Please read about the Biomass-fired CHP plant Lisbjerg and how DSE helped with their challenges with straw bales being delivered in different sizes and densities.
Background
Biomass-fired CHP plant in Lisbjerg is the latest of its kind in Denmark. It started production in 2017 and uses 170.000 tons of straw annually.
The straw bales Biomassefyret Kraftværk is receiving is a mix of classic Heston bales in format 127 x 120 x 245 cm and 3/4 bales in format 90 x 120 x 245 cm, also called MIDI-bales.
Developing High-density balers in the midi size format during the last 7 – 8 years has been a more efficient and environmentally friendly way of collecting straw. The bales are getting heavier but smaller, making it possible to get more straw on truckloads, thus gaining cheaper, more efficient, and environmentally friendly transport.
Case description
However, the mix of size and density has proven to be a challenge to moisture determination by microwaves used in power plants worldwide. Until May 2019, all crane moisture meter systems were set up to use one standard density value for all bales.
When a system uses one standard density for all bale types and receives a mix of different types and densities, the measurements will be errors depending on the deviation from the standard density settings. This can be several % of the readings.
Adjusting the density settings for, e.g., High-Density Midi bales also affects the moisture measurement range; in some cases, the maximum measurement range comes below the rejection criteria.
To ensure a fair settlement, the Biomass-fired CHP plant Lisbjerg asked DSE to assist them in developing a solution. In May 2019, the solution was installed in the form of a software update and a sensor update.
System description
The hardware update of the sensors gave an increase in measurement area of 3% in the low-density area (dry density 120kg/m3). A 2.3% increase in density area of 160kg/m3(dry density), measuring up to 26.3% moisture to help ensure moisture can be read up to the rejection criteria.
The DSE moisture control software was extended with an advanced algorithm to calculate the correct dry weight density based on the information from the crane about the bale type, length, and wet weight of the bales in the yoke, combined with the microwave signal.
The calculated dry weight of the bales in the yoke is used to calculate the moisture value for the bales. Thus, the moisture values no longer depend on the standard density settings but are dynamically customized to all kinds of bales - ensuring correct moisture measurements.
All data is recorded in the database for trackability and returned to the crane as documentation to the power plant and its suppliers.