Liquefaction continued

Work has also continued on the solvent-refined coal + hydrocracking concept (the NT.SL, or non-integrat-ed, two-stage liquefaction process), and a pilot plant was operated by Amoco, DOE and the Electric Power Research Institute (EPRI) from 1974 to 1992. 

In conclusion, the technology of total liquefaction of apple allows to work with a continuous process with less labour and faster than with a classical one, to get a high and constant yield during the whole processing season at a very high level (93- 95%), to get a pulp with a low content of solids (about 20% in volume) which can be centrifuged instead of pressed (lower investment in equipment), to decrease the quantity of waste pomace, to decrease the production costs. Liquefaction technology allows to process different fruits with the same process, at last to liquefy fruits for which no equipment had been developed to extract the juice or for which the use of pectinases did not allow to get juice such as tropical fruits. 

The remainder of this paper can be restricted to coals of North America, since this is the area for which we have data and in any case other contributors to this collection will deal with the coals of their own areas. The first statement above needs qualification we ourselves have no liquefaction data on Canadian coals, but Ignasiak et al. (48) present some in this collection.Relying, as in the earlier part of this paper, on geological information, we can say that the strata of the North Great Plains and Rocky Mountain provinces continue north into Canada, as does the Pacific province. Nova Scotia contains some Carboniferous coals related to those in the Eastern province. 

The reactive role of liptinite macerals in liquefaction has been partially documented (50,68). However, recent work has shown that unaltered sporinite often is encountered in the residues from both batch and continuous liquefaction runs. For example, sporinite was a common component in the residues of a high volatile A bituminous coal after hydrogen-transfer runs at 400° for 30 minutes (70). In spite of the relative unreactivity of the sporinite in this instance, the vitrinite clearly had reacted extensively because vitroplast was the predominant residue component. The dissolution rate of sporinite from some coals, even at 400°C, may be somewhat less than that of vitrinite. 

CCDC built a continuous short residence time coal liquefaction unit with throughput of about 4.5 kg/hr of coal. The SRC unit consisted of a short residence time reactor constructed from 53.3 m of high pressure tubing having an ID of 0.516 or... 

In addition to continuous bench-scale work, CCDC carried out a rather extensive laboratory program involving the use of the microautoclave reactor. The program developed tests to compare the activities of different solvents. These tests quickly evaluated a solvent so that the performance under coal liquefaction conditions could be predicted. The tests are now used at the Wilsonville SRC Pilot Plant as a means of determining when stable operation has been achieved. 

Continuous Bench-Scale Experimentation With encouraging results obtained from microautoclave tests, experimentation emphasis moved to the bench-scale unit Here the concept of adding Light SRC to the recycle solvent on a continuous basis was tested Earlier work (j>) performed on short contact time coal liquefaction showed Indiana V coal to be out-of-solvent balance Also the operability of the continuous bench-scale SRT unit was highly dependent upon the quality of the solvent ... 

Continuous Short Residence Time Experimentation After determining the effect of Light SRC addition to a conventional SRC-I operation, experimentation moved to determining the effect of Light SRC addition on short residence time coal liquefaction performance ... 

The explosive properties of liquid methane-oxygen mixtures were determined [8], Dining investigation of an explosion in a portable air liquefaction-separation plant, hydrocarbon oil was found in a silica filtration bed [9], The mechanism of slow heterogeneous accumulation of hydrocarbons dissolved in trace amounts in liquid oxygen on the liquid evaporator surfaces is discussed. It was concluded that months of continuous evaporation would be required to attain explosion-hazardous levels in real evaporators [10],... 

The concentration of chlorine in the total permeate continuously decreases as the process continues. This is illustrated by Fig. 7.5, showing the percentage of the nitrogen originally present which accompanies permeation of 80% and 90% of the chlorine. The purity of the gas is a measure of its utility in further processing. One option is to recycle the permeate to the liquefaction process. This is discussed in more detail in Section 7.3.3. 

Autoclaves provide reactors which can be used readily to acquire data from coal liquefaction studies but are less representative of likely commercial plant tyi reactors than small scale continuous bed-type reactors. Ideally comparisons between reactors are best made by carrying out experiments in various designs of reactors under similar reaction conditions, but, in order to cover the full range of designs adequately, a larger expenditure on equipment (beyond the budgets of most laboratories) would be necessary. However, steps can be taken to cover the... 

The large amount of energy necessary for liquefaction, that is, 40% of the upper heating value, makes liquid hydrogen not an energy-efficient storage medium. Furthermore, the continuous boil-off of hydrogen limits the possible applications... 

After World War II, direct liquefaction of coal became uneconomical as the use of lower-cost petroleum products became more widespread. However, the German process of indirect coal liquefaction, the Fischer-Tropsch process, continued to hold some interest. The Fischer-Tropsch process first involved production of a carbon monoxide and hydrogen-rich synthesis gas by the controlled gasification of coal followed by a catalytic reaction process to yield a valuable mixture of hydrocarbon products. Simplified Fischer-Tropsch reactions are shown by the following equations ... 

Catalysts in coal liquefaction are used in moving-bed, ebulating-bed, and fixed-bed processes. Disposable iron catalysts must be used in moving beds. More expensive Co-Mo and Ni-Mo catalysts are used in either ebulating or fixed beds, and catalyst deactivation rates and ultimate lifetime are of concern (80, 81). In ebulating beds, a small portion of fresh catalyst is continuously fed to balance the catalyst being purged. 

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