Delayed cokers

Thermal Cracking. Heavy petroleum fractions such as resid are thermally cracked in delayed cokers or flexicokers (44,56,57). The main products from the process are petroleum coke and off-gas which contain light olefins and butylenes. This stream also contains a considerable amount of butane. Process conditions for the flexicoker are more severe than for the delayed coker, about 550°C versus 450°C. Both are operated at low pressures, around 300—600 kPa (43—87 psi). Flexicokers produce much more linear butenes, particularly 2-butene, than delayed cokers and about half the amount of isobutylene (Table 7). This is attributed to high severity of operation for the flexicoker (43). 

Vapors from the top of the drum are directed to the fractionator where they are separated into gases, naphtha, kerosine, and gas oil. Table 3-3 shows products from a delayed coker using different feeds. ... 

Feeds and products from a delayed coker unit (using different feeds) ... 

The gas oil feed for the conventional cat cracker comes primarily from the atmospheric column, the vacuum tower, and the delayed coker. In addition, a number of refiners blend some atmospheric or vacuum resid into the feedstocks to be processed in the FCC unit. 

A test run is conducted to evaluate the performance of a 50,000 bpd (331 m /hr) FCC unit. The feed to the unit is gas oil from the vacuum unit. No recycle stream is processed however, the off-gas from the delayed coker is sent to the gas recovery section. Products from the unit are fuel gas, LPG, gasoline, LCO, and decanted oil (DO). Tables 5-2 and 5-3 contain stream flow rates, operating data, and laboratory analyses. The meter factors have been adjusted for actual operating conditions. 

Particulate emissions from decoking can also be considerable. Coke-laden water from decoking operations in delayed cokers (hydrogen sulfide, ammonia, suspended solids) and coke dust (carbon particles and hydrocarbons) occur. 

Butylenes (FCC and delayed coker) Isopropanol, Oligomers MEK (methyl ethyl ketone) Alkylation, MTBE... 

An LP model for a petroleum refinery would consist of a number of modules for the different units (e.g., FCC, hydrocracker, fluid delayed coker, etc.). Each of these... 

This is an area of associated technology that has also been developed and demonstrated in several recent units. We have installed a number of refinery off gas (ROG) units, the purpose of which is to treat and concentrate the combined C2 and lighter fractions from refinery unsaturated off gas (FCC and delayed cokers). 

During the past 25 years United States petroleum coke production has increased from less than 1,000,-000 tons per year to 3,400,000. Most of the 1,000,-000 tons were produced in externally fired shell stills and manually removed from the stills. Almost all of the 3,400,000 tons were produced in large "delayed coker" type coke drums and removed mechanically. As was true 25 years ago, the major use for petroleum coke is as a fuel, although the proportion so used is declining. Its use in aluminum production is growing rapidly and currently takes about 18% of the production. 

There is little danger, in injecting a controlled amount of water into a furnace inlet, when using a properly designed metering pump. Such pumps typically have a capacity of 1 to 10 GPM and provide a set flow, regardless of the discharge pressure. The injected water flashes immediately to steam inside the furnace tubes. Vfe have retrofitted several vacuum and delayed coker heaters with condensate injection systems, with no adverse downstream effects. Water from the hot well of a vacuum ejector system is our normal source of condensate for this environmentally friendly modification. 

The deasphalted oil is sent to the delayed coker where it is combined with the heavy coker gas oil from the coker fractionator and sent to the heavy coker gas oil stripper where low-boiling hydrocarbons, are stripped off and returned to the fractionator. The stripped deasphalted oil/heavy coker gas oil mixture is re-... 

The process was first demonstrated at Cities Service s Lake Charles refinery with the construction of a 2500 BPD unit. The unit was later expanded to 6000 BPD with no increase in the size of the catalytic reactors. Maximum sulfur removal from delayed coker feedstock was achieved by this expansion. 

A major fire that resulted in 65 million in property damages occurred early in the morning (4 21 A.M.) on August 2, 1993. The central unit of three delayed coker units was the origin of the fire. Each of the three units consisted of four 100-ft. metal coke drums mounted about 40 ft. above grade. The sustained, intense fire caused other pipes in the area to rupture, releasing more hydrocarbons. Over 95 fire brigade members battled the fierce fire for nearly three hours. [21] The fire killed three people. 

The complexity of formation of mesophase must not be underestimated. With the exception of a few model compounds, it is the industrial pitch which is the source of mesophase. Such materials contain thousands of reactive molecules and there is an interdependence in the carbonization system which currently is known to us but not analyzed in depth. This is an area for further research. Formation of mesophase is further complicated because it involves chemistry within a fluid/plastic system of increasing viscosity. And in the delayed coker, volatile release and liquid turbulence are yet additional factors in influencing final structure in mesophase. 

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