A STIEFEL project KVA Linthgebiet Niederurnen case study

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Courtesy of Jakob Stiefel GmbH

The waste incineration plant KVA Linthgebiet is situated in Switzerland. The plant disposes of a total of 120’000 tons of waste each year from 240‘000 inhabitants in the surrounding area. Due to the thermal recovery, it produces annually 84 GWhour of electrical energy and therefore saves 250’000 litres of fuel oil by providing energy to a district heating system.

Background and history of the KVA Linthgebiet
The local government of the Glarus region constructed the incinerator in Niederurnen between 1971 and 1973. In 1974, the authorities founded an Association for the waste disposal of the whole area.

From 1982 until 1984, the Association enlarged the plant capacity by a second combustion line. A Martin combustion system considerably increased the waste capacity. This line was equipped to recover energy from the waste material.

From 1996 to 2001, the Incinerator Plant was completely modernised with the latest technology. The system engineering and the computer control systems are still some of the most technically advanced in the world today.

Since 1982, Jakob Stiefel Technik AG has been the Engineering Partner for the KVA Linthgebiet Plant. All assembly and commissioning of equipment in various parts of the plant was performed by STIEFEL Technik. Due to the plant being continually optimised and upgraded with STIEFEL technology, it remains at the forefront and leading edge of incineration and flue gas treatment. Commencing in 1988, Line 1 of the Combustion System was completely changed and renewed with the STIEFEL grate. The success of this led to Line 2 being retrofitted 3 years later. In 2003 and in 2011, further modernisation of the plant took place which has resulted in Line 1 being equipped with an external grate drive system and Line 2 now using a new modular grate step with a replaceable surface plate.

The Reconstruction of Line 1
Toward the end of the nineties, the KVA Linthgebiet became the pioneer for the “Totally Water Cooled STIEFEL Combustion System”. The water cooling was extended to the grate, the feeder as well as all other parts in contact with heat which resulted in the elimination of the thermal wear factor. Each grate zone was equipped with its own independently controlled primary air fan. The combustion control system was integrated and optimised with the system for the entire plant allowing the best possible operational practices.

In 2011, the forward motion grate was modernised with the next generation drive system. This newly developed system features an external drive which provides safe, quick and easy access for routine maintenance.

Retrofit of Line 2
The existing air cooled MARTIN combustion system was modified in 2001 to become water cooled. In the first phase, the feeder together with grate zones 1 and 2 were replaced with a water cooled system along with the combustion control system. The retrofit of zones 3 to 5 was made in 2004. Since 2008, grate steps of the latest generation have been used. These grate steps are unique as they allow for the replacement of just the worn surface plate. This modular replacement can be undertaken at any time with only the worn out surfaces having to be replaced.

Control System
The STIEFEL combustion control system optimises all the features and possibilities of the STIEFEL concept. The system makes full use of the advantages of a Water Cooled grate and other components which include an individual grate step drive and an individual control of primary air fans in all zones. Having such individuality, which is unique within the industry, enables stable and complete combustion resulting in lower flue gas emissions.

Advantages

  • The water cooling avoids any thermal wear resulting in a much longer life span of all components and a higher reliability of the combustion system.
  • The air distribution is completely independent of the grate surface cooling. This enables an optimal positioning in the main combustion zone and results in an outstanding burnout.
  • The combustion air is injected efficiently. Therefore, the flue gas volume is lower and the emissions are minimal.
  • Due to individually controlled primary air fans, reliability is increased and the combustion process is precisely controlled.
  • A uniform grate surface which is not subject to thermal wear enables a homogeneous primary air injection across the whole zone. Therefore caking is significantly reduced and the efficiency and life span of the boiler is increased.
  • Using larger grate elements reduce the number of mechanical connections to adjacent elements which increases the reliability and reduces the maintenance effort.
  • The individual drive of each grate step simplifies the mechanical operation and increases the reliability.
  • The continuous moving of the grate steps avoids blockage.
  • The external grate drive improves the accessibility and simplifies the maintenance.
  • Specific wearing parts are easily replaced and reduce the maintenance times.

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