Waste liquefaction

Chemical. A chemical route is followed by two processes which are similar, the U.S. Bureau of Mines (BuMines) waste liquefaction process and the Worcester Polytechnic Institute (WPI) hydrogenation process. 

Feasibility Study for a Demonstration Plant for Waste Liquefaction and Coal-Waste Coprocessing, US DOE, Contract No. DE-FC22-93PC93053, The Consortium for Eossil Fuel Science, 1 August 1995-30 June 1999. P.I., Gerald P. Huffman. 

Liquefaction. Siace the 1970s attempts have been made to commercialize biomass pyrolysis for combiaed waste disposal—Hquid fuels production. None of these plants were ia use ia 1992 because of operating difficulties and economic factors only one type of biomass Hquefaction process, alcohohc fermentation for ethanol, is used commercially for the production of Hquid fuels. 

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. 

This paper outlines waste plastic liquefaction technology, and discusses its use in the operation of a demonstration plant. The following aspects are considered plastics suitable for liquefaction, basic principals of liquefaction technology, the liquefaction process, examples, results, and conclusions. 4 refs. 

Polymers have inherently high hydrocarbon ratios, making liquefaction of waste plastics into liquid fuel feedstocks a potentially viable commercial process. The objective is to characterise the thermal degradation of polymers during hydrogenation. LDPE is studied due to its simple strueture. Isothermal and non-isothermal TGA were used to obtain degradation kinetics. Systems of homopolymer, polymer mixtures, and solvent-swollen polymer are studied. The significant variables for... 

The use is described of a foamed Styrol liquefaction treatment machine which has been developed as an environmentally acceptable method of recovery of waste foamed styrene.Details are given of the liquefaction treatment which consists of four processes crushing and removal of foreign substances heating, gasification and pyrolysis cooling and liquefaction and the recycling of resultant liquid as solvent for use in the first three processes. 

This paper discusses in depth advanced technologies for recycled materials from solid waste streams. Chemical depolymerisation, thermal depolymerisation, pyrolytic liquefaction, pyrolytic gasification, partial oxidation, and feedstock compatibility are all explained. The economic feasibility of the methods are considered. 

Smith, R. Overview of Feedstock Recycling of Commingled Waste Plastics, Presentation at the consortium for fossil fuel Liquefaction Science, P " Annual Meeting, Pipestem. WV, August, (1995). 

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. 

It is to be noted that the difference in dissipation of energy between the thermal energy demanded by organic chemical hydrides and the mechanical energy by compression or liquefaction of hydrogen is quite significant because the former is supplied as waste heat, whereas the latter is lost at the site of hydrogen utilization for fuel cells or ICEs. 

The chlorine liquefaction plant comprises a bromine-removal column, a compression-condensation unit and a Tetra absorption/distillation unit (Fig. 14.2). Waste streams of chlorine are absorbed in diluted cell-liquor in the chlorine destruction area. As a result, the destruction liquid contains sodium chloride and less sodium hydroxide than is usual. Bromine from the bromine-removal column is also added to the chlorine destruction unit. The hypochlorite solution that is formed contains a reasonable amount of bromine and salts. However, it is a hypochlorite of non-marketable quality. 

In liquefaction systems wood and wood wastes are the most common fuelstocks. They are reacted with steam or hydrogen and carbon monoxide to produce liquids and chemicals. The chemical reactions that take place are similar to gasification but lower temperatures and higher pressure are used. Liquefaction processes can be direct or indirect. The product from liquefaction is pyrolytic oil which has a high oxygen content. It can be converted to diesel fuel, gasoline or methanol. 

Pyrolysis and liquefaction processes take an intermediate position in the sense that they maintain some larger molecular characteristics. Pyrolysis is a process in which the biomass material is quickly heated. The thermal cracking process, de-polymerizes waste or dry biomass and produces a liquid of complex composition (Fig. 1.17). 

Over the past two decades, considerable interest has been directed toward the conversion of cellulosic biomass (such materials as wood wastes, bagasse, and straw) into useful products, notably fuels. Several procedures, including fermentation, gasification, liquefaction, and pyrolysis, have been commercially applied to carbohydrates with various degrees of success. In order to use the polysaccharides present in lignocel-lulosic materials as a substrate in fermentation processes, pretreatments are necessary, such as with steam (under slightly acid conditions) or... 

Estimated capital cost (BuMines Liquefaction of waste)... 

Kaufman, J.A. and Weiss, A.H., "Solid Waste Conversion Cellulose Liquefaction", Report No. EPA-670/2-75-031, Nat. Environmental Research Center, Office of R D, U.S. Environmental Protection Agency, Cincinnati (1975). 

Very little information regarding the release of individual isomers was located in the literature. A coal liquefaction waste water effluent contained o- cresol at a concentration of 586 mg/L (Fedorak and Hrudey 1986). o-Cresol was detected at an average concentration of 1.1 pg/L for three samples of retort water from a shale oil production facility (Hawthorne and Sievers 1984). 

Waste water effluents from coal gasification facilities contained p-cresol at concentrations of 880 mg/L (Neufeld et al. 1985) and 5,120 ppb (Pellizzari et al. 1979). A coal liquefaction and a shale oil waste water effluent contained p-cresol at concentrations of 420 mg/L (Fedorak and Hrudey 1986) and 779 pg/L (Pellizzari et al. 1979), respectively, p- Cresol was emitted with the waste water of a poultry processing plant at concentrations ranging from 2.14 to 22.5 mg/L (Andelman et al. 1984). 

Coal liquefaction Fischer-Tropsch synthesis Synthesis of methanol Hydrogenation of oils Alkylation of methanol and benzene Polymerization of olefins Hydrogenation of coal oils, heavy oil fractions, and unsaturated fatty acids Adsorption of S02 in an aqueous slurry of magnesium oxide and calcium carbonate S02 or removal from tail gas Wet oxidation of waste sludge Catalytic desulfurization of petroleum fractions Wastewater treatment... 

---