By-product value

Fluid bed boilers have also been applied as a cure to sulfur dioxide air pollution from power plants. Various schemes have been developed in which combustion of a sulfur containing fuel takes place in a fluidized bed of particles which absorb or react with sulfur dioxide. The particles are usually regenerated to recover sulfur, which often has enough by-product value to make a significant contribution to process economics. 

Net cost of the phenol (cumene + oxygen + plant operating cost less acetone less by-product values) ... 

This work also suggests other research and development directions needed to bring the price of ethanol down to an automotive fuel level. We need a lower capital cost hydrolysis process which can produce a concentrated sugar solution. We also need a fermentation process adaptable to concentrated sugar solutions to lower alcohol purification costs. Finally we need to recover and include by-product values - lignin, furfural, acids, methanol, etc. -in our income. 

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. 

Basis Naphtha Feedstock at European Location Premium By-Product Values... 

With fuel by-product values, the cost of producing ethylene increases as once-through severity decreases from 27 wt %. For example, at 27 wt % ethylene, the production cost is 4.0 /lb at 23 wt % the cost rises to over 4.2 /lb. This is primarily a result of more feed being downgraded to fuel at lower severity. 

More interesting, however, is the result when premium by-product values apply. Here we see that the production cost dips through a minimum at about 25% severity. This may be explained by noting that as severity drops, by-product credits increase owing to increased olefins production so that by-products credits minus feed costs increase, even while feed requirements go up. This tends to lower production costs. On the other hand, the investment and operating costs tend to increase as severity drops—this tends to raise production costs. The net effect is a minimum in production costs at about 2.45 /lb of ethylene. 

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.

Two possible future developments, should they become reality, could radically affect the U.S. ethylene industry. Lower cost imported heavier feedstocks and by-product value changes associated with lead free gasoline each would increase the attractiveness of using the heavy feeds. Acting together they would probably lead to future heavy feed domination of almost all new U.S. ethylene plant construction. 

This integrated plant will eost about 2,500 million eompared to the 1,708 million of the cracker only option. However, with the by-products valued with oil at 70/bbl or as those typical for 2007, the polymer production costs are about l,260/tonne. This is about the same product... 

Differential by-product value of crude case over naphtha case = l,347,000/yr.6... 

EP = Product value + (By-product value - (Raw material costs -... 

By-product value Moderate Moderate High Moderate... 

By-product value is a measure of the capability of producing a high-value tail gas. In many refinery hydrogen upgrading processes, the impurities to be rejected include hydrocarbons which have value significantly above fuel value. This is particularly true for olefin-containing streams. The relative amounts of high-value hydrocarbons and the incremental cost of further separation determine whether by-product recovery is an important parameter to be considered. 

By-product Value and Markets. Elemental sulfur is a valuable byproduct with existing markets (32). Liquid elemental sulfur is the most marketable form of sulfur, and the easiest to transport. Although most sulfur is used as sulfuric acid, it is significantly less expensive to transport liquid sulfur and convert it to sulfuric acid at the location of its use than to transport the acid. For comparison, 1 ton of sulfur could produce 2 tons SO2, 3.06 tons sulfuric acid, or 5.37 tons gypsum. 

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