The oxidation of harmful organic compounds contained in aqueous waste effluents known as super critical water oxidation, SCWO, has been worked out since the 1980s. This highly efficient end of the pipe process operates at pressures and temperatures above 221 bar and 374 C, the critical point of water. R&D experience and the technological state including economical and regulatory aspects are reviewed and further R&D needs are discussed in this article. Future applications are also seen in coupling supercritical CO 2 extraction with oxidation to treat contaminated materials and in supercritical water gasification, SCWG, to convert biomass and organic wastes to hydrogen.
Biofuels of the second generation can contribute significantly to the replacement of the currently used fossil energy carriers for transportation fuel production. The lignocellulosic biomass residues used do not compete with food and feed production, but have to be collected from wide‐spread areas for industrial large‐scale use. The two‐stage gasification concept bioliq offers a solution to this problem. It aims at the conversion of low‐grade residual biomass from agriculture and forestry into synthetic fuels and chemicals. Central element of the bioliq process development is the 2–5 MW pilot plant along the complete process chain: fast pyrolysis for pretreatment of biomass to obtain an energy dense, liquid intermediate fuel, high‐pressure entrained flow gasification providing low methane synthesis gas free of tar, hot synthesis gas cleaning to separate acid gases, and contaminants as well as methanol/dimethyl ether and subsequent following gasoline synthesis. After construction and commissioning of the individual process steps with partners from industry, first production of synthetic fuel was successfully achieved in 2014. In addition to pilot plant operation for technology demonstration, a research and development network has been established providing the scientific basis for optimization and further development of the bioliq process as well as to explore new applications of the technologies and products involved. WIREs Energy Environ 2017, 6:e236. doi: 10.1002/wene.236
This article is categorized under:
Bioenergy > Science and Materials
Bioenergy > Systems and Infrastructure
Supercritical Water Oxidation (SCWO) was studied at the Institute of Technical Chemistry, ITC-CPV. SCWO is a high-pressure-high-temperature process with high space-time yield to destroy organic hazardous compounds present in industrial waste effluents to form water and carbon dioxide. Heteroatoms were mineralized to the corresponding acids or salts; nitrous oxides formation was suppressed due to low oxidation temperatures. Results obtained in a tube reactor system showed destruction efficiency (D.E.) values close to 100% of the organic content, but indicate plugging and corrosion of the tube when treating salt and/or acid containing solutions. Hence, the application of SCWO process is limited. To enlarge the potential of SCWO process for industrial applications, new reactor concepts were developed. Among these, the transpiring wall reactor (TWR) concept is considered to have very good prospects to overcome these limitations. The TWR installed at ITC-CPV is designed for T 5 630°C, P 5 32 MPa, wastewater flow rate 5 20 kg/h, air feed rate 5 40 kg/h, transpiring water flow rate 5 20 kg/h, and quench water flow rate 5 40 kg/h. The TWR can be fed with suspensions of up to 10 wt. %. SCWO experiments with model compounds and industrial waste effluents or waste suspensions of up to 6 wt. % solid material content resulted in D.E. values of up to 99.99%. However, feeding of effluent suspensions may become less reliable at low feed flow rates. Computer simulations of the experiments using the CFD code CFX4 complement the SCWO studies. The Institute for Reactor Safety, IRS, performed 2D and 3D steady-state calculations to get an insight into local flow conditions and species concentrations inside the reactor and around the transpiring wall-information that are hardly accessible to measurements. For validation of the computational results, local temperatures, and the destruction efficiency can be compared with the experimental data. This is illustrated for an experiment in the ITC-TWR with the model compound ethanol.
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