein with the high pressure manometer  20 . The heat exchanger  24  is provided with the hot fluid inlet  24 A and the hot fluid outlet  24 B. The hot fluid inlet  24 A is connected to the hot water device  12  via a cut-off valve  56 , and the hot fluid outlet  24 B is connected to the water tank  8  via a cut-off valve  55 . The first stage pressure reducing valve assembly includes two pressure reducing valves  25 A and  25 B provided in parallel. Cut-off valves  25 C and  25 D are respectively connected in series upstream and downstream of the pressure reducing valve  25 A, and cut-off valves  25 E and  25 F are respectively connected in series upstream and downstream of the pressure reducing valve  25 B. The hot fluid inlet  24 A and the hot fluid outlet  24 B of the heat exchanger  24  are respectively connected to the water tank  8  and the hot water device  12 . In use, the water may be circulated along the water tank  8 , the hot water device  12 , the heat exchanger  24  and the water tank  8 . 
     As shown in  FIG. 1 , along the flow direction of the fuel gas, the medium pressure pipeline  42  is provided therein with the blow-off valve  26  and the second stage pressure reducing valve  29  successively. The medium pressure pipeline  42  between the blow-off valve  26  and the second stage pressure reducing valve  29  is provided therein with the medium pressure relief valve  27  and the medium pressure manometer  28  successively. 
     As shown in  FIG. 1 , along the flow direction of the fuel gas, the low pressure pipeline  43  is successively provided therein with the low pressure gas supply valve  32 , the flowmeter  33 , the third stage pressure reducing valve  34  and the combined solenoid valve assembly  35  which are connected in series. The fuel gas pipeline between the medium pressure relief valve  27  and the low pressure gas supply valve  32  is provided therein with the low pressure manometer  30  and the low pressure relief valve  31  successively. As shown in  FIGS. 1-3 , an outlet of the combined solenoid valve assembly  35 , acted as the tail end of the low pressure pipeline  43 , is connected to the natural gas combustion device  7 . 
     As shown in  FIGS. 2 and 3 , the natural gas dewaxing vehicle provided by the present application further includes a control system provided on the bedplate  11 . The control system is connected to the natural gas combustion device  7 , the water pump  14  and the hot water device  12 , respectively, so as to realize the control of the operating process thereof. 
     As shown in  FIGS. 2 and 3 , the water tank  8  is provided on the middle-rear portion of the bedplate  11 . The natural gas combustion device  7  and the hot water device  12  are provided on the middle portion of the bedplate  11  and are provided adjacent to the water tank  8 . The power mechanism and the air blower  3  of the combustion mechanism are provided on the front portion of the bedplate  11 . The control system is provided on the bedplate  11  between the power mechanism and the hot water device  12 . 
     As shown in  FIGS. 2 and 3 , a carriage  5  is provided in a region from a front end of the bedplate  11  to a front portion of the water tank  8 . A bottom portion of a front end of the carriage  5  is fixedly connected to the bedplate  11 , and a bottom portion of a rear end of the carriage  5  is fixedly connected to the top portion of the water tank  8 . 
     The hot water device  12  may be a heating furnace, also may be a heater. The air blower  3  may be a centrifugal air blower  3 , also may be other kinds of air blower  3 . As shown in  FIGS. 2 and 3 , in the natural gas dewaxing vehicle provided by the present application, a natural gas steel cylinder group includes twelve natural gas steel cylinders, which are connected via pipelines. A part of the natural gas steel cylinder group is provided on a top portion of the water tank  8 , the other part of the natural gas steel cylinder group is provided on the bedplate  11  behind the water tank  8 . The gas storage device  9  is not limited to be the natural gas steel cylinder group, also may be other natural gas storage devices. 
     In dewaxing operation, the compressed natural gas in the gas storage device  9  enters into the fuel gas pressure reducing system  6  to reduce its pressure. When the pressure reduced natural gas reaches the predetermined combustion condition, the on-bedplate engine  2  is started to drive the water pump  14  to supply operation medium (water) to the hot water device  12 . When the hot water device  12  is filled with the operation medium (water), the control system  4  is started such that the natural gas combustion device  7  heats the operation medium (water) to high temperature vapor or hot water according to a set program, thereby performing dewaxing operation to the wax precipitation in the oil pipe, the oil rod and the oil pipeline.