Steam unconverted

With regard to the unconverted residue, the VI after dewaxing is 120 to 135 and the BMCI is between 10 and 15, which makes it an excellent feed for steam cracking units. 

Carbon Conversion. Carbon conversion on a once-through basis is a function of the coal composition and is strongly influenced by the oxygen/coal ratio. For some coals, the conversion pattern is also affected by the level of steam in the blast. Another factor is fly slag recycle, which raises the carbon conversion by recycling the unconverted carbon, most of which resides on the fly slag. This results in an overall carbon conversion greater than 99%. 

In the Monsanto/Lummus Crest process (Figure 10-3), fresh ethylbenzene with recycled unconverted ethylbenzene are mixed with superheated steam. The steam acts as a heating medium and as a diluent. The endothermic reaction is carried out in multiple radial bed reactors filled with proprietary catalysts. Radial beds minimize pressure drops across the reactor. A simulation and optimization of styrene plant based on the Lummus Monsanto process has been done by Sundaram et al. Yields could be predicted, and with the help of an optimizer, the best operating conditions can be found. Figure 10-4 shows the effect of steam-to-EB ratio, temperature, and pressure on the equilibrium conversion of ethylbenzene. Alternative routes for producing styrene have been sought. One approach is to dimerize butadiene to 4-vinyl-1-cyclohexene, followed by catalytic dehydrogenation to styrene ... 

The gaseous mixture containing H2, CO, and steam (and usually about 4% of unconverted methane) leaves the reformer at about 800-900°C. ft is cooled rapidly to about 350°C (thereby generating steam) and is fed to WGS reactors, where CO reacts with steam over a catalyst bed producing H2 and C02 ... 

The effect of steam treatment of ZSM-5 on its cracking activity and selectivity was measured with experiments using n-hexadecane feed. With the thermally treated ZSM-5 catalyst, concentration of the unconverted n-hexadecane in the product was not measurable while 507e of the feed was unconverted with the steam treated ZSM-5 catalyst (Table II). The lower limit of conversion with the thermally treated catalyst corresponding to detection limit of n-hexadecane is 99.99%. This lower limit suggests at least an order of magnitude reduction in apparent first order rate constant of the ZSM-5 catalyst upon steam treatment. The small reduction in crystallinity upon steaming cannot fully explain the dramatic activity loss. Loss of active sites due to dealumination of ZSM-5 can be postulated to explain the reduction in activity. 

Natural gas is reacted with steam on an Ni-based catalyst in a primary reformer to produce syngas at a residence time of several seconds, with an H2 CO ratio of 3 according to reaction (9.1). Reformed gas is obtained at about 930 °C and pressures of 15-30 bar. The CH4 conversion is typically 90-92% and the composition of the primary reformer outlet stream approaches that predicted by thermodynamic equilibrium for a CH4 H20 = 1 3 feed. A secondary autothermal reformer is placed just at the exit of the primary reformer in which the unconverted CH4 is reacted with O2 at the top of a refractory lined tube. The mixture is then equilibrated on an Ni catalyst located below the oxidation zone [21]. The main limit of the SR reaction is thermodynamics, which determines very high conversions only at temperatures above 900 °C. The catalyst activity is important but not decisive, with the heat transfer coefficient of the internal tube wall being the rate-limiting parameter [19, 20]. 

In order to remove the small amount of unconverted vinyl acetate, steam is blown through the suspension for about 30 min, the flask being fitted with a condenser for distillation.The suspension is finally cooled externally to room temperature and diluted with cold water to about 500 ml. Only now is the stirrer switched off and after settle-... 

Reactor effluent is cooled to remove the steam, compressed to 285 psig, passed through an activated alumina drying system to remove further amounts of water, and then fed to the first fractionator. In that vessel, 95% of the unconverted propane is recovered as a bottoms product. This stream also contains 3%... 

Gasification by low-temperature steam-reforming reactions, the heart of die MRG process, is carried out between liquid hydrocarbons and steam over catalyst to fonn methane, hydrogen, and carbon oxides. In order to increase the calonfic value of product gas to the values similar to natural gas, methanation reactions are required. Hydrogen in product gas is reacted with C02 and CO to form methane, with only a small portion unconverted. Methanation reactions are ... 

Significant amounts of CH4 and C2H2 are also formed but will be ignored for the purposes of this example. The ethane is diluted with steam and passed through a tubular furnace. Steam is used for reasons very similar to those in the case of ethylbenzene pyrolysis (Section 1.3.2., Example 1.1) in particular it reduces the amounts of undesired byproducts. The economic optimum proportion of steam is, however, rather less than in the case of ethylbenzene. We will suppose that the reaction is to be carried out in an isothermal tubular reactor which will be maintained at 900°C. Ethane will be supplied to the reactor at a rate of 20 tonne/h it will be diluted with steam in the ratio 0.3 mole steam 1 mole ethane. The required fractional conversion of ethane is 0.6 (the conversion per pass is relatively low to reduce byproduct formation unconverted ethane is separated and recycled). The operating pressure is 1.4 bar total, and will be assumed constant, i.e. the pressure drop through the reactor will be neglected. 

In the cracker, heavy oil cracking and the steam-iron reaction take place simultaneously under conditions similar to thermal cracking. Any unconverted feedstock is recycled to the cracker from the bottom of the scrubber. The scrubber effluent is separated into hydrogen gas, liquefied petroleum gas (LPG), and liquid products that can be upgraded by conventional technologies to priority products. 

The concept of the system was to vaporize/preheat a methanol/air mixture, combust it in a separate combustor and feed the methanol steam reforming reaction with the energy of the hot combustion gases (see Figure 2.75). light-off of the combustion gases occurred at 70 °C [115]. The combustion gases were further used subsequently to supply the fuel pre-heater/evaporator of the combustor and finally the fuel pre-heater/evaporator of the reformer. Unconverted methanol and water were removed in a separator from the reformate prior to GC analysis. 

The ammonia loop is based on the Ammonia Casale axial-radial three-bed converter with internal heat exchangers. Heat from the ammonia synthesis is used to 1) generate high-pressure steam and 2) preheat feed gas. The gas is then cooled and refrigerated to separate ammonia product. Unconverted gas is recycled to the syngas compressor208 214... 

The reactor effluent, which contains unconverted NH3 and C02, is stripped in a falling-film type shell and tube exchanger at reactor pressure. The stripping agent, CO2, flows upward, which is countercurrent to the effluent stream. The stripper tubes are make of 25-22-2 stainless steel, which has lasted almost 30 years in some plants. The stripped-off NH3 and CO2 are then partially condensed and recycled to the reactor. The heat from this condensation is used to make 4.5 bar steam. Some of this steam can be used in downstream sections of the plant while some is sent to the turbine on the CO2 compressor108,110. 

The heat of condensation is recovered as 7.0 bar steam for use in downstream process steps. Urea solution leaving the IDR loop contains unconverted NH3, C02, and carbamate. These unconverted compounds are recycled to the synthesis loop108,110 ... 

In practice, the process is effected as follows, Crude m- xylene, containing 60-70% of m- xylene, is mixed with sulphuric acid (sp. gr. 1.84) whereupon the temperature rises to 45°C. Then the mixture is heated to 50°C and allowed to remain at this temperature for 2 hr. Under these conditions sulphonation of the o- and m- isomers takes place. The sulphonic acids may be separated from unconverted p- xylene either by extraction with water or by expelling the p- xylene by steam distillation. 

Optionally, the gasifier may be fed with a slurry of coal in oil and a controlled amount of reaction temperature moderator, such as steam. Facilities for recycling unconverted coal are also provided. A schematic flow diagram of the process is shown in Figure 2. 

In practice, gas mixtures containing carbon monoxide (CO) as well as carbon dioxide (C02) and unconverted methane (CH4) are produced and require further processing. The reaction of CO with steam (water-gas shift) over a catalyst produces additional hydrogen and C02, and after purification, high-purity hydrogen (H2) is recovered. In most cases,... 

Description Natural gas is preheated and desulfurized. After desulfurization, the gas is saturated with a mixture of preheated process water from the distillation section and process condensate in the saturator. The gas is further preheated and mixed with steam as required for the pre-reforming process. In the pre-reformer, the gas is converted to H2, C02 and CH4. Final preheating of the gas is achieved in the fired heater. In the autothermal reformer, the gas is reformed with steam and 02. The product gas contains H2, CO, C02 and a small amount of unconverted CH4 and inerts together with undercomposed steam. The reformed gas leaving the autothermal reformer represents a considerable amount of... 

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