Gas separation hydrocarbons

Summary This work is devoted to the systematic study of hydrocarbon gas separation parameters of polydimethylsilmethylene (I) and polysiltrimethylenes bearing various groups at the Si atom (R = R = Me (D), CH2Si(Me2)Ph (HI) R = Me, R = CH2SiMe3 (IV), (CH2)3SiMe3 (V), m-Tol (VI)) deposited on polyamide hollow fibers. 

Deep-cavity cavitands that dimerize into capsules via the hydrophobic effect, in the presence of a suitable guest molecule and in aqueous solution, have been developed by the Gibb group [110,111], Such complexes possess hydrophilic outer coats, hydrophobic rims that favor self-assembly, and deep hydrophobic pockets (up to 1 nm wide to 2 nm long). They have been used to drive the formation of high-definition assemblies with a number of guest molecules, including steroid and hydrocarbon molecules [112]. Reactions within the capsule (eg, selective oxidation of substrates) and potential applications in hydrocarbon gas separation [111] have been also achieved or demonstrated [113]. 

The hydrocarbon gas feedstock and Hquid sulfur are separately preheated in an externally fired tubular heater. When the gas reaches 480—650°C, it joins the vaporized sulfur. A special venturi nozzle can be used for mixing the two streams (81). The mixed stream flows through a radiantly-heated pipe cod, where some reaction takes place, before entering an adiabatic catalytic reactor. In the adiabatic reactor, the reaction goes to over 90% completion at a temperature of 580—635°C and a pressure of approximately 250—500 kPa (2.5—5.0 atm). Heater tubes are constmcted from high alloy stainless steel and reportedly must be replaced every 2—3 years (79,82—84). Furnaces are generally fired with natural gas or refinery gas, and heat transfer to the tube coil occurs primarily by radiation with no direct contact of the flames on the tubes. Design of the furnace is critical to achieve uniform heat around the tubes to avoid rapid corrosion at "hot spots."... 

In Sittt Filter Membranes In situ membranes are being fitted into incinerator flue-gas stacks in an attempt to reduce hydrocarbon emissions. Two types of commercially available gas separation membranes are being stndied (I) flat cellnlose acetate sheets and (2) hoUow-tnbe fiber modules made of polyamides. 

The reaction takes place at low temperature (40-60 °C), without any solvent, in two (or more, up to four) well-mixed reactors in series. The pressure is sufficient to maintain the reactants in the liquid phase (no gas phase). Mixing and heat removal are ensured by an external circulation loop. The two components of the catalytic system are injected separately into this reaction loop with precise flow control. The residence time could be between 5 and 10 hours. At the output of the reaction section, the effluent containing the catalyst is chemically neutralized and the catalyst residue is separated from the products by aqueous washing. The catalyst components are not recycled. Unconverted olefin and inert hydrocarbons are separated from the octenes by distillation columns. The catalytic system is sensitive to impurities that can coordinate strongly to the nickel metal center or can react with the alkylaluminium derivative (polyunsaturated hydrocarbons and polar compounds such as water). 

Figure 7.7b shows the essential features of a refinery catalytic cracker. Large molar mass hydrocarbon molecules are made to crack into smaller hydrocarbon molecules in the presence of a solid catalyst. The liquid hydrocarbon feed is atomized as it enters the catalytic cracking reactor and is mixed with the catalyst particles being carried by a flow of steam or light hydrocarbon gas. The mixture is carried up the riser and the reaction is essentially complete at the top of the riser. However, the reaction is accompanied by the deposition of carbon (coke) on the surface of the catalyst. The catalyst is separated from the gaseous products at the top of the reactor. The gaseous products leave the reactor... 

Example 10.1 A hydrocarbon gas stream containing benzene vapor is to have the benzene separated by absorption in a... 

The product mixture was analyzed with on-line connected gas chromatograph using mol sieve and HP-PLOT Q capillary column to separate permanent gases followed by detection with TCD saturated and unsaturated hydrocarbons were separated using PLOT Q and DB-VRX capillary columns and detected by FID. 

The discussion of Brouwer diagrams in this and the previous chapter make it clear that nonstoichiometric solids have an ionic and electronic component to the defect structure. In many solids one or the other of these dominates conductivity, so that materials can be loosely classified as insulators and ionic conductors or semiconductors with electronic conductivity. However, from a device point of view, especially for applications in fuel cells, batteries, electrochromic devices, and membranes for gas separation or hydrocarbon oxidation, there is considerable interest in materials in which the ionic and electronic contributions to the total conductivity are roughly equal. 

The produced oil or gas is connected to surface flowlines from the wellhead pumping unit or surface regulating valve assembly typically referred to as a Christmas tree but to its arrangement. The flowlines collect the oil or gas to local tank batteries or central production facilities for primary oil, water, and gas separation. The reliability of electrical submersible pumps (ESPs) has increased to the point where the submersible electrical pump is commonly used for the production of liquid hydrocarbons where artificial lift is required for production. 

The equilibria are readily reversed by heating and the salt loaded aqueous amine solutions can be made to release the carried H2S and CO2 after separation from the hydrocarbon gas being sweetened. 

Industrial analysis of hydrocarbon gases 25 years ago was limited almost to Orsat-type absorptions and combustion, resulting in crude approximations and inadequate qualitative information. The more precise method of Shepherd (56) was available but too tedious for frequent use. A great aid to the commercial development of hydrocarbon gas processes of separation and synthesis was the development and commercialization of high efficiency analytical gas distillation units by Podbielniak (50). In these the gaseous sample is liquefied by refrigeration, distilled through an efficient vertical packed column, the distillation fractions collected as gas and determined manometrically at constant volume. The operation was performed initially in manually operated units, more recently in substantially automatic assemblies. 

Gas specifications will be inqportant only if the gas is to be delivered to a gas pipeline system. If the gas is to be injected in the producing field the only usual critical requirement is to dehydrate the gas adequately to prevent hydrate formation anywhere in the system. The gas pipeline specification which most Influences the design of oil-gas separation systems is the hydrocarbon dewpoint limitation. This is usually expressed as a maximum dewpoint temperature at a specified pressure. For onshore gas pipelines in the USA end Europe this specification may be in the range of 32°F (0°C) at 1000 paia (68 atmospheres), which is adequate to prevent condensation of liquids in the pipelines in the normal range of onshore pipeline operating pressures from 900 to 1000 psl. In the USA this specification is seldom iiqposcd on producers and is controlled with pipeline facilities. 

It is apparent from the preceding discussion of objectives that two factors are most significant in the design of oil-gas separation systems. These are the vapor pressure of the crude oil, and gas pipeline considerations which influence the hydrocarbon dewpoint of the produced gas. Some further discussion of these two factors may be helpful. 

The line QiQj separates the area in which liquid water and hydrocarbon gas exist from the area in which liquid water and hydrate exist. This line represents the conditions at which gas and liquid water combine to form hydrate. 

Point Q2 is a quadruple point. At Q2, four phases are in equilibrium liquid water, hydrocarbon liquid, hydrocarbon gas, and solid hydrate. The almost vertical line extending from point Q2 separates the area of liquid water and hydrocarbon liquid from the area of liquid water and hydrate. 

Qi, which occurs at approximately 32°F, is also a quadruple point representing the point at which ice, hydrate, liquid water, and hydrocarbon gas exist in equilibrium. The vertical line extending from point Qj separates the area for hydrate and liquid water from the area for hydrate... 

Some of the advantages of 3S in comparison with conventional technologies for the separation of hydrocarbons from a mixed hydrocarbon gas stream are ... 

Natural gas is usually produced from the well and transported to the gas processing plant at high pressure, in the range 500-1500 psi. To minimize recompression costs, the membrane process must remove impurities from the gas into the permeate stream, leaving the methane, ethane, and other hydrocarbons in the high-pressure residue gas. This requirement determines the type of membranes that can be used for this separation. Figure 8.30 is a graphical representation of the factors of molecular size and condensability that affect selection of membranes for natural gas separations. 

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