Hydrogen Production by Steam-Gasification of Petroleum Coke

Participants:

• PDVSA (Venezuela)

• CIEMAT (E)

• ETH/PSI (CH)

Contact:

• Manuel Romero, manuel.romero@ciemat.es

• Juan Carlos de Jesus, dejesusjc@pdvsa.com

• Aldo Steinfeld, aldo.steinfeld@eth.ch

Funding:  

• PDVSA-CIEMAT-ETH

Duration:

• January 1, 2003 - December 31, 2007

Scheme of solar chemical reactor configuration for the steam-gasification of petcoke, featuring a continuous gas-particle vortex flow confined to a cavity receiver and directly exposed to concentrated solar radiation. The reactants are injected as a liquid slurry of petcoke particles and water.

Background

The solar steam-gasification of petroleum coke, in which petcoke is the chemical source for H2 production and concentrated solar power is the energy source for process heat, offers a viable route for fossil fuel decarbonization and creates a transition towards solar hydrogen. The advantages of supplying solar energy for process heat are four-fold: 1) the calorific value of the feedstock is upgraded; 2) the product gases are not contaminated by the byproducts of combustion; 3) the need for a pure oxygen source is eliminated; and 4) polluting emissions into the environment are avoided.

Objectives

• The project aims at experimental demonstration of the technology in a 500 kWth solar reactor.

Achievements in 2006

The solar reactor configuration is depicted in ‎Figure 4.3. The reactor features a continuous vortex flow of steam laden with petcoke particles confined to a cavity receiver and directly exposed to concentrated solar radiation. A 5 kWth prototype reactor was tested in PSI’s solar furnace in the 1300-1800 K range. Petcoke-water slurry was continuously injected into a solar cavity-receiver to create a vortex flow. For a nominal reactor temperature of 1500 K, a water-petcoke molar ratio of 4.8, and a residence time of 2.4 s, maximum petcoke conversion was 87%. Typical syngas composition was 62% H2, 25% CO, 12% CO2, and 1% CH4. Reactor scale-up to 500 kWth solar power and testing is in progress at the Plataforma Solar de Almería.
The solar reactor was modeled by means of a two-phase formulation that couples radiative, convective, and conductive heat transfer to the chemical kinetics. A unique feature of the reactor is that the gas-particle flow is directly exposed to concentrated solar radiation, providing efficient radiative transfer to the reaction site for the high-temperature endothermic process. The governing mass, momentum, and energy con-servation equations were solved by applying Monte-Carlo, two-flux, and finite-volume techniques. Validation was accomplished by comparing the numerically calculated temperatures, product composition, and chemical conversions with the experimental measurements found from testing a 5 kWth prototype reactor in the PSI solar furnace.

Publications

• Trommer D., Noembrini F., Fasciana M., Rodriguez D., Morales A., Romero M., Steinfeld A. (2005) Hydrogen production by steam-gasification of petroleum coke us-ing concentrated solar power – I. Thermodynamic and ki-netic analyses, Int. J. Hydrogen Energy 30, 605-618.

• Lipinski W., Z’Graggen A., Steinfeld A. (2005) Transient radiation heat transfer within a non-gray non-isothermal absorbing-emitting-scattering suspension of reacting particles undergoing shrinking, Numerical Heat Transfer, Part B, 47, 443-457.