Kumar Patchigolla

Comparison of Particle Size Distributions Measured Using Different Techniques

ABSTRACT In this article, particle size distributions (PSDs) measured by different techniques, including image analysis (IA), laser diffraction (LD), ultrasonic attenuation spectroscopy (UAS), and focused-beam reflectance measurement (FBRM), are compared for spherical glass beads and nonspherical silica flakes. It is shown that particle shape strongly affects the results obtained by different techniques. For spheres, the PSDs obtained by IA, LD, and UAS agree well. There is no consistent result among different particle measurement techniques for nonspherical particles. The conversion between PSDs obtained by IA, LD, and UAS has been based on particle shape factors. Caution must be exercised when a measured chord length distribution (CLD) is used to indicate the PSD during a process because the CLD result obtained by FBRM is complex, depending not only on the PSD, but also on particle optical properties and shape.

Energy recovery from human faeces via gasification: A thermodynamic equilibrium modelling approach.

Highlights • On dry basis, typical human faeces contain 83 wt.% organic fraction and 17 wt.% ash.• The LHV of dry human faeces ranged from 19 to 22 MJ/kg, values similar to wood biomass.• Syngas from dry human faeces had LHV of 15–17 MJ/kg at equivalence ratio of ∼0.31.• Energy is best recovered from moist human faeces at equivalence ratio above 0.6.• Recoverable exergy potential from moist human faeces can be up to 15 MJ/kg.

Effect of SO2 and steam on CO2 capture performance of biomass-templated calcium aluminate pellets

Four types of synthetic sorbents were developed for high-temperature post-combustion calcium looping CO2 capture using Longcal limestone. Pellets were prepared with: lime and cement (LC); lime and flour (LF); lime, cement and flour (LCF); and lime, cement and flour doped with seawater (LCFSW). Flour was used as a templating material. All samples underwent 20 cycles in a TGA under two different calcination conditions. Moreover, the prepared sorbents were tested for 10 carbonation/calcination cycles in a 68 mm-internal-diameter bubbling fluidized bed (BFB) in three environments: with no sulphur and no steam; in the presence of sulphur; and with steam. When compared to limestone, all the synthetic sorbents exhibited enhanced CO2 capture performance in the BFB experiments, with the exception of the sample doped with seawater. In the BFB tests, the addition of cement binder during the pelletisation process resulted in the increase of CO2 capture capacity from 0.08 g CO2 per g sorbent (LF) to 0.15 g CO2 per g sorbent (LCF) by the 10th cycle. The CO2 uptake in the presence of SO2 dramatically declined by the 10th cycle; for example, from 0.22 g CO2 per g sorbent to 0.05 g CO2 per g sorbent in the case of the untemplated material (LC). However, as expected all samples showed improved performance in the presence of steam, and the decay of reactivity during the cycles was less pronounced. Nevertheless, in the BFB environment, the templated pellets showed poorer CO2 capture performance. This is presumably because of material loss due to attrition under the FB conditions. By contrast, the templated materials performed better than untemplated materials under TGA conditions. This indicates that the reduction of attrition is critical when employing templated materials in realistic systems with FB reactors.

An experimental investigation of the combustion performance of human faeces

Highlights • Dry human faeces have a Higher Heating Value (HHV) of 24 MJ/kg.• Faeces combustion was investigated using a bench-scale downdraft combustor test rig.• Combustion temperature of 431–558 °C was achieved at air flow rate of 10–18 L/min.• Fuel burn rate of 1.5–2.3 g/min was achieved at air flow rate of 10–18 L/min.• Combustion temperature of up to 600 ± 10 °C can handle 60 wt.% moisture in faeces.

Conceptual energy and water recovery system for self-sustained nano membrane toilet

Highlights • Energy and water recovery system from human excreta is modelled in Aspen Plus.• The Nano Membrane Toilet is proven to be a self-sustained system.• Up to 87% of total amount of water fed to the system can be recovered.• Net power output of the entire system is similar to the USB port peak power (2–6 W).• The specific net power output varies between 23.1 and 69.2 Wh/kgsettledsolids.

Design and commissioning of a multi-mode prototype for thermochemical conversion of human faeces

Highlights • Ignition, gasification and combustion of simulant and real faeces were studied.• Trials using fuel flowrates of 1.2 g/min and 7.5–8 L/min of air were carried out.• Mean temperatures of 440–670 °C allowed self-sustained combustion.• Maximum temperatures reached for real faeces were in the range of 1210–1240 °C.• Combustion trials lasted up to 160 min without external heat supply.

Evaluating oil palm fresh fruit bunch processing in Nigeria

Three routes of oil palm fresh fruit bunch (FFB) processing in Nigeria namely, industrial, small-scale and traditional were compared by means of determining fruit losses associated with each route. The fruits that are not recovered after each process were hand-picked and quantified in terms of crude palm oil (CPO), palm kernel (PK), mesocarp fibre (MF) and palm kernel shell (PKS). The energy value of empty fruit bunch (EFB), MF and PKS were used to determine the value of energy lost for each route. Additionally, the environmental implications of disposal of EFB were estimated, and socio-economics of the industrial and small-scale routes were related. The analysis showed that 29, 18, 75 and 27 kg of CPO, PK, MF and PKS were lost for every 1000 kg of FFB processed with the industrial route, whereas 5.6, 3.2, 1.4 and 5.1 g were lost with the small-scale route, respectively. Approximately 89 kWh and 31 kWh more energy were lost from MF and PKS with the industrial route than the other two routes, respectively. An equivalent of 6670 tonnes carbon dioxide equivalent of methane and nitrogen oxide was released due to the disposal of 29,000 tonnes of EFB from one palm oil mill. The monetary value of lost CPO per 1000 kg of FFB processed in the industrial route is more than the labour cost of processing 1000 kg of FFB in the small-scale route. The advantages of the industrial route are high throughput in terms of FFB processed per hour and high quality of CPO; however, high fruit loss is associated with it and therefore, the poorly threshed EFB is recommended to be fed into the small-scale route.

The Agglomeration of CaO-Based Sorbent Used to Capture CO2 in Fluidized Bed

High temperature CO2 capture via a CaO-based sorbent was investigated in a fluidized bed. The sorbents tested included natural limestone, pellets made from powdered lime with a calcium aluminate cement binder, mixtures of natural limestone and alumina with a ratio of 1:1 and 2:1. Air-combustion flue gas with a composition of 15% CO2 + 6% H2O + 3% O2 + 76% N2 at 680°C and oxy-combustion flue gas with a composition of 80% CO2 + 16% H2O + 3% O2 + 1% N2 at 950°C were used as a carbonation and calcination atmosphere separately to simulate real CFB running conditions. Results showed that pellets have a lower carrying capacity (g CO2/g calcined limestone or pellets) than nature limestone for the first few cycles mainly due to the existence of calcium aluminate cement (CaAl2O4) binder, while pellets have better cyclic activity than natural limestone. Solids agglomeration was found to be a big problem in the application of using Ca-based sorbent to capture CO2. The solids was not powdery as original ones and tended to clump together after few cycles, making it difficult to fluidize and some dead areas form in the fluidized bed. Agglomeration became severer as cycle number increase and pellets had a much slighter agglomeration than nature limetone due to large particle size. The two mixtures were run in different conditions and H2O was speculated to accelerate agglomeration.