PDF Publication Title:
Text from PDF Page: 143
Chapter 3: Capture of CO2 131 The conventional two-stage CO conversion reduces the CO concentration in syngas (or in hydrogen) down to 0.2-0.3%. High temperature shift reactors operating between 400°C and 550°C and using an iron-chromium catalyst leave between 2% and 3% CO in the exit gas (dry basis). Copper-based catalyst can be used at temperatures from 180°C-350°C and leave from 0.2-1% CO in the exhaust. Lower CO content favours higher CO2 recovery. The gas is then cooled and hydrogen is produced by a CO2/H2 separation step. Until about 30 years ago, the CO2 was removed using a chemical (solvent) absorption process such as an amine or hot potassium carbonate and was rejected to atmosphere as a pure stream from the top of the regenerator. There are many of these plants still in use and the CO2 could be captured readily. separation of CO2 from SMR syngas above apply equally to the POX process. POX is a technology in common use today, the efficiency is lower than SMR, but the range of fuels that can be processed is much wider. Modern plants, however, use a pressure swing adsorber (PSA), where gases other than H2 are adsorbed in a set of switching beds containing layers of solid adsorbent such as activated carbon, alumina and zeolites (see the fuller description of PSA in Section 3.5.2.9). The H2 exiting the PSA (typically about 2.2 MPa) can have a purity of up to 99.999%, depending on the market need. The CO2 is contained in a stream, from the regeneration cycle, which contains some methane and H2. The stream is used as fuel in the reformer where it is combusted in air and the CO2 ends up being vented to atmosphere in the reformer flue gas. Hence, to capture CO2 from modern SMR plants would require one of the post-combustion processes described above in Section 3.3. Alternatively, the PSA system could be designed not only for high recovery of pure H2 but also to recover pure CO2 and have a fuel gas as the third product stream. For large-scale hydrogen production, the oxygen is supplied from a cryogenic air separation unit (ASU). The high investment and energy consumption of the ASU is compensated by the higher efficiency and lower cost of the gasification process and the absence of N2 (from the air) in the syngas, which reduces the separation costs considerably. However for pre-combustion de-carbonization applications, in which the hydrogen would be used as fuel in a gas turbine, it will be necessary to dilute the H2 with either N2 or steam to reduce flame temperature in the gas turbine combustor and to limit NOx emission levels. In this case the most efficient system will use air as the oxidant and produce a H2/N2 fuel mixture (Hufton et al. 2005) In a design study for a large modern plant (total capacity 720 tH2 d-1), the overall efficiency of making 6.0 MPa H2 from natural gas with CO2 vented that is without CO2 capture, is estimated to be 76%, LHV basis, with emissions of 9.1 kg CO2/ kg H2 (IEA GHG, 1996). The process can be modified (at a cost) to provide a nearly pure CO2 co-product. One possibility is to remove most of the CO2 from the shifted, cooled syngas in a ‘wet’ CO2 removal plant with an appropriate amine solvent. In this case the CO2-deficient syngas exiting the amine scrubber is passed to a PSA unit from which relatively pure H2 is recovered and the PSA purge gases are burned along with additional natural gas to provide the needed reformer heat. The CO2 is recovered from the amine solvent by heating and pressurized for transport. Taking into account the power to compress the CO2 (to 11.2 MPa) reduces the efficiency to about 73% and the emission rate to 1.4 kgCO2/kgH2, while the CO2 removal rate is 8.0 kgCO2/kgH2. 3.5.2.3 Auto-thermal reforming of gas and light hydrocarbons The autothermal reforming (ATR) process can be considered as a combination of the two processes described above. The heat required in the SMR reactor is generated by the partial oxidation reaction (2) using air or oxygen, but because steam is supplied to the reactor as well as excess natural gas, the endothermic reforming reaction (1) occurs in a catalytic section of the reactor downstream of the POX burner. The addition of steam enables a high conversion of fuel to hydrogen at a lower temperature. Operating temperatures of the autothermal process are typically 950-1050°C, although this depends on the design of the process. An advantage of the process, compared to SMR, is the lower investment cost for the reactor and the absence of any emissions of CO2 since all heat release is internal, although this is largely offset by investment and operating cost for the oxygen plant. The range of fuels that can be processed is similar to the SMR process, but the feed gas must be sulphur free. CO2 capture is accomplished as described above for the steam methane reforming. 3.5.2.4 Gas heated reformer Each of the three syngas generation technologies, SMR, ATR and POX produce high temperature gas which must be cooled, producing in each case a steam flow in excess of that required by the reforming and shift reactions. It is possible to reduce this excess production by, for example, using preheated air and a pre-reformer in an SMR plant. Another technique is to use the hot syngas, leaving the primary reactor, as the shell-side heating fluid in a tubular steam/hydrocarbon reforming reactor which can operate in series, or in parallel, with the primary reactor (Abbott et al., 2002). The addition of a secondary gas heated reformer will increase the hydrogen production by up to 33% and eliminate the excess steam production. The overall efficiency is improved and specific capital cost is typically reduced by 15%. Again, CO2 capture is accomplished as described previously for steam methane reforming. 3.5.2.5 Gasification of coal, petroleum residues, or biomass 3.5.2.2 Partial oxidation of gas and light hydrocarbons In the partial oxidation (POX) process (reaction 2), a fuel reacts with pure oxygen at high pressure. The process is exothermic and occurs at high temperatures (typically 1250°C-1400°C). All the heat required for the syngas reaction is supplied by the partial combustion of the fuel and no external heat is required. As with SMR, the syngas will be cooled, shifted and the CO2 removed from the mixture. The comments made on thePDF Image | CARBON DIOXIDE CAPTURE AND STORAGE
PDF Search Title:
CARBON DIOXIDE CAPTURE AND STORAGEOriginal File Name Searched:
srccs_wholereport.pdfDIY PDF Search: Google It | Yahoo | Bing
NFT (Non Fungible Token): Buy our tech, design, development or system NFT and become part of our tech NFT network... More Info
IT XR Project Redstone NFT Available for Sale: NFT for high tech turbine design with one part 3D printed counter-rotating energy turbine. Be part of the future with this NFT. Can be bought and sold but only one design NFT exists. Royalties go to the developer (Infinity) to keep enhancing design and applications... More Info
Infinity Turbine IT XR Project Redstone Design: NFT for sale... NFT for high tech turbine design with one part 3D printed counter-rotating energy turbine. Includes all rights to this turbine design, including license for Fluid Handling Block I and II for the turbine assembly and housing. The NFT includes the blueprints (cad/cam), revenue streams, and all future development of the IT XR Project Redstone... More Info
Infinity Turbine ROT Radial Outflow Turbine 24 Design and Worldwide Rights: NFT for sale... NFT for the ROT 24 energy turbine. Be part of the future with this NFT. This design can be bought and sold but only one design NFT exists. You may manufacture the unit, or get the revenues from its sale from Infinity Turbine. Royalties go to the developer (Infinity) to keep enhancing design and applications... More Info
Infinity Supercritical CO2 10 Liter Extractor Design and Worldwide Rights: The Infinity Supercritical 10L CO2 extractor is for botanical oil extraction, which is rich in terpenes and can produce shelf ready full spectrum oil. With over 5 years of development, this industry leader mature extractor machine has been sold since 2015 and is part of many profitable businesses. The process can also be used for electrowinning, e-waste recycling, and lithium battery recycling, gold mining electronic wastes, precious metals. CO2 can also be used in a reverse fuel cell with nafion to make a gas-to-liquids fuel, such as methanol, ethanol and butanol or ethylene. Supercritical CO2 has also been used for treating nafion to make it more effective catalyst. This NFT is for the purchase of worldwide rights which includes the design. More Info
NFT (Non Fungible Token): Buy our tech, design, development or system NFT and become part of our tech NFT network... More Info
Infinity Turbine Products: Special for this month, any plans are $10,000 for complete Cad/Cam blueprints. License is for one build. Try before you buy a production license. May pay by Bitcoin or other Crypto. Products Page... More Info
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)