Hydrogen petrochemical processes

Most refinery/petrochemical processes produce ethylene that contains trace amounts of acetylene, which is difficult to remove even with cryogenic distillation. Frequently it is necessary to lower the acetylene concentration from several hundreds ppm to < 10 ppm in order to avoid poisoning catalysts used in subsequent ethylene consuming processes, such as polymeri2ation to polyethylene. This can be accompHshed with catalytic hydrogenation according to the equation. 

The purge gas from a petrochemical process is at 25°C and contains a mole fraction of methane of 0.6, the balance being hydrogen. This purge gas is to be burnt in a furnace to provide heat to a process with a cold stream pinch temperature of 150°C (A= 50°C). Ambient temperature is 10°C. 

The solubility of gaseous weak electrolytes in aqueous solutions is encountered in many chemical and petrochemical processes. In comparison to vapory-liquid equilibria in non reacting systems the solubility of gaseous weak electrolytes like ammonia, carbondioxide, hydrogen sulfide and sulfur dioxide in water results not only from physical (vapor-liquid) equilibrium but also from chemical equilibrium in the liquid phase. 

Light hydrocarbons from nitrogen or hydrogen Reactor purge gas, petrochemical process streams, refinery waste gas Application is expanding rapidly... 

Technical solutions to produce hydrogen using nuclear energy and electrolysis will then be described. We mill describe the relevant characteristics of alkaline electrolyser technology. Using results of nuclear-aided petrochemical processes technico-economic studies, we mill show that synthetic fuels are accessible at reasonable costs. 

Hydrogen is present in fossil fuels and water in sufficient quantities that it can be produced on a large scale by three different methods 1) Petrochemical Processes, 2) Coal-based Chemical Processes and 3) Electrochemical Processes (Electrolysis). In Table 5.7, the percentage of hydrogen production is broken down by type of manufacturing process for the years between 1974 and 198846. A similar distribution for 2002 is shown in Table 5.8162. 

In the Petrochemical Processes, both natural gas and crude oil fractions can be converted into synthesis gas (a mixture of hydrogen and carbon monoxide) using two basically different methods46 ... 

The first purification plant that used PSA was developed by Union Carbide Corporation (UCC) and was built at the Yokkaichi Plant of Mitsubishi Petrochemical Industries in 19714. This process used several adsorbent beds and a complex valving system to produce high purity hydrogen. The process is now licensed by UOP and more than 400 units were operating worldwide in 19921. 

In a number of petrochemical processes, a gas (hydrogen) is present as reactant. In hydrodesulfurization (HDS), hydrocracking (HC), and hydrodenitrogenation (HDN), the reaction products H2S and ammonia, respectively, are known to decrease the catalyst activity, but are partly transferred to the gas phase. Therefore, also these processes profit from reactive stripping. 

CDHydro [Catalytic Distillation Hydrogenation] A family of petrochemical processes that combine "catalytic hydrogenation with fractional distillation in one unit operation. Most involve the selective hydrogenation of diolefins in C3 to C6 hydrocarbon fractions. Developed by CDTECH, a partnership between Chemical Research Licensing Company and ABB Lummus Crest (now ABB Lummus Global). The first plant was built at Shell s Norco, LA, site in 1994. Ten units were operating in 1997. 

A number of petrochemical processes produce significant volumes of hydrogen as a by-product, including pyrolysis cracking. This can be used as a fuel oil substitute, but this greatly undervalues hydrogen, and alternative use in other chemical processes is the better option and generally pursued by successful operations. 

BASF-AG/ABB Lummus Global Process described in Petrochemical Processes 2005 Hydrocarbon Processing and B. Heida, G. Bohner and K. Kindler, Hydrocarbon Processing, Mar. 2002, p. 50B other processes described in Petrochemical Processes include UOP KLP Process which involves selective hydrogenation of acetylenes Petrochemical Processes 2005 , Hydrocarbon Processing,, CD ROM, p. 38-41. 

Hydrogen is also formed in large quantities as a byproduct in petrochemical processes, refineries, coking plants (coke oven gas) and in chemical and electrochemical processes e.g. chloralkali-electrolysis. Other processes such as the photochemical production of hydrogen or thermal dissociation of water are only used in special applications and are currently industrially unimportant. 

In this section, several of commercial hydrogen production processes based on recovery of hydrogen from syngas mixture or other petrochemical offgas mixture are briefly summarized. Other commercial hydrogen production processes using natural gas as feedstock are covered in Chapter 4. 

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