Method for efficiently desulfurizing and producing hydrogen based on solar STEP thermal-electrochemical coupling
阅读说明：本技术 一种基于太阳能step热-电化学耦合高效脱硫并制氢气的方法 (Method for efficiently desulfurizing and producing hydrogen based on solar STEP thermal-electrochemical coupling ) 是由 朱凌岳 苑丹丹 纪德强 闫超 江弘 吴红军 王宝辉 于 2019-11-28 设计创作，主要内容包括：本发明涉及一种基于太阳能STEP热-电化学耦合高效脱硫并制氢气的方法。该方法包括如下步骤：(1)对煤炭进行预处理,获得煤粉；(2)将煤粉和固态电解质混合后形成的固态材料置于密闭的电解装置内；和(3)在320-380℃和1.8-3.0V下对固态材料电解4-8h,通过太阳能集热装置提供电解所需的热能,通过光伏电池提供电解所需的电能。本发明首次提出了一种基于太阳能STEP热-电化学耦合高效脱硫并制氢气方法,方法所需的能量全部来源于太阳能,过程中不需要添加任何额外的能量。(The invention relates to a method for efficiently desulfurizing and producing hydrogen based on solar STEP thermal-electrochemical coupling. The method comprises the following steps: (1) pretreating coal to obtain coal powder; (2) placing a solid material formed by mixing the coal powder and the solid electrolyte in a closed electrolysis device; and (3) electrolyzing the solid material at the temperature of 320-380 ℃ and the voltage of 1.8-3.0V for 4-8h, providing the heat energy required by electrolysis through a solar heat collecting device, and providing the electric energy required by electrolysis through a photovoltaic cell. The invention provides a method for efficiently desulfurizing and producing hydrogen based on solar STEP thermal-electrochemical coupling for the first time, the energy required by the method is all from solar energy, and no additional energy is required to be added in the process.)
1. A method for efficient desulfurization and hydrogen production based on solar STEP thermal-electrochemical coupling is characterized by comprising the following STEPs:
(1) pretreating coal to obtain coal powder;
(2) placing a solid material formed by mixing the coal powder and the solid electrolyte in a closed electrolysis device; and
(3) the solid material is electrolyzed for 4-8h at the temperature of 320-380 ℃ and the voltage of 1.8-3.0V, the heat energy required by the electrolysis is provided by the solar heat collection device, and the electric energy required by the electrolysis is provided by the photovoltaic cell.
2. The method of claim 1,
the electrolysis was carried out at 380 ℃ and 3.0V for 8 h.
3. The method of claim 1,
the solid electrolyte is powdered sodium hydroxide.
4. The method according to any one of claims 1 to 3,
the mass ratio of the pulverized coal to the solid electrolyte is 1: (10-15), preferably 1: 10.
5. The method according to any one of claims 1 to 4,
the electrolysis adopts a double-electrode system, and the electrodes are all nickel electrodes.
6. The method according to any one of claims 1 to 5,
the solar heat collecting device is a focusing solar heat collector; and
the solar photoelectric conversion device is a polycrystalline silicon photovoltaic cell.
7. The method of claim 6,
and during the electrolysis, the voltage output by the solar photoelectric conversion device is regulated by the voltage stabilizer.
8. The method of claim 6,
the thermal energy provided by the solar thermal collection device is regulated by a temperature controller equipped with a thermocouple.
9. The method according to any one of claims 1 to 8,
the pretreatment comprises the following steps:
(a) crushing coal;
(b) screening the crushed coal;
(c) drying the screened coal; and
(d) and (4) performing deliming treatment on the dried coal.
10. The method of claim 9,
sieving coal below 120 meshes;
drying the screened coal at 40-60 ℃ for 20-24 hours; and/or
The deashing treatment is carried out according to the following method: soaking the dried coal with absolute ethyl alcohol, adding 40% hydrofluoric acid solution, and placing the mixed material in a water bath device at 50-60 deg.C while heating and stirring; filtering the obtained material, cooling, adding 50% hydrochloric acid solution, stirring, filtering, washing and drying in sequence.
Technical Field
The invention relates to the technical field of coal treatment, in particular to a method for efficiently desulfurizing and producing hydrogen based on solar STEP thermal-electrochemical coupling.
Background
Coal accounts for about 70% of the energy consumption structure in China, and is an important guarantee for the sustainable and rapid development of economy. However, sulfur in coal generates SO during combustion and coking2Causing serious air pollution and causing a series of environmental problems. Therefore, coal desulfurization has important significance for improving the utilization efficiency of coal resources and protecting the environment. Sulfur in coal can be classified into inorganic sulfur and organic sulfur according to the presence state. Inorganic sulfur in coal can be removed by physical methods such as gravity separation and flotation, but the physical method can only remove part of pyrite, and is not applicable to the removal of inorganic mineral substances such as sulfate embedded in fine particles. Organic sulfur removal is difficult and usually employs chemical methods such as thermocaustic leaching and oxidation, which generally require strong acid/base or high pressure reaction, and may reduce the cohesiveness, expansion and calorific value of the coal. The microbial desulfurization has low energy consumption and no influence on coal quality, but the existing desulfurization strain is single, the production period is long, the equipment investment is high, the variation of the microorganisms cannot be avoided, and the desulfurization process is not mature and is only suitable for removing the micro-fine-particle pyrite.
The electrochemical desulfurization technology is a mild desulfurization method which is carried out at lower temperature and normal pressure, the process is easy to realize, and the equipment required in industry is simple. This technology has been proposed as early as the sixties, and a great deal of research has been conducted on this technology after the seventies. Many scientists in foreign countries have carried out a lot of experiments on H-shaped electrolytic cells with diaphragms, fluidized bed electrolytic cells, electrolysis under alkaline conditions, electrolysis under acidic conditions and the like, but in the research process, the problems that the electrochemical desulfurization technology still has many problems and the investment of the electrolytic cells is too large still troubles researchers. The research of China on electrochemical desulfurization starts late, and in recent years, the research on a diaphragm-free electrolytic cell can remove more than 70% of inorganic sulfur and remove up to 60% of organic sulfur under a mild electrolysis condition, but the main problems of high cost and high energy consumption still cannot be fundamentally solved, and the research on the mechanism of electrochemical desulfurization is not carried out.
Solar energy is one of the most safe, greenest and ideal alternative energy sources. The total amount of solar energy resources is huge, the radiation range is wide, the use process is clean, and the problem of resource exhaustion does not exist.
At present, no relevant report of efficiently removing sulfur in coal by using solar energy is found.
Disclosure of Invention
The invention aims to provide a method for efficiently desulfurizing and producing hydrogen based on solar STEP thermal-electrochemical coupling.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for efficient desulfurization and hydrogen production based on solar STEP thermal-electrochemical coupling comprises the following STEPs:
(1) pretreating coal to obtain coal powder;
(2) placing a solid material formed by mixing the coal powder and the solid electrolyte in a closed electrolysis device; and
(3) the solid material is electrolyzed for 4-8h at the temperature of 320-380 ℃ and the voltage of 1.8-3.0V, the heat energy required by the electrolysis is provided by the solar heat collection device, and the electric energy required by the electrolysis is provided by the photovoltaic cell.
Preferably, the electrolysis is carried out at 380 ℃ and 3.0V for 8 h.
Preferably, the solid electrolyte is powdered sodium hydroxide.
Preferably, the mass ratio of the pulverized coal to the solid electrolyte is 1: (10-15), preferably 1: 10.
Preferably, the electrolysis employs a two-electrode system, the electrodes all being nickel electrodes.
Preferably, the solar heat collecting device is a focusing solar heat collector; and
the solar photoelectric conversion device is a polycrystalline silicon photovoltaic cell.
Preferably, during the electrolysis, the voltage output by the solar photoelectric conversion device is regulated by a voltage stabilizer.
The thermal energy provided by the solar thermal collector is preferably regulated by a temperature control instrument equipped with a thermocouple.
Preferably, the pre-treatment comprises:
(a) crushing coal;
(b) screening the crushed coal;
(c) drying the screened coal; and
(d) and (4) performing deliming treatment on the dried coal.
Preferably, the coal below 120 meshes is screened out by screening;
drying the screened coal at 40-60 ℃ for 20-24 hours; and/or
The deashing treatment is carried out according to the following method: soaking the dried coal with absolute ethyl alcohol, adding 40% hydrofluoric acid solution, and placing the mixed material in a water bath device at 50-60 deg.C while heating and stirring; filtering the obtained material, cooling, adding 50% hydrochloric acid solution, stirring, filtering, washing and drying in sequence.
Advantageous effects
The technical scheme of the invention has the following advantages:
the invention provides a method for removing organic sulfur and inorganic sulfur in coal based on solar STEP thermal-electrochemical coupling for the first time, which simultaneously utilizes solar photo-thermal and solar photo-electric processes to drive the organic sulfur and inorganic sulfur in the coal to be converted into stable sulfate radicals so as to achieve the aim of purifying the coal, and can obtain an ideal additional product of hydrogen with certain economic value.
The energy (including heat energy and electric energy) required by the method provided by the invention is completely derived from solar energy, the heat energy required by the method is provided by a solar heat collecting device, the electric energy required by the method is provided by a solar photoelectric conversion device, and no additional energy is required to be added in the process.
The invention provides necessary heat energy for removing dibenzothiophene in coal by utilizing the light-heat effect in the long wavelength region, and provides necessary electric energy for removing dibenzothiophene in coal by utilizing the visible light region, thereby obviously improving the utilization rate of sunlight and realizing full-band utilization of sunlight.
The method provided by the invention has no problem of secondary pollution.
Drawings
FIG. 1 is a schematic diagram of desulfurization of dibenzothiophene by conventional electrochemical methods;
FIG. 2 is a schematic diagram of the desulfurization of dibenzothiophenes by the process of the present invention;
FIG. 3 is the desulfurization rates at different temperatures; temperature on the abscissa means Temperature (. degree. C.), and desulfurization rate on the ordinate means percent (%) of sulfur removal;
FIG. 4 is a graph showing the change in desulfurization rate under various electrolysis potential conditions; the abscissa Potential means the electrolytic Potential (V) and the ordinate desulfurization rate means the desulfurization (%);
FIG. 5 is a graph of hydrogen production versus desulfurization for different electrolysis potential conditions; the abscissa Potential means the electrolytic Potential (V), the left ordinate desulfation rate means the desulfurization rate (%), and the right ordinate Hydrogen generation means the Hydrogen production (ml);
FIG. 6 is a graph showing the change of desulfurization rate with time at 320 ℃; the abscissa Time means Time (h), and the left ordinate desulfurization rate means desulfurization (%).
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The invention provides a method for desulfurizing and producing hydrogen based on solar STEP thermal-electrochemical coupling for the first time. The method simultaneously utilizes the solar photo-thermal and solar photo-electric processes to drive organic sulfur and inorganic sulfur in the coal to be converted into stable sulfate radicals so as to achieve the aim of purifying the coal, and can also obtain an ideal additional product of hydrogen with certain economic value; the energy (including heat energy and electric energy) required by desulfurization in the method is completely derived from solar energy, the heat energy required by the method is provided by a solar heat collection device, the electric energy required by the method is provided by a solar photoelectric conversion device, and no extra energy is required to be added in the process; the invention provides necessary heat energy for removing organic sulfur in coal by utilizing the photo-thermal effect of a long wavelength region, and provides necessary electric energy for removing organic sulfur in coal by utilizing a visible light region, thereby obviously improving the utilization rate of sunlight and realizing full-wave-band utilization of the sunlight; the method has no secondary pollution problem. Specifically, the method provided by the invention comprises the following steps:
(1) pretreating coal to obtain coal powder;
(2) placing a solid material formed by mixing the coal powder and the solid electrolyte in a closed electrolysis device; and
(3) the solid material is electrolyzed for 4-8h at the temperature of 320-380 ℃ and the voltage of 1.8-3.0V, the heat energy required by the electrolysis is provided by the solar heat collection device, and the electric energy required by the electrolysis is provided by the photovoltaic cell.
Conventional electrochemical desulfurization processes are typically carried out at low temperatures below 100 ℃. The inventors have found in their studies that organic sulfur at low temperatures and the total sulfur removal effect are not ideal and almost no organic sulfur can be removed. The desulfurization method provided by the invention is carried out at the temperature of 320-380 ℃, the temperature region fully utilizes the photothermal effect of solar energy, and the thermal effect is most obvious. In addition, the energy required by the method provided by the invention is all from solar energy, so that the method has no concern of high energy consumption. Considering the instability and uncertainty of the coal quality change and the high temperature reaction, the present invention determines the temperature condition as 320-.
The invention improves the desulfurization effect by strengthening the action of the electric field on the basis of the action of the thermal field. The inventor finds in research that inorganic sulfur and organic sulfur need different electrolytic potentials when undergoing electrochemical reaction, and the electrolytic potential for electrochemical oxidation of organic sulfur is higher than that of inorganic sulfur. At lower potentials, mainly inorganic sulfur is removed, the removal rate of inorganic sulfur increases faster than organic sulfur, while at higher potentials, the opposite rule is followed, the removal rate of organic sulfur increases faster than inorganic sulfur. But the removal effect of either organic, inorganic or total sulfur increases with increasing electrolysis potential. However, an excessively high electrolytic potential increases the oxidation rate of the electrode, the electrode efficiency gradually decreases during a long reaction time, and the desulfurization rate of coal is affected, and the oxidation reaction is too active at an excessively high temperature and is difficult to control, and the influence on the quality of coal is difficult to avoid. Based on the above, the present invention determines the electrolysis voltage condition to be 1.8 to 3.0V, for example, 1.8V, 2.0V, 3.0V, without continuing to raise the electrolysis potential.
The following is the desulfurization mechanism of the process provided by the present invention:
the solar STEP thermal-electrochemical coupling coal conversion desulfurization process is a complex high-temperature electrochemical oxidation reaction process, the exploration of the desulfurization mechanism can effectively help people to understand how the desulfurization process occurs, the desulfurization process can be strengthened and adjusted according to the mechanism, and the efficiency and the selectivity of the desulfurization reaction process are improved.
Generally, the sulfur contained in coal exists mainly in two forms of inorganic sulfur and organic sulfur, wherein the inorganic sulfur mainly includes pyrite sulfur and sulfate sulfur, the sulfate sulfur mainly exists in stable sulfate radical and can not be further oxidized, and the sulfate is easy to dissolve in aqueous solution, so the sulfate sulfur is easier to be removed than the pyrite sulfur. The removal of inorganic sulfur is mainly focused on the removal of pyrite sulfur.
Taking the removal of sulfur from pyrite as an example, the electrochemical reaction can be expressed as:
anode:
4OH-→O2+H2O+4e
FeS2+OH-+O2→Fe(OH)3+SO4 2-+H2O
FeS2+14Fe3++8H2O→15Fe2++16H++2SO4 2-
cathode:
2H2O+2e-→H2+2OH-。
the molten alkali electrolyte provides more active free radicals for electrochemical reaction, divalent iron ions are oxidized into trivalent iron ions in the reaction process, the trivalent iron ions react with pyrite to be reduced into divalent iron ions, the chemical cycle is relative to the iron ions, the iron ions are equivalent to the role of a catalyst in the reaction process, and the sulfur in the pyrite is continuously consumed and converted into sulfate radicals to be removed. In the initial stage of the reaction, a uniform electrolyte is wrapped around the pyrite, the pyrite undergoes an electrochemical reaction with the progress of the reaction, the particles of the pyrite gradually become smaller, the concentration of the electrolyte around the pyrite also decreases, the generated products such as sulfate radicals and ferric ions diffuse into the electrolyte, active groups generated by the anode are adsorbed by the pyrite particles, the oxidation of sulfur in the pyrite is promoted, the pyrite particles gradually become smaller, and the pyrite further nucleates with the lapse of time until the pyrite completely reacts until the nuclei disappear. When the temperature rises, the process is influenced by the temperature, the reaction rate and the number of active free radicals are enhanced, and the adsorption speed of the pyrite on the active free radicals in the electrolyte and the desorption speed of generated substances are increased, so that the desulfurization rate of the pyrite is increased.
Organic sulfur is the most difficult moiety to remove, and is generally present in coal as a sulfur-containing functional group, with typical sulfur-containing functional groups being mercaptans, sulfides, disulfides, sulfide quinones, and heterocyclic sulfides. At higher reaction temperatures, thiol groups and disulfides are unstable and decompose during desulfurization, so that more stable thiophenes are used as model compounds in the process of discussing desulfurization mechanism of organic sulfur. The thiophene organic matters have stable structures, and can be condensed with organic matters into high-molecular sulfides even in the high-temperature carbonization process, wherein the organic matters which are most difficult to be oxidized in the thiophene organic matters are dibenzothiophene.
Taking desulfurization of dibenzothiophene as an example, as shown in fig. 1, the conventional electrochemical method for desulfurization of dibenzothiophene can be divided into five steps. The first step is that dibenzothiophene is primarily oxidized to increase one sulfur-oxygen double bond on sulfur, and two sulfur-oxygen double bonds are increased on sulfur along with the continuous oxidation, and the addition of the sulfur-oxygen bond reduces the bond energy of the original carbon-sulfur bond, so that the carbon-sulfur bond in the generated oxidation product becomes more unstable and is easy to break to generate phenylphenol sulfinic acid. The phenylphenol sulfinic acid is oxidized to generate sulfur dioxide and biphenyl.
It can be seen that dibenzothiophene is not sufficiently oxidized to form sulfur dioxide using conventional electrochemical methods. The release of sulphur dioxide gas is very harmful to the environment and to the reaction equipment, and conventional methods are not very desirable, if at all possible.
The inventors believe that the most important process in the oxidation of dibenzothiophenes is the primary oxidation of sulfur on the basis of the original thiophene structure, which breaks the original thiophene stable structure and makes it more susceptible to the cleavage of the C — S bond by oxidation. In the conventional electrochemical process at a lower temperature, the oxidation process is difficult to be completed at a lower voltage, and considering that the electrolyte is water, if an excessively high voltage is used in the electrochemical oxidation process, the water undergoes a rapid electrolytic reaction, which affects the effect of electrolytic oxidation.
The process of the invention is carried out at elevated temperature. In high temperature environment, the molecule of dibenzothiophene is heated and activated because the heat effect has taken place, makes dibenzothiophene be in the state of an excitation, and the molecule of excited state is more active has higher reactivity under this state, so originally need provide higher voltage just can be with the process of its oxidation, uses lower voltage alright realize under the supplementary of high temperature. Because more active factors can be formed on the surface of the anode in a high-temperature environment, and the molecular motion and the reaction rate are enhanced, the dibenzothiophene can be fully oxidized, so that the final oxidation product is not sulfur dioxide and biphenyl but sulfate and biphenyl.
FIG. 2 is a schematic diagram of desulfurization in the process of the present invention. As shown in figure 2, after two sulfur-oxygen bonds are added to dibenzothiophene, due to enough active factors in the system, sufficient oxidation can be achieved for dibenzothiophene, sulfite is generated instead of sulfur dioxide after generated phenylphenol sulfinic acid is broken, and sulfate is generated through further oxidation of sulfite. By verification, sulfur dioxide is not detected in the product of the invention, so that sulfur-containing organic matters with dibenzothiophene and similar structures can be judged to be fully oxidized in the oxidation process to generate sulfate radicals instead of sulfur dioxide.
In some preferred embodiments, the present invention provides a desulfurization method, wherein the electrolysis is performed at 380 ℃ and 3.0V for 8 hours, so that the best desulfurization effect and hydrogen yield can be obtained.
In some preferred embodiments, the solid electrolyte is powdered sodium hydroxide. Sodium hydroxide melts at 318 c and provides better conductivity.
In some preferred embodiments, the mass ratio of the pulverized coal to the solid electrolyte is 1: (10-15) may be, for example, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, most preferably 1: 10.
In some preferred embodiments, the electrolysis employs a two-electrode system, with both electrodes being nickel electrodes. In the electrochemical reaction process, the electrode is used as an important medium for generating the electrochemical reaction, the efficiency of the reaction process, the selectivity of products and the like are influenced and determined, and the selection of electrode materials is very important. In the process of converting the solar STEP coal, the reaction occurs in a high-temperature and high-corrosion environment for a long time, so that the selected electrode needs to be resistant to high temperature and corrosion within a long reaction time, have good physical and chemical stability in a high-temperature environment, and consider factors such as economic cost and industrial realization possibility. The nickel electrode has the advantages of smooth change of electrode potential along with current density, small degree of metal passivation, good electrochemical stability and certain rigidity and strength, so that the nickel electrode is adopted in the invention.
In some preferred embodiments, the solar heat collection device is a focused solar heat collector. In some preferred embodiments, the solar photovoltaic conversion device is a polycrystalline silicon photovoltaic cell. More preferably, during the electrolysis, the voltage output by the solar photoelectric conversion device is regulated by a voltage stabilizer; and/or the thermal energy provided by the solar thermal collection device is regulated by a temperature control instrument equipped with a thermocouple.
In some preferred embodiments, the pre-treatment comprises: (a) crushing coal; (b) screening the crushed coal; (c) drying the screened coal; and (d) subjecting the dried coal to deliming treatment. The coal powder has the appropriate maximum granularity, ash content, uniformity and the like through the pretreatment.
In the pretreatment provided by the present invention, coal is first pulverized to reduce the particle size of the coal and to increase the degree of divergence of the heterogeneous material to make its properties uniform. The crushing can be carried out by a sealed vibration crusher, and the coal is crushed for 1 hour, so that the coal sample is fully crushed. Then, the crushed coal is screened, the coal sample which is not sufficiently crushed and meets the requirement of granularity is screened out, and a sample with the granularity of less than 120 meshes is screened out by a screen. The screened coal sample is placed in a drying oven and dried at 40-60 deg.C (for example, 40 deg.C, 45 deg.C, 50 deg.C, 55 deg.C, 60 deg.C) for 20-24 hours (for example, 20 hours, 21 hours, 22 hours, 23 hours, 24 hours) to remove a large amount of water from the coal sample. And cooling the dried coal sample, and then performing coal sample deashing treatment. Because the collected coal sample contains a large amount of ash, the ash in the raw coal needs to be pretreated to remove a large amount of ash so as to prevent the ash from influencing the desulfurization conversion process of the coal in the experimental process. The deliming treatment can be carried out as follows: soaking dried coal in anhydrous ethanol, adding 40% hydrofluoric acid solution, and heating while stirring the mixture in a water bath device at 50-60 deg.C (such as 50 deg.C, 51 deg.C, 52 deg.C, 53 deg.C, 54 deg.C, 55 deg.C, 56 deg.C, 57 deg.C, 58 deg.C, 59 deg.C, 60 deg.C); filtering the obtained material, cooling, adding 50% hydrochloric acid solution, stirring, filtering, washing and drying in sequence.
More fully, the method provided by the invention comprises the following steps:
(1) pretreating coal to obtain coal powder;
the pretreatment comprises the following steps: (a) crushing coal; (b) screening the crushed coal, and screening the coal with a particle size of less than 120 meshes; (c) drying the screened coal at 40-60 ℃ for 20-24 hours; and (d) subjecting the dried coal to deliming treatment. The deashing treatment is carried out according to the following method: soaking the dried coal with absolute ethyl alcohol, adding 40% hydrofluoric acid solution, and placing the mixed material in a water bath device at 50-60 deg.C while heating and stirring; filtering and cooling the obtained material, adding 50% hydrochloric acid solution, and sequentially stirring, filtering, washing and drying;
(2) putting a solid material formed by mixing coal powder and a solid electrolyte into a closed electrolysis device; the solid electrolyte is powdery sodium hydroxide; the mass ratio of the pulverized coal to the solid electrolyte is 1: (10-15), preferably 1: 10;
(3) electrolyzing the solid material in the step (2) at the temperature of 320-380 ℃ and the voltage of 1.8-3.0V for 4-8h, providing the temperature condition required by electrolysis through a solar heat collecting device, and providing the voltage condition required by electrolysis through a solar photoelectric conversion device; preferably, the electrolysis is carried out at 380 ℃ and 3.0V for 8 h; a double-electrode system is adopted for electrolysis, and electrodes are nickel electrodes; the solar heat collecting device is a focusing solar heat collector; the solar photoelectric conversion device is a polycrystalline silicon photovoltaic cell; during the electrolysis, the voltage output by the solar photoelectric conversion device is regulated by the voltage stabilizer; the thermal energy provided by the solar thermal collection device is regulated by a temperature controller equipped with a thermocouple.
The following are examples of the present invention.