Hot Flue Gas Research Articles

Secondary reactions of volatiles upon the influences of particle temperature discrepancy and gas environment during the pyrolysis of scrap tyre chips

Pyrolysis process is one of the potential routes to convert waste scrap tyres into high-value resources such as liquid oil that is low in oxygen and high in valuable hydrocarbons. Although many studies have been conducted, the understanding of the fundamental science underpinning the pyrolysis of scrap tyre chip is still far from complete. This paper has examined the mild pyrolysis of scrap tyre chips at 600 °C, in an integrated manner by examining the co-effects of several key parameters including heating rate, volatile residence time, tyre chip size and non-inert gases (CO2 and/or H2O) on the quality of tars. In particular, we aimed to elucidate the influences of particle temperature discrepancy to the surrounding gas environment and reactive gas on the tar yield and properties, under the simulated fixed-bed/rotary kiln condition that is either heated directly by hot flue gas or indirectly by reactor wall. It has been confirmed that, in a simulated fixed-bed reactor with the absence of carrier gas, the particle temperature discrepancy can be correlated exponentially to the secondary cracking extent of volatiles in a temperature discrepancy range of 100 °C. Upon an increase on the temperature discrepancy by either increasing the heating rate or tyre chip size, the inherent long-chain aliphatics preferentially underwent scission, cyclisation and polymerisation, enhancing the yields for both heavy aromatics and methane – rich light gases. The use of carrier gas (i.e. hot flue gas) is beneficial in improving tar yield and aliphaticity. As a convective heating source, it heated particles slowly and also swept out volatile vapours immediately, thereby minimising the secondary reactions. For the two major components, CO2 and steam in hot flue gas, CO2 is rather inert at 600 °C, while steam is reactive enough to reduce the heavy hydrocarbons via steam reforming reaction, upon the catalytic effect of the nascent char derived from scrap tyre chips. The hydrogenation of unsaturated alkene and aromatics was also improved, and even the methanation reaction of CO on the nascent char surface, thus leading to the overwhelming dominance of CH4 in the pyrolysis gas.

Industry 4.0 based process data analytics platform: A waste-to-energy plant case study

Industry 4.0 and Industrial Internet of Things (IIoT) technologies are rapidly fueling data and software solutions driven digitalization in many fields notably in industrial automation and manufacturing systems. Among the several benefits offered by these technologies, is the infrastructure for harnessing big-data, machine learning (ML) and cloud computing software tools, for instance in designing advanced data analytics platforms. Although, this is an area of increased interest, the information concerning the implementation of data analytics in the context of Industry4.0 is scarcely available in scientific literature. Therefore, this work presents a process data analytics platform built around the concept of industry 4.0. The platform utilizes the state-of-the-art IIoT platforms, ML algorithms and big-data software tools. The platform emphasizes the use of ML methods for process data analytics while leveraging big-data processing tools and taking advantage of the currently available industrial grade cloud computing platforms. The industrial applicability of the platform was demonstrated by the development of soft sensors for use in a waste-to-energy (WTE) plant. In the case study, the work studied data-driven soft sensors to predict syngas heating value and hot flue gas temperature. Among the studied data-driven methods, the neural network-based NARX model demonstrated better performance in the prediction of both syngas heating value and flue gas temperature. The modeling results showed that, in cases where process knowledge about the process phenomena at hand is limited, data-driven soft sensors are useful tools for predictive data analytics.

Design, fabrication, and performance evaluation of a novel biomass-gasification-based hot water generation system

Design and development of a novel 22kWth hot water generation system comprising a biomass-gasification unit in the core and an integrated fire-tube water heat exchanger in the annulus is reported. Producer gas from the gasifier is combusted in a burner and the resulting hot flue gases are routed back through the helical tube to heat the water contained within the annular shell. This allows recovery of the thermal energy typically lost from the outer surface of a conventional gasification system. The simple design improvisation leads to a doubling of the overall efficiency (≈48%) compared to a standard system with physically separated gasifier and heat exchanger units (≈24%). The developed system holds promise in domestic and industrial water heating applications. Overall, this integrated design presents an efficient and environment-friendly waste-to-value concept and proposes a meaningful use of the underutilized 36 EJ/annum potential of biomass from crop residue globally.

Numerical simulation of impact and solidification of melting dust on spherical bead surface and experimental validation

The impact and solidification processes of single melting tin dust at the micron scale on a spherical bead were numerically studied with hot flue gas flow. The geometrical evolution of dust impacting on hot bead and spreading without solidification involved initial spreading, retraction and oscillation, and stabilizing. The increased impact angle was found to reduce maximum spread area, weaken retraction and oscillation, and raise steady spread area. Dust impacting on cold bead completely solidified after liquid spreading and solidification without retraction and oscillation. Increased impact angle raised solidification sliding distance, whereas it reduced solidification spread area. Then, the effects of bead temperature, dust inlet velocity and size on the sliding and spreading of dust were studied, and the results indicated that increasing bead temperature, dust inlet velocity and size could raise solidification sliding distance and solidification spread area. With the dusts continually impacting on the bed, a dust layer forms at the front of bead, being different from that of solid dust, which becomes thick firstly, and then spreads from bead front to sides.

A PROPER SELECTION OF HOT AND COLD UTILITIES IN A PLANT CONTAINING MULTIPLE HEAT EXCHANGER NETWORKS

In this paper, the hot and cold utilities of a complex natural gas refinery containing multiple heat exchanger networks (HENs) were properly selected. Following using pinch analysis for designing the HENs of the natural gas refinery, this selection could be done by considering available utilities in the plant under consideration. The plant network was divided into the five heat exchanger networks for better and precise estimation of utility requirements in each smaller network. By comparing the type and temperature level of the utility required in each network, the best utility could be selected, in order to use as the heating and cooling media in the plant network with a considerable reduced operating cost of the system. The results show that in the new network design, there was about 38 and 100% reduction in cooling air and BFW respectively, but 45% increase in cooling water, as cold utilities and almost 64.4, 30.0, 90.9 and 100% reduction in HP steam, LP steam, hot flue gas and electric heater as hot utilities, respectively relative to the existing network.

Flameless Combustion Characteristics of Producer Gas Premixed Charge in a Cyclone Combustor

Producer gas (PG) flameless combustion in a premixed cyclone combustor was investigated experimentally and numerically. The experiment was carried out over different premixed charges of air/fuel mixture and inlet nozzle diameters under PG fuel input power up to 80 kW. Exhaust temperature was above 1050 K for the whole operating range with CO emission below 0.08 Vol.% and NOx emission of 420 ± 30 ppm. Swirl flow field, internal hot flue gas recirculation, and temperature distributions inside the combustor were numerically studied. The numerical results were validated by the experimental data and it confirmed the achievement of temperature uniformity throughout the combustion volume when operated under flameless combustion mode. The reaction regime of PG flameless combustion was further analyzed with respect to turbulent scale characteristics. The present PG flameless combustions were typified by both moderate Damkohler and Karlovitz numbers, falling into the Flamelets in eddies regime.

Water and power consumption reduction by gas conditioning tower system modification in cement industry

Gas conditioning tower (GCT) is a vital equipment in cement industries. The main principle in this equipment is evaporative cooling, i.e. reducing the temperature of the hot flue gas by evaporation of cooling water. Thus, the water consumption is large enough to be able to cool the hot gas from about 400 °C to 150 °C or less. In this case study, the water consumption reduction of a GCT is evaluated before and after modification. The modification of the GCT system includes the change in operating condition and tower mechanical construction which are installation of flow deflector in the inlet pipe, the addition of two perforated plates, the reduction of the nozzle sprayers and the addition of tower length. Meanwhile, the dust removal replacement from Electrostatic Precipitator (EP) to Bag Filter (BF) system allows higher outlet gas temperature of the GCT which could reduce the water and power consumption significantly. The modification effect of the GCT system is analyzed in terms of water demand and energy savings using 100 days real plant data from PT Indocement Tunggal Prakarsa, Indonesia (ITP). It is shown that the modification can reduce the total water consumption by about 20 % and the specific power consumption by about 0.5 kWh/ton of Raw Mill product. The general equation for cooling water demand calculation based on heat balance has been modified as well for better real data approach incorporating air spray flow into the equation.

Effects of the Distribution of Heating Surface Areas on the Performance of Bagasse Boiler

Main components of a bagasse boiler are furnace, evaporator, superheater, boiler bank, economizer, and air heater. Combustion of fuel and air in the furnace produces thermal energy that is used to evaporate feed water in the evaporator. Hot flue gases from the furnace also contribute to increasing steam temperature in the superheater. Hot flue gases then pass through the boiler bank, resulting in additional water evaporation. After that, they pass successively through the economizer, in which feed water temperature is increased, and the air heater, in which air temperature is increased, before being exhausted to the atmosphere. It is known qualitatively that the boiler efficiency is increased with the heating surface area of each component. Quantitative effects of increasing heating surface areas, however, require a bagasse boiler model that takes into account their effects. The unavailability of a suitable model in the open literature is the main reason why this paper is written. The proposed model assumes the superheater is a radiative-convective heat exchanger, whereas boiler bank, economizer, and air heater are convective heat exchangers. The model is then used to determine how the boiler efficiency is affected by the heating surface areas of superheater, economizer, and air heater. It is found the boiler efficiency is most sensitive to change in economizer surface area.

Numerical simulation of ignition mode and ignition delay time of pulverized biomass particles

In this paper, numerical simulations were carried out to identify the mode of ignition and ignition delay time of pulverized biomass particles in hot flue gas produced by a methane/air flame. In the experiments, it was observed that for most biomass residues the dominant combustion mode was the staged gas-phase ignition in the surrounding gas followed by surface ignition at the char surface. There were some exceptions to this general trend, e.g. wheat straw particles, which ignited at the surface of the particle under some temperature conditions. Moreover, temporally and spectrally resolved images of the single burning particles were obtained in the experiments and CH* chemiluminescence at different stages of biomass conversion was recorded. In this study, by means of a detailed numerical model for conversion of biomass particles and employing detailed gas chemistry mechanism, the ignition mode and ignition delay time of the particles are studied. The model is able to distinguish between different ignition modes of the particles in agreement with the experimental data. The underlying physics behind shifting ignition mode from homogeneous ignition to heterogeneous ignition for wheat straw are discussed. The ignition delay times for different biomass sources at different conditions are calculated and the results are in good agreement with the experimental data. Apart from the detailed model, CFD simulations are performed to assess the flow and combustion process (temperature, O2 concentration and velocity difference between the ambient gas and the particle) around the particle. The CFD results show similar trends compared with the CH* chemiluminescence from the particle at different times during the devolatilization stage.

Numerical Simulation of Internal Flow in Direct Burning Coal-fired Hot Flue Gas Furnace

In this paper, a direct burning coal-fired hot flue gas furnace is taken as the research object. By using the SIMPLEC algorithm and the pressure based implicit solver in the analysis software FLUENT, the temperature, velocity and pressure distribution cloud chart and the CH4, CO, O2 and CO2 content distribution clouds are obtained by the numerical simulation of the gas solid two phases in the direct burning hot flue gas furnace. Through analysis, the high temperature zone in the hot flue gas furnace is the combustion area in the combustion chamber. There is a large amount of volatile matter in this area. The volatiles burn up a lot of oxygen rapidly and release carbon dioxide and heat. At the primary settlement, the radiation temperature of the reflected arch is higher, and more burnt particles are settled. The hot smoke flow in the whole hot flue gas is under negative pressure, and the flow is smoother. The flow in the furnace is relatively gentle, and the flow velocity and turbulence energy are large at the two turns. After the secondary sedimentation, the temperature gradually decreases and the output hot flue gas is substantially clean.

ANALISIS EFISIENSI KINARJA ECONOMIZER DI PT. PLN (PERSERO) KALIMANTAN SELATAN-TENGAH SEKTOR PLTU ASAM – ASAM

Electrical energy is the dominant energy needed for human life. One source of electricity income is Steam Power Plant (PLTU). With an installed capacity of 4 x65 MW for public transportation, each unit of acid acid plant has one boiler with 1 economizer as a means of boiler efficiency enhancer by absorbing hot flue gas. To avoid it then in need of maximum care to components of economizer. To see the effectiveness of the economizer it is necessary to observe the economizer. This study aims to analyze the effectiveness of the economizer. From the results of the boiler efficiency study from March 27, 2017 to April 10, 2017 with a total average efficiency in the analysis of 81.93%. With the highest efficiency on date On March 29, 2017 the efficiency calculated was 83.42% at 02:00. And the lowest on April 2, 2017, an 80.32% efficiency at 09:00. The factor that influences the efficiency ratio is the temperature difference between the incoming gas gas furnace (T_ (h, i)), exit (T_ (h, o)) and the feed water inlet tube temperature (T_ (c, i)). The research obtained the highest heat transfer coefficient that is equal to 1.647,1 Btu/h.ft2 at 227,4°C on 27/03/2017 and the lowest that is equal to 1.636,91 Btu/h.ft2 at 233°C on 28/03/2017 Keywords: Economizer, Feed Water Tube, Flue Gas, Koefisien Heat Transfer, Heat transfer

Thermodynamic and economic analyses of a hybrid waste-driven CHP–ORC plant with exhaust heat recovery

A smart hybrid power plant comprising a waste-fired CHP (combined heat and power) plant accompanied by a small-scale organic Rankine cycle was recently designed and analyzed thermodynamically. The objective of this hybridization is to maximize the share of electricity production of waste-CHP plants rather than a higher heat production rate in a cost-effective manner. In this work, utilization of the exergy of the hot flue gas of the waste-fired CHP unit in order to increase the potential of the organic Rankine cycle for maximizing the net power output of the hybrid cycle is proposed and techno-economically analyzed. In addition, the effect of using alternative environmentally-friendly organic working fluids on the performance of the system was investigated. The results of the study show that by the flue gas potential utilization of the same CHP unit, the size of the organic Rankine cycle may increase significantly, leading to a larger power output of the plant. As such, the net exergy and energy efficiency values of the combined plant in various operational conditions are improved compared to its primary configuration by, respectively, about 10% and 20%, when both of the main CHP cycle and the organic Rankine cycle are working at nominal load. In addition, this exergy utilization is beneficial economically as well, decreasing the payback period of the parallelization project by about 10% (from 7.4 years to 6.7 years). The alternative organic working fluid does not make a significant change in the technical and economic performance indices of the system.

Ultraviolet Absorption Cross Sections of KOH and KCl for Nonintrusive Species-Specific Quantitative Detection in Hot Flue Gases.

An understanding of potassium chemistry in energy conversion processes supports the development of complex biomass utilization with high efficiency and low pollutant emissions. Potassium exists mainly as potassium hydroxide (KOH), potassium chloride (KCl), and atomic potassium (K) in combustion and related thermochemical processes. We report, for the first time, the measurement of the ultraviolet (UV) absorption cross sections of KOH and KCl at temperatures between 1300 K and 1800 K, using a newly developed method. Using the spectrally resolved UV absorption cross sections, the concentrations of KOH and KCl were measured simultaneously. In addition, we measured the concentrations of atomic K using tunable diode laser absorption spectroscopy, both at 404.4 and 769.9 nm. The 404.4 nm line was utilized to expand the measurement dynamic range to higher concentrations. A constant amount of KCl was seeded into premixed CH4/air flames with equivalence ratios varied from 0.67 to 1.32, and the concentrations of KOH, KCl, and atomic K in the hot flue gas were measured nonintrusively. The results indicate that these techniques can provide comprehensive data for quantitative understanding of the potassium chemistry in biomass combustion/gasification.

Computational Analysis of Heat Transfer Effect on Liquid–Vapor Phase Change and Boiling-Induced Phase Instabilities

Liquid–vapor phase change (boiling/evaporation and condensation) is one of the most important phenomena in thermal management and many other applications of flow and heat transfer. Numerically, it poses challenge due to disparate densities of the phases, resulting in a stiff matrix. The presence of a third phase increases the numerical challenge. In the case of a primary domestic heater, water is heated by hot flue gas in a plate heat exchanger. It is important to avoid boiling of water in this heat exchanger and ensure a steady flow. In the present study, simplified plate heat exchanger geometry is used to predict the flow, heat transfer, and boiling in the heat exchanger in the given condition through CFD. Physically meaningful flow and phase change behavior could be predicted with moderate computational cost. Although it should be a steady process in absence of boiling, the formation of water vapor induces oscillation in the flow. It is observed that dead zones in the heat exchangers initiate local boiling and the vapor is periodically flushed out by the liquid. An oscillatory pattern is observed with a single dominant frequency, which is supported by experimental observations.

Optimal design of heat and water recovery system utilizing waste flue gases for refinery CO2 reduction

Energy efficiency improvement is an effective strategy for CO2 reduction as well as cost savings in the industrial sector. Petroleum refineries generate significant amounts of hot and wet flue gas containing CO2 given their large fuel consumption due to energy intensive processes. In addition, for those locations where the climate is arid, sustainable water supply turns out to be a serious problem to meet the large demand for steam. This paper proposes to synthesize an optimal heat and water recovery system (HWRS) using a superstructure based method to achieve CO2 reduction, cost savings, and water recovery all simultaneously. The water recovery rate is obtained using Aspen Plus® and the HEN is designed by formulating an MINLP problem and solving it using GAMS. As a result, the HWRS could achieve 4.348% CO2 reduction and 28 k$/day of cost savings with 29% lower water demand from the desalination plant.

Optimal coupling of waste and concentrated solar for the constant production of electricity over a year

AbstractIn this article, a biogas‐based Brayton cycle is integrated with a concentrated solar power facility. The gas turbine hot flue gas and the molten salts are used to generate steam for the regenerative Rankine cycle. The process model is solved as a nonlinear optimization problem within a multiperiod scheme to decide on the contribution of the energy resources and the operating conditions of the facility to meet a certain demand of power over a year mitigating the absence of solar availability. The steam turbine is responsible for power production while the gas turbine works mainly as a combustion chamber. In the South of Spain, an excess of biogas is available during summer yielding a production cost of electricity of 0.17 €/kWh with an investment of 380 M€ for a production facility of 25 MW. This plant is not yet economic.

Thermal performance improvement of the three aligned natural draft dry cooling towers by wind breaking walls and flue gas injection under different crosswind conditions

The substantial objective of using circulating cooling water in a typical power plant is to remove the heat effectively from the vapor cycle and to expel it to the environment. One of the most popular cooling systems for this purpose is the natural draft dry cooling tower (NDDCT) which is widely used in regions with the shortage of water, such as Iran. Environmental conditions affect the Heller cooling tower's performance strictly. Temperature, density, and the mass flow rate of sucked air into the cooling towers will all influence their operation. To improve the cooling tower's performance and air suction capability, it is proposed to inject the steam generators' flue gas into the tower. In this study, a single natural draft dry cooling tower incorporating the flue gas duct is modeled to study the effect of flue gas injection on the sucked air flow rate and the radiator heat transfer. Considering the buoyancy effect term, for a 3-D incompressible flow, the Navier Stokes' equations, as well as the energy equation, are solved by computational fluid dynamic method (CFD) to obtain the airflow pattern inside and outside the tower as well as the heat transfer from the radiators. The tower is assumed to be equipped with windbreak walls in one case and without it in another case so that the effect of crosswind could be investigated. Having compared the thermal performance of the towers, the results show that the thermal deficiency is more pronounced for the towers in crosswind without any flue gas injection. It is also shown that the injection of the hot flue gas (with temperature of 130 °C) will increase air intake and the thermal performance of the towers which, in turn, results in the reduction of the outlet water temperature. The modeling is then extended to three aligned NDDCTs to determine the effect of flue gas injection in the presence of windbreak walls under crosswind condition. Consequently, a notable promotion had been observed in all three towers thermal performance but with different ratios.

Farklı Metal (Bakır, Çinko, Kurşun, Kalsiyum ve Mangan) Oksitlerin Sıcak Baca Gazı Kükürt Tutma Aktiviteleri

Bu çalışma, düşük sıcaklıklarda kükürt tutma aktivitesi bilinen beş metal oksitin (CuO, ZnO, PbO, CaO ve MnO) yüksek sıcaklıkta gösterecekleri kükürt giderme performanslarını test etmeyi amaçlamaktadır. Özellikle yüksek kükürt içeren linyitlerin enerji üretimi amacıyla kullanıldığı ülkemizde yüksek kükürt içeriğinin neden olduğu çevresel sorunlar linyit kullanımı için önemli bir sınırlayıcı engeldir. Bu engeli aşmak için önerilen çözümler ise genellikle açığa çıkan sıcak baca gazlarının soğutulması sonrasında kükürtün metal oksit temelli bir adsorbent yardımıyla tutulmasına dayanmaktadır. Yanma prosesine alternatif olan ve temiz kömür teknolojisi olarak bilinen gazlaştırma prosesleri ise sentez gazı (CO ve H2) üzerinden petrol üretimine imkan vermektedir. Kömürün gazlaştırılmasıyla enerji üreten sistemlerde sıcak baca gazlarının soğutulmasının neden olduğu enerji kayıplarını önlemek için, kükürtü sıcak baca gazlarından uzaklaştırmak gerekir. Bu sebeple kükürtün giderimi için kullanılan metal oksitlerin yüksek sıcaklıkta gösterdikleri kükürt giderim aktiviteleri hem çevresel bir sorunu gidermek hem de enerji verimini artırmak adına son derece önemlidir.

Parameter study and optimization on filtration and resistance characteristics of granular bed filter

In this paper, experimental studies were carried out to investigate the filtration and resistance characteristics of a fixed granular bed filter (GBF) during the process of dust particles removal for hot industrial flue gas. The effects of geometric and operating parameters (including filtration superficial velocity, granules size, bed height, dust particles concentration and flue gas temperature) were examined according to the orthogonal array design method. The experimental results show that the filtration superficial velocity has the most significant effect on filtration efficiency, which is followed by granules size, bed height, flue gas temperature and dust particles concentration respectively; for pressure drop, the order of the factors are granules size, filtration superficial velocity, bed height, flue gas temperature and dust particles concentration respectively. Based on the experimental results, correlations of filtration efficiency and pressure drop with these parameters were established, which have good prediction accuracy with most of the deviations within 15%. The optimized parameters combinations of the maximum filtration efficiency and the minimum pressure drop of the GBF were gained which agree well with the experimental results. The correlations are significant for design and evaluation of GBF in practical applications.

Thermal performance analysis and optimization design for LNG submerged combustion vaporizer

Submerged combustion vaporizer (SCV) is an efficient and energy-saving liquefied natural gas (LNG) heat exchange facility, which is developed by multiphase flow heat transfer combined with supercritical fluid heat transfer technology. This paper adopted the computational fluid dynamics (CFD) approach to investigate thermal performance of a real-life SCV with the designed handling capacity of 202 t/h. The numerical results and monitoring industrial data were in good agreement, indicting the feasibility of present method. Results displayed that two typical physical processes, namely, hot flue gas and water flowing across stagger tube bundle wall and supercritical LNG gasification, occurred inside the SCV system. The shell-side heat transfer capacity was mainly affected by the initial water level and volume rate of flue gas. Higher inlet LNG velocity could effectively enhance local tube-side heat transfer coefficient, and the maximum value may depend on the inlet LNG pressure. Furthermore, the Han models could be used to predict the overall thermal performance of SCV with a higher accuracy. Eventually, an optimization design method for SCV system was provided.