Industrial H2SO4 Production Process
- Contact Process — H2SO4 production technology accounting for >95% of global output
- 3 Main Stages: Burning S → SO2 → Oxidizing SO2 to SO3 (V2O5 catalyst) → Absorbing SO3 to produce H2SO4
- Raw Materials: Elemental sulfur (S), pyrite (FeS2), or SO2 gas from non-ferrous metallurgy
- V2O5 Catalyst — optimal operation at 420-450°C, SO2 conversion efficiency >99.5%
- Bulk Purchase of 98% H2SO4: Call 0979 891 929 — quote within 15 minutes
1. Overview — How is H2SO4 Produced?
Sulfuric acid is the most produced industrial chemical globally, with total output exceeding 260 million tons/year. Over 95% of global H2SO4 is produced via the Contact Process — patented by Peregrine Phillips in 1831 and continuously improved to date.
Historically, there are two industrial H2SO4 production methods:
| Method | Product Concentration | Efficiency | Current Status |
|---|---|---|---|
| Contact Process | 98-99% | SO2 → SO3 >99.5% | Global industrial standard |
| Chamber Process | 60-78% | Low, uneconomical | Obsolete, no longer used |
This article focuses on the Contact Process — the only process still operated in modern industry.
2. Raw Materials
Three sulfur-containing raw materials for H2SO4 production:
2.1. Elemental Sulfur (S) — accounts for ~70% of global H2SO4 production
Sulfur is recovered from oil and natural gas refining (Claus Process). This is the cleanest raw material, with minimal impurities, yielding the highest quality H2SO4.
Technical Specifications:
- Purity: >99.5% S
- Impurities: As <1 ppm, Se <1 ppm
- Form: Solid, pellets or powder, yellow
2.2. Iron Pyrite (FeS2) — accounts for ~20% of production
Pyrite is roasted in a fluidized bed furnace at 800-900°C: 4FeS2 + 11O2 → 2Fe2O3 + 8SO2. The by-product Fe2O3 is used in cement production. Common in China — home to large pyrite deposits.
2.3. SO2 Gas from Metallurgy — accounts for ~10% of production
Exhaust gas from copper, zinc, and lead ore smelting contains SO2 (5-15% vol), which is recovered instead of being emitted. This is a sustainable production direction — reducing SO2 emissions while producing commercial H2SO4.
3. Contact Process — 3 Main Stages
Stage 1: Burning Sulfur to Produce SO2
Molten sulfur (~140°C) is sprayed into a combustion chamber with dry air:
S(l) + O2(g) → SO2(g) ΔH = -297 kJ/mol
Operating Parameters:
| Parameter | Value |
|---|---|
| Combustion Chamber Temperature | 1000-1100°C |
| Outlet SO2 Concentration | 10-12% vol |
| Excess O2 Concentration | 8-10% vol |
| Pressure | 1-2 bar |
SO2 gas is cooled via a waste heat boiler — generating high-pressure steam for turbine power generation in the plant. Temperature drops from ~1000°C to ~420°C before entering Stage 2.
Stage 2: Oxidizing SO2 to SO3 (V2O5 Catalyst)
This is the heart of the Contact Process:
2SO2(g) + O2(g) ⇌ 2SO3(g) ΔH = -198 kJ/mol
Vanadium Pentoxide (V2O5) Catalyst:
| Parameter | Value |
|---|---|
| Active Component | V2O5 (5-8%) on SiO2 support |
| Operating Temperature | 420-450°C (optimal) |
| Minimum Temperature | ~400°C (below this, activity drops sharply) |
| Catalyst Lifespan | 5-10 years (stable operation) |
| Catalyst Poisons | Arsenic (As), Fluorine (F), Chlorine (Cl) |
Le Chatelier’s Principle of Equilibrium: The reaction is exothermic and reduces volume (3 moles gas → 2 moles gas). To achieve high efficiency:
- Low Temperature (420-450°C): Shifts equilibrium towards SO3
- High Pressure (1.5-3 bar): Increases efficiency, reduces equipment size
- Excess O2: Maintains O2/SO2 ratio ≥ 1.1
Multi-bed Converter System: Modern plants use 4-5 catalyst beds in series with intermediate cooling. After each bed, the gas is cooled to optimize equilibrium for the next bed:
| Bed | Inlet Temperature | Outlet Temperature | Cumulative Conversion |
|---|---|---|---|
| Bed 1 | 420°C | 600°C | ~70% |
| Bed 2 | 440°C | 520°C | ~90% |
| Bed 3 | 430°C | 460°C | ~97% |
| Bed 4 | 420°C | 435°C | ~99.5% |
Total SO2 conversion efficiency exceeds 99.5% — only <0.05% residual SO2 is treated via scrubber before emission.
Stage 3: Absorbing SO3 to Produce H2SO4
SO3 is not directly absorbed into water because the reaction is too violent, creating uncontrollable acid mist. Instead, SO3 is absorbed into 98% H2SO4 in an absorption tower:
SO3(g) + H2SO4(l) → H2S2O7(l) (oleum / disulfuric acid)
Oleum is then hydrolyzed with precisely calculated water:
H2S2O7(l) + H2O(l) → 2H2SO4(l)
Absorption Tower Parameters:
| Parameter | Value |
|---|---|
| Circulating H2SO4 Concentration | 98.5% |
| Absorption Temperature | 70-90°C |
| Tower Material | Carbon steel lined with acid-proof brick |
| Packing Material | Ceramic saddles |
The final product is 98-99% H2SO4 — cooled via heat exchanger to ~40°C before pumping into storage tanks.
4. Energy Recovery & Emission Control Technologies
Modern H2SO4 plants are net energy exporters. All three main reactions are strongly exothermic:
| Reaction | Heat Released (kJ/mol) | Recovery Application |
|---|---|---|
| S + O2 → SO2 | -297 | High-pressure steam (40-60 bar) for turbines |
| 2SO2 + O2 → 2SO3 | -198 | Medium-pressure steam, preheating |
| SO3 + H2O → H2SO4 | -130 | Hot water, plant heating |
A 1,000-ton/day H2SO4 plant can co-generate 8-12 MW of electricity — sufficient for the plant and grid export.
Emission Control:
- Residual SO2: Absorbed by NaOH/NH3 solution in scrubber → reduced to <200 mg/Nm³ (Vietnamese standards)
- Acid Mist: Mist eliminator with candle filters — efficiency >99%
- Wastewater: Neutralized with lime before discharge
5. Loc Thien — H2SO4 Supply from Contact Process Production
1. Clear Origin: H2SO4 distributed by Loc Thien comes from Contact Process plants — sulfur burning + V2O5 catalyst, achieving 98% concentration. Each batch includes a COA detailing actual H2SO4 content, Fe, As, and heavy metal impurities.
2. National Warehouse System: Binh Duong (main warehouse), Ho Chi Minh City, Dong Nai, Long An, Bac Ninh, Hai Phong — ensuring stable, uninterrupted supply.
3. Fleet of 20 Specialized Tankers: Carbon steel tanks, UN 1830 certified, direct delivery to plant storage tanks. Sealed pumps — no air contact, no moisture absorption.
4. COA/MSDS per Batch: Each order includes COA + GHS MSDS. Traceable to each shipment.
6. Frequently Asked Questions
Why Did the Contact Process Completely Replace the Chamber Process?
The Contact Process yields 98-99% H2SO4 (vs. 60-78% for Chamber), achieves >99.5% SO2→SO3 efficiency, and allows easier energy recovery and emission control. The Chamber Process uses NO/NO2 as a homogeneous catalyst — difficult to recover, causing NOx pollution. No Chamber plants have operated commercially since the 1980s.
What Impurities Poison the V2O5 Catalyst?
Arsenic (As) is the primary poison — forming V-As compounds that deactivate the catalyst surface. Fluorine (F) from phosphate raw materials destroys the silica support structure. Chlorine (Cl) forms volatile VCl4 at operating temperatures. Solution: Filter raw materials, maintain temperature >440°C to reduce As adsorption.
Why Not Absorb SO3 Directly into Water?
SO3 + H2O reacts too quickly, releasing extreme heat and creating fine H2SO4 mist (acid mist) that cannot condense — escaping through the stack. Absorbing SO3 into 98% H2SO4 → forming intermediate oleum → controlled hydrolysis — is the only way to obtain 98% concentrated H2SO4 with >99.9% absorption efficiency.
Do H2SO4 Plants Need Wastewater Treatment?
Yes, but the volume is small. Wastewater originates from scrubbers (dilute acid solution containing dissolved SO2) and equipment cleaning. Treatment: Neutralize with lime Ca(OH)2 → CaSO4 precipitate → sedimentation → clean water pH 6.5-7.5 discharged. CaSO4 sludge can be sold to cement plants.
What’s the Difference Between Domestic and Imported H2SO4?
Domestic H2SO4: Fast delivery (1-3 days), flexible MOQ, lower shipping costs. Imported H2SO4: Typically 5-10% cheaper for orders >100 tons but with 2-4 week lead time, customs procedures, and storage. Loc Thien combines both sources — ensuring competitive pricing + stable delivery.
7. Request H2SO4 Quotation
Call 0979 891 929 for quotes on 98%, 96%, 78%, 50% H2SO4 — complete COA/MSDS provided.
LOC THIEN INVESTMENT DEVELOPMENT COMPANY LTD
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Main Warehouse: Binh Duong — 24h Delivery to HCM/Binh Duong/Dong Nai/Long An Industrial Zones
Hotline: 0979 891 929
Website: hoachatlocthien.com