
Control H2 Recycle H2O concentration for optimum catalyst performance and for catalyst regeneration control.
Application Note
Catalytic Reforming Unit
The Catalytic Reformer Unit of a modern refinery is an important process unit for converting lower octane naphtha streams into higher octane aromatic compounds.
These chemical conversions are done in catalytic reactors that transform straight-chain C6-C8 compounds found in the naphtha into light aromatics such as Benzene, Toluene and Xylenes (BTX). This high octane reformate can then be used in gasoline blending or sold to chemical plants.
Figure 1
As shown in Figure 1, depentanized naphtha feed is mixed with recycled Hydrogen gas, preheated and passed through a series of reactors where the conversion to aromatics takes place.
After the last reactor, a Hydrogen Separator strips out the hydrogen and other light gases from the stream. After the removal of the Hydrogen, the stream enters a Stabilizer Tower (also called a Debutanizer) that removes the Butanes and lighter gases with the Reformate leaving the Bottoms for gasoline blending or sent to a chemical plant.
Critical Control of Moisture
The catalyst in the reactors is very expensive and sensitive to poisoning if exposed to certain compounds; most notably H2 If left unchecked, the moisture damages the catalyst, thus shortening its life and resulting in costly replacement fees. Proper operation of the Reformer needs reliable monitoring of the moisture levels in the Hydrogen Recycle.
Traditional Measurement Solutions
Electrochemical moisture analyzers have been the traditional method for monitoring the levels of H2O in the Hydrogen Recycle stream. However, heavy hydrocarbons and trace HCl present in the stream contaminate electrochemical probes, which must then be replaced resulting in high maintenance costs. It’s not uncommon for moisture probes to be replaced multiple times a year.
SpectraSensors’ Solution
SpectraSensors SS2100 is the ideal solution for this challenging application. Its non-contact sensor is impervious to damage from contaminants. The use of Tunable Diode Laser technology means that measurement interferences from other infrared absorbing compounds are avoided. And being laser-based means there are no wet-up or dry-down delays, resulting in fast updates even when the concentration changes dramatically.
Dual Range / Dual Channel
Refineries normally operate at about 5 – 50 ppm moisture level in the hydrogen recycle stream. During catalyst regeneration moisture can be much higher. A Dual SS2100, with two measurement cells calibrated for different ranges in a single sample enclosure is the answer to this requirement.
The analyzer is supplied as a controller in a NEMA 4X enclosure with the cell and interconnecting cable supplied loose. SSI or a qualified systems integrator can supply sample conditioning system suitable to the application.
Typical Background Stream Composition
| Component | Maximum (Mole %) |
Normal (Mole %) |
Maximum (Mole %) |
| Hydrogen | 70 | 80 | 90 |
| Methane | 8 | 12 | 20 |
| Ethane | 3 | 5 | 10 |
| Propane | 0 | 2 | 5 |
| i-Butane |
0 |
1 |
2 |
| n-Butane |
0 |
<1 |
2 |
| C5+ |
0 |
0 |
1 |
Data Sheet
Performance |
|
|
Target Components |
H2O in Hydrogen Recycle Gas |
|
Typical Measurement Ranges |
0-50ppm
0-500ppm
0-1000ppm*
|
|
Typical Precision |
±2% of full scale* |
|
Measurement Response Time |
1 to ~60 sec |
|
Principle of Measurement |
Tunable Diode Laser Absorption Spectroscopy
Non-differential
|
|
Environmental Temperature Range |
-20º to 50ºC (-4º to 122ºF)
-10º to 60ºC (14º to 140ºF) optional
|
|
Sample Inlet Pressure |
70 kPag (10 PSIg) typical
210 kPag (30 PSIg) maximum |
|
Cell Temperature |
Maintain at 50ºC +/- 0.2ºC |
|
Maximum Cell Pressure |
70 kPag (10 PSIg) |
| Sample Flow Rate |
3-4 L/min (6.4 to 8.5 scfh)* |
| Validation |
Certified blend of H2O in pure N2 |
Electrical |
|
|
Power |
100-240 VAC, 50-60 Hz standard |
|
Max Current |
Controller: 1 A @ 120 VAC |
|
Controller to Cell Cable Length |
1m standard (3m, 5m & 10m available optionally) |
|
Communication |
Current Loop Output 4-20 mA Isolated,
1200 ohms @ 24 VDC max load
Serial: ASCII Text RS232C standard
Modbus RS232C
|
| Digital Outputs |
4 ea. 12 VDC for valve operations
Scrubber (if required), Process/Val, Val 1, Val 2
5 SPDT (Form C) Dry Contacts
Common Fault, Val 1 Active, Val 2 Active, Val Fail
Low Sample Flow
|
| LCD Display |
Concentration, Cell Pressure and Temperature, Diagnostic Data |
Physical |
|
|
Controller Enclosure |
NEMA 4X - Stainless Steel standard |
|
Dimensions |
343mm H x 305mm W x 165mm H
(13.5" H x 12" W x 6-7/16" D)*
|
|
Weight Approximately |
13.1 Kg (28.6 lbs)* |
|
Sample Cell Dimensions |
0.8m cell for ranges >100ppm
438mm H x 108mm W
(17-1/4” H × 4-1/4” W)* 28m cell for ranges <100 ppm 559 mm H × 127 mm W (22” H × 5” W) |
|
Sample Cell Construction |
316L Series Polished Stainless Steel standard |
| Number of Sample Cells |
1 (single channel SS2100) or
2 (dual channel SS2100)
|
| Area Classification |
CSA Certified for Class I, Division 2,
Groups B,C,D Temp Code T3C
|
|
Note: The Analyzer scope of supply is the controller and enclosure, the cell and the interconnecting cables. SSI or qualified systems integrator can supply sample conditioning systems appropriate to the applications.
* Application specific; consult factory
|
|
Typical Accessories
|
SS2100 ARM9 Electronics
|
|
|
80000-02199 |
Temperature Control Board |
|
23000-00030 |
4-20 mA Current Loop Board
|
|
80000-02203 |
Power Supply Assembly, 120/240 VAC 50/60 Hz
|
|
80000-02300 |
Power Supply Assembly, 24 VDC
|
| 01902-17106 | External Serial Output Cable |
| 01902-30011 | Keypad Assembly |
| 24601-00002 |
Display Assembly
|
| 02203-13100 |
Daughter Board
|
| 45000-02002 |
Relay, DC12V SPDT 3 A/120 VAC
|
| Herriott Cell (8m & 28m) |
|
| 02101-17102 |
Pressure Transducer Assembly
|
| 02101-17103 |
Thermistor Assembly
|
| 02199-00006 |
Spares Kit (o-rings, fuses), AC, Viton
|
| 02199-00007 |
Cleaning Kit (domestic only)
|
| Cell (0.8m) | |
| 01902-17102 |
Pressure Transducer Assembly
|
| 02199-00001 |
Spares/Cleaning Kit (o-rings, fuses), AC, Viton (domestic only)
|
| 02199-00005 |
Spares Kit (o-rings, fuses), AC, Viton
|

