New sulphuric acid plant considered

Chemicals manufacturing company Chemical Initiatives, owned by the AECI group, is considering building another sulphuric acid plant, owing to increased demand for sulphuric acid worldwide and more specifically in Southern Africa, Chemical Initiatives MD Steve Sackett tells Engineering News.

The plant will be electricity- or energy-neutral and is expected to be completed between 2010 and 2011. It will also use energy generated from chemical processes to power all of the plant’s energy requirements.

Two prefeasibility studies are currently under way and the new facilities are each expected to have the capacity to produce 1 500 t of sulphuric acid a day.

The company’s existing sulphuric acid manufacturing plant, based in Durban and operating since 1974, produces steam which is sold to a wider factory complex for energy generation. It is envisioned that the new facility will function in a similar way.

Sackett says that demand for sulphuric acid is increasing worldwide but that levels of supply are not catching up, owing to developments, such as uranium-mining, that consume large quantities of sulphuric acid.
The global price of sulphur rose from $75/t to $550/t last year.

Sackett attributes this to increased demand for fertilisers from China, for agricultural activities. Biofuels are also increasing the need for fertilisers for growing crops and an increase in base metals projects, such as nickel, zinc and copper cobalt in Australia, and in Africa, are also contributing to increased sulphur demand.

Chemical Initiatives supplies predominantly sulphur-based chemicals, as well as chemicals such as ammonia and nitric acid, and speciality chemicals, such as quick lime and solvents.

Sulphur, obtained essentially from crude oil, is mainly supplied by Canada, the Middle East and Russia, owing to large oil and gas reserves.

Sulphur and sulphuric acid are the building blocks for fertiliser manu- facture. The company supplies chemicals for water treatment, paper processes, car batteries, paints, leather tanning, mining operations and pigments, besides others.

Chemical Initiatives manufactures sulphuric acid by the double-absorption contact process, which requires sulphur, air and water. Because sulphur is exothermic and burns in air, heat is generated and most sulphuric acid plants generate steam as a by- product. The process includes the use of heat exchangers, that heat or cool chemical processes, as well as catalysts and converters.

Sackett says that research and development of sulphuric acid today centres on heat recovery systems and catalysts to reduce pollution.

The company sells concentrated sulphuric acid, which is less corrosive to metal containers and tankers than weaker concentrations of 91% and lower. Sackett says that sulphuric acid can be recycled by its application in other chemical processes. The company obtains its raw materials from the Middle East, as well as from Engen, Sapref and Chevron oil refiners in South Africa.

CHEMICAL TRANSPORT
Chemical Initiatives is currently working on improving the efficiencies of its sulphuric acid transport and logistics. A tanker, also called a combo-vehicle, was manufactured by the company and began running last year. The combo-vehicle has three separate storage tanks, two of which are for sulphuric acid and one for sulphur. The sulphur tank is heated by a generator that is fed by diesel from the vehicle to maintain temperatures of over 130 ˚C.

ENVIRONMENT
Chemical Initiatives constantly monitors quantities of dilute sulphur dioxide released during the sulphuric acid manufacturing process. The company’s sulphuric acid plants also contain scrubbers, which releases cleaner gas.

Chemical Initiatives’ production centre, Umbogintwini, is configured to produce sulphur trioxide, sulphur dioxide and oleum, and has a nameplate capacity of 500 t/d of sul- phuric acid. The existing plant is a double absorption, four-pass convertor plant, and a Dynawave scrubber was retrofitted in the plant to reduce sulphur dioxide emissions.

The company’s empowerment subsidiary, Metswako Chemicals, operates in Botswana, and offers chemical services to Botswana’s mines, industries and municipalities.