CN105048870A - Method for power generation by employing medium-low-temperature waste heat generated in industrial production via reverse electrodialysis device - Google Patents

Abstract

The invention discloses a method for recovering medium and low temperature waste heat generated in industrial production by using a reverse electrodialysis device. The medium and low temperature waste heat fluid generated in industrial production is used to carry out reverse electrodialysis waste liquid with a low salt concentration through a heat exchange device. After heating and concentrating, the electrodialysis device is used to generate electricity; the solution chambers are separated by anion or cation exchange membranes alternately, and a spacer is placed between the exchange membranes to enhance mass transfer. The concentrated solution and fresh water enter the reverse electrodialysis device from the corresponding inlets to generate electricity. The generated reverse electrodialysis waste liquid is circulated to the heat exchange device for evaporation and concentration. The invention can realize the use of medium and low temperature waste heat which is difficult to utilize in industrial production for power generation. The salt solution components used have strong selective permeability between exchange membranes and high conversion efficiency. When the current density is 5A/m ² , the conversion efficiency exceeds 95%. The generated current is stable, and a higher voltage can be obtained through series connection. The material liquid in the process is recycled, no pollutants are discharged, the process is simple, and it is easy to realize industrialization.

Description

A method for generating electricity by using medium and low temperature waste heat generated in industrial production through a reverse electrodialysis device

technical field

The invention relates to a method for generating electricity by using industrial waste heat, which belongs to the field of energy conservation and environmental protection. In particular, it relates to a method for converting industrial waste heat into electrical energy by using a membrane method.

Background technique

With the rapid development of our country's national economy and the further expansion of industrial production, the energy crisis has become one of the important issues restricting industrial development. All countries have made various efforts and made remarkable achievements in improving energy efficiency. However, in metallurgy, chemical industry and other industries, there is still a lot of low-temperature waste heat that is difficult to be effectively utilized, especially when some low-temperature gases or liquids are discharged, a large amount of heat is taken away, resulting in a serious waste of energy.

Reverse electrodialysis power generation technology is a technology that uses the difference in chemical energy between concentrated salt solution and dilute solution to generate electricity. This technology has the characteristics of environmental friendliness and simple structure. At present, the research on reverse electrodialysis power generation technology mainly focuses on the use of salt difference energy between coastal rivers and seawater to generate power, but there is no report on the use of medium and low temperature waste heat for power generation.

The invention mainly uses industrial waste heat to concentrate reverse electrodialysis waste liquid with low salt concentration. After the concentrated concentrated solution and fresh water pass through the reverse electrodialysis device to generate electricity, the discharged waste liquid enters the heat exchange device to continue to concentrate, and the salt solution can be recycled. , no pollution to the environment.

Contents of the invention

The object of the present invention is to provide a method for utilizing the medium and low temperature waste heat generated in industrial production through a reverse electrodialysis device, which can use the waste heat generated in the industrial production process for power generation. It has the characteristics of high energy recovery rate, simple structure, and environmental friendliness.

In order to achieve the above object, the technical solution of the present invention adopts a method for generating electricity by using the medium and low temperature waste heat generated in industrial production through a reverse electrodialysis device, and the specific implementation is as follows:

The medium and low temperature waste heat fluid generated in industrial production is used to heat and concentrate the reverse electrodialysis waste liquid with low salt concentration through the heat exchange device, and after concentration, a concentrated solution with a concentration of 0.1-5mol/L is produced and passed into the reverse electrodialysis with fresh water The dialysis device generates electricity, and the reverse electrodialysis device includes two electrodes, two electrode solution chambers, multiple concentrated solution chambers and dilute solution chambers; the solution chambers are separated by anion or cation exchange membranes alternately, and the exchange membranes are placed The separation screen enhances mass transfer, concentrated solution and fresh water enter the reverse electrodialysis device at a flow rate of 0.1-3L/min from the concentrated solution inlet and fresh water inlet to generate power, and the reverse electrodialysis waste liquid generated by power generation is circulated to the heat exchange device for evaporation and concentration.

The heat exchanger is a plate or tube heat exchanger.

The medium and low temperature waste heat fluid is gas or liquid in industrial production, and the temperature is 60°C-300°C.

The composition of the reverse electrodialysis waste liquid is sodium chloride, sodium nitrate or potassium chloride and other soluble ionic compounds containing one or more metal ions, and the concentration of the salt solution is 0.1-0.9 mol/L.

The fresh water is tap water or a very low concentration salt solution containing one or more metal ions, such as an aqueous solution of soluble ionic compounds such as sodium chloride, sodium nitrate, and potassium chloride, and its salt concentration is 0.001-0.1mol/L.

The concentration of the concentrated solution is 0.4-2mol/L.

The two electrodes are respectively a cathode and an anode, the cathode is made of stainless steel, and the anode is made of metal titanium and graphite.

The main component of the electrode solution is a salt solution containing one or more variable-valence metal ions, including manganese salt, iron salt, nickel salt, and cobalt salt, and its concentration is 0.01-1mol/L.

The anion and cation exchange membranes have a thickness of 0.05-0.1 mm, and the partitions are traditional trapezoidal or diamond-shaped partitions.

The invention adopts the method of generating electricity by reverse electrodialysis and utilizes medium and low temperature waste heat to generate electricity, and waste heat which is difficult to utilize in industrial production is used for power generation. The present invention has the following advantages:

1. The present invention has strong adaptability to heat sources, and various heat sources can be used for heat exchange.

2. The salt solution components used in the present invention have strong selective permeability between exchange membranes, and the conversion efficiency between salt difference energy and electric energy is high. When the current density is 5A/m ² , the conversion efficiency exceeds 95%. The generated current is stable, and a higher voltage can be obtained through series connection to meet application requirements.

3. In the process of the present invention, the feed liquid is recycled, no pollutants are discharged, no large-scale equipment is needed, the process is simple, and it is easy to realize industrialization.

Description of drawings

Fig. 1 is a schematic diagram of the reverse electrodialysis device of the present invention.

In the figure, 1: cathode 2: anode 3: external circuit

C: Cation exchange membrane A: Anion exchange membrane

Fig. 2 is a schematic diagram of the reverse electrodialysis liquid flow of the present invention. The solid line in the figure is the flow direction of the concentrated solution, and the dotted line is the flow direction of the dilute solution.

Detailed ways

The following combined examples are intended to further illustrate the present invention, rather than limit the present invention.

After the medium and low temperature waste heat fluid generated in industrial production is exchanged with the dilute salt solution through the heat exchanger, the dilute salt solution is evaporated and concentrated into a concentrated solution. The concentrated solution and tap water respectively enter the concentrated solution chamber and the fresh water chamber of the reverse electrodialysis device. Driven by the concentration gradient, the ions in the concentrated solution selectively pass through the anion exchange membrane and the cation exchange membrane, resulting in the directional transfer of ions between the solutions. The directional transfer of ions between the solutions creates a potential difference on both sides of the electrodes, causing the generation of external circuit current. There is no chemical reaction in the process of reverse electrodialysis. In order to maintain the electronic balance in the solution, the electrode solution is added. The electrode solution circulates between the cathode and anode, and the electrochemical reaction occurs with the variable-valence metal ions to maintain the balance of electrons in the solution. The dilute solution produced in the reverse electrodialysis process is returned to the heat exchanger to continue to concentrate and be recycled.

Embodiment 1: the salt solution used in the reverse electrodialysis experiment is NaCl solution, the concentration of the concentrated solution is 0.4mol/L, the total chamber of the reverse electrodialysis device is 30, the total concentration of iron salt in the electrode solution is 0.08mol/L, and the thickness of the ion exchange membrane is is 0.08mm. A peristaltic pump is used to control the flow rate, and the concentrated solution and 0.02mol/L NaCl solution enter the chamber in a countercurrent manner, and the flow rate is 300ml/min. The cathode is stainless steel and the anode is titanium metal. The output current density is 4.8A/m ² , the energy density is 1.2W/m ² , the output voltage is 0.4V, and the concentration of dilute brine discharged after power generation is 0.27mol/L.

Embodiment 2: the saline solution used in the reverse electrodialysis experiment is NaCl solution, the concentrated solution concentration is 0.8mol/L, the total chamber of the reverse electrodialysis device is 40, and the total concentration of manganese salt in the electrode solution is 0.11mol/L, and the ion exchange membrane The thickness is 0.09mm. A peristaltic pump is used to control the flow rate, and the concentrated solution and tap water enter the chamber in a countercurrent manner with a flow rate of 300ml/min. The cathode is stainless steel and the anode is graphite. The output current density is 5A/m ² , the energy density is 1.5W/m ² , the output voltage is 0.45V, and the concentration of dilute brine discharged after power generation is 0.52mol/L.

Embodiment 3: the salt solution used in the reverse electrodialysis experiment is KCl solution, the concentration of the concentrated solution is 0.4mol/L, the total chamber of the reverse electrodialysis device is 30, the total concentration of iron salt in the electrode solution is 0.10mol/L, and the thickness of the ion exchange membrane is is 0.08mm. A peristaltic pump is used to control the flow rate, and the concentrated solution and tap water enter the chamber in a countercurrent manner with a flow rate of 200ml/min. The cathode is stainless steel and the anode is titanium metal. The output current density is 4.3A/m ² , the energy density is 1.6W/m ² , the output voltage is 0.35V, and the concentration of dilute brine discharged after power generation is 0.24mol/L.

Example 4: The salt solution used in the reverse electrodialysis experiment is a mixed solution of n _(KCl) :n _(NaCl) = 1:1, the concentration of the concentrated solution is always 1.0mol/L, and the total number of chambers of the reverse electrodialysis device is 50. The total concentration of cobalt salt in the electrode solution is 0.1mol/L, and the thickness of the ion exchange membrane is 0.09mm. A peristaltic pump is used to control the flow rate, and the concentrated solution and tap water enter the chamber in a countercurrent manner with a flow rate of 400ml/min. The cathode is stainless steel and the anode is graphite. The output current density is 5.2A/m ² , the energy density is 1.5W/m ² , the output voltage is 0.5V, and the concentration of dilute brine discharged after power generation is 0.56mol/L.

Claims (9)

1. one kind by anti-electrodialysis plant utilize produce in industrial production in low-temperature waste heat generating method, it is characterized in that comprising the following steps: by heat-exchanger rig utilize produce in industrial production in the low-temperature waste heat fluid anti-electrodialysis waste liquid lower to salt concentration carry out heating and concentrate, after concentrated, produce the concentrated solution that concentration is 0.1-5mol/L and fresh water pass into anti-electrodialysis plant and generate electricity, anti-electrodialysis plant comprises two electrodes, two electrode solution chambers and multiple concentrated solution chamber and weak solution chamber; Solution chamber employing anion or cation-exchange membrane interlock and separate, filter mass transfer enhancement is placed between exchange membrane, concentrated solution and fresh water enter anti-electrodialysis plant with the flow velocity of 0.1-3L/h from concentrated solution entrance and fresh water entrance and generate electricity, and the anti-electrodialysis waste liquid circulation that generating produces carries out evaporation and concentration to heat-exchanger rig.

2. according to claim 1 a kind of by anti-electrodialysis plant utilize produce in industrial production in low-temperature waste heat generating method, it is characterized in that: described heat exchanger is board-like or pipe heat exchanger.

3. according to claim 1 a kind of by anti-electrodialysis plant utilize produce in industrial production in the method for low-temperature waste heat generating, it is characterized in that: described middle low-temperature waste heat fluid is gas in industrial production or liquid, and temperature is 60 DEG C-300 DEG C.

4. according to claim 1 a kind of by anti-electrodialysis plant utilize produce in industrial production in low-temperature waste heat generating method, it is characterized in that: the composition of described anti-electrodialysis waste liquid is the soluble ion compound containing one or more metal ions such as sodium chloride, sodium nitrate or potassium chloride, and concentration of salt solution is 0.1-0.9mol/L.

5. according to claim 1 a kind of by anti-electrodialysis plant utilize produce in industrial production in low-temperature waste heat generating method, it is characterized in that: described fresh water is the salting liquid that running water or extremely low concentration contain one or more metal ions, and salting liquid is the aqueous solution of sodium chloride, sodium nitrate or potassium chloride soluble ion compound.

6. according to claim 1 a kind of by anti-electrodialysis plant utilize produce in industrial production in low-temperature waste heat generating method, it is characterized in that: described strong solution concentration is 0.4-2.0mol/L.

7. according to claim 1 a kind of by anti-electrodialysis plant utilize produce in industrial production in low-temperature waste heat generating method, it is characterized in that: described two electrodes are respectively negative electrode and anode, negative electrode is stainless steel, and anode is Titanium, graphite.

8. according to claim 1 a kind of by anti-electrodialysis plant utilize produce in industrial production in low-temperature waste heat generating method, it is characterized in that: described electrode solution composition is the salting liquid containing one or more variable valency metal ionses, and described salting liquid is the aqueous solution of manganese salt, molysite, nickel salt or cobalt salt.

9. according to claim 1 a kind of by anti-electrodialysis plant utilize produce in industrial production in the method for low-temperature waste heat generating, it is characterized in that: described anions and canons exchange membrane thickness is 0.05-0.1mm, filter be traditional trapezoidal or brilliant filter.