15 March 2020
In AGROinLOG project, the Spanish agro-industry “Pascual Sanz” produced herbaceous blend pellets for the energy market which were satisfactory validated by means of combustion tests in different facilities.
First in CIRCE’s combustion facilities, in a fixed bed reactor and an industrial boiler based on a grill burner. Good CO emissions were obtained in all blends tested, being lower than 500 mg/ N m3 d. b., as per the standard for this kind of installation (between 150-500 kW).
When comparing these biofuels to the reference fuel (100 % forestry wood pellet), the main drawback was related to sintering and deposition problems associated to the ash. As a result, it was concluded that in order to avoid sintering problems, the new fuels should have a low ash content, low Si content and high Ca+Mg content; to avoid problems of deposition, the fuels should have a low percentage of ash, few fines and a low content of S and Cl.
The blends were tested and compared. In terms of combustion performance, the WSP family (wheat straw pellets) presented better results than the MSP family (maize stalk pellets). Finally, the blend selected was the one with 60 % wheat straw and 40 % forestry wood, since it achieved a good behaviour compared to the reference fuel (100 % forestry pellet), in terms of emissions, yield, sintering and deposition phenomena, satisfying also the ISO standard. In economic terms, the selling price, was also quite competitive compared to industrial woody pellets.
Moreover, the new products were validated with several industrial end-users including two agro-industries, one domestic user and one boiler manufacturer.
All the validators qualified the tests performed as “satisfactory” or “very satisfactory”, as they did not have any problems with the operation of the boiler. The only inconvenient was the quantity of ashes generated, but the automatic cleaning was able to remove the ashes, so no problems were found during operation. All the validators indicated that they would be interested in the new products if the purchasing price were more competitive than their current biofuel in terms of €/kWh.