Chemical

In these plants,  ammonia is catalytically burned with air or oxygen via process gas coolers.

The resulting gas (NO gas) is cooled (from 950 °C to 500 ° -C 180 °)C and the heat energy is used to generate steam.

The process gas coolers developed by Oschatz consist of the following components:

• The burner head with ignition system and internals for optimum distribution of the in-flowing ammonia gas
• A gauze-clamping device to support and retain the catalyst gauze
• Spiral heating surfaces to cool the gases to the required temperature. The heating surfaces consist of pre-evaporator, superheater, main evaporator and – if required – economizers
• The cylindrical gas pressure vessel in which the heating surface is mounted. Here, a gas-tight welded tube wall protects the vessel from high gas temperatures

At Oschatz, we are very well acquainted with all types of gauze-clamping systems and can build process gas coolers up to a gas volume of 230,000 Nm³/h and a gas pressure of 12 bar. One of the largest process gas coolers in the world with a vessel diameter of six meters was built and put into operation for a German customer.

Even though the greatest care is taken at the design and production stages, it is impossible to avoid the possibility, however unlikely, that leaks occur in the spiral heating surfaces after years of service. Using the leak testing system developed by Oschatz, the defective tube can be identified easily and reliably so that the necessary repairs can then be carried out.

Using this technology, elemental sulfur is oxidized to SO₂/SO₃ and then converted in a catalytic, exothermic process to sulfuric acid. More than 40 waste heat boilers are currently being used by satisfied customers across the globe.

In the cooling sections that are required for this process, several heat exchangers – precisely tailored to the process requirements of the contact furnace – cool the gases down to the required temperatures.

One of the biggest challenges in this process is maintaining a constant gas exit temperature from the waste heat boiler regardless of the load. Oschatz reaches these temperatures by implementing internal or external gas- or steam-side bypasses which are equipped with the necessary control mechanisms.

• Our design allows for both vertical and horizontal thermal expansion, avoiding the use of compensators as far as possible
• Boiler walls are welded so that they are gas-tight
• Simple heating surfaces that are easy to maintain
• Heating surfaces can be exchanged in segments, thus reducing downtime
• All systems are designed to operate with minimal maintenance

Typical Applications

• Steam quantity:                   5–257 t/h
• Steam pressure:                 40–90 bar
• Steam temperature:          300–500 °C
• Process gas pressure:        1–1.4 bar a
• Process gas           temperature: 1000–1600 °C

These systems ensure the safe disposal of residual materials with minimal emissions and provide a reliable source of steam and energy.

Since the 1990s, Oschatz has been successfully designing, manufacturing, delivering and commissioning turnkey complex incineration systems with efficient waste heat recovery functions, e.g. for acrylic acid, butanediol and THF plants.

Major Design Features Are:

• High throughput, long operating times and zero downtime
• Exhaust gas quantities up to 400,000 Nm³/h; liquid residues up to 20 t/h and steam generation up to 200 t/h
• Bespoke burner systems for the simultaneous application of a variety of liquid and gaseous feedstocks. Modern incineration technology, designed to be efficient in their fuel requirements. Low NOx burner systems, flue gas recirculation and intelligent furnace management are the basis for a substantial reduction in emissions
• Further NOx reduction is achieved by means of secondary measures, such as SNCR or SCR systems and use of adiabatic and brick-lined combustion chambers in the incineration of difficult and low-calorific residues
• Cooled combustion chambers through the integration of the boiler system for high calorific residues
• Waste heat boiler system consisting of superheater, evaporator, economizer, heating surface cleaning system and air/waste gas pre-heater
• Process control system to ensure the highest levels of plant safety and uptime

• natural gas,
• fuel oil,
• hydrogen,
• Fuels containing carbon monoxide (e.g., blast furnace gas, converter gas and coke oven gas)

to generate steam and electrical power.

Oschatz has developed a tailor-made heating system for this process, taking into account the specific characteristics of exhaust gases, including gas composition, dust content, as well as fluctuating load and calorific values.

In order to ensure uniform and safe steam generation, auxiliary fuels, e.g. natural gas, can be co-fired.

We can fulfill the most demanding requirements by ensuring low temperatures of the flue gas emerging from the boiler, which ensures a high degree of efficiency, as well as rapid reactions and moderate compensation of erratic loads.

Our customers benefit from software-supported flow simulation as well as our high quality requirements in the selection of materials, the design and in the professional production, which means that they enjoy maximum operator flexibility and maximum uptimes.