|
3. Subtask 3 : Conceptual design of the total system3.1 Conceptual design of the total system3.1.1 R&D GoalsThe objective of the conceptual design of the system is to describe the design configuration of a system ranging from the hydrogen production to its utilization by conducting a conceptual design on a practical scale and at the same time to present a technological development target from economic point of view by making cost estimate and sensitivity analysis of hydrogen , etc.In fiscal year 1993 as the first year of this research project, an investigation was conducted on the present situation of each individual technology of the processes from the hydrogen production to its utilization as well as that of the similar overseas projects. Based on this investigation, eligible technologies were selected which were applicable to WE-NET system, and the base system for the conceptual design which was to be conducted from the FY 1994 onward, was established. Based on these results, in the FY 1994, the conceptual design, cost estimate and sensitivity analysis were carried out on the system composed of hydrogen production utilizing solid polymer electrolytes water electrolysis, mass transportation and storage of hydrogen using liquid hydrogen and hydrogen combustion turbine in order to evaluate as a whole system the technology currently under R&D in WE-NET. From FY 1995 to 1996, transportation and storage system using methanol and ammonia, which could be composed of existing technologies, was selected, and then technical development themes were indicated through conceptual design, cost estimate and sensitivity analysis on the system, and also through comparison with the system using liquid hydrogen. In this fiscal year, followings were studied as the items regarding the system which is independent of large scale and concentrated utilization by liquid hydrogen utilizing renewable energy, based on various suggestions to the interim evaluation of the WE-NET research and development which had been conducted in last fiscal year by Agency of Industrial and Science tecnology, and also from the view point of social introduction and dissemination of hydrogen energy:
(1) Study on alternative hydrogen production methods
3.1.2 Results in fiscal year 19973.1.2.1 Study on alternative hydrogen production methodsAs the hydrogen production method which can be defined as extended form of existing technology and can secure huge amount of hydrogen, reforming method of coal gas and natural gas is selected, which is a typical method of hydrogen production from reforming of fossil fuel. Hydrogen production cost is calculated on this method and the cost is compared with hydrogen production cost using renewable energy. Recoverable amount of hydrogen from chemical plants and bio-mass utilizing systems, as securing other hydrogen supply sources, is also investigated.(1) Hydrogen production system by reforming fossil fuela. Hydrogen production system by coal gasificationA pressurized two stage entrained bed partial oxidization method using oxygen is selected as a type of coal gasification furnace. The study results| coal consumption by this method, hydrogen production, hydrogen production cost, system energy efficiency (=produced hydrogen energy/ total energy input for hydrogen production), and so on| are shown below.
b. Hydrogen production system by natural gas reforming The process of producing hydrogen by steam reforming using natural gas as raw material, is adopted on a major chemical industry requiring huge amount of hydrogen such as an ammonia plant and a methanol plant. In this study, specification of a hydrogen producing plant is studied considering the maximum unit capacity of existing ammonia plant as a basis for the study. Following are the study results of natural gas consumption, hydrogen production, hydrogen production cost, system energy efficiency (= hydrogen energy in final form thereof/ total energy input for hydrogen production) and etc.:
c. Hydrogen production cost evaluation by reforming of fossil fuel Comparing hydrogen production system by coal gasification with that by natural gas reforming, it is shown that both the system energy coefficients are almost same but hydrogen production cost by natural gas reforming is much cheaper than that by coal gasification. The reason why is material cost of coal for the coal gasification system is 0.9 yen/1000 kcal, which is lower than that for natural gas (LNG) of 1.8 yen/1000 kcal, but equipment cost is 78.1 billion yen for coal gasification, which is around 3 times higher than the natural gas reforming system. As the result of comparison of the hydrogen production cost by fossil fuel reforming with WE-NET hydrogen production cost from renewable energy utilizing overseas hydropower generation (in case of hydrogen combustion turbine with output of 1,000 MW, and transportation distance of 5,000 km), it is shown that the hydrogen production cost by fossil fuel reforming (cost before hydrogen combustion turbine) except cost for carbon dioxide sequenstration, is 4.3 to 7.0 yen/Mcal (13.1 to 21.4 yen/Nm3), and the cost is much cheaper than the WE-NET hydrogen production cost (7.2 to 10.6 yen/Mcal :21.9 to 32.2 yen/Nm3), as shown in the table below. However, since the WE-NET hydrogen production system is a clean energy system without any carbon dioxide emission, carbon dioxide sequenstration is indispensable for utilizing the fossil fuel system from a viewpoint of the environmental matter. Therefore, it is necessary to evaluate the cost including the carbon dioxide sequenstration ,but considering restrictions on environment aspect at the initial phase, the hydrogen production cost by fossil fuel reforming is assumed to have a possibility to compete with that by the WE-NET system.
Comparison of hydrogen production cost
(2) Investigation on recoverable amount of hydrogen from chemical plantThe recoverable hydrogen amount from an ethylene plant which occupies major part of a petrochemical industry complex, was investigated as an typical example of the recoverable hydrogen from off-gas of a chemical plant. As the result of investigation, it was indicated that highly pure hydrogen of some 7,300 Nm3/hr is possible to bring out from an ethylene plant of some 300,000 t/year plant capacity. Accordingly, hydrogen of around 1.38 billion Nm3/year potentially exists as recoverable highly pure hydrogen from the ethylene plants in all over Japan, considering all the production capacity of the ethylene plants. The quantity of this kind hydrogen corresponds to around 2.4% of objective for "Others alternative energy to oili1,900x104klj". It is considered that hydrogen dispersed utilization has a highly possibility.(3) Investigation on recoverable hydrogen amount from bio-mass systemsRecoverable hydrogen amount from raw material bio-mass such as poplar and from organic substances in black liquor recovered in paper and pulp production process were investigated.Assuming the recoverable hydrogen amount from raw material bio-mass is 20,000 Nm3/hr, required amount of the raw material bio-mass is 72,000kg/hr. That means that the raw material corresponding to 146 lumbers per hour when diameter and length of the lumber are 30cm and 20m, respectively. Also, it is indicated that hydrogen of 39 Nm3/hr can be recovered from black liquid treatment of 75 t/day, as the recoverable hydrogen amount from organic substances in the black liquid recovered in the paper and pulp production process. Accordingly, hydrogen of some 30,000 Nm3/day can be recovered, considering total treatment amount of the black liquid at paper and pulp producing factories (57,855 t/day) all over Japan. 3.1.2.2 Study on the total system including dispersed utilization of hydrogenHydrogen supply system combining dispersed hydrogen utilization system to the total system is studied, in view of introduction and dissemination of hydrogen energy system to whole the society as early as possible. As a model of dispersed utilization system, fuel cell system, hydrogen diesel engine system and automobile fuel system applied to a model city (population of some 300,000 grade) which is studied in the subtask 7, is assumed, Following are whole flow diagram of the hydrogen supply system combined with the dispersed hydrogen utilization system and overall system flow diagram of each dispersed utilization system.(1) Whole flow diagram of hydrogen supply systemFig. 3.1.2.2 (1)
(2) Overall system flow diagram of hydrogen supply system for hydrogen diesel engine
(3) Overall system flow diagram of hydrogen supply system to fuel cellAlmost the same with the hydrogen supply system for the hydrogen diesel facility(hydrogen compressor is not necessary). Fig. 3.1.2.2 (3)
(4) Overall system flow diagram of hydrogen supply system to hydrogen automobileFig. 3.1.2.2 (4)
3.1.2.3 Study on middle range hydrogen gas transmission pipelineHydrogen transportation by the hydrogen gas transmission pipeline from the inland part of China to Northern Kyushu area via East China Sea, is studied on reference to "Study results of natural gas pipe line over a wide area conducted by the private sector" as one of alternative systems that enables reduction of storage and transportation cost, for the purpose of reduction of power generation cost of hydrogen combustion turbine. Following are overall flow diagram of gas pipeline transportation system of hydrogen and main study results thereabout:(1) Overall flow diagram of pipeline transportation system of hydrogenFig. 3.1.2.3
(2) Main study results of pipeline transportation of hydrogen gas
Transportation cost of hydrogen by middle range pipeline transportation of hydrogen gas, 15.2 yen/Nm3, is less expensive in comparison with corresponding transportation cost by liquid hydrogen transportation system (liquefaction cost of hydrogen + storage cost (hydrogen supply side) + tanker transportation cost), 19.2 yen/Nm3 , therefore it may be possible to lead up to reduction of power generation cost utilizing hydrogen combustion turbine. 3.1.2.4 Application of life cycle assessment on CO2 emissionRegarding each system of the WE-NET system (transportation systems of liquid hydrogen, methanol and ammonia) targeting large and concentrated utilization of hydrogen, inventory analysis of each raw material used for from construction to operation thereof, was conducted to calculate preliminarily the carbon dioxide emission factors(CO2 emissions per kWh) as an assessment of environmental impact load. As the result, the CO2 emission factors(g-C/kWh) in the WE-NET system was calculated to be 7.63 g-C/kWh for the liquid hydrogen transportation system, 179 g-C/kWh for the methanol transportation system and 15.2 g-C/kWh for the ammonia transportation system, respectively, when operation life of the system is assumed to be 30 years. The CO2 emission factors of the liquid hydrogen transportation system and the ammonia transportation system is almost as same as that of existing renewable energy power generation system (hydropower, geothermal power, solar power and wind power) and thus those systems can be defined as the system with less environmental impact load. However, since coal is used for methanol synthesis, CO2 emission per kWh of power generation system by the methanol transportation is as high as that of existing LNG fired power generation system. For that reason, integrated system effectively combined with CO2 sequenstration technology is absolutely required for the future.3.1.2.5 Development of soft-ware for system designingIn this study, the soft-ware program of oxygen production facility was added to the existing soft-ware program of liquid hydrogen transportation system, as well as the soft-ware program of the cost calculation was developed, for the alternative hydrogen production methods along with the hydrogen gas pipeline transportation system. Those study results support quite effectively for conducting cost calculation of the systems.3.1.3 Research plan for fiscal year 1998In the next fiscal year, which is final fiscal year of the first phase research and development of the WE-NET project, it is scheduled to reflect the most recent research result of each sub-task into "Conceptual design of the total system" and to indicate clearly future technical development theme.
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
