Siyu Yang

Comparative study of coal, natural gas, and coke-oven gas based methanol to olefins processes in China

Abstract Traditional olefins production mainly depends on oil. In view of the short supply of oil, feedstocks are expanded to coal, natural gas, coke-oven gas, and methanol in China. In this paper, a comparative study of alternative olefins production is conducted from aspects of techno-economic feasibility and environmental friendliness. Results show that coal-to-olefins has a significant cost advantage. However, it suffers from low energy efficiency and serious CO2 emissions. To address these problems, this study proposes and analyses coal-to-olefins with CO2 capture, coal and natural gas-to-olefins, and coal and coke-oven gas-to-olefins. The two co-feed systems ensure great reduction of CO2 emissions and significant improving energy efficiency. They should be actively developed in regions with rich coal and gas. While in regions with rich coal and lean gas, coal-to-olefins with CO2 capture should be developed in large scale. This paper also provides several suggestions on planning these olefins production routes in China.

Life cycle assessment of coal-based methanol

Abstract This paper analyzes the environment impact of methanol production from both product life cycle and process life cycle. Four indicators, global warming, acidification, photochemical oxidant formation and human toxicity, are used for assessment. According to the analysis, the periods that have significant impacts on environmental performance are explored. Several suggestions are provided at the end.

Multi-scale sustainability assessments for biomass-based and coal-based fuels in China

Transportation liquid fuels production is heavily depend on oil. In recent years, developing biomass based and coal based fuels are regarded as promising alternatives for non-petroleum based fuels in China. With the rapid growth of constructing and planning b biomass based and coal based fuels production projects, sustainability assessments are needed to simultaneously consider the resource, the economic, and the environmental factors. This paper performs multi-scale analyses on the biomass based and coal based fuels in China. The production cost, life cycle cost, and ecological life cycle cost (ELCC) of these synfuels are investigated to compare their pros to cons and reveal the sustainability. The results show that BTL fuels has high production cost. It lacks of economic attractiveness. However, insignificant resource cost and environmental cost lead to a substantially lower ELCC, which may indicate better ecological sustainability. CTL fuels, on the contrary, is lower in production cost and reliable for economic benefit. But its coal consumption and pollutant emissions are both serious, leading to overwhelming resource cost and environmental cost. A shifting from petroleum to CTL fuels could double the ELCC, posing great threat to the sustainability of the entire fuels industry.

Revision and Extension of Eco-LCA Metrics for Sustainability Assessment of the Energy and Chemical Processes

Ecologically based life cycle assessment (Eco-LCA) is an appealing approach for the evaluation of resources utilization and environmental impacts of the process industries from an ecological scale. However, the aggregated metrics of Eco-LCA suffer from some drawbacks: the environmental impact metric has limited applicability; the resource utilization metric ignores indirect consumption; the renewability metric fails to address the quantitative distinction of resources availability; the productivity metric seems self-contradictory. In this paper, the existing Eco-LCA metrics are revised and extended for sustainability assessment of the energy and chemical processes. A new Eco-LCA metrics system is proposed, including four independent dimensions: environmental impact, resource utilization, resource availability, and economic effectiveness. An illustrative example of comparing assessment between a gas boiler and a solar boiler process provides insight into the features of the proposed approach.

An integrated process of coke-oven gas tri-reforming and coal to methanol with high carbon utilization and energy efficiency

Abstract The hydrogen to carbon (H/C) ratio of coal gasified gas ranges of 0.2-1.0, far less than the desired value for the coal to methanol process. Therefore, a water gas shift (WGS) unit is needed to raise the H/C ratio, which results in a great deal of CO 2 emission and carbon resource waste. On the other side, in the coking process, massive coke-oven gas (COG) is not been fully used, with a high H/C ratio at 6.5, consisting of 60% hydrogen and 26% methane. Proposed in this paper is an integrated process of coke-oven gas and coal gasification to methanol, in which a tri-reforming reaction is used to convert methane and carbon dioxide to syngas. The carbon utilization efficiency of the new process increases to 65% from 40% of the current coal to methanol process, while the carbon dioxide emission declines by 44%.

Techno-economic analysis of coal gasification based co-production systems

Abstract Coal gasification based co-production systems are increasing popular in the world because they are assumed to be advantageous in energy efficiency and economic cost. However, there has been seldom researches on quantifying these advantages. In this paper, the co-prouction systems are analyzed from the technical and ecnomic point of views. During the study, the co-production system, of which the products are electricity and methanol, is modeled and simulated. For analysis, the energy analysis model and the economy analysis model are established. Results show that the co-production system has higher energy efficiency and less capital expenditure than tranditional single production systems.

Investigation on Life-cycle Cost of Coal-based Synthetic Natural Gas (SNG)

Abstract Coal-based synthetic natural gas (SNG) is considered to be a promising alternative of clean energy, especially for urban uses, to response to the insufficient supply of natural gas in China, In this paper, life cycle costing is conducted for SNG in three main urban applications: heating boiler use, residential use, and transit bus use, respectively. The results show that the SNG is competitive for residential use, while it is not as cost- effective as expected when used for heating boiler use or transit bus use. Major shortcoming of SNG is from the large environmental emissions in the production stage.

A framework for sustainability of coal based energy and chemical processes

Abstract A framework is proposed for sustainability study of coal based chemical and energy processes. Comprehensive analysis from efficiency, energy, economic, and environment perspectives. Process modelling, synthesis, and life cycle analysis, are conducted. Based on these multi-layer analyses, optimization is applied to explore for new process innovation and existing process modification. The analysis is illustrated with two case studies. The first case is the coal based methanol production process, which environmental impacts were investigated in a life cycle assessment. The second case is the co-production of electricity and methanol, in which key parameters are designed by mutual optimisation of energy efficiency and economic cost.