Low sulfur

Fuel switch. Switching to a low-sulfur fuel is an obvious solution. 

The potential advantages of LPG concern essentially the environmental aspects. LPG s are simple mixtures of 3- and 4-carbon-atom hydrocarbons with few contaminants (very low sulfur content). LPG s contain no noxious additives such as lead and their exhaust emissions have little or no toxicity because aromatics are absent. This type of fuel also benefits often enough from a lower taxation. In spite of that, the use of LPG motor fuel remains static in France, if not on a slightly downward trend. There are several reasons for this situation little interest from automobile manufacturers, reluctance on the part of automobile customers, competition in the refining industry for other uses of and fractions, (alkylation, etherification, direct addition into the gasoline pool). However, in 1993 this subject seems to have received more interest (Hublin et al., 1993). 

In France there are four categories of heavy fuels whose specifications are given in Table 5.19 the different product qualities are distinguished essentially by the viscosity, equal to or less than 110 mm /s at SOT for No. 1 fuel oil, equal to or greater than 110 mm /s for No. 2 fuel oil, and by the sulfur content varying from 4 wt. % (No. 2 fuel oil) to 1 wt. % (No. 2 TBTS - very low sulfur content fuel oil). 

BTS Low sulfur content. TBTS Very low sulfur content. 

Characteristics Atmospheric residue (Arabian light) Vacuum residue (VR) Visbroken residue (on VR) LCO (low sulfur) HCO (low sulfur)... 

For the refiner, the main problem is to meet the specifications for kinematic viscosity and sulfur content. Dilution by light streams such as home-heating oil and LCO, and selection of feedstocks coming from low-sulfur crude oils give him a measure of flexibility that will nevertheless lead gradually to future restrictions, most notably the new more severe antipollution rules imposing lower limits on sulfur and nitrogen contents. 

In the past, reducing the sulfur content was mainly concerned with the heaviest products, most particularly the fuel oils. This development is explained by a legitimate concern to reduce SO2 emissions, notably in areas around large population centers. This is how low sulfur heavy fuels —having a maximum of 2% sulfur— and very low sulfur ( % sulfur) came into being. Currently the whole range of petroleum products, particularly motor fuels, should be strongly desulfurized for reasons we will explain hereafter. 

FOL No. 2 which can require supplementary specifications such as BTS (Low Sulfur content) and TBTS (Very Low Sulfur content). See AFNOR information documents M 15-010, M 15-011, M 15-012, M 15-013. 

These reactions can explain the absence of olefins in crude oil, their presence being detected only in the crudes of low sulfur content. The sulfur content in crude from Bradford which is the one of the rare crudes containing olefins is about 0.4%. 

Its purpose is to partially convert heavy fractions highly contaminated by natural compounds such as sulfur, nitrogen, metals Ni, V, and asphaltenes and to prepare feedstocks for deeper conversion or to produce low-sulfur fuel-oil. 

Heavy residues are not always converted. The use of low sulfur light crude and crudes having a reduced ultimate residue (higher ratio of gasoline + distillates/vacuum residue) as well as natural gas utilization has been intensified. 

Heavy residue conversion is linked to the demand for high quality diesel motor fuel (aromatics content 10%, cetane number 55) as well as to the demand for production of light fuel-oil having very low sulfur, nitrogen and metal contents. 

TBTS 1 very low sulfur content (/res basse teneur ... 

Steps such as the substitution of low sulfur fuels or nonvolatile solvents, change of taw materials, lowering of operation temperatures to reduce NO formation or vo1ati1i2ation of process material, and instaHion of weU-designed hoods (31—37) at emission points to effectively reduce the air quantity needed for pollutant capture are illustrations of the above principles. 

R. P. Janoso, "Baghouse Dust Collectors on a Low Sulfur Coal Eired Utihty Boiler," Preprint 74-101, 67th APCA Annual Meeting Denver, Col, June... 

Nonetheless, production and use of nitric phosphates ia Europe are continuing to grow. In general, nitric phosphate processes are somewhat more compHcated than sulfur-based processes and requite higher investment. In the past, several attempts have been made to estabHsh commercial acceptance of this type process ia the United States, but plant operations have been relatively short Hved because of low sulfur prices and resultant competition from sulfur-based processes. 

LPC Product Quality. Table 10 gives approximate analyses of several LPC products. Amino acid analyses of LPC products have been pubhshed including those from alfalfa, wheat leaf, barley, and lupin (101) soybean, sugar beet, and tobacco (102) Pro-Xan LPC products (100,103) and for a variety of other crop plants (104,105). The composition of LPCs varies widely depending on the raw materials and processes used. Amino acid profiles are generally satisfactory except for low sulfur amino acid contents, ie, cystine and methionine. 

A significant issue in combustors in the mid-1990s is the performance of the process in an environmentally acceptable manner through the use of either low sulfur coal or post-combustion clean-up of the flue gases. Thus there is a marked trend to more efficient methods of coal combustion and, in fact, a combustion system that is able to accept coal without the necessity of a post-combustion treatment or without emitting objectionable amounts of sulfur oxides, nitrogen oxides, and particulates is very desirable (51,52). 

Properties. The properties of char products from two possible coal feeds, a low sulfur Western coal, and a high sulfur Midwestern coal, are shown in Table 11. The char derived from the low sulfur Western coal may be direcdy suitable as plant fuel, with only minor addition of clean process gas to stabilize its combustion. Elue gas desulfurization may not be required. Elue gas from the combustion of the char derived from the high sulfur Illinois coal, however, requires desulfurization before it may be discharged into the atmosphere. 

Furthermore, 60—100 L (14—24 gal) oil, having sulfur content below 0.4 wt %, could be recovered per metric ton coal from pyrolysis at 427—517°C. The recovered oil was suitable as low sulfur fuel. Figure 15 is a flow sheet of the Rocky Flats pilot plant. Coal is fed from hoppers to a dilute-phase, fluid-bed preheater and transported to a pyrolysis dmm, where it is contacted by hot ceramic balls. Pyrolysis dmm effluent is passed over a trommel screen that permits char product to fall through. Product char is thereafter cooled and sent to storage. The ceramic balls are recycled and pyrolysis vapors are condensed and fractionated. 

The volatiles contents of product chars decreased from ca 25—16% with temperature. Char (lower) heating values, on the other hand, increased from ca 26.75 MJ /kg (11,500 Btu/lb) to 29.5 MJ /kg (12,700 Btu/lb) with temperature. Chars in this range of heating values are suitable for boiler fuel apphcation and the low sulfur content (about equal to that of the starting coal) permits direct combustion. These char products, however, are pyrophoric and require special handling in storage and transportation systems. 

In the United States and increasingly in other parts of the world, environmental regulations prohibit the combustion of all but very low sulfur-content coals without sulfur oxide emission controls. The cost of installing sulfur oxide control equipment together with concern about equipment rehabihty have led to the shipment of the lower rank low sulfur coals from up to 1600 km away from the mining site. 

North America.. In the United States, lignite deposits are located in the northern Great Plains and in the Gulf states. Subbituminous coal is found along the Rocky Mountains. The western half of North Dakota has about 74% of the nation s resources, Montana 23%, Texas 2%, and Alabama and South Dakota about 0.5% each. The lignite resources to 914 m represent 28% of the total toimage of all coal deposits in the United States. The lower cost and low sulfur content have contributed to rapid growth in production. 

The lignitic coals of the northern United States tend to have low sulfur contents, making them attractive for boilet fuels to meet sulfur-emission standards. However, low sulfur content coals have impaired the performance of electrostatic precipitators. The ash of these coals tends to be high in alkaline earths (Ca, Mg) and alkaUes (Na, K). As a result, the ash can trap sulfur as sulfites and sulfates (see Airpollution control methods). 

Because of its low sulfur content, lignite is becoming mote important. The U.S. Clean Air Act Amendments of 1990 have resulted in economic premiums fotlow sulfur coal corresponding to 10/t for emission allowances at 500/t of SO2 (32). 

Fig. 9. Measured coal-fired flow faciUty (CFFF) NO emissions where ( ) represents high sulfur coal, (e) low sulfur coal, (A) low sulfur coal having K2/S = 1.15, and ( ) LMF5-G. A, Illinois No. 6 coal (3% S) B, Montana Rosebud coal (1% S), and the NSPS range is between the dotted lines. To...

Tetrahydronaphthalene is produced by the catalytic treatment of naphthalene with hydrogen. Various processes have been used, eg, vapor-phase reactions at 101.3 kPa (1 atm) as well as higher pressure Hquid-phase hydrogenation where the conditions are dependent upon the particular catalyst used. Nickel or modified nickel catalysts generally are used commercially however, they are sensitive to sulfur, and only naphthalene that has very low sulfur levels can be used. Thus many naphthalene producers purify their product to remove the thionaphthene, which is the principal sulfur compound present. Sodium treatment and catalytic hydrodesulfuri2ation processes have been used for the removal of sulfur from naphthalene the latter treatment is preferred because of the ha2ardous nature of sodium treatment. 

Heavy fuel oil usually contains residuum that is mixed (cut back) to a specified viscosity with gas oils and fractionator bottoms. For some industrial purposes in which flames or flue gases contact the product (eg, ceramics, glass, heat treating, and open hearth furnaces), fuel oils must be blended to low sulfur specifications low sulfur residues are preferable for these fuels. 

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