Chemical Looping Combustion of Rice Husk

A thermodynamic investigation of direct chemical looping combustion (CLC) of rice husk is presented in this paper. Both steam and CO2 are used for gasification within the temperature range of 500–1200˚C and different amounts of oxygen carriers. Chemical equilibrium model was considered for the CLC fuel reactor. The trends in product compositions of the fuel reactor, were determined. Rice husk gasification using 3 moles H2O and 0 moles CO2 per mole carbon (in rice husk) at 1 bar pressure and 900˚C was found to be the best operating point for hundred percent carbon conversion in the fuel reactor. Such detailed thermodynamic studies can be useful to design chemical looping combustion processes using different fuels

Thermodynamic modeling and experimental study of rice husk pyrolysis

Pyrolysis of agricultural waste is a promising route for waste to energy generation. Rice husk is a type of agro-waste that is available in plenty in India. It can be used as feed for pyrolysis to produce different products such as (solid) coke and silica, (liquid) tar and other organics and syngas. HSC Chemistry computer aided code for thermodynamic modeling was used to predict the products of rice-husk pyrolysis in this research study. The pyrolysis of rice husk was carried out between 100-1200°C in the pressure range of 1 – 15 bar. The pyrolysis products predicted by HSC calculations were mainly solid coke, gases like H2, CO2, CO, CH4, with small quantity of aromatic compounds like C6H6, C7H8, C8H10 (ethyl benzene), C8H10 (xylenes) and C6H5 –OH. An experimental study for product validation was also done and the results are presented

Experimental study of effect of pressure on pyrolysis of biomass

Pyrolysis is thermal treatment of solid waste in the absence of an oxidizing agent (in inert atmosphere) which generally yields three products namely pyrolysis-oil (liquid), char (solid residue) and gas. The products obtained in pyrolysis can be further used as energy source. Rice husk and saw dust are considered as solid wastes in this study. The effect of temperature and pressure on pyrolysis was studied in a fixed bed reactor. The experimental runs were performed in nitrogen atmosphere. The temperature was varied from 300°C to 500°C, while the operational pressure was fixed at 4 bar, 7 bar and 10 bar. The products such as solid char, liquid pyrolysis oil and syngas were obtained. The solid char was characterized by CHNS analysis, while the pyrolysis oil was characterized by FTIR analysis

Experimental Study of CO2 Gasification of Biomethanation Waste

Gasification is one of prominent thermochemical processes generally used to convert organic feedstock to combustible syngas (CO and H2). An experimental study of biomass gasification using carbon dioxide as an gasifying medium was carried out in a fixed bed gasifier. The main aim of this study was to determine the effect of temperature on the output syngas. The present study reported the results for producing syngas with CO2 as gasification agent and biomass (rice husk and bio-methanation waste) as raw material. The gasification was performed at 700-900°C respectively and CO2 flow rate was maintained at 0.5 lpm. Maximum syngas production found at high temperature (900°C). The syngas analysis showed higher hydrogen yield at higher temperatures

Chemical looping combustion of biomass for renewable & non- CO2 emissions energy- status and review

World depends on fossil fuel combustion for thermal energy generation. Fossil fuel combustion leads to the generation of CO2 and ex-tinction of non-renewable resources. To meet the future energy demands replacement of existing technologies should take place in the view of large quantities of GHG’s emissions from fossil fuels and their extinction. Chemical looping combustion (CLC) is primarily a combustion technique with an inherent separation of CO2 from the flue gases. Due to its advantage of negative CO2 emissions, chemical looping combustion got attention of many researchers since last one and half decade. Recent research advancements in the CLC provided a platform for further research and developments in chemical looping combustion of biomass. This paper reviews the CLC of biomass to present the overview of chemical looping combustion technology and its status of biomass utilization as a fuel in CLC reactors

Energy Analysis in Combined Reforming of Propane

Combined (steam and CO2) reforming is one of the methods to produce syngas for different applications. An energy requirement analysis of steam reforming to dry reforming with intermediate steps of steam reduction and equivalent CO2 addition to the feed fuel for syngas generation has been done to identify condition for optimum process operation. Thermodynamic equilibrium data for combined reforming was generated for temperature range of 400–1000°C at 1 bar pressure and combined oxidant (CO2 + H2O) stream to propane (fuel) ratio of 3, 6, and 9 by employing the Gibbs free energy minimization algorithm of HSC Chemistry software 5.1. Total energy requirement including preheating and reaction enthalpy calculations were done using the equilibrium product composition. Carbon and methane formation was significantly reduced in combined reforming than pure dry reforming, while the energy requirements were lower than pure steam reforming. Temperatures of minimum energy requirement were found in the data analysis of combined reforming which were optimum for the process

An alternative process for gasoline fuel processors

The article explores the thermodynamics of an alternate hydrogen generation process – dry autothermal reforming and its comparison to autothermal reforming process of isooctane for use in gasoline fuel processors for SOFC. A thermodynamic analysis of isooctane as feed hydrocarbon for autothermal reforming and dry autothermal reforming processes for feed OCIR (oxygen to carbon in isooctane ratio) from 0.5 to 0.7 at 1 bar pressure under analogous thermoneutral operating conditions was done using Gibbs free energy minimization algorithm in HSC Chemistry. The trends in thermoneutral points (TNP), important product gas compositions at TNPs and fuel processor energy requirements were compared and analyzed. Dry autothermal reforming was identified as a less energy consuming alternative to autothermal reforming as the syngas can be produced with lower energy requirements at thermoneutral temperatures, making it a promising candidate for use in gasoline fuel processors to power the solid oxide fuel cells. The dry autothermal reforming process for syngas production can also be used for different fuels

Thermoneutral conditions in dry reforming of ethanol

The reaction enthalpy (ΔH) of reforming processes like steam and dry (CO₂) reforming is of great importance for scale-up and process development. Generally, the reforming processes are considered endothermic in nature. However, a detailed study of the reaction enthalpy of reforming process, taking the example of dry reforming of ethanol considered in this study, reveals the existence of exothermic reaction enthalpy at low temperatures. A study of reaction enthalpy of ethanol dry reforming within pressure (1–10 bar), temperature range (300–900 °C), and CO₂ to carbon in ethanol ratio (CCER 1–5) was initiated to determine the existence of thermoneutral temperatures for the overall reaction. The variation of thermoneutral conditions and product yields at the thermoneutral temperatures was studied. The utilization potential of the products generated at thermoneutral conditions was also evaluated. The low-pressure thermoneutral operation favored higher hydrogen production, lower methane and water formation, whereas the high-pressure thermoneutral operation favored product gas of lower syngas ratio with higher CO₂ conversion (utilization) in the process. The study can be extended to steam and dry reforming of other fuels to generate valuable products at thermoneutral conditions avoiding use of air in the process and subsequent N₂ dilution of the product gas

Hydrogen generation with CO₂ utilization: a solvay cluster study

The fuel cell economy is yet to start research programs in hydrogen generation with CO<SUB>2</SUB> utilization for hydrocarbon reforming processes used in fuel processor applications. A simple thermodynamic study using solvay clusters was done to investigate the feasibility of using the carbon species produced in the steam methane reforming process to produce value added chemicals. The results of this study are highly encouraging to start process development of closed systems of hydrogen generation with CO<SUB>2</SUB> conversion to acetic acid/acrylic acid making easier the commercialization of fuel cells and hydrogen energy. Such studies can be specifically carried out for different fuel processor systems