Shot coke

Coke produced from delayed coking is described as delayed sponge, shot, or needle coke depending on its physical structure. Shot coke is the most common when running the unit under severe conditions with sour crude residues. Needle coke is produced from selected aromatic feedstocks. Sponge coke is more porous and has a high surface area. The properties and markets for petroleum cokes have been reviewed by Dymond. Table 3-4 shows the types of petroleum cokes and their uses. ... 

Some forms of petroleum coke (such as shot coke) can have additional handling costs. 

The three main types of coke that are produced in a delayed coker are typically categorized as needle coke, sponge coke and shot coke. Needle coke is a premium grade coke, which is considered a specialty coke and is produced from specific aromatic feedstocks. 

The regular grades of coke are sponge coke and shot coke. A short description of each type of coke follows. 

Shot Coke. Another form, generally undesirable, of regular coke is formed as small spheres often held together in a matrix of sponge coke or in large spheres of shot coke alone. The formation is highly dependent upon feedstocks such as Maya, West Texas Sour and... 

There are basic differences in coke sizing and structure for delayed and fluid cokes because of differences in the two coking operations. Sometimes, fluidization occurs in delayed coke drums when the feed has a high asphaltene content and the recycle ratio is low. Such conditions tend to produce millimeter-size "shot" coke, which is very isotropic, and yields a calcined coke which is very hard with low porosity and high density. Such coke is hard to... 

It is free from troublesome material like shot coke in Delayed Coker. 

In an attempt to explain the activity of Nafion it was hypothesized that the SO3H groups were not in the inverted micelle, but rather were exposed at the surface of the micelle. This observation suggested selecting a different hydrophobic material. The next approach was to utilize a liquid composition of Nafion and coat a hydrophobic support such as carbon. The carbon selected was calcined shot coke, a material with very large pores. The mean pore diameter was about lOOOA. 

The liquid composition of Nafion , approximately 5 wt% solution, was used to coat the calcined shot coke (10-20 mesh, 0.42m /gram). Loadings were varied up to 3 wt%. The oligomerization of isobutylene in toluene at 110°C was used to measure the activity of the sulfonic acid catalysts. Table 4 compares the activity of several supported and non-supported sulfonic acid polymers. The... 

CSC is calcined shot coke DOW fluorocarbon sulfonic acid polymer on a-alumina. 

Shot coke Bottom nozzle plugging, uneven cooling... 

Shot coke is composed of precipitated asphaltenes. Asphaltenes are large hydrocarbon molecules that are dispersed in the lighter aromatic and paraffinic oils in vacuum residuum. 

When these lighter molecules thermally crack and vaporize in the coke drum, the asphaltenes agglomerate and precipitate out of solution. The coke is called shot coke because the precipitated asphaltenes take the form of hard, spherical particles. 

Sponge coke is a mixture of needle and shot coke. The coke formed is spongelike in appearance, and has a dull, black cast. 

It is porous, with no structure. When the ratio of needle coke to shot coke falls below a certain point, the s()onge coke will become less porous. 

The outside surface of shot coke spheres is coated with a layer of needle coke. The coating gives shot coke its polished-surface appearance. 

When coke is cut from a drum, sponge coke is found along the walls, and shot coke is found in the middle. What causes this segregation ... 

The coefficient of thermal expansion of calcined shot coke is too high, making it unsuitable for high-quality anode production. 

The VCM content of shot coke is similar to that of sponge coke, in the range of 9%-12%. 

The reason for the less porous apiaearance is that shot coke, in this case, is just beginning to form. This is sometimes called incipient... 

Whenever it is desired to reduce the production of low-value coke to make more gas oil, the coke drum generates almost all shot coke. How can coke production be reduced without causing shot coke ... 

A reduction in coke production cannot be made without producing more shot coke. A certain amount of cross-linked aromatic coke, mixed with the asphaltic coke, is necessary to turn shot coke into sponge coke. This increases total coke production. 

Why does the amount of shot coke in the drum vary, even though the drum temperature and pressure, and the recycle ratio and refinery crude composition are kept constant ... 

The formation of free radicals in the coker feed is favored by exposure of the crude or resid to oxygen. Particulate matter in the resid also accelerates shot coke formation. The particulates can be controlled by improving the operation of the crude unit desalter. 

Does increasing the recycle of light coker gas oil promote shot coke formation ... 

I witnessed a drum full of shot coke unheaded with this device. The coke started to roll out in a most alarming fashion. However, the operator controlling the piston from a remote location simply closed the head partially until the shot coke stopped rolling out. Champlin has applied for a patent on this device (not granted as of January 1990). 

Coke drum readiness, 42-43 pres-sure/back-pressure, 46,80,82 vapor outlet, 47 warm-up, 86, 88 Coke quality, 43-49 coke VCM, 43-44 time/pressure/steam, 44 physical structure, 44 shot coke, 45... 

Shot coke. Coke Is made in small balls instead of the usual sponge structure. 

Why is the coke in the top of a coke drum mostly sponge coke, and the coke in the middle and bottom of the drum mostly shot coke ... 

During coking, the top of the drum runs cooler than the middle or bottom of the drum. Therefore, the coke formed in the top of the drum contains a higher percentage of needle coke mixed with shot coke. 

Why, at constant heater outlet temperature, does the coke drum vapor outlet run hotter when shot coke is produced compared to when needle coke is produced ... 

The precipitation of asphaltenes to form shot coke is a physical change involving no heat of reaction. Therefore, there is no temperature drop across the coke drum. 

Needle-grade coke contains no shot coke. Commercial needle coke is typically produced by charging FCCU slurry oil to the delayed coker. 

The coker feed nozzle at the bottom of the coke drum can plug with shot coke. How can this be prevented ... 

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