Thermal conversion processes

Chemical Processes. Biological—biochemical and thermal conversion processes are chemical processes, too, but a few specific chemical processes are mentioned separately because they are directed more to conventional chemical processing and production. These processes have been grouped together as chemical processes. 

Typical characterization of the thermal conversion process for a given molecular precursor involves the use of thermogravimetric analysis (TGA) to obtain ceramic yields, and solution NMR spectroscopy to identify soluble decomposition products. Analyses of the volatile species given off during solid phase decompositions have also been employed. The thermal conversions of complexes containing M - 0Si(0 Bu)3 and M - 02P(0 Bu)2 moieties invariably proceed via ehmination of isobutylene and the formation of M - O - Si - OH and M - O - P - OH linkages that immediately imdergo condensation processes (via ehmination of H2O), with subsequent formation of insoluble multi-component oxide materials. For example, thermolysis of Zr[OSi(O Bu)3]4 in toluene at 413 K results in ehmination of 12 equiv of isobutylene and formation of a transparent gel [67,68]. 

Uncertainties with the availability and suitability of biomass resources for energy production are primarily due to their varying moisture content, and to a lesser degree to their chemical composition and heating value. As the moisture content of biomass increases, the efficiency of thermal conversion process decreases. At some point more energy may have to be expended to dry the biomass than it contains. Uncertainties can be reduced by conducting a detailed chemical and physical analysis of the biomass sources. 

Ensuring a constant feed supply is very important, because most of the biomass is only available on a seasonal basis. In such cases continuous operation of the conversion facility will require either extensive long-term storage of the feedstock or a feed reactor that is flexible enough to accommodate multiple feedstocks. Most thermal conversion processes demand a finely divided, substantially dry feed and therefore some pre-treatment is required to match the feedstock to the process. The main pre-treatment operations are [19] ... 

Pyrolysis, gasification, and combustion are typical thermal conversion processes for biomass. These processes are compared and contrasted in TABLE 12-4. 

TABLE 12-4. Biomass Thermal Conversion Process Comparison... 

The products contain lower amounts of asphaltene-related material and have lower carbon residues. As with other thermal conversion processes, the products are cumulatively lower in sulfur than the original feedstocks and there are indications that at least 60% of the original sulfur is removed during the process. 

Continuous contact coking a thermal conversion process in which petroleum-wetted coke particles move downward into the reactor in which cracking, coking, and drying take place to produce coke, gas, gasoline, and gas oil. 

Decarbonizing a thermal conversion process designed to maximize coker gasoil production and minimize coke and gasoline yields operated at essentially lower temperatures and pressures than delayed coking (q.v.). 

Thermal Conversion Process Resource Recovery Corporation, Inc. Thermo-Depolymerization Process, LLC Renewable Energy solutions, LLC... 

In principle, biomass resources can be converted using any of the biochemical or thermal conversion processes. 

SiC fiber was produced from polycarbosilane (PCS) by Yajima et al. " in 1975, which is the earliest case of organosilicon polymer utilization for an industrial structural material. In the Yajima process, PCS was mainly synthesized from polydimethylsilane (PDS) by a thermal conversion process using an autoclave or an open reflux system. This is the commonly available PCS. Its melt spinability, solubility in various orgaiuc solvents, and stability for storing at room temperature are critically important for industrial uses. 

It is normally not necessary to reduce the water content of high-moisture-content or wet biomass feedstocks for microbial conversion processes. This contrasts with thermal conversion processes such as combustion. Dry biomass burns at higher temperatures and thermal efficiencies than wet biomass. For... 

Knowledge of the effects of various independent parameters such as biomass feedstock type and composition, reaction temperature and pressure, residence time, and catalysts on reaction rates, product selectivities, and product yields has led to development of advanced biomass pyrolysis processes. The accumulation of considerable experimental data on these parameters has resulted in advanced pyrolysis methods for the direct thermal conversion of biomass to liquid fuels and various chemicals in higher yields than those obtained by the traditional long-residence-time pyrolysis methods. Thermal conversion processes have also been developed for producing high yields of charcoals from biomass. 

If biomass is subjected to the ASTM D 3172 procedure for determination of fixed carbon, chemical transformation of a portion of the organic carbon in biomass into carbonaceous material occurs as described here. All of the fixed carbon determined by the ASTM procedure is therefore generated by the analytical method. Furthermore, the amount of fixed carbon generated depends on the heating rate used to reach biomass pyrolysis temperatures and the time the sample is subjected to these temperatures. Nevertheless, such analyses are valuable for the development of thermal conversion processes for biomass feedstocks. But application of the ASTM procedures to biomass might more properly be called a method for determination of pyrolytic carbon or coking yields. In the petroleum industry, the Conradson carbon (ASTM D 189, differ-... 

The design of the burner allows a staging of the process by means of temperatures and combustion air. To achieve the required goals the following boundary conditions needed to be met in the thermal conversion processes ... 

This paper describes che project development process and attempts to highlight the commercial climate in which an energy project, based on a thermal conversion process, has to become established and survive. The detail of the thermal conversion process itself, ie the technical process, is not relevant to the conception or the understanding of the project development process, ie the nnancial process, although the former process will have a major influence on the project s risk profile which will come under intense scrutiny in the latter process. 

The commercial world of electricity supply, in which the thermal conversion process hopes to find an application, is changing rapidly in the developed world and the support and sustenance that prototype processes might have received in years gone by from central authorities is now vanishing. 

The drive to utilize more non-fossil fuels in electricity production, in order to meet climate change accords, is likely to provide the main stimulus to technological development of new thermal conversion processes which can utilize biomass or waste products as a feedstock in the developed world. 

Della Rocca, P.A. (1998) Study on biomass thermal conversion processes. DPhil thesis, Universidad de Buenos Aires. 

ABSTRACT The volatility of tars from pyrolysis of biomass and biomass-derived materials is of special interest. This interest is related to the question whether or not biomass tar evaporation has a significant effect on the total rate escape of tar from pyrolyzing substance and therefore on pyrolysis kinetics. In fact, in many practical applications (especially in fossil fuel thermal conversion processes), tar vaporization is known to be an important step during pyrolysis that influences both yield and composition of pyrolysis products. 

As consequence of the fact that only the organic materials are shredded, both glass bottles and cans remain intact. Maintenance and power consumption are also significantly reduced. In addition, the extremely low glass-content of the RDF minimizes equipment abrasion and reduces potential slagging problems in the thermal conversion process. 

The coefficients of the Arrhenius equation determined in this manner, are the basic data for the calculation of the kinetics of pyrolysis (crack) reactions and therefore also the basis for the choice of process conditions, such as pre-setting of reactor temperatures, residence times etc. in thermal conversion processes. 

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