Cooling Water Consumption Research Articles

Process simulation, optimization and assessment of post-combustion carbon dioxide capture with piperazine-activated blended absorbents

High efficiency, large capacity, and low energy consumption have become an important challenge in performances of post-combustion carbon dioxide (CO2) capture and regeneration. Blended absorbents have shown great potential but their process simulation, modeling, and optimization have not been known definitively. This work developed the blended aqueous absorbents based on piperazine (PZ) activators: PZ-activated methyldiethanolamine (MDEA), potassium carbonate solution (K2CO3), and aqueous ammonia (NH3.H2O) to improve their techno-economic performances. The whole process simulation was conducted using a validated rate-based model under given a CO2 capture efficiency of 85%. In this process, the key factors including the molar concentration of the absorbent, PZ molar ratio, CO2 load of lean liquid, lean-liquid temperature, flue-gas temperature, and rich-liquid temperature, were employed for the design of experiment using response surface methodology. A series of nonlinear regression equations were developed using the flow rate of absorbents, the reboiler heat duty (in the units of gigajoules per ton of CO2), and the cooling-water flow rate as the multi-objective function. Subsequently, the optimal Pareto solution set and compromise solutions were determined using the multi-objective genetic algorithm and finally, their performances were assessed using the fuzzy close-degree algorithm. It was found that the optimal operating parameters can be determined effectively according to the proposed approach. For each PZ-activated blended absorbents, the trade-off effect exists between absorbent flow rate, reboiler heat duty, and cooling water consumption. The absorbents having optimal techno-economic performance were recommended to be PZ-activated MDEA, followed by PZ-activated K2CO3 and PZ-activated NH3.H2O when considering the regeneration energy consumption. The results may provide a positive reference for process design and optimization of the industrial post-combustion CO2 capture system.

Control of heat exchangers in series using neural network predictive controllers

Abstract The paper reveals three applications of neural network predictive control (NNPC) to a system of four heat exchangers (HEs) in series with counterflow configuration to save energy expressed by cooling water in the system of HEs cooling the distillation product. Neural networks (NNs) are used at first in conventional NNPC and subsequently, neural network predictive controllers (NNPCLs) are employed as a master controller in a cascade control, and as a feedback controller in the control system with disturbance measurement. Neural-network-predictive-control-based (NNPC-based) feedback control systems are compared with PI controller based feedback control loop. Series of simulation experiments were done and the results showed that using NNPC-based cascade control reduced cooling water consumption. This control system also significantly reduced the settling time and overshoots in the control responses and provided the best assessed integral quality criteria compared to other control systems. NNPC-based cascade control can also be interesting for industrial use. Generally, simulation results proved that NNPC-based control systems are promising means for the improvement of HEs control and achievement of energy saving.

Seasonal Risk Assessment of Water-Electricity Nexus Systems under Water Consumption Policy Constraint.

Previous studies have estimated power plant cooling water consumption based on the long-term average cooling water consumption intensity (WI: water consumption per unit of electricity generation) at an annual scale. However, the impacts of the seasonality of WI and streamflow on electricity generation are less well understood. In this study, a risk assessment method is developed to explore the seasonal risk of water-electricity nexus based on the Integrated Environmental Control Model, which can simulate variable WIs in response to daily weather conditions and avoid underestimation in WIs as well as nexus risk during dry seasons. Three indicators, reliability, maximum time to recovery, and total power generation loss, are proposed to quantify the seasonal nexus risk under water consumption policy constraint represented by the allowed maximum percentage of water consumption to streamflow. The applications of the method in two representative watersheds demonstrate that the nexus risk is highly seasonal and is greatly impacted by the seasonal variability of streamflow rather than annual average water resources conditions on which most previous studies are based. The nexus is found more risky in the watershed with almost double mean annual streamflow and greater streamflow variability, compared with the watershed with less streamflow variability.

Computational experiment on determination of load on the rollers of continuous casting machine

The article is devoted to calculations of load on rollers of a curvilinear continuous casting machine during bending of the ingot in the levelling section. The calculation takes into account the elastic and plastic characteristics of metal and the flexibility of the roller apparatus. Determination of load on rollers together with meeting other requirements such as reducing the cooling water consumption, minimizing the energy consumption enables optimizing the technology of slab cooling in the secondary cooling zone (SCZ) and obtaining metal of the required quality.

Experimental study on the influence of the saline concentration in the electrical performance of a Hygroscopic cycle

The Hygroscopic cycle is a novel proprietary power cycle characterized by working with hygroscopic compounds which optimize the condensation of the turbine output steam in a steam absorber. This technology can be incorporated in any power plant that uses a Rankine cycle, obtaining higher electrical efficiency without limiting the cold sink temperature and without cooling water consumption. The novelty of this article is that Hygroscopic cycle is experimentally investigated in a test power plant with high concentrations of lithium bromide solution in water in the cooling reflux to analyze the effect on condensing temperature, condensing pressure, power output and efficiency. Mass concentration of lithium bromide in the cooling reflux stream ranges from 45 to 65%. The increase in salt concentration at the cooling reflux stream allows the condensing temperatures to be significantly increased by more than 15 °C in a Hygroscopic cycle with respect to a Rankine cycle. Results also show that it is possible to decrease the turbine outlet condensing pressures for the same condensing temperature. Thereby, as mass concentration of lithium bromide is increased the gross electric power output increases with reference to a Rankine cycle for the same condensing temperature. The minimum increments in net electric power output and electrical efficiency are 7.6% and 2.6% respectively.

A water-electricity nexus model to analyze thermoelectricity supply reliability under environmental regulations and economic penalties during drought events

A reliable thermoelectricity supply system requires available cooling water. Recent electricity supply failures that have occurred all over the world during drought events indicate that the thermoelectricity system is vulnerable. However, knowledge and policy gaps remain regarding water-electricity interactions at the watershed scale. In this study, a water-electricity nexus model is developed to facilitate electricity generation decisions and environmental policy designs involving cooling water consumption and temperature controls. This nexus model consists of three modules, a physically based hydrologic module, a decentralized optimization module, and a thermoelectricity generation module, which are closely integrated at the daily time step. The model is used to quantify tradeoffs between environmental impacts and potential electricity supplies at the power plant and watershed levels. A case study is conducted to demonstrate the model application for a watershed-wide, coordinated water-energy policy design under different combinations of environmental regulations and economic penalties during a drought event.

Influence of cooling temperature increase in a hygroscopic cycle on the performance of the cooling equipment

Power output of power plant is substantially reduced when cooling is conducted at high ambient temperatures. The problem is also intensified at locations with water scarcity. Hygroscopic cycle is a novel technology that improves Rankine cycle and solve those problems in an effective way. Hygroscopic Cycle Technology works with hygroscopic compounds that increase the cooling temperature for each output pressure of the steam turbine and uses dry coolers for refrigeration. As a result, much better cooling conditions are obtained and water consumption is avoided. Higher electrical performance is obtained without the limitation of high ambient temperatures. In this paper, Hygroscopic Cycle is experimentally studied. Results have been obtained in a test plant with a live steam generation capacity of 110 kg/h. This article shows cooling temperatures increase obtained for high mass concentrations from 45 to 65% of lithium bromide solution in water at the cooling reflux stream. The increase of the saline concentration in the cooling reflux significantly increase the cooling temperatures by more than 15 °C in a Hygroscopic cycle with respect to a Rankine cycle, for the same condensing pressure. Consequently, it reduces the electrical power required by the chosen cooling system, as well as to save all the cooling water consumption needed for cooling towers in other installations. Hygroscopic Cycle with high concentrations is able to increase up to 17.41% the net electrical power output respect to Rankine cycle.

Analysis of the effect of seasonal climate changes on cooling tower efficiency, and strategies for reducing cooling tower power consumption

Cooling towers are widely used in chemical industries to cool water with ambient air that is susceptible to weather changes not only during the day, but also during the year, resulting in challenges to cooling towers design and operation. In the design phase, the difficulties to determine the cooling tower capacity arise not only from the uncertainty of cooling water consumption but also from ambient temperature variations, which have a direct impact on the volume of cooling tower fill and fan power. Wide temperature variations can result in cooling towers that excessively cool water during significant portion of the year. Moreover, an oversized cooling tower brings challenges to the plant operation, since the cooling tower turndown must be high to account for the colder days. The mathematical model of cooling tower operation that is composed by mass and energy balances, and by cooling tower characteristic equations can be simulated to design cooling towers, and forecast their performances in four Brazilian cities (Manaus, Salvador, São Paulo and Porto Alegre). Analyzing the results enables the calculation of the cooling tower slack, and the required turndown during the year in these four cities. This work proposes strategies for cooling tower fan operation to reduce the slack, and estimates the electrical energy cost reduction if such strategies are implemented.

Analyzing the economic value of thermal power plant cooling water consumption

Abstract The consumption of water by thermal power plants for cooling purposes has presented several policy and resource allocation challenges in the recent past. There is need for improved economic understanding of thermal power plant water consumption to better address these challenges. In this paper, we examine the economic efficiency of water consumption substitutes for existing thermal power plants. In the long run, a power plant could reduce water consumption by investing in efficiency improvements. In the short run, a power plant could reduce water consumption by curtailing power output. The analysis presented in this paper demonstrates that these substitutes are not economically efficient; water prices in excess of $1.00/m3 would be required for power plants to make efficiency investments or curtail output. Thermal power plants are therefore not attractive targets for water consumption reduction initiatives based on pricing alone. Furthermore, in the long run, efficiency improvements only show significant water reduction potential for the most inefficient plants. However, the findings of the short run analysis indicate that since thermal power plants are willing to pay water prices in excess of $1.00/m3 before curtailing output, these power plants do not require free reallocation of water from senior water rights holders during periods of scarcity, as has been the practice in several regions. Instead, a more efficient water policy focus would be creation of enabling environments for water market transactions. Such water market transactions could help balance competing water demands during periods of scarcity, while maintaining reliable electricity supply.

Integration of thermo-vapor compressors with phenol and ammonia recovery process for coal gasification wastewater treatment system

Current phenol and ammonia treatment process consumes a large amount of hot utilities to recover crude phenol and aqua ammonia, which includes 0.5 MPag steam (2.68 MW), 1.0 MPag steam (10.17 MW), and 2.5 MPag steam (1.97 MW) based on the benchmark treatment capacity of 100 t/h. This paper fixates on the further improvement of energy efficiency by process integration and innovation. A novel integrated process is proposed in this paper to abate utilities consumption. Two scenarios have been analyzed following the Grand Composite Curve. The results show that one of the new integrated processes performs better energy saving efficiency. It requires 53.7% (7.96 MWsteam) less hot utility consumption and 57.5% (6.86 MWcw) less cooling water consumption at the expense of 68.7% (662 kWelec) more electricity use, as suggested in simulation results. The estimated cost savings relevant to the improved process is 1.095 million US$/y, and the emission reduction is 5237 t CO2 e/y.

Assessing the impact of drought on the emissions- and water-intensity of California's transitioning power sector

This study investigates how technological transitions across California's power sector have shifted its state-level carbon dioxide emissions and cooling water consumption intensities. Its ultimate goal is to evaluate how the state's climate mitigation and environmental policies have affected the power sector's vulnerability to extreme drought and how extreme drought has affected progress towards the state's climate mitigation priorities. The study analyzes the period spanning 2010–2016, which includes one of the state's most severe droughts on record. The results indicate that the growth of variable renewable energy generation has helped offset some of the negative consequences of drought, which include increased emissions and cooling water usage by natural gas generators during periods of low hydropower. However, the retirement of the San Onofre nuclear power plant has delayed the overall decarbonization of the state's power sector, and the closure of significant coastal power plant capacity could increase the freshwater consumption of the power sector if replacement capacity is not cooled with alternative cooling water sources or dry cooling systems. The noted tradeoffs between greenhouse gas mitigation priorities, freshwater dependency, and vulnerability to climatic events highlight the importance of holistic decision making as regional power grids transition to cleaner generation sources.

A novel building material with low thermal conductivity: Rapid synthesis of foam concrete reinforced silica aerogel and energy performance simulation

With the increasing number of commercial buildings in the United States, the energy consumption for space air conditioning is continuously rising. Considering the external building envelope an important role to generate cooling and heating loads, we developed a new high performance building material for building envelope application. Hence, a novel foam concrete reinforced SiO2 aerogel (FC-SA) material was synthesized via sol-gel technique, vacuum impregnation method and rapid supercritical drying process. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric / differential scanning calorimetry (TG-DSC), N2 adsorption-desorption test (BET) and transient plane source method (TPS). The prepared composite had a high degree of aerogel filling (74% volume of matrix) and the aerogel component still maintained a porous nanostructure. Besides, FC-SA showed a large specific surface area of 405.3 m2/g and high pore volume of 1.28 cm3/g. Meanwhile, the introduction of aerogel has little effect on the mechanical strength of the matrix material. According to the test results, the thermal insulation performance of foam concrete has been found greatly improved with silica aerogel composition. The thermal conductivity of FC-SA composite was measured as low as 0.049 W m−1 K−1 at room temperature (30 °C), which was a 48.4% decrease from foam concrete. Finally, the energy saving simulation results showed that in cold and hot areas, the use of FC-SA to replace traditional concrete materials can greatly reduce both of energy consumption and cooling water consumption.

Challenges in predicting steam-side pressure drop and heat transfer in air-cooled power plant condensers

Conventional power plant condensers operate at unsustainably high cooling water consumption rates (2–28 m3 MW h−1). Dry air-cooled condensers (ACCs) can enable reduced water consumption in power plants. However, ACCs are rarely employed because of the substantial decreases in condenser performance and power plant efficiencies compared to wet-cooled systems. ACC studies typically focus on air-side transport, assuming that the effects of steam-side pressure drop and thermal resistance are small. The objective of the present investigation is to scrutinize this assumption – quantifying the influence of steam-side effects on ACC operation. A detailed model of a representative ACC is formulated. Model results demonstrate that condensation heat transfer and pressure drop are poorly characterized at ACC operating conditions. Predicted power plant efficiency varies by 0.7% with different condensation heat transfer models. Additionally, predicted plant efficiencies vary depending on which pressure drop correlation is employed. The differences are exacerbated at low steam saturation pressures (∼4 kPa), where the cycle efficiencies range from 36.0% and 37.7% between different pressure drop correlations. Results from this study indicate that both steam side and air-side effects must be considered to improve ACC performance. Some methods for enhancing in-tube condensation are mentioned, and future ACC research needs are discussed.

Advantages of incorporating Hygroscopic Cycle Technology to a 12.5-MW biomass power plant

This article focuses on the advantages found by incorporating Hygroscopic Cycle Technology into the 12.5-MWe “Vetejar” biomass power plant operating in the province of Córdoba (Spain) since 1996. The power plant required upgrades to increase its availability, net electrical performance and to extend the service life span of refrigeration equipment. The incorporation of the new Hygroscopic Cycle Technology has allowed not only to alleviate the shortcomings of the power station in a simple way, but also to make the most of the existing equipment, despite the adverse environmental conditions. The scarcity of water in the area is one of the greatest difficulties the plant has met since its start-up. It significantly diminishes the operation hours of the plant, reducing the electrical power generated, electrical performance and availability. The incorporation of this novel technology to the existing plant has allowed the cooling temperature to increase by 13 °C while maintaining the same condensing pressure. As a result, significant net increase in electrical efficiency, reduction of auto-consumption and cut down on annual cooling water consumption were obtained.

The Feasibility on the Case that the Air Conditioning Condensate Water is used as the Make-up Water of Cooling Tower

The cooling water consumption accounts for 80% of total industrial water consumption. The cooling water need be used more reasonably, while waste of water resources may be reduced by minimizing water losses and recycling these resources. It is hard to collect condensate due to the low yield, but there are major advantages. An integrated service building of Beijing is employed as the example, condensate yield and water-saving amount are calculated according to central air conditioning systems and fan coil units. In addition, the feasibility of supplying condensate from air conditioners to cooling towers is comprehensively analyzed based on construction budgets. Results suggest that it is energy-efficient and feasible to recycle and reuse the condensate, which is a by-product of central air-conditioners.

Parametric modeling approach for economic and environmental life cycle assessment of medium-duty truck electrification

Using a parametric modeling approach, we evaluate economic and environmental life cycle trade-offs of medium-duty electric trucks in comparison with nine non-electric technologies (e.g., conventional diesel, biodiesel, compressed natural gas, etc.) for U.S. model year 2015. Life cycle results for electric trucks vary strongly with weighted positive kinetic energy, whereas those for non-electric trucks vary the most with average trip speed. Our parametric life cycle assessment models explain 91%–98% of the variability in life cycle inventory and impact assessment results, revealing “how” and “why” the trade-offs of truck electrification change with different input conditions.In terms of cost, whether total cost of ownership or also including health and climate impact costs, model year 2015 battery electric trucks in severe applications such as urban driving provide positive and robust net benefits in many areas of the U.S. However, for typical operations, petroleum diesel with idle reduction or hybrid-electric technology provide the largest overall life cycle cost benefit.Battery electric, idle reduction, and hybrid trucks emit lower life cycle greenhouse gas emissions across the board in comparison with the other technologies. Despite lower carbon-intensity, electric trucks tend to be water-intensive because of cooling water consumption for thermo-electric power plants. Hybrid trucks create higher NOx emissions and thus larger associated environmental impacts. Idle reduction is beneficial to urban-type applications. Compressed natural gas trucks are the least water-intensive but may not reduce greenhouse gas emissions. Using marginal rather than average factors for electric grid emissions calculations doesn't change the overall life cycle comparisons. Improving driving behavior has universally positive effects for which the exact magnitude and sensitivity depend on environmental impact indicators and technologies.

Methodology for the optimal design of an integrated first and second generation ethanol production plant combined with power cogeneration

The application of methodologies for the optimal design of integrated processes has seen increased interest in literature. This article builds on previous works and applies a systematic methodology to an integrated first and second generation ethanol production plant with power cogeneration. The methodology breaks into process simulation, heat integration, thermo-economic evaluation, exergy efficiency vs. capital costs, multi-variable, evolutionary optimization, and process selection via profitability maximization. Optimization generated Pareto solutions with exergy efficiency ranging between 39.2% and 44.4% and capital costs from 210M$ to 390M$. The Net Present Value was positive for only two scenarios and for low efficiency, low hydrolysis points. The minimum cellulosic ethanol selling price was sought to obtain a maximum NPV of zero for high efficiency, high hydrolysis alternatives. The obtained optimal configuration presented maximum exergy efficiency, hydrolyzed bagasse fraction, capital costs and ethanol production rate, and minimum cooling water consumption and power production rate.

Effect of heat preservation for the heating- pipe between the kettles of double- kettle distiller on volatile compounds of cherry brandy and the distillation characters

Heat preservation was processed to the heating- pipe between the kettles of double- kettle distiller. The difference of components and contents of volatile compounds in raw cherry brandy were studied. The power and cooling water consumption,efficiency of the distiller were calculated. The results showed that β- Damascenone,geraniol,1- Decanol and some ethyl esters in especially ethyl hexanoate and ethyl decanoate were increased,while furfural and benzaldehyde were decreased and total amount of carbonyl compounds were also reduced after reformation.Sensory analysis resulted that the aroma of cherry fruit,flower and sweet flavor was much better after heat preservation. The power and cooling water consumption were decreased while efficiency was increased. The modification had no significant effect on the content of methanol.

Water recycling and reuse in soft drink/beverage industry: A case study for sustainable industrial water management in Turkey

The aim of this study was to investigate water conservation and reuse opportunities in a soft drink/beverage manufacturing company. Water use analysis and benchmarking were carried out to determine the areas and processes where significant water saving potential is present. Based on evaluations, water recycling and reuse practices were realized in cooling systems. As a result of applying these practices, the total specific cooling water demand of the company was reduced from 14.4 to 1.2m3/m3 product or by 91.8%. Moreover, the total specific water intensity of the company was decreased 55.0%. Thus, the achieved total annual water saving was 503,893m3. After applications, specific wastewater generation of the company was reduced by 57.4% and hydraulic overload issues in wastewater treatment plant of Kayseri organized industrial zone were resolved. During the implementation of water saving measures/techniques 56,960$ was spent for equipments. Annual cost saving of the company were 97,000$. So, the payback period of the implementations was approximately 7 months. This study proved that water recycling and reuse can successfully be implemented in soft drink/beverage industry as a sustainable industrial water management approach. If successfully replicated in other manufacturing sectors besides soft drink/beverage sector, outcomes of this study can be a solution for excessive cooling water consumption in Turkey as well as other parts of the world where similar processes are employed.

Reducing water and energy consumption in chemical industry by sustainable production approach: a pilot study for polyethylene terephthalate production

In this study, a polyethylene terephthalate manufacturing plant was subjected to environmental performance evaluation and analyses/benchmarking of water consumption. The objective was to determine processes/practices where significant water and related energy saving potential was present. Based on evaluations and analyses, a technology change was realized in heat transfer systems from water-to air-cooled process. As a result of the applications, soft cooling water consumption of the company was reduced by 46.7% which corresponds to water saving of 151,428 m3/year. Moreover, 117,848 kWh/year of energy was saved due to electricity saving in electric motors of pumps of heat transfer systems as well as pumps/fans of cooling towers. Owing to the improved energy efficiency, total carbon emissions of the company was reduced by 69,530 kg CO2/year. Auxiliary material consumption was also reduced since the maintenance requirements of heat transfer pumps were minimized. The total cost saving was 104,905 $/year, while the payback period was calculated as 6 months. This study was conducted to be used as a successful model to increased water and energy efficiency in manufacturing industries based on systematic environmental performance evaluations and benchmarking. Furthermore, it could serve as a building block in Turkey for the integration of cleaner and sustainable production approach into national agenda which is currently being structured by the European Union harmonization efforts of this country.