Polygeneration Systems And Hydrogen Utilization Of Natural Gas-Based Acetylene Process

Due to the increasing depletion of resources and energy sources all over the world, efficient and economical energy systems are of utmost importance for the future in terms of sustainable development. Polygeneration systems, which integrate high efficiency systems, are effective ways to achieve efficient resources utilizing and build an economy resource social.Supported by the NSF of China (No.: 90210032), the major aim of this research is to investigate the integration principles and reasonable matching relations of the natural gas-based acetylene process. The major aim of this research is to propose a mechanism of hydrogen conversion and utilization in natural gas et al. fossil fuel complex energy conversion systems, and to develop a novel hydrogen power generation cycle and polygeneration systems for acetylene production and power generation. The main contents are as follows:First, the influence of operational conditions on the fractional conversion of hydrogen and the energy level needed in the conversion process of hydrgen to carbon monoxide are investigated. This paper finds out that the increasing of the molar ratio of carbon dioxide to hydrogen can achieve two aims: (1) decreasing the temperature of heat source; and (2) increasing the fractional conversion of hydrogen and increasing the content of carbon monoxide. Under the same conditions, the burning of the CO gas is able to release more heat than the H₂ gas. Comparing with the process of hydrogen conversion to power directly, H₂ and CO₂ inverse shift reaction can be considered as a indirect way of hydrogen conversion and utilization. Based on the analysis of acetylene process based on natural gas, this paper finds that when the process produces acetylene product a large amount of H₂-rich gas will be produced in the reactor. So the efficient conversion and utilization of hydrogen is an important way to establish novel polygeneration systems of acetylene and power and becomes the energy integration principles of polygeneration systems.Secondly, this paper presents a graphic analysis method will be introduced, which involves thermodynamic principles of energy analysis and energy integration, a flowrate-exergy diagram (FED), which consists of a plot representing the increase or decrease of the flowrate of H₂ vs. the exergy change of the process, and a series of revelatory criteria to use the FED mainly from process configuration. In some complex energy conversion process system related to hydrogen, as like as an acetylene production process, the influence of hydrogen conversion and utilization on the characteristics of energy conversion is very important. The proposed tool visually and concisely describes the conversion rates of hydrogen and hydrogenous chemicals associating with the exergy loss. Based on the analysis and comparison of the graph it is able to discover the cause of affecting the hydrogen conversion efficiency and find out the relative advanced technology. Then the FED may be used to develop retrofitting processes to improve the energy conversion efficiency.Then three novel acetylene production and power generation polygeneration systems based on natural gas systems were developed and investigated in this paper. They related to direct power conversion and indirect conversion of hydrogen.Based on the investigation of partial oxidation/combustion (POC) of natural gas for producing acetylene process and the proton exchange membrane fuel cell (PEMFC), a novel polygeneration system that integrates the acetylene process and fuel cells is presented. The system produces acetylene and power by a process of the POC of natural gas process, a water gas water-gas shift reactor, a fuel cell and a waste heat boiler auxiliary system to recover the exhaust heat and gas from the fuel cell. The new polygeneration system's exergy analysis and the flow rate of the products were investigated by the aid of FED, to reveal that the energy conversion and systematic integration mechanism demonstrated the improvement of natural gas energy conversion efficiency.Based on the analysis of steam reforming of natural gas and H₂/O₂ cycle system, a novel acetylene and H₂/O₂ cycle polygeneration system was proposed by the use of FED revelatory criteria and system integration method. The energy conversion characteristics and system efficiency of the system are researched. The thermodynamic principle of the new system and coupling mechanism for hydrogen conversion and energy integration between the acetylene process based on natural gas and H₂/O₂ cycle were both revealed with the aid of FED method.A novel high-efficiency power cycle system is proposed, which is composed of chemical recuperative with H₂ and CO₂ reverse shift reaction, chemical heat recovery with an ammonia absorption refrigeration cycle, and cooling the inlet gas. First, the heat is recovered from the turbine exhaust to drive H₂ and CO₂ reverse shift reaction, and then lower temperature heat from the turbine exhaust is provided with the ammonia absorption refrigeration system to generate chilled media, which is used to cool the turbine inlet gas except export. In this paper, a detailed thermodynamic analysis is carried out to reveal the performance of the proposed cycle and the influence of key parameters pressure ratio and temperature of interlet on performance is discussed, which shows the new cycle achieves the indirect efficient use of hydrogen. Based on the analysis of the power cycle and the energy integration principles of acetylene and power polygeneration systems, a new acetylene and power polygeneration system is proposed.