Refinery hydrocarbon streams

The outcome of this is that although not easily interpretable by inspection (as for example in mid-infrared absorbance spectra) the NIR spectra of hydrocarbon streams possess a very high information content. Use of suitable chemometric methods allows for the reduction of this information content into extremely powerful predictive models for not only chemical compositional properties, but also bulk physical and fuel properties of hydrocarbon process streams and prodncts.  

2 Polyols, ethoxylated derivatives, ethylene oxide/propylene oxide polyether polyols 

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Phenols are removed from refinery hydrocarbon streams by treating with a solution of sodium hydroxide in water. This produces a waste stream, which is difficult to treat in a bio-pond [75]. If feasible, this stream will be sold (or given) to a neighboring petrochemical plant if it can make use of the phenol content. Phenol is economically recovered from this stream by acidification using flue gases, followed by solvent extraction (Eq. 18.44). 

In Appendix 1, the reader will find the data required to calculate the properties of the most common hydrocarbons as well as those components that most frequently accompany them in refinery process streams. The data are grouped in seven categories ( ... 

Olefins are produced primarily by thermal cracking of a hydrocarbon feedstock which takes place at low residence time in the presence of steam in the tubes of a furnace. In the United States, natural gas Hquids derived from natural gas processing, primarily ethane [74-84-0] and propane [74-98-6] have been the dominant feedstock for olefins plants, accounting for about 50 to 70% of ethylene production. Most of the remainder has been based on cracking naphtha or gas oil hydrocarbon streams which are derived from cmde oil. Naphtha is a hydrocarbon fraction boiling between 40 and 170°C, whereas the gas oil fraction bods between about 310 and 490°C. These feedstocks, which have been used primarily by producers with refinery affiliations, account for most of the remainder of olefins production. In addition a substantial amount of propylene and a small amount of ethylene ate recovered from waste gases produced in petroleum refineries. 

The butane-containing streams in petroleum refineries come from a variety of different process units consequently, varying amounts of butanes in mixtures containing other light alkanes and alkenes are obtained. The most common recovery techniques for these streams are lean oil absorption and fractionation. A typical scheme involves feeding the light hydrocarbon stream to an absorber-stripper where methane is separated from the other hydrocarbons. The heavier fraction is then debutanized, depropanized, and de-ethanized by distillation to produce C, C, and C2 streams, respectively. Most often the stream contains butylenes and other unsaturates which must be removed by additional separation techniques if pure butanes are desired. 

Like ethylene, propylene (propene) is a reactive alkene that can be obtained from refinery gas streams, especially those from cracking processes. The main source of propylene, however, is steam cracking of hydrocarbons, where it is coproduced with ethylene. There is no special process for propylene production except the dehydrogenation of propane. 

The Ce-Cg aromatic hydrocarbons—though present in crude oil—are generally so low in concentration that it is not technically or economically feasible to separate them. However, an aromatic-rich mixture can be obtained from catalytic reforming and cracking processes, which can be further extracted to obtain the required aromatics for petrochemical use. Liquefied petroleum gases (C3-C4) from natural gas and refinery gas streams can also be catalytically converted into a liquid hydrocarbon mixture rich in C6-C8 aromatics. 

MHDV [Mobil Hydrogen Donor Visbreaking] A modified visbreaking process in which a hydrogen donor stream from the oil refinery is added to the heavy hydrocarbon stream before thermal cracking. Developed by Mobil Corporation... 

Minex A process for removing hydrogen sulfide and carbon dioxide from gases and light hydrocarbon streams in oil refineries. Developed by the Merichem Company, Houston, TX. 

The major discharges from sulfuric acid alkylation are the spent caustics from the neutralization of hydrocarbon streams leaving the alkylation reactor. These wastewaters contain dissolved and suspended solids, sulfides, oils, and other contaminants. Water drawn off from the overhead accumulators contains varying amounts of oil, sulfides, and other contaminants, but is not a major source of waste. Most refineries process the waste sulfuric acid stream from the reactor to recover clean acids, use it to neutralize other waste streams, or sell it. 

United States patent 5,684,580 by Cooper etal. of Ashland Inc. discusses monitoring the concentration of benzene and substituted aromatic hydrocarbons in multiple refinery process streams and using the results for process control.56 Xylene isomers can be differentiated by Raman spectroscopy, making it technically preferable to NIR. This patent is a good example of process Raman spectroscopy and subsequent process control. 

Butane A normally gaseous straight-chain or branch-chain hydrocarbon (C4H10), extracted from natural gas or refinery gas streams. It includes isobutane and normal butane. 

Another important factor that distinguishes this separation is that it is not environmentally or economically feasible to simply return a rejected stream to the environment, as in a typical aqueous RO process where the brine can be returned to the ocean. The federal regulations mandate that C02 emissions from refineries and chemical plants be reduced to low levels therefore, facilities can no longer afford to dispose of waste hydrocarbon streams in their flare systems. Pure streams from polyolefin reactors and vents from polymer-storage facilities, which were once flared, must be redirected to recovery systems. To reduce the economic penalty of environmental compliance, these paraffin and olefin mixtures must be recovered and recycled. In other words, two products must be made, a useful fuel and a useful chemical product, hence more process engineering is required in order to achieve such an objective. 

BTX (benzene-toluene-xylene) mixtures are an important petroleum refinery stream that is separated by extractive distillation (Fig. 1) from a hydrocarbon stream, usually a reformate, and followed by downstream fractionation for isolation of the pure materials for further treatment and use (Fig. 2). 

In a modern refinery the different hydrocarbon streams contain a variety of sulphur compounds, including hydrogen sulphide, mercaptans, sulphides, disulphides, and thiophenes. The amount and the type of the sulphur compounds depends highly on the used crude oil type, but even the most sweet (low sulphur) crudes contain considerable amounts of sulphur. For different reasons the sulphur concentration of the product streams of the crude destination train must be reduced ... 

Application To produce propylene and ethylene from low-value, light hydrocarbon streams from ethylene plants and refineries with feeds in the carbon number range of C4 to C8, such as steam cracker C4/C5 olefins, cat-cracker naphthas, or coker gasolines. 

XyMax A selective process for making p-xylene and o-xylene by isomerizing C8 aromatics-rich hydrocarbon streams, using a proprietary zeolite catalyst. Developed by ExxonMobil and first used in 2000 in its refinery on Jurong Island, Singapore. Five more units have subsequently been licensed. Retrofit applications are licensed by ExxonMobil Chemical, grassroots applications by Axens. 

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