Supercritical water gasification is a clean technology for biomass conversion and utilization.In supercritical water gasification systems,H_(2)O is often used as the transport medium.Decreases in the reaction temperat...Supercritical water gasification is a clean technology for biomass conversion and utilization.In supercritical water gasification systems,H_(2)O is often used as the transport medium.Decreases in the reaction temperature at the gasification area and in the heating rate of biomass may limit the gasification rate and efficiency.In this paper,CO_(2)is used as the transport medium due to its relatively low critical point and specific heat capacity.Moreover,a corn stalk gasification system with different transport media is established in this paper,and the influences of various operating parameters,such as temperature,pressure and feedstock concentration,are investigated.The results show that the gas yield in the CO_(2)-transport system decreases by no more than 5 wt%.In addition,thermodynamic analysis reveals that a system with CO_(2)as transport medium consumes approximately 25%less electricity than a system with H_(2)O as the transport medium.In addition,the reaction heat absorption decreases.The results show the superiority of CO_(2)to H_(2)O as a transport medium.展开更多
The rising production of sewage sludge,characterized by high organic content and excessive heavy metals,necessitates an effective treatment method.This study investigated the production of syngas and the migration and...The rising production of sewage sludge,characterized by high organic content and excessive heavy metals,necessitates an effective treatment method.This study investigated the production of syngas and the migration and transformation behavior of heavy metals such as Zn,Ni,Cr,Cu,and As during supercritical water gasification(SCWG)of sewage sludge.The experiments were conducted without or with alkaline additives at temperatures between 380 to 420℃ and retention time from 15 to 60 min.The results revealed that the highest syngas yield reached 10.9 mol/kg with an H2 concentration of 44.7% at 420℃ and 60 min.In this process,heavy metals were effectively immobilized and converted into a more stable form,whereas higher temperatures and longer retention time enhanced this effect.The introduction of alkaline additives(NaOH,KOH,Ca(OH)_(2),Na_(2)CO_(3),and K_(2)CO_(3))led to the redistribution of heavy metals,further promoting the stabilization of Zn,Cr,and Cu.An environmental risk assessment showed that SCWG could significantly lower the risk associated with heavy metals to a low or negligible level.展开更多
A new cleaner power generation system(IPGS) is proposed and investigated in this paper. Integrating combined cycle with supercritical water gasification of coal, the thermodynamic energy of the produced syngas is casc...A new cleaner power generation system(IPGS) is proposed and investigated in this paper. Integrating combined cycle with supercritical water gasification of coal, the thermodynamic energy of the produced syngas is cascade utilized according to its temperature and pressure, both sensible and latent heat of the syngas can be recycled into the system, and thereby the net power efficiency can be about 6.4 percentage points higher than that of the traditional GE gasification based power plant(GEPP). The exergy analysis results show that the exergy efficiency of the proposed system reaches 52.45%, which is 13.94% higher than that of the GEPP, and the improvement in exergy efficiency of the proposed system mainly comes from the exergy destruction decline in the syngas energy recovery process, the condensation process and the syngas purification process. The syngas combustion process is the highest exergy destruction process with a value of 157.84 MW in the proposed system. Further performance improvement of the proposed system lies in the utilization process of syngas. Furthermore, system operation parameters have been examined on the coal mass fraction in the supercritical water gasifier(GF), the gasification temperature, and the gasification pressure. The parametric analysis shows that changes in coal concentration in the GF exert more influence on the exergy efficiency of the system compared with the other two parameters.展开更多
As a benign energy vector,hydrogen has been discussed for a long time.Supercritical water gasification was one of good ways to produce hydrogen.However,supercritical water gasification system with H_(2)O transporting ...As a benign energy vector,hydrogen has been discussed for a long time.Supercritical water gasification was one of good ways to produce hydrogen.However,supercritical water gasification system with H_(2)O transporting was energy consuming in the process of heating due to the high specific heat of H_(2)O.A new supercritical water gasification system was established in this paper with supercritical CO_(2)as medium instead.Phenolic plastics were used as the sample transported by CO_(2).Production yields,energy flow and exergy flow of the system were collected and the influence of temperature,pressure,gasification concentration and transporting concentration was investigated.Mass flow of H_(2)O input into the reactor was 1000 kg/h.The typical condition was as follow:temperature 923.15 K,pressure 23 MPa,and the mass ratio of water,sample and transporting medium was 100:9:9.Yield of H_(2),CH4,CO and CO_(2)at this condition was 8.1 kg/h,39.6 kg/h,6.6 kg/h and 137.5 kg/h,respectively.Similar system with H_(2)O transporting was used to compare with the supercritical CO_(2)transporting system and proved that system with CO_(2)transporting could reduce the loss of both energy and exergy while the reduce of each gas production yield was less than 0.1 mol/mol.展开更多
Wastewater from the thermochemical conversion of coal and biomass contains a significant amount of phenolic structures compounds.The degradation of these phenolic compounds to hydrogen-rich gasses can prevent envi-ron...Wastewater from the thermochemical conversion of coal and biomass contains a significant amount of phenolic structures compounds.The degradation of these phenolic compounds to hydrogen-rich gasses can prevent envi-ronmental pollution and save energy.Supercritical water(SCW)gasification of phenol is experimentally studied and a reactive force field molecular dynamics(ReaxFF-MD)simulation is conducted to investigate the catalytic mechanism of Ni/Al2 O3 in the phenol degradation.The experimental results indicate that Ni/Al2 O3 facilitates the conversion of phenol to 1-ethoxy butane via ring opening,which is a crucial step for complete gasification.The ReaxFF-MD simulation demonstrated that Ni facilitates the formation of H3 O free radicals and Ni-phenol inter-mediates.H3 O free radicals can be decomposed into H2 and OH free radicals.Both the generated OH free radical and Ni-phenol intermediate promote the ring-opening reaction of phenol.Ni promotes the direct decomposition of phenol into C1,C2,and C3 fragments,which is beneficial for further complete gasification.展开更多
Energy conversion and utilization, particularly carbon-based fuel burning in air phase, have caused great environmental pollution and serious problems to society. The reactions in water phase may have the potential to...Energy conversion and utilization, particularly carbon-based fuel burning in air phase, have caused great environmental pollution and serious problems to society. The reactions in water phase may have the potential to realize clean and efficient energy conversion and utilization. Coal gasification in supercritical water is a typical carbon-based fuel conversion process in water phase, and it takes the advantages of the unique chemical and physical properties of supercritical water to convert organic matter in coal to H2 and CO2. N, S, P, Hg and other elements are deposited as inorganic salts to avoid pollution emission. The State Key Laboratory of Multiphase Flow in Power Engineering has obtained extensive experimental and theoretical results based on coal gasification in supercritical water. Supercritical water fluidized bed reactor was developed for coal gasification and seven kinds of typical feedstock were selected. The hydrogen yield covers from 0.67 to 1.74 Nm3/kg and the carbon gasification efficiency is no less than 97%. This technology has a bright future in industrialization not only in electricity generation but also in hydrogen production and high value-added chemicals. Given the gas yield obtained in laboratory-scale unit, the hydrogen production cost is U.S.$ 0.111 Nm3 when the throughput capacity is 2000 t/d. A novel thermodynamic cycle power generation system based on coal gasification in supercritical water was proposed with the obvious advantages of high coal-electricity conversion efficiency and zero pollutant emission. The cost of U.S.$ 3.69 billion for desulfuration, denitration and dust removal in China in 2013 would have been saved with this technology. Five kinds of heat supply methods are analyzed and the rates of return of investment are roughly estimated. An integrated cooperative innovation center called a new type of high-efficient coal gasification technology and its large-scale utilization was founded to enhance the industrialization of the technology vigorously.展开更多
Coal consumption leads to over 15 billion tons of global CO_(2) emissions annually,which will continue at a considerable intensity in the foreseeable future.To remove the huge amount of CO_(2),a practically feasible w...Coal consumption leads to over 15 billion tons of global CO_(2) emissions annually,which will continue at a considerable intensity in the foreseeable future.To remove the huge amount of CO_(2),a practically feasible way of direct carbon mitigation,instead of capturing that from dilute tail gases,should be developed;as intended,we developed two innovative supporting technologies,of which the status,strengths,applications,and perspective are discussed in this paper.One is supercritical water gasification-based coal/biomass utilization technology,which orderly converts chemical energy of coal and low-grade heat into hydrogen energy,and can achieve poly-generation of steam,heat,hydrogen,power,pure CO_(2),and minerals.The other one is the renewables-powered CO_(2) reduction techniques,which uses CO_(2) as the resource for carbon-based fuel production.When combining the above two technical loops,one can achieve a full resource utilization and zero CO_(2) emission,making it a practically feasible way for China and global countries to achieve carbon neutrality while creating substantial domestic benefits of economic growth,competitiveness,well-beings,and new industries.展开更多
基金National Key R&D Program of China(Grant No.2020YFA0714400).
文摘Supercritical water gasification is a clean technology for biomass conversion and utilization.In supercritical water gasification systems,H_(2)O is often used as the transport medium.Decreases in the reaction temperature at the gasification area and in the heating rate of biomass may limit the gasification rate and efficiency.In this paper,CO_(2)is used as the transport medium due to its relatively low critical point and specific heat capacity.Moreover,a corn stalk gasification system with different transport media is established in this paper,and the influences of various operating parameters,such as temperature,pressure and feedstock concentration,are investigated.The results show that the gas yield in the CO_(2)-transport system decreases by no more than 5 wt%.In addition,thermodynamic analysis reveals that a system with CO_(2)as transport medium consumes approximately 25%less electricity than a system with H_(2)O as the transport medium.In addition,the reaction heat absorption decreases.The results show the superiority of CO_(2)to H_(2)O as a transport medium.
基金the financial support from the National Natural Science Foundation of China(No.52250410339)the“Pioneer”and“Leading Goose”R&D Program of Zhejiang(China)(No.2024C03129).
文摘The rising production of sewage sludge,characterized by high organic content and excessive heavy metals,necessitates an effective treatment method.This study investigated the production of syngas and the migration and transformation behavior of heavy metals such as Zn,Ni,Cr,Cu,and As during supercritical water gasification(SCWG)of sewage sludge.The experiments were conducted without or with alkaline additives at temperatures between 380 to 420℃ and retention time from 15 to 60 min.The results revealed that the highest syngas yield reached 10.9 mol/kg with an H2 concentration of 44.7% at 420℃ and 60 min.In this process,heavy metals were effectively immobilized and converted into a more stable form,whereas higher temperatures and longer retention time enhanced this effect.The introduction of alkaline additives(NaOH,KOH,Ca(OH)_(2),Na_(2)CO_(3),and K_(2)CO_(3))led to the redistribution of heavy metals,further promoting the stabilization of Zn,Cr,and Cu.An environmental risk assessment showed that SCWG could significantly lower the risk associated with heavy metals to a low or negligible level.
基金the financial support of the National Key Research and Development Program of China(Grant No.2016YFB0600105)。
文摘A new cleaner power generation system(IPGS) is proposed and investigated in this paper. Integrating combined cycle with supercritical water gasification of coal, the thermodynamic energy of the produced syngas is cascade utilized according to its temperature and pressure, both sensible and latent heat of the syngas can be recycled into the system, and thereby the net power efficiency can be about 6.4 percentage points higher than that of the traditional GE gasification based power plant(GEPP). The exergy analysis results show that the exergy efficiency of the proposed system reaches 52.45%, which is 13.94% higher than that of the GEPP, and the improvement in exergy efficiency of the proposed system mainly comes from the exergy destruction decline in the syngas energy recovery process, the condensation process and the syngas purification process. The syngas combustion process is the highest exergy destruction process with a value of 157.84 MW in the proposed system. Further performance improvement of the proposed system lies in the utilization process of syngas. Furthermore, system operation parameters have been examined on the coal mass fraction in the supercritical water gasifier(GF), the gasification temperature, and the gasification pressure. The parametric analysis shows that changes in coal concentration in the GF exert more influence on the exergy efficiency of the system compared with the other two parameters.
基金This work is supported by the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China(No.51888103).
文摘As a benign energy vector,hydrogen has been discussed for a long time.Supercritical water gasification was one of good ways to produce hydrogen.However,supercritical water gasification system with H_(2)O transporting was energy consuming in the process of heating due to the high specific heat of H_(2)O.A new supercritical water gasification system was established in this paper with supercritical CO_(2)as medium instead.Phenolic plastics were used as the sample transported by CO_(2).Production yields,energy flow and exergy flow of the system were collected and the influence of temperature,pressure,gasification concentration and transporting concentration was investigated.Mass flow of H_(2)O input into the reactor was 1000 kg/h.The typical condition was as follow:temperature 923.15 K,pressure 23 MPa,and the mass ratio of water,sample and transporting medium was 100:9:9.Yield of H_(2),CH4,CO and CO_(2)at this condition was 8.1 kg/h,39.6 kg/h,6.6 kg/h and 137.5 kg/h,respectively.Similar system with H_(2)O transporting was used to compare with the supercritical CO_(2)transporting system and proved that system with CO_(2)transporting could reduce the loss of both energy and exergy while the reduce of each gas production yield was less than 0.1 mol/mol.
基金supported by the National Natural Science Founda-tion of China(Grant Nos.:51976046 and 52006044)the Shenzhen Technology Project(Grant No.:RCJC20210609103755110).
文摘Wastewater from the thermochemical conversion of coal and biomass contains a significant amount of phenolic structures compounds.The degradation of these phenolic compounds to hydrogen-rich gasses can prevent envi-ronmental pollution and save energy.Supercritical water(SCW)gasification of phenol is experimentally studied and a reactive force field molecular dynamics(ReaxFF-MD)simulation is conducted to investigate the catalytic mechanism of Ni/Al2 O3 in the phenol degradation.The experimental results indicate that Ni/Al2 O3 facilitates the conversion of phenol to 1-ethoxy butane via ring opening,which is a crucial step for complete gasification.The ReaxFF-MD simulation demonstrated that Ni facilitates the formation of H3 O free radicals and Ni-phenol inter-mediates.H3 O free radicals can be decomposed into H2 and OH free radicals.Both the generated OH free radical and Ni-phenol intermediate promote the ring-opening reaction of phenol.Ni promotes the direct decomposition of phenol into C1,C2,and C3 fragments,which is beneficial for further complete gasification.
基金supported by the National Natural Science Foundation of China(Grant Nos.5132301151306145&51236007)
文摘Energy conversion and utilization, particularly carbon-based fuel burning in air phase, have caused great environmental pollution and serious problems to society. The reactions in water phase may have the potential to realize clean and efficient energy conversion and utilization. Coal gasification in supercritical water is a typical carbon-based fuel conversion process in water phase, and it takes the advantages of the unique chemical and physical properties of supercritical water to convert organic matter in coal to H2 and CO2. N, S, P, Hg and other elements are deposited as inorganic salts to avoid pollution emission. The State Key Laboratory of Multiphase Flow in Power Engineering has obtained extensive experimental and theoretical results based on coal gasification in supercritical water. Supercritical water fluidized bed reactor was developed for coal gasification and seven kinds of typical feedstock were selected. The hydrogen yield covers from 0.67 to 1.74 Nm3/kg and the carbon gasification efficiency is no less than 97%. This technology has a bright future in industrialization not only in electricity generation but also in hydrogen production and high value-added chemicals. Given the gas yield obtained in laboratory-scale unit, the hydrogen production cost is U.S.$ 0.111 Nm3 when the throughput capacity is 2000 t/d. A novel thermodynamic cycle power generation system based on coal gasification in supercritical water was proposed with the obvious advantages of high coal-electricity conversion efficiency and zero pollutant emission. The cost of U.S.$ 3.69 billion for desulfuration, denitration and dust removal in China in 2013 would have been saved with this technology. Five kinds of heat supply methods are analyzed and the rates of return of investment are roughly estimated. An integrated cooperative innovation center called a new type of high-efficient coal gasification technology and its large-scale utilization was founded to enhance the industrialization of the technology vigorously.
基金supported by the National Natural Science Foundation of China(No.51888103).
文摘Coal consumption leads to over 15 billion tons of global CO_(2) emissions annually,which will continue at a considerable intensity in the foreseeable future.To remove the huge amount of CO_(2),a practically feasible way of direct carbon mitigation,instead of capturing that from dilute tail gases,should be developed;as intended,we developed two innovative supporting technologies,of which the status,strengths,applications,and perspective are discussed in this paper.One is supercritical water gasification-based coal/biomass utilization technology,which orderly converts chemical energy of coal and low-grade heat into hydrogen energy,and can achieve poly-generation of steam,heat,hydrogen,power,pure CO_(2),and minerals.The other one is the renewables-powered CO_(2) reduction techniques,which uses CO_(2) as the resource for carbon-based fuel production.When combining the above two technical loops,one can achieve a full resource utilization and zero CO_(2) emission,making it a practically feasible way for China and global countries to achieve carbon neutrality while creating substantial domestic benefits of economic growth,competitiveness,well-beings,and new industries.
