Cold Gas Efficiency Research Articles

From municipal solid waste (MSW) to hydrogen: Performance optimization of a fixed bed gasifier using Box-Benkhen method

Management of solid waste, generated from the municipal/urban sectors has always been troublesome to the governing authorities, especially of the developing and wide populated nations. Traditionally, the municipal solid waste (MSW) is dumped in low land areas for land-filling purpose or burnt in improper way which causes environmental pollution in short term as well as in long term basis. It is experienced that production from green fuel like hydrogen (H2) from MSW through gasification route will not only mitigate the MSW management issues but also reduce the dependency on fossil fuels. In this study, model development of a fixed bed gasifier considering steam gasification method is carried out for production of H2 rich syngas from MSW. Additionally, optimization study by employing Box-Benkhen method of Response Surface Methodology (RSM) is performed to find out the best values output parameters viz., H2 yield, lower heating value (LHV) of syngas and cold gas efficiency (CGE). It is noted that modelled gas data matches well with the experimental gas data. It is also imparted from the optimization analysis that the model offers H2 yield of about 64% with LHV of the syngas of about 11 MJ/kg and cold gas efficiency of about 92%, respectively. Desirability of the model predicted results are computed to be ‘0.79’ which signifies that results are substantially accurate and well acceptable.

Process Analysis and Design Considerations of a Low Carbon Methanol Synthesis Plant from Lignite/Waste Gasification

This study presents design considerations and an evaluation of a full-scale process chain for methanol and advanced drop-in fuel production derived from lignite/solid recovered fuel (SRF) feedstock. The plant concept consists of a high-temperature Winkler (HTW) gasifier coupled with an air separation unit (ASU), which provides a high-purity (99.55%) gasification oxidant agent. The concept includes the commercially proven acid gas removal (AGR) system based on cold methanol (e.g., Rectisol® process) for the removal of BTX and naphthalene components. With the involvement of Rectisol®, an almost pure CO2 off-gas stream is generated that can be further stored or utilized (CCS/CCU), and a smaller CO2 stream containing H2S is recovered and subsequently driven to the sulfur recovery unit (e.g., Claus process). One of the potential uses of methanol is considered, and a methanol upgrading unit is implemented. The overall integrated process model was developed in the commercial software Aspen PlusTM. Simulations for different feedstock ratios were investigated, ensuring the concept’s adaptability in each case without major changes. A number of parametric studies were performed concerning (a) the oxygen purity and (b) the reformer type, and a comparison against alternative methanol production routes was conducted. Simulations show that the proposed system is able to retain the cold gas efficiency (CGE) in the range of 79–81.1% and the energetic fuel efficiency (EFE) at around 51%. An efficient conversion of approximately 99.5% of the carbon that enters the gasifiers is accomplished, with around 45% of carbon being captured in the form of pure CO2. Finally, the metrics of EFE and total C for the conversion of methanol to liquid fuels were 40.7% and 32%, respectively, revealing that the proposed pathway is an effective alternative for methanol valorization.

Multizone model of a refused derived fuel gasification: A thermodynamic Semi-empirical approach

Substitution of fossil fuels by sustainable energy sources has raised attention worldwide. Refuse derived fuel (RDF), which is the combustible fraction of Municipal solid waste (MSW), is used as an alternative fuel through combustion route. The gasification of RDF is gaining importance due to the operational issues of RDF combustion. The multizone RDF gasification model is developed to predict syngas composition in the present study. A stoichiometric approach is followed for modelling the pyrolysis and combustion zone. The reduction zone is modelled as a cylindrical fixed bed reactor with a uniform cross-sectional area. The developed set of differential equations is solved using MATLAB to predict the syngas properties. The novelty lies in the fact that the model can predict the output of each zone satisfactorily since the model assumptions are more realistic and cater to the heterogeneous nature of RDF. The impact of Equivalence ratio (ER), moisture content and reduction zone length on the performance of the gasifier are evaluated. The optimum values of lower heating value (LHV), gas yield, cold gas efficiency (CGE) and carbon conversion efficiency (CCE) for three different RDF at optimum ER is determined. Notably, 90% of the conversion is achieved within 60% length of reduction zone for all three types of RDF at all ERs. Predicting syngas properties can pave the way for the process integration of RDF gasification-based syngas in various industrial applications.

INFLUENCE OF THE OXIDIZER ON THE FORMATION AND PURIFICATION EFFICIENCY OF ACID GASES PRODUCED DURING ASPHALTENE GASIFICATION

Link for citation: Ermolaev D.V., Daminov A.Z. Influence of the oxidizer on the formation and purification efficiency of acid gases produced during asphaltene gasification. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2022, vol. 333, no. 4, рр. 215-223. In Rus.
 The relevance of the study is determined by the need to understand the influence of the oxidizer on the formation of acid gases (CO2, H2S, COS and CS2) during thermal decomposition of high-viscosity hydrocarbons. This is important for predicting the purification efficiency of the produced gasification products and estimating the economic costs. The aim: using the simulation to study the effect of an oxidizer in the form of steam on the composition and properties of asphaltene gasification products obtained from natural bitumen, as well as to determine the cleaning efficiency depending on the amount of steam and the absorbent based on NaOH water-alkaline solution. Object: asphaltene of natural bitumen of Ashalchinskoe field of the Tatarstan Republic (Russia), oxidizer in the form of steam, the value of which varied from 0,1 to 1 depending on the amount of asphaltene. Methods: simulation of asphaltene gasification and acid gas absorption taking into account influence of an oxidizer in a form of steam with regard for basic chemical kinetics, ultimate analysis and TGA. Simulation results of gasification and absorption showed that steam used as an oxidizer during asphaltene gasification has a significant influence on the composition and properties of gasification products, as well as on the purification of syngas. With the increase of steam, a parabolic dependence of the concentrations of syngas components is observed, which values decrease with time, except for CO2. The calorific value of syngas decreases from 11,3 to 7,2 MJ/m3 and the cold gas efficiency increases from 53,4 to 62,5 % due to growth of syngas yield. As the amount of steam increases, the amount of absorbent decreases and the purification efficiency of acid gases rises. Thus, the amount of absorbed CO2 increases by 20,7 % while the absorbent decreases by 6,7%. At the same time the amount of absorbed H2S increased by 0,39 % with decrease of NaOH by 40,9 %.

Sustainable utilization of bamboo through air-steam gasification in downdraft gasifier: Experimental and simulation approach

This study presents a detailed analysis to utilize bamboo which is a widely available feedstock in North-Eastern states of India, via air-steam gasification with an estimated potential to generate 23.92 PJ energy. The study was carried out in a downdraft gasifier (10 kWe) to produce hydrogen-rich syngas. The effect of the steam to biomass ratio (0.1–0.4) on the gas composition and performance parameters is studied. The maximum H2 yield (37.12%) is found in the steam to biomass ratio of 0.35. The lower heating value and cold gas efficiency are in the range of 4.72–5.71 MJ/Nm3 and 62.1–85.7%, respectively. The higher steam to biomass ratio of above 0.35 led to cooling of combustion and reduction zone and negatively affected the performance parameters of the gasifier. The experimental data of the present study is validated with model data and root mean square error is found in the range of 4.24–7.76 and 2.88–10.08 from experimental data from literature with the developed model. Results show that it is economical and viable to use small-scale gasifiers to produce syngas from bamboo to meet the local energy demand. This is of importance in small and isolated communities that are near bamboo forest.

Comparative evaluation of microwave and conventional gasification of different coal types: Experimental reaction studies

Effects of gasifier conditions (microwave or conventional) on the gasification characteristics of four different types of coal are evaluated by analysis of gaseous species generated during pyrolysis and gasification reactions. Four different coal samples are tested: a lignite (Mississippi), a low-ash subbituminous (Wyodak), a high-ash subbituminous (Usibelli), and a low volatile bituminous (Pocahontas #3). Gas composition, overall yields, carbon conversion efficiency, and cold gas efficiency are evaluated to compare gasification reactivity of the different coal types under microwave and conventional heating. During microwave pyrolysis (Ar atmosphere), greater selectivity of syngas species (H2 + CO) and greater overall non-condensable gas yields are observed, compared to conventional pyrolysis for all coals tested. The high yield of syngas during microwave pyrolysis is attributed to primary pyrolysis gases subsequently gasifying the char of the same sample to produce greater amounts of H2 and CO. During microwave gasification (CO2 atmosphere), selective heating and formation of hotspots within the coal enable the reverse Boudouard reaction to occur at a low bulk gasification temperature of 700 °C, which is less favorable under thermal gasification at this temperature. Yields of syngas are much higher under microwave gasification of all coals. Carbon conversion is found to have a linear correlation with volatile matter of the parent coal. Carbon conversion and cold gas efficiency are highest for coals gasified under microwave irradiation, and gasification reactivity of the four coals was determined to be dependent on the coal type.

Investigation of characteristics of gas and coke residue for the regime of quasi- and non-stationary steam gasification of coal in a fluidized bed: Part 1

The steam oxygen-free gasification allows deep processing of coal and obtaining gas with high contents of H2 and CO. The design of dual fluidized bed gasifiers (DFB) is considered promising. There are insufficient experimental data on the steam gasification process in DFB for more accurate mathematical modeling. The paper presents the experimental results in dynamics of the quasi-stationary and non-stationary gasification of two types of coals in a laboratory gasifier. It has been established that when using superheated steam for preliminary and main gasification process, it is possible to obtain a gas with a total content of H2 and CO of more than 75% vol, maximum cold gas efficiency 87%. The conditions for the expedient use of two chambers for gasification of coals of different degrees of metamorphism are identified. The gasification regimes that will increase H2 and CO formation in DFB are determined. This research substantiate the necessarily to use only steam in DFB for improving the synthesis gas quality.

Design, instrumentation, and operation of a standard downdraft, laboratory-scale gasification testbed utilising novel seed-propagated hybrid Miscanthus pellets

Biomass gasification remains an attractive option to impact climate chaos; however, the technology presents challenges in tolerance to feedstock variability and tar production, which can limit the overall process efficiency, gasifier performance, durability and downstream syngas utilisation. The primary objectives of this study were to compare two gasifier design approaches using different reaction kinetics, based on multiple or singular oxidation and gasification reactions, and build and test a novel, flexible, laboratory-scale downdraft gasifier to convert pellets from UK hybrid Miscanthus into syngas, whilst deploying inexpensive instrumentation methods. The experimental gasification parameters studied were carbon conversion efficiency, gas yield, cold gas efficiency and gas heating values. The performance study shows that the system achieved good average temperature (842–866 °C) in the reduction zones for equivalence ratios between 0.25 and 0.35. The optimum values for carbon conversion efficiency, cold gas efficiency, heating values (HHV) of product gas and gas yield were 74%, 32%, 4.17 MJ/m3 and 1.32 m3/kg(biomass), respectively. The reported performance parameters for the new seed-propagated hybrid Miscanthus in the present study were comparable to those from conventional Miscanthus pellet gasification in downdraft gasifiers but these new hybrid varieties offer advantages in productivity over broader climatic regions compared to conventional varieties.

Three-stage modelling and parametric analysis of a downdraft biomass gasifier

Syngas production from biomass resources suggest considerable privileges to attain energy sustainability in future. Design and control strategies are essential to extend the technology of biomass gasifiers, which require reliable model developments. The overarching contribution of this study is to develop and evaluate a three-stage biomass gasifier model. The model consists of three successive sub-models for drying and pyrolysis, partial oxidation and char reduction reactors. The pyrolysis of raw material is simulated based on the ligno-cellulosic structure of the biomass by adopting comprehensive kinetic rate modelling approach. The partial oxidation sub-model is built by axis-symmetric 2D transport equations including detailed chemical scheme. Char reduction sub-model is extended based on axis-symmetric 2D DPM model accompanied by appropriate chemical kinetic scheme considering heterogeneous and homogeneous reactions. Accuracy of each sub-model is separately verified by comparison with available numerical and experimental data. Moreover, the correctness and predictability of the complete gasifier model is evaluated using two experimental reports. For both cases, investigations demonstrate high resolution agreement between the results of the developed model and available experimental measurements both thermally and chemically. Furthermore, a parametric analysis is conducted to investigate the gasifier performance against the variations of the main system operating parameters including the type of the feeding biomass and its moisture content, equivalence ratio and air initial temperature. Based on the results, higher volatiles mass fractions and lower char mass fraction have been produced from pyrolyzing of hardwood in comparison with beech wood. Also, Results reveal that with increase of the moisture content from 15% to 35%, syngas LHV and cold gas efficiency reduce by 1.9559 MJ . kg −1 and 25.78% respectively, while H 2 mole fraction at the gasifier outlet rises by 0.90%. On the contrary, growth of equivalence ratio from 2 to 10 leads to the drastic increase of syngas LHV by 5.6404 MJ . kg −1 , however, cold gas efficiency peaks to 82.75% at the equivalence ratio of 4. Besides, varying the inlet air temperature over a range of 500 K–1300 K causes 0.6938 MJ . kg −1 growth of syngas LHV as well as 9.43% rise of cold gas efficiency. • A conceptual three-stage model is developed to simulate the performance of a downdraft biomass gasifier. • The model includes three separate successive sub-models for pyrolysis, partial oxidation and char reduction. • Results of each sub-model and the whole three-stage model are experimentally validated. • Three-stage model is evaluated for two different lignocellulosic feedstocks. • The effects of the key operating parameters on the gasifier performance are analyzed.

Rice husk fixed bed gasification for circular economy in compact rice mills

ABSTRACT Considering the physicochemical properties of residual rice husk, which is suitable for gasification and its vast availability in Colombia, an experimental analysis of the energy potential of rice husk for small-scale fixed bed gasification processes was conducted, thereby facilitating the implementation of the circular economy model in compact rice mills. Because of the impact of air flow on the process equivalence ratio (ER), gas calorific value, and gasifier thermal power, the optimum air superficial velocity (VSair) considering the end use of the producer gas for both internal combustion engines (ICEs) and atmospheric burners (AB), is examined. According to the results, biomass consumption rate, cold gas efficiency (CGE), and process temperature increased in the ranges 1–1.55 kg/h and 45–65% and 825–950°C, respectively, when ER goes from 0.23 to 0.3. To obtain the highest process performance, the process should be conducted at a VSair ~ 5.1 m/min and ER ~ 0.3. Under these parameters, a gas with thermal power and lower heating value (LHV) of 3.6 kWth and 4.78 MJ/Nm3, respectively, was obtained. These properties allow for an engine fuel quality (EFQ) of 1817 kJ/kg. For comparison, an ICE designed to be fueled with natural gas (EFQ of natural gas approx. 2650 kJ/kg) would have a ~ 30% drop in its maximum power when fed with the producer gas obtained through rice husk gasification.

Syngas analysis by hybrid modeling of sewage sludge gasification in downdraft reactor: Validation and optimization

In general, sewage sludge obtained from the municipal wastewater treatment plant is one of the significant sources of waste for renewable energy production. In this article, the thermochemical conversion of sewage sludge through a downdraft gasifier is addressed. Two-zone equilibrium and one-zone kinetic model as the hybrid modeling of the sewage sludge gasification is proposed. Three zones of drying & pyrolysis, oxidation, and (char) reduction are modeled by using an integrated thermodynamic stoichiometric equilibrium and Langmuir-Hinshelwood kinetic model. Through the validation and sensitivity analysis, the syngas compositions and cold gas efficiency show to be sensitive to the variations of inlet flow rates of gasifying agents (air and steam), the inlet flow rate of feedstock (sewage sludge), and the temperature and pressure of the gasifier. Through the response surface methodology-based optimization algorithm, the proper operating conditions of the process can be found under the prescribed operating constraints.

Non-Thermal Air Arc Plasma Assisted Biomass Gasification

A novel small-scale biomass gasification system assisted by a non-thermal air arc plasma is introduced in this paper and the gasification experiment setup, procedure and gasification results are described in detail. The results show that the production of syngas (CO and H2) is in the range of 1.14 Nm3/h to 1.46 Nm3/h during the system normal operation at plasma power consumption 120 W and biomass feed rate 3360 g/h, and the volume fraction of syngas in produced gas is in the range of 20.2% to 23.89%. The maximum cold gasification efficiency is 44.56% and the minimum specific energy consumption (defined as the ratio of plasma power consumption to the heat power content of the produced gas) of the gasification system is 2.18%, which is much lower than that of gasification system with thermal plasma.

Hydrogen rich syngas production from food waste via an integrated two-stage process of in-situ steam gasification after fast pyrolysis

ABSTRACT This study introduced an integrated two-stage process (ITP) for treating the mixed food waste (MFW) and producing syngas with higher hydrogen fraction where in-situ steam gasification was conducted after fast pyrolysis at the same temperature. Characteristics of syngas (syngas yield, composition, H2 yield, and high heating value (HHV)) from the proposed approach was first compared with that from conventional overlapping process (COP) of steam gasification process at the same temperature of 700°C and then with that from ITP at a higher temperature of 850°C. Syngas yield from ITP at 700°C (0.91 m3/kg) was almost the same as the syngas yield from COP at 700°C (0.85 m3/kg); however, the hydrogen and CO fraction were much higher (H2: gasification part~ 63%, average ~ 57.8%; CO: gasification part ~ 25%, average ~ 24%) than that from COP at 700°C (H2: 52%, CO: 19%). The hydrogen fraction in syngas further increased to 68% (from the gasification part) on increasing the ITP temperature to 850. Moreover, the syngas yield increased significantly (1.51 m3/kg) at the higher temperature of 850°. Finally, change in HHV values and corresponding changes in cold gas efficiency (CGE) were also presented to evaluate the process performance.

An improved kinetic modelling of woody biomass gasification in a downdraft reactor based on the pyrolysis gas evolution

Biomass gasification technology is evolving and more research through modelling alongside the experimental work needs to be performed. In the past, all the attention has been concentrated on the combustion and reduction stages to be the controlling reactions while the pyrolysis is modelled as an instantaneous process. In this study, a new enhanced model for the gasification process in the downdraft reactor is proposed with a more realistic representation of the pyrolysis stage as a temperature-dependent sequential release of gases. The evolution of the pyrolysis gas, followed by the combustion and reduction reactions, are kinetically controlled in the proposed model which is developed within the Aspen Plus software package. The simulation of the reactor temperature profile and the evolution of the pyrolysis gas is carried out in an integrated MATLAB and Aspen Plus model. The proposed model has been validated against experimental data obtained from the gasification of different woody biomass types and considering a range of scale reactor and power loads. The predicted results are in very good agreement with the experimental data, and therefore the model can be used with confidence to perform a sensitivity analysis to predict the performance of a gasifier at different load levels corresponding to the air flow rate range of 3–10 L/s. As the supplied air flow rate increases, the LHV decreases but the gas yield behaves conversely, and in turn the cold gas efficiency is maintained at a good level of energy conversion at ≥ 70%. Furthermore, the variation in the biomass moisture content, which is commonly in the range of 5–25 % has a significant effect on the gasification efficiency. Such that biomass that has a high moisture content substantially reduces the CO content and consequently the LHV of the produced gas. Hence, it is important to maintain the moisture content at the lowest level.

Optimization study on operation conditions of an industrial-scale circulating fluidized bed coal gasification

This research was carried out on a new industrial circulating fluidized bed (CFB) gasifier with output power of 111 MW. In order to realize stable operation and improve economic benefits, a series of experimental studies were carried out during the hot commissioning of the gasifier. The effects of O2/coal ratio, oxygen concentration and secondary gasification agent on gasification indices were investigated. The boundary conditions for the safe and stable operation of the gasifier were obtained, which provides a strong support for the commercial operation of the gasifier. The results showed that, the gasifier can operate stably between 940 and 970 ℃. As the O2/coal ratio increases from 0.31 to 0.36 Nm3/kg, the dry gas yield increases from 2.5 to 2.8 Nm3/kg, carbon conversion rate increases from 78.1 to 82.1% and cold gas efficiency increases from 68.9 to 71.5%, while the effective gas composition (CO, H2 and CH4) decreases from 51.9 to 49.3% and heat value of gas decreases from 6.6 to 6.3 MJ/Nm3. With the increase of oxygen concentration, the effective gas composition and heat value of gas increase. When the oxygen concentration of gasification agent reaches 25%, the temperature is about 960 ℃ and the heat value of gas can reach 6.2 MJ/Nm3. The introduction of secondary gasification agent (O2 + H2O) makes the riser temperature more uniform, but it will reduce the effective gas content and gas heat value to a certain extent.

Towards a sustainable waste-to-energy pathway to pequi biomass residues: Biochar, syngas, and biodiesel analysis

The waste-to-energy (WTE) valorization pathway of Caryocar brasiliense (pequi) seeds was investigated via pyrolysis, gasification, and transesterification to understand its potential as biochar, syngas, and biodiesel. First, the pyrolysis (300–700 °C) was conducted in N2 atmosphere for pequi seeds (PS) and pequi seeds without its extractives (PSWE), characterizing its biochar properties. The PSWE was then gasified at 1000 °C under O2/N2, O2/CO2/N2 and O2/H2O/N2 atmospheres to evaluate the characteristics of the producer gas. The PS extractives were then transesterified and characterized for biodiesel production. Finally, a multiple-criteria decision analysis assessed the PS products’ potential within the thermochemical routes. The results evidenced better biochar (up to 22.29% HHV enhancement, higher mass and energy yield, up to 75.9 and 85.5% reduction of O/C and H/C, respectively, and enriched N content) via PSWE pyrolysis than PS considering biofuel application and optimistic perceptions for soil amendment. This indicates that the preceding extraction of vegetal fat from PS strengthens the WTE by including further processing of extracted oil. The produced syngas under O2/H2O/N2 gasification atmosphere showed better applicability as a biofuel (16.37 MJ·kg−1 lower heating value, 107.33% cold gas efficiency, and 113.55% carbon conversion efficiency) with up to 24% higher success rate. The transesterification of the extractives revealed its potential (98% conversion rate) for use as feedstock for in situ power generation, or blended for biodiesel production. The results provide insights into the circular economy in agro-extractivist communities that may support Brazil’s small and medium agro-food industries with their energy demands.

Mathematical Modeling of Waste Engine Oil Gasification for Synthesis Gas Production; Operating Parameters and Simulation

The release of waste oil into the environment will have destructive effects. Gasification is an advanced and environmentally friendly process for converting waste oils into clean combustible gas products. Thermochemical equilibrium modeling has been used in this method to predict the performance of a downdraft gasifier. This model uses the thermodynamic equilibrium of gasification reactions to predict the gases produced in the gas mixture. Having the percentage of gas components produced, different characteristics of the produced gas including H2:CO ratio, process temperature and calorific value of the produced gas, Cold gas efficiencies and carbon conversion efficiency are also obtained. The effect of equivalence ratio, oxygen enrichment and pressure on gasification properties is analyzed. The simulation results are compared with the reported experimental measurements through which the numerical model is confirmed. The results indicated that the equivalence ratio (mole of air in gasification per mole of air in combustion) between 0.4 and 0.42 had the potential to yield the highest calorific value about 10.5 Mj.m-3. The temperature of gaseous mixture in this range will be 2000 K that can be used for other processes such as steam generation. Using pure oxygen instead of air reduces the efficiency of the gasifier from 78% to 55%. Pressure changes from 10 to 65 bar cause gas mixture temperature changes from 1684 to 1690 Kelvin. The H2:CO ratio decreases from 1.6 to 0.6 with increasing equivalence ratio and increases from 1.2 to 1.6 with changes in oxygen enrichment.

Blends of bio-oil/biogas model compounds for high-purity H2 production by sorption enhanced steam reforming (SESR): Experimental study and energy analysis

• SESR of bio-oil/biogas blends leads to renewable high-purity H 2 production. • H 2 yield of 87.1% is experimentally obtained at 625 °C and 2.5 bar. • H 2 purity of 98.6 vol% is achieved at 625 °C and 2.5 bar. • Higher temperature and steam/C molar ratio, but lower pressure, favor H 2 production. • Biogas addition increases the energy efficiency of the bio-oil SESR process by 1.34%. H 2 production by sorption enhanced steam reforming (SESR) of bio-oil/biogas blends was demonstrated in a fluidized bed reactor. It combines steam reforming (SR) with simultaneous CO 2 capture by a solid sorbent. SESR was performed on a Pd/Ni-Co catalyst derived from a hydrotalcite-like material (HT) using dolomite as CO 2 sorbent. Bio-oil from fast pyrolysis of biomass is a carbon–neutral and renewable energy source with great potential for clean H 2 production by steam reforming processes. Biogas is also a promising renewable bio-based resource for hydrogen generation that can be used to increase the H 2 production of a biomass-based plant. In turn, it could improve the energy efficiency of the process due to the exothermic reaction of the CO 2 contained in biogas with the sorbent. Bio-oil composed of acetic acid and acetone (1/1 mol/mol) and biogas composed of CH 4 and CO 2 (60/40 vol%) were used as fuels. They were blended (50 wt% bio-oil + 50 wt% CH 4 ) to study the SESR process. Effects of temperature, steam/C molar ratio, and pressure on the process performance were evaluated. SESR results showed an effective reforming of bio-oil/biogas blends and an enhancement in the H 2 production and fuel conversion compared to conventional SR. Higher temperature and steam/C ratio, but lower pressure, favored H 2 yield and purity. High H 2 yield (87.1%) and H 2 purity (98.6 vol%) were obtained at 625 °C and 2.5 bar (steam/C molar ratio three times higher than the stoichiometric value). The thermodynamic energy analysis of the SESR of bio-oil/biogas blends rendered 1.34% higher cold gas efficiency (CGE) than bio-oil SESR.

Effects of sewage sludge blending on techno-economic performance of Integrated Gasification Combined Cycle (IGCC) system

Municipal sewage sludge (SS) can be used as an alternative carbon-neutral feedstock for energy utilization owing to its considerable higher heating value compared with lignite coal. It is potential to efficiently co-utilize SS by coal-sludge-slurry gasification technology avoiding the energy consumption for SS drying process. In this study the effects of SS blending on the techno-economic performance of Integrated Gasification Combined Cycle (IGCC) systems based on different kinds of gasification technology and coal are analyzed. The results show that the overall energy efficiency of the system based on dry gasifier is more sensitively affected by the blending of SS than the one based on wet gasification due to the energy consumption during drying process. For wet gasification technology, the overall energy efficiency for coal A first increases from 45.17% to 45.26% and then reduces to 44.77% with the SS mix ratio, while the overall energy efficiency for coal C declines from 38.58% to 38.03%. The results indicate the overall energy efficiency has positive correlation with the cold gas efficiency instead of ash fusion temperature and the effects of SS addition on the overall energy efficiency can be qualitatively estimated by analyzing the cold gas efficiency. In most cases the blending of SS in IGCC systems benefits the economic performance and the net present value of the system based on wet gasification and coal A could be increased by 88% due to the increasing power output and the SS treatment subsidy.

Characteristics of steel slag as an oxygen carrier for chemical looping gasification of sewage sludge

A comprehensive study was conducted to assess the characteristics of basic oxygen furnace slag (BOFS) and electric arc furnace slag (EAFS) as oxygen carriers for chemical looping gasification (CLG) of sewage sludge (SS). The surface roughness and wear resistance of BOFS were found to be higher than those of EAFS. Further, the oxygen transport capacity of BOFS was higher than that of EAFS at 800 ° C and 900 ° C with the same redox cycles. As the mass ratio increased, the carbon conversion rate and CO2 concentration gradually increased, while the water conversion rate, cold gas efficiency, and H2 and CO concentrations initially increased and then decreased. Both BOFS and EAFS as oxygen carriers had the highest carbon conversion rate and cold gas efficiency when the steam flow rate was 0.15 g min−1. The cyclic reactivity of BOFS as an oxygen carrier in the CLG process decreased faster than that of EAFS. However, the content of combustible components of BOFS as an oxygen carrier was significantly higher than that of EAFS in each cycle. Overall, these results provide a theoretical basis for steel slag as an oxygen carrier for the CLG of SS.