Waste Heat Recovery for Conventional Power Plants

In modern state-of-the-art power stations and industrial manufacturing processes, energy efficiency is a vital prerequisite from a price and environmental point of view.

Many years of experience and special know-how have enabled Oschatz to develop proprietary technologies in the form of boilers and steam generators for waste heat recovery. We plan, design and construct boiler concepts for solid as well as liquid and gaseous fuels in our own production facilities.

Waste Heat Systems

Waste Heat Boiler for Liquid and Gaseous Fuels

In addition to waste heat boiler systems for solid fuels, the Oschatz portfolio includes tailor-made boiler systems for liquid and gaseous fuels as well as directly fired steam generators for the chemical and oil and gas industries.

Depending on the characteristics of the fuel to be used, steam parameters, emission constraints, available area and other site conditions, we plan custom water tube boilers.

We can design space-saving one-pass vertical “tower” types or multiple, compactly-arranged continuous-flow boilers in a combined vertical / horizontal layout with natural or forced water circulation.

Our plants offer a huge range of options, and can be operated solely with the exhaust gases from gas turbines, with gas turbine exhaust gas plus auxiliary firing, or purely with forced draught operation without the gas turbine system.

After the energy conversion system (hot water, process steam or even superheated steam) has been chosen, our technological flexibility means that downstream steam turbines can be used to generate electricity in the most economically efficient manner possible.

Continuous steam generation with integrated process-relevant parameters ensures high levels of uptime and operational reliability for the downstream processes of CCGT power plants or production processes.

Oschatz Boiler Applications

Special Features of Oschatz Waste Heat Boilers

Both hanging and supported boiler arrangements
Feed water preheating or external superheaters to achieve higher steam parameters, improving electrical efficiency
Cooling of the flue gases to less than 650 °C before they enter the convection bundles → Protection against corrosive flue gases and accretions of sticky dusts
Protection of tubes which are exposed to most critical corrosion conditions thanks to corrosion-resistant cladding
Cleaning of the heating surfaces using the most modern systems, e.g. water spraying, soot blowers, hammering and rapping devices as well as shot cleaning
Optimal integration of our boilers into the firing and combustion chamber to ensure excellent cooling and reduced slagging of the walls
Optimization of the boiler and bundle geometry to ensure optimal flue gas velocity and to reduce flue gas pressure losses
Expansion of boiler radiation area with wall heating surfaces to avoid the need for a third pass

Typical Features of the Waste Heat Boiler

Designed as an evaporation system without economizer
Designed solely as a forced circulation boiler or as using a combined natural and forced circulation principle
Depending on the process and furnace geometry, sole horizontal draw or a combination of vertical and horizontal draw boilers can be used
Vertical passes are usually designed as radiant heating surfaces
Horizontal passes contain the convection heating surfaces
Boiler walls as membrane pipe walls
Evaporator and superheater heating surfaces in hanging bulkhead or bundle construction
Hammering-system for cleaning all types of heating surfaces
Occasional use of soot blowers

Thermal Utilization Systems

Grate Firing

Oschatz’s air-cooled grate firing system is designed for almost all solid fuels, in particular low-calorific fuels with a calorific value starting at 5,000 kJ/kg. By means of specific pre-heating with regulated air supply and flue gas recirculation, the fuel is prepared for ignition and incineration. This makes the use of a wide range of fuels possible.

The combustion process is managed using a modern fire power control system. The combustion quality can be adapted to suit the combustion chamber temperature and the O2 measurement by influencing the amount of secondary and recirculation air in the chamber. This ensures a stable firing performance and good burnout.

In this way, the Oschatz combustion system with feed grate and control system makes it possible to reduce combustion-specific emissions below the legally permissible limit values.

Advantages of Air-Cooled Grates

Great range of calorific values and throughputs possible
Limited residues
Minimum emission values (in line with the IED Directive, formerly 17. BImSchV)
Capacity range: 25 – 90 MW
Excellent mixing of fuels
Perfect burn-out with lowest C content
Minimal carbon monoxide emissions in accordance with legislative requirements
Homogenous combustion air distribution below and above the grate

For high-calorific fuels such as substitute fuels or when using fuels with low ash melting points, a water-cooled grate can also be used.

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Conventional Power Plants