Jinyue Yan

Potential market niches for biomass energy with CO2 capture and storage - Opportunities for energy supply with negative CO2 emissions

The paper presents an analysis of biomass energy with CO2 capture and storage (BECS) in industrial applications. Sugar cane-based ethanol mills and chemical pulp mills are identified as market niches with promising prospects for BECS. Calculations of CO2 balances of BECS in these applications show that the introduction of CO2 capture and storage in biomass energy systems can significantly increase the systems’ CO2 abatement potentials. CO2 emissions of the total systems are negative. The CO2 reduction potentials of these technologies are discussed in regional and global contexts. An economic assessment of each system is carried out and opportunities for cost-effective technologies for CO2 capture, transportation and storage are identified. Furthermore, potentials for system improvements that could substantially decrease the CO2 abatement cost are addressed.

Biodiesel production from waste cooking oil catalyzed by TiO2-MgO mixed oxides.

Mixed oxides of TiO(2)-MgO obtained by the sol-gel method were used to convert waste cooking oil into biodiesel. Titanium improved the stability of the catalyst because of the defects induced by the substitution of Ti ions for Mg ions in the magnesia lattice. The best catalyst was determined to be MT-1-923, which is comprised of an Mg/Ti molar ratio of 1 and calcined at 923 K, based on an assessment of the activity and stability of the catalyst. The main reaction parameters, including methanol/oil molar ratio, catalyst amount, and temperature, were investigated. The catalytic activity of MT-1-923 decreased slowly in the reuse process. After regeneration, the activity of MT-1-923 slightly increased compared with that of the fresh catalyst due to an increase in the specific surface area and average pore diameter. The mixed oxides catalyst, TiO(2)-MgO, showed good potential in large-scale biodiesel production from waste cooking oil.

Black liquor gasification integrated in pulp and paper mills: A critical review.

Black liquor gasification (BLG) has potential to replace a Tomlinson recovery boiler as an alternative technology to increase safety, flexibility and energy efficiency of pulp and paper mills. This paper presents an extensive literature review of the research and development of various BLG technologies over recent years based on low and high temperature gasification that include SCA-Billerud process, Manufacturing and Technology Conversion International (MTCI) process, direct alkali regeneration system (DARS), BLG with direct causticization, Chemrec BLG system, and catalytic hydrothermal BLG. A few technologies were tested on pilot scale but most of them were abandoned due to technical inferiority and very fewer are now at commercial stage. The drivers for the commercialization of BLG enabling bio-refinery operations at modern pulp mills, co-producing pulp and value added energy products, are discussed. In addition, the potential areas of research and development in BLG required to solve the critical issues and to fill research knowledge gaps are addressed and highlighted.

Intensification of biodiesel synthesis using zigzag micro-channel reactors.

Zigzag micro-channel reactors have been fabricated and used for continuous alkali-catalyzed biodiesel synthesis. The influences of the main geometric parameters on the performance of the micro-channel reactors were experimentally studied. It has been found that the zigzag micro-channel reactor with smaller channel size and more turns produces smaller droplets which result in higher efficiency of biodiesel synthesis. Compared to conventional stirred reactors, the time for high methyl ester conversion can be shortened significantly with the methyl ester yield of 99.5% at the residence time of only 28 s by using the optimized zigzag micro-channel reactor, which also exhibits less energy consumption for the same amount of biodiesel during biodiesel synthesis. The results indicate that zigzag micro-channel reactors can be designed as compact and mini-fuel processing plant for distributive applications.

Potential and cost-effectiveness of CO2 reductions through energy measures in Swedish pulp and paper mills

Using the two criteria of potential CO2 reduction and cost of CO2 reduction, technical energy measures in Swedish pulp and paper mills are investigated. Principal CO2-reducing measures analysed are: decreased specific energy utilisation, fuel switch, and CO2 capture and sequestration. Among the investigated measures, conventional technologies for electricity conservation and improved electrical conversion efficiency in existing systems for cogeneration of heat and power are identified as the most cost-effective alternatives that also have large CO2 reduction potentials. For commercially available technologies, the results indicate an accumulated reduction potential of up to 8 MtCO2/y (14% of the Swedish net emissions). If emerging technologies for black liquor gasification (BLG) with pre-combustion CO2 capture and sequestration are considered, the CO2 reduction potential increases by up to 6 MtCO2/y (10% of the Swedish net emissions). Commercialised BLG, CO2 capture and reliable CO2 sequestration technologies are identified as important potential contributors to Swedish compliance with Kyoto Protocol targets, especially in a scenario of nuclear power closure.

A total energy system of fuel upgrading by drying biomass feedstock for cogeneration: a case study of Skellefteå bioenergy combine

Emissions of greenhouse gases, such as CO2, need to be greatly reduced to avoid the risk of harmful climate changes. One way to mitigate emissions is switching fuels, from fossil fuels to renewable energy, e.g., biomass. In this paper we investigate a new approach for improving the performance of biomass-based cogeneration plants, a bioenergy combine. The system is a conventional biomass-based combined heat and power (CHP) plant with integrated pellet production, where part of the CHP plants heat is used for drying biomass feedstock for producing pellets. This unique integration enables increased annual operational hours and an increased use of biomass because the upgraded pellets as an energy carrier can be economically and technically transported from regions with a surplus biofuel to regions with demand for biofuel. In the studied case of this paper, the produced pellets are transported to another CHP plant for substituting fossil fuels. The total energy system of the bioenergy combine and the linked CHP plant is analysed from a perspective of CO2 reduction and energy efficiency. The results show that the system has great potential for reducing CO2 and increasing the efficiency. Furthermore, the non-technical factors influencing the realisation of the project has also been studied through interviews, showing that the main criterion behind the investment was the potential for profitability. In addition, an important factor that facilitated the realisation was the co-operative environment between the municipality and Skelleftea Kraft. Environmental issues appeared not to be influencing direct, but indirect through government subsidies.

Ammonia-water bottoming cycles: a comparison between gas engines and gas diesel engines as prime movers

Ammonia–water cycles can produce more power than steam Rankine cycles in several applications. One of these applications is as a bottoming cycle to internal combustion engines. In the present study, ammonia–water bottoming cycle configurations for spark-ignition gas engines and compression-ignition gas diesel engines have been compared. Single-pressure Rankine cycles have been used as a basis for the comparison. Low heat source temperatures should increase the difference in power output between the ammonia–water cycle and the Rankine cycle. However, in this study, the results of the simulations show different trends. In most cases, the ammonia–water bottoming cycles with gas engines as prime movers generate more power compared to a Rankine cycle than when gas diesel engines are the prime movers. The temperature of the most important waste heat source, the exhaust gas, is approximately 100°C higher for the gas engines than for the gas diesel engines. Therefore, for the gas engines, most of the waste heat available to a bottoming cycle is in the form of relatively high-temperature exhaust gas, while for the gas diesel engines more of the waste heat is in the form of relatively low-temperature heat sources.

Bio-refinery system of DME or CH4 production from black liquor gasification in pulp mills.

There is great interest in developing black liquor gasification technology over recent years for efficient recovery of bio-based residues in chemical pulp mills. Two potential technologies of producing dimethyl ether (DME) and methane (CH(4)) as alternative fuels from black liquor gasification integrated with the pulp mill have been studied and compared in this paper. System performance is evaluated based on: (i) comparison with the reference pulp mill, (ii) fuel to product efficiency (FTPE) and (iii) biofuel production potential (BPP). The comparison with the reference mill shows that black liquor to biofuel route will add a highly significant new revenue stream to the pulp industry. The results indicate a large potential of DME and CH(4) production globally in terms of black liquor availability. BPP and FTPE of CH(4) production is higher than DME due to more optimized integration with the pulping process and elimination of evaporation unit in the pulp mill.

Performance evaluation of adding ethanol production into an existing combined heat and power plant

In this paper, the configuration and performance of a polygeneration system are studied by modelling the integration of a lignocellulosic wood-to-ethanol process with an existing combined heat and power (CHP) plant. Data from actual plants are applied to validate the simulation models. The integrated polygeneration system reaches a total efficiency of 50%, meeting the heating load in the district heating system. Excess heat from the ethanol production plant supplies 7.9 MW to the district heating system, accounting for 17.5% of the heat supply at full heating load. The simulation results show that the production of ethanol from woody biomass is more efficient when integrated with a CHP plant compared to a stand-alone production plant. The total biomass consumption is reduced by 13.9% while producing the same amounts of heat, electricity and ethanol fuel as in the stand-alone configurations. The results showed that another feature of the integrated polygeneration system is the longer annual operating period compared to existing cogeneration. Thus, the renewable electricity production is increased by 2.7% per year.

Status and Perspective of Externally Fired Gas Turbines

Power generation with an externally fired gas turbine (EFGT) is a promising technology for solid fuels such as coal and biomass because it offers high efficiency, low cost, and low environmental impacts. Different systems of EFGT are presented, including externally fired combined cycles and externally fired humid air turbines. Recent research and engineering development of the technologies are reviewed. Topics including system configurations, thermal efficiencies, and high-temperature heat exchangers issues are discussed. The results of this study can be applied to guide the future development of solid-fuel-based externally fired gas turbine systems.