chemistry

Wet sulfuric acid process

Wet sulfuric acid process is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Wet sulfuric acid process rather than just read about it. In short: The wet sulfuric acid process (WSA process) is a gas desulfurization process introduced by Danish company Haldor Topsoe in 1987. The WSA process can be applied in all industries where sulfur removal presents an issue, and produces commercial quality sulfuric acid (H2SO4) and high-pressure steam during desulfurization.

Key takeaways

Wet sulfuric acid process belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Wet sulfuric acid process to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Wet sulfuric acid process from memory before moving on to harder problems.

Reference excerpt

The wet sulfuric acid process (WSA process) is a gas desulfurization process introduced by Danish company Haldor Topsoe in 1987. The WSA process can be applied in all industries where sulfur removal presents an issue, and produces commercial quality sulfuric acid (H2SO4) and high-pressure steam during desulfurization. The wet catalysis process is used for processing sulfur-containing streams, such as:

H2S gas from e.g. amine gas treating unit Off-gas from sour water stripper (SWS) gas Off-gas from Rectisol Spent acid from an alkylation unit Claus process tail gas Heavy residue or petcoke-fired utility boiler off-gas Boiler flue gases from various processes SNOX flue gas desulfurization Metallurgical process gas Production of sulfuric acid

The process

The main reactions in the WSA process Combustion: 2 H2S + 3 O2 ⇌ 2 H2O + 2 SO2 (-1036 kJ/mol) Oxidation: 2 SO2 + O2 ⇌ 2 SO3 (-198 kJ/mol) [in the presence of a vanadium (V) oxide catalyst] Hydration: SO3 + H2O ⇌ H2SO4 (g) (-101 kJ/mol) Condensation: H2SO4 (g) ⇌ H2SO4 (l) (-90 kJ/mol) The energy released by the above-mentioned reactions is used for steam production. Approximately 2–3 tons of high-pressure steam are produced per ton of acid.

Industrial applications Industries where WSA process plants are installed:

Refinery and petrochemical industry Metallurgy industry Coal-based industry (coking and gasification) Power industry Viscose industry Sulfuric acid industry

WSA for gasifiers The acid gas exiting a Rectisol-, Selexol-, amine gas treating unit or other similar units installed after the gasifier contains H2S, COS and hydrocarbons in addition to CO2. In order to prevent the emission of SO2 into the environment, the acid gas can be purified via the WSA process. The WSA process is resource-efficient, providing a high sulfur recovery while producing superheated steam with the excess heat generated, which can be recirculated and reused.

Examples of WSA process for gasification Example 1:

Feed-gas flow: 14,000 Nm3/h Composition [vol %]: 5.8% H2S, 1.2% COS, 9.7% HC and 77.4% CO2 SOx concentration [vol %]: 1.58% H2SO4 production: 106 MTPD Steam production: 53 ton/h Cooling water consumption: 8 m3/ton acid (delta T = 10 °C) Fuel consumption: 1,000 Nm3/h (LHV = 2,821 kcal/Nm3) Example 2: A sulfur plant in China will be built in connection with an ammonia plant, producing 500 kilotons/year of ammonia for fertilizer production.

Spent acid regeneration and production of sulfuric acid The WSA process can also be used for the production of sulfuric acid from sulfur burning or regeneration of the spent acid from e.g., alkylation plants. Wet catalysis processes differ from other contact sulfuric acid processes in that the feed gas contains excess moisture when it comes into contact with the catalyst. The sulfur trioxide formed by catalytic oxidation of the sulfur dioxide reacts instantly with the moisture to produce sulfuric acid in the vapor phase to an extent determined by the temperature. Liquid acid is subsequently formed by condensation of the sulfuric acid vapor and not by the absorption of the sulfur trioxide in concentrated sulfuric acid, as in contact processes based on dry gases. The concentration of the product acid depends on the H2O:SO3 ratio in the catalytically converted gases and on the condensation temperature. The combustion gases are cooled to the converter inlet temperature of about 420–440 °C. Processing these wet gases in a conventional cold-gas contact process (DCDA) plant would necessitate cooling and drying of the gas to remove all moisture. As such, the WSA process is relatively cost-efficient under most circumstances. About 80% to 85% of the world’s sulfur production is used in sulfuric acid production. 50% of the world’s sulfuric acid production is used in fertilizer production, mainly to convert phosphates to water-soluble forms, according to the Fertilizer Manual published jointly by the United Nations Industrial Development Organization (UNIDO) and the International Fertilizer Development Center.

References

Worked examples

Example 1 — a first encounter with Wet sulfuric acid process

Start with the simplest possible case. Write down what Wet sulfuric acid process claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Wet sulfuric acid process before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Wet sulfuric acid process ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Wet sulfuric acid process

In research: Wet sulfuric acid process appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Wet sulfuric acid process in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Wet sulfuric acid process is common in secondary-school and first-year university syllabi. It links to neighbouring topics Air pollution control systems, Desulfurization, Natural gas technology, so understanding it makes those chapters shorter.
In everyday life: Look for Wet sulfuric acid process outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Wet sulfuric acid process in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Wet sulfuric acid process means in your own words.
Compare your version with the excerpt and mark what you missed.
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Frequently asked questions

What is Wet sulfuric acid process in simple terms?

Why does Wet sulfuric acid process matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Wet sulfuric acid process?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Wet sulfuric acid process.