Refinery Plant Research Articles

Continuous Characterization of the Odour Emissions by Advanced Instrumental Odour Monitoring System in Oil Refinery and Petrochemical Plant

Oil refinery and petrochemical plants are of crucial importance to enhance world economy. Besides the related considerable economic impact of this industries, the population and governments pose towards a great attention which boosted the necessity of developing effective tools for the control of the associated environmental pressures, without hindering economy growth. Among the environmental aspects of key relevance in the refinery sector, air quality and atmospheric pollution in terms of odour emissions, especially in the last years, have become a priority concern in the management of the plants. The monitoring and control of the odour emissions are thus needed in order to prevent potential impact and avoid complaints from the exposed population. Nowadays, senso-instrumental methods by using Instrumental Odour Emissions Systems (IOMSs) represents the most attractive tool for the monitoring of environmental odours, allowing the possibility to obtain real-time and continuous information’s, to support the decision-making process and for the implementation of proactive approach. No universally accepted regulation or standardized procedure exist at present and limited data are available in the scientific and technical literature with reference to these systems for the odour monitoring control in the oil refinery plants. In the CEN/TC264 ‘Air Quality’ standardization committee, a specific working group (WG41) is currently working to produce a validation procedure for the IOMSs. The research presents and discusses an advanced instrumental odour monitoring system device useful for the continuous characterization of the odour emissions in complex oil refinery and petrochemical plants. The influence of the use of different feature extraction methods in the odour monitoring model elaboration, in terms of classification, is analysed. Results demonstrate the existence of considerable differences in terms of correct classification percentage, in the use of different feature extraction methods. The importance and usefulness of having a fully-developed flexible system that allows to select and compare automatically different settings options, as the different feature extraction methods, in order to guarantee the best training model, is highlighted. Results demonstrated the high reliability of the system in recognizing artificial gas samples, with characteristics similar to the emissions from refinery plants.

Use of Drone to Measure Odour Gases in a Refinery Plant

The objective of this study was to identify odorous gases “fingerprint” and quantify odor throughout the production process of an oil refinery located in Rio Grande do Sul State, Brazil. The NH3 (ammonia), H2S/CH4S (hydrogen sulphide/methylmercaptan), SO2 (sulfur dioxide) and VOCs (volatile organic compounds) gases were measured during 14 consecutive days around emission sources and throughout the company's production process. The monitoring was performed on main stacks, tanks vent, production process and wastewater treatment station. To measure over the stacks, it was used a Drone DJI to suspend a set of integrated electrochemical sensors that analyze the air continuously. This system made it possible to record the emission from stacks at heights of up to 120 meters above ground level, which was previously impossible to accomplish. Cairpol’s electrochemical sensors were used to provide automatic and continuous measurement. This equipment records the measurements in ppb (part per billion) every minute and stores them in an internal data logger. The odorous gas analysis results showed that the largest sources of emissions are the industrial effluent treatment, which is responsible for the emission H2S/CH4S and VOCs and the emission from the oil-water separator is only of VOCs. The flare stack and the Sulfur Recovery Unit’s stack are the main emitters of H2S/CH4S and SO2. However, the coverage radius for the effluent treatment station and the oil-water separator is small due to the emission characteristics, as the emissions at ground level. The main sources of odor emission that can spread and annoy the neighborhood are the stacks as they presented the higher concentrations, henceforth their odor emission can be perceived from kilometers of distance.

Biodegradation of toluene in a two-phase low-pressure bioscrubber with using silicon oil as organic phase

ABSTRACT The aim of the present study was biodegradation of toluene using a two-phase low-pressure bioscrubber with silicon oil as organic phase. The bioscrubber designed in this study consisted of two parts, the adsorption column and the bioreactor. In order to increase the efficiency of the scrubber, silicone oil was added as organic phases in concentrations of 5%, 7.5% and 10% and tested. The source of the toluene degrading microorganisms was the treatment plant of Tehran refinery. Important operating parameters include inlet concentration (mg/m3), outlet concentration (mg/m3), biomass content (g/l), removal efficiency (%), and elimination capacity (g/m3.h). The results showed that the use of 5% silicon oil increased the efficiency from 22% in the state without organic phase to 55% in the case of using 5% silicone oil. Also, the results showed that at a concentration of 5% organic phase, the lowest efficiency was 47% and the highest 71%, and the use of silicone oil in a concentration of 5% increased the efficiency by 38%. Finally, at a concentration of 10% organic phase, the lowest efficiency was 36% and the highest 64%. The use of silicone oil in a concentration of 10% increased the efficiency by 33%. According to studies, bioscrubber can be one of the most effective methods to remove volatile organic compounds compared to conventional methods. However, there are many challenges in using biological systems that can be overcome in a bioscrubber and have better control over its performance parameters.

Lights and Shadows of the Voc Emission Quantification

Nowadays, Volatile Organic Compounds (VOC) are a class of air pollutants increasingly studied in the scientific literature, due to the well-known impact on human health and the environment. They can be emitted from different sources, including various types of industrial plants, such as oil refinery and petrochemical plants. For these reasons, the attention of control agencies on VOC emissions has increased and with it the request to quantify the total amount of VOC emitted by a plant, to monitor and to reduce this emission. However, several critical aspects still exist related to the classification of VOCs and their quantification. Indeed, different definitions of VOC are reported in scientific and technical literature. These diversities result in multiple strategies for quantifying the VOCs emitted by an industrial plant. Therefore, this paper reviews the available regulation about the quantification of VOC emitted from industrial plants, focusing on refineries and petrochemical plants, to underline some formal inconsistencies in VOC estimation procedures. From this comparison, it appears clear that VOC quantification can be addressed in different manners, obtaining a substantial non-uniformity of the VOC emission data. The data difference can conduct to a misleading estimation of emission rate.

Techno-economic assessment at full scale of a biogas refinery plant receiving nitrogen rich feedstock and producing renewable energy and biobased fertilisers

Anaerobic digestion of nitrogen (N) rich substrates might be hindered when ammonia (NH3) formation reaches toxic levels for methanogenic microorganisms. One possible strategy to avoid inhibiting conditions is the removal of NH3 from digestate by stripping and scrubbing technology and by recirculating N depleted digestate back to the digester. This study aimed to i) monitor the performance (mass and energy balances) of a full scale digestate processing cascade that includes an innovative vacuum side stream NH3stripping and scrubbing system, ii) assess the production cost of ammonium sulphate (AS) solution and iii) evaluate its fertiliser quality. The use of gypsum to recover NH3 in the scrubbing unit, instead of the more common sulphuric acid, results in the generation of AS and a fertilising liming substrate. Mass and nutrient balances indicated that 57% and 7.5% of ammonium N contained in digestate was recovered in the form of a 22% AS and liming substrate, respectively. The energy balance showed that about 3.8 kWhel and 59 kWhth were necessary to recover 1 kg of N in the form of AS. Furthermore, the production cost of AS, including both capital and operational costs, resulted to be 5.8 € t−1 of digestate processed. According to the fertiliser quality assessment, this technology allows for the recovery of NH3in the form of salt solutions that can be utilised as a substitute for synthetic mineral nitrogen fertilisers.

Exergy Study of Sour Water Stripper Unit of Delayed Coker Unit in a Refinery plant: A Real Start-Up Plant

Process sour water produced from refinery contains some hazardous pollutants as (H2S and NH3). Sour water stripper units remove both compounds from water. The two stripped pollutants are sent to Sulphur recovery unit to produce Sulphur and prevent any acidic emissions against environmental regulations. The sour water stripper unit serving the delayed Coker unit was simulated with Aspen HYSYS V.11 and an exergy study was conducted on different equipment. While energy is transformed from a form to another, exergy is destructed in an irreversible process. The total exergy is equal to physical and chemical exergies. Physical exergy is calculated through HYSYS and chemical exergy is calculated through a series of equations embedded in excel. The exergy destruction rates, the destruction efficiency and the percentage share of the destruction of each equipment was calculated. The total unit destruction rate was 2996.25 kW. The stripper showed the highest destruction rate 2592.23 kW and a percentage share of 86.52 % of total destruction. The overall efficiency of exergy is 81.58%. A comparison was conducted between the exergy results of this study with two other exergy studies performed in the same refinery plant. The columns in the three studies showed the highest destruction rates exceeding 78% of the total destruction of each unit. The air coolers showed the second- highest destruction rates in their units with a percentage share exceeding 7% of total destruction. The pumps showed the lowest destruction rates with values of less than 1% of the total destruction of each unit.

Exergy analysis of petroleum refinery hydrogen network integration based on reaction system

High-purity hydrogen is a crucial input in a crude oil refinery to upgrade several products. For this reason, the effective hydrogen management is necessary to satisfy hydrogen requirements. On the other hand, adding exergy analysis to the hydrogen pinch analysis especially for refinery plants, where hydrogen reacts under high temperature and pressure, helps improve the efficiency of unit by overcoming the lack of pinch analysis. The aim of this study is the simulation and exergy analysis of reactors within hydrogen network integration of a petroleum refinery retrofitted by pinch analysis before. Two hydrogen production and four consumption units were considered and simulated by Aspen Plus, and then the exergy efficiencies were calculated. Low exergy efficiencies were determined in the hydrogen production and hydrodesulfurization units, whereas the separation of excess hydrogen from the desired product considerably effected on the efficiency. The results also show that not only the hydrogen demand of reactors has to be reduced, but also the hydrogen recovery and purification is very important for the increase in efficiency. Although the processes are carried out at the high operating conditions, the reactions significantly affect the total exergy flow rate.

Retrofit of heat exchanger networks by graphical Pinch Analysis – A case study of a crude oil refinery in Kuwait

Energy integration of the existing chemical and petrochemical facilities is regarded as a keystone for sustainable energy systems. It is widely known that a considerable number of the petrochemical industries are not applying efficient heat exchanger network (HEN) systems to minimise the use of external utilities. In the present study, a Pinch Analysis-based graphical approach is used to retrofit an existing HEN for optimising a crude oil distillation operation. The existing HEN is represented using Thot–Tcold diagram, where the cold stream temperatures are plotted on the x-axis and the hot stream temperatures are plotted on the y-axis, for each exchanger unit. The graphical approach is applied to a real case study of a petroleum refinery plant located in Kuwait with the objective of performing energy analysis and retrofitting the existing HEN. Retrofit modifications are extracted from the graphical representation to enable scenarios for energy and emission reduction. The application of the proposed approach resulted in substantial energy savings of about 10.4 MW compared to the current operation, leading to annual operating cost savings of about MM$2 and less than one-year payback time. Overall, this study provides tools to address the energy traits in crude preheat trains of industrial feature, which can improve the overall economic–environmental sustainability of existing refineries.

A Spectral AutoML approach for industrial soft sensor development: Validation in an oil refinery plant

Spectral AutoML is a platform for fast development of PAT soft sensors that considers the combined effect of pre-processing, band selection, band-wise resolution definition, hyper-parameter tuning and model estimation. Spectral AutoML was compared with models developed under the classic paradigm, and their performance assessed on an independent test set. The validation study regards the prediction of 12 different diesel fuels properties, using FTIR-ATR spectra. The proposed framework led to clearly better predictions in 8 out of the 12 properties, and minor improvements in 3 properties. The Spectral AutoML results were obtained overnight, without interfering in the daily work of the users, while the benchmark models resulted from several months of work and fine tuning of the methods. The results demonstrated the added value of the proposed Spectral AutoML approach in terms of prediction accuracy, development time of the models and reduced dependence on resident experts.

An innovative techno-economic analysis for the selection of an integrated ejector system in the flare gas recovery of a refinery plant

The compression process in flare gas recovery, commonly carried by compressors, is the costliest. The use of an integrated gas-gas ejector system instead of a compressor is proposed and studied technically and economically in this paper. Thus, the flare gas recovery process modeling, including the gas sweetening unit, is performed for both compressor and ejector systems. Different arrangements of the integrated ejector system in the form of multi-stage ejectors (series) in parallel branches are also investigated. To find the geometry of ejectors for simulation of integrated ejector system in Aspen HYSYS, as well as the prediction of the ejector performance under different pressures and mass flow rates of inlet gas, a computer code was developed in MATLAB software. Results of the economic analysis demonstrated the compression method with a parallel three-branch arrangement (containing a three-stage ejector in each branch) were the most appropriate solution in the flare gas recovery of a typical oil refinery plant, with an investment cost of 4.84 $M and accepted payback period of 2 years and the recovery of approximately 90% flare gas volume during normal operation.

A Formal Framework for Secure Fog Architectures

Despite the importance of fog computing, few works using formal techniques have been interested in the modelling and verification of fog architectures to ensure their security. The present work fits into this context and proposes a generic formal model (CA-BRS), extending the BRS with control agents. This offers the possibility to specify a fog architecture consisting of a set of secure fog nodes that act both as filters to reduce the amount of data sent to the cloud and as processing units close to the data collected. This formal setting makes possible the description of the multi-layers' collaboration requirements (IoT, fog, and cloud) and the analysis of certain security requirements with regard to identity management and resource access management. The execution of CA-BRS model through the framework supporting tool: “Maude-based Tool for CA-BRS” allows the formal analysis of the reliability and availability properties of an illustrative fog system example which is an oil/gas refinery plant.

A fuzzy DEMATEL-ANP-VIKOR analytical model for maintenance strategy selection of safety critical assets

In most industries, such as aerospace, manufacturing, transport and energy sectors, maintenance plays a vital role in improving the performance of safety critical equipment and facilities. It also helps industries achieve the largest possible efficiency, ensure workplace and environmental safety, and reduce unnecessary breakdowns and costs. Therefore, it is crucial for industries to adopt an optimal maintenance strategy for their critical systems and infrastructure. In this study, we aim to propose a novel analytical multi-criteria decision-making (MCDM) methodology for selecting the most suitable maintenance strategy in distillation units of oil refinery plants. The alternative maintenance strategies include run-to-failure (RTF), preventive maintenance (PM), condition-based maintenance (CBM), and reliability centered maintenance (RCM), which are evaluated with respect to 12 sub-criteria in three categories of economical, safety, and sustainability issues. The MCDM methodology consists of a DEMATEL-based analytic network process (ANP) method to determine the importance weights of decision criteria and a VIKOR method to rank the maintenance strategies. Also, interval type-2 fuzzy sets are used to capture uncertainty in experts’ individual judgments. Finally, a real case study is provided to show the applicability of the proposed methodology to an oil refinery plant. The results show that, thanks to advances in degradation modeling, sensor technology, and data analytics platforms, the RCM and CBM are the superior maintenance strategy for crude oil distillation systems.

Technical evaluation and optimization of a flare gas recovery system for improving energy efficiency and reducing emissions

Gas flaring is a significant cause of air contamination and a source of energy losses in the oil and gas industry. A liquid ring compressor is a cost-effective and appropriate technology, which can be used to recover flare gas from various sources. In this paper, a novel flare gas recovery process based on liquid ring compressors is proposed, in which flare gases are compressed and treated simultaneously using methyl diethanolamine. This process is simulated here through some custom models in Aspen HYSYS and MATLAB software, and the effects of operating and design parameters on the performance of the proposed flare gas recovery system are examined. Results demonstrate that the H2S absorption efficiency can be improved by reducing amine temperature or raising the flow rate of the recycling amine. However, the energy consumption of the process increases in these conditions. It is also demonstrated that there is an optimum value for the lean amine solvent concentration to minimize the H2S concentration of the outlet gas. The process analysis shows that by integrating the proposed flare gas recovery system with a refinery plant generating 0.5 MMSCFD of flare gas, it is possible to recover 87% of the available heating value in the flare gas. Also, the environmental aspects of the plant is considerably improved by preventing the release of 28 mtCO2 equivalent per day to the atmosphere. Due to the overlapping effects of system operating parameters, a multi-objective optimization is conducted to optimize the process, and the Pareto solutions set consists of the best possible trade-offs between process energy consumption, H2S concentration of outlet gas, and lean amine solvent consumption are generated.

ОГЛЯД БІТУМНИХ В'ЯЖУЧИХ, ЩО ВИКОРИСТОВУЮТЬСЯ В УКРАЇНІ

Introduction. Pavement bitumen is one of general road construction materials that are used for pavement construction. The quality of bitumen binder regulates specific technical and operational characteristics of asphalt pavements and their durability Problem Statement. Nowadays in Ukraine only one refinery plant produces pavement bitumen. The volume of its production is not enough to completely satisfy the demands of Ukrainian road construction industry. Due this a lot of binders in Ukraine are imported from other countries. In recent years the highest volumes of bitumen was imported from Republic of Belarus and Poland. In 2020 the amount of road construction works was increased, particularly with pavement repairing and new pavement constructing. It resulted in increasing in need in pavement bitumen that led not only to the high volume of import bitumen but to an expansion of the list of importing counties. Purpose. The presented study is aimed on analysis of quality of bitumen imported in Ukraine from eight countries. For these binders their features are obtained and problem of their applicability and its advisability in Ukraine road industry is considered. Materials and methods. As a material of research bitumens produced in Azerbaijan, the Republic of Belarus, Greece, Spain, Italy, Poland, Turkey and Ukraine are chosen. The standard quality properties are obtained in accordance with the actual in Ukraine standards ДСТУ 4044 and ДСТУ EN 12591. Beside this the attention is paid to the finding of fundamental properties of these binders, such as adhesion, cohesion and viscosity. Results. With the experimental data it is found that all bitumens significantly differ in their structural type. It results in differences in softening point and breaking point temperatures at the equal penetration value (this difference is in the range from 4.5 °С for the closer values to 16.5 °С for the most distinct values). This fact can influence on asphalt pavement properties and durability. Besides such a difference in a temperature susceptibility of binders their adhesion and cohesion properties differ too. Bitumen that tends to sol type of structure is characterized with higher cohesion and viscosity values. This peculiarity must be taken into account in mixing and compaction operations for the asphalts with such bitumen. The temperatures of these operations must be higher than one for bitumen close to the gel type. The low temperature susceptibility and wide plasticity interval are the advantages of bitumen that tends to gel type of structure. Conclusions. All bitumens that are imported in Ukraine must be certificated with ДСТУ 4044:2019 national standard requirements. Also they must be tested with additional methods to validate the decision on their implementation in road construction industry and to specify the implementation area. Keywords: paving bitumen, bitumen binder, penetration, softening point temperature, adhesion, cohesion, viscosity

Inhibition of the metabolism of mixed cultures of purple phototrophic bacteria by typical refinery and petrochemistry wastewater pollutants

AbstractBACKGROUNDAnaerobic treatments based on purple phototrophic bacteria (PPB) can be a more efficient and less energetically demanding alternative to aerobic biological processes currently used in refinery and petrochemistry wastewater (RPWW) treatment plants. Toxic compounds in the RPWW might compromise PPB metabolism, limiting its feasibility. In this work, seven toxic compounds that are typical components of RPWW [benzene, toluene, ethylbenzene, o‐xylene (BTEX), furfural, methyl‐di‐ethanolamine (MDEA) and butanone] were evaluated as potential inhibitors of the specific activity and growth of PPB.RESULTSInhibitory Ki parameters of 50% reduction of specific activity or biomass yield were calculated. Most of the BTEX compounds showed initial inhibitory effects on the specific activity, with Ki values of 305 ± 9, 151 ± 17 and 84 ± 2 mg L−1 for benzene, toluene and ethylbenzene, respectively. These compounds also caused inhibition of PPB growth (Ki of 411 ± 7 and 241 ± 3 mg L−1, 26% below the control, respectively). By contrast, o‐xylene affected neither the activity nor the growth. Furfural inhibited the initial specific activity (Ki of 448 ± 24 mg L−1), with no effect over the PPB growth. However, MDEA and butanone improved the initial specific activity of PPB (15% and 40% above the control, respectively). However, butanone negatively impacted the growth which decreased to ≤40% below the control.CONCLUSIONSCalculated inhibition thresholds for the seven toxic compounds were far above the actual concentrations found in the RPWW. Thus, anaerobic treatments based on PPB for the treatment of RPWW would not be limited by the presence of the toxic compounds studied here. © 2021 Society of Chemical Industry (SCI).

Echo-state networks for soft sensor design in an SRU process

The implementation of soft sensors for industrial processes is expanding in applications for recent machine learning techniques. In this work, strategies based on reservoir computing are applied to developing dynamical models of target variables in a sulfur recovery unit (SRU) of a refinery plant in Italy. In particular, a specific type of recurrent network, namely an echo-state network (ESN), is adopted to estimate key process variables on the SRU. Two process lines are considered to evaluate the proposed algorithm on different datasets in terms of estimation performance and computational effort of the learning process. The obtained results are evaluated in comparison with other recurrent networks, based on long short-term memory, and with other techniques reported in the literature, demonstrating the feasibility of the proposed approach. Furthermore, the introduction of intrinsic plasticity (IP) is also considered to adapt the reservoir parameters to the provided inputs, achieving a significant improvement in the statistical distribution of the results obtained for the pool of learned networks. The reported results show that ESN-IP represents a suitable solution for identifying dynamical models of the industrial processes, avoiding the time-consuming regressor selection procedure, which is needed when a static network is adopted to design a dynamical model.

What’s the Role Of Corn Ethanol Fuel in China: From the Life Cycle Cost View

China originally planned to use fuel ethanol gasoline nationwide in 2020, and taking corn as an important raw material of ethanol gasoline, this paper analyzed the life cycle cost model of corn fuel ethanol gasoline and traditional gasoline from production to consumption, including internal and external cost calculations. The internal cost is the actual cost of the industry chain, while the external cost is converted into the cost value by examining the environmental impact of pollutant emission levels in each stage of the life cycle of ethanol gasoline production. Based on this model, by selecting the project data of specific regions and manufacturers in China, it can be calculated as follows: The main links affecting the internal cost of ethanol gasoline production are crude oil procurement cost, refinery and ethanol plant construction cost; The main influencing link of external cost is the emission of ethanol gasoline combustion, including the fuel, power and other energy consumption factors in the production of ethanol and gasoline; The cost can be optimized from the perspective of production technology, technological process, energy material consumption and various labor costs. Assuming E10 is used in the whole Chinese market, the empirical results are as follows: among the pollutants produced by the use of ethanol-added gasoline in the whole region, CO2 emission reduction is the largest, exceeding 53 million tons, followed by CO and wastewater emission reduction of 1.78 million tons and 1.58 million tons respectively. In terms of the conventional gasoline, the CO emission reduction of about 20% is the largest, followed by about 17% reduction of HC, about 15% reduction of SO2 and about 9% reduction of CO2 respectively. These results show that the promotion of ethanol gasoline (E10) usage in China has a considerable reduction effect of emission if the availability of raw materials are sufficient. The life cycle external cost of ethanol gasoline is 11.45%, lower than that of conventional gasoline. In 2019, China’s fuel ethanol production capacity was 4.15 million tons, and the actual production was about 3 million tons. Assuming that all of it were used to produce E10 ethanol gasoline, compared with traditional gasoline consumption, the emission reduction benefit of E10 gasoline would be nearly $84.7 million.

CFD simulation for dispersion of benzene at a petroleum refinery in diverse atmospheric conditions.

Atmospheric parameters play a vital role in the dispersion of air pollutants. Benzene is a confirmed human carcinogen. It is also a neurotoxin and an irritant compound. The objective of this study was to examine the CFD simulation by Fluent16 software to simulate and analyze the effect of atmospheric conditions on the dispersion of benzene in eight different scenarios in a petroleum refinery. According to the results of this study, the highest and lowest impacts of atmospheric parameters occurred on spring days and autumn nights, respectively. Wind direction did not have a significant effect on the benzene distribution due to the artificial ceiling of piping installations in the computational domain. However, the wind speed had a critical role in the benzene dispersion. The maximum concentration occurred at 36- to 37-m distance from the inlet boundary for all scenarios except winter nights. On winter nights, this distance increased to 38 m. Benzene concentrations were the highest at their sources of release. They decreased after the artificial ceiling of the pipelines was at 5.5- to 7-m height where the air displacement was not sufficient, and therefore, leading to a gradual reduction in concentration. The accumulation of benzene concentration in the small domain was noticeable compared to the benzene concentration distributed in the total computational domain, and the authors recommended control measures in this domain. This study demonstrated CFD simulation methodology could enable the investigators to predict the benzene concentration dispersion in the atmosphere of a petroleum refinery plant. These findings can be used by occupational health engineers for health risk assessment of refinery personnel involved with maintenance operations and engineering control systems.

Evaluation of Process Control Schemes for Sour Water Strippers in Petroleum Refining

For the sour water strippers in petroleum refinery plants, three prediction models were developed first, including the estimators of sour water feed concentrations using convenient online measurements, the minimum reboiler duty and the corresponding internal temperature at a specific location (Tstage,29). Feedforward control schemes were developed based on these prediction models. Four categories of control schemes, including feedforward, feedback, feedback with external reset, and feedforward-feedback, were proposed and evaluated by the rigorous dynamic simulation model of the sour water stripper for their dynamic responses to the sour water feed stream disturbances. The comparison of control performance, in terms of the settling time, integrated absolute error (IAE) of the NH3 concentration of the stripped sour water and IAE of the specific reboiler duty, reveals that FFT (feedforward control of Tstage,29) and FBA-DT3 (feedback control with 3 min concentration measurement delay) are the best control schemes. The second-best control scheme is FBAT (cascade feedback control of concentration with temperature).

A review of bio-oil upgrading by catalytic hydrotreatment: Advances, challenges, and prospects

• Two most common biofuels production techniques including fast pyrolysis and HTL arecovered. • The proposed crude bio-oil upgrading approaches are discussed. • Effects of various upgrading parameters on bio-oil HDO are described. • The mechanism for catalyst deactivation and possible solutions are provided. • Chemistry of major bio-oil model compounds during HDO is thoroughly reviewed. Fast pyrolysis and hydrothermal liquefaction (HTL) have been regarded as the most promising thermochemical conversion technologies for liquid bio-fuels production. However, the poor quality of generated crude bio-oils, such as high O and water contents, low thermal stability, and high corrosivity, limits their direct applications as the alternative transportation fuels. Thus, a number of upgrading techniques mainly including chemical and physical methods have been developed. Among them, hydrotreatment like hydrodeoxygenation (HDO) as a well-established technology at petroleum refinery plants has been widely adopted for upgrading of the crude oil obtained from pyrolysis or HTL. In this review, the effects of various upgrading reaction conditions (temperature, H 2 pressure, solvents, residence time, and catalyst) of HDO treatment of real bio-oil and its mode compounds are thoroughly reviewed. In which, the underlying mechanisms for bio-oil HDO are elucidated with a wide range of its model compounds (lignin-derived oxygenates and carbohydrates-derived oxygenates) and the interaction between these model compounds. Moreover, a discussion regarding the HDO of real bio-oil from pyrolysis and HTL is provided, and the technical/operating problems for the catalytic HDO and the possible solutions are presented. Finally, the important knowledge gaps and future directions are addressed for further investigations.