Upscaling of a 500 kW Solar Powered Reactor. for steam Gasification of Petroleum Coke
A. Vidal*1, T. Denk2, A. Valverde2, A. Steinfeld3, L. Zacarfas4, J. C. de Jesus4 and
M. Romero1
1 CIEMAT, 28040 Madrid, Spain
2 PSA-CIEMAT, 04200 Tabernas (Almeria), Spain
3 PDVSA INTEVEP, 1070-A Caracas, Venezuela
4 ETH, 8092 Zurich, Switzerland Corresponding Author, alfonso. vidal@ciemat. es
Abstract
Hybrid solar/fossil endothermic processes, in which fossil fuels are used exclusively
chemical source for H2 production and concentrated solar power is used exclusively
energy source of process heat, offer a viable route for fossil fuel decarbonization and a transition path towards solar hydrogen. Research in recent years has demonstrated the efficient use of solar thermal energy for driving endothermic chemical reforming reactions in which hydrocarbons are reacted to form syngas. This process produces not only a highly useful and transportable end product, but also results in the storage of a significant fraction of solar energy in the chemical bonds of the fuel molecules.
The steam-gasification of petroleum derivatives and residues using concentrated solar radiation is proposed as a viable alternative to solar hydrogen production. Therefore, PDVSA, CIEMAT and ETH started a joint project with the goal to develop and test a 500 kW plant for steam gasification of petcoke. This report summari zes the major accomplishments and challenges of upscaling the installation at the SSPS - tower of the Plataforma Solar de Almeria.
Keywords: Solar Chemistry, Gasification, Central Receiver, Petroleum Coke, Slurry
Gasification, which is a means to convert fossil fuels, biomass and wastes into either a combustible gas or a synthesis gas for subsequent utilization. The feedstocks include coal, natural gas (for reforming applications), refinery residues and biomass/wastes in combination with coal.
The use of high temperature solar heat to drive the endothermic reaction associated with coal gasification has been suggested and investigated in the last 20 years. The advantages of supplying solar energy for process heat are three-fold:
• Calorific value of the feedstock is upgraded
• Gaseous products are not contaminated by the by products of combustion; and
• Discharge of pollutants to the environment is avoided.
An important example of such hybridization is the endothermic steam-gasification of petroleum derivatives and residues (petcoke) to synthesis gas (syngas), represented by the simplified net reaction:
x
CHxOy + (1 - y)H2O ^ (2 +1 - y)H2 + CO
where x andy are the elemental molar ratios of H/C and O/C in petroleum tar, respectively. In a previous paper, the chemical thermodynamics and reaction kinetics of reaction were examined [1].
With regard to refinery residues (bottoms), these can take several forms depending on the design on the refineries and their products. In particular, our study comprises one type of these refinery residues: solid materials such as coke which is a by-product from the processing of heavy and extra-heavy oils using delay-coking technology. Application of these technologies is resulting in increased yields of low value refinery residues such as residual fuel oil, coke and petroleum tar, furthermore stringent environmental regulations appears to be reducing the markets for these residues - particularly petroleum coke [2].
The project of solar petroleum coke gasification is a joint cooperation between the company Petroleos de Venezuela (PDVSA), the Eidgenossische Technische Hochschule (ETH) in Zurich / Switzerland, and the Centro de Investigaciones Energeticas, MedioAmbientales y Tecnologicas (Ciemat) in Spain. The primary goal is to develop a clean technology for the solar gasification of petroleum coke and other heavy hydrocarbons.
The project is divided into three phases. In a first step, after performing in-depth studies of the thermodynamic and kinetic behaviour, a small 5 kW prototype was tested in the Solar Furnace of PSI / Switzerland [1]. Goal was to demonstrate the feasibility of the solar gasification, to determine critical process parameters, to identify possible difficulties, and finally to get a solid data base for the scale up step in phase 2. One important result was the decision to use slurry for the feeding of the reactor [3].
In phase 2, the design, construction, and operation of a 500 kW reactor are foreseen. The design of the reactor itself was done by ETH and upstream and downstream system by Ciemat. Construction is managed by Ciemat, and operation will be done at the SSPS-tower at the Plataforma Solar de Almeria during 2008. In phase 3 finally, a 50 MW solar gasification plant located in Venezuela will be designed.
