Solar STEP Coal Conversion:Construction And Process Via Solar-Driven Thermal And Electrochemistry

With the outbreak of the energy crisis,it is realized that the over-dependence of traditional fossil energy could lead unpredictable obstacles to the development of human beings.Furthermore,the over excessive exploitation and utilization of fossil fuels caused more and more serious environmental problems.The explortation of new energy is extremely urgent.At present,the most popular new energy is solar energy.Currently,the solar applications are most extensively focused on the solar to heat and electricity such as solar heater,solar refrigeration and solar to power.The solar energy gaines a low efficiency and big influence by the surrounding environment which limited the development of solar energy.The solar STEP(Soalr Thermal Electrochemical Process)novely couples the photo-thermal,photo-electro and photho-chemical process to drive different chemical reactions,aiming to gain efficient ultilization of solar energy.In the paper,the theory foundation of STEP combined with the transformation of traditional fossil fuels was proposed to drive the clean renewable transformation process of coal with the heat and electricity from the STEP process.The combination of solar energy and fossil fuel could realize the conversion and storage of solar energy,also the clean transformation of fossil fuel.The theory fourndation of solar STEP coal conversion process was mainly studied for leading to the research of solar STEP coal cleaning process and solar STEP coal conversion process.Based on the experiments data,the calculation efficiency of solar transformation and STEP coal conversion were done to set up STEP coal clean conversion system with the rational design and description for providing the theoretical basis and technical reference.The main contents are as follows:(1)The theoretical and experimental model of solar STEP coal conversion were proposed and set up,and the theoretical analysis of the process was done.Based on the thermodynamic analysis and the electrochemical reaction model,the STEP coal conversion process can be realized the utilization of solar energy and clean coal conversion.(2)The clean coal desulfurization was driven with solar photo-thermal and photo-electro process from STEP.In the experiments,the nickle was used as working electrode.The electrochemical experiments were done under different temperature zones to gain the desulfurization rate.Furthermore,the mechanism of STEP clean coal desulfurization was studied.The results showed that the desulfurization rate increased with the temperature and got the highest in high temperature zone under the same working potential.The desulfurization of inorganic sulfur have already got the ideal rate in low temperature zone,however,for the desulfurization of organic sulfur,much more higher temperatures were required to achieve the desired efficiency.According to the experimental results,the rate of total desulfurization was 40% in low temperature zone,the rate of total desulfurization was 58% in middle temperature zone and the rate of total desulfurization was 77% in high temperature zone under 2V for 4 hours.The desulfurization of inorganic sulfur achieved 72% in low temperature zone with a low rate of organic sulfur which got 50% in high temperature zone.The recovery of coal also showed that the desulfurization of coal under middle and high temperature zone proceed with the oxidation of coal,the higher temperature leading to less coal residues.So,the high temperature themal electrochemical process driven by STEP could remove the sulfur efficiently,moreover,it could realize the green conversion of coal to high-quality energy.(3)Based on the desulfurization of coal under high temperature zone,the process of coal conversion driven by solar STEP was intensive studied.The thermal electrochemical oxidation of coal could achieve in molten NaOH driven by STEP which with the temperature was lower than the traditional coal conversion process.And the product contained small molecule gas,such as hydrogen,methane and various liquid products.The high conversion of STEP coal conversion is 87.3% with the current of 0.4 A at 360℃ in 4 hours.The gasification rate goes to 38.5% and the liquefaction rate goes to 48.8%.In this paper,the mechanism of coal conversion process with electrochemical reactions at high temperature was studied.According to the analysis of the physical structure model and the oxidation process of coal,in the high temperature electrochemical process,the coal absorbed the heat from STEP which make the small molecule escaped from the non covalent bond and destroyed the covalent bond of big molecule.The steady structure of big molecules were destroyed by the high temperature electrochemical reactions to achieve the goal of deep oxidize the coal.(4)According to the high temperature electrochemical oxidation and desulfurization reactions driven by STEP,the STEP clean coal conversion process was set up and the efficiency of the system was calculated.The solar conversion efficiency was 17% and the efficiency of solar to chemical energy was 11.86%.The solar conversion unit and solar to chemical energy conversion unit were set up and combined.In summary,a flow diagram was designed and described to help the following process design and experimental amplification.