Thermodynamic Model of a Solar Receiver for Superheating of Sulfur Trioxide and Steam at Pilot Plant Scale

Within the European research project SOL2HY2, key components for a solar hybrid sulfur cycle are being developed and demonstrated at pilot scale in a real environment. Regarding the thermal portion, a plant for solar sulfuric acid decomposition is set up and initially operated at the research platform of the DLR Solar Tower in Jülich, Germany. One major component is the directly irradiated volumetric receiver, superheating steam and SO3 coming from a tube-type evaporator to above 1000 °C. At the design flow rate of sulfuric acid (50%-wt.) of 1 l/min, a nominal solar power of 57 kW is required at the receiver. With a flat ceramic absorber made from SiC and a flat quartz glass window, the design is based on lab scale reactors successfully demonstrated at the solar furnace of the German Aerospace Centre (DLR) in Cologne, Germany. A flexible lumped thermodynamic tool representing the receiver, compiled to assess different configurations, is presented in detail. An additional raytracing model has been established to provide the irradiation boundaries and support the design of a conical secondary concentrator with an aperture diameter of 0.6 m. A comparison with first experimental data (up to 65% nominal power), obtained during initial operation, indicates the models to be viable tools for design and operational forecast of such systems. With a provisional method to account for the efficiency of the secondary concentrator, measured fluid outlet temperatures (up to 1000 °C) are predicted with deviations of ±60 °C. Respective absorber front temperatures (up to 1200 °C) are under-predicted by 100-200 °C, with lower deviations at higher mass flows. The measured window temperature (up to 700 °C) mainly depends on the absorber front temperature level, which is well predicted by the model

The Impact of Decentralized Industrialization on a Taiwanese Village.

The decentralization of industrial production in Taiwan over the past ten years has had a powerful impact on rural economic organization. A number of small- and medium-scale factories have been established in the Central Taiwan village described here, creating a dem and for local unskilled workers. Commodities are produced primarily for sale in overseas markets. Local families have begun to model household factories after the kinds of factories established by non-local entrepreneurs, creating a new avenue for upward economic mobility. Many village housewives perform secondary manufacturing and finishing steps in their homes, working on a part-time, piece-rate basis. A large percentage of village households continue to farm rice on a part-time basis, although the average value of earnings from agriculture to household budgets has declined significantly. Specialized agricultural commodities such as ducks have become much more profitable than rice, and provide returns on household labor comparable to industrial employment. Agricultural and industrial production are interrelated because both draw labor primarily from the local community. The availability of attractive industrial employment in the village has greatly affected village social structure and process. Out-migration of villagers between the ages of 15 and 30 has slowed, and many out-migrant villagers have returned from urban locations. New employment patterns have encouraged parents to cut short the number of years they send their children to formal schooling. New strategies have been developed for investing the incomes of unmarried children still contributing incomes to the household. Few specific cultural changes can be linked directly to the villages new economic structure. However, attitudes toward work and its potential rewards have supported the labor-intensive production processes found in this village. Religious and ritual events are widely observed by all classes and age groups, and the application of traditional beliefs and rituals to industrial work settings suggests the continued vitality of the folk belief system. The proliferation of privately housed gods appears to differentiate villagers who have more fully embraced industrial activities and those who have not. The development of decentralized industry in rural Taiwan is similar to recent developments in the People's Republic of China in important respects, even though it is primarily export-oriented and has not taken a primary role in supporting agriculture as it has in the PRC.Ph.D.Cultural anthropologyUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/160192/1/8422297.pd

Modeling of a Solar Receiver for Superheating Sulfuric Acid

A volumetric solar receiver for superheating evaporated sulfuric acid is developed as part of a 100kW pilot plant for the Hybrid Sulfur Cycle. The receiver, which uses silicon carbide foam as a heat transfer medium, heats evaporated sulfuric acid using concentrated solar energy to temperatures up to 1000 °C, which are required for the downstream catalytic reaction to split sulfur trioxide into oxygen and sulfur dioxide. Multiple approaches to modeling and analysis of the receiver are performed to design the prototype. Focused numerical modeling and thermodynamic analysis are applied to answer individual design and performance questions. Numerical simulations focused on fluid flow are used to determine the best arrangement of inlets, while thermodynamic analysis is used to evaluate the optimal dimensions and operating parameters. Finally a numerical fluid mechanics and heat transfer model is used to predict the temperature field within the receiver. Important lessons from the modeling efforts are given and their impacts on the design of a prototype are discussed

Development and Test Operation of a Demonstration Plant for Sulfuric Acid Splitting at the DLR Concentrating Solar Power Tower Facility

Sulfuric acid splitting is a key step of the hybrid sulfur cycle (HyS) for solar thermochemical hydrogen production. This exothermal reaction can be divided into two steps: firstly, the evaporation of liquid sulfuric acid (H2SO4) at about 400 °C forming sulfur trioxide (SO3), and secondly, the decomposition of SO3 to sulfur dioxide (SO2) and oxygen (O2) at 800 – 1000 °C. While the first sub-reaction has fast kinetics, the second one is rather slow and requires the introduction of catalysts to achieve sufficient conversion. Since 2004 the concept of a solar receiver-reactor for sulfuric acid splitting has been developed by DLR and operated in its solar furnace during the European projects HYTHEC and HycycleS. In the follow-up European project SOL2HY2, a scale-up of this concept has been designed, developing a solar tower demonstration plant. This demonstrator has a design flow rate of 1 l/min of sulfuric acid (50 w%) and consist of four main components arranged in series and connected by Joule heated piping: a 60 kW electrical evaporator for vaporization of the liquid acid, a solar receiver for superheating the SO3 to about 1000 °C, an adiabatic reactor with a fixed bed of an iron(III) oxide catalyst and a scrubber. The Joule heated evaporator consists of six vertical steel tubes with a siliconized silicon carbide (SiSiC) inner tubes filled with porous SiSiC foam structures for enhanced heat transfer. Liquid acid is injected at the bottom and vaporizes while passing upwards through the pipes. The vapors are collected in a steel manifold and, subsequently, conveyed to the solar receiver with an outer shell also made of steel. Concentrated radiation from the solar field passes through a quartz glass window closing the receiver and heats up a sectioned absorber composed of porous SiSiC foam structures. After superheating in the receiver, the process gas passed through the catalyst bed for an adiabatic reaction forming SO2. Before neutralization with sodium hydroxide solution in the scrubber, the SO2 concentration is measured by a customized gas analysis system via UV/Vis spectroscopy. The pilot plant was constructed and assembled on the research platform of the DLR concentrating solar power tower facility in Juelich, Germany. The layout of the plant was accompanied and supported by thermo-mechanical modelling of the most important components like the evaporator and solar receiver. Initial operation of the demonstrator was performed with air and water as process fluids. During water operation, the solar receiver reached the predicted design parameters achieving a gas outlet temperature of 1000 °C at an absorber front temperature of 1200 °C and a solar power on aperture of 50 kW. In the adiabatic reactor, however, temperatures of only about 400 °C were measured which are too low for SO3 decomposition. Therefore, the system was modified placing the catalytic fixed bed directly behind the solar absorber in the outlet section of the receiver. In the following test runs, the temperatures of this adiabatic reaction zone were sufficiently high with a minimum temperature in excess of 750 °C below which the catalyst would be deactivated due to sulfate formation. As a result, testing could proceed with sulfuric acid as the feed successfully demonstrating decomposition of SO3. A detailed analysis of all results of the systematic on-sun test series is given in the present paper

Solar Hydrogen Generation via the HyS-Cycle – Solar Tower Pilot Plant for Sulphuric Acid Splitting

Solar Hydrogen Generation via the HyS-Cycle – Solar Tower Pilot Plant for Sulphuric Acid Splittin

Design of a pilot scale directly irradiated, high temperature, and low pressure moving particle cavity chamber for metal oxide reduction

Recently a novel design concept of a reactor—the cascading pressure reactor—for the thermochemical fuel production, using a solar-driven redox cycle, was proposed. In this concept, thermal reduction of metal oxide particles is completed in multiple stages, at successively lower pressures. This leads to an order of Magnitude decrease in the pumping power demand as compared to a single stage, which in turn increases the solar to fuel efficiency. An important step in the process is the transfer of heat in the form of concentrated solar radiation to the particles, while providing reducing conditions in the space surrounding the particles. In this context, a novel system for heating and reducing particles, with a focus on operating at the small prototype scale (below 20 kW), is investigated. The key goals of the system are continuous operation, uniform heating of the reactive material, the ability to heat reactive material to 1723 K or higher, and flexibility of control. These criteria have led to the conceptual design of a continuous thin-layer particle conveyor, contained in an apertured, windowed cavity and enclosed in a vacuum chamber. This chamber, in combination with a water-splitting chamber and other System components, allows the possibility of testing multiple redox materials without any significant change in the reactor design. The present work shows a potential design for the proposed component, feasibility tests of the physics of moving particles with relevant materials, and series of interconnected numerical models and calculations that can be used to size such a system for the appropriate scales of power and mass flow rates. The use of a unified design strategy has led to efficient development of the system. Experimental investigations of the horizontal motion plate allowed effective determination of motion profiles and bed uniformity. The most important factors determined through the modeling effort were the aperture diameter, which serves as the coupling point between the solar simulator lamp array and the cavity particle heating, and the particle bed thickness, which has a strong effect on the outlet temperature of the particles