Gas hourly space velocity GHSV

Both catalyst space velocity and bed geometry play a role. The gas hourly space velocity (GHSV) is used to relate the volumetric flow rate to the catalyst volume. GHSV has units of inverse hour and is defined as the volume flow rate per catalyst volume. 

Another commonly used term is the gas hourly space velocity (GHSV), which is defined as... 

The reactions were carried out in the steady state flow mode as described previously [11]. Differential kinetics were determined from plots of conversion vs. W/F. Three catalysts CoZSM-5, HZSM-5 and NaZSM-5 (Si/AI = 11) were studied in this work. The catalyst preparation and the standard pretreatment used prior to reaction have been described previously [11]. It involved dehydration in flowing dried 0 as the temperature was raised slowly to 500°C. The feed comprised CH4 (0.28%), NO (0.21 %) or NOj (0.21 %). and/or Oj (2.6%) in He. The flow rate was 75 ml/min and the gas hour space velocity (GHSV) was varied between 4,500 and 250,000 h by changing the weight of catalyst samples. 

However, the detailed description of the FT product distribution together with the reactant conversion is a very important task for the industrial practice, being an essential prerequisite for the industrialization of the process. In this work, a detailed kinetic model developed for the FTS over a cobalt-based catalyst is presented that represents an evolution of the model published previously by some of us.10 Such a model has been obtained on the basis of experimental data collected in a fixed bed microreactor under conditions relevant to industrial operations (temperature, 210-235°C pressure, 8-25 bar H2/CO feed molar ratio, 1.8-2.7 gas hourly space velocity, (GHSV) 2,000-7,000 cm3 (STP)/h/gcatalyst), and it is able to predict at the same time both the CO and H2 conversions and the hydrocarbon distribution up to a carbon number of 49. The model does not presently include the formation of alcohols and C02, whose selectivity is very low in the FTS on cobalt-based catalysts. 

The most common unit of <2rel is bed volumes per hour (BV/li). Space velocity is also used in catalytic reactors, especially in three-phase fixed-beds, and is referred to as liquid hourly space velocity (LHS V) for the liquid phase, and gas hourly space velocity (GHSV) for gas phase. As mentioned above, space-time and space velocity are measured under the entrance conditions. However, for space velocity, other conditions are frequently used (Fogler, 1999). For example, the LHSV is measured at 60 to 75 °F, and GHSV at standard temperature and pressure. 

Mass-related reaction rates, tm, were determined at normal pressure for the following ranges of operating conditions T = 473 to 503 K, xc6h12 = 2-6 vol%, normal pressure conditions at both membrane sides, gas hourly space velocity (GHSV) 400-1000 h-1. The composition of the effluent was measured under steady-state conditions using gas chromatography (GC). 

The effects of standard activation procedures (adopted by industry) and fast activation procedures (often reported in the literature) have been investigated by Lombardo and coworkers [80], In the standard activation procedure, the catalyst was heated in air up to reaction temperature, followed by introduction of the butane in three steps, up to 1.5%. The gas hourly space velocity (GHSV) was increased in four steps to 2500 h" . This procedure could take up to 380 hours. 

The key variables in the steam reforming experiments were the steara/carbon and tl /carbori ratio In the reactor feed and the gas hourly space velocity (GHSV) calculated for normal temperature and pressure (NTP), The H20/carbon and H2/carbon levels were varied according to the incidence of carbon deposition on each catalyst sample. The GHSV was adjusted at the beginning of each experiment to approximate differential conditions (<26 mol% conversion) of the hydrocarbon feedstcick into the product. Normal laboratory SNG production conditions wore as follows ... 

It should be operable at extreme high gas hourly space velocities (GHSVs), while the pressure drop over the catalyst bed should be low. 

In addition to the performance variations with reactant concentration and gas hourly space velocity (GHSV), there can be multiple steady states observed. Generally, a reactor in which a single, exothermic reaction is occurring will operate in one of two stable steady states. Additionally, an unstable steady-state solution to the mass... 

Catalytic oxidation reactions were carried out in a conventional fwed bed reactor under atmospheric pressure [10]. The flow rate through the reactor was set at 500 cm min and the gas hourly space velocity (GHSV) was set at 15000 h. The residence time based on the packing volume of the catalyst was 0.24 s. Following the reactor, a portion of the effluent stream was delivered and analysed on-line using a Hewlett Packard 5890 Series II gas chromatograph (GC) equipped with an electron capture detector (ECD) and a thermal conductivity detector (TCD), and controlled with HP ChemStation software. The concentration of the chlorinated feeds was determined by the ECD after being separated in a HP-VOC column. 

Another important feature of gas turbine operation is the very high velocity of the fuel/air mixture. For example, in a full scale catalytic combustor designed by General Electric [8], the air flow through the 51 cm diameter unit was 23 kg s . This corresponds to a gas hourly space velocity (GHSV) of 300 000 h" at 12 bar pressure and 450 °C. The catalyst must obviously be able to operate effectively at these very high gas velocities. 

Both powder and monolithic catalysts were evaluated for their activity and selectivity for PTA offgas destmction. For powder catalyst screening, a total of 1 ml of catalyst powder was placed on a quartz frit in a U-shaped, downflow reactor. A reactant mixture, which included carbon monoxide, methyl bromide, benzene, and methyl acetate, was used to represent an industrial PTA offgas. The concentrations of these compounds were 3500 ppm CO, 35 ppm CHjBr, 9 ppm and 410 ppm CH3CO2CH3, respectively. TTie gas hourly space velocity (GHSV) was... 

Catalytic activity was measured in a parallel reactor system, using 50 mg of catalyst (125-200 pm) and a gas-hourly space velocity (GHSV) of 60,000 h at atmospheric pressure. Three reactions were investigated (a) direct N2O decomposition (1.5 mbar N2O in He), (b) reduction of N2O by CO (1.5 mbar N2O +1.0 mbar CO in He), and (c) selective catalytic reduction of N2O with CaHg in the presence of excess oxygen (1.5 mbar N2O +... 

Figure 2 shows the development in the hydrocarbon formation rate as a function of time on stream for the experiments at elevated pressure. The vertical dotted lines marks the start and stop of water/syngas co-feeding. The gas hourly space velocity (GHSV) is adjusted after the co-feeding period to give the same level of CO conversion as prior to the introduction of water. It is seen that the promoted catalyst is significantly more active compared to the unpromoted one when no water pretreatment has taken place, but this difference is absent on the water treated catalysts. It is proposed that rhenium supports the reduction of cobalt, but the water pretreatment leads to a reoxidation of the active metal. 

Catalytic activity was evaluated in an integral quartz flow reactor in steady-state experiments carried out at 823 K and a gas hourly space velocity (GHSV) of 60,000 (calculated at standard conditions of temperature (293K) and pressure (1 atm)). The feed was a simulated automotive exhaust stream containing 1.5% CO, 0.5% H2, 1500 ppm HC (comprised of 1000 ppm propylene and 500 ppm... 

Similar quantities that are often used in the literature and which express the load on the catalyst are the liquid hourly space velocity (LHSV, Eq. 2.1-4), the gas hourly space velocity (GHSV, Eq. 2.1-5), and the weight hourly space velocity (WHSV, Eq. 2.1-6). 

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