Release of N-containing compounds during pyrolysis of milk/dairy processing sludge – Experimental results and comparison of measurement techniques

Marzena Kwapinska, Peter Sommersacher, Norbert Kienzl, Stefan Retschitzegger, Jacqueline Lagler, Alen Horvat, James J. Leahy

Research output: Contribution to journalArticlepeer-review

Abstract

A dried dairy processing sludge (sludge from wastewater treatment of an effluent from a milk processing plant) was pyrolysed in a single-particle reactor at different temperatures from 400 °C to 900 °C. NH3 and HCN were measured online and offline by means of FTIR as well as by cumulative sampling in impinger bottles (in 0.05 M H2SO4 and 1 M NaOH, respectively) and analysed by photometric method. NO and NO2 were measured online using a nitric oxide analyser while N2O was measured by FTIR. Nitrogen (N) in the sludge and in the remaining char, char-N, was determined. Moreover, tar content in pyrolysis gas was measured and tar-N was determined. The results with respect to N mass balance closure are discussed. The different measurements techniques are compared. For pyrolysis at 520 ℃ and 700 ℃ nitrogen in the gas phase was mainly contained as N2 (36 % and 40 % respectively), followed by NH3 (15 % and 18 %), tar-N (10 % and 9 %), HCN (1 % and 3 %), NO (1 %) and NO2 (0.2 %). The dairy processing sludge has very specific properties with organic-N present predominantly as proteins and a high content of inherent Ca. These characteristics affected the distribution of N. The amount of char-N was higher while the amount of tar-N lower than for sewage sludge from literature, at comparable pyrolysis temperature.

Original languageEnglish
Article number106391
JournalJournal of Analytical and Applied Pyrolysis
Volume178
DOIs
Publication statusPublished - Mar 2024

Keywords

  • Ammonia
  • Char
  • FTIR
  • Hydrogen cyanide
  • N mass balance
  • Photometric

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