The Oil Drum

A review of what petroleum coke is  (the carbon residue when you have driven off the hydrogen molecules) also describes how it is produced

Petroleum coke is a by-product of the oil refining process. Delayed coking, the most widely used process, uses heavy residual oil as a feedstock. During delayed coking, heavy residual oil is introduced into a furnace, heated to about 480 °C, and pumped into coking drums. The coking process initiates the formation of coke and causes it to solidify on the drum wall. Thermal decomposition drives off gases, which are removed continuously. When this reaction is complete, the drum is opened, and coke removal begins. Water spraying thermally shocks the coke and allows it to break off. Coke that remains on the drum walls is subsequently cut from the drum with a high pressure water jet. After the water drains, coke is transported for use or storage.

. The volume of coke generated is also given

As of January 1, 1998, total worldwide production of coke was reported to be approximately 46 x 106 tonnes per annum [6]. Of this, North America (predominantly the U.S.) accounted for approximately 66.5 percent; Europe, about 17 percent; the Asia-Pacific region, about 9.5 percent; South America/Caribbean, about 4.5 percent; and the Middle East/Africa, about 2.5 percent [6]. Nearly 90 percent of the total coke produced is delayed petroleum coke. Of the petroleum coke produced in the U.S., about 66 percent is exported. Japan, Turkey, Italy, Spain, Belgium, The Netherlands, and Canada consume 75 percent of U.S. exported coke [4]. Of the approximately 10 x 106 tonnes of petroleum coke consumed domestically, approximately 2.5 x 106 tonnes (which is equivalent to about 1,000 MW of electric power) are used for power generation. No hard statistics are available as to how much of the world's annual petroleum coke production is currently used for power generation. However, projections of major boiler suppliers indicate that between 1,500 and 2,000 MW of additional petroleum coke-based power is expected to come on line within the next 5 years. With the maturation of petroleum coke-based power generation technologies and increased production of petroleum coke, it is expected that these numbers will grow.

The paper also explains how to get the pollutants out of the flue gases, and ends

A deterioration in the quality of crude oil and improvements in oil refining technology have led to increased production of petroleum coke. The mismatched supply and demand situation has caused the price of petroleum coke to drop, and experts predict that this situation will continue for the near-term. This has created an opportunity for increased use of petroleum coke as both a primary and a co-firing fuel for power generation. Today four technologies are available to successfully use petroleum coke.

 I suspect that the US may now have as many boilers in operation as can use the product, and the Chinese may be building them, and looking for additional material.

(I have only ever worked with it once, and found it very difficult to ignite).