Chemical looping gasification and reforming – A perspective and prospects of novel circulating fluidized bed systems

The concept of chemical looping reactions has been widely applied in chemical industries. Fundamental research on chemical looping reactions has also been applied to energy systems. Fossil fuel chemical looping applications were used with the steam-iron process for coal from the late 1800s to early1900s and were demonstrated at a pilot scale for synthetic natural gas production with the IGT HYGAS Process and the CO2 Acceptor Process in the 1960s and 1970s. There are presently no chemical looping processes using carbonaceous fuels in commercial operation. Key technical factors that determine commercial viability of the technology lie in the sustainability of the reactivity and recyclability of the metal oxide oxygen carriers and the ability of configuring the reactor assembly for optimal operation and control of the solids flow system. The chemical looping system is developed on the circulating fluidized bed platform. The successful deployment of this technology requires thorough knowledge of two interconnected fields, i.e., metal oxide reaction engineering and particle science and technology. With now CO2 emission control of great concern and process conversion efficiency enhancement of great interest, activities on research and development of chemical looping technology have resurfaced. Specifically, chemical looping technology is a manifestation of the interplay among such key elements of metal oxide reaction engineering and particle science and technology as particle synthesis, reactivity and mechanical properties, flow stability and contact mechanics, gas-solid reaction engineering and particulates system engineering. This presentation will describe the fundamental and applied features of modern chemical looping technology in the context of the circulating fluidized bed platform that utilizes fossil and other carbonaceous feedstock. It will discuss the reaction chemistry, ionic diffusion mechanisms, metal oxide synthesis and thermodynamics, reactor design, and system engineering along with energy conversion efficiency and economics of the chemical looping processes for, specially, partial and selective oxidation for syngas and chemicals production. The Ohio States University has developed a number of advanced chemical looping gasification and reforming processes which will be highlighted in this presentation. Potential for solar based chemical looping technology will also be discussed

Fish communities in small agricultural streams of Iowa: relationships with environmental factors

Fish distribution and composition in small agricultural streams were compared between major river basins (Mississippi and Missouri) and among five subecoregions in the Iowa region of the Western Corn Belt Plains Ecoregion (WCBPE)) using a 1981-1984 state survey database. Additionally, environmental and fish data were collected from April 1992 to October 1993 from five 50-m stream sections in each of 10 streams representing the subecoregions. The associations among watershed, stream habitat, and fish community features were investigated. The 1993 flooding effects on the headwater habitat and fish communities were also explored. Watershed data were derived from maps, remote imagery and field inspection, and integrated by Geographical Information Systems (GIS) technology. Habitat data were collected in each stream section in 1992 and 1993;The distinctions in headwater fish distribution and composition were significant both between major river basins and subecoregions. These variations result from the interactions of natural and historical factors such as topography, soil type, and drainage connections and human activities, including stocking and agricultural disturbances;The northern, rowcrop-dominated watersheds commonly exhibited better stream habitat conditions such as greater water clarity and habitat complexity than the southern watersheds, which have greater grazing landuse. Moreover, fish communities in the northern headwaters also demonstrated greater species richness and total number of individuals, a greater proportion of insectivores, and a lower proportion of omnivores;Linear structural relations (LISREL) models identified four major factors in structuring headwater habitat and fish communities: geological and agricultural influences, precipitation, riparian forest zone, and stream width. The 1993 flooding influenced the communities in reducing adult abundance, changing physical and chemical habitat features, and rearranging the environmental associations with fish species

Iron-based chemical looping processes

Chemical looping technology has attracted significant attention due to its potential in cost-effective CO2 capture capabilities. It utilizes metal oxide as oxygen carriers to indirectly convert carbonaceous fuel such as coal, natural gas and biomass into electricity, H2, liquid fuel without the use of an air separation unit (ASU). In the case of power production, chemical looping process allows for high exergy efficiency, as the high grade heat produced from the oxidation of the oxygen carrier can be extracted for steam production, while the lower grade heat is recuperated in the oxygen carrier to perform its endothermic reduction. With the exponential growth of research and publications in this field, chemical looping has expanded to encompass both power and chemical production with in-situ gas separation. Extensive computational and experimental studies on iron-based composite material support the long-term recyclability, reactivity and physical strength of OSU’s oxygen carriers. In addition, the behavior of iron-based composite material at the micro- and nanoscale will be discussed in the context of optimal oxygen carrier candidates. Nanostructure formation mechanism and ionic diffusion play a central role in sustaining the reactivity and recyclability of Fe-Ti system. OSU’s unique moving-bed chemical looping technology takes full advantage of iron-based oxygen carriers when compared with fluidized-bed system. The synergetic effect between reactor design and oxygen carrier optimization ensures complete fuel conversion and near 100% CO2 capture. To date, more than 1000 operating hours have been achieved in 25-kWth sub-pilot scale unit with coal, biomass and syngas at the OSU Clean Energy Research Center. Near 100% conversion of both gaseous and solid fuel types to CO2 were achieved. A 250 kWth-3MWth syngas chemical looping pilot scale demonstration is currently in its testing phase at the National Carbon Capture Center. The present paper summarizes key results and development for both the syngas chemical looping and coal direct chemical looping systems

Hydrodynamics of chemical looping combustion systems: Effects of reactor design parameters

Chemical looping combustion (CLC) has been considered a transformational technology for the carbon dioxide (CO2) capture in power plants. Extensive research has been conducted on the selection and preparation of oxygen carrier (OC) materials, their production and characterization, CLC process development, and reactor system demonstrations from bench to pilot scales. Different configurations of CLC system have been proposed and tested, such as interconnected circulating fluidized bed (CFB) reactor systems, CFB with counter-current moving bed reactor systems, and fixed bed reactor systems. Despite considerable research efforts on the development of CLC systems, the analysis of the effects of hydrodynamic characteristics of OC particles, such as particle size, density and support content, on the design and operation of the CLC system is still lacking. Further, major operational parameters that continue to be in need of exploration include the control of the solids circulation rate of the system, pressure balance and profile of the system, and the gas sealing from the interconnected reactors. This study examines the inter-relationships between the hydrodynamics and kinetics characteristics of the OC particles and the operating conditions of the reactors, along with the reaction and heat management of the system. The design principle that is applied to sizing the reactor system is developed. Parametric effects on the system performance due to the variation of particle parameters, reactor size, system pressure, and operating conditions are simulated and analyzed

Characterization of loop seal in a complex circulating fluidized bed system

Loop seal is widely used in circulating fluidized bed systems to transport solids from high pressure reactor to low pressure reactor. It also found applications in complex systems with multiple reactors. The functions of the loop seal include circulating solids between reactors with desired solids flow rate, preventing gas leak from either reactor, and providing pressure balance for the proper operation of the system. The proper design and sizing of the loop seal are necessary so that the operation of loop seal is not to disturb the desired, independent operation of the reactors. Despite its extensive applications, the systematic, experimental studies that characterize the loop seal operation in the complex reactor systems are limited. Among the available studies, the particles used are mainly Geldart group A and group B particles. Little is conducted on experiments with Geldart Group D particles. This paper examines the operation of solids through a loop seal in a complex circulating fluidized bed system using Geldart group D particles. The circulating fluidized bed has two reactors whose operational conditions are controlled independently, with a loop seal placed between them. Besides the loop seal and the two reactors, the CFB system also includes a riser, a cyclone, a solids receiver, and standpipes. The solids inlet in the supply chamber of the loop seal is connected to the bottom of the standpipe, while the solids outlet in the return chamber is connected to the solids inlet of a dense phase fluidized bed reactor. A gas outlet with a valve and a gas flowmeter is designed to be located at the top of the return chamber to control the gas flow rate flowing into the fluidized bed reactor downstream the loop seal. The rectangular supply chamber has a dimension of 25 mm x 75 mm x 150 mm and the square return chamber is 75 mm × 75 mm × 300 mm. The pressure profile of the system is recorded using differential pressure gauges and pressure gauges are installed throughout the system. The solids circulation rate of the system is measured using a solids bypassing system connected between the bottom of the system and the top of the standpipe. Effects of operating parameters, such as supply chamber gas flow rate, return chamber fluidization velocity, and gas flow rate from the gas outlet of return chamber, on the operation of the circulating fluidized bed system, including the solids circulation rate and the system pressure balance are also analyzed and discussed

Depth Extraction from a Single Image and Its Application

In this chapter, a method for the generation of depth map was presented. To generate the depth map from an image, the proposed approach involves application of a sequence of blurring and deblurring operations on a point to determine the depth of the point. The proposed method makes no assumptions with regard to the properties of the scene in resolving depth ambiguity in complex images. Since applications involving depth map manipulation can be achieved by obtaining all-in-focus images through a deblurring operation and then blurring the obtained images, we have presented methods to derive all-in-focus images from our depth maps. Furthermore, 2D to 3D conversion can also be achieved from the estimated depth map. Some demonstrations show the performance and applications of the estimated depth map in this chapter