Supercritical Fluid Technologies within Chematur Engineering Ab

The Chematur Engineering group of companies is presented, briefly describing the business areas within the group. Activities in the field of supercritical fluids are given. The range of equipment as well as applications for supercritical carbon dioxide and supercritical water oxidation are presented. The Chematur Engineering demonstration plant for SCWO is described in detail and results from some performed treatability studies are given, including de-inking sludge and sewage sludge. The results clearly show that SCWO is a very effective method for treatment of sludge. Introduction The Chematur Engineering Group is a group of companies delivering process plants to the chemical industry based on proprietary as well as licensed technologies. The group is headquartered in Karlskoga, Sweden with subsidiaries in Finland (Chematur Ecoplanning), Sweden (Electrocell & Supercritical Fluid Technology Sweden) and USA (Weatherly). Production plants for the following technologies are offered by the group: The Supercritical Fluids business area is rapidly expanding and the area where most of the development resources are used. There are two key thrust technologies in this area. The first is the use of supercritical fluids to enhance reactions and separations. The current emphasis is on using supercritical carbon dioxide (scCO2). With respect to scCO2 there is a range of units, from the pilot unit with a flow capacity of 50 kg/h up to large units with a CO2 flow of 10 ton/h. All units are as standard designed for a max. pressure of 500 bar. Applications include environmentally friendly degreasing of metal parts, the RotowasherTM, extraction of nutraceutical extract from e.g. herbs, the XtractorTM series, and the use of scCO2 as solvent for carrying out chemical reactions, the Swan SCFTM unit (1). The Swan SCF multi purpose unit is the first of its kind that has been built and it offers true continuous production of fine and speciality chemicals on a large scale. The client, Thomas Swan & Co., is targeting areas like hydrogenation, acid catalysed reactions and hydroformylation. The engineering was very challenging with design pressure and temperature at 500 bar and 200 °C. Explosives & Propellants Nitric Acid Fertilizers Isocyanates (TDI, MDI) Nitroaromatics Ethanol and its derivatives Hydrogen peroxide Acid concentration and recovery systems Evaporation & Crystallisation Electrochemistry Supercritical Fluids Presented at the 3 Disposal Conference, Karlskoga, Sweden, November 10-11, 2003 Page 2(9) Copyright © Chematur Engineering AB Figure 1 shows the multipurpose pilot unit, figure 2 shows the novel continuous reaction plant installed at Thomas Swan & Co, UK and figure 3 a production plant for aromas extraction. The Rotowasher unit, similar in appearance to the Xtractor 500/50 unit, features a revolutionary rotating cleaning basket to enhance mass transport and cleaning performance. It has been in successful operation at Viking Sewing Machines, Huskvarna, Sweden since 1999, cleaning small sintered metal parts (2,3). Figure 1 scCO2 Pilot plant, XtractorTM 500/50 Figure 2 Swan SCFTM chemical reaction system Figure 3 XtractorTM 500/1000, 1000 kg/h, 500 bar scCO2 extraction plant Presented at the 3 Disposal Conference, Karlskoga, Sweden, November 10-11, 2003 Page 3(9) Copyright © Chematur Engineering AB The second thrust area and currently where the largest effort is being expended is in Supercritical Water Oxidation (SCWO). A state of the art demonstration plant has been built in Karlskoga, Sweden. Chematur Engineering has made every attempt to construct the demonstration plant in the same way as a commercial scale plant would be constructed. This enables Chematur to gain experience regarding the best engineering solutions, taking into consideration all the key aspects such as corrosion, fouling, strength of construction material, manufacturing and permitting. Supercritical water oxidation To achieve a sustainable society, future pollution control must include the concept of complete destruction of toxic substances and sludges. Two options exist for the complete destruction of toxic or persistent substances in wastewaters and organic sludges. These two options are incineration and supercritical water oxidation. SCWO has proven to be a very promising method for many different wastewaters and sludges. SCWO utilises the unique features of water in its supercritical state (SCW), above 221 bar and 374 °C. SCW is, contrary to normal water, totally miscible with organic substances and gases. This feature eliminates all mass transport limitations and together with the relatively high temperature of the process, 400-600 °C, it ensures rapid and complete reactions. A destruction efficiency of 99.9 % or better is typically achieved in about one minute reaction time. All substances are destroyed irrespectively of their structure and in fact it has been reported (4) that SCWO destroys dioxins found in fly ashes from conventional incineration. Furthermore, no NOx or SOx is formed so there is no effluent gas cleaning requirements. As a matter of fact there is not even a chimney as effluent gas is released at close to ambient conditions. Finally, the process is normally autothermal and heat of oxidation can be recovered in an effective way even in quite diluted systems, containing as much as 90 to 95 % water. Chematur Engineering expanded its activities in the field of environmental protection in 1995 with a license agreement for SCWO, signed with Eco Waste Technologies (EWT). In 1999 Chematur acquired the EWT technology on a world-wide basis. Chematur is now a world leader in this field and the Chematur SCWO process is marketed under the trade names Aqua Critox, Aqua ReciTM and AquaCat. In early 1998 Chematur inaugurated its 250 kg/h SCWO demonstration facility and since then several successful treatability tests have been performed. The Chematur demonstration unit is built as a tool for commercialising the technology, by showing potential users that this method is applicable for their wastes. During these demonstration runs several successful and extensive treatability tests with actual wastes have been performed. The demonstration plant A simplified flow sheet of the plant is shown in figure 4. The bottom outlet from the feed tank is connected to a grinder pump. This eliminates the risk of big particles entering the high-pressure pump. It also provides mixing of the wastewater by means of a recirculation loop. The plant is equipped with two different high pressure feed pumps, one for clear liquids and one for dispersions and sludges. The high pressure feed pumps raise the feed pressure to about 250 bar and pumps the feed through the SCWO system. Presented at the 3 Disposal Conference, Karlskoga, Sweden, November 10-11, 2003 Page 4(9) Copyright © Chematur Engineering AB The feed enters the tube side of a double-pipe economiser where it is preheated by the reactor effluent. After leaving the economiser, the feed enters the heater. From the heater outlet, the hot feed enters the reactor. In the reactor, oxygen is injected to start the oxidation reaction. The oxidation reaction generates heat and, as a result, the reactor temperature increases. In some cases, the inlet feed concentration may be too high for complete oxidation of the organic material to occur in one step without exceeding the reactor’s design temperature, 600 oC. In these cases the waste may be oxidised in two stages, using a proprietary and patented method. At the beginning of the second stage, quench water is added with the oxygen. The water cools the effluent from the previous stage enough to allow the additional oxygen to continue the oxidation reaction without exceeding the temperature limit.