Fig 3 - uploaded by Nassim Tahouni
Content may be subject to copyright.
Source publication
The aim of this work is to perform a retrofit study of an ammonia plant, in purpose of improving energy efficiency. As a common practice, one can divide an ammonia plant into two parts: the hot-end and the cold-end. In the hot section, two different options are investigated that both lead to a threshold condition and achieve maximum energy saving....
Similar publications
The effects of conventional refrigerants on ozone layer and its effect on global warming are known. Refrigerants based on chlorofluorocarbons (CFC) and hydrochlorofluorocarbons (HCFCs) have been used in refrigeration systems for a long time and are still being used. Instead of these refrigerants, the use of natural refrigerants which are much less...
Citations
... The summary of energy targeting at optimum ΔT min is shown in Table 6. As shown, the absence of hot utility confirms that the problem is Threshold [39]. Fig. 7 shows composite curves at ΔT Threshold = 11.9°C, ...
There has been a growing recognition in recent years that Electrofuels (e-fuels), also known as renewable and sustainable fuels, which are produced from hydrogen and carbon dioxide as the primary feedstocks, have great potential to reduce carbon footprint and address climate change. In the present study, contrary to most previous studies in which the sources of feedstock's preparation were considered as block boxes, two stand-alone processes are taken into account and incorporated into the e-fuels production system. H 2 is obtained by a high-temperature electrolysis system having an overall efficiency nearly twice that of a low-temperature electrolysis system. CO 2 is captured from a power plant flue gas stream with a purity of 99.81%. Investigating heat integration potential in such an integrated plant is an up-to-date and interesting topic and has not yet been well explored. Therefore, a heat integration within the three individual processes is implemented to reduce energy consumption. The design of the process-to-process heat transfer section is carried out using pinch design rules. By integrating individual units, approximately 42% of the required cold utility, traditionally supplied by chilled water and refrigerants, is allocated to generate high and medium-pressure steams. Having used the high-temperature steam electrolysis for H 2 production, a process that requires less external electricity compared to low-temperature water electrolysis, a power-to-liquid efficiency of 70% is achieved. Furthermore, the results reveal a carbon conversion ratio of 98.6%, indicating the effective converting the carbon from the feedstock into liquid hydrocarbons.
... kmol) which was then scaled-up to 200 tons/day using a scale-up factor of 1.1375, as small sized plants could be scaled-up to a large size one when necessary (Axelrod, 2006;Ramos & Zeppieri, 2013;Sanchez & Martin, 2018;Vrijenhoef, 2017) reported that there is currently in existence, about 105 large-scale plants ranging from 600-1800tpd in practically every corner of the world, which is apparently close to this capacity. According to Panjeshahi et al. (2008), the recovery of fairly small amount of heat has the ability to accrue into a sizeable energy savings, as NH3 manufacture is voted as an energy intensive technique. For all heat exchangers present, the second law via Pinch Technology gives the thermal interactions between the chemical process and utility systems that surrounds them to improve utility consumption (Ozturk & Dincer, 2021;Tavares et al., 2013). ...
Optimal production of ammonia (NH3) using natural gas is necessary in order to make it available for wide range of applications including the manufacture of fertilizers, fuel for transportation and during synthesis of some chemicals. Achieving this would require strategic implementation of a control scheme to simulated ammonia production, capable of ensuring adequate realization of production targets. The work involves ASPEN Plus modeling, simulation, sensitivity analysis and control of NH3 production process. Steam/carbon ratio, conversion of CH4, removal of carbon dioxide (CO2) and carbon monoxide (CO), hydrogen/nitrogen ratio and heat exchanger and separator temperatures were identified as requiring control in units any of these specifically impacts. As a result, approximately 176 tons of NH3 was realized daily based on the simulation results and can be scaled-up using a calculated factor equivalent to 1.1375 to 200 tons/day capacity, in this design. Sensitivity analysis resulting in control of certain unit parameters is effective in ensuring process safety, maximum yield of important end-products and reduction in the cost of operation.
... Some thermal systems reach a point at which one of the thermal utilities reduces to zero; the value of ΔTmin diminishes by moving the hot and cold composite curves on horizontal axes. This is known as the threshold problem [53]. In the HEN design for threshold problem, the cold-end threshold problem can be considered as having only the part above the pinch point and should be designed from the cold-end; the hot-end threshold problem can be considered as having only the part below the pinch point and should be designed from the hot-end. ...
Methanol and ammonia are important chemical materials in the chemical industry. During the production of methanol and ammonia, a large amount of waste heat is released. The waste heat can be used to save energy and reduce CO2 emissions. In this study, pinch analysis is used to design the heat exchanger network (HEN) of pulverized coke (PC) chemical looping gasification coupled with coke-oven gas (COG) to methanol and ammonia (PCCLHG-CGTMA). The heat integration process is accomplished in two ways, as mentioned below. (1) The HENs in each of the three heat exchange units are designed individually; (2) the HENs of the three heat exchange units are treated as a whole and designed simultaneously. Compared to the HEN designed individually, when the HENs are designed as a whole, a total of 112.12 MW of hot and cold utilities are saved. In the HENs designed as a whole, the reduction in operating cost is sufficient to offset the increase in capital cost; the total annual cost (TAC) is reduced by 10.9%. These results reveal that the HENs designed as a whole have more scope for energy saving, which can be a reference for new HEN design and modification to realize more heat recovery and lower investment.
... Vast array combinations of feedstock and fuel resources for the classic ammonia plant have been investigated and the SMR-based routes proved to have a relatively small impact across several parameters (Tock et al., 2015;Zhang et al., 2020;Bicer et al., 2016). Acknowledging the maturity of SMR-based ammonia production technology, numerous studies have been performed to further increase its efficiency via several methods, i.e. operational, revamping, retrofit, etc. (Sadeek et al., 2020;Rafiqul et al., 2005;Panjeshahi et al., 2008;Song et al., 2017;Tran et al., 2017;Pedernera et al., 1999). Although most ammonia produced today is synthesized from NG, no study about variable NG composition has been reported. ...
Ammonia plays critical role as the second most produced chemical commodity with around 80% used in producing nitrogen-based fertilizer. Considering the decline of reserves of fossil-based feedstocks it is imperative to shift towards greener alternatives. However, such green ammonia processes are far from being economically viable. This makes natural gas-based ammonia synthesis the best available technology currently, but this faces critical difficulties as natural gas supply could widely vary due to declining reserve or changing sources, posing another key challenge to improve the efficiency of affected ammonia production.
This study is the first to investigate the effect of variable natural gas composition (within the range of 83-99.99% vol dry methane; towards lean gas) on an industrial ammonia production process with maintained key operating parameters value such as steam to carbon ratio (S/C), hydrogen over nitrogen ratio (H/N), etc. The sensitivity analysis shows that sustained energy efficiency of the process is possible, confirming the conventional ammonia plant's ability to withstand changes in feedstock and fuel supply. In addition, lean gas yielded a positive impact on the raw material intensity and CO2 emissions with average reductions of 1.17% and 1.79% per each 4% methane content increase, respectively.
... Frattini et al. [12] simulated several renewable pathways for synthetic ammonia production based on biomass gasification, biogas reforming and water electrolysis by wind or solar energy, then compared their energy efficiency and sustainability level, and finally gave related beneficial suggestions. Panjeshahi et al. [13] evaluated energy efficiency of retrofit of ammonia plant by the combined pinch & exergy analysis to prove effectiveness of their proposed measures. Tallaksen et al. [14] compared energy use and greenhouse gas emissions of ammonia production based on wind energy and fossil fuel. ...
... Next, the emergy of ecological service, required to dilute the i-th air emission/water pollutant, is calculated using Eqs. (13) and (14), respectively. ...
Sustainability of urea production should concentrate on its economic, energy and environmental performances, but few studies are found to address the three aspects simultaneously. Here a set of indicator system, composed of energy use, economic cost, and emissions' impacts in terms of emergy and carbon emission intensity, were built to investigate this issue. Next six scenarios of Chinese urea production, attained through combination of two ammonia synthesis methods and three urea production methods, were evaluated. The study results show that (1) urea production from natural gas (UPNG) should pay more attention to indirect energy use of raw materials and energy sources while urea production from coal (UPC) should more emphasize energy efficiency of production processes, (2) dust emissions should be emphasized for carbon dioxide stripping technology and ammonia stripping technology, while more attention should be paid to NH3–N discharge from urea production using aqueous solution full-cycle technology, (3) UPNG are worse than UPC according to energy consumption intensity and economic cost but better than the latter in terms of emissions’ impacts, and (4) generally combination of coal based ammonia synthesis and ammonia stripping method is the best one.
... Improved and novel methods of ammonia synthesis have seen great interest, aiming at transitioning away from the massive energetic footprint of the Haber-Bosch process. This can include better energy management of the production process through optimized heat recovery and energy efficiency, which could potentially decrease energy requirements by up to 15 percent (Panjeshahi et al., 2008), and transitioning toward greener energy sources and replacing the methane used by the process with renewable sources such as syngas or biogas from biomass gasification or anaerobic digestion, or even hydrogen, further reducing the environmental footprint of the process (Arora, 2017;Tunå et al., 2014). Researchers have also been investigating alternative ammonia synthesis processes, with notable interest surrounding photocatalytic, electrocatalytic, and plasma-assisted processes (Hao et al., 2020;Peng et al., 2018;Soloveichik, 2019). ...
In this chapter is presented part of the results of a project of the Greek Ministry of Rural Development and Foods (MRDF). This project aimed at the investigation of the freshwater quality (surface and groundwater) in River Water Basins EL07 and ELO4 located in Sterea Hellas, central Greece. This includes the identification of pollution sources as well as the proposal of measures for protection and restoration of water quality, according to the provisions of Community Directive 2000/60 and national regulations. The water properties discussed in this chapter are pH, electrical conductivity, and the inorganic nitrogen ions nitrite, nitrate, and ammonium. The entire area was divided into 11 catchments from which, for two consecutive years (2017–2018), water samples were taken at specified intervals from rivers, lakes, canals, and wells. These samples were analyzed in situ and in the laboratory, evaluated as to their suitability for drinking and irrigation, according to European Union and national regulations. The values of the parameters studied ranged widely among rivers, lakes, groundwater, and drainage canals, reflecting the various prevailing conditions in the different water sources and the special characteristics of the sampling positions. The median values of all the properties studied are lying within the normal and acceptable levels. However, in some places, extreme values, unacceptable for any use were recorded. The pH was higher in lake water, followed by rivers, canals, and groundwaters; electrical conductivity was found to be higher in river and canal waters, followed by canals and groundwaters; nitrite was higher in groundwaters followed by canals, rivers, and lake waters, while nitrate was higher in groundwaters followed by all other categories, and ammonium was higher in canals, followed by lakes, rivers, and groundwaters.
The sources of contamination on a case-by-case basis appear to be anthropogenic, such as poor agricultural practices and, in particular, unsound management of inputs (fertilizers and pesticides), the dumping into drainage canals of untreated municipal or/and industrial waste, livestock farming (as it was found in the catchments, Sperceios – C1, Kifisos – C5, and Asopos – C6). And there are natural sources, such as seawater intrusion and the chemical composition of the rocks of the study area (especially in the catchments: Sperceios – C1, Amfissa – C4, Messapios-Lilantas – C8, Nireas-Kireas-Voudoros-Kimasi – C9, Kallas – C10). The most significant suggested measurement of water contamination are the tracing of contamination sources to identify their origin (agricultural, livestock, urban, industrial), the implementation of good agricultural practices (especially in applying appropriate irrigation methods that reduce nutrient leaching into the aquifer), and the estimation of the nutrient needs by soil and plant analysis or by using precision agriculture practices, both of which permit the differentiation of the amount of nitrogen fertilizers needs by taking into account the significant variability of the soil properties. Furthermore, suggestions include the continuous monitoring of surface and groundwater through certain environmental indicators (for example nitrate content), and taking protection measures of water drilling and application of their protection zones following the River Basin Management Plans, which propose detailed measures based on the article 4 of the Water Framework Directive 2000/60.
... Many researchers have used these curves for energy studies [1]. Panjeshahi et al. (2008) divided an ammonia plant into two sections of the hot-end and the cold-end and presented some recommendations to improve energy efficiency. The cold-end section is mainly the ammonia synthesis and refrigeration cycles. ...
... The cold-end section is mainly the ammonia synthesis and refrigeration cycles. They used the EGCC diagram to minimize exergy destruction and losses and compressors' power demands in the cold-section of an industrial ammonia plant by suggesting new refrigeration levels [2]. Ataei (2011) used the EGCC diagram to correct the temperature levels of refrigeration cycles of an olefin plant in order to reduce exergy destruction and losses and compressors' power consumption. ...
... Thus, the thermal exergy destruction and losses within a HEN can readily be calculated and also needed modifications to increase the efficiency of refrigeration systems, can graphically be recommended. To investigate the accuracy of the new method, they studied a PRICO process and an ammonia refrigeration cycle (Panjeshahi et al., 2008) [12]. Safder Tables (ChExCT) as a numerical tool were introduced to achieve maximum waste energy recovery. ...
In this research, a new graphical tool entitled Omega Total Site Profile (OTSP) is introduced to simply calculate the exergy destruction and losses within a total site. This new diagram is obtained by the development of Omega Composite Curves (OCC) used for exergy destruction and loss calculations within an individual process. The OTSP diagram is linear and the enclosed area between process and utility streams has a rectangular shape and shows the thermal exergy destruction and losses within a total site. Having combined the new diagram with a mathematical optimization like Genetic Algorithm, a method to a new design or retrofit a total site is presented. Next, two case studies are used to demonstrate the performance of the proposed diagram and the optimization procedure. In the first total site case study by considering flexible temperature levels for utilities, the optimum scheme resulted in 14.6% and 24% lower exergy destruction and losses compared to the current design with fixed temperature levels for utilities. In the second total site case study, by considering three temperature levels of utilities, the optimum heat recovery design resulted in 24% lower exergy destruction and losses compared to the base case.
... Improved and novel methods of ammonia synthesis have seen great interest, aiming at transitioning away from the massive energetic footprint of the Haber-Bosch process. This can include better energy management of the production process through optimized heat recovery and energy efficiency, which could potentially decrease energy requirements by up to 15% (Panjeshahi et al., 2008), and transitioning towards greener energy sources, and replacing the methane used by the process with renewable sources such as syngas or biogas from biomass gasification or anaerobic digestion, or even hydrogen, further reducing the environmental footprint of the process (Arora, 2017; Tunå et al., 2014). Research has also been investigating alternative ammonia synthesis processes, with notable interest surrounding photocatalytic, electrocatalytic, and plasma-assisted processes (Hao et al., 2020;Peng et al., 2018;Soloveichik, 2019). ...
Fertilizers are at the foundation of our modern society, without which we would not be able to feed and sustain a majority of the world population. Of the major macronutrients necessary for agriculture, which include nitrogen (N), phosphorus (P) and potassium (K), nitrogen is essential for healthy plant growth, being vital for the production of amino-acids and proteins. For this reason, nitrogen is by far the most produced and applied fertilizer around the world, generally in the form of urea and ammonium salts, as well as through organic fertilizers such as manures, composts and digestates. Luckily, in the early 1900's, the Haber-Bosch process was developed, allowing for the production of synthetic nitrogen fertilizers on an industrial scale; a process that is still responsible for over 96% of the world's synthetic nitrogen production. However, despite the unimaginable benefits of nitrogen fertilizers on humanity, there have also been some significant impacts worldwide, notably ecologically and environmentally. Such impacts include soil acidification, eutrophication, nutrient runoff , reduced biological diversity, and substantial greenhouse gas (GHG) emissions. This chapter aims at exploring the environmental and ecological impact of nitrogen fertilizers, discussing the impact of their production and application to land.
... Unreacted nitrogen from the second step is carried through the entire ammonia synthesis plant and needs to be balanced for the stoichiometric requirements of the Haber Bosch reaction, R1. Since its introduction, efforts have been made to improve catalyst selectivity, reduce operating pressure and optimize heat integration of the Haber Bosch process [10][11][12]. Modern optimized Haber Bosch plants still require high pressure (>20.3 MPa) to shift the equilibrium of R1 forward, which accounts for 10-16% of the process energy demand [13]. ...
Stranded Natural Gas (SNG) flaring has increased over the last decade resulting in additional Green House Gas (GHG) emissions and underutilization of our finite fossil fuel resources. However, utilization of SNG is difficult due to its low volume, inconsistent composition, and intermittent flow. In this paper, intensified Chemical looping for Ammonia Synthesis (CLAS) is explored as a process suitable for remote deployment at SNG sites. CLAS mediate ammonia synthesis by using compounds that carry nitrogen and hydrogen in stepwise reactions, allowing ammonia synthesis under milder conditions and smaller, more flexible processes. The challenge in CLAS is to find a feasible combination of materials and process conditions that yield ammonia at economically acceptable rates. We propose a framework that systematically evaluates CLAS to determine their suitability for SNG deployment. CLAS reaction schemes are reviewed and organized based on the mediating compounds used to synthesize ammonia. Different compounds are evaluated for each CLAS in search of a thermodynamically spontaneous pair. Spontaneous CLAS flowsheets are, then, optimized to maximize ammonia output at equilibrium. The results are ranked against performance metrics of energy intensity, efficiency, and cost. Chemical loops with Ca3N2/CaH2, SrH2/Sr3N2, MnO2/Mn5N2 and MoO2/Mo2N are found to have favorable performance, along with literature-reported evidence and are recommended for further evaluation toward a distributed ammonia synthesis solution.
... Regarding production of nutrients, the main source of emissions is the high energy requirement for ammonia synthesis and the energy required for P and K production. This could potentially be reduced by a variety of ways, such as through improving heat transfer and energy efficiency (Fló rez-Orrego and de Oliveira Junior, 2017;Panjeshahi et al., 2008;Rafiqul et al., 2005), using alternative, non-fossil, energy sources (Arora, 2017;Tallaksen et al., 2015;Tock et al., 2015;Tunå et al., 2014), or even transitioning towards emerging photocatalytic and electrocatalytic ammonia synthesis processes Michalsky et al., 2012;Montoya et al., 2015;Zhou et al., 2017). ...
Fertilizers have become an essential part of our global food supply chain and are necessary to sustain our growing population. However, fertilizers can also contribute to greenhouse gas (GHG) emissions, along with other potential nutrient losses in the environment, e.g. through leaching. To reduce this environmental impact, tools such as life cycle assessments and decision support systems are being used to aid in selecting sustainable fertilization scenarios. These scenarios often include organic waste-derived amendments, such as manures, composts and digestates. To produce an accurate assessment and comparison of potential fertilization scenarios, these tools require emission factors (EFs) that are used to estimate GHG emissions and that are an integral part of these analyses. However, such EFs seem to be very variable in nature, thereby often resulting in high uncertainty on the outcomes of the analyses. This review aims to identify ranges and sources of variability in EFs to provide a better understanding of the potential uncertainty on the outcomes, as well as to provide recommendations for selecting EFs for future studies. As such, an extensive review of the literature on GHG emissions from production, storage, transportation and application of synthetic fertilizers (N, P, K), composts, digestates and manures was performed. This paper highlights the high variability that is present in emissions data and confirms the great impact of this uncertainty on the quality and validity of GHG predictions related to fertilizers. Variability in EFs stem from the energy source used for production, operating conditions, storage systems, crop and soil type, soil nutrient content, amount and method of fertilizer application, soil bacterial community, irrigation method, among others. Furthermore, a knowledge gap exists related to EFs for potassium fertilizers and waste valorization (anaerobic digestion/composting) processes. Overall, based on this review, it is recommended to determine EFs on a case by case basis when possible and to use uncertainty analyses as a tool to better understand the impact of EF variability.
