Pilot Scale Pyrolysis of Activated Sludge Waste from Milk Processing Factory

The majority of the sludge from the treatment of wastewater in milk processing plants is land spread. The drawbacks of land spreading include local oversupply due to high transport costs, which results in sludge being spread on lands in the vicinity of the dairy factories. Local oversupply can lead to accumulation of certain substances in soil through annual application over many years. Therefore, in the long term, there is a need for alternative methods to recover energy and nutrients from increasing volumes of sludge generated from dairy processing. Pyrolysis ofers a potential alternative to land spreading, which can reduce health and environmental risks, while providing an avenue for the recovery of energy and nutrients. Pyrolysis allows energy recovery in the form of a high calorifc value pyrolysis gas and a char which may be used as a soil amendment. In this study pyrolysis of dried dairy sludge was carried out at pilot scale. The results indicate that a dried biological sludge can be successfully pyrolysed and when mixed with wood the resulting char meets European Biochar Certifcate criteria regarding carbon content. Most of the initial energy content of the feedstock was retained in the pyrolysis gas prior to cleaning, 53%, compared to 34.5% in the char and 1.5% in the tar. For the pyrolysis gas after cleaning (mainly cracking in presence of air) the initial energy content of the feedstock retained in the gas was only slightly higher than that retained in the char, 39.2% versus 34.5%, while the tar accounted for 0.8% of the initial energy content

Energy recovery through co-pyrolysis of wastewater sludge and forest residues – The transition from laboratory to pilot scale

peer-reviewedAnaerobically digested sewage sludge mixed with forest residues was pyrolysed at 800 ◦C, at laboratory and pilot scale. The study quantified differences in char and gas yields for tests carried out in a simple fixed bed laboratory reactor and rotating retort pyrolyser at pilot scale, when the residence time of feedstock was 10 min in both cases. The yield of char from pilot scale was 4 % lower than from laboratory scale while the yield of gas was 15.7 % higher. During the pilot scale pyrolysis of anaerobically digested sewage sludge blended with forest residues the gas quality for energy recovery applications was assessed and the fate of impurities (tar, NH3 and H2S) was investigated. The raw pyrolysis gas contained 14.6 g/Nm3 of tar, 36.9 g/Nm3 of NH3 and 793 ppm of H2S. Sixteen N-containing tar species were identified of which pyridine, propenenitrile, 2 methyl-, benzonitrile, and indole are found to be the most abundant. The yield of N-containing tar compounds accounted for approx. 12 % of total tar content. Conditioned pyrolysis gas contained 7.1 g/Nm3 of tar, 0.036 g/Nm3 of NH3 and 119 ppm of H2S. Benzene was by far the most abundant tar compound followed by toluene and styrene. The specifications of the used internal combustion engine were exceeded due to the sum of tar compounds such as fluorantrene and pyrene with 4+ aromatic rings (at 0.0015 g/Nm3nd NH3 content The effectiveness and sustainability of energy recovery in wastewater treatment can be improved using forest industry by-products

Parametric study of lab-scale and pilot-scale biomass torrefaction for the production of woodstove briquettes

Conversion of torrefied olive residues to high-density briquettes is a potential solution to solid waste problems as well as to the lack of locally available fuel wood in Ireland. In this study, olive stones were torrefied at various temperatures and holding times in a fixed-bed reactor. Effects of process parameters such as heat treatment temperature from 200 to 300℃, residence time from 30 to 60 min, and particle size from 0.18 to 3 mm on the yield and composition of products were investigated and the results were compared with the mass balances from industrial-scale torrefaction plant at the Arigna Fuels (Carrick-on-Shannon, Ireland). The olive stones of larger particle size produced more liquid and gaseous products than smaller particles in a fixed bed reactor, whereas particle size had significantly less influence on the product yields than residence time and heat treatment temperature. The analysis of liquid products of the industrial-scale plant showed a greater content of heavy molecular products compared to the lab-scale pyrolysis using high-performance liquid chromatography and size exclusion chromatography techniques. New value-added products were developed from the tar compounds produced at the industrial-scale torrefaction plant. In addition, the lab-scale experiments showed that the ash content of torrefied biomass significantly increased with the increased feedstock particle size. The torrefied olive stones briquettes using different binders were tested in a conventional woodstove. Torrefaction of olive stones has been found to reduce the emissions by approximately 60% compared to the non-treated feedstock. This demonstrates that torrefaction has good potential as a cost-effective and sustainable process for the production of woodstove briquettes from low-quality feedstocks

Poultry Litter Gasification in a Fluidized Bed Reactor: Effects of Gasifying Agent and Limestone Addition

Air and air-steam gasification of poultry litter was experimentally studied in a laboratory scale bubbling fluidized bed gasifier at atmospheric pressure using silica sand as the bed material. The effects of equivalence ratio (ER), gasifier temperature, steam-to-biomass ratio (SBR), and addition of limestone blended with the poultry litter, on product gas species yields and process efficiency, are discussed. The optimum conditions (maximum carbon conversion, gas yield, heating value, and cold gas efficiency) were achieved at an ER 0.25 and 800 °C, using air (SBR = 0) and poultry litter blended with 8% w/w limestone, yielding a product gas with a lower heating value (LHV) of 4.52 MJ/Nm 3 and an average product gas composition (dry basis) of H 2 : 10.78%, CO: 9.38%, CH 4 : 2.61, and CO 2 : 13.13. Under these optimum processing conditions, the cold gas efficiency, carbon conversion efficiency, and hydrogen conversion efficiency were 89, 73, and 43% respectively. The reported NH 3 measurement at an ER of 0.28 and 750 °C is 2.7% (equivalent to 19,300 mg/Nm 3 ) with 14.7 mg/Nm 3 of HCl observed as the dry product gas. High temperature and steam injection favor production of CO and H 2 , while their effect on CH 4 was almost negligible. It is demonstrated that poultry litter can be gasified by blending with limestone, making it possible to overcome the fluidization problems caused by the mineral composition of poultry litter ash (high K and P content), yielding a gas with a similar heating value compared to gasifying without limestone addition, but with a significantly lower tar content

Pyrolysis of wastewater sludge and composted organic fines from municipal solid waste: laboratory reactor characterisation and product distribution

peer-reviewedSludge from municipal wastewater treatment plants and organic fines from mechanical sorting of municipal solid waste (MSW) are two common widespread waste streams that are becoming increasingly difficult to utilise. Changing perceptions of risk in food production has limited the appeal of sludge use on agricultural land, and outlets via landfilling are diminishing rapidly. These factors have led to interest in thermal conversion technologies whose aim is to recover energy and nutrients from waste while reducing health and environmental risks associated with material re-use. Pyrolysis yields three output products: solid char, liquid oils and gas. Their relative distribution depends on process parameters which can be somewhat optimised depending on the end use of product. The potential of pyrolysis for the conversion of wastewater sludge (SS) and organic fines of MSW(OF) to a combustion gas and a carbon-rich char has been investigated. Pyrolysis of SS and OF was done using a laboratory fixed-bed reactor. Herein, the physical characterisation of the reactor is described, and results on pyrolysis yields are presented. Feedstock and chars have been characterised using standard laboratory methods, and the composition of pyrolysis gases was analysed using micro gas chromatography. Product distribution (char/liquid/gas) from the pyrolysis of sewage sludge and compostedMSWfines at 700°C for 10 min were 45/26/29 and 53/14/33%, respectively. The combustible fractions of pyrolysis gases range from 36 to 54% for SS feedstock and 62 to 72% from OF. The corresponding lower heating value range of sampled gases were 11.8–19.1 and 18.2–21.0 MJ m-3, respectively

Cynara cardunculus L. gasification in a bubbling fluidized bed: the effect of magnesite and olivine on product gas, tar and gasification performance

peer-reviewedGasification of Cynara cardunculus L. was performed in a bubbling fluidized bed (BFB) using air as gasifying agent and, magnesite and olivine as different bed materials. Temperature was varied during the experiments (700-800 degrees C) with fixed biomass feeding and air flow rate. The effect of using the magnesite and olivine on gas and tar composition, carbon and biomass conversion, and cold gas efficiency was investigated. The product gas showed high hydrogen content (13-16% v/v) for both magnesite and olivine in the studied temperature range. Higher heating value and gas yield were improved with increasing the temperature from 700 to 800 degrees C. Biomass and carbon conversion were greater than 75%, obtaining values higher than 90% for both 700 and 800 degrees C in magnesite and for 800 degrees C in olivine. Small differences in total tar were observed between materials, although tar composition was very different. BTEX were higher for olivine and similar PAHs was obtained for both magnesite and olivine. A higher catalytic activity at 800 degrees C was observed for magnesite. Gasification performance was better with magnesite at 700 degrees C while olivine showed better properties at 800 degrees C. (C) 2016 Elsevier Ltd. All rights reserved.ACCEPTEDpeer-reviewe

Distribution of ash forming elements during pyrolysis of municipal wastewater sludge and sludge from milk processing factories

In the long term, there is a need for alternative methods to recover energy and nutrients from increasing volumes of sludge generated from wastewater treatment plants. Pyrolysis can be an interesting option, which can reduce health and environmental risks, while providing an avenue for the recovery of energy and nutrients. One of the main concerns related to thermal conversion technologies is the release and fate of heavy metals and contaminants existing in the feedstock. Therefore, a detailed understanding of the transformation pathways of problematic compounds is necessary to assess the suitability of pyrolysis. In this study pyrolysis of dried dairy sludge and sewage sludge was carried out using a simple laboratory fixed bed reactor. Characterisation of the feedstock and pyrolysis products was performed through proximate and ultimate analysis and the content of major and minor ash forming elements were determined. The mass balance information obtained from the experimental tests was used for an indicative distribution of Al, Ca, Fe, K, Mg, Na, P, S, Si, As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sb, Se, Ti, V and Zn between solid and liquid pyrolysis products. Results indicate that distribution of major elements between pyrolysis products was similar for dairy sludge and sewage sludge, with Ca, Mg, Fe, P, Si, Al, Na and K predominantly retained in pyrolysis chars (pyrogenic solids). However, substantial quantities of Al, K, Na and Si were detected in pyrolysis oil and in the aqueous fraction. The heavy metals and trace elements were mainly retained in the pyrolysis chars (pyrogenic solids) with the exception of As, Ba, Cd, Se, Sb and Pb, which were also detected in the liquid products

Hydrothermal carbonization of milk/dairy processing sludge: Fate of plant nutrients

Dairy processing sludge (DPS) is a byproduct generated in wastewater treatment plants located in dairy (milk) processing companies (waste activated sludge). DPS presents challenges in terms of its management (as biosolids) due to its high moisture content, prolonged storage required, uncontrolled nutrient loss and accumulation of certain substances in soil in the proximity of dairy companies. This study investigates the potential of hydrothermal carbonization (HTC) for recovery of nutrients in the form of solid hydrochar (biochar) produced from DPS originating from four different dairy processing companies. The HTC tests were carried out at 160 ◦C, 180 ◦C, 200 ◦C and 220 ◦C, and a residence time of 1h. The elemental properties of hydrochars (biochars), the content of primary and secondary nutrients, as well as contaminants were examined. The transformation of phosphorus in DPS during HTC was investigated. The fraction of plant available phosphorus was determined. The properties of hydrochar (biochar) were compared against the European Union Fertilizing Products Regulation. The findings of this study demonstrate that the content of nutrient in hydrochars (biochars) meet the requirements for organo-mineral fertilizer with nitrogen and phosphorus as the declared nutrients (13.9–26.7%). Further research on plant growth and field tests are needed to fully assess the agronomic potential of HTC hydrochar (biochar).</p

Preliminary Assessment of Pyrolysis Biochar Derived from Milk/ Dairy Processing Sludge as a Potential Component of Fertilizers

Disposal of waste-activated sludge [dairy processing sludge, (DPS)] from wastewater treatment plants located in milk processing companies is an increasing concern. DPS is usually applied to farmlands in the vicinity of the dairy companies. This practice is becoming unsustainable due to uncontrolled nutrient loss and potential soil contamination. We propose to recover nutrients in the form of biochar. This paper examines the properties of biochars obtained from slow pyrolysis of DPS. DPS samples were pyrolyzed at laboratory and pilot scale at 600 and 700 °C. The elemental properties of biochars, the content of primary and secondary nutrients, as well as contaminants were examined and compared against the European Union Fertilizing Products Regulation. The biochars meet the specified limits for hydrogen-to-organic carbon ratio, chloride, and polycyclic aromatic hydrocarbons intended for gasification and pyrolysis component category materials. In six out of eight biochars, the content of phosphorus (P) as a single declared nutrient and the level of contaminants meet those required for an organo-mineral fertilizer. Only two biochars meet the required concentrations of nitrogen, phosphorus, and potassium. A minimum solid content of 30% in DPS is required to make the process of biochar production energetically sustainable </p