Temperature control method for alkaline electrolytic cell

Abstract

The invention discloses a temperature control method for an alkaline electrolytic cell, and the alkaline electrolytic cell has five states, namely a working state, in which the temperature in the alkaline electrolytic cell is maintained at a stable working temperature level; a power-off state: in the power-off state, the temperature in the alkaline electrolytic bath is close to the environment temperature; a standby state: in the standby state, the temperature in the alkaline electrolytic bath is controlled within a set temperature range; in a cold starting state, an external heating device is adopted to heat the alkaline electrolytic bath in the cold starting state; and a hot start state in which the alkaline electrolytic cell starts hot start from the standby state. Different temperature control strategies are operated according to different states, and efficient thermal management of the alkaline electrolytic cell is achieved, so that the temperature of the alkaline electrolytic cell is stabilized within a safe and efficient range, and high-precision and rapid control over the temperature of the alkaline electrolytic cell can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic cell control, and particularly relates to a method for controlling the temperature of an alkaline electrolytic cell. Background Art

[0002] An alkaline electrolytic cell is the most commonly used hydrogen production equipment by electrolysis. During the operation of the alkaline electrolytic cell, too high a temperature will damage the equipment and affect its service life, while too low a temperature will cause an increase in resistance and consumption. Therefore, the stable operating temperature of an alkaline electrolytic cell is usually 70 - 90°C. The importance of temperature control lies in ensuring work efficiency and safety. Too high or too low a temperature will affect work efficiency and even damage the equipment. Therefore, it is necessary to strictly control the operating temperature of the electrolytic cell to ensure the best use effect and equipment life.

[0003] There are many factors affecting the temperature inside the cell, such as the heat energy generated by the electrochemical reaction, heat conduction with the outside world, and the influence of the cooling system, etc. Therefore, how to stabilize the temperature of a PEM (Proton Exchange Membrane) alkaline electrolytic cell within a safe and efficient range is also a problem worthy of exploration, and how to achieve high-precision and rapid control of the cell temperature is also an important problem. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a method for controlling the temperature of an alkaline electrolytic cell, so as to stabilize the temperature of the electrolytic cell within a safe and efficient range.

[0005] To achieve the above purpose, the technical solution of the present invention is:

[0006] A method for controlling the temperature of an alkaline electrolytic cell, the alkaline electrolytic cell includes five states, namely:

[0007] Operating state, in the operating state, the temperature inside the alkaline electrolytic cell is maintained at a stable operating temperature level;

[0008] Shutdown state, in the shutdown state, the temperature inside the alkaline electrolytic cell approaches the ambient temperature;

[0009] Standby state, in the standby state, the temperature inside the alkaline electrolytic cell is controlled within a set temperature range;

[0010] Cold start state, in the cold start state, an external heating device is used to heat the alkaline electrolytic cell;

[0011] Hot start state, in the hot start state, the alkaline electrolytic cell starts a hot start from the standby state.

[0012] Optionally, in the working state, the working temperature in the alkaline electrolytic cell is:

[0013]

[0014] Where f(T) is a nonlinear function related to temperature, and u is a control variable related to the circulating alkali solution flow rate.

[0015] Optionally, the control amount u related to the circulating alkali solution flow rate is obtained by:

[0016] Introduce the error variable e=T between the alkaline electrolytic cell temperature and the preset temperature d -T, taking the derivative of e, we get

[0017]

[0018] f(T) has upper and lower limits, namely

[0019] |f(T)|<ρ

[0020] To achieve e→0, the control quantity u related to the circulating alkali solution flow rate is set as

[0021]

[0022] Optionally, in the standby state, the electrolyte is kept warm by using the resistance heating element or heat storage device of the alkaline electrolytic cell so that the temperature inside the alkaline electrolytic cell is controlled within a set range; in the standby state, the heat preservation power is 8% of the rated power.

[0023] Optionally, in the cold start state, an external heating device is used to heat the electrolytic cell, and the heating power is 15% of the rated power.

[0024] Optionally, in the working state, the temperature in the alkaline electrolyzer is maintained at a stable working temperature level through a second type absorption heat pump and a circulating water network.

[0025] Optionally, the alkaline electrolytic cell temperature control method also includes: constructing a dynamic model of electrochemistry and heat conduction of the alkaline electrolytic cell, taking the circulating alkali solution flow rate as the control object, constructing a control law for temperature control, obtaining the alkali solution flow rate based on the control law, and adjusting the alkali solution flow rate by detecting the alkali solution temperature at the outlet.

[0026] Optionally, the operating temperature in the alkaline electrolytic cell is obtained by:

[0027] The electrochemical working process of the alkaline electrolyzer is modeled as:

[0028]

[0029] Among which, U cell and U rev are respectively the terminal voltage and the reversible voltage of the electrolysis chamber; r 1，2 is the ohmic resistance parameter of the electrolyte; A is the area of the electrolysis module; I is the current of the electrolytic cell; s 1,2,3 is the overvoltage coefficient; t 1,2,3 is the overvoltage coefficient; T el is the temperature of the electrolyte;

[0030] The sum of the polarization voltage and the ohmic loss voltage is characterized by the overvoltage η, that is

[0031]

[0032] U cell = U rev + η

[0033] The calculation formula for the heat conduction of the electrolytic cell is:

[0034]

[0035] Among which, U th is the thermal neutral voltage; Q el is the heat dissipation of the AWE electrolytic cell; C p,KOH is the specific heat capacity corresponding to the average temperature when the alkaline solution flows out and into the electrolytic cell; V KOH is the flow rate of the alkaline solution flowing out of the electrolytic cell;

[0036] ρ KOH is the density corresponding to the average temperature when the alkaline solution flows out and into the electrolytic cell; T H0 is the temperature of the alkaline solution flowing out of the electrolytic cell; T Hr is the temperature when the alkaline solution just flows into the electrolytic cell; m O2 is the mass flow rate of oxygen at the outlet of the electrolytic cell; m H2 is the mass flow rate of hydrogen at the outlet of the electrolytic cell; h O2 and h H2 are respectively the enthalpy values of oxygen and hydrogen at the outlet of the electrolytic cell; R t is the thermal resistance; T a is the ambient temperature.

[0037] According to the above equation, the working temperature in the alkaline electrolytic cell is

[0038]

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] The method of the present invention divides the operating state of the alkaline electrolyzer into 5 states in a refined manner, and operates different temperature control strategies according to different states, realizing efficient thermal management of the alkaline electrolyzer, so that the temperature of the alkaline electrolyzer is stabilized within a safe and efficient range, and high-precision and rapid control of the temperature of the alkaline electrolyzer can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the composition of the thermal management device for the alkaline electrolyzer;

[0042] Figure 2 It is a schematic diagram of the composition of the alkaline electrolyzer temperature control method provided by the embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] Embodiment:

[0044] The technical solutions of the present invention will be further described below with reference to the drawings and embodiments.

[0045] Refer to Figure 1 As shown, it is a schematic diagram of the composition of the existing thermal management device for the alkaline electrolyzer, mainly composed of an alkaline electrolyzer system, a second type of absorption heat pump (absorption heat transformer, AHT), and a circulating water network. Operating points are taken in each component, and are represented by H, R, and U plus numbers.

[0046] In order to stabilize the temperature of the alkaline electrolyzer within a safe and efficient range and achieve high-precision and rapid control of the alkaline electrolyzer temperature, as Figure 2 shown, the alkaline electrolyzer temperature control method provided by the embodiment of the present application divides the state of the alkaline electrolyzer into 5 modes, such as the operating state (ON), the shutdown state (OFF), the standby state (standby, STB), the cold start (coldstart, CLD), and the warm start (warm start, WRM).

[0047] In the operating state, hydrogen and oxygen are generated by the electrolysis reaction of water in the alkaline electrolyzer, and the temperature in the alkaline electrolyzer is maintained at a stable operating temperature level through the second type of absorption heat pump and the circulating water network to ensure the efficient progress of the reaction.

[0048] In the shutdown state, all operations of the alkaline electrolyzer stop, and the temperature in the alkaline electrolyzer approaches the ambient temperature; in this state, the alkaline electrolyzer does not perform the electrolysis reaction.

[0049] In the standby state, the alkaline electrolyzer is in a low-power consumption mode, consuming the minimum amount of electricity to prevent the temperature inside the alkaline electrolyzer chamber from dropping. In this state, the temperature inside the alkaline electrolyzer is controlled within a stable range to facilitate restarting at any time and producing hydrogen.

[0050] In the cold start state, after the alkaline electrolyzer has not been operating for a long time, it takes a certain amount of time to preheat to the rated operating temperature before hydrogen can be produced. To accelerate the heating rate of the electrolyte, an external heating device is used to heat the electrolyzer.

[0051] In the hot start state, to accelerate the heating of the electrolyte to the rated operating temperature, the alkaline electrolyzer directly resumes from the standby state to the hydrogen production working state within a short time.

[0052] It can be seen that by finely dividing the working state of the alkaline electrolyzer into 5 states and operating different temperature control strategies according to different states, the method realizes the efficient thermal management of the alkaline electrolyzer, thereby stabilizing the temperature of the alkaline electrolyzer within a safe and efficient range and enabling high-precision and rapid control of the temperature of the alkaline electrolyzer.

[0053] In a specific embodiment, in the working state, the alkaline electrolyzer generates hydrogen and oxygen through the electrolysis of water. At the same time, the second-type absorption heat pump and the circulating water network maintain the temperature inside the alkaline electrolyzer chamber at a stable level to ensure the efficient progress of the reaction. At this time, the electrolysis power is often not constant. The electrochemical working process of the alkaline electrolyzer is modeled as:

[0054]

[0055] Where U cell and U rev are the terminal voltage and reversible voltage of the electrolysis chamber, respectively, in V; r 1，2 is the ohmic resistance parameter of the electrolyte, in Ω·m 2 ; A is the area of the electrolysis module, in m 2 ; I is the current of the electrolyzer, in A; s 1,2,3 is the overvoltage coefficient, in V; t 1,2,3 is the overvoltage coefficient, in m 2 / A; T el is the temperature of the electrolyte, in °C.

[0056] The polarization voltage and the ohmic loss voltage are characterized by the overvoltage η, that is

[0057]

[0058] U cell = U rev + η

[0059] The calculation formula for the heat conduction of the electrolytic cell is

[0060]

[0061] Among them, U th is the thermal neutral voltage, V; Q el is the heat dissipation of the AWE electrolytic cell, kJ / h; C p,KOH is the specific heat capacity corresponding to the average temperature when the alkaline solution flows out and into the electrolytic cell, kJ / (kg·℃); V KOH is the flow rate of the alkaline solution flowing out of the electrolytic cell, m 3 / h; ρ KOH is the density corresponding to the average temperature when the alkaline solution flows out and into the electrolytic cell, kg / m 3 ; T H0 is the temperature of the alkaline solution flowing out of the electrolytic cell (i.e., the initial temperature of the driving heat source), ℃; T Hr is the temperature of the alkaline solution just flowing into the electrolytic cell, ℃; m O2 is the mass flow rate of oxygen at the outlet of the electrolytic cell, kg / h; m H2 is the mass flow rate of hydrogen at the outlet of the electrolytic cell, kg / h; h O2 、h H2 are the enthalpy values of oxygen and hydrogen at the outlet of the electrolytic cell, kJ / kg; R t is the thermal resistance, ℃ / W; T a is the ambient temperature, ℃.

[0062] According to the above equation, the working temperature in the alkaline electrolytic cell is

[0063]

[0064] Among them, f(T) is a non-linear function related to temperature, and u is a control variable related to the flow rate of the circulating alkaline solution.

[0065] Introduce the error variable e = T d -T of the cell temperature and the preset temperature. Taking the derivative of e gives

[0066]

[0067] Due to the limitations of actual physical conditions, f(T) has upper and lower limits, that is

[0068] |f(T)| < ρ

[0069] To achieve e→0, the control variable u is set as

[0070]

[0071] In this way, the control variable u related to the flow rate of the circulating alkaline solution is calculated through parameters, so as to control the coolant flow rate and realize the temperature regulation of the alkaline electrolytic cell.

[0072] In a specific embodiment, in the standby state, the electrolyte is kept warm by using the resistance heating element or heat storage device of the electrolytic cell. In cold standby, the insulation power is 8% of the rated power. In this way, the temperature inside the alkaline electrolytic cell is controlled within a relatively stable range, so that it can be restarted at any time and hydrogen production can be carried out.

[0073] In a specific embodiment, in the cold start (CLD) state, an external heating device is used to heat the electrolytic cell, and the heating power is 15% of the rated power, so that the electrolyte temperature rise speed can be accelerated.

[0074] At the same time, by constructing a dynamic model of electrochemistry and heat conduction in the alkaline electrolytic cell, taking the circulating alkali solution flow as the control object, a control law for temperature control is constructed, and the alkali solution flow is obtained based on the control law. The alkali solution flow is adjusted by detecting the alkali solution temperature at the outlet.

[0075] return Figure 1 As shown, on the hydrogen side, the mixture of alkali solution and gas flows out of the electrolyzer and passes through the evaporator and generator in sequence to be cooled step by step.

[0076] Then, the alkali solution is refluxed, and when the first regulating valve is opened and the second regulating valve is closed, the mixture will not pass through the first regenerative heat exchanger;

[0077] On the contrary, it will flow through the first heat recovery heat exchanger to exchange heat with the cooled reflux alkali solution, and then flow through the circulating water preheater and the first cooling fan for further cooling, and enter the gas-liquid separator for gas-liquid separation.

[0078] On the oxygen side, after the mixture of alkali solution and gas flows out of the generator, when the third regulating valve is opened and the fourth regulating valve is closed, the mixed fluid does not pass through the second regenerative heat exchanger;

[0079] On the contrary, it will flow into the second heat recovery heat exchanger to exchange heat with the cooled reflux alkali solution.

[0080] Then, after being cooled by the second cooling fan, it flows into the gas-liquid separator for gas-liquid separation. The obtained alkali liquid merges with the alkali liquid separated from the hydrogen side to form a reflux alkali liquid, which flows through the heat recovery exchanger and is finally pumped into the electrolytic cell through a circulation pump.

[0081] In the circulating water network, the preheated circulating water flows into the absorber, absorbs heat, increases temperature, and supplies heat to users;

[0082] The cooling water flows through the circulating water preheater again to be preheated, and then enters the absorber for recycling. As a gas desiccant regeneration device for heat users, the commonly used water absorbents for drying hydrogen in industrial production are liquid (such as sulfuric acid, lithium bromide) and solid (such as sodium hydroxide, calcium chloride).

[0083] In this way, the cooling of the lye and the recovery of waste heat can be achieved through the above operations.

[0084] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those of ordinary skill in the art to understand the content of the present invention and implement it accordingly, and it should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the essence of the content of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for controlling the temperature of an alkaline electrolyzer, characterized in that, The alkaline electrolyzer includes five states, namely: Working state. In the working state, the temperature inside the alkaline electrolyzer is maintained at a stable working temperature level. Shutdown state. In the shutdown state, the temperature inside the alkaline electrolyzer approaches the ambient temperature. Standby state. In the standby state, the temperature inside the alkaline electrolyzer is controlled within a set temperature range. Cold start state. In the cold start state, an external heating device is used to heat the alkaline electrolyzer. Hot start state. In the hot start state, the alkaline electrolyzer starts a hot start from the standby state.

2. The temperature control method of the alkaline electrolyzer according to claim 1, characterized in that, In the working state, the working temperature inside the alkaline electrolyzer is: where f(T) is a non-linear function related to temperature, and u is a control quantity related to the flow rate of the circulating alkaline solution.

3. The method for controlling the temperature of an alkaline electrolyzer according to claim 2, wherein The control quantity u related to the flow rate of the circulating alkaline solution is obtained by the following method: Introduce the error variable e = T of the alkaline electrolyzer temperature and the preset temperature d -T, taking the derivative of e gives f(T) has upper and lower limits, that is |f(T)| < ρ To achieve e → 0, the control quantity u related to the flow rate of the circulating alkaline solution is set as 4. The temperature control method of the alkaline electrolyzer according to claim 1, characterized in that, In the standby state, the in-built resistance heating element or heat storage device of the alkaline electrolyzer is used to keep the electrolyte warm, so that the temperature inside the alkaline electrolyzer is controlled within the set range; in the standby state, the heat preservation power is 8% of the rated power.

5. The method for controlling the temperature of an alkaline electrolyzer according to claim 1, wherein, In the cold start state, an external heating device is used to heat the electrolyzer, and the heating power is 15% of the rated power.

6. The temperature control method of the alkaline electrolyzer according to claim 1, wherein In the working state, the temperature inside the alkaline electrolyzer is maintained at a stable working temperature level through a second-class absorption heat pump and a circulating water network.

7. The method for controlling the temperature of an alkaline electrolyzer according to claim 1, wherein The method further includes: constructing a dynamic model of the electrochemistry and heat conduction of the alkaline electrolyzer, taking the flow rate of the circulating alkaline solution as the control object, constructing a control law for temperature control, obtaining the alkaline solution flow rate based on the control law, and adjusting the alkaline solution flow rate by detecting the alkaline solution temperature at the outlet.

8. The method for controlling the temperature of an alkaline electrolyzer according to claim 2, wherein The working temperature inside the alkaline electrolyzer is obtained by the following method: The electrochemistry working process of the alkaline electrolyzer is modeled as: where U cell and U rev are the terminal voltage and the reversible voltage of the electrolysis chamber respectively; r 1，2 is the ohmic resistance parameter of the electrolyte; A is the area of the electrolysis module; I is the current of the electrolytic cell; s 1,2,3 is the overvoltage coefficient; t 1,2,3 is the overvoltage coefficient; T el is the temperature of the electrolyte; The overvoltage η is used to characterize the sum of the polarization voltage and the ohmic loss voltage, that is U cell = U rev + η The calculation formula for the heat conduction of the electrolyzer is: Among them, U th is the thermoneutral voltage; Q el is the heat dissipation of the AWE electrolyzer; C p,KOH is the specific heat capacity corresponding to the average temperature when the caustic solution flows out and into the electrolyzer; V KOH is the flow rate of the caustic solution flowing out of the electrolyzer; ρ KOH is the density corresponding to the average temperature when the lye flows out and into the electrolytic cell; T H0 is the temperature when the lye flows out of the electrolytic cell; T Hr is the temperature when the lye just flows into the electrolytic cell; m O2 is the mass flow rate of oxygen at the outlet of the electrolytic cell; m H2 is the mass flow rate of hydrogen at the outlet of the electrolytic cell; h O2 、h H2 are the enthalpy values of oxygen and hydrogen at the outlet of the electrolytic cell respectively; R t is the thermal resistance; T a is the ambient temperature; According to the above equations, the working temperature inside the alkaline electrolyzer is

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