Liquid hourly space velocity defined

The reactor feed may be preheated and the feed pressure may alter. The volumetric flowrate of gases depends on the reactor temperature and pressure at fixed mass flowrate. In many cases, the feed is liquid at room temperature, while the reaction mixture is a gas at the higher temperature in the reactor. In these instances, the performance of the reactor is represented as conversion and selectivity against the liquid hourly space velocity (LHSV). This is defined as... 

Note Typically in reformer design, liquid hourly space velocity (LHSV) is defined as fresh liquid charge volumetric flow rate divided by catalyst volume. Catalyst volume includes the void fraction and is defined by WJpp( — e).]... 

Convert the liquid-hourly space velocities in Prob. 3-6 to a gas basis, that is, to space velocities defined as the ratio of the gas-flow rate at reaction conditions to the total reactor volume. Then calculate the actual contact time for each run. The gases may be assumed to obey the perfect-gas law. The reaction does not result in a change in number of total moles. 

Other terms that are used when feeding liquids to a reactor are the weight hourly space velocity (WHSV) and the liquid hourly space velocity (LHSV) [3]. Both have units of hr but are defined differently ... 

As an aside, some authors use the term space velocity" such as, the liquid hourly space velocity, LHSV, the gas hourly space velocity, GHSV, the mass hourly space velocity, WHSV, or mol-volume space velocity, mol feed/hour litre of catalyst, MvolHSV. Unfortunately, the flowrates used in space velocity data are defined at conditions different from the typical reaction conditions. Thus, LHSV is measured at 20 °C GHSV, at 15 °C and 0.1 MPa. As an approximation, we can convert space velocity to residence time, in seconds, = 3600/(the hourly space velocity corrected to volumetric conditions using the temperature and pressure to reactor inlet conditions). 

Figure 3.52 depicts the dependence of methanol conversion and product composition on contact time as contact time increases, (reciprocal of the catalyst load), the yield of gasoUne and aromatics increases. (In English terminology, the catalyst load is defined as (LHSV) liquid hourly space velocity ). 

In industrial practice, the terms WHSV (weight hourly space velocity), LHSV (liquid hourly space velocity), and GHSV (gas hourly space velocity) are also used -defined as the ratio of the mass flow (WHSV) or volumetric flow (LHSVand GHSV, usually at STP) of the liquid or gaseous feed per volume of reactor. 

Another measure of the efficiency of ammonia conversion is the space velocity which may be used. Space velocity refers to the volume of reactants fed to a reactor per hour, divided by the volume of the reactor. For liquid reaction streams this relationship is straightforward. For gases, however, the space velocity is defined as being the volume of gases corrected to 0°C and 760 mm Hg (1 atm) passing through the reactor (or catalyst) volume/hour. This amounts to a measure of the gas-catalyst contact time for heterogeneous reaction (Eq. 11.7). 

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