Production Of Superheated Steam Research Articles

Performance assessment of USC power plants integrated with CCS and concentrating solar collectors

This paper focuses on the evaluation of the potential benefits arising from the integration of Ultra Super Critical (USC) steam power plants with Carbon Capture and Storage (CCS) and concentrating solar systems. In particular, it reports on a comparative performance analysis of different integrating approaches, based on the design of the solar field to produce low-pressure saturated steam for the CCS solvent regeneration process and intermediate-pressure saturated and superheated steam for the introduction in the steam cycle. For the two different technical solutions, the comparative study calculates the increase in the annual energy production and net efficiency due to the solar energy contribution as a function of solar field size and for two different CO2 removal efficiencies.The study demonstrates that the integration of concentrating solar collectors can partially offset the efficiency penalties due to CO2 removal in USC power plants and that the most efficient approach is based on the production of superheated steam while lesser benefits can be achieved by producing low-pressure saturated steam for the solvent regeneration process. It also demonstrates that the introduction of the steam produced by the solar field greatly affects the performance of the power plant that operates in an “off design” mode. For this reason, to avoid an excessive increase in the turbine steam mass flow, the solar energy contribution to the annual electricity production cannot exceed 2–3%. Overall, integration with the solar section can improve the efficiency of the USC-CCS power plant by about 1 percentage point.Finally, the results of a preliminary economic analysis show that the solar assisted USC-CCS configuration may be able to operate with competitive solar energy production costs, especially with reduced solar field costs. In particular, the marginal levelized energy production cost of the most efficient solar assisted USC-CCS configuration is lower than that of the reference USC-CCS power plant for solar field costs lower than 110–115€/m2.

A Theoretical Study of Two Novel Concept Systems for Maximum Thermal-Chemical Conversion of Biomass to Hydrogen

Two concept systems that are based on the thermochemical process of high-temperature steam gasification of lignocellulosic biomass and municipal solid waste are introduced. The primary objectives of the concept systems are 1) to develop the best scientific, engineering, and technology solutions for converting lignocellulosic biomass, as well as agricultural, forest and municipal waste to clean energy (pure hydrogen fuel), and 2) to minimize water consumption and detrimental impacts of energy production on the environment (air pollution and global warming). The production of superheated steam is by hydrogen combustion using recycled hydrogen produced in the first concept system while in the second concept system concentrated solar energy is used for the steam production. A membrane reactor that performs the hydrogen separation and water gas shift reaction is involved in both systems for producing more pure hydrogen and CO2 sequestration. Based on obtaining the maximum hydrogen production rate the hydrogen recycled ratio is around 20% for the hydrogen combustion steam heating system. Combined with pure hydrogen production, both high temperature steam gasification systems potentially possess more than 80% in first law overall system thermodynamic efficiencies.

Production of superheated steam from vapor-dominated geothermal reservoirs

Vapor-dominated geothermal systems such as Larderello, Italy, The Geysers, California, and Matsukawa, Japan yield dry or superheated steam when exploited. Models for these systems are examined along with production data and the thermodynamic properties of water, steam and rock. It is concluded that these systems initially consist of a water and steam filled reservoir, a water-saturated cap rock, and a water or brine-saturated deep reservoir below a water table. Most liquid water in all parts of the system is relatively immobilized in small pores and crevices; steam dominates the large fractures and voids of the reservoir and is the continuous, pressure-controlling phase. With production, the pressure is lowered and the liquid water boils, causing massive transfer of heat from the rock and its eventual drying. Passage of steam through already dried rock produces superheating. After an initial vaporization of liquid water in the reservoir, the decrease in pressure produces increased boiling below the deep water table. With heavy exploitation, boiling extends deeper into hotter rock and the temperature of the steam increases. This model explains most features of the published production behavior of these systems and can be used to guide exploitation policies.