Turning NGCC Into IGCC: Cycle Retrofitting Issues
The increase in price of natural gas and the need for a cleaner technology to generate electricity has motivated the power industry to move towards Integrated Gasification Combined Cycle (IGCC) plants. The system uses a low heating value fuel such as coal or biomass that is gasified to produce a mixture of hydrogen and carbon monoxide. The potential for efficiency improvement and the decrease in emissions resulting from this process compared to coal-fired power plants are strong evidence to the argument that IGCC technology will be a key player in the future of power generation. In addition to new IGCC plants, and as a result of new emissions regulations, industry is looking at possibilities for retrofitting existing natural gas plants. This paper studies the feasibility of retrofitting existing gas turbines of Natural Gas Combined Cycle (NGCC) power plants to burn syngas, with a focus on the water/steam cycle design limitations and necessary changes. It shows how the gasification island processes can be treated independently and then integrated with the power block to make retrofitting possible. This paper provides a starting point to incorporate the gasification technology to current natural gas plants with minor redesigns.
An estimation of cogeneration potential by using refinery residuals in Mexico
Abstract Electric power generation in Mexico is mainly based on fossil fuels, specifically heavy fuel oil, although the use of natural gas combined cycles (NGCC) is becoming increasingly important. This is the main destination that has promoted growing imports of natural gas, currently accounting for about 20% of the total national annual consumption. Available crude oil is becoming heavier; thus refineries should be able to process it, and to handle greater quantities of refinery residuals. If all refinery residuals are used in cogeneration plants serving petroleum refineries, the high heat/power ratio of refinery needs, leads to the availability of appreciable quantities of electricity that can be exported to the public utility. Thus, in a global perspective, Mexican imports of natural gas may be reduced by cogeneration using refinery residuals. This is not the authors’ idea; in fact, PEMEX, the national oil company, has been entitled by the Mexican congress to sell its power leftovers to The Federal Electricity Commission (CFE) in order to use cogeneration in the way described for the years to come. A systematic way of determining the cogeneration potential by using refinery residuals from Mexican refineries is presented here, taking into account residual quantities and composition, from a national perspective, considering expected scenarios for Maya crude content going to local refineries in the years to come. Among different available technologies for cogeneration using refinery residuals, it is believed that the integrated gasification combined cycle (IGCC) would be the best option. Thus, considering IGCC plants supplying heat and power to refineries where it is projected to have refinery residuals for cogeneration, the expected electric power that can be sent to the public utility is quantified, along with the natural gas imports mitigation that may be attained. This in turn would contribute to a necessary fuel diversification policy balancing energy, economy and ecology.
Laminar heat or mass transfer in rectangular channels and in cylindrical tubes for fully developed flow: comparison of solutions obtained for various boundary conditions
Abstract A comparison is made of results obtained with various boundary conditions at the wall of the channels. By comparing blood Sherwood numbers for finite wall resistance with those for constant concentration boundary condition only a small variation is found for various points along the blood channel.