NITROGEN VAPORIZATION

Abstract

Apparatus and methods for vaporizing liquid nitrogen at sufficient pressure, temperature, and volume to enable a single mobile pumper to meet the needs of many industrial applications. The dual-mode nitrogen pumper of the present invention utilizes a reciprocating pump and heat from the engine coolant and exhaust stream of an internal combustion engine, as well as heat from hydraulic fluid used to load the engine, and transfers that heat to liquid nitrogen pumped through a first heat exchanger and a second, internally-fired heat exchanger is provided to transfer heat to liquid nitrogen pumped through a second heat exchanger. The temperature of the hydraulic fluid is maintained, and the temperature, pressure, and flow rate of the vaporized nitrogen is controlled, by balancing the engine load against the nitrogen pumping rate.

Claims

1. A liquid nitrogen vaporizing system including an internal combustion engine with circulating engine coolant fluid that absorbs heat produced by operation of the engine and produces hot exhaust gases while the engine is artificially loaded by driving a hydraulic pump that forces the hydraulic fluid through the restricted orifice of a sequential valve, thus heating the hydraulic fluid, comprising: a source of liquid nitrogen; a reciprocating pump having an input connected to said liquid nitrogen source and an output; a first heat exchanger for receiving liquid nitrogen from the output of said reciprocating pump and outputting vaporized nitrogen, the heat for said first heat exchanger being stripped from the heated coolant of the operating internal combustion engine, the heated hydraulic fluid pumped by operation of the internal combustion engine, and the engine exhaust gas; a second heat exchanger for receiving liquid nitrogen from the output of said reciprocating pump and outputting vaporized nitrogen, the heat for said second heat exchanger being obtained by combustion of fuel within a fired burner; and a valve for mixing liquid nitrogen with vaporized nitrogen output from either or both of said first or said second heat exchangers.

2. The nitrogen vaporizing system of claim 1 additionally comprising a programmable logic controller for monitoring and varying the fuel consumed by the fired burner of said second heat exchanger for the purpose of maintaining either an operator-selected output temperature of vaporized nitrogen, an operator-selected output flow of vaporized nitrogen, or an operator-selected temperature and flow of vaporized nitrogen, said programmable logic controller being operatively connected to a valve for increasing or decreasing the fuel consumption of the fired burner.

3. The nitrogen vaporizing system of claim 2 wherein said programmable logic controller is programmed with a fuel consumption map.

4. The nitrogen vaporizing system of claim 1 additionally comprising sensors and controls for maintaining the temperature of the hydraulic fluid pumped by the internal combustion engine within an optimal temperature range.

5. The nitrogen vaporizing system of claim 1 additionally comprising sensors and controls for maintaining the discharge temperature of the vaporized nitrogen by either the fired, the unfired, or both the fired and unfired vaporizers at a selected temperature by changing one or more of the volume of nitrogen liquid, nitrogen vapor, or cold nitrogen gas mixed with the vaporized nitrogen.

6. A method of vaporizing liquid nitrogen with a nitrogen vaporizer comprising a heat recovery vaporizer and a direct fired vaporizer powered by an internal combustion engine comprising the steps of: splitting the horsepower output from the internal combustion engine between a mechanical drive for pumping nitrogen to the vaporizers and a hydraulic circuit for providing waste heat from the internal combustion engine to the heat recovery vaporizer; and balancing the load imposed on the internal combustion engine by the hydraulic circuit with the load imposed on the engine by the nitrogen pump by monitoring pumped nitrogen pressure data and either opening or closing a sequential valve located in the hydraulic circuit in response to changes in pressure.

7. The method of claim 6 wherein hydraulic fluid temperature is changed by opening or closing the sequential valve, thereby increasing or decreasing heat to the unfired vaporizer, and wherein shaft rotation of the mechanical drive of the nitrogen pump is monitored as to increases or decreases in the volume of nitrogen pumped.

8. The method of claim 6 additionally comprising a programmable logic controller (PLC) operably connected to the direct fired vaporizer for changing fuel consumption in response to a pre-programmed fuel consumption map stored in the memory of the PLC.

9. A method of maintaining the temperature of the hydraulic fluid within the hydraulic circuit of a heat recovery vaporizer for vaporizing a cryogenic liquid including an internal combustion engine for powering a hydraulic circuit, the engine being loaded by a sequential valve located in the hydraulic circuit and the cryogenic liquid being pumped through the heat recovery vaporizer comprising the steps of selecting an optimal temperature range at which the hydraulic fluid is to be maintained, monitoring hydraulic fluid temperature, and pumping cryogenic liquid through the heat recovery vaporizer at a rate that strips only so much heat from the hydraulic fluid, or enough heat from the hydraulic fluid, as to maintain the temperature of the hydraulic fluid at an optimal temperature range.

10. The method of claim 9 additionally comprising the step of changing engine load to increase or decrease the amount of heat available to the heat recovery vaporizer.

11. The method of claim 9 wherein hydraulic fluid temperature is maintained at an optimal temperature range selected for maximizing the service life of the components of the hydraulic circuit.

12. The method of claim 9 additionally comprising the step of reducing the fuel consumption and combustion gas emissions of the fired vaporizer by vaporizing a portion of the pumped cryogenic liquid with the unfired vaporizer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a schematic, or layout, diagram of a system incorporating a nitrogen vaporizer constructed in accordance with the teachings of the present invention.

[0014] FIG. 2 is also a schematic, or layout, diagram and shows one embodiment of instrumentation and controls for operating the nitrogen vaporizing system of FIG. 1.

[0015] FIG. 3 is a diagram showing a programmable logic controller (PLC) and the inputs and outputs to the PLC for operating the controls and instrumentation of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0016] Referring to FIG. 1, liquid nitrogen is provided to a storage tank 10 by one or more cryogenic transport trucks (not shown) or other sources that may be filled through a loading manifold (not shown), all in accordance with known liquid nitrogen storage and handling systems. Liquid nitrogen is output from storage tank 10 through supply line 16 to the nitrogen vaporizer of the present invention, indicated generally at reference numeral 18, that is itself powered by an internal combustion engine 19 that may be diesel powered or powered by other hydrocarbon fuels such as gasoline or natural gas. The internal combustion engine 19 of nitrogen vaporizer 18 is “artificially” loaded by driving a hydraulic pump 20 that pumps hydraulic fluid through the restricted orifice 22 (see FIG. 3) of a sequencing valve, the engine 19 producing more heat that is “captured” in the engine coolant as engine 19 works harder and burns more fuel to push hydraulic fluid through valve orifice 22. In the embodiment described herein, the internal combustion engine 19 of nitrogen vaporizer 18 provides three heat sources, the hydraulic fluid, the engine exhaust, and the high temperature engine coolant, and all three heat sources are used to advantage in the method and apparatus described below.

[0017] As set out below in connection with the description of FIG. 2, the engine 19 of nitrogen vaporizer 18 also powers a hydraulically-driven booster pump 24 provided for the purpose of feeding liquid nitrogen through line 26 to the suction side of a reciprocating pump 28, which may be a simplex, duplex, triplex, or other multiple-cylinder pump. Those skilled in the art who have the benefit of this disclosure will recognize that the booster pump 24 is not always utilized, and may not even be needed, in installations in which the nitrogen source, such as storage tank 10 or transport trucks, provides liquid nitrogen at sufficient pressure to the suction side of reciprocating pump 28. For instance, some cryogenic tanks provide liquid nitrogen at sufficient pressure that a booster pump is not needed and some cryogenic tanks are provided with internal pumps that provide liquid nitrogen at the pressure needed at the suction side of reciprocating pump 28. A pressure indicator controller PIC-103 is provided in the line 26 and pressure is monitored at pressure transducer PT-105 for controlling boost pump 24 in a manner known in the art. In a preferred embodiment, the output from boost pump 24 is maintained at sufficient pressure by outputting sufficient flow from boost pump 24 to ensure the suction side of pump 28 is always fed with sufficient nitrogen (see below). If nitrogen is provided to the suction side of pump 28 in a volume exceeding the net positive suction pressure (NPSP) of pump 28, excess nitrogen is returned to tank 10 through line 29.

[0018] Reciprocating pump 28 builds sufficient pressure in the input line 30 to the unfired and direct-fired heat exchangers 32, 52 to overcome the 200-1000 psi pressure drop characteristic of passage through a heat exchanger with the result that the nitrogen output through line 34 to the nitrogen tank 36 or other equipment can be in the 500-10,000 psi range, more particularly, 500-5000 psi, to overcome further pressure drop or resistance downstream depending upon the needs of the particular installation or application. The pressure in input line 30 is monitored by pressure transducer PT-103 and, in the particular embodiment shown, displayed at pressure indicator PI-103. As discussed briefly above, the tank/other equipment indicated generally at reference numeral 36 is an industrial plant, electric power plant, temporary pipeline, a well head for applications in which the vaporized nitrogen is utilized at volumes and pressures sufficient for well servicing and/or oilfield operations, or any of the many other applications and/or installations in which nitrogen is used to advantage. As also shown in FIG. 1, output line 34 is provided with a valve 37 and line 39 for routing the nitrogen through liquid line 39A and hot gas line 39B with valves V-102 and V-105 for mixing the nitrogen exiting line 41 to a selected discharge temperature ranging from a nominal—320 F to temperatures of about 500 F or more directly to the industrial plant or any of the many other applications and/or installations in which large volumes of pressurized nitrogen at a selected temperature are used to advantage.

[0019] As noted above, the internal combustion engine 19 of LNG vaporizer 18 outputs three heat sources, and first heat exchanger 32 receives inputs from the engine coolant at temperatures typically ranging between about 120-160 degrees F. and the hydraulic fluid used to load engine 19 at temperatures typically ranging between about 120-160 degrees F. (see below for further discussion of the hydraulic fluid temperature). The third heat source, namely the engine exhaust, enters heat exchanger 32 at temperatures ranging between about 300 degrees F. up to temperatures as high as 1000 degrees F. The heat exchanger 32 that strips heat from hydraulic fluid, engine coolant, and exhaust together comprise the unfired nitrogen vaporizer of the present invention and additional details of the construction and operation are described in more detail in co-pending application Ser. No. 14/085,783, filed Nov. 20, 2013, the entirety of which is hereby incorporated into the present application by this specific reference.

[0020] The temperature of the fluid in the hydraulic circuit including sequencing valve 22 is monitored at temperature indicator controller TIC-102 comprising a portion of the unfired vaporizer and utilized as an input to a programmable logic controller (PLC) 100 (see below) for operating the actuator of V-104 of the sequencing valve 22 in the hydraulic circuit, the valve 22 responding to changes in temperature at TIC-102 to maintain a set temperature range, selected by an operator at PLC 100, in the hydraulic fluid, within the range specified by the manufacturer of the hydraulic fluid for maximizing the life and performance of the hydraulic fluid, and hence the components of the hydraulic circuit. As set out above, as sequencing valve 22 is opened and/or closed, the internal combustion engine 19 works harder against the hydraulic pressure to build heat in the hydraulic circuit and/or backs off to dissipate heat.

[0021] No matter how well the nitrogen storage tank 10 is insulated, some vapor is lost from tank 10 which may be vented to the atmosphere. Alternatively, the present invention may be provided with means to collect the vapor from storage tank 10 (and/or the transport trucks or other storage equipment) and direct that collected vapor back to tank 10, thus preventing the vapor/gas from being vented to the atmosphere and preserving the nitrogen for meaningful use. Appropriate controls and valves are provided for this purpose as known in the art, including a tank level pressure transducer PT-107, level indicator controller LIC-101, pressure transducer PT-106, and pressure indicator controller PIC-106.

[0022] A second heat exchanger is also shown in FIG. 1. Second heat exchanger 52 is a direct-fired heat exchanger (rather than the non-fired, or heat recovery, exchanger 32) and, like non-fired heat exchanger 32, receives liquid nitrogen output from pump 28 such that first and second heat exchangers 32 and 52 are connected into the nitrogen flow in parallel. Output from heat exchanger 52 passes through TIC-101 and out through line 34 and valve 37, valves V-102 and V-105 being closed. The hot gas in line 34 is mixed with liquid nitrogen in tempering line 40 using modulating valve V-130 under control of PIC-101 to obtain vaporized nitrogen at the temperature selected by the operator.

[0023] Referring now to FIGS. 2 and 3, the RPM of reciprocating pump 28 is monitored by flow indicator controller FIC-101, providing PLC 100 with the nitrogen flow rate into line 30. To obtain a selected flow rate, the speed of engine 19 and transmission gear selection is controlled to give the shaft RPM at pump 28 that provides the required flow rate into line 30 under control of PLC 100. Those skilled in the art will recognize that the speed of engine 19 and the particular gear in which the transmission 42 is operated can also be controlled manually and also that some control of flow rate into line 30 can also be obtained by varying engine speed or the particular gear of transmission 42. The outputs from PLC 100 are shown at engine control module ECM and transmission control module TCM on FIG. 3.

[0024] A shown in FIG. 2, when the improved dual mode pumper of the present invention is in pumping mode, the power from engine 19 is diverted through the gearbox 21 with two output pads (the output pads, being a part of gearbox 21, are not separately designated in the figures). One of the output pads is utilized for driving a hydraulic pump for changing the orifice of sequential valve 22 for loading the engine 19 to burn fuel and produce heat. The second pad is equipped with a driveshaft 23 for driving reciprocating pump 28. As noted above, this configuration of the engine 19, transmission 42, and gearbox 21 enables engine horsepower to be distributed through the transmission 42 to gearbox 21 so that a portion of the horsepower drives driveshaft 23 and the balance of the horsepower drives the hydraulic package, thereby maximizing utilization of engine horsepower for loading engine 19 for use in non-fired vaporization. As also shown in FIG. 2, a separate power take-off PTO is provided as a power source for a second hydraulic circuit powering the fired vaporizer fuel pump, nitrogen booster pump, auxiliary coolant pump, vaporizer cooling fan 60 (see below), the hydraulic and lube oil cooling fans, the flameless vaporizer coolant pump, and the lubricating system for reciprocation pump 28, all of which are known in the art and therefore not shown in the figures.

[0025] Referring now to FIG. 3, a programmable logic controller (PLC) is indicated generally at reference numeral 100. The operator selects, or activates, a particular control module at PLC 100, for instance, the pressure of the nitrogen output through line 34. Appropriate prompts are utilized by the operator to select the required flow rate, then the control module for selecting the temperature of the nitrogen output is activated and temperature selected, and so on, all in accordance with methods known in the art. As shown in FIG. 3, inputs from the various pressure, flow, temperature, and other indicators summarized above are likewise monitored at PLC 100 and adjustments made in engine speed, nitrogen flow rate, and so on in accordance with pre-programmed operating rules for maintaining operator selected pressure, flow, and temperature. More specifically, to increase nitrogen output, nitrogen temperature, or both flow and temperature when operated in dual mode, PLC 100 is programmed with a fuel consumption map that enables PLC 100 to call for opening (or closing) of fuel control valve V-145 to increase (or decrease) engine speed taking the heat available from the unfired vaporizer into consideration. The speed of the hydraulically-powered vaporizer fan 60 is also controlled from PLC 100 through flow control valve FCV-1. Those skilled in the art will recognize that with the operating flexibility and the level of control provided by PLC 100, the improved dual mode pumper of the present invention is capable of being operated at speeds and at the 120-140 degree F. temperatures that maintain the optimal viscosity of the hydraulic fluid and therefore the longevity of the component parts of the pumper.

[0026] The improved dual-mode (fired and un-fired) nitrogen pumper of the present invention offers certain advantages and efficiencies that, on information and belief, cannot be accomplished with previous nitrogen pumpers. For instance, it will be noted that direct-fired and heat recovery vaporizers can be bypassed to discharge liquid nitrogen as required for some applications. Further, the improved dual mode pumper of the present invention is capable of working pressures up to 10,000 psi and can deliver vaporized nitrogen at temperatures ranging from nominal temperature of about—320 F up to about 500 F. Vaporizer selection is made by an operator depending on desired flow rate and temperature of the application. In flameless mode, the pumper of the present invention is capable of delivering vaporized nitrogen at rates up to 4200 scfm at 70 F (and even higher flow rates depending upon the horsepower available from internal combustion engine 19). In direct fired mode, the pumper is capable of vaporized nitrogen flow rates over 12,000 scfm at 70+ F and up to 500 F at lower flow rates. For purposes of comparison, and referring again to U.S. Pat. No. 8,943,842, the hybrid-pumper described in that prior patent is described as consuming an estimated 29 gal/hr of fuel to produce an estimated 216,000 scfh, but that hybrid-pumper can only achieve that output by operating in direct-fired mode. The dual-mode pumper of the present invention consumes an estimated 27 gal/hr to produce that same estimated output, but the dual-mode pumper of the present invention produces that same estimated output without using the direct-fired vaporizer, thereby enabling operation in flameless environments and/or in environments in which emissions must be limited. Further, the output pressure required has minimal effect on the fuel consumption of the improved dual mode pumper of the present invention because the dual mode pumper of the present invention is capable of such gas output pressure in unfired mode. To further illustrate a further advantage of the dual-mode pumper of the present invention, at an estimated 540,000 scfh at 65-70 F, the dual-mode pumper of the present invention burns an estimated one gallon of fuel per minute as compared to typical consumption rates approximately 1.5 to 2 greater than one gal/min as a result of the efficient use of the non-fired vaporizer 32.

[0027] Those skilled in the art who have the benefit of this disclosure will also recognize that changes can be made to the component parts of the present invention without changing the manner in which those component parts function and/or interact to achieve their intended result. All such changes, and others that will be clear to those skilled in the art from this description of the preferred embodiment(s) of the invention, are intended to fall within the scope of the following, non-limiting claims.