Ahmed Shafeen

A novel process integration, optimization and design approach for large-scale implementation of oxy-fired coal power plants with CO2 capture

Abstract The widespread use of fossil fuels within the current energy infrastructure is considered as the largest source of anthropogenic emissions of carbon dioxide, which is largely blamed for global warming and climate change. At the current state of development, the risks and costs of non-fossil energy alternatives, such as nuclear, biomass, solar, and wind energy, are so high that they cannot replace the entire share of fossil fuels in the near future timeframe. Additionally, any rapid change towards non-fossil energy sources, even if possible, would result in large disruptions to the existing energy supply infrastructure. As an alternative, the existing and new fossil fuel-based plants can be modified or designed to be either “capture” or “capture-ready” plants in order to reduce their emission intensity through the capture and permanent storage of carbon dioxide in geological formations. This would give the coal-fired power generation units the option to sustain their operations for longer time, while meeting the stringent environmental regulations on air pollutants and carbon emissions in years to come. Currently, there are three main approaches to capturing CO 2 from the combustion of fossil fuels, namely, pre-combustion capture, post-combustion capture, and oxy-fuel combustion. Among these technology options, oxy-fuel combustion provides an elegant approach to CO 2 capture. In this approach, by replacing air with oxygen in the combustion process, a CO 2 -rich flue gas stream is produced that can be readily compressed for pipeline transport and storage. In this paper, we propose a new approach that allows air to be partially used in the oxy-fired coal power plants. In this novel approach, the air can be used to carry the coal from the mills to the boiler (similar to the conventional air-fired coal power plants), while O 2 is added to the secondary recycle flow as well as directly to the combustion zone (if needed). From a practical point of view, this approach eliminates problems with the primary recycle and also lessens concerns about the air leakage into the system. At the same time, it allows the boiler and its back-end piping to operate under slight suction; this avoids the potential danger to the plant operators and equipment due to possible exposure to hot combustion gases, CO 2 and particulates. As well, by integrating oxy-fuel system components and optimizing the overall process over a wide range of operating conditions, an optimum or near-optimum design can be achieved that is both cost-effective and practical for large-scale implementation of oxy-fired coal power plants.

A comparative study of refinery fuel gas oxy-fuel combustion options for CO2 capture using simulated process data

Publisher Summary This chapter highlights the large scale industrial greenhouse gas (GHG) emitters, mainly coal-fired power plants, refineries and other chemical plants are compelled in the near future to reduce their GHG emissions, especially carbon dioxide. This would be in accordance with the Kyoto protocol that is currently awaiting international ratification. Carbon dioxide, a major component of greenhouse gases, could be captured and isolated from different industrial flue gas streams by installing a CO2 capture and treatment plant. Once CO2 is captured, it can be stored permanently in suitable geological storage sites and/or used for coal-bed methane, enhanced oil recovery, or utilized for many other commercial applications. This chapter presents the application of oxy-combustion and CO2 capture to two refinery fuel gases with given compositions. The simulation results are presented for four different combustion modes, including the air case as the baseline and three oxy-fuel combustion cases. It shows that oxy-fuel combustion is a possible and viable approach for CO2 capture from refinery fuel gases. A cost analysis is also performed to find out the estimated CO2 capture and avoidance costs for each case. The CO2 avoidance cost was found to be approximately 3cents to 4.5cents per kg of CO2, excluding the transport and storage costs.

A Decentralized Control Structure for a CO2 Compression, Capture and Purification process: An Uncertain Relative Gain Array Approach

Abstract This paper presents a study on decentralized control structures that can be proposed to control a CO 2 compression, capture, and purification process for fossil fuel power plants based on oxyfuel combustion. A dynamic model that describes the transient behavior of this process is currently not available. Thus, the present work applied the Relative Gain Array (RGA) analysis to identify the most promising control strategies for this process. The process gains were estimated using a steady-state process model developed in Aspen Plus and validated with data obtained from the CanmetENERGY. The RGA analysis performed for the base case operation of this process was compared to an uncertain RGA analysis that takes into account the uncertainty on the process gains for control structure selection. The result obtained with the uncertain RGA demonstrates that the controller pairings suggested by nominal RGA can lead to control configurations with loops that may become unstable.

Gas Turbine Integrated High-Efficiency Oxy-Fuel Combustion Process With CO2 Capture

Fossil fuel energy conversion processes are the primary source of anthropogenic greenhouse gas emissions. New approach to utilization of fossil fuels through near-zero emission energy conversion systems represents an emerging opportunity for developing new concepts and designs, increasing the efficiency of the baseline combustion processes and reducing their environmental footprints, including greenhouse gas emissions, through CO2 capture and storage. Oxy-fuel combustion process provides an elegant way to address the environmental issues, in particular CO2 emissions, associated with current combustion systems. In this process nearly pure oxygen (instead of air) is burned with fuel. The resulting flue gas is composed mainly of CO2 and H2 O, and other trace contaminants (e.g., SOx , NOx and particulates). The challenge faced in the development of oxy-fuel systems is the inability of current design configurations and materials for combustors, boilers, and turbo-machinery, to operate at the high temperatures resulting from burning the fuel in pure oxygen. Recent development at CANMET has been focused on design of a new generation of advanced oxy-fuel systems. These systems are very compact and can be integrated with a modified gas turbine to generate electricity, while the products of combustion can be sent to another turbine for recovery. The resulting CO2 -rich stream at the outlet of the turbine is then sent to a CO2 capture and compression unit to separate and compress CO2 for pipeline transport. In this paper we present this proposed gas turbine integrated high-efficiency oxy-fuel combustion process and its main components, including the gas turbine and heat recovery system design. Moreover, we will present the results of the overall system integration, performance modeling and simulation to develop the tools required to asses the efficiency and viability of the overall integrated system and its components.Copyright