Fluid catalytic cracking - Wikipedia. A typical fluid catalytic cracking unit in a petroleum refinery. Fluid catalytic cracking (FCC) is one of the most important conversion processes used in petroleum refineries. It is widely used to convert the high- boiling, high- molecular weight hydrocarbon fractions of petroleumcrude oils into more valuable gasoline, olefinic gases, and other products.[1][2][3] Cracking of petroleum hydrocarbons was originally done by thermal cracking, which has been almost completely replaced by catalytic cracking because it produces more gasoline with a higher octane rating.
Naphtha Catalytic Cracking For Propylene Production Process
It also produces byproduct gases that have more carbon- carbon double bonds (i. The feedstock to FCC is usually that portion of the crude oil that has an initial boiling point of 3. C or higher at atmospheric pressure and an average molecular weight ranging from about 2.
This portion of crude oil is often referred to as heavy gas oil or vacuum gas oil (HVGO). In the FCC process, the feedstock is heated to a high temperature and moderate pressure, and brought into contact with a hot, powdered catalyst. The catalyst breaks the long- chain molecules of the high- boiling hydrocarbon liquids into much shorter molecules, which are collected as a vapor. Economics[edit]Oil refineries use fluid catalytic cracking to correct the imbalance between the market demand for gasoline and the excess of heavy, high boiling range products resulting from the distillation of crude oil.
As of 2. 00. 6, FCC units were in operation at 4. FCC to produce high- octane gasoline and fuel oils.[2][4] During 2. FCC units in the United States processed a total of 5,3. FCC units worldwide processed about twice that amount. FCC units are less common in Europe and Asia because those regions have high demand for diesel and kerosene, which can be satisfied with hydrocracking. In the US, fluid catalytic cracking is more common because the demand for gasoline is higher. Flow diagram and process description[edit]The modern FCC units are all continuous processes which operate 2.
HISTORY of THE TEXAS COMPANY. And PORT ARTHUR WORKS Refinery. by Elton N. Gish. The Port Arthur Works was a direct by-product of the January 10, 1901, Lucas gusher.
There are several different proprietary designs that have been developed for modern FCC units. Each design is available under a license that must be purchased from the design developer by any petroleum refining company desiring to construct and operate an FCC of a given design. There are two different configurations for an FCC unit: the "stacked" type where the reactor and the catalyst regenerator are contained in a single vessel with the reactor above the catalyst regenerator and the "side- by- side" type where the reactor and catalyst regenerator are in two separate vessels. These are the major FCC designers and licensors: [1][3][4][6]Side- by- side configuration: Stacked configuration: Each of the proprietary design licensors claims to have unique features and advantages. A complete discussion of the relative advantages of each of the processes is beyond the scope of this article.
Reactor and Regenerator[edit]The reactor and regenerator are considered to be the heart of the fluid catalytic cracking unit. The schematic flow diagram of a typical modern FCC unit in Figure 1 below is based upon the "side- by- side" configuration. The preheated high- boiling petroleum feedstock (at about 3. C) consisting of long- chain hydrocarbon molecules is combined with recycle slurry oil from the bottom of the distillation column and injected into the catalyst riser where it is vaporized and cracked into smaller molecules of vapor by contact and mixing with the very hot powdered catalyst from the regenerator. All of the cracking reactions take place in the catalyst riser within a period of 2–4 seconds. The hydrocarbon vapors "fluidize" the powdered catalyst and the mixture of hydrocarbon vapors and catalyst flows upward to enter the reactor at a temperature of about 5. C and a pressure of about 1.
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- Investment in on-purpose propylene production technology based on naphtha-based feedstock is taking on various process configurations.
- Petroleum Refining Corrosion (reproduced courtesy of the Occupational Safety and Health Administration) OSHA. Contents. Introduction; Overview of the Petroleum Industry.
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The reactor is a vessel in which the cracked product vapors are: (a) separated from the spent catalyst by flowing through a set of two- stage cyclones within the reactor and (b) the spent catalyst flows downward through a steam stripping section to remove any hydrocarbon vapors before the spent catalyst returns to the catalyst regenerator. The flow of spent catalyst to the regenerator is regulated by a slide valve in the spent catalyst line. Since the cracking reactions produce some carbonaceous material (referred to as catalyst coke) that deposits on the catalyst and very quickly reduces the catalyst reactivity, the catalyst is regenerated by burning off the deposited coke with air blown into the regenerator. The regenerator operates at a temperature of about 7.
In petrochemistry, petroleum geology and organic chemistry, cracking is the process whereby complex organic molecules such as kerogens or long-chain hydrocarbons are. Mixed Naphtha/Methanol Feed Used in the Thermal Catalytic/Steam Cracking (TCSC) Process for the Production of Propylene and Ethylene. Table 1 Typical product yields (%) by mass from steam cracking various hydrocarbon feedstocks. Data from: Petroleum processes Volume 1, A Chauvel and G Lefebrve.
C and a pressure of about 2. The combustion of the coke is exothermic and it produces a large amount of heat that is partially absorbed by the regenerated catalyst and provides the heat required for the vaporization of the feedstock and the endothermic cracking reactions that take place in the catalyst riser. For that reason, FCC units are often referred to as being 'heat balanced'. The hot catalyst (at about 7.
C) leaving the regenerator flows into a catalyst withdrawal well where any entrained combustion flue gases are allowed to escape and flow back into the upper part to the regenerator. The flow of regenerated catalyst to the feedstock injection point below the catalyst riser is regulated by a slide valve in the regenerated catalyst line. The hot flue gas exits the regenerator after passing through multiple sets of two- stage cyclones that remove entrained catalyst from the flue gas. The amount of catalyst circulating between the regenerator and the reactor amounts to about 5 kg per kg of feedstock, which is equivalent to about 4. Thus, an FCC unit processing 7. Figure 1: A schematic flow diagram of a Fluid Catalytic Cracking unit as used in petroleum refineries.
Distillation column[edit]The reaction product vapors (at 5.C and a pressure of 1.
FCC end products of cracked petroleum naphtha, fuel oil, and offgas. After further processing for removal of sulfur compounds, the cracked naphtha becomes a high- octane component of the refinery's blended gasolines. The main fractionator offgas is sent to what is called a gas recovery unit where it is separated into butanes and butylenes, propane and propylene, and lower molecular weight gases (hydrogen, methane, ethylene and ethane). Some FCC gas recovery units may also separate out some of the ethane and ethylene. Although the schematic flow diagram above depicts the main fractionator as having only one sidecut stripper and one fuel oil product, many FCC main fractionators have two sidecut strippers and produce a light fuel oil and a heavy fuel oil. Likewise, many FCC main fractionators produce a light cracked naphtha and a heavy cracked naphtha. The terminology light and heavy in this context refers to the product boiling ranges, with light products having a lower boiling range than heavy products.
The bottom product oil from the main fractionator contains residual catalyst particles which were not completely removed by the cyclones in the top of the reactor. For that reason, the bottom product oil is referred to as a slurry oil. Part of that slurry oil is recycled back into the main fractionator above the entry point of the hot reaction product vapors so as to cool and partially condense the reaction product vapors as they enter the main fractionator. The remainder of the slurry oil is pumped through a slurry settler.
The bottom oil from the slurry settler contains most of the slurry oil catalyst particles and is recycled back into the catalyst riser by combining it with the FCC feedstock oil. The clarified slurry oil or decant oil is withdrawn from the top of slurry settler for use elsewhere in the refinery, as a heavy fuel oil blending component, or as carbon black feedstock.
Regenerator flue gas[edit]Depending on the choice of FCC design, the combustion in the regenerator of the coke on the spent catalyst may or may not be complete combustion to carbon dioxide CO2. The combustion air flow is controlled so as to provide the desired ratio of carbon monoxide (CO) to carbon dioxide for each specific FCC design.[1][4]In the design shown in Figure 1, the coke has only been partially combusted to CO2. The combustion flue gas (containing CO and CO2) at 7.
C and at a pressure of 2. This is required to prevent erosion damage to the blades in the turbo- expander that the flue gas is next routed through.