Economics of Naphtha Cracking

Unlike gas feedstock cracking the economics cracking of liquid feedstock such as naphtha is complicated by the ability to change the product slate by changing the cracking conditions (severity) and to select 

The base case is developed for the production of 1 million toimes of ethylene per year, which is typical of the scale for naphtha-crackers being established in 2008. The base case statistics (oil at 70/bbl) for the OPEN system (all products sold) are given in Table 9.1. 

The capital for the basic operation producing lOOOkt/y ethylene is about 1,700 million. This is for a stand-alone plant producing the products as detailed and does not, for instance, include downstream plant for separating the C4 olefin stream. 

With oil at the 70/bbl mark, the estimated production cost is l,209/tonne with an operating margin of about 229/tonne. 

A CLOSED operation can be modelled in which all products other than ethylene, propylene and pyrolysis gasoline are recycled. The propane and C4 streams are recycled to the feed side of the pyrolysis furnace and the hydrogen, methane and fuel oil to the fuel side of the furnace. This offsets some of the need for fuel but reduces the by-product credits to 482 million/year and this raises the production cost to 1227/toime and reduces the operating margin to 211/tonne as valuable by-products are reduced to fuel value. The comparative cost breakdown is illustrated in Eigure 9.4. 

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