Optimal HEN with PHEs for Carbon Dioxide Capture by Amine Absorption Unit at Coal Fired Power Station

The CO2 capture processes are of growing interest to scholars in the struggle against global warming, and for the use of CO2 in the production of clean fuels, chemicals, plastics, and other materials. The post-combustion capture of carbon dioxide from flue gases with monoethanolamine (MEA) Absorption Desorption Unit (ADU) is studied with Process Integration methodology. The optimal structure of the Heat Exchanger Network (HEN) is determined. The study aims to find economically viable options for desorption column parameters by computer modelling and to evaluate the use of novel compact plate heat exchangers (PHEs) with intensified heat transfer. Based on a presented case study, the variation of temperature approach on rich/lean heat exchanger and its influence on heat consumption is discussed. The effect of minimal temperature difference in HEN on the investment cost and its energy efficiency is analyzed. It is shown that the optimal value of minimal temperature difference for HEN with PHEs is 7 °C, which is two times smaller than for HEN based on shell and tube heat exchangers. The use of PHEs in HEN ADU at the same or even smaller purchased cost of heat exchangers saves up to 24 % energy compared to the base case. It is 13 % higher than for the option based on the use of conventional tubular heat exchangers

Using a Neural Network Approach to Predict Deposits on the Surfaces of Heat Exchange Equipment

This work proposes a neural network (NN) approach for predicting the following values: the heat transfer coefficient at the point of interest in the operational period of plate heat exchangers (PHEs), and the time-point to reach the lower allowable limit of the heat transfer coefficient. In this approach, neural network models replace complex mathematical modelling that used systems of differential equations and matrices of heuristic coefficients to calculate the flow rate of deposits on PHE plates, which required the involvement of serious computing resources. Training a feed-forward neural network (FFNN) on a small dataset simulated in the vicinity of reference points obtained by industrial measurements showed the proper coefficient of determination R2 = 0.99 (accuracy) of the short-term prediction forecasts and for operational evaluation of the heat transfer coefficient due to the static type of NN

Modeling residential electricity consumption from public demographic data for sustainable cities

Demographic factors, statistical information, and technological innovation are prominent factors shaping energy transitions in the residential sector. Explaining these energy transitions re-quires combining insights from the disciplines investigating these factors. The existing literature is not consistent in identifying these factors, nor in proposing how they can be combined. In this paper, three contributions are made by combining the key demographic factors of households to estimate household energy consumption. Firstly, a mathematical formula is developed by considering the demographic determinants that influence energy consumption, such as the number of persons per household, median age, occupancy rate, households with children, and number of bedrooms per household. Secondly, a geographical position algorithm is proposed to identify the geographical locations of households. Thirdly, the derived formula is validated by collecting demographic factors of five statistical regions from local government databases, and then compared with the electricity consumption benchmarks provided by the energy regulators. The practical feasibility of the method is demonstrated by comparing the estimated energy consumption values with the electricity consumption benchmarks provided by energy regulators. The comparison results indicate that the error between the benchmark and estimated values for the five different regions is less than 8% (7.37%), proving the efficacy of this method in energy consumption estimation processes

The Estimation of Heat Transfer Area of Plate Heat Exchanger for Condensation of Vapour in the Presence of Noncondensing Gas as a Component of Heat Exchanger Networks

The cooling of gaseous streams that include condensable components is frequently encountered in different industrial applications requiring the use of Heat Exchanger Networks (HENs) for optimal heat recuperation. Plate Heat Exchanger (PHE) with enhanced heat transfer can effectively work with condensation of vapours from a mixture with non-condensable gases. For their integration in HENs, a reliable method for estimation of PHE heat transfer area is required. The description of this method is presented. It is based on the mathematical model of the condensation process in PHE and proposes the approach of estimating minimal PHE heat transfer area that can be achieved by variation of plates size and corrugations geometry. The variables are corrugation inclination angle (varied at 30°, 45° and 60° levels) and corrugation height (varied from 2.5 to 5.5 mm with the step equal to 0.5 mm). The method is illustrated by a case study. Based on this method, the software for estimation of PHE heat transfer area as an element of HEN in condensation of steam from its mixture with air is developed. It can be included in software packages for HEN optimisation as a DLL module

Environmental performance and techno-economic feasibility of different biochar applications: An overview

Biochar has a broad application owning to its physicochemical properties and low cost by origin (by-products or generated from waste). Wide research attention received is the application to the soil as carbon sequestration. In contrast to the efficiency evaluation, the overall cost feasibility and environmental performance of the application still deserves broader analysis and discussion. This study aims to enumerate the advantages, and potential drawbacks of the different applications, in term of cost and the environmental footprints. The other alternatives (e.g. the conventional methods) in achieving the same purpose are compared. Special attention is given to the application of biochar to the soil as carbon sequestration. This study could serve as a guideline in evaluating the pros and cons of biochar application to ensure the unburdening footprints can offset the burdening footprint associated with the generation and other downstream processes towards sustainability

A Novel Temperature vs Pessure drop Grid Diagram for Energy Saving in Heat Exchanger Network Retrofit

Pressure drop in the heat exchanger is a key issue that should be considered in the HEN retrofit, as increasing the pressure of fluid can cost a substantial amount of energy. To accurately estimate the cost-related trade-off factors, the relative cost of pressure drop and heat transfer performance should be determined for each heat exchanger and generally for the whole heat exchanger network. However, there is still lacking a graphical method that can visualise the pressure drop together with a heat exchanger network retrofit. This paper proposes a new Temperature vs Pressure drop (TVPD) Grid Diagram to consider the pressure drops in heat exchangers when retrofitting a heat exchanger network. The method includes the proper design of heat exchangers based on the full utilisation of allowable pressure drop, where several commonly used types of heat exchangers are considered, including shell-and-tube heat exchangers and plate heat exchangers of plate-and-frame and brazed construction commonly used in industry. The new Grid Diagram can be used for energy targeting, visualising the temperature range of different heat exchanger types, and pressure drop. The method provides guidance for engineers to design a heat exchanger network with both considerations on pressure drop and heat recovery

Total site water main concentration selection: A case study

A water main is an interface between water sources and sinks to reduce the complexity of the Total Site Integration for water reuse. The selection of the contaminant concentration of water main can significantly affect the site freshwater use and wastewater generation. This paper proposes a hierarchical approach to the selection of the inter-plant water main concentration for minimising the water utilities. The algorithm first performs Plant- Level Water Integration, exposing to the site level only the residual water sources and sinks. The case study shows that, for the water main inlet concentration increase from 100 ppm to 800 ppm, the minimum freshwater input increases from 127.5 t/h to 133.3 t/h, and the wastewater generation increases from 132.5 to 138.4 t/h. The trend, in this case, can be explained by the fact that the water sinks require cleaner water than the water main can offer. The conclusion is that the selection of the water main contaminant concentration requires balancing the availability from water sources and the demand by water sinks at the site level

Pinch-based targeting methodology for multi-contaminant material recycle/reuse

This work presents a systematic resource targeting procedure in the domain of multiple contaminants water recycling/reuse network. A resource-allocation model was developed and modified to determine the model characteristics, to obtain the optimal solution. By inferring from the formulations, it is recognised that each water sink is constrained by a certain contaminant. This plays a vital role in determining the assignment of sinks to the proper contaminants cascade, classifying them to below or above the Pinch Region, and the source allocation strategy. Multiple Targeting Pinch Diagrams with Source and Sink Composite Curves then should be plotted for each contaminant. Each contaminant is assigned a specific separate Pinch Plot and analysed sequentially until the demands of all sinks are fulfilled. The credibility of the novel approach is demonstrated by several industrial case studies encompassing problems with a fresh and impure resource. The method provides insights into the problem while providing the minimum resource target

Individual Heat Substations Integrated with Heat Pumps for District Heating Systems in Ukraine

Energy systems around the world require a sustainable way for energy supply that does not add carbon to the atmosphere and thus does not enlarge the greenhouse effect, which is seen nowadays as the main cause of climate change. Urban housing consumes the most energy in European countries accounting for up to 43 % of final energy, while 65 % of it is spent on house heating and hot tap water supply. The reduction of carbon dioxide emissions and increasing of energy efficiency of power plants in Ukrainian cities, where district heating systems are centralised, and heat carriers are supplied from central combined heat and power stations based on fossil fuels, can be performed by modifying the existing district heating systems. One of the promising ways is the transition to low-temperature heat carriers from combined heat and power stations, which suppose the use of renewable energy sources, which can be integrated with individual heat substations of houses, and should satisfy the needs of residents in heating and hot water, with the possibility of air conditioning. In the present work, the possible implementation of individual heat substations integrated with heat pumps for low-temperature district heating systems is discussed. The analysis of the possibilities to increase the energy efficiency of the dormitory building with old construction is provided. The method for the design of individual heat substations for heating and hot water supply systems is discussed, including the recommendations for the building renovation

The Influence of Plate Corrugations Geometry on Performance of PHE as Condenser of Steam from its Mixture with Air

The condensation of steam from its mixture with air in channels of plate heat exchanger (PHE) is studied experimentally and with calculations based on a mathematical model developed earlier and based on correlations for local process parameters. The experiments are done for five experimental samples modelling the corrugated field of PHE channel with corrugation angle to the main flow direction 30 degrees, 45 degrees, 60 degrees and channel spacing 5 mm, 7.5 mm and 10 mm. The mathematical model validity is confirmed by comparison of calculated temperature program for cooling of air-stream mixture with experimental data for all five samples. The influence of plates corrugations geometry on overall PHE performance in air-stream condensation and local process parameters distribution is discussed. The analysis reveals that to satisfy the required temperature program, PHE with smaller corrugations angle should have plates of bigger length, as well as PHE with bigger channel spacing. Both these parameters can be used as independent variables in the optimisation of plates corrugations geometry for specified process conditions using examined mathematical model