GB2089022A - Rotary driven fluid pumping and heating system - Google Patents

Abstract

The described system utilizes a heat engine which provides shaft power and heat such as a conventional diesel engine 14 in which part of the shaft power drives a pump 11 for fluid to be heated; for example, a cryogenic liquid. The engine heat is used to heat and/or vaporize the cryogenic liquid in a heat exchanger 10. The heat available from the engine for transfer to the liquid to be vaporized is proportional to the power level of the engine. By providing a loading on the engine which is proportional to the flow rate of the cryogenic liquid, a sufficient amount of heat is provided to effect complete vaporization of the liquid, the amount of heat being directly proportional to the flow rate of the liquid. The loading of the engine can be accomplished by a power absorbing hydraulic drive 22 connected to the engine shaft with the hydraulic medium used to drive the cryogenic liquid pump. A rotary hydraulic drive and multisection rotary driven fluid pump 24 is provided to achieve vibration free, smooth operation in simplified, closed loop hydraulic drive circuit. A dual rotary system is also disclosed. The vaporized can be used to displace fluid in oil wells, to purge pipelines or tanks in ships, or for filling gas storage bottles. <IMAGE>

Description

SPECIFICATION Rotary driven fluid pumping and heating system BACKGROUND OF THE INVENTION This invention relates generally to fluid pumping and heating systems and more particularly to an improved system for pumping and heating and/or vaporizing fluids such as cryogenic liquids which is particularly adapted for employing a rotary driven LN pumping system.

This invention is an improvement of that disclosed in our U.S. Patent No. 41 97712 issued April 15, 1 980. As therein disclosed, the invention is concerned with adding heat to a fluid as it is being pumped from a low pressure to a high pressure by means of a heat engine, such as a diesel engine. The engine uses the combustion of fuel to produce shaft power and heat both of which are used to convert the condition of the fluid from liquid at ambient pressure to a gas at high pressure, deliverable at an adjustable flow rate commensurate with the speed of operation of the engine.

Systems for pumping and heating a fluid to a desired temperature, as for example heating liquid nitrogen from --3200F. to provide gaseous nitrogen at a desired pressure and temperature, for example 5000 psi and 700 F., are well known in the art. The vaporized nitrogen can be used to displace fluid in oil wells, or for the purposes of purging tanks in ships or purging pipelines, or for simply filling nitrogen gas storage bottles.

Heretofore, the known systems usually required burners; direct fired units, boiler systems and the like to effect the heating and/or vaporization. Thus, in addition to an internal combustion engine for driving the cryogenic pump, an additional burner for vaporization is used.

Heat engines are devices which convert combustion energy into shaft power and heat. Heat rejected from a heat engine is commonly called "waste" heat because this heat is used by the engine but is not converted into shaft power. In the present invention this heat is not wasted. It is used to heat the fluid being pumped. The present invention is particularly concerned with those circumstances in which the heat required is less than the heat which rnay be conveniently extracted from the so-called waste heat. Under these conditions, the methods of this invention increase the engine power level so as to increase the amount of heat rejected from the engine so that an adequate amount can be extracted for heating the fluid.

More particularly, the present invention includes pumping the fluid to be heated along a flow path.

An engine which supplies shaft power and heat such as a diesel engine is provided and part of the shaft power is used to effect the pumping. This shaft power is then further loaded so that the engine operates at a greater power level than necessary to effect the pumping to thereby provide increased heat from the engine. Finally, a heat exchange is effected between the engine heat and fluid passing along the flow path to thereby heat the fluid, the amount of heat provided being directly proportional to the flow rate of the fluid. As a consequence, separate burners, direct fired units, boiler systems and the like, are not required. Moreover, the heat of the engine which is normally wasted is utilized in the heating process, thereby providing a more efficient system.

For use in vaporizing liquid nitrogen, the referenced system of U.S. Patent 197,712 comprises a LN2~GN2 flow line including a cryogenic pump, an engine coolant loop, and a hydraulic pump drive loop including a load. Work is done by the engine shaft to drive the cryogenic pump, hydraulic loop and load which is transferred by a hydraulic medium heat exchanger to the coolant loop. The heat produced in the engine is transferred to the coolant loop by the engine itself and combined with that of the first heat exchanger to be transferred to the LN2 < GN2 line by a vaporize heat exchanger.

More specifically, the loading means includes a hydraulic drive connected to a fluid pump such as a cryogenic pump, this hydraulic drive in turn being powered from a hydraulic pump connected to the engine shaft. A back pressure valve is provided in the circulation path of the hydraulic medium for the hydraulic pump thereby loading the hydraulic pump and engine shaft. The engine includes a coolant medium and a radiator for the coolant medium. The coolant pump is driven by the engine for circulating the coolant medium through the engine, the heat exchanger, and the radiator, The coolant picks up heat from the engine and from the hydraulic medium and delivers this heat to the fluid being pumped in the heat exchanger. Any excess heat is then removed from the coolant in the radiator.

The operation of the fluid or cryogenic pump is derived from the engine shaft. The amount of engine heat available is proportional to the engine shaft power. The amount of heat required to heat the fluid being pumped to a desired temperature is proportional to the flow rate of the fluid. By loading the engine so that the engine shaft power is proportional to the fluid flow rate, the amount of heat available is proportional to the fluid flow rate and hence can be made approximately equal to the amount of heat required.

Thus because the purpose of this invention is primarily to heat a pumped fluid, it will be instructive to consider the heat balance of a typical system. All of the energy required for operation of the system is provided by combustion of fuel in a diesel engine. The diesel engine drives a hydraulic pump and the hydraulic medium drives a cryogenic pump to pump liquid nitrogen. The engine is loaded by the hydraulic pump which pumps through a backpressure valve set at a pressure level higher than the pressure required to operate the cryogenic pump drive. The heat for vaporizing the liquid nitrogen is obtained from the work done on the nitrogen and hydraulic fluid, from the engine heat through the engine coolant, and possibly the engine exhaust gas.

The shaft power drives the hydraulic pump which transfers a portion of this energy into pump work in the nitrogen pump. The balance of the hydraulic pump work including pump inefficiency appears as heat in the hydraulic oil and is rejected into coolant in an oil-coolant heat exchanger.

Heat from the coolant is transferred to the nitrogen in the vaporizer. Any excess is rejected to the air which passes over the engine radiator. When no nitrogen is being pumped, the radiator rejects all of the coolant heat.

In one system for carrying on the foregoing, the shaft output can be supplied to a ram cylinder for reciprocatingly driving an actuator member on a cryogenic pump. However, that such as system requires various flow reversing valves together with a plurality of interconnection lines for its operation, all of which use subject to considerable surge pressures as the cylinder direction is reversed in each cycle. These surge pressures cause mechanical problems in the form of broken lines, leakage and undue wear due to excessive vibration of the unit and components.

There is therefore a need for improved system for Fluid Heating and Pumping which will overcome the foregoing defi"iencies.

DESCRIPTION OF THE E)FiAWiNGS Figure 1 is a schematic block diagram of a vaporizer system constructed in accordance with the present invention.

Figure 2 is a more detailed schematic block diagram of a vaporizer system of Figure 1, using a closed loop rotary hydraulic drive.

Figure 3 is a detailed schematic hydraulic diagram of a duai rotary driven pumping system constructed in accordancfs with Figure 2.

DETAILED DESCRIPTiON DF THE INVEiffION Referring first to the top porticn of Fig. 1, the vaporizer system includes a vaporizer heat exchanger 10 positioned in the flow path along which fluid to be vaporized is pumped as by a fluid pump 11 from a suitable supply tank 12.

Where the fluid to be vaporized constitutes a cryogenic liquid such as nitrogen, the resulting gaseous nitrogen at the outlet of the heat exchanger 10 might be utilized as a fluid displacement medium for an oil well indicated schematically at 13. While the principal embodiment of this invention will be described with respect to vaporization of a cryogenic liquid such as nitrogen, it should be understood that the basic method and system are applicable to the heating and/or vaporization of other fluids.

Still referring to Fig. 1 there is shown in the lower centre portion of a heat engine 14 which may be any suitable type of heat engine such as a gasoline engine or diesel engine which provides shaft power as well as heat. In Fig. 1, the shaft for engine 14 is schematically indicated by the heavy dashed-dot line 15, part of the power from the shaft being utllized to drive the fluid pump 11.

Associated with the engine 14 is radiator 16 shown to the left in Fig. 1 through which a coolant medium is circulated as by means of a coolant pump 1 7 driven by the shaft 1 5. A loading means for loading the shaft of the engine 14 is indicated by the block 1 8 and takes two different forms in the two embodiments to be subsequently described. In both of these embodiments, however, the coolant pump 17 will pass a cooling medium from the engine 14 through the heat exchanger 10 in the heat exchanging relationship with the fluid from pump 11 to vaporize this fluid, and thence through a temperature control 1 9 and the radiator 1 6 back to the heat engine.As will become clearer as the descriptlon proceeds, the temperature control 19 controls the radiator in a manner to radiate away excess heat in the coolant not absorbed in the heat exchanger 10 during the vaporization process.

Also illustrated to the lower right of Fig. 1 is a control panel 20 which incorporates the various pressure and temperature gauges and engine monitoring equipment.

It will be noted in Fig. 1 that there is not required any separate burner or boiler for effecting the vaporization and as a consequence, the entire system is more portable than would otherwise be the case. In this respect, there is indicated schematically in Fig. 1 a skid structure 21 for supporting the basic components described so that the entire system can be transported to a particular site such as an oil field or even to an ofhore drilling rig and vaporization of the cryogenic liquid nitrogen carried out.

Referring now to Fig. 2 there are illustrated several of the basic components of Fig. 1 together with a first type of loading means enclosed within the dashed-dot lines 1 8 in accord with an actual embodiment of this invention presently in use. As mentioned, this particular embodiment is utilized to vaporize cryogenic liquid nitrogen and as depicted in Fig. 2, the liquid nitrogen (LN2) is pumped from an appropriate supply tank through the cryogenic pump 11 to the vaporizer heat exchanger 10 and thence will emerge as gaseous nitrogen (GN2), The loading means 18. of FIG. 2 includes a hydraulic drive connected to the cryogenic pump 11 as indicated by the heavy dashed-dot line 23. A hydraulic pump 24 also designated P5 in FIG. 2 is connected to the shaft 1 5 of the diesel engine 14 for circulating an appropriate hydraulic medium to operate the hydraulic drive 22. Thus, the hydraulic medium heat exchanger passes from a hydraulic medium heat exchanger 27 pump 24 back pressure variable 28, also designated B1 in a simple closed loop.

The hydraulic medium heat exchanger 27 is in the flow path of the coolant medium passing from the vaporizer heat exchanger 10 to the temperature control 1 9 and radiator 16, this hydraulic medium heat exchanger serving to cool the hydraulic fluid.

In Fig. 2, the fluid flow path for the cryogenic liquid is indicated in the upper portion at 30, the circulating path for the coolant medium at 31 and the hydraulic circulating path for the coolant medium at 31 and the hydraulic circulating path at 32. Accumulators or surge tanks in the flow path 30 and 34-1, 34-2 in the hydraulic medium flow path are not needed for smoothing out the flow. However, safety pressure relief valves may be provided such as indicated in the flow path 30 at 55, and similarly pressure responsive bypass valves such as indicated at 38 may be provided.

Thus, a closed loop is provided which incorporates the hydraulic pump 24, the hydraulic drive 22.

and hydraulic heat exchanger 27.

A manual bypass valve 36 is provided to allow a small flow of liquid nitrogen around the vaporizer heat exchanger 10 to permit a reduction or "tempering" of the discharge temperature of the GN2 when this is desired.

Finally, there are depicted schematically in Fig. 2 various temperature gauges Tg and pressure gauges Pg in various ones of the circulating paths for monitoring purposes. These latter gauges would be located on the control panel 28 described in Fig. 1. It will be understood in an actual embodiment that further valves and gauges as well as surge tanks would be provided at appropriate locations along with priming valves and the like.

As shown more particularly in Figure 3, hydraulic motor 22 and fluid pumps 11 and both of the rotary drive type to thereby lessen or eliminate pressure surges in the lines. Preferably, the fluid pump is of the multisection type (three sections), each section of which Is staggered with respect to the others in order to smooth out the load it presents to the hydraulic drive. This results in a substantially vibrationfree system. In addition, the hydraulic drive system operates as a closed loop system to eliminate reservoirs and secondary pumps and to facilitate parallel operations.

In Fig. 2, the hydraulic medium pump 24 connected to the diesel engine shaft 1 5 constitutes a hydrostatic transmission-variable displacement pump to enable adjustment of the flow rate of the hydraulic medium for a given back pressure set by the back pressure valve 28 in the flow line 32. It will be appreciated that the higher the back pressure provided by the valve 28 the greater will be the load applied to the shaft 15 by the pump 24 if the pump rate is to remain constant. Actually, a given back pressure is set by the valve 28 and the variable displacement pump 24 adjusted to provide a flow rate for the cryogenic liquid such that all the liquid will be vaporized by the heat generated in the engine and transferred by the coolant medium.In other words, a proportionality between the flow rate and heat available for vaporizing the liquid is always maintained. The flow rate provided by the cryogenic pump 11 depends on the rate of operation of the hydraulic fluid through the hydraulic pump 24. Because the valve 28 maintains a constant back pressure on the hydraulic pump independent of the flow rate of hydraulic fluid, the power required to drive the hydraulic pump is proportional to the hydraulic fluid flow rate. Since the pump 24 is driven by the engine shaft, it will be appreciated that the engine power is proportional to the flow rate of the cyrogenic liquid through the vaporizer heat exchanger 10.

Further, the heat developed by the engine is approximately proportional to the power of the engine and thus for an increased flow rate there will be provided increased heat in the vaporizer heat exchanger 10 from the coolant mediurn passing through the diesel engine 14.

It will thus be evident from the foregoing that the available heat provided by the coolant medium in the vaporizer heat exchanger 10 is approximately equal to the heat required for complete vaporization of the cryogenic liquid at the particular flow rate. Essentially, the hydraulic drive and pump 24 embodied in the loading means 18 of Fig. 2 absorbs the diesel engine shaft power resulting in the generation of the necessary heat by the engine for vaporization.

It will be appreciated that the heat generated by the engine is not exactly proportional to the power generated. At low engine power levels and at very high speeds the heat generated per unit power increased. The engine generates a significant amount of heat even at idle conditions or when no power is being generated. To allow for these variations the system must be designed so that the available heat always equals or exceeds the heat required to vaporize the cryogenic liquid. As a result, there will occur some regimes of engine operation where there is excess heat which must be dissipated.

The radiator 16, as mentioned briefly heretofore, serves to radiate away any excess heat above that necessary to effect the desired vaporization of the cryogenic liquid. Any such excess heat would be in the circulating coolant medium passing to the radiator by way of the temperature control 19. The temperature control 1 9 may comprise simplyu a thermally-responsive valve arrangement to permit passage of the coolant medium directly to the diesel engine in the event no excess heat is present (the coolant medium simply bypasses the radiator 1 6), or pass a portion of the coolant medium through the radiator 1 6 to radiate away the excess heat. By utilizing a thermostatic control for the valve, the operation is completely automatic and self-regulating.

Referring now to both Figures 2 and 3 the hydraulic drive circuit of the present invention is characterized by rotary driven closed loop system. Thus, the shaft power output of the engine operates the hydraulic pump and load loop 32 including one side of hydraulic medium heat exchanger 27, the other side of which is tied into the engine thermal cooling loop so that the heat generated in the loop 32 is exchanged into loop 31 and thence to the vaporizer heat exchanger 1 0. The loop 32 is provided with a control mechanism in the form of a charge pump 25 which serves to keep the closed loop charged with oil and to make up for any leaks that exist in the system.Pump 25 is a small pump which draws from an associated reservoir 25-1 at a relatively low flow rate between the two, bathe the principal pump 24 in fresh cool liquid from the reservoir for cooling purposes and to flush out hot oil generated by the inefficiency of the pump. The charge pump also serves to generate a charge pressure to drive a servo valve (not shown) which is manually controlled by the operator to operate a piston integral with pump 24 to push on a swash plate which varies the displacement of the pump. Valve V1 serves as a sequencing valve or load valve and serves to keep the pressure constant between it and the pump output, so that it effectually serves as a variable orifice and thus variable load on the pump and engine.

By utilizing a rotary driven hydraulic drive the load and system can be kept relatively free of pulsations thereby eliminating the need for an independent partially open break in the loop 32 as was previously disclosed in our original U.S. patent 4,197,712.

Referring now to Figure 3 there is shown a complete and detailed hydraulic circuit diagram for a dual rotary driven hydraulic system constructed in accordance with the present invention. Thus, two separate hydraulic drives and a cryogenic pump circuits are provided, each of which has been given like numbers to those of Figure 2 with the addition of a -1, for the first circuit and a -2, for the second. It will be understood that a plurality of such circuits could be provided, two being sufficient for the purposes of illustration herein. The circuits are operated in parallel to each other except that means is provided for combining the flow and output of the several cryogenic pumps together before passed through the vaporizer heat exchanger means 10, which may include a plurality of heat exchangers for convenience of construction.The hydraulic pumping circuits are operated in parallel and are driven together. The pumps are turning all the time due to the nature of the system, but they are not pumping hydraulic fluid unless they are actuated by the system previously discussed in connection with the output of charge pump 25. Thus, one system can be at zero speed, while the other is operating at full speed independently of each other.

It will be noted that each of the hydraulic drive circuits is identical and each cryogenic pump includes a multi-section construction which is arranged to operate in sequence 1 200 out-of-phase with each other, so that the three sections shown provide a relatively even load for the motor. Each of the pump sections is provided with a vibration dampener Vln to further decrease pulsations. The input to each of the positive displacement sequentially driven piston pumps PN2 is provided additionally with a priming pump circuit including a hydraulic motor Ma which is driven by a pump on one of the engine shafts. The output of the motor drives the centrifugal pump PNt for raising the inlet pressure of liquid nitrogen delivered to the pumps PN2 to provide cavitation suppression and to provide a cooling fluid stream for maintaining the pumps PN2 at liquid nitrogen temperatures even if the system is idling.

The following is a parts list and description which identified by the drawing call-out number given in Figure 3.

ITEM QTY PART NO. NAME OR DESCRIPTIONS T ~ TRANSMISSION WITH OLUTCHES V7 CUSTOMER VALVE TF THERMOSTATIC FAN SC SURGE CHAMBER V16 VIBRATION INHIBITOR Vls VIBRATION INHIBITOR V14 VIBRATION INHIBITOR Vl2 VIBRATION INHIBITOR VI1 VIBRA TION INHIBITOR V,2 AUX INLET VALVE V6 CRYO. CENT. BOOST PUMP THROTTLE VALVE V5 TEMPERING VAL VE V4 H.P. PUMP PRIMING VALVE V3 BOOST PUMP PRIMING VALVE V2 BOOST PUMP DISCHARGE V1 BOOST PUMP SUCTION TV THERMOSTATIC BYPASS VALVE TS TEMPERATURE SENSOR (GN2 DiSCHARGE) TI3 TEMPERATURE INDICATOR (HYD. OIL) TI2 TEMPERATURE INDICATOR (COOLANT) TI1 TEMPERATURE INDICATOR (GN2 DISCHARGE) SV3 I'tAIN SAFETY RELIEF (12,500 PSIG) 5V2 THERMAL RELIEF (350 PSIG) SV, THERMAL RELIEF (60 PSIG) S2 STRAINER (AUX. H.P. PUMP INLET) STRAINER (BOOST PUMP INLET) Rl RUPTURE DISK (15,000 PSIG) PV3 BOOST PUMP SPEED CONTROL VALVE PV2 OVER PRESSURE RELIEF VALVE PVl 2 BACK PRESSURE VALVE PN2 2 AIRCO 3 GHPD H.P. RECIP. PUMP Fl1 CRYOGENIC CENTRIFUGAL BOOST PUMP PID FILTER DIFFERENTIAL PRESSURE PI@ PRESSURE INDICATOR (HYD. CHARGE PUMP) PI7 PRESSURE INDICATOR (CRYOBOOST HYD. CIRCUIT) PI6 PRESSURE INDICATOR (COOLANT CIRCUIT) PI5 PRESSURE INDICATOR (HYD. CHARGE PUMP) PI4 PRESSURE INDICATOR (HYD. MAIN LOOP)

ITEM QTY PART NO. NAME OR DESCRIPTIONS PI3 PRESSURE INDICATOR (GN2 DISCHARGE) PN1 PRESSURE INDICATOR (LN2 BOOST PUMP) P4 VARIABLE DISPLACEMENT HYD. PUMP P3 COOLANT CIRCULATING PUMP P2 HYDRAULIC PUMP (CENT. BOOST) P1 VARIABLE DISPLACEMENT HYD. PUMP M2 2 GMPD DRIVE MOTOR M1 CRYO-BOOST PUMP MOTOR HX7 ENGINE EXHAUST-LN2 HEX HX6 COOLANT -N2 HEAT EXCHANGER HX5 ENGINE EXHAUST -LN2 HEX HX4 OIL-WATER HEAT EXCHANGER HX3 ENGINE RADIATOR HX2 OIL-WATER HEAT EXCHANGER HX1 COOLANT -N2 HEAT EXCHANGER F2 HYD. OIL FILTER (MAIN LOOP) F1 HYD. OIL FILTER (CHARGE PUMP INLET) DC4 1"H.P. UNION (GN2 DISCHARGE) DC3 1" LN2 FIXED END (RETURN) DC2 1" LN2 FIXED END (AUX. INLET) DC1 2" LN2 FIXED END (BOOST PUMP INL.) D DIESEL ENGINE CV6 PRIMARY CHECK VALVE CV5 2 PUMP ISOLATION CHECK VALVE CV4 2 PECIRCULATION CHECK VALVE CV3 2 VAR. DISP. PUMP ISOLATIN CHECK VALVE ITEM QTY PART NO~. NAME OR DESCRIPTIONS

Claims (9)

1. A fluid pumping and heating system including a heat exchanger, a fluid pump for passing a fluid to be heated to a desired temperature through said heat exchanger, a heat engine which provides shaft power and heat output, part of said shaft power being used to operate said fluid pump and said heat being used in said heat exchanger, loading means for increasing the pumping load on the engine shaft to thereby provide sufficient heat to heat said fluid in said heat exchanger to a pre-determined temperature, the amount of heat provided being directly proportional to the flow rate of said fluid provided by said fluid pump, said loading means further inciuding a hydraulic drive and a hydraulic pump connected to the engine shaft for circulating a hydraulic medium to operate said hydraulic drive, said fluid pump being of the type including a rotary actuating member, and said hydraulic drive being of the type comprising a rotary motor having a rotary output shaft member.

2. A fluid pumping and heating system as in Claim 1 in which said hydraulic pump, said loading means, said hydraulic drive, and said hydraulic medium heat exchanger are connected together to form a closed loop hydraulic system.

3. A system as in Claim 1 in which said fluid pump comprises a multiple section pump, each section of which is staggered in operation with respect to the next.

4. A system as in Claim 3 further including a vibration damper connected in series to the input of each section of said pump.

5. A system as in Claim 3 in which said fluid pump is a three-section pump, each section of which is operable 1 200 out of phase with respect to the preceding section.

6. A system as in Claim 1 in which said fluid pump comprises a plurality of parallel connected fluid pumps together with means for combining their outputs together and delivering the same to said heat exchanger, and in which said hydraulic drive comprises a plurality of hydraulic drives respectively connected to one of said plurality of fluid pumps, said hydraulic motor comprising a plurality of hydraulic motors, each of which is connected to a respective one of said hydraulic drives, whereby each of said hydraulic pump, hydraulic drive and fluid pump forms a linkage capable of operations independently of the others.

7. A system as in Claim 6 in which said heat exchanger comprises a plurality of parallel connected units connected to the output of said fluid pumps through a common line.

8. A system as in Claim 1 further including a priming pump connected in series at the inlet of said fluid pump, said priming pump serving to provide a continuous cooling of the fluid pump and to provide an inlet pressure to prevent cavitation.

9. A fluid pumping and heating system according to claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.