Gasification residue

There are environmental impacts to consider in connection with biomass production, collection (e.g. by forestry) and transport to gasification site, from the gasification and related processes and finally from the use made of the gas. The gasification residues, ash, char, liquid wastewater, and tar have... 

Complex Mixture Extraction. Analytical SFE can also be used for complex mixture sample preparation. Typical examples using hazardous waste samples are described below. Sample A was a soil boring contaminated with coal gasification residuals and sample B was from a waste stream from a treatment facility. The major objective of these studies was to compare the extraction abilities (e.g., amount of material extracted) of three different fluid systems using approximately four-gram aliquots of the samples. The specific fluid systems, the extraction conditions, and the percentage of the total mass of material extracted from each sample are listed in Table II. 

FIGURE 3.14 Digital images of nitrogen gasification residues from three nanocomposites a) PP/mass fraction 5% MMT b) PP/mass fraction 15% PP-g-MA/mass fraction 2% MMT (c) PP/mass fraction 15% PP-g-MA/mass fraction 5% MMT. 

FIGURE 3.16 Gasification residue of PP/PP-g-MA/MMT with 7.7% PP-g-MA and MMT. See insert for color representation of figure.)... 

Coal can be converted to gas by several routes (2,6—11), but often a particular process is a combination of options chosen on the basis of the product desired, ie, low, medium, or high heat-value gas. In a very general sense, coal gas is the term appHed to the mixture of gaseous constituents that are produced during the thermal decomposition of coal at temperatures in excess of 500°C (>930°F), often in the absence of oxygen (air) (see Coal CONVERSION PROCESSES, gasification) (3). A soHd residue (coke, char), tars, and other Hquids are also produced in the process ... 

G. A. White We have looked at a case consisting of a Koppers-Totzek gas, at essentially atmospheric pressure, in combination with the COED liquefaction process. We considered the residue gas that came from gasification at atmospheric pressure, methanated it at atmospheric pressure, and took out C02 at atmospheric pressure before compression. That was the minimum cost for our system. It is obvious that each system will have some difference in economics, depending on what you can achieve by methanation. 

Texaco gasification is based on a combination of two process steps, a liquefaction step and an entrained bed gasifier. In the liquefaction step the plastic waste is cracked under relatively mild thermal conditions. This depolymerisation results in a synthetic heavy oil and a gas fraction, which in part is condensable. The noncondensable fraction is used as a fuel in the process. The process is very comparable to the cracking of vacuum residues that originate from oil recycling processes. 

The first reactor is a gasification (or fast pyrolysis) reactor in which PVC-rich waste is converted at 700-900 °C with steam into a gaseous product (fuel gas and HCl) and residual tar. 

The second reactor is a combustor that bums the residual tar to provide the heat for gasification. 

The residual fraction of Zn after combustion without steam at 1273 K was about 80 %, meanwhile the residual fraction after pyrolysis was about 30 %. Also at 1423 and 1573 K, the residual fraction of Zn after combustion was greater than in the case of pyrolysis. This was considered that under N2 atmosphere, Zn in coal was released as the compound that should be volatized at each temperature, however under air atmosphere, a part of Zn were oxidized into ZnO (mp 2521 K) which was very stable at high temperature. When the combustion was carried out with additional steam, the residual fraction of Zn was same as the cases in the absence of steam. However, the residual fraction of Zn after steam gasification was about 60 %, greater than the residual fraction after pyrolysis (about 30 %) and smaller than the residual fraction after combustion (about 80 %). This was considered that under steam gasification, a part of Zn, which should be emitted at 1273 K, was oxidized into ZnO by additional steam. 

We compared and discussed about the release behavior of trace metals from coal under the condition of coal combustion, pyrolysis and steam gasification. Under the condition of combustion, the residual fraction of Zn and Sb was grater than in case of pyrolysis and the residual fraction of Se was smaller. Because a part of trace metals in coal was oxidized during combustion. Moreover the release of Se and Sb was promoted when steam existed in atmosphere, and the release of Hg was suppressed. 

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