Low temperature heat source thermoelectric conversion system using blend refrigerant

Abstract

The invention provides a low temperature heat source thermoelectric conversion system using a blend refrigerant, comprising an evaporator, sprinkler, a first heater and a second heater are successively arranged from the top down in the evaporator, a hot well containing a blend refrigerant is connected to the sprinkler through a pipeline with a booster transfer pump, a steam dryer is arranged at the upper part of the evaporator, the steam dryer is connected with an intake end of a turbine through a pipeline, the turbine is connected with a generator, and an exhaust end of the turbine is connected with a mixer through a pipeline, a reflux device is arranged at the lower part of the evaporator, the reflux device is connected with the mixer through a pipeline, and the mixer is connected with a condenser. The invention further provides a low temperature heat source thermoelectric conversion method using a blend refrigerant.

Claims

1. A low temperature heat source thermoelectric conversion method using a blend refrigerant, characterized by using a low temperature heat source thermoelectric conversion system using the blend refrigerant, the thermoelectric conversion system including a evaporator (8), wherein a sprinkler (7), a first heater (9-1) and a second heater (9-2) are successively arranged from the top down in the evaporator (8), a hotwell (1) containing the blend refrigerant is connected to the sprinkler (7) through a pipeline with a booster transfer pump (11), a steam dryer (6) is arranged at an upper part of the evaporator (8), the steam dryer (6) is connected with an intake end of a turbine (5) through a pipeline, the turbine (5) is connected with a generator (4), and an exhaust end of the turbine (5) is connected with a mixer (3) through a pipeline, a reflux device (10) is arranged at a lower part of the evaporator (8), the reflux device (10) is connected with the mixer (3) through a pipeline, and the mixer (3) is connected with a condenser (2), comprising the following steps: step 1: the blend refrigerant in the hot well (1) is pumped into the sprinkler (7) inside the evaporator (8) through the booster transfer pump (11), the blend refrigerant comes into contact with the surface of the first heater (9-1) with temperature higher than the boiling temperature of the blend refrigerant through the sprinkler (7) to allow refrigerant with boiling temperature lower than the surface temperature of the first heater (9-1) in the blend refrigerant to partially vaporize; step 2: vaporized refrigerant separated out first flows to the steam dryer (6), non-vaporized blend refrigerant enters the lower part of the evaporator (8) to form a level line (9-0), refrigerant below the level line (9-0) is unceasingly heated by a heat transfer surface of the second heater (9-2) with temperature higher than the boiling temperature of the blend refrigerant to unceasingly separate out vaporized refrigerant flowing to the steam dryer (6), and liquid particles in the vaporized refrigerant are removed in the steam dryer (6); step 3: dry vaporized refrigerant from the steam dryer (6) is transfused to the turbine (5), the vaporized refrigerant is expanded to do work in blade passages of the turbine (5) to be converted into mechanical energy, and drive the generator (4) to supply electric power to a grid in the form of electricity, and exhaust steam with work done in the turbine (5) is discharged to the mixer (3); step 4: remaining vaporized refrigerant below the level line (9-0) in the evaporator (8) and with partial boiling temperature lower than the surface temperature of the first heater (9-1) undergoes further vaporization under heating from the heat transfer surface of the second heater (9-2), and non-vaporized refrigerant with high density tends to stay at the lower part of the evaporator (8) to form an area with minimum concentration of refrigerant components with the boiling temperature lower than the surface temperature of the first heater (9-1); and step 5: a refrigerant lean liquid is taken from the reflux device (10) based on a total amount of refrigerant pumped by the booster transfer pump (11) into the evaporator (8) as well as a component ratio of the refrigerant with the boiling temperature lower than the surface temperature of the first heater (9-1) and the level line (9-0), and delivered to the mixer (3) to mix with a discharged exhaust steam with work done in the turbine (5), the exhaust steam and the non-vaporized blend refrigerant are fully mixed in the mixer (3), and then led to the condenser (2), after the steam and liquid mixture is cooled in the condenser (2), vaporized refrigerant of the steam and liquid mixture is gradually absorbed by the refrigerant lean liquid, and the mixture is finally sent into the hot well (1) in a liquid state to complete a thermoelectric conversion cycle; wherein an amount of the refrigerant lean liquid taken from the reflux device (10) is controlled by multi-impulse control of the level line (9-0) of the evaporator (8), reference parameters for multi-impulse control of the level line (9-0) of the evaporator (8) include flow, temperature and density of vaporized refrigerant at an inlet of the turbine (5), flow, temperature and density of liquid refrigerant at an outlet of the booster transfer pump (11), and flow, temperature and density of the refrigerant lean liquid in the pipeline between the outlet of the reflux device (10) and an inlet of the mixer (3).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a Kalina cycle process.

(2) FIG. 2 is a schematic diagram of a low temperature heat source thermoelectric conversion system using a blend refrigerant provided by the invention.

(3) FIG. 3 is a schematic diagram of a cycle process of the system provided by the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

(4) The invention is described in detail in combination with the following drawings and preferred embodiments for clear understanding.

(5) The invention provides a low temperature heat source thermoelectric conversion system using a blend refrigerant. The blend refrigerant satisfies the following two conditions: (1) more than two refrigerants with stable chemical compositions; and (2) more than two different refrigerants with stable boiling points and capable of forming unfixed boiling points. The (1) refers to a mechanical mixture of more than two chemical compositions without chemical reaction, such as an ammonia-water mixture at any ammonia-water ratio, or a mixture of ammonia, water and other refrigerant. The low temperature heat source refers to a heat source with temperature higher than the boiling temperature of the refrigerant and containing industrial process waste heat, solar energy, terrestrial heat, etc. Thermoelectric conversion refers that low-grade heat energy of the low temperature heat source is converted into electric energy output to the grid.

(6) FIG. 2 is a schematic diagram of a low temperature heat source thermoelectric conversion system using a blend refrigerant provided by the invention. The low temperature heat source thermoelectric conversion system using a blend refrigerant comprises a hot well (1) containing a blend refrigerant, one end of the booster transfer pump (11) is connected with the hot well (1) through a pipeline, and the other end is connected to an evaporator (8) through a pipeline, a steam dryer (6) is arranged at the upper part of the evaporator (8), the steam dryer (6) is connected with an intake end of a turbine (5) through a pipeline, the turbine (5) is connected with a generator (4), and an exhaust end of the turbine (5) is connected with a mixer (3) through a pipeline, a reflux device (10) is arranged at the lower part of the evaporator (8), the reflux device (10) is connected with the mixer (3) through a pipeline, the mixer (3) is connected with a condenser (2), and cooling water (12) is introduced in the condenser (2).

(7) A sprinkler (7), a first heater (9-1) and a second heater (9-2) are successively arranged from the top down in the evaporator (8), the sprinkler (7) is located at the top in the evaporator (8) and connected with the booster transfer pump (11). The first heater (9-1) and the second heater (9-2) share the same low temperature heat source, that is, the low temperature heat source enters the first heater (9-1), and then enters the second heater (9-2) from the first heater (9-1).

(8) A flow control valve (13) is arranged on the pipeline connecting the reflux device (10) with the mixer (3).

(9) In combination with FIG. 3, the operating method of the system is as follows:

(10) the blend refrigerant in the hot well (1) is pumped into the evaporator (8) through the booster transfer pump (11), the blend refrigerant from the booster transfer pump (11) comes into contact with the surface of the first heater (9-1) with temperature higher than the boiling temperature of the blend refrigerant through the sprinkler (7) to allow refrigerant with boiling temperature lower than the surface temperature of the first heater (9-1) in the blend refrigerant to partially vaporize;

(11) vaporized refrigerant separated out first flows to the steam dryer (6), non-vaporized blend refrigerant enters the lower part of the evaporator (8) to form a level line (9-0), refrigerant below the level line (9-0) is unceasingly heated by a heat transfer surface of the second heater (9-2) with temperature higher than the boiling temperature of the blend refrigerant to unceasingly separate out vaporized refrigerant flowing to the steam dryer (6), and liquid particles in the vaporized refrigerant are removed in the steam dryer (6);

(12) dry vaporized refrigerant with liquid particles being removed in the steam dryer (6) is transfused to the turbine (5), intrinsic energy (pressure and enthalpy) of the vaporized refrigerant is expanded to do work in blade passages of the turbine (5) to be converted into mechanical energy, and drive the generator (4) to supply electric power to a grid in the form of electricity;

(13) exhaust steam with work done in the turbine (5) is discharged to the mixer (3);

(14) remaining vaporized refrigerant below the level line (9-0) in the evaporator (8) and with partial boiling temperature lower than the surface temperature of the first heater (9-1) undergoes further vaporization under heating from the heat transfer surface of the second heater (9-2), and non-vaporized refrigerant with high density tends to stay at the lower part of the evaporator (8) to form an area with minimum concentration of refrigerant components with the boiling temperature lower than the surface temperature of the first heater (9-1) in the reflux device (10); and

(15) the refrigerant lean liquid is taken from the reflux device (10) based on the total amount of refrigerant pumped by the booster transfer pump (11) into the evaporator (8) as well as the component ratio of the refrigerant with the boiling temperature lower than the surface temperature of the first heater (9-1) and the level line (9-0), and delivered to the mixer (3) to mix with the discharged exhaust steam with work done in the turbine (5), the exhaust steam and the non-vaporized blend refrigerant are fully mixed in the mixer (3), and then led to the condenser (2), after the steam and liquid mixture is cooled by the cooling water system (12) in the condenser (2), vaporized refrigerant is gradually absorbed by the refrigerant lean liquid, and the mixture is finally transferred into the hot well (1) in a liquid state to complete a thermoelectric conversion cycle.

(16) In the process of delivering the refrigerant lean liquid from the reflux device (10) to the mixer (3) of the invention, the amount of the refrigerant lean liquid taken from the reflux device (10) is precisely controlled by multi-impulse control of the design level line (9-0), thus improving the mixing process of the refrigerant lean liquid delivered to the mixer (3) and the discharged exhaust vapor with work done in the turbine (5), and improving the absorption efficiency of vaporized refrigerant by the refrigerant lean liquid in the condenser (2). The specific method comprises the following steps: 1. setting the level line (9-0) in the evaporator (8), and designing the level line as a control goal based on different heat sources and output power; 2. setting measuring points for flow, temperature and density of the vaporized refrigerant at the inlet of the turbine (5), the parameter group supports the booster transfer pump (11) to control the output power and realize level line control; 3. setting sampling points for flow, temperature, density and other operating parameters of the pumped liquid refrigerant on the outlet pipeline of the booster transfer pump (11), the parameter group is used as a basis for control of output power, and also a basis for control and comparison of liquid flow into the mixer (3); and 4. setting sampling points for flow, temperature, density and other operating parameters of the refrigerant lean liquid on the pipeline from the outlet of the reflux device (10) to the inlet of the mixer (3), the parameter group is used as a basis for control, comparison and online setup of liquid flow into the mixer (3).

(17) The amount of the refrigerant lean liquid taken from the reflux device (10) can be obtained after operation by using a PID control algorithm based on the control parameters. Liquid and vaporized refrigerants in the mixer (3) can be mixed at a precise proportion through control of the flow control valve (13), so that the refrigerant lean liquid can complete absorb and liquefy the vaporized refrigerant, stabilizing the backpressure of the turbine, improving the cycle efficiency. and making it convenient to adjust the volume of cooling water and operating conditions of cooling towers.

(18) As a control goal is set for the reflex device.fwdarw.mixer process and the control goal is realized by multi-impulse control in the invention, with the control precision not lower than 1%, the mixing efficiency is improved by about 10%, and the cycle efficiency is improved by about 2% in the invention compared with the U.S. Pat. No. 434,656 patent.