Increase In Boiler Efficiency Research Articles

Combustion Process of Coal–Açai Seed Mixtures in a Circulating Fluidized Bed Boiler

This study investigates the effects of the co-combustion of coal and açai seed in circulating fluidized bed (CFB) boilers, highlighting the increase in thermal efficiency and relevance of a less-polluting source of energy. Using the computer software 1.5D CeSFaMB™® v4.3.0, simulations of the co-combustion process of coal and biomass were carried out in a CFB boiler, obtaining results such as the temperature profile, boiler efficiency and emissions. The work acquired data regarding the equipment in real operational conditions, consisting of the fundamental geometric and operational parameters used in the simulation campaign. The thermal and chemical properties of the fuels were analyzed by carrying out proximate, ultimate, heating value, particle size and specific mass analyses. The model validation was achieved by simulating the boiler in its real operating conditions and comparing the obtained results with the real data; the obtained error was below 10%. Simulations with different fractions of açai seed for energy replacement (10% and 30%) were carried out. As a result, an increase in the average temperature of the bed was observed, highlighting the region immediately above the dense bed. An increase in boiler efficiency was verified from 56% to 85% with 10% açai and to 83% with 30% açai seed. Decreases in SO2 and CO emissions with the insertion of açai were obtained, showing that co-combustion is more complete, while CO2 emissions were increased due to the higher quantity of fuel inserted into the equipment. The fossil CO2 emissions were reduced.

An Overview of the Energy Savings, Utilization, and Emission Reductions of Boilers

Industries and power plants use boilers extensively as a steam generating system. Boilers use a substantial amount of the world's energy supply. Much more fossil fuel can be saved and CO2 emissions can be decreased with even a slight increase in boiler efficiency. This paper outlines the energy consumption of boilers, the methods used to assess their energy efficiency, the losses that have occurred and their reasons, the role that maintenance activities play in preventing heat loss, the quantity of waste energy recovered, and the methods of raising public awareness of energy consumption. On the aforementioned subjects, the most recent published literature has been examined and reported. This includes journal articles, PhD and MSc theses, conference proceedings, reports, and online resources. The high temperature flue gas or boiler exhaust is discovered to be a significant source of energy loss. Also, for a variety of reasons, there are certain other inevitable losses. However, waste heat may be captured and used to provide power, heat, refrigeration effect, and other useful forms of energy utilizing a variety of methods. By doing planned maintenance, one may increase a boiler's efficiency and keep it operating at peak performance. Staff members must regularly participate in education programs and seminars aimed at raising knowledge about energy consumption. As a result, they will be better able to comprehend the significance of the energy utilized in the boiler system and the effects of their activities on it.

ТЕРМО- І АЕРОМОДЕЛІ ЕНЕРГЕТИЧНОГО ОБЛАДНАННЯ ЖИТЛОВИХ КОМПЛЕКСІВ

During accidents or destruction of the infrastructure of residential complexes at low temperatures, it is necessary to restore the operation of heat supply systems in a short time. It is convenient to use gas tube boilers for this. But we need new solutions to the problems of increasing the power and energy efficiency of equipment and systems due to the reduction of resistances to the movement of liquids or gases, as well as the intensification of heat transfer. Numerous studies have shown that an increase in the heat transfer coefficient at the gas-metal wall interface by 2-5 times leads to an increase in energy consumption of boiler fans by 10 times or more. The article uses three research methods to improve the performance of boilers. Visual diagnostics of the movement of liquids and gases made it possible to identify signs of self-organization of the flow structure. Hydraulic studies in slot channels, where only the height h varied in the range h = 0.2-2.5 mm, confirmed that the distribution structure of the pulsation components of the dynamic part of the energy affects the increase or decrease in speed at a given initial pressure. The thermal experiment showed that the flow structure also affects the nature of the change in the heat transfer coefficient. For channel sizes where the pulsation components have positive values, the increase in the heat transfer coefficient is much more intense than for sizes where the pulsations have negative values. That is, visual studies of the flow structure and the correct choice of transverse channel sizes can solve the problem of increasing the flow up to 24% without additional energy costs, as well as eliminate the problem of uncertainty when solving the problem of intensifying heat transfer at the gas-metal wall boundary. Visual studies of the jet in a flooded space provide information for solving the problem of intensifying heat transfer. The use of turbulators in gas-tube boilers ensured an increase in boiler efficiency from к.1 = 0.84 to к.2 = 0.929. At the same time, the energy consumption for fan operation changed slightly. The use of visual diagnostics of the flow structure makes it possible to solve hydraulic and thermal problems when developing or improving energy equipment for housing complexes.

Prediction Modeling of Flue Gas Control for Combustion Efficiency Optimization for Steel Mill Power Plant Boilers Based on Partial Least Squares Regression (PLSR)

The energy-intensive steel industry, which consumes substantial amounts of electricity, meets its power demands through external electricity purchases and self-generation through the operation of its own generators. This study aimed to optimize boiler combustion efficiency and increase power generation output by deriving optimal operational values for O2 and CO within the boiler flue gas using machine learning (ML) with the aim of achieving maximum boiler efficiency. This study focuses on the power-generation boilers at steel mill P in Korea. First, 361 types of operation data from power generation equipment were collected and preprocessed. Subsequently, a partial least squares regression (PLSR) algorithm was used to develop a prediction model for O2 and CO values, known as the Boiler Flue Gas Prediction Model (BFG-PM). The prediction accuracy for O2 was notably high (83.2%), whereas that for CO was lower (53.4%). Nonetheless, the model’s reliability was high because more than 90% of the predicted values were within a 10% error range. Finally, the correlation of the BFG-PM model was applied to the performance test code (PTC) 4.0 for the boiler efficiency calculations formula, deriving the optimal O2 and CO control points. Through a simulation, it was verified that the boiler efficiency was improved by controlling the combustion air. In addition, an average increase in boiler efficiency of 0.29% was confirmed by applying it directly to the generator operating on-site. The results of this study are expected to contribute to annual cost savings, with a reduction of USD 217,000 in electricity purchasing costs and USD 19,700 in greenhouse gas emissions trading expenses.

Efficiency Analysis using Economizer Alternative Energy in Boilers

Efficiency is one of the efforts in implementing energy conservation. Economizers are an alternative source of energy that can survive because of the potential for energy efficiency. Economizer equipment in producing electrical energy and steam produces less than 10-30% fuel needed for a conventional energy plant. The Economizer system that was assumed in this study, there was an increase in boiler efficiency with an Economizer system of 19%. As for the need for burning calories in the combustion chamber with an Economizer system of 46,868,200,68 kcal/hour compared to a system without an Economizer of 61.003.054,86 kcal/hour. Thus the fuel requirement will be less with an Economizer system of 7,735 kg/hour compared to a system without an Economizer of 10.069 kg/hour. So that the results obtained with the same ratio and type of fuel, there is a fuel efficiency of 2.334 kg/hour.

THERMAL ASPECTS OF HEATING BOILER PLANTS OPERATION WITH HEAT-RECOVERY AND EXHAUST GAS RECIRCULATION

The feature analysis of application for heating boiler plants of relatively small heating capacity, which are not equipped with air heaters, of the method of reducing the emission of nitrogen oxides due to decrease the temperature in the boiler furnace by recirculating exhaust gases into the blown air are presented. At the same time, heating gas-consuming boiler plants with traditional heat recovery systems of exhaust gases and implementation of this method with the selection of recycled gases after the boiler and heat-recovery exchanger are considered. The study results for a water-heating boiler with a heating capacity of 2 MW of the change regularities of the combustion temperature in the boiler furnace, the its exhaust gases temperature and water heated in the boiler as well as the boiler efficiency, depending on its relative heat load changed (from 30 to 100%) and with different parts of recirculated gases (from 10 to 20%) in the mixture with the blown air are presented. The studies were performed with and without them recirculation and heat recovery of flue gases. The research results show that the use of waste gas recirculation causes a noticeable decrease (by 150 – 250°C) in the combustion adiabatic temperature and a slight (by 0.5 – 4.7°C) decrease in the boiler waste gases temperature. Recirculation also leads to a decrease in boiler efficiency by 1.3 – 3.1% during the heating period, and the use of the considered heat recovery system of boiler waste gases with heating of return heat-network water by cooling them provides an increase in boiler efficiency by 2.5 – 8.1%. The resulting increase in boiler efficiency with a heat recovery and recirculation system is 0.1–4.8%.

Theoretical Analysis of a Lignite-Fired Power Plant with Pre-Drying System in Terms of Energy Efficiency and Economy

The coals with different initial moisture content to be used in the theoretical analysis were tested according to the related test standards and the results were used in the analysis. In the designed system, waste heat in the flue gas is used as the heat source. The fresh air is heated for drying in the shell-tube heat exchanger by means of flue gas. In fluidized bed dryers, the moisture of the coal was reduced by contacting the raw coal with the drying air. Due to the high initial moisture of the coals used in the theoretical analysis, the pre-drying degree could be at most 0.14 in order that the boiler feeding rate be the same as in the power plant feeding rate without pre-drying system. The system theoretically does not conform to the design parameters and the boiler feed rate is less than the flow rate of power plant without pre-drying system when the pre-drying degree is greater than 0.14. The pre-drying system had ten small capacity dryers working simultaneously to ensure the continuity of the boiler feed. In the study, the theoretical analysis was performed, and thermal performance of the power plant were formulized and graphically presented according to pre-drying degree. Thanks to the pre-drying system, owing to the decrease in the moisture content of the coal, a reduction in the flue gas flow rate and the amount of energy required to evaporate the moisture are realized. As a result, there was a decrease in the boiler losses and an increase in the efficiency of the boiler. The increase in boiler efficiency was 10.74% when coal 1 had been used and it was 7.92% when coal 2 had been used. Since the coals are dried in the same drying system under the same conditions, the moisture of coal 1 decreases more, thus the losses of the boiler decrease more. Due to the increase in the lower heating value and in the boiler efficiency, the efficiency of the power plant with pre-drying could increase by 3.04-4.34%. The coal pre-dried power plant had far more economic performance than a power plant without pre-drying system, since more electricity would be obtained thanks to the increase in efficiency of the plant. The redemption period of the system was determined as 2 years with coal 1 and it was determined as 3 years with coal 2. After the payback periods, the system makes a net profit and brings in an average of 55 million TL extra income per year. In addition, it was observed that when the degree of pre-drying was decreased, economic efficiency of the system also decreased. It is aimed that the study will provide principles of energy efficiency improvement in coal fired power plants with pre-drying system and will guide people who wants to do similar studies.

Effects of the fuel-lean coal/air flow damper opening on combustion, energy conversion and emissions in a supercritical down-fired boiler

In-situ trials were carried out to investigate the effects of the fuel-lean coal/air flow damper opening (FLD) on the pulverized-coal combustion and energy conversion efficiency in a 350-MW supercritical down-fired boiler. This boiler was operated with inferior coal, having a high ash content and low calorific value. The influence of combustion in furnace on steam temperature and coal consumption of a supercritical down-fired boiler were discussed innovatively. The experimental results indicate that, as the FLD was decreased from 100% to 25%, heating of the fuel-rich coal/air flow accelerated such that the overall furnace temperature increased and the thermal load gradually focused at the furnace center area. As a result, the maximum temperature of the water-wall in the lower furnace was reduced and the superheating degree rose significantly. Thus the superheated and reheated steam temperatures increased from 550.4 and 545.8 °C to 558.2 and 555.0 °C. Reducing the FLD also lowered the carbon in the fly ash and slag from 8.17% and 7.70% to 4.51% and 3.43%, respectively. Furthermore, the increase of boiler efficiency and the decrease of specific heat consumption both contributed to the reduction of the specific coal consumption, from 354.45 to 340.43 g·(kW·h)−1, thus the energy conversion efficiency of the unit was improved. However, adjustment of the FLD had only a minimal effect on NOx emissions, which remained in the range of 654–672 mg/m3 at 6% O2. Based on optimizing coal combustion characteristic and economic performance of the unit, an optimal FLD of 25% was recommended.

Exergoenvironmental results of a eucalyptus biomass-fired power plant

Forest biomass has always played an important role in the Brazilian energy mix, with eucalyptus presenting high levels of production and productivity. Due to the high expected potential of this woody biomass, this study assesses this resource for thermal energy production, contributing to the expansion of this sector and to energy transition strategies. This study developed a Life Cycle Assessment (LCA) to quantify the environmental impacts associated with the combustion of eucalyptus. LCA data, which included the procurement of eucalyptus and wood ash treatment, was implemented in exergy and exergoenvironmental analyses, based on the SPecific Exergy COsting (SPECO) approach, for a steam power plant fueled by eucalyptus biomass. Fuel combustion takes into account the formation of pollutants. The high moisture content of biomass affects the overall and boiler exergy efficiencies. The components with worse environmental performance are those with high environmental impact rates associated with exergy destruction (feed water and pump). The environmental impact rate per exergy unit of electricity is 7715 mPt/GJ. A sensitivity analysis verifies the effect of biomass moisture on boiler efficiency and on the specific environmental impact associated with power, concluding that an increase in boiler efficiency increases global efficiency and decreases the specific environmental impact, resulting in a reduction of global exergy destruction.

A novel corner-fired boiler system of improved efficiency and coal flexibility and reduced NOx emissions

To assure stable ignition and combustion of low-volatile coals in conventionally configured boilers, storage systems are commonly used to separate the ground coal from the air or gas and evaporated moisture prior to the combustion process, and the stored ground coal is then transported by hot air to the combustion process. This study is to develop a novel combustion system, in order to facilitate the firing of different types of coals in existing conventional corner-fired boilers originally configured for low-volatile semianthracite-firing and to improve the boiler performance. Numerical simulation, boiler retrofit and full-scale performance test are conducted. After successful demonstration in a 330 MWe semianthracite corner-fired utility boiler, the novel combustion scheme is implemented in retrofit of two other similar boilers. The simulation and full-scale performance test on all the three boilers show that the use of the new combustion system achieves a significant reduction in NOx emissions and a remarkable increase in boiler efficiency whereas induces no side effect in operation. After retrofit, these boilers can also readily accommodate low-volatile semianthracite (the design coal) and high-volatile bituminous coal (the retrofit coal), largely improving the coal flexibility.

Transpired solar collectors in building service engineering: Combined system operation and special applications

One of the easiest ways to integrate renewable sources of energy into the heat producing system of a building is the application of transpired solar collectors. They are widespread in North America, where air heating is a common heating alternative, but they are gaining bigger share in the European solar thermal market nowadays. Their simple construction, maintenance-free operation and high working efficiency result in low capital and operating costs. The combination of TSC with other system elements results in additional benefits. Preheating the combustion air of large-scale boilers results in the increase of boiler efficiency and thus the reduction of natural gas consumption and CO2 emission. Whether to choose TSC or heat recovery unit for a certain air conditioning system has to be investigated by examining efficiency-influencing factors of both systems. Besides solar air heating, transpired solar air collectors can reduce the cooling demand on a building. Roof ventilation and nocturnal radiant cooling are two alternatives, which are being presented in the current paper.

Improvement of Boiler's Efficiency Using Heat Recovery and Automatic Combustion Control System

This research was conducted to improve the efficiency of a fire tube boiler with a fixed gate and screw conveyor for feeding fuel. The efficiency improvement was based on the use of flue gas heat for fuel drying, air preheating before combustion, and controlling amount of air for fuel combustion before entering the combustion chamber using the fuzzy logic control algorithm. The experimental result indicates that using heat recovery and fuel drying reduces 3%wt of fuel moisture content and boiler efficiency increases 0.41%. Preheating air means a 35°C increase of temperature or a 0.72% increase of boiler efficiency. The average accuracy of air control is 89.15%, indicating a 4.34% increase of boiler efficiency. If the three systems are operated simultaneously, 5.15% increase of boiler efficiency will be achieved or 246.88 tons/year saving of fuel.

Boiler Retrofit for the Utilization of Biodiesel

Fuel oil used in the boiler is able to substitute with biodiesel. In lower blends, there are no engine modification needed, but some researchers recommended some technical adjustments in order to maintain the boiler's performance and equipment durability. This study consists of the comparison between the performance of boiler before and after retrofitting on the use of biodiesel. The diesel oil was introduced in biodiesel blends of 10% (B10), 20% (B20) and 25% (B25). A fire tube boiler was used for the test with pressure of 3 bar and heat input capacity of 60,000 kcal. The boiler retrofit is conducted by fine tuning the fan damper scale (FDS) and adding a heating feature on fuel system. It was specifically intended to maintain the quality of combustion and boiler efficiency as well as to avoid an increase in fuel consumption. The combustion behaviour was monitored by exhaust emissions of CO, NOx, and SO 2 . The fan damper scale (FDS) and fuel temperature is adjusted by the increasing portion of biodiesel used. The fuel heating apparatus was set at temperature of 40 o C for the use of B10, and 60 o C for B20 and B25. The FDS adjustment was successfully resulted a reduction in rate of combustion air by average of 9.2%. The boiler retrofitting for the utilization of B10, B20 and B25 showed an increase in boiler efficiency by 0.64%, 0.42% and 2.6% respectively. The boiler retrofitting is surprisingly reduced the fuel consumption by average of 11.2%.

Use of Fuzzy Logic to Control Air Intake for Increase in Boiler Efficiency

This paper presents a study and investigation of an improvement of boiler efficiency with an automatic control of air quantity into a combustion chamber. A fire tube boiler with a fixed gate and screw conveyor for feeding fuel was used to test the automatic control system, and a sub-bituminous was used as a fuel for this study. The increase in boiler efficiency was based on controlling amount of air quantity for fuel combustion before entering to the combustion chamber using fuzzy logic control algorithm. Automatic combustion control was achieved by measuring the amount of Oxygen gas (O2) from flue gas stack. From the experimental results, it was indicated that the automatic control system can control the average amount of O2 in flue gas at 11.09% when the O2 in the flue gas was set at 10%. The boiler efficiency was increased by 4.34%, and the energy consumption was reduced to have a fuel saving of 195.88 ton/year.

Asymmetric combustion characteristics and NO x emissions of a down-fired 300 MW e utility boiler at different boiler loads

To investigate the aerodynamic field, cold airflow experiments were conducted under different boiler loads in a cold small-scale model of a down-fired pulverized-coal 300 MW e utility boiler. At 300 MW e and 250 MW e loads, a deflected flow field appeared in the lower furnace. In contrast, at a 150 MW e load, a U-shaped flow field appeared in regions near the left- and right-side walls in the lower furnace. Concurrently, the regions near the two wing walls adjacent to the front arch had received deflected upward airflow emanating from the region near the rear wall. Moreover, a symmetric W-shaped flow field appeared in the central regions below the front and rear arches. Industrial-sized experiments on the full-scale furnace were also performed at different loads with measurements taken of gas temperatures in the burner region and near the right-side wall, as well as heat fluxes and gas components in the near-wall region. Asymmetric combustion appeared at 300 MW e and 250 MW e loads, with large differences arising in gas temperatures, gas components, and heat fluxes between zones near the front and rear walls. At 150 MW e load, gas temperatures, gas components and heat fluxes are, in general, symmetrically distributed throughout the furnace. By decreasing the load, differences in gas temperatures, gas components, and heat fluxes near the front and rear walls decrease, as did NO x emissions. Meanwhile, the carbon content in fly ash essentially decreased, yielding an increase in boiler efficiency assisted by a drop in exhaust gas temperature.

Energy Efficiency Improvement Strategies for Industrial Boilers: A Case Study

In this paper, the findings of boiler house efficiency improvement study carried out in a large boiler house unit of a pulp and paper mill has been presented. The causes of poor boiler efficiency were various heat losses such as loss due to unburnt carbon in refuse, loss due to dry flue gas, loss due to moisture in fuel, loss due to radiation, loss due to blow down, and loss due to burning hydrogen, etc. The various heat losses were analyzed and a set of recommendations were made to the plant management for implementation, so that efficiency of boiler can be increased. Five important recommendations were implemented by plant management, and it has been seen that there is tremendous increase in boiler efficiency. Economic analysis reveals that the expenditure on the proposed system will be recovered in a short span of time. This work, with only five recommendations implemented, has resulted in net increase of 2% in overall boiler efficiency and an annual saving of Rs. 34,12,395. In addition, it is observed that carefulness in the operation of boiler can help a great deal in energy efficiency improvement in boiler.

Influence of Staged-Air on Airflow, Combustion Characteristics and NOx Emissions of a Down-Fired Pulverized-Coal 300 MWe Utility Boiler with Direct Flow Split Burners

Cold airflow experiments were conducted to investigate the aerodynamic field in a small-scale furnace of a down-fired pulverized-coal 300 MW(e) utility boiler arranged with direct flow split burners enriched by cyclones. By increasing the staged-air ratio, a deflected flow field appeared in the lower furnace; larger staged-air ratios produced larger deflections. Industrial-sized experiments on a full-scale boiler were also performed at different staged-air damper openings with measurements taken of gas temperatures in the burner region and near the right-side wall, wall heat fluxes, and gas components (O(2), CO, and NO(x)) in the near-wall region. Combustion was unstable at staged-air damper openings below 30%. For openings of 30% and 40%, late ignition of the pulverized coal developed and large differences arose in gas temperatures and heat fluxes between the regions near the front and rear walls. In conjunction, carbon content in the fly ash was high and boiler efficiency was low with high NO(x) emission above 1200 mg/m(3) (at 6% O(2) dry). For fully open dampers, differences in gas temperatures and heat fluxes, carbon in fly ash and NO(x) emission decreased yielding an increase in boiler efficiency. The optimal setting is fully open staged-air dampers.

00/03551 Numerical simulation of the combustion processes in a W-shaped boiler furnace under different operating conditions

In-situ trials were carried out to investigate the effects of the fuel-lean coal/air flow damper opening (FLD) on the pulverized-coal combustion and energy conversion efficiency in a 350-MW supercritical down-fired boiler. This boiler was operated with inferior coal, having a high ash content and low calorific value. The influence of combustion in furnace on steam temperature and coal consumption of a supercritical down-fired boiler were discussed innovatively. The experimental results indicate that, as the FLD was decreased from 100% to 25%, heating of the fuel-rich coal/air flow accelerated such that the overall furnace temperature increased and the thermal load gradually focused at the furnace center area. As a result, the maximum temperature of the water-wall in the lower furnace was reduced and the superheating degree rose significantly. Thus the superheated and reheated steam temperatures increased from 550.4 and 545.8 °C to 558.2 and 555.0 °C. Reducing the FLD also lowered the carbon in the fly ash and slag from 8.17% and 7.70% to 4.51% and 3.43%, respectively. Furthermore, the increase of boiler efficiency and the decrease of specific heat consumption both contributed to the reduction of the specific coal consumption, from 354.45 to 340.43 g·(kW·h)−1, thus the energy conversion efficiency of the unit was improved. However, adjustment of the FLD had only a minimal effect on NOx emissions, which remained in the range of 654–672 mg/m3 at 6% O2. Based on optimizing coal combustion characteristic and economic performance of the unit, an optimal FLD of 25% was recommended.

Field testing of boiler economy devices

A number of commercially promoted boiler economy devices have been tested for their effect on the operation of a twin boiler system in a working primary school. Both boiler efficiency and site gas usage were measured. It was found that most of the devices had no effect on either aspect of performance. The only device to produce measurable reductions in gas usage and an increase in boiler efficiency appeared to achieve this by effecting unacceptable reductions in average boiler temperature.