Thermochemical processes

Thermochemical processes can produce hydrogen from water using high-temperature heat from either nuclear or concentrated solar power (CSP). There are over 100 thermochemical cycles for hydrogen production in the operating temperature range of 600-2500° C, where direct 

A key advantage of the S-I cycle is that the chemicals all are recycled there are no effluents. The key challenge is that the process requires high temperatures (800°C) and is still in the experimental stages. 

Schultz (2003) estimates the costs for a nuclear thermochemical facility utilizing the S-I cycle. The estimated capital cost for the hydrogen 

The CSP estimates rely heavily on assumptions for the nuclear thermochemical facility for cost estimates for the S-I cycle. Jones (2005) notes that a different cycle may be preferable for use with CSP technologies for several reasons including 

However, until the study for CSP is complete and performance and cost estimates for commercial plants developed, the best available information about thermochemical hydrogen production comes from the nuclear studies. Consequently, the basis for the CSP inputs used in this model is the same as for the nuclear thermochemical case - based on the sulfur-iodine cycle cost and performance information from Schultz (2003). 

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Lujuefaction. Eigure 21 outlines most of the biomass Hquefaction methods under development. There are essentially three basic types of biomass Hquefaction technologies, ie, fermentation, natural, and thermochemical processes. 

A. V. Bridgwater, ed.. Thermochemical Processing of Biomass, Butterworths, London, 1984, 344 pp. 

The quantitative computations were conducted using equilibrium thenuodynamic model. The proposed model for thermochemical processes divides layer of the sample into contacting and non-contacting zones with the material of the atomizer. The correlation of all initial components in thermodynamic system has been validated. Principles of results comparison with numerous experimental data to confirm the correctness of proposed mechanism have been validated as well. 

The rates of these reactions bodr in the gas phase and on the condensed phase are usually increased as the temperature of die process is increased, but a substantially greater effect on the rate cati often be achieved when the reactants are adsorbed on die surface of a solid, or if intense beams of radiation of suitable wavelength and particles, such as electrons and gaseous ions with sufficient kinetic energies, can be used to bring about molecular decomposition. It follows drat the development of lasers and plasmas has considerably increased die scope and utility of drese thermochemical processes. These topics will be considered in the later chapters. 

It will be seen tliroughout this discussion of thermochemical processes tlrat these require a knowledge of botlr thermodynamic and kinetic data for their analysis, and while kinehc theory obviously determines the rate at which any process may be caiTied out, the thermodynamic properties determine the extent to which the process can occur. 

The simplest system in which useful products are obtained by thermochemical processing involves the evaporahon of an element or elements in vacuum in order to produce thin hlms on a selected substrate. This process is usually limited to the production of thin hlms because of the low rates of evaporation of the elements into a vacuum under conditions which can be controlled. These rates can be calculated by the application of the kinetic theory of ideal gases. 

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