Clean fuels

As mentioned in Chapter 1 (Section 8.2.4), on-road diesel in the United States must contain 15 wppm sulfur by 2006. The sulfur limit for non-road diesel will be 500 wppm in 2007. The present U.S. specification for gasoline is 30 wppm sulfur. In the European Union, the sulfur content of both gasoline and diesel must be 50 wppm by 2005 and 10 wppm by 2008. 

To meet clean fuel specifications, refiners in North America and Europe are increasing their hydroprocessing capabilities and adjusting operations. Two real-world examples are described below. 

Example 2. A European refiner now runs a mild hydrocracker (MHC) to maximize conversion of VGO and to pretreat the feed to its FCC unit. The plant cannot post-treat its FCC gasoline, so the sulfur content of the MHC bottoms must be less than 500 wppm to guarantee that the sulfur content of the FCC gasoline is less than 150 wppm. Other low-sulfur streams (reformate, alkylate and hydrotreated gas oil) go into the final gasoline blend, so sulfur in the FCC gasoline can exceed the final-product limit of 50 wppm. 

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Proposed Regulationsfor Eow Emission Uehicles and Clean Fuels, Staff Report, California Air Resources Board, Sacramento, Calif., Aug. 13, 1990. 

J. A. Alich, Jr., and R. E. Inman, Effective Etilicyation of Solar Energy to Produce Clean Fuel, Grant No. GI38723, Fiaal Report for National Science Foundation, Stanford Research Institute, Palo Alto, Calif., June 1974. 

A. Kasem, Three Clean Fuels from Coal Technology and Economics, Marcel Dekker, Inc., New York, 1979. 

Od condensed from the released volatdes from the second stage is filtered and catalyticady hydrotreated at high pressure to produce a synthetic cmde od. Medium heat-content gas produced after the removal of H2S and CO2 is suitable as clean fuel. The pyrolysis gas produced, however, is insufficient to provide the fuel requirement for the total plant. Residual char, 50—60% of the feed coal, has a heating value and sulfur content about the same as feed coal, and its utilisation may thus largely dictate process utdity. 

J. A. Hamshar, H. D. Terzian, and L. J. Scotti, "Clean Fuels From Coal by the COED Process," paper presented at EPA Symposium on Environmental Aspects of Fuel Conversion Technology, St. Louis, Mo., May 1974. 

Electrode Walls. Development of durable electrode wads, one of the most critical issues for MHD generators, has proceeded in two basic directions ceramic electrodes operating at very high surface temperatures (>2000 K) for use in channels operating with clean fuels such as natural gas, and cooled metal electrodes with surface temperatures in the range 500—800 K for channels operating with slag or ash-laden flows. 

Clean fuel was used. Continuous generation. LPG was used as fuel. 

The UPI and MI retorts are processing 7000 t/d (7700 short tons/d) of Irati shale to produce 24,381 m /d (3870 bbl) of shale as well as 80 t (55 short tons) of LPG, 132 t (145 short tons) of clean fuel gas, and 98 t (108 short tons) of sulfur. The SIX plant has reached its design rate (Table 16) in an energy efficient manner with a high on-stream (operating) factor. 

Checking Against Optimum Design. This attempts to answer the question whether a balance needs to be as it is. The first thing to compare against is the best current practice. Information is available ia the Hterature (13) for large-volume chemicals such as NH, CH OH, urea, and ethylene. The second step is to look for obvious violations of good practice on iadividual pieces of equipment. Examples of violations are stack temperatures > 150° C process streams > 120° C, cooled by air or water process streams > 65° C, heated by steam t/ urbine 65% reflux ratio > 1.15 times minimum and excess air > 10% on clean fuels. 

The exacting Hst of specification requirements for aviation gas turbine fuels and the constraints imposed by deUvering clean fuel safely from refinery to aircraft are the factors that affect the economics. Compared with other distillates such as diesel and burner fuels, kerosene jet fuels are narrow-cut specialized products, and usually command a premium price over other distillates. The prices charged for jet fuels tend to escalate with the basic price of cmde, a factor which seriously underrnined airline profits during the Persian Gulf war as cmde prices increased sharply. 

Bodle, Vyas, and Talwalker Clean Fuels from Coal Symposium IT, Institute of Gas Technology, Chicago, 1975) presented the chart in Fig. 27-5, which shows very simply the different routes from coal to clean gases and liquids. 

The new law also establishes a clean fuel car pilot program in California, requiring the phase-in of tighter emission limits for 150,000 vehicles in model year 1996 and 300,000 by the model year 1999. These standards can be met with any combination of vehicle technology and cleaner fuels. The standards become even stricter in 2001. Other states can opt in to this program, though only through incentives, not sales or production mandates. 

Clean Fuels low-pollution fuels that can replace ordinary gasoline, including gasohol and natural and LP gas. 

Public concerns about air quality led to the passage of the Clean Air Act in 1970 to amendments to that act in 1977 and 1990. The 1990 amendments contained seven separate titles covering different regula-toiy programs and include requirements to install more advanced pollution control equipment and make other changes in industrial operations to reduce emissions of air pollutants. The 1990 amendments address sulfur dioxide emissions and acid rain deposition, nitrous oxide emissions, ground-level ozone, carbon monoxide emissions, particulate emissions, tail pipe emissions, evaporative emissions, reformulated gasoline, clean-fueled vehicles and fleets, hazardous air pollutants, solid waste incineration, and accidental chemical releases. 

Methane is mainly used as a clean fuel gas. Approximately one million BTU are obtained by burning 1,000 ft of dry natural gas (methane). It is also an important source for carbon black. 

As a constituent of synthesis gas, hydrogen is a precursor for ammonia, methanol, Oxo alcohols, and hydrocarbons from Fischer Tropsch processes. The direct use of hydrogen as a clean fuel for automobiles and buses is currently being evaluated compared to fuel cell vehicles that use hydrocarbon fuels which are converted through on-board reformers to a hydrogen-rich gas. Direct use of H2 provides greater efficiency and environmental benefits. ... 

Ammonia is the precursor for many other chemicals such as nitric acid, hydrazine, acrylonitrile, and hexamethylenediamine. Ammonia, having three hydrogen atoms per molecule, may be viewed as an energy source. It has been proposed that anhydrous liquid ammonia may be used as a clean fuel for the automotive industry. Compared with hydrogen, anhydrous ammonia is more manageable. It is stored in iron or steel containers and could be transported commercially via pipeline, railroad tanker cars, and highway tanker trucks. The oxidation reaction could be represented as ... 

Clean fuel-emissions are low compared with combustion of most other fossil fuels. 

Although the demand for transportation motor fuels in North America is projected to be limited, economic growth in other parts of the world will require crude oil-based fuels. The Far East, Latin America, and the former Soviet Union are areas where there will be substantial demand for transportation fuels. The collapse of communism, the privatization of state-owned oil companies, and the global awareness of environmentally clean fuels will cause this growth. 

Lee, A. L., Methanation for Coal Gasification, Clean Fuel for Coal Symp. 

Desulfurization processes are absolutely necessary for producing clean fuels. Possible strategies to realize ultradeep suffiirization currently include adsorption, extraction, oxidation, and bioprocesses. Oxidative desulfurization (ODS) combined with extraction is considered one of the most promising of these processes [13]. Ultradeep desulfurization of diesel by selective oxidation with amphiphilic catalyst assembled in emulsion droplets has given results where the sulfur level of desulfurized diesel can be lowered from 500 ppm to about 0.1 ppm without changing the properties of the diesel [12]. 

Ultradeep desulfurization of fuel oils is used for producing not only clean fuels but also sulfur-free hydrogen used in fuel-cell systems, in which the hydrogen can be produced potentially through the reforming of fuel oils. Fuel-cell systems must be run with little-to-no sulfur content, because sulfur can irreversibly poison the precious metal catalysts and electrodes used [12]. 

There is a need to seek an environmentally benign, technically feasible and economical alternative fuel because of the limited crude oil reserves and serious pollution all over the world. Recently, dimethyl ether (DME) is proved to be used as an alternative clean fuel in transportation, power generation and household use for its excellent behavior in compression ignition for combustion, cetane number of over 55 and zero sulfur content, and is praised as a super-clean fuel in the 21 century. It has a promising foreground of application. Therefore, the efficient synthesis of DME from syngas derived from natural gas, coal or biomass has drawn much attention. 

To date, electrochemical C02 transport has not been applied to situations other than manned spacecraft life support. It appears possible that commercial MCFC s can provide an economical means for providing food-grade C02 [34]. In this scheme (Fig. 23b) the MCFC acts as a concentrator for C02 (and some 02) from the flue gas emitted from a power plant burning relatively clean fuel (e.g. natural gas). Electric power input is required, as is considerable regenerative heat exchange. Despite these charges, the process would be economical if the MCFC stacks become commercially available at projected prices [34]. 

J. "The Nature and Origins of Asphaltenes in Processed Coals Chemistry and Mechanisms of Coal Conversion to Clean Fuel", Annual Rept. for 1978 from Mobil Res. Dev. Corpn. to Electric Power Research Institute, AF-1298, Vol. 2. 

Dixson, S., Quality products, in The Importance of Conversion Processes in Oil Refining and their Role in the Production of Clean Fuels. 2006. IFP - Rueil-Malmaison, 20-22 June OAPEC-IFP JOINT SEMINAR. 

Marion, P., Axens Clean Fuels Technologies, in 4th International Conference on Petroleum Refining Technology Economics in Russia, the CIS and Baltics. 2002, 21-23 October. Axens-IFP. 

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