How to Use Moisture Analyzers to Improve CCR Efficiency

The catalytic reforming process

Catalytic reforming was developed to produce high-octane aromatic compounds from petroleum-quality naphtha that had previously been distilled from crude oil.  Today, these high-octane products are used for blending in gasoline, with by-products from the process also being used for the manufacture of plastics and as hydrogen feedstocks.  Hydrogen by-product is also reused within the reforming process itself.

Continuous catalytic reforming (CCR) takes a feed of desulphurized naphtha blended with hydrogen, which is heated to between 450°C and 520°C and then fed through a series of stacked reactors containing catalyst materials to facilitate a number of chemical processes.  These include:

The dehydrogenation process stages are endothermic, so additional heating is added at subsequent stages of the process.  The hot reaction products from the final reaction stage are then passed to a gas separator, where hydrogen is removed, before the liquid phase in the separator is transferred to a fractionation column or stabilizer.  Here, the liquid bottoms, or reformates, are removed for future gasoline blending, while the off-gases or light ends are sent for further processing to recover butane and propane.

The metallic catalyst materials are critical to the different reaction stages as they act as sites for the different chemical reactions.  They also have to undergo regular regeneration.  In a CCR plant, this is a continuous process, with a proportion of the catalyst being extracted from the base of the reactor, passed through a regeneration unit and then returned to the head of the reactor vessel.

Although catalytic materials vary, they typically use a bi-metal configuration of platinum and another metal such as rhenium or tin, on a base support of chlorided gamma alumina.

Moisture and catalytic reforming

One of the challenges to efficiently operating a CCR process is the management of moisture levels – in particular, in the hydrogen that is produced during the dehydrogenation phase and before it is remixed with the naphtha feedstock.  The reinjected hydrogen must have a carefully controlled level of moisture, within the 10…20 ppmV range.  This is to ensure that when hydrochloric acid is periodically injected into the reactor – to chlorinate the alumina and maintain the various acid sites – the acidity of the catalyst is maintained at optimum levels.

If the moisture level falls below 10 ppmV, the catalyst will begin to deteriorate, causing a loss of productivity.  Conversely, high moisture levels will strip chloride from the catalyst and reduce the effectiveness of catalytic cracking and isomerization.  Additionally, chlorides may react to form hydrochloric acid vapor that is caried through the process train, or form ammonium chloride salts; in each case, there is the risk of damage to downstream equipment.

Moisture monitoring systems for continuous catalyst reforming

The latest version of our proven QMA601 Moisture Analyzer has been developed to ensure that levels of moisture are measured accurately and consistently – and, as a result, to help optimize operational efficiency and productivity.  This precision instrument features Quartz Crystal Microbalance Technology and has an asymmetric cycle option to protect the sensor and reduce maintenance requirements in aggressive environments; this provides a sampling time of 30 seconds, with the sensor then being isolated and purged.

The instrument is capable of detecting moisture levels down to 0.1 ppmV, with a fast response speed, accuracy to within ±0.1 ppmV or 10 % (whichever is greater) and repeatability of ±5 % across its measuring range of 0.1…2,000 ppmV.  The QMA601 is IECEx, ATEX and UKCA certified for Exd flameproof, and cQPSus certified for explosion proof environments.