From Naphtha to Synthesis Gas: The Steam Reforming Process

Synthesis gas, a crucial mixture of hydrogen (H2) and carbon monoxide (CO), serves as a building block for numerous petrochemicals. Steam reforming of naphtha, a hydrocarbon mixture derived from crude oil, is a prominent method for producing this valuable gas. Let's explore the process flow, step by step.

Synthesis gas production from naphtha by steam reforming

Naphtha Steam Reforming Process

Step 1: Naphtha Vaporization and Preheating

The journey begins with liquid naphtha. It's first vaporized and then preheated to about 220°C. This initial heating step is crucial for preparing the naphtha for the subsequent reactions.

Step 2: Hydrogenation and Desulfurization

Next, the vaporized naphtha is heated further to around 380°C in a fired heater. This temperature is optimal for the hydrogenation reaction. During this stage, sulfur compounds present in the naphtha react with hydrogen, transforming into hydrogen sulfide (H2S).

Removal of Sulfur Compounds

Sulfur is a catalyst poison for the downstream reforming process, so its removal is essential. The H2S is then absorbed and removed, typically using a zinc-based absorbent.

Step 3: Adiabatic Pre-Reformer

The desulfurized naphtha, now free from sulfur, enters an adiabatic pre-reformer. Inside the pre-reformer, the heavier hydrocarbons in the naphtha undergo partial reforming, converting into simpler molecules like methane (CH4), carbon monoxide (CO), carbon dioxide (CO2), and more hydrogen (H2).

Step 4: Steam Reformer

The partially reformed gas mixture proceeds to the steam reformer. This is where the bulk of the reforming takes place. The reformer consists of catalyst-filled tubes positioned vertically within a furnace.

Reforming Reactions

The high temperature and steam-rich environment in the reformer further convert methane and other hydrocarbons into more H2, CO, and CO2.

Step 5: Secondary Reformer (with Air Injection)

The gas stream from the steam reformer enters a secondary reformer. Here, air is injected into the mixture. The oxygen in the air reacts with the remaining hydrocarbons and some of the CO, further increasing the hydrogen content.

Step 6: Waste Heat Recovery

The hot synthesis gas exiting the secondary reformer contains valuable thermal energy. This heat is recovered using a waste heat boiler to generate process steam, which can be used elsewhere in the plant, improving the overall energy efficiency of the process.

Step 7: Synthesis Gas Composition

The resulting synthesis gas from the secondary reformer has a typical composition (in mole percent) of approximately: 

• H2: 51.52% 
• N2: 22.79% 
• CO: 13.57% 
• CO2: 11.25% 
• Ar: 0.27% 
• CH4: 0.60%

Here are the reforming reactions for the naphtha steam reforming process:

Reforming Reactions

Primary Reforming Reaction

• C_nH_m + nH₂O → nCO + (n + m/2)H₂

Secondary Reforming Reaction (with Air Injection)

• CO + 1/2O₂ → CO₂
• CH₄ + 2O₂ → CO₂ + 2H₂O
• C_nH_m + (n + m/4)O₂ → nCO₂ + (m/2)H₂O

Shift Conversion Reactions

• CO + H₂O → CO₂ + H₂ (High-Temperature Shift)
• CO + H₂O → CO₂ + H₂ (Low-Temperature Shift)

Methanation Reaction

• CO + 3H₂ → CH₄ + H₂O
• CO₂ + 4H₂ → CH₄ + 2H₂O

Key Advantages of Naphtha Steam Reforming

Established Technology

Steam reforming of naphtha is a well-established and widely used technology.

High Efficiency

The process can achieve high conversion rates and efficient heat recovery.

Versatile Feedstock

Naphtha is readily available in many refineries.

Sugarcane to Sugar: A Process Flow Diagram

The Sugar Story: Uncovering the Process Flow Diagram of Sugarcane Sugar Production

 

Sugar factory processes sugarcane with different unit operations such as the crushing of cane (using roller milling), the concentration of thin sugar cane juice to syrup (using vacuum pan evaporators), converting syrup to crystals by boiling (using evaporators), separation of crystals from the liquor by centrifuge equipment, sizing of sugar by crystal size, etc.

Factory operations description:

Cane from the field is brought to the factory through lorries and unloaded to cane trolleys 5-6 ft long canes are weighed in the electronic weighbridges and conveyed to tilting tables, pushers, and hailers. Preparatory devices such as knives, cutters, etc are used to get cane pieces and fed to mill tandem, which consists of 4 nos.  3 -rollers mills (usually). The juice is extracted by exerting pressure on the top rollers of each of these mills. Fresh water known as imbibition water is sprayed on the blanket of the bagasse to dilute the juice contained in the bagasse for complete extraction. The mixed juice obtained at different mills is known as mixed raw juice. The bagasse obtained from the last mill is used as fuel in the boiler for steam generation. It consists of 50% moisture and 2% sugar bagasse, which can also be used for paper manufacture, furfural, cattle feed, briquettes, etc.

The mixed juice consists of sugar, glucose, fructose, and many other salts. It also contains coloring matter. It has a pH of 5.8 and total dissolved solids or Brix may vary from 15 to 18%. It is necessary to remove all the impurities and raise the pH and Brix of the raw juice. To this, first, the juice is weighed and preheated to 70^oC. Then it is sent to the sulphitor where SO2 and lime are added. This sulphited juice is further heated to 105^oC in the juice heaters. Then it is fed to the clarifier before that magmafloc is added which helps in the quick settling of mud in the clarifier and clear juice is fed to the evaporators.

The muddy juice along with bagacillo is fed to the vacuum filters. The mud will be separated from the juice in the vacuum filters. Filtered juice is sent back to process and filter cake will be sent out. Filter cake is a byproduct, which we can make waxes and it can be used as manure to the sugar cane fields.

The clear juice is fed to the multiple effect evaporators where the thin juice of 150Bx is concentrated to syrup of 60o Bx after evaporation; the syrup is fed to a sulphitor. Here SO2 is added, so this process is known as the double sulphation process. The syrup is further concentrated in vacuum pans to form crystals. A mixture of mother liquor and crystal is called Massecuite. The boiling is stopped after achieving the required size of crystals and it is dropped into a crystallizer. The stirrer keeps the Massecuite in motion in the crystallizer, until the Massecuite is cooled to optimum temperature for further growth crystals.

This Massecuite is fed to the centrifuges through the pug mills where the sugar and molasses will be separated. The sugar from the centrifuge is dried and cooled while passing through hoppers and fed to bucket elevators. The sugar is graded according to its crystal size and stored in bins. Finally bagged through automatic weighers, stitched, and stored in the godown.

Equipment details and specifications based on a production capacity of 500 metric tons per day of sugar from sugarcane

Equipment	Capacity	Type	Motor Power	Speed	Voltage	Current	Other Specifications
Cane Unloader	500 MT/day	Hydraulic/Pneumatic	30-50 HP	10-20 RPM	440V, 3-phase, 50Hz	50-100 A	-
Cane Crusher	" "	4-Roll/5-Roll Mill	100-150 HP	20-30 RPM	" "	150-250 A	Roll Dia.: 800-1000 mm, Roll Length: 1500-2000 mm
Juice Extractor	" "	3-Roll/4-Roll Mill	150-200 HP	" "	" "	200-300 A	Roll Dia.: 800-1000 mm, Roll Length: 1500-2000 mm
Clarifier	" "	Sedimentation/Centrifugal	20-50 HP	10-20 RPM	" "	20-50 A	Dia.: 2000-3000 mm, Height: 3000-4000 mm
Evaporators	" "	MEE	50-100 HP	" "	" "	50-100 A	Heating Surface Area: 1000-1500 m², Steam Consumption: 2-3 tons/hour
Crystallizers	" "	Vacuum Crystallizers	" "	" "	" "	" "	Cooling Surface Area: 500-1000 m², Vacuum Pressure: 500-700 mmHg
Centrifuges	" "	Basket/Screen Centrifuges	100-200 HP	20-30 RPM	" "	150-250 A	Bowl Dia.: 800-1200 mm, Bowl Length: 1500-2000 mm
Sugar Dryers	" "	Rotary/Flash Dryers	50-100 HP	10-20 RPM	" "	50-100 A	Heating Surface Area: 500-1000 m², Drying Temperature: 80-100°C, Air Flow: 5000-10000 m³/h
Conveyor Systems	" "	Belt Conveyors/Chain Conveyors	20-50 HP	" "	" "	20-50 A	Belt Width: 800-1200 mm, Belt Length: 50-100 meters

Utilities and Services: (Capacity and Type)

Utilities and Services	Capacity	Type	Fuel/Source	Other Specifications
Steam Generation	10-15 tons/hour	Boiler	Bagasse or Coal	Operating Pressure: 10-20 bar, Operating Temperature: 180-200°C
Power Generation	1-2 MW	Steam Turbine or Diesel Generator	Steam or Diesel	Frequency: 50 Hz, Voltage: 440V, Efficiency: 80-90%
Water Supply	500-1000 m³/day	Well or Municipal Water Supply	Groundwater or Municipal Water	Water Quality: Potable, Treatment: Filtration and Disinfection
Effluent Treatment	500-1000 m³/day	Biological or Chemical Treatment	-	Treatment Process: Aerobic/Anaerobic, Effluent Quality: Reusable for Irrigation

Pump Sizing Calculator for Domestic and Industrial Application

Pump Sizing Calculator

Flow Rate (Q): GPMLPMm³/s Static Head (Hs): mft Pressure Head (Hp): mftpsi Pipe Diameter (D): mft Pipe Length (L): mft Pipe Roughness (ε): mft (e.g., 0.00015 for steel) Fluid Viscosity (μ): Pa·scP (e.g., 0.001 for water) Fluid Density (ρ): kg/m³lb/ft³ (e.g., 1000 for water)

Unit Conversion: For flow rate (GPM, LPM, m³/s), head (m, ft, psi), diameter and roughness (m, ft), viscosity (Pa·s, cP), and density (kg/m³, lb/ft³).

Reynolds Number Calculation: To determine the flow regime (laminar or turbulent) to select the appropriate friction factor equation.

Colebrook-White Approximation: A suitable approximation of the Colebrook-White equation for the friction factor (f) is used. This avoids the need for the Moody chart lookup.

Turbulent Flow Assumption: The simplified friction factor calculation is valid for turbulent flow (generally Re > 4000), which is common in most pump systems. For laminar flow, a different equation would be needed.

Pump Power Calculation: The pump power calculation now includes a pump efficiency factor (η). You can adjust this value as needed.

The Silent Struggle: When Pumps Don't Speak Your Language

Imagine a bustling factory floor. Machines hum, gears grind, and fluids flow, the lifeblood of the operation. At the heart of it all sits a pump, tirelessly pushing liquid through pipes, a silent workhorse. But what happens when this vital organ falters? What if the flow is sluggish, the pressure erratic? More often than not, the culprit isn't a mechanical failure, but a simple miscommunication – the pump just isn't speaking the system's language. It's a problem of improper sizing.

We've talked about the basics: flow rate, head, friction loss. Every online calculator covers that. But pump sizing is more than plugging numbers into equations. It's about understanding the story your system is trying to tell.

Let's take the case of a brewery. They're not just pumping water; it's a complex dance of wort, beer, and cleaning solutions, each with its own viscosity, temperature profile, and chemical properties. A standard centrifugal pump might handle the initial water stages, but what about the thick, viscous wort during the brewing process? Suddenly, friction losses skyrocket, the pump struggles, and the brewmaster's dream of the perfect IPA turns into a foamy nightmare.

This is where the deeper understanding comes in. It's not just about Darcy-Weisbach; it's about rheology. How does the fluid's viscosity change with shear rate? Is it shear-thinning, shear-thickening, or something in between? A simple online calculator won't tell you that. You need specialized testing, maybe even CFD simulations, to truly understand the fluid's behavior.

And what about the pipes themselves? We often think of smooth, uniform conduits. But real-world systems are messy. They have elbows, bends, valves, and sometimes even unexpected obstructions. Calculating equivalent lengths is a good start, but it's an approximation. What about the biofilm that builds up inside the pipes over time, increasing roughness and restricting flow? That's not in any textbook equation.

Then there's the human factor. Operators might tweak settings, maintenance crews might replace components with slightly different ones, and suddenly, the carefully calculated pump is no longer operating at its sweet spot. It's a dynamic system, constantly evolving, and the pump needs to be able to adapt.

This is where the real artistry of pump sizing comes in. It's not just about picking a pump; it's about designing a system. It's about understanding the fluid's personality, the pipe network's quirks, and the human element's unpredictability. It's about anticipating the unexpected and building in flexibility.

We've built a calculator, yes, but it's not just a black box spitting out numbers. It's a tool for exploration. Play with the inputs. See how viscosity changes things. Experiment with different pipe sizes. Use it to understand the why behind the numbers, not just the what.

Pump sizing isn't a science; it's a conversation. It's about listening to the system, understanding its needs, and choosing a pump that speaks its language. And sometimes, it requires a little bit of magic.