Patent Application
20180245800
The object of this patent application relates to the methods and apparatus for gas fired hot water plant waste heat recovery with incorporated high temperature water source heat pump for waste heat source utilization.
Heat pumps that have been used in prior art to enhance the heating power of hot water and power plants for the supply of industrial and district heating networks by utilizing the waste heat recovery have been deployed in a various designs. According to CN101900318A the waste heat of flue gas is used by incorporated air to air type heat pump to improve the heating performance of gas fired power plant, wherein the heat generated by integrated heat pump is fed to the air to water type heat exchanger being connected with supply pipeline of heat distribution circuit. In accordance the main disadvantage of represented approach is relatively low thermal performance compared to the proposed solution with water source type heat pump as explained hereinafter.
This invention relates to the hot water plants for the supply of industrial and district heating networks, wherein at least one incorporated water source high temperature heat pump is used to upgrade a low temperature heat from at least one waste heat source to the higher temperature heat output, which can be afterwards used directly or indirectly by at least one heat consumer for space or process heating, preferably in the scope of district heating. It is important to notice, that the heat pump according to the invention is used to heat up and rise the temperature of a primary heat transfer medium in a supply line of an open loop heating network, and/or in a return line of a closed loop heating circuit, wherein a design (i.e. operational) temperature of the primary heat transfer medium in a forward line of the heat distribution network is substantially higher than 45° C., at least when operating at normal operating conditions. It can be understood, that operating conditions of the heat distribution network are provided after commissioning and warm-up process where at least basic design temperature of the heat distribution network is successfully achieved and maintained (i.e. established) over at least a short period of time, hence at least one first heat releasing unit is turned on and operating by firing the fuel in the fuel burning (i.e. combustion) process in the scope of substantially a continuous operation, and at least one second heat releasing unit (i.e. heat pump) is turned on and operating for liquid-vapor phase change thermodynamic cycle process and waste heat source utilization. In accordance, at least one furnace with at least one incorporated boiler in the scope of said hot water plant and at least one water source high temperature heat pump are used to provide a first and a second heat source respectively in the scope of the heat distribution network, where individual unit shall substantially operate in the range between its minimum and maximum rated (i.e. full load) operating power, preferably at normal rated power for highest power efficiency developed in continuous operation.
Exemplary embodiment of the present invention will now be described with reference to the accompanying drawing, i.e. schematics of a hot water plant with incorporated water source high temperature heat pump in the scope of a heat distribution network, here shown as a simple single closed loop heating circuit.
Referring to the preferential embodiment of the power plant with incorporated water source high temperature heat pump (HP), the system comprises a furnace with incorporated boiler in the scope of first heat releasing unit of hot water plant (HWP), which preferably runs on a gas fuel, such as natural gas, liquefied petroleum gas, landfill gas, wood gas, biogas or coal for example. While hot water plant (HWP) first heat releasing unit is used for heat generation when powered, a significant amount of heat is released by the flue gas, wherein the heat is either used by heat consumer (HC) rather than discharged and dissipated to the ambient (O) through the exhaust pipe (P12) (i.e. chimney). It is important to notice, that the first heat source for heat consumer (HC) is preferably represented by boiler in the scope of the hot water plant (HWP), having an inlet and outlet aperture, whereby plurality of waste heat sources arise in the scope of the hot water plant (HWP) and incorporated heat pump (HP), at least when the hot water plant (HWP) and heat pump (HP) are turned on and powered, preferably at optimum efficiency or full load regime.
Effective recovery of waste heat is critical to provide a good total utilization of fuel energy, thus, first and most important waste heat source is represented by the stream of high temperature flue gas in exhaust system, which is a product of the combustion process within the hot water plant (HWP). Secondly, there is at least one additional waste heat source represented by heat pump (HP) compressors lubrication oil cooling systems (CS), which is under certain circumstances still important for good total waste heat source utilization.
According to the depicted preferential embodiment as represented on
As partially known from prior art, the waste heat of flue gas is eventually utilized by incorporated heat exchanger (HE) which collects the high temperature waste heat of flue gas in exhaust system, wherein the exhaust heat exchanger (HE) is capable to collect and transfer the heat of said waste heat source due to the significant temperature difference between the temperature of flue gas in exhaust system and the temperature of primary heat transfer medium in incorporated heat exchanger (HE). In addition, as explained in CN101900318A, the heat of the flue gas is not only collected, but also upgraded by incorporated air source heat pump, wherein it is essential to notice, that according to stated solution from prior art, the waste heat collected by heat pipe is used to upgrade the heat of flue gas by air to air heat pump principle utilization, hence the heat of high temperature flue gas is transferred to the primary heat transfer medium in a chamber of incorporated air to water type heat exchanger.
According to the invention, the exhaust system preferably comprises at least one condensing type heat exchanger (HE) to collect the heat of flue gas, wherein collected heat is transferred to the evaporator unit of water source high temperature heat pump (HP) by circulation of secondary heat transfer medium with aim to upgrade and enhance the heating power of the hot water plant (HWP). While the temperature of flue gas in exhaust system is rapidly reduced (preferably below 45° C.), the exhaust system may further comprise a suction fan (FI) for removal of flue gas from exhaust system. Furthermore, depicted embodiment comprises the lubrication oil cooling system (CS) in form of a heat exchanger, operably coupled to the evaporator unit with aim to collect the waste heat of heat pump (HP) compressors lubrication oil, which is afterwards upgraded by a liquid-vapor phase change thermodynamic cycle utilization process and transferred to the heat distribution network by incorporated water source high temperature heat pump (HP).
Since the apparatus according to preferential embodiment comprises at least one motorized valve, preferably hatch (HI) for flue gas stream manipulation (i.e. regulation), regulated by main control unit, the utilization of flue gas waste heat source is maximized by high temperature heat pump (HP), when the flue gas stream is fully enforced through the condensing heat exchanger (HE), hence it collects the waste heat required for heat pump (HP) principle utilization. If appropriate, the heat exchanger (HE) and heat pump (HP) shall be implemented in a multistage or cascade principle approach comprising a plurality of heat pumps (HP) and/or heat exchangers (HE) in parallel and/or serial connection to reach the optimized total waste heat source utilization.
While there are several options for waste heat source utilization it is essential to notice, that preferential embodiment of water source high temperature heat pump (HP) utilization uses at least one low temperature waste heat source for vaporization of working medium of incorporated heat pump (HP), wherein the condenser unit outlet is preferably fed (i.e. operably coupled) to the heat distribution circuit return line, more precisely to the inflow of the boiler in the scope of closed loop heat distribution system. It can be understood, that proposed concept is suitable for open loop heat distribution system as well, where it is essential to notice, that in such an embodiment the condenser unit outlet of said high temperature heat pump (HP) is fed to the inlet of the boiler in hot water plant (HWP) with aim to preheat the primary medium of said open loop heat distribution circuit, hence the temperature difference between involved heat transfer medium in the supply line and working medium in condenser unit is the highest. It can be understood, that suggested approach is essential for total waste heat source utilization, since the coefficient of performance is depended on temperature difference of involved heat transfer medium in the heat pump (HP) condenser and evaporator unit.
Furthermore, the invention relates to a method of the heat pump (HP) integration process and to a method of hot water plant (HWP) waste heat source utilization.
The following steps represent the key features of a heat pump (HP) integration and novel method for hot water plant (HWP) waste heat source utilization:
1. Integration of the water source high temperature heat pump (HP) having a condenser and evaporator unit with working medium for liquid-vapor phase change thermodynamic cycle utilization and at least one heat exchanger (HE), wherein:
A) the high temperature heat pump (HP) condenser unit is operably coupled to the heat distribution return line in a closed loop heat distribution system or to the supply line in an open loop heat distribution system;
B) the high temperature heat pump (HP) evaporator unit is operably coupled with at least one heat exchanger (HE) in a closed loop piping system with secondary heat transfer medium involved.
2. Collecting the heat by incorporated heat exchanger (HE) from at least one waste heat source, wherein the heat source is:
A) The stream of a flue gas in exhaust system; and/or
B) The lubrication oil in heat pump (HP) compressors lubrication oil cooling system.
3. Transfer of the heat from at least one heat exchanger (HE) to the high temperature heat pump (HP) evaporator unit, preferably by circulation of secondary heat transfer medium in the closed loop piping system.
4. Transfer of the heat from secondary heat transfer medium to the working medium in evaporator unit of the high temperature heat pump (HP), wherein at least low temperature heat from at least one waste heat source is upgraded by working medium liquid-vapor phase change thermodynamic cycle, hence the temperature of the working medium in condenser unit is substantially higher than the temperature of the working medium in evaporator unit.
5. Transfer of the heat from working medium in the high temperature heat pump (HP) to the primary heat transfer medium in the heat distribution network, wherein the
temperature of the primary heat transfer medium at condenser unit outlet is substantially higher than temperature of the primary heat transfer medium at condenser unit inlet, hence the high temperature output of condenser unit is fed to at least one boiler inlet in the scope of hot water plant (HWP), where the primary heat transfer medium is reheated by firing the fuel in the boiler.
6. Transfer of the heat from at least one boiler in the scope of hot water plant (HWP) to at least one heat consumer (HC) in open or closed loop heat distribution network.
7. Usage of high temperature primary heat transfer medium by at least one heat consumer (HC) in the scope of the district heating, industrial or technological process.
Furthermore, the following steps represent the key features of a method of using an apparatus according to the invention:
1. A fuel combustion process, where preferably at least one furnace is used for burning the fuel in the scope of the hot water plant (HWP) with aim to provide a first heat releasing unit for heating at least one heat transfer medium in the boiler, wherein at least one waste heat source arise when said first heat releasing unit is turned on and operating by firing the fuel in the combustion process. Accordingly, plurality of boilers and/or furnaces in parallel or serial connection shall be used to provide an advanced embodiment of the first heat releasing unit.
2. A waste heat recovery process which comprises a process of collecting the waste heat, wherein at least one waste heat recovery unit (i.e. heat exchanger (HE)) is used to collect at least a portion of the heat of at least one waste heat source from group of waste heat sources comprising a flue gas in exhaust system and lubrication oil in lubrication oil cooling system in the scope of the integrated heat pump (HP). Accordingly, plurality of waste heat recovery units in parallel or serial connection shall be used to provide an advanced embodiment of apparatus for waste heat recovery process utilization.
A liquid-vapor phase change thermodynamic cycle utilization process, wherein at least one water source high temperature heat pump (HP) shall be used to provide a second heat releasing unit for heating at least one heat transfer medium in said heat distribution network, at least when said heat pump (HP) is turned on and operating. Accordingly, plurality of heat pumps (HP) units in parallel or serial connection is used to provide an advanced edition of the second heat releasing unit.
Usage of collected heat for liquid-vapor phase change utilization, wherein at least a portion of collected heat is used for the liquid-vapor phase change cycle utilization and wherein at least a portion of the heat generated by at least one heat pump (HP) in the scope of the second heat releasing unit is used for heating the primary heat transfer medium in heat pump (HP) condenser unit.
Distribution of the heat in at least one closed loop circuit of said heat distribution network by circulation of at least one heat transfer medium, wherein the lowest temperature of the heat distribution medium in at least one boiler inlet in the scope of the first heat releasing unit is substantially higher than the lowest temperature of the heat distribution medium in at least one heat consumer (HC). Hence, at least one heat transfer medium in at least one return line of said closed loop heat distribution network is reheated by the heat pump (HP) principle utilization, at least when a design temperature of the heat distribution network is reached and said hot water plant (HWP) and heat pump (HP) are operating at full load; and/or
Distribution of the heat in at least one open loop heat distribution network by at least one heat transfer medium, wherein the inlet temperature of the primary heat distribution medium in at least one boiler inlet in the scope of the first heat releasing unit is substantially higher than temperature of the primary heat distribution medium in at least one heat pump (HP) condenser unit inlet, wherein said condenser unit inlet is operably connected to supply line of heat transfer medium source in open loop connection. Hence, at least one line of primary heat transfer medium in at least one supply line of said open loop heat distribution network is preheated by the heat pump (HP) principle utilization, at least when a design temperature of the heat distribution network is reached and said hot water plant (HWP) and heat pump (HP) are operating at full load.
In addition to represented method of using the apparatus according to the invention, few explanations and definitions are required, wherein combustion process is substantially a continuous process, while at least one furnace with incorporated boiler in the scope of hot water plant (HWP) normally operates in the range between its minimum and maximum rated operating power, preferably at normal rated power in continuous operation. Similarly the liquid-vapor phase change thermodynamic cycle utilization process is substantially a continuous process, wherein said heat pump (HP) operates in the range between its minimum and maximum rated operating power, preferably at normal rated power in continuous operation. If appropriate, the fuel combustion process in an advanced hot water plant (HWP) embodiment shall be provided by plurality of boilers and/or furnace units in the scope of the first heat releasing unit, wherein the heat in the scope of the first heat releasing unit is transferred in serial and/or in parallel connection and similarly, the liquid-vapor phase change thermodynamic cycle utilization process shall be utilized by plurality of heat pump (HP) units to provide a second heat releasing unit of the advanced hot power plant (HWP).
While one of the key features of a method and apparatus according to the invention is establishment of predetermined set point value of primary heat transfer medium temperature in heat distribution system, the thermal energy balance adjustment is executed by adapting the power of said heat pump (HP) and/or by adapting the power of said furnace in the scope of first heat releasing unit and/or by adapting the mass flow of the primary heat transfer medium through the heat distribution system. Accordingly the mass flow of the primary heat transfer medium in said closed loop heat distribution circuit is adapted by changing the flow velocity in said heat distribution circuit and/or the mass flow of the secondary heat transfer medium in said closed loop circuit is adapted by changing the flow velocity in said closed loop circuit, wherein the velocity of heat transfer medium in heat distribution network is adapted by switching (i.e. on/off regulation) and/or by adjusting the power of at least one circulation pump for mass flow adjustment. In addition, the mass flow of the primary heat transfer medium in depicted heat distribution circuit is alternatively adapted by stream flow regulation, wherein at least a portion of the primary heat transfer medium stream in the return line of said heat distribution circuit is redirected to the return line of said heat distribution circuit to provide a heat pump (HP) bypass connection, and/or wherein at least a portion of the primary heat transfer medium stream from said heat pump (HP) is redirected to a forward line of the heat distribution circuit to provide a hot water plant (HWP) bypass connection with aim to balance the power generated by first and second heat releasing units. Similarly the mass flow of the secondary heat transfer medium in said closed loop circuit for waste heat source utilization is adapted by stream flow regulation, wherein at least a portion of the secondary heat transfer medium stream is redirected in said closed loop circuit to provide a bypass connection for at least one waste heat recovery unit. Accordingly, the mass flow regulation of the primary heat transfer medium and/or the mass flow regulation of the secondary heat transfer medium for thermal energy balance adjustment is determined, controlled and executed by at least one control unit (i.e. electronic controller), wherein the position and/or the state (i.e. open/closed or on/off regulation) of the automated regulation means is adjusted in respect to the heat demand in said heat distribution network.
Apparatus according to the invention further comprises at least one control unit, wherein such a controller shall be an autonomous device for thermal management regulation or alternatively, at least basic functions of the thermal management controller for determination process, comparison process and execution process could be incorporated and implemented to the hot water plant (HWP) controller or in to the heat pump (HP) controller as well. In the determination process the environment and thermal conditions of heat distribution network is determined by the group of thermal, pressure or other sensors, wherein at least one input from at least one sensor of heat distribution network or hot water plant (HWP) is used for comparison process, where at least one value of at least one input parameter (i.e. preferably the value of an inlet temperature of the primary heat transfer medium hot water plant (HWP) is analyzed and compared to the nominal values, preferably being pre-defined and stored in the control unit. Accordingly the execution process comprises a process of executing instructions stored in control unit to generate appropriate output signal, where at least one parameter for thermal energy balance adjustment is generated, executed and performed by control electronics in cooperation with automated regulation means in order to reach and maintain the threshold set-point value, wherein said threshold value is defined between the maximum value and the minimum value for set point equal value with aim to provide a hysteresis for thermal energy balance adjustment.
It can be understood that control unit (i.e. electronic module) may communicate with various output devices where the temperature of the heat transfer medium in the heat transfer network is determined, controlled and regulated by a group of automated regulation means comprising motorized valves, pumps and sensors, wherein regulation means are preferably adapted to be manipulated by at least one control unit. And furthermore, the heat distribution process in heat distribution network is provided by at least one heat transfer medium, preferably by plurality of heat distribution mediums. Accordingly the heat in said heat transfer network is transferred from first heat releasing unit to the heat consumer (HC) by circulation of the primary heat transfer medium in at least one closed loop circuit, and similarly the heat from waste heat recovery unit is transferred to the heat pump (HP) by circulation of the secondary heat transfer medium in at least one closed loop circuit, wherein the heat upgraded by at least one heat pump (HP) is furthermore transferred from heat pump (HP) condenser unit to at least one boiler inlet in the scope of said hot water plant (HWP) by said primary heat transfer medium.
Summarizing, the heat of flue gases in the scope of the hot water plant (HWP) is used for utilization of water source high temperature heat pump (HP), wherein upgraded heat is preferably used for reheating or preheating of primary heat transfer medium in at least one heat distribution network. It can be understood, that all vital components of heat distribution circuit are preferably operably coupled for heat transfer medium circulation, wherein the compressor of the incorporated heat pump (HP) shall be driven by electric machine, powered by electricity from grid or generator, or alternatively if appropriate, a high temperature heat pumps (HP) compressor shall be mechanically coupled to and driven by additional internal combustion engine as well. Furthermore, as can be dearly read out from previous description, the primary heat transfer medium in preferential embodiment is water and similarly, the secondary heat transfer medium in preferential embodiment is mix of water and glycol.
In the foregoing description those skilled in the art will readily appreciate that modifications may be made to the invention without departing from the concepts disclosed herein. Such modifications are to be considered as included in the following claims, unless these claims expressly state otherwise.
| Number | Date | Country | Kind |
|---|---|---|---|
| P-201500215 | Sep 2015 | SI | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2016/000387 | 3/24/2016 | WO | 00 |
