Energy Recovery System and Method

• US 20120261090A1
• Filed: 01/26/2010
• Published: 10/18/2012
• Est. Priority Date: 01/26/2010
• Status: Active Grant

• Current Assignee: TMEIC Corp. Americas
• Original Assignee: Tmeic Corporation (Toshiba Corporation)
• Inventors: Lara, Marcelo Andres, Durmaz, Ahmet
• Granted Patent: US 9,347,339 B2
• Time in Patent Office: Days
• US Class Current: 165/11.1
• CPC Class Codes: F01K 13/02 Controlling, e.g. stopping or starting
• CPC Class Codes: F01K 23/10 with exhaust fluid of one cycle heating the fluid in another cycle F01K17/025 takes precedence
• CPC Class Codes: F01K 25/08 using special vapours
• CPC Class Codes: F23J 15/06 of coolers
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
• CPC Class Codes: Y02E 20/30 Technologies for a more efficient combustion or heat usage

Abstract

A system and method for converting otherwise wasted energy produced in the form of heated gases as a byproduct of an industrial process into electrical energy. At least some waste gases are diverted from a typical exhaust structure through a heat exchanger and back into the exhaust structure. The amount of gases flowing through the heat exchanger is monitored and regulated by a controller. A heat source liquid is simultaneously circulated under pressure through the heat exchanger and through an organic Rankine cycle system. The amount of heat source liquid being circulated is also monitored and regulated by the controller. The ORC system converts the heat from the heat source liquid into electricity.

Claims

1. A system for converting excess energy generated as a byproduct of a fuel-powered industrial process in the form of heated exhaust gases directed to an exhaust structure into electrical energy comprising:

a heat exchanger having a gas input and a gas output, each connected to the exhaust structure, and having further a heat source liquid input and a heat source liquid output;

an organic Rankine cycle (ORC) system having a first input connected to the heat

source liquid output of said heat exchanger and a first output connected to the heat source liquid input of said first heat exchanger, said ORC system further having a generator delivering electric power to a second output of said ORC system;

gas circulating means for regulating the temperature of the liquid heat source by

changing the amount of gases circulated between the exhaust structure and the gas input and the gas output of said heat exchanger; and

heat source liquid circulating means for regulating the heat transfer to said ORC by changing the amount of liquid circulated between said ORC and said heat exchanger.

2. A system for converting excess energy generated as a byproduct of a fuel-powered industrial process in the form of heated exhaust gases directed to an exhaust structure into electrical energy comprising:

a heat exchanger having a gas input, a gas output, a heat source liquid input and a heat source liquid output;

first means for diverting at least a part of the heated exhaust gases into the gas input of said first heat exchanger;

second means connected to the gas output of said first heat exchanger for regulating the circulation through and exit of the exhaust gases from said first heat exchanger through a vent back into the exhaust structure;

third means for supplying and regulating the flow of heat source liquid to the heat source liquid input of said first heat exchanger; and

an organic Rankine cycle (ORC) system having a first input connected to the heat source liquid output of said first heat exchanger and a first output connected to the heat source liquid input of said first heat exchanger through said third means, said ORC system further having a generator delivering electric power to a second output of said ORC system.

3. The system of claim 2 wherein said first means comprises a tap connected at its input to the exhaust structure and at its output to the gas input of said first heat exchanger.

4. The system of claim 2 wherein said second means comprises:

an exhaust gases fan connected to the vent;

a first electric motor connected to said exhaust gases fan;

a first variable frequency drive connected to said first electric motor; and

first controller means connected to said first variable frequency drive for monitoring and regulating said first variable frequency drive.

5. The system of claim 4 wherein said second means further comprises:

second controller means connected to said first controller means for monitoring

fuel consumption data of the industrial process and transmitting that data to said first controller means;

first sensor means connected to the gas input of said first heat exchanger for measuring the temperature of the exhaust gases at that point and for transmitting that data to said first controller means;

second sensor means connected to the heat source liquid output of said first heat exchanger for measuring the temperature of the liquid at that point and for transmitting that data to said first controller means;

third sensor means connected to the heat source liquid output of said first heat exchanger for measuring the pressure of the heat source liquid at that point and for transmitting that data to said first controller means; and

a protective power transducer connected between the second output of said ORC system and said first controller means.

6. The system of claim 5 wherein said third means comprises:

a pressurized heat source liquid expansion tank;

a pressure relief valve connected to said expansion tank and to said first controller means;

a variable speed circulating pump connected at its input to said expansion tank and at its output to the heat source liquid input of said heat exchanger;

a second electric motor connected to said pump;

a second variable frequency drive connected to said second electric motor; and

fourth sensor means connected to said ORC for measuring the temperature of the cooling medium used by said ORC,

and wherein further said second variable frequency drive is further connected to said first controller means.

7. The system of claim 5 wherein said third means comprises:

a pressurized heat source liquid expansion tank;

a pressure relief valve connected to said expansion tank and to said first controller means;

a fixed speed circulating pump connected at its input to said expansion tank and at its output to the heat source liquid input of said heat exchanger; and

a second electric motor connected to said pump.

8. The system of claim 3 wherein said second means comprises an adjustable valve connected to said tap, the movement of which is controlled by a first controller.

9. A method for regulating the generation of electrical power from heated waste gases emitted from a fuel-powered industrial device into an exhaust structure using a heat exchanger having a gas input connected to the exhaust structure and a gas output connected to a variable speed exhaust fan which is itself connect to the exhaust structure and having further an organic Rankine cycle device (ORC) with an evaporator having a heat source liquid input connected to a liquid output of the heat exchanger and a heat source liquid output connected to a pressurized source of liquid further connected to a pump and thereafter to a liquid input of the heat exchanger wherein the ORC incorporates an expander coupled to a generator having an electrical output connected to a transducer comprising:

diverting at least a portion of the waste gases away from the exhaust structure into the gas input of the heat exchanger;

regulating the heat source liquid temperature by changing the amount of the waste gases so diverted by varying the speed of the exhaust fan;

controlling the amount of heat transferred from the heat source liquid to the ORC by changing the flow of the liquid circulated between the ORC and the heat exchanger by managing the operation of the pump; and

monitoring at the transducer the amount of electricity generated by the generator at the electrical output.

10. The method of claim 9 wherein the pump may be either a variable speed or a fixed speed pump.

11. A method for regulating the production of electrical power from heated waste gases generated as a byproduct of a fuel-powered industrial device wherein at least a part of the waste gases are diverted at a temperature measured by a first sensor into a gas input of a first heat exchanger before being expelled from a gas output of the first heat exchanger into an exhaust structure, the circulation of the waste gases through the heat exchanger being regulated by an exhaust gases fan driven by a first electric motor the speed of which is controlled by a first variable frequency drive (VFD) itself further controlled by a first controller incorporating a Proportional-Integral regulator, said first controller being connected to a second controller further connected to the fuel-powered device for monitoring fuel consumption and to the first sensor and wherein further a heat source liquid is delivered to a liquid input of the heat exchanger before being expelled from a liquid output of the heat exchanger into a heat source liquid circuit at a temperature measured by a second sensor and a pressure measured by a third sensor both of which sensors being connected to the first controller, the circulation of the heat source liquid through the heat exchanger being regulated by a pump driven by a second electric motor the speed of which is controlled by a second variable frequency drive (VFD) itself further controlled by the first controller, while the heat source liquid pump inlet is also connected to a liquid expansion tank subject to pressurization with inert gas, the pressure of which is monitored by the third sensor, the expansion tank also including a pressure relief valve monitored by the first controller, the heat source liquid expelled from the liquid output being then directed through an evaporator located in an organic Rankine cycle (ORC) system incorporating a heat sink circuit having a fourth sensor connected to the first controller for measuring the temperature of the ORC cooling medium, an expander connected to a generator and a power transducer connected between the generator and the second controller comprising:

ascertaining first whether data representing the fuel consumption of the fuel powered industrial device is available from the first controller;

if so, calculating an optimum target temperature for the heat source liquid according to the formula T*=K0(Thg,Fuel_C)+T1* where K0(Thg.Fuel_C) is an interpolation block or a function having as input variables the temperature feedback of heated gases entering the gas input (Thg.) and the device fuel consumption (Fuel_C), and T1* is the heat source liquid initial target temperature stored as a variable in the second controller;

otherwise calculating an optimal target temperature for the heat source liquid according to the formula T*=K0(Thg)+T1*;

further calculating a desired speed feed forward command for the first variable frequency drive according to the formula F*ff=K1(T*,n*) where F*ff is the exhaust gases fan speed expressed as a feed-forward command and K1(T*,n*) is an interpolation block or function having as input variables the calculated optimal heat source liquid temperature, T* and a target speed reference n* for the second variable frequency drive;

yet further calculating a speed adjustment according to the formula F*c=(Kp+Ki/s).(T*−

Tho) where F*c is the exhaust gases fan speed target compensation, Tho is the heat source liquid temperature as measured by the second sensor and Kp and Ki are, respectively, the proportional and integral gains of the Proprotional-Integral regulator;

setting the target speed of the first variable frequency drive according to the formula F*=F*ff+F*c;

further setting the maximum allowable speed of the first variable frequency drive according to the formula F*max=K2(T*,P,Pr) where K2(T*,P,Pr) is an interpolation block or function having as input variables the heat source liquid target temperature T*, the output power feedback of the ORC system in kilowatts P as measured by the transducer and Pr is a feedback signal from the third sensor representing the pressure of the heat source liquid circuit;

determining whether F*>

F*max;

if so, limiting the exhaust fan speed such that F*=F*max;

otherwise, calculating additionally the target speed n* for the second variable frequency drive according to the formula n*=K3(T*,Tc)+n1* where K3(T*,Tc) is an interpolation block or a function based on the input variables T* representing the heat source liquid target temperature at the outlet of the heat exchanger and Tc representing the temperature of the ORC system cooling fluid based on a feedback signal from the fourth sensor and where n1* is the base speed target of the second VFD;

further determining the maximum allowable speed for the second VFD according to the formula n*max=K4(P) where K4(P) is an interpolation block or a function for which the input variable is the output power P of the ORC as measured by the transducer;

ascertaining further whether n*>

n*max;

if so, limiting the pump speed such that n*=n*max; and

otherwise, until the fuel powered device is no longer in operation, returning to ascertaining first.