Modelling of combustion and sorbent reactions in three-dimensional flow environment of a circulating fluidized bed furnace

This thesis presents a three-dimensional, semi-empirical, steady state model for simulating the combustion, gasification, and formation of emissions in circulating fluidized bed (CFB) processes. In a large-scale CFB furnace, the local feeding of fuel, air, and other input materials, as well as the limited mixing rate of different reactants produce inhomogeneous process conditions. To simulate the real conditions, the furnace should be modelled three-dimensionally or the three-dimensional effects should be taken into account. The only available methods for simulating the large CFB furnaces three-dimensionally are semi-empirical models, which apply a relatively coarse calculation mesh and a combination of fundamental conservation equations, theoretical models and empirical correlations. The number of such models is extremely small. The main objective of this work was to achieve a model which can be applied to calculating industrial scale CFB boilers and which can simulate all the essential sub-phenomena: fluid dynamics, reactions, the attrition of particles, and heat transfer. The core of the work was to develop the model frame and the required sub-models for determining the combustion and sorbent reactions. The objective was reached, and the developed model was successfully used for studying various industrial scale CFB boilers combusting different types of fuel. The model for sorbent reactions, which includes the main reactions for calcitic limestones, was applied for studying the new possible phenomena occurring in the oxygen-fired combustion. The presented combustion and sorbent models and principles can be utilized in other model approaches as well, including other empirical and semi-empirical model approaches, and CFD based simulations. The main achievement is the overall model frame which can be utilized for the further development and testing of new sub-models and theories, and for concentrating the knowledge gathered from the experimental work carried out at bench scale, pilot scale and industrial scale apparatus, and from the computational work performed by other modelling methods.

Energy Efficiency of Pumping Medium Consistency Pulp with Centrifugal Pump

Approximately a quarter of electrical power consumption in pulp and paper industry is used in different pumping systems. Therefore, improving pumping system efficiency is a considerable way to reduce energy consumption in different processes. Pumping of wood pulp in different consistencies is common in pulp and paper industry. Earlier, centrifugal pumps were used to pump pulp only at low consistencies, but development of MC technology has made it possible to pump medium consistency pulp. Pulp is a non-Newtonian fluid, which flow characteristics are significantly different than what of water. In this thesis is examined the energy efficiency of pumping medium consistency pulp with centrifugal pump. The factors effecting the pumping of MC pulp are presented and through case study is examined the energy efficiency of pumping in practice. With data obtained from the case study are evaluated the effects of pump rotational speed and pulp consistency on energy efficiency. Additionally, losses caused by control valve and validity of affinity laws in pulp pumping are evaluated. The results of this study can be used for demonstrating the energy consumption of MC pumping processes and finding ways to improve energy efficiency in these processes.

Dieselmoottorisen kaupunkilinja-auton muuttaminen sarjahybridiajoneuvoksi

Tutkimus on pohjustusta Lappeenrannan teknillisen yliopiston Green Campus–hankkeessa tulevaisuudessa mahdollisesti rakennettavalle Cambus–hybridibussille ja siihen liittyvälle muutostyölle. Tässä tutkimuksessa käsitellään asioita, joita kohdataan kun tavallinen dieselkäyttöinen linja–auto muutetaan hybridiajoneuvoksi. Työ sisältää teoriaosuuden, jossa esitellään peruskomponentteja esimerkiksi moottoreiden ja energianvarastointitekniikoiden osalta sekä uusimpia kehityskohteita polttomoottoreiden osalta. Tutkimuksessa on myös vertailtu erilaisia hybridivaihtoehtoja sekä käsitelty mm. tasauspyörästön välityssuhteen ja vaihteiston vaikutusta bussin teoreettiseen suorituskykyyn. Tehdyn tutkimustyön perusteella on hahmoteltu eräs mahdollinen sarjahybridibussin voimansiirtolinja esimerkkikomponentteineen. Tutkimuksessa esitetään myös laskelmia järjestelmän teoreettisesta polttoaineenkulutuksesta jarrutusenergian talteenotto huomioiden perinteiseen kaupunkilinja-autoon verrattuna.

Dieselsähköisen laivan pyörimisnopeussäädettyjen voimansiirtokonseptien mallinnus ja vertailu

Tässä työssä tutkitaan eri voimansiirtokonseptien vaikutusta referenssitapauksen polttomoottorivoimalaitoksen energiatehokkuuteen ja polttoaineenkulutukseen staattisessa tilan-teessa. Referenssitapaukseksi on valittu ulkomerellä toimiva huoltoalus. Työssä esitellään dieselsähköisen laivan voimansiirtokonseptien toteutusvaihtoehtoja ja luodaan katsaus valittuihin generaattoreihin sekä taajuusmuuttajiin. Voimansiirtokonseptien hankintahintaa arvioidaan saatujen hintatietojen ja aikaisempien tutkimusten avulla. Lisäksi konseptien energian- ja polttoaineenkulutusta arvioidaan vuositasolla staattisessa tilanteessa. Perinteiselle kiinteän pyörimisnopeuden toteutukselle löydettiin haastajia sekä konseptien kuluttaman energian, että polttoaineen kannalta tarkasteltuna. Lisäksi työssä muodostetaan referenssialusta vastaava yksinkertainen simulointimalli, jolla voidaan arvioida voimalaitoksen tehohäviöitä sekä polttoaineenkulutusta eri ajotavoilla. Simulointimallilla tutkitaan myös energiavaraston tuomia etuja lisäämällä energiavarasto malliin. Mallia simuloitiin paikoitusajossa ilman energiavarastoa, sekä sen kanssa. Energiavaraston avulla saavutettiin merkittävät polttoainesäästöt.

Simulation of Solid Processes by Aspen Plus

Solid processes are used for obtaining the valuable minerals. Due to their worth, it is obligatory to perform different experiments to determine the different values of these minerals. With the passage of time, it is becoming more difficult to carry out these experiments for each mineral for different characteristics due to high labor costs and consumption of time. Therefore, scientists and engineers have tried to overcome this issue. They made different software to handle this problem. Aspen is one of those software for the calculation of different parameters. Therefore, the aim of this report was to do simulation for solid processes to observe different effect for minerals. Different solid processes like crushing, screening; filtration and crystallization were simulated by Aspen Plus. The simulation results are obtained by using this simulation software and they are described in this thesis. It was noticed that the results were acceptable for all solid processes. Therefore, this software can be used for the designing of crushers by calculating the power consumption of crushers, can design the filter and for the calculation of material balance for all processes.

Combustion properties of biomass residues rich in phosphorus

Tillgången på traditionella biobränslen är begränsad och därför behöver man ta fram nya, tidigare outnyttjade biobränslen för att möta de uppställda CO2 emissionsmålen av EU och det ständigt ökande energibehovet. Under de senare åren har intresset riktats mot termisk energiutvinning ur olika restfraktioner och avfall. Vid produktion av fordonsbränsle ur biomassa är den fasta restprodukten ofta den största procesströmmen i produktionsanläggningen. En riktig hantering av restprodukterna skulle göra produktionen mera lönsam och mer ekologiskt hållbar. Ett alternativ är att genom förbränning producera elektricitet och/eller värme eftersom dessa restprodukter anses som CO2-neutrala. Målsättningen med den här avhandlingen var att studera förbränningsegenskaperna hos några fasta restprodukter som uppstår vid framställning av förnybara fordonsbränslen. De fyra undersökta materialen är rapskaka, palmkärnskaka, torkad drank och stabiliserat rötslam. I studien används ett stort urval av undersökningsmetoder, från laboratorieskala till fullskalig förbränning, för att identifiera de huvudsakliga utmaningarna förknippade med förbränning av restprodukterna i pannor med fluidiserad bäddteknik. Med hjälp av detaljerad bränslekarakterisering kunde restprodukterna konstateras vara en värdefull källa för värme- och elproduktion. Den kemiska sammansättningen av restprodukterna varierar stort jämfört med mera traditionellt använda biobränslen. En gemensam faktor för alla de studerade restprodukterna är en hög fosforhalt. På grund av de låga fosforkoncentrationerna i de traditionella biobränslena har grundämnet hittills inte ansetts spela någon större roll i askkemin. Experimenten visade nu att fosfor inte mera kan försummas då man studerar kemin i förbränningsprocesser, då allt flera fosforrika bränslen tränger in på energimarknaden.

Simulation and optimization of IGCC technique for power generation and hydrogen production by using lignite Thar coal and cotton stalk

The purpose of this study was to simulate and to optimize integrated gasification for combine cycle (IGCC) for power generation and hydrogen (H2) production by using low grade Thar lignite coal and cotton stalk. Lignite coal is abundant of moisture and ash content, the idea of addition of cotton stalk is to increase the mass of combustible material per mass of feed use for the process, to reduce the consumption of coal and to increase the cotton stalk efficiently for IGCC process. Aspen plus software is used to simulate the process with different mass ratios of coal to cotton stalk and for optimization: process efficiencies, net power generation and H2 production etc. are considered while environmental hazard emissions are optimized to acceptance level. With the addition of cotton stalk in feed, process efficiencies started to decline along with the net power production. But for H2 production, it gave positive result at start but after 40% cotton stalk addition, H2 production also started to decline. It also affects negatively on environmental hazard emissions and mass of emissions/ net power production increases linearly with the addition of cotton stalk in feed mixture. In summation with the addition of cotton stalk, overall affects seemed to negative. But the effect is more negative after 40% cotton stalk addition so it is concluded that to get maximum process efficiencies and high production less amount of cotton stalk addition in feed is preferable and the maximum level of addition is estimated to 40%. Gasification temperature should keep lower around 1140 °C and prefer technique for studied feed in IGCC is fluidized bed (ash in dry form) rather than ash slagging gasifier

Technical and economic analysis of replacing artificial lighting system to induction of photoperiod effect in begonia's seedlings in greenhouse

The type of artificial light used for inducing photoperiod effect in begonia's seedlings at greenhouse has fundamental importance in the growth and development of these plants and directly reflects in the electrical energy consumption used in this production process. The objective of this research was to analyze the technical and economic feasibility of replacing the current technology of artificial lighting used by the producers (incandescent lamps), by the technology of discharge lamps with the purpose of inducing photoperiod in a greenhouse. The analysis results indicate that the discharge lamp of 32 W Tubular Fluorescent discharge lamp was the one that presented the lower peak demand and lower average energy consumption of 85.01% compared to incandescent filament lamp of 100 W that is the technology of bigger consumption and currently used by the producer.

Technical evaluation of artificial ligthing systems for broiler houses

The spatial distribution of illuminance and the electric consumption of artificial lighting system is one of the main problems related to broiler production. Therefore, the aim of this study was to evaluate the spatial distribution of luminance level and energy efficiency of different lighting systems for broiler houses. Six types of lamps were tested in two different configurations to find the minimum illuminance of 20 and 5 lux. The tested lamps were incandescent (IL) 100 W, compact fluorescent (CFL) 34 W, mixed (ML) 160 W, sodium vapor (SVL) 70 W, T8 fluorescent tube (T8 FTL) 40 W and T5 fluorescent tube (T5 FTL) 28 W. The first four were evaluated with and without reflective light fixture and the latter two without light fixture. It was observed that the tested system with light fixtures negatively affected the spatial distribution of illuminance inside the house. The systems composed by IL and ML without light fixture led to better results in meeting the minimum illuminance of 20 lux and 5 lux, respectively. T5 FTL presented the lowest energy demand.

Efficiency of water use in sunflower grown in hydroponic system under saline stress

In order to identify alternatives for the use of saline water in agricultural production, the effects of the use of brackish water in the preparation of the nutrient solution for the cultivation of sunflower (cv. EMBRAPA 122-V2000) were studied in hydroponic system on consumption and efficiency of water use for the production of achenes and biomass. A completely randomized design was used, analyzed in a 5x2 factorial scheme with three replications. The factors studied were five levels of salinity of nutrient solution (1.7 - control; 4.3; 6.0; 9.0; and 11.5dS m-1) and two plant densities - one or two plants per vessel. It was concluded that the water consumption of sunflower is a variable sensitive to the salinity of the nutrient solution, especially after the fourth week of crop, and that the efficiency of water use in the production of achenes and biomass of sunflower is greater when the plant density increases from one to two plants per vessel, even under saline stress.

Rational use of water in a poultry slaughterhouse in the state of Paraná, Brazil: a case study

Agroindustries are major consumers of water. However, to adapt to environmental trends and be competitive in the market, they have sought rational use of water through water management in their activities. Cleaner Production can result in economic, environmental and social benefits, and in actions that promote reduction in water consumption. This case study was conducted in a slaughterhouse and poultry cold storage processing plant and aimed to identify points of excessive water consumption, and to propose alternatives for managing water resources by reducing consumption. Consumption data are presented in relation to the processing stages with alternatives proposed for the rational use of water, such as closure of mains water during shift changes. Following the implementation of recommendations, a reduction in water consumption of approximately 11,137 m³ per month was obtained, which equates to a savings of US$ 99,672 per year. From this study, it was concluded that the company under review could develop various improvement actions and make an important contribution to the preservation of water resources in the region where it operates.

Start-up of anaerobic reactors for slaughterhouse wastewater treatment

This study aimed to evaluate the start-up of a horizontal anaerobic fixed bed reactor (HAFBR) followed by an upflow anaerobic sludge blanket (UASB) for the slaughterhouse wastewater treatment. HAFBR was filled with bamboo rings and had 1.2 m in length, 0.10 m in diameter and volume of 7.5 L. The UASB had the volume of 15 L. The HAFBR and UASB operated at organic loading rate and hydraulic retention time average of 8.46 and 3.77 kg m-3 d-1 of COD and 0.53 and 0.98 days, respectively. During 150 days of monitoring system it was found pH 6.8, relatively high values of bicarbonate alkalinity (> 1000 mg L-1) and reduced values of volatile acids (70 to 150 mg L-1), which afforded average removal efficiencies of COD total and total suspended solids of the order of 31 and 23% in HAFBR and 79% and 63% in UASB. It can be concluded that the generation and consumption of bicarbonate alkalinity and total volatile acids, thereby maintaining the pH during the study indicated stable operation of the reactors. The COD removal in the reactors was satisfactory especially when it considers that the assessment was conducted in a period of adaptation of organisms to the effluent and also the high organic load applied during this period.

Ultrafiltration of pulp mill bleaching effluents

Main objective of this research was to find suitable polymeric ultrafiltration membranes with high retentions, good capacities and low fouling tendencies for the E2- and EP-effluent ultrafiltration. Purpose was to treat alkaline bleaching effluents with ultrafiltration in a way that permeates of the filtrations could be recycled back to process and the consumption of fresh water in the pulp mill could be reduced significantly. In the theoretical part of this work the challenges set by the pulp and paper indus-try processes for membranes were examined. An overview of the membrane tech-nology in the pulp industry was also provided. In addition process conditions in the chemical pulp bleaching and properties of bleaching effluents were discussed in literature study. In experimental part the E2- and EP-stage bleaching effluents from Stora Enso Imatra kraft pulp mill were ultrafiltered with CR250- and CR200-filters. Suitable membranes for ultrafiltration were chosen after screening experiments. Concentra-tion experiment was made for the E2-effluent in order to estimate water saving potential. The E2-effluent was finally ultrafiltered in the pulp mill in order to test the feasibility of ultrafiltration in a real industrial environment. Good membrane for the EP-effluent ultrafiltration based on the EP-screening ex-periments was polyethersulfone membrane UP020 with cut-off value of 20 000 Da. Polysulfone membrane UFX05 with cut-off value of 5 000 Da was promising membrane for the ultrafiltration of the E2-effluent. Based on the concentration filtration of the E2-effluent with UFX05 membrane the water saving potential could be 2.2 m3/Adt for the industrial scale ultrafiltration process. Retention re-sults, such as average COD retention of 60 %, from the trial filtration at the pulp mill with UFX05 membrane were modest compared to the screening experiments, where average COD retention was 75 %. Therefore tighter ultrafiltration mem-branes should be tested for the ultrafiltration of the E2-effluent. The UP020 mem-brane seemed to be suitable for the ultrafiltration of the EP-effluent however con-centration and pilot scale ultrafiltration experiments are needed to verify this.

Automatic system identification and optimization of centrifugal pump operation

Centrifugal pumps are a notable end-consumer of electrical energy. Typical application of a centrifugal pump is the filling or emptying of a reservoir tank, where the pump is often operated at a constant speed until the process is completed. Installing a frequency converter to control the motor substitutes the traditional fixed-speed pumping system, allows the optimization of rotational speed profile for the pumping tasks and enables the estimation of rotational speed and shaft torque of an induction motor without any additional measurements from the motor shaft. Utilization of variable-speed operation provides the possibility to decrease the overall energy consumption of the pumping task. The static head of the pumping process may change during the pumping task. In such systems, the minimum rotational speed changes during reservoir filling or emptying, and the minimum energy consumption can’t be achieved with a fixed rotational speed. This thesis presents embedded algorithms to automatically identify, optimize and monitor pumping processes between supply and destination reservoirs, and evaluates the changing static head –based optimization method.

The energy efficiency of chilled beam systems in an office building at different climates

Besides the sustaining of healthy and comfortable indoor climate, the air conditioning system should also achieve for energy efficiency. The target indoor climate can be ob-tained with different systems; this study focuses on comparing the energy efficiency of different air conditioning room unit systems in different climates. The calculations are made with dynamic energy simulation software IDA ICE by comparing the indoor cli-mate and energy consumption of an office building with different systems in different climates. The aim of the study is to compare the energy efficiency of chilled beam systems to other common systems: variable air volume, fan coil and radiant ceiling systems. Besides the annual energy consumption also the sustainability of target indoor climate is compared between the simulations. Another aim is to provide conclusions to be used in the product development of the chilled beam systems’ energy efficiency. The adaptable chilled beam system and the radiant ceiling system prove to be energy efficient independent of the climate. The challenge of reliable comparison is that other systems are not able to reach the target indoor climate as well as the others. The complex calculation environment of the simulation software, made assumptions and excluding of the financial aspects complicate comparing the big picture. The results show that the development of the chilled beam systems should concentrate on energy efficient night heating, flexible demand based ventilation and capacity control and possibilities on integrating the best practices with other systems.