BC Insight - Nitrogen+Syngas, Sulphur, Fertilizer International
Login
BCInsight Ltd
China Works
Black Prince Road
London, SE1 7SJ
United Kingdom
Tel: +44 (0)20 7793 2567
Fax: +44 (0)20 7793 2577

Publication > Issue > Articles

Asia Nitrogen 1996 Conference Report

Summary

The Asia Nitrogen 1996 conference was held in Singapore from the 12th to 14th of February. This was the second of British Sulphur's international conferences focusing on the nitrogen fertilizer market in Asia, following the success of the previous conference in Bali, Indonesia in 1994.

Abstract

The nitrogen fertilizer sector in Asia is still ra'pidly expanding, particulalry in the giant markets of India and China. It was therefore no surprise that some 180 delegates should make their way to Singapore, one of the region's fastest- growing trade hubs, for the 1996 Asia Nitrogen conference. In his welcome address, John French of British Sulphur stressed the international character of the meeting, with delegates present from 30 countries. He was also, he said, pleased by the level of participation by plant operators, who had valuable experience of the practicalities of fertilizer production to share with the delegates.

Add to basket


Electric motors: a cost effective driver

Summary

In this final part of the series about designing a methanol plant for low investment cost, A. M. Dark * and R. N. Grundy ** consider electric motor drivers for methanol plant machinery. They show that the generation of electrical power, its distribution and then reconversion into shaft power for driving compressors and other machinery is extremely efficient and cost effective.

Abstract

The two previous articles in this series1,2 considered the cost of steam turbines and then gas turbines for driving the rotating machinery found in a conventional 2,000 tid methanol plant. In this final article, the investment costs and operating characteristics of electric motors are evaluated for driving some of the centrifugal compressors found in a 2,000 tid methanol plant.

Add to basket


Increasing performance of NOx abatement

Summary

Stricter controls on the emissions of nztrogen oxides from the tail gas of nitric acid plants has increased the importance of efficient NOx abatement systems. This in turn has led to the development of new improved catalysts for selective catalytic reduction of NO. Those x of BASF and CRI Catalysts are described below.

Abstract

Depending on the plant design and mode of operation, the tail gas of nitric acid plants contains variable amounts of nitrogen oxides (NO and N02). The total nitrogen oxide (NO) can be as high as 2,500 ppm or more and the molar ratio of N02 to total NOx can exceed 50%. Selective catalytic reduction using ammonia as the reducing agent can provide a cost effective and efficient means to reduce NOx levels to more acceptable levels (e.g. 200 ppm). The main reactions governing the selective catalytic reduction (SCR) of NO and N02 in the tail gas of nitric acid plants are shown below:

  • NO + NO2 + 2NH3 -> 2N2 + 3H2O
  • 4NO + O2 + 4NH3 -> 4N2 + 6H2O
  • 6NO2 + 8NH3 -> 7N2 + 12H2O
  • 2NO2 + 4NH3 + O2 -> 7N2 + 6H2O

Add to basket


Nitric acid catalyst customization

Summary

Improved catalyst technologies have contributed to the longer and more efficient campaigns now achieved in nitric acid plants. EngelhardCLAL is forming partnerships with customers to permit them to participate in the development of their own catalyst formulations.

Abstract

Engelhard-ClAL is one of the world's largest suppliers of platinum alloy gauze catalysts for ammonia oxidation and a technology leader in high-efficiency platinum recovery systems.

In Europe, where medium-pressure nitric acid plants predominate, the most commonly used platinum alloys contain 5% or 10% rhodium, which acts as a strengthener. In the USA, where high-pressure plants are typical, a platinum alloy containing 5% rhodium and 5% palladium is preferred. Engelhard-CLAL uses a variety of production techniques, including knitting and weaving, to produce platinum alloy gauzes which are then cut to size according to customer requirements.

All medium-pressure plants utilize a precious metal catchment system to recover volatilized platinum loss from the catalyst. Engelhard-ClAL's MTL palladium alloy gauze systems achieve economical platinum recovery rates of 80-85% (35% of the rhodium loss is also captured). A corrugated version, known as LPMTL, which has one third of the pressure drop of normal MTL is also available for high-pressure nitric acid plants. These gauzes typically recover 65-70% of platinum loss.

At the end of the catalyst cycle, the catalyst and MTL pack are returned to Engelhard-CLAL for refining and reconditioning. The alloys are melted down, cast into ingots, rolled and drawn into wire with a diameter of 60 or 76 mu m.

Add to basket


Sandvik's special stainless steels

Summary

Special stainless steels have been used in the fertilizer industry with exceptionally good results for many years. In nitric acid service, where materials like 304L may corrode, an alloy with improved resistance such as Sandvik 2REJ0 offers superior performance.

Abstract

In nitric acid plants, standard austenitic steels of type 304L are extensively used in all parts of the plant where acid is present. Type 321 is also sometimes used, even if 304L is regarded as a better grade for service in nitric acid. For some parts a more corrosion-resistant material is needed. A higher chromium content will improve corrosion resistance. A very low carbon content in combination with a low amount of impurities will give the best possible corrosion resistance. Sandvik's 2REI0 is a material which fits these criteria and has been optimized for use in nitric acid. The chemical composition of Sandvik 2REI0 is shown in Table 1. In Figure 1, 2REI0 is compared with 3R12, a version of 304L with low impurity level. The solid curves in Figure 1 correspond to a corrosion rate of 0.1 mm/year (4 mils/year).

In nitric acid plants, the most severe corrosion conditions are normally found in tail gas preheaters, boiler feed water heaters and cooler/ condensers, i.e. mainly where the evaporation of nitric acid droplets or condensates occur. If evaporation occurs, the acid concentration will probably increase to the azeotropic concentration, which in high pressure processes means up to 69% nitric acid, which is very aggressive (see Fig. 1).

Corrosion problems can vary from plant to plant because of local service conditions. When they become frequent there is a need to select better materials. The initial cost for a better material might be higher, but it is always more expensive to replace later with a corrosion-resistant material.

Add to basket


Improved ammonia conversion

Summary

Grande Paroisse, an affiliate of Elf Atochem, is the largest producer of nitric acid in France, and one of the largest in Europe. Grande Paroisse technology is licensed worldwide in plants ranging"from 35 tid to 2,000 tid. Here the company's new developments in medium-pressure plants are reviewed.

Abstract

Historically, Grande Paroisse has been a pioneer in the area of dual-pressure nitric acid plants, where ammonia oxidation and nitrogen oxide (NOx) absorption are carried out at two different pressures. However, the investment involved in such a plant can often only be justified for large production volumes. Depending upon energy costs, dual pressure plants require a nitric acid capacity of around 1,000 tid or greater to produce a reasonable return on investment. Where plant capacity is in the region of 500 tid, a monopressure plant must be used.

Grande Paroisse's most recent developments in the area of improving nitric acid manufacture have concentrated upon such mid-sized plants, and cover three main areas; improving the rate of ammonia conversion, integration of nitric acid and ammonium nitrate (AN) production units to maximise energy recovery, and reduction of NOx emissions to air and water.

Add to basket