The intermediate pyrolysis of de-inking sludge to produce a sustainable liquid fuel

Abstract

De-inking sludge is a waste product generated from secondary fibre paper mills who manufacture recycled paper into new paper sheets; it refers directly to the solid residues which evolve during the de-inking stage of the paper pulping process. The current practice for the disposal of this waste is either by landspreading, landfilling or incineration which is unsustainable. This work has explored the intermediate pyrolysis of pre-conditioned de-inking sludge pellets in a recently patented 20 kg/h intermediate pyrolysis reactor (The Pyroformer). The reactor is essentially two auger screws which are configured in such a way as to circulate solids within the reactor and thus facilitate in the cracking of tars. The potential application of using the volatile organic vapours and permanent gases evolved would be to generate both combined heat and power (CHP) located at paper making sites. The results show that de-inking sludge could be successfully pyrolysed and the organic vapours produced was largely composed of phenolic compounds and some fatty acid methyl esters as detected by liquid GC-MS. The calorific value of the oil after condensing was between 36-37 MJ/kg and the liquid fuel properties were also determined, permanent gases were detected by a GC-TCD and was composed of approximately 24% CO, 6% CH 4 and 70% CO 2 (v/v%). After pyrolysis the solid char residue also contained a small residual calorific value, and was largely composed of mainly calcium based inert metal oxides. The application of applying intermediate pyrolysis to de-inking sludge for both CHP production and waste reduction is in principle a feasible technology which could be applied at secondary fibre paper making sites.

Thermocatalytic Reforming of Biomass Waste Streams

“…A high ash content was detected in the sewage sludge (76.2 %) and paper sludge (82.3 %) biochars in agreement with other studies, and the resulting HHVs were lower than that of the corresponding feedstocks at 5.9 and 3.6 MJ kg −1 , respectively.…”

Steam gasification of rapeseed, wood, sewage sludge and miscanthus biochars for the production of a hydrogen-rich syngas

“…It comprises counter rotating coaxial screws to move the feed along the reactor and allows for easy control of solid residence time. Heat transfer is aided by the use of metal spheres, negating the need for costly feed preparation associated with fast pyrolysis [6].…”

Engines for Combined Heat and Power

“…Intermediate pyrolysis (slow heating rates, intermediate solid residence times) is considered to be at the early stages of research and development; however, recent studies have shown that biomass and waste derived intermediate pyrolysis oils can give a product oil with improved properties which are to a certain degree more comparable to biodiesel and diesel fuels [10][11][12][13].…”

“…Ouadi et al [10,11,35] recently demonstrated that pyrolysis oils with a low water content of 3−4% and a higher heating value (HHV) of around 36−37 MJ/kg could be produced through intermediate pyrolysis of deinking sludge obtained from both a secondary fibre tissue and newsprint mill.…”