Naphtha feed prices

Figure 7. Effect of aromatics by-product price structure and naphtha feed price on U.S. ethylene production costs (1000 MM Ibs/yr ethylene production from naphtha feed premium value by-products)...

Figure 3 presents the effect of feed price on ethylene production costs in a billion lb/yr European plant for naphtha, light gas oil, and heavy gas oil feedstocks based on premium by-product valuations. 

The breakeven price defines the unit price one could afford to pay for the gas oil to realize the same ethylene production cost as for a naphtha feed. If for a given naphtha price, the gas oil can be obtained at a price below the indicated gas oil breakeven price, gas oil would be the more attractive feed. If the gas oil can only be obtained at a price above the breakeven, naphtha would be the desired feed. Thus, with naphtha at, say, 1 /lb, the heavy gas oil would have to be priced below 0.7 /lb to be more profitable than naphtha as a cracking feed, assuming premium by-products prevail. Valuing the by-products as fuel has only a slight effect on the breakeven levels. The curves cross as nonaromatics in the pyrolysis gasoline have been valued the same as naphtha feed. 

Figure 4. Breakeven prices for heavy gas oil feed vs. naphtha feed in Europe (1000 MM lbs/yr ethylene production premium and fuel value by-products)...

Figure 8. Breakeven prices for ethane feed vs. naphtha feed in the United States. Parameter is aromatics by-product value. 1000 MM Ibs/yr ethylene production premium value byproducts.

Under the assumptions of naphtha price and aromatics value stated above, naphtha pyrolysis clearly would be superior to light hydrocarbon pyrolysis at their current feed prices. A similar analysis can probably be made also for gas oil. Thus, if the possible developments discussed above do materialize, the heavier feeds could probably dominate almost all new U.S. ethylene plant construction in the future. 

Fig. 3. Price ratio of various feeds to ethane, 1978—1991 (D) propane—ethane, (+) light naphtha—ethane, and (<)) fuU-range naphtha—ethane.

Naphtha at one time was a more popular feed, and alkah-promoted catalysts were developed specifically for use with it. As of 1994 the price of naphtha in most Western countries is too high for a reformer feed, and natural gas represents the best economical feedstock. However, where natural gas is not available, propane, butane, or naphtha is preferentially selected over fuel oil or coal. 

Cracking large hydrocarbons usually results in olefins, molecules with double bonds. Thats why the refinery cat crackers and thermal crackers are sources of ethylene and propylene. But the largest source is olefin plants where ethylene and propylene are the primary products of cracking one or more of the following ethane, propane, butane, naphtha, or gas oil. The choice of feedstock depends both on the olefins plant design and the market price of the feeds. 

At current price levels, heavier feeds in the United States are not competitive with light hydrocarbon feeds. With U.S. naphtha at 1.6 /lb (10 /gal), the ethylene production costs from this feed ranges about 40-70% higher than costs associated with lighter feeds, assuming premium by-product values. The differences are even greater with fuel byproduct values prevailing. 

In Europe. With either premium or fuel by-product prices prevailing, naphtha is very marginally the preferred feedstock. Heavy gas oil appears to be an interesting feed possibility at current price levels. Although the ethylene production cost with this feed is slightly higher than with naphtha, the difference is so small that it could be wiped out by a naphtha price increase of less than 0.1 /lb. 

Europe. The demand for naphtha for petrochemical feed purposes in Europe continues to rise strongly. As a result, the prices for this commodity have risen over the past several years. Increased use of light North African crudes, providing a higher proportion of gasoline and potential petrochemical naphtha, has retarded but not stopped the rise in naphtha prices. 

If widely predicted future price increases for the natural gas liquid feeds materialize, naphtha and gas on feedstocks will become more competitive in the United States even at current prices for the heavier feeds. 

Incorporating some or all of the above mentioned improvements will lead to a considerable reduction of energy consumption of an ammonia plant based on steam reforming of natural gas or naphtha. The actual plant design will depend on the project particulars and feed and utility price structure. 

Price of Naphtha and Other Liquid Feed Stocks... 

In this chapter we consider some commercial routes and emerging technology for the production of olefins Irom coal. For the most part olefins are made from natural gas and crude oil derivatives - LPG, naphtha, gas oil or residual fuel oil. The cost of these feed-stocks are tied one way or another to the prevailing price of crude oil and the petrochemical operations have to bid for feedstock against the oil-refiners demand for them to produce transport fuels. For example, a major feedstock is ethane. In developed economies the price of ethane is directly linked to the prevailing price of crude oil or indirectly via the natural gas price, which is linked one way or another to the price of crude oil. 

Lower olefins are today produced by steam cracking of naphtha, LSR or other paraffinic feeds. Hie actual methanol price does not allow the methanol to olefins process to compete economically. However, if methanol will become more available firom natural gas transforming routes, then there is a great chance for that process to become commercial. 

Ethylene. The largest potential chemical market for n-butanc is in steam cracking to ethylene and coproducts. n-Butane is a supplemental feedstock for olefin plants and has accounted for 1 to 4 percent of total ethylene production for most years since 1970. It can be used at up to 10 to 15 percent of the total feed in ethane/propane crackers with no major modifications. n-Butane also can be used as a supplemental feed at as high as 20 to 30 percent in hea y naphtha crackers. The consumption of C s has fluctuated considerably from year to year since 1970, depending on the relative price of butane and other feedstocks. The yield of ethylene is only 36 to 40 percent, with the other products including methane, propylene, ethane, butadiene, acetylene, and butylenes. About 1 to 2 billion lb of butane are consumed annually to produce ethylene. 

---