Mirek Spicar explains how a smart solution improves the cleaning of evaporator bundles
Magnon Green Energy generates renewable energy by incinerating excess material from forestry and agricultural biomass as a contribution to sustainable environmental protection.
The fluidised bed unit of 41MW capacity in the Spanish firm’s Huelva plant suffered for many years by plugging of the two-drum type evaporator bundle (often called “boiler bank”) by fly ash. The cleaning effect of the originally installed, steam-driven soot blowers was not sufficient to keep the flue gas temperature downstream the evaporator at a constant level. Due to the tight open space between the evaporator tubes, the ashes tend to deposit and clog the flue gas passage. In November 2019 the operator decided to install one Shock Pulse Generator (SPG) to investigate the efficiency of the cleaning effect. The location chosen was where the most concentrated fly ash is carried with the flue gas into the evaporator bundle. The location proved a success.
The operator is satisfied with the cleaning effect and the reliability of the SPG, which keeps the spaces between the evaporator tubes free of deposits even in the areas that are not accessible to the soot blowers and especially because it doesn’t cause any damage to the tubes.
Within nearly three years of its operation, approximately 20,000 shock pulses were carried out. The first larger maintenance works were carried out by Explosion Power in May 2022, and the operator carries out routine maintenance.
Larger Maintenance Works
Maintenance works at SPGs can be easily carried out while the boiler is in operation. The SPG will be disconnected from the boiler, and the opening at the discharge nozzle is sealed against the negative pressure of the boiler. The main works for the SPG are the exchange of worn parts such as gaskets, which are exposed to short time high temperatures during the shock pulses and checking of spare parts. After reassembly, the SPG is reconnected to the boiler and thoroughly checked for tightness and correct functioning of the control system. This work is carried out within one day.
The operator told Explosion Power that it would prefer to include additional SPGs in-between the evaporator bundle, where the soot blowers are presently located. Other areas where the SPGs would further increase efficiency were discussed too. However, such decisions were not yet taken, as the unit represents the oldest one at the site and it is not yet known for how long the unit will continue operation. Two newer units were installed at the plant site in 2012 and 2019, producing 137MW of electrical energy in total.
Mirek spicar is WtE and environmental engineer at Explosion Power