The role of fluid catalytic cracking in process optimisation for petroleum refineries

Petroleum refining is a chemical process in which the raw material (crude oil) is converted to finished commercial products for end users. The fluid catalytic cracking (FCC) unit is a key asset in refineries, requiring optimised processes in the context of engineering design. Following the first stage of separation of crude oil in a distillation tower, an additional 40 per cent quantity is attainable in the gasoline pool with further conversion of the downgraded product of crude oil (residue from the distillation tower) using a catalyst in the FCC process. Effective removal of sulphur oxides, nitrogen oxides, carbon and heavy metals from FCC gasoline requires greater separation efficiency and involves an enormous environmental significance. The FCC unit is primarily a reactor and regeneration system which employs cyclone systems for separation. Catalyst losses in FCC cyclones lead to high particulate matter emission on the regenerator side and fines carryover into the product on the reactor side. This paper aims at demonstrating the importance of FCC unit design criteria in terms of technical performance and compliance with environmental legislation. A systematic review of state-of-the-art FCC technology was carried out, identifying its key technical challenges and sources of emissions. Case studies of petroleum refineries in Nigeria were assessed against selected global case studies. The review highlights the need for further modelling investigations to help improve FCC design to more effectively meet product specification requirements while complying with stricter environmental legislation

Gaps in regulation and policies on the application of green technologies at household level in the United Kingdom

ited Kingdom (UK) government established a Ten-Point Plan and over GBP 5 billion to support Green-Tech to lay the foundations for a green industrial revolution and reduce emissions by 180 million tons of carbon dioxide equivalent (CO2e) by 2032. Households and buildings contribute around 40% of the UK’s total GHG emissions, which implies that key actions are needed in all areas around the building sector (Point 7). This study provides an overview and analysis of the existing regulation and standards in the UK building/household sector, to understand the current state-of-the-art and identify gaps preventing Green-Tech wider implementation and use. Discrepancies in regulation and standards were identified. Given that households bring together and adhere to numerous standards and regulations, the analysis highlighted that it is critical to formulate relevant actions starting from the individuals with engagement and information. Complete and clear guidelines addressing environmental awareness, the performance and economical convenience of Green-Tech implementation and related regulations, are required to come to a consensus on the best way to move forward to achieve sustainability and NET-ZERO targets

Predicting the effects of capping contaminated sediments via numerical simulations

Contaminated sediments are one of the key risks to human health and the environment, due to high concentrations of many types of substances contained in them and their direct contact with the aquatic fauna. This contributes to fish consumption advisories and limits the uses of many water bodies. In this study, an in situ capping (ISC) is considered as a potential remedy to minimise the exposure of aquatic ecosystems to sediment contaminants and a valid alternative to ex situ remediation options, by reducing contaminant fluxes to the upper water. Numerical design simulations, taking into account a biosorptive sediment cap and comparing different adsorptive characteristics of sediments, are proposed. As a case study, polychlorinated biphenyls contaminated sediments of Lake Hartwell, an artificial lake located in South Carolina, USA, were considered. A numerical predictive model of concentrations in a multilayered bed sediment and overlying water was developed in order to evaluate the long-term effectiveness of ISC of different thicknesses. Results showed that, for the case study, a minimum 20 cm cap allows to reduce the contaminant flux to the overlying water through reaction of the contaminants with the capping matrix, by highlighting how sediment biosorptive characteristics can influence the cap design

Associated health risks from heavy metal-laden effluent into point drainage channels in Faisalabad, Pakistan

Industrial effluent discharge has increased due to rapid urbanization and industrialization. Irrational use of this water for irrigation has caused environmental and health issues. The objective of the current study is to evaluate the treated effluents of textile, ghee and chemical industries for major heavy metals (Cd, Cr, Ni, Pb and Fe) and other basic analysis (pH, EC, TSS and TDS). Effluent samples were collected from the discharge of industries entering into main wastewater collecting channel located in Faisalabad city. Heavy metals contents were determined via atomic absorption spectrophotometry. Results showed that the highest pH (11.06) was recorded in textile effluent while EC (7.89mS/cm), TSS (1185.55mg/L) and TDS (6317.33mg/L) were found highest in chemical industrial effluents. Heavy metals contents were determined through atomic absorption spectrophotometer. The mean comparison of heavy metal concentration (mg/L) showed the concentration of Cd, Cr and Ni were within the safe limits; however, Fe and Pb were higher than the safe limits in all industrial effluents. The highest/unsafe concentration of metal Fe was recorded 4.093, 2.979 and 2.959 mg/L in the effluents of chemical, textile and ghee mill respectively. While the highest/unsafe concentration of metal Pb was recorded 0.643, 0.578 and 0.286 mg/L in the effluents of textile, chemical and ghee mill respectively. The permissible limits of heavy metals Fe and Pb is 0.5 and 2 mg/L respectively. We conclude that before discharge into a receiving stream, the effluents must be treated more time with a treatment method that removes Pb and Fe within standard limits else the discharge will pose pollution and health risks to human beings

An innovative in-situ DRAINage system for advanced groundwater reactive TREATment (in-DRAIN-TREAT)

The removal of groundwater contamination is a complex process due to the hydro-geochemical characteristics of the specific site, related maintenance and the possible presence of several types of pollutants, both organic and inorganic. In recent decades, there has been an increasing drive towards more sustainable treatment for contaminated groundwater as opposed to “intensive” treatments, i.e. with high requirements for onsite infrastructure, energy and resource use. In this study, a new remediation technology is proposed, combining the use of advanced drainage systems with adsorption processes, termed “In-situ reactive DRAINage system for groundwater TREATment” (In-DRAIN-TREAT). By taking advantage of the groundwater natural gradient, In-DRAIN-TREAT collects the contaminated groundwater via a drainage system and treats the polluted water directly into an active cell located downstream, avoiding external energy inputs. Preliminary results indicate the applicability and high efficiency of In-DRAIN-TREAT when compared with a permeable reactive barrier (PRB). In-DRAIN-TREAT is applied to remediate a theoretical aquifer with low permeability, contaminated by a 13 m wide hexavalent chromium (CrVI) plume. This is achieved in less than a year, via a drain DN500, 32 m long, a 30 m3 treatment cell filled with activated carbon and no energy consumption. A comparison with permeable barriers also shows a preliminary 63% volume reduction, with a related 10% decrease of remediation costs

Experimental investigations and numerical modelling of in-situ reactive caps for PAH contaminated marine sediments

The present study compared numerical modelling and experimental investigations to evaluate the effectiveness of in-situ reactive capping for marine sediments contaminated by polycyclic aromatic hydrocarbons (PAHs). As a case study, sediment samples from Mar Piccolo (Italy) were analyzed and experiments were undertaken using batch columns. Two types of capping amendments were tested: AquaGate® + 5 % of powdered activated carbon (AG PAC) and Organoclay Reactive Core Mat (OC RCM). The column tests were carried out for 20 days, obtaining a short-term PAH distribution for three cases analysed, which compared the application of the two caps with no intervention. In parallel, in order to evaluate the intervention long term efficacy, an ad-hoc multilayered model predicting PAH concentrations into the sediments and the overlying water column was developed and validated with the experimental results. Both capping systems considerably reduced PAH concentrations in the overlying water, with the highest performance seen in AG PAC for benzo[a]pyrene (99 %) and anthracene (72 %); results also confirmed in the model predictions. In addition, the numerical simulations indicated a good efficiency of both caps over time, obtaining PAH values below the threshold limit in the long term. Although further experiments need to be developed accounting for multiple contamination competitiveness

Pump-and-treat configurations with vertical and horizontal wells to remediate an aquifer contaminated by hexavalent chromium

Pump-and-treat technology is among the most used technologies for groundwater remediation. While conventional, vertical wells (VRWs) are well-known and used from long time, horizontal wells (HRWs) have been explored for remediation technologies only in last few decades. HRWs have shown to outperform vertical wells in terms of versatility, productivity and clean-up times under certain conditions. In this paper, the efficacy of an innovative pump-and-treat (P&T) configuration for groundwater remediation obtained by adopting either VRWs or HRWs technology is comparatively tested. A 3D transient finite element model of an unconfined aquifer containing a hexavalent chromium (Cr(VI)) contamination plume is considered to compare a single horizontal well configuration vs a range of spatially-optimised arrays containing vertical wells. A sensitivity analysis aimed at finding the best configuration to minimise the remediation time and the related cost is carried out by comparing different well diameters, D, pumping rates, Q, and position of wells. A comparative cost analysis demonstrates that, for the examined case-study, a single HRW achieves the clean-up goals in the same time span as for a greater number of vertical wells, but at higher price due to the excavation costs

Experimental and simulation study of the restoration of a thallium (I)-contaminated aquifer by Permeable Adsorptive Barriers (PABs)

Permeable Adsorptive Barriers (PABs), filled with a commercial activated carbon, are tested as a technique for the remediation of a thallium (I)-contaminated aquifer located in the south of Italy. Thallium adsorption capacity of the activated carbon is experimentally determined through dedicated laboratory tests, allowing to obtain the main modelling parameters to describe the adsorption phenomena within the barrier. A 2D numerical model, solved by using a finite element approach via COMSOL Multi-physics®, is used to simulate the contaminant transport within the aquifer and for the PAB design. Investigations are carried out on an innovative barrier configuration, called Discontinuous Permeable Adsorptive Barrier (PAB-D). In addition, an optimization procedure is followed to determine the optimum PAB-D parameters, and to evaluate the total costs of the intervention. A PAB-D made by an array of wells having a diameter of 1.5 m and spaced at a distance of 4 m from each other, is shown to be the most cost-effective of those tested, and ensures the aquifer restoration within 80 years. The simulation outcomes demonstrate that the designed PAB-D is an effective tool for the remediation of the aquifer under analysis, since the contaminant concentration downstream of the barrier is below the thallium regulatory limit for groundwater, also accounting for possible desorption phenomena. Finally, the best PAB-D configuration is compared with a continuous barrier (PAB-C), resulting in a 32% saving of adsorbing material volume, and 36% of the overall costs for the PAB-D

Evaluating different soil amendments as bioremediation strategy for wetland soil contaminated by crude oil

This study evaluated the efficacy of using Tween 80 surfactant (TW80) and food-waste anaerobic digestate fibre (FWAD) as soil amendments for the remediation of wetlands contaminated by crude oil. A 112-day mesocosms experiment was carried out to simulate hydrocarbon degradation under typical acidified wetland conditions. Soil was spiked with 50,000 mg kg−1 crude oil and TW80 and FWAD were added to mesocosms at 10%, 20% and 30% w/w. The soil basal respiration, microbial community dynamics, environmental stress, alkanes, and PAHs degradation were monitored throughout the mesocosm experiment. Amending the mesocosms with FWAD and TW80 enabled the recovery of the soil microbial activities. This was evidenced by soil basal respiration which was the highest in the 30% FWAD and 30% TW80 mesocosms and translated into increased degradation rate of 32% and 23% for alkanes, and 33% and 26% for PAHs compared to natural attenuation, respectively. Efficient total hydrocarbon degradation was achieved in soil mesocosms with 30% FWAD and 30% TW80 at 90% and 86.8%, respectively after 49 days. Maize seed germination results showed significant improvement from 29% to over 90% following the FWAD and TW80 treatment

The role of fluid catalytic cracking in process optimisation for petroleum refineries

Petroleum refining is a chemical process in which the raw material (crude oil) is converted to finished commercial products for end users. The fluid catalytic cracking (FCC) unit is a key asset in refineries, requiring optimised processes in the context of engineering design. Following the first stage of separation of crude oil in a distillation tower, an additional 40 per cent quantity is attainable in the gasoline pool with further conversion of the downgraded product of crude oil (residue from the distillation tower) using a catalyst in the FCC process. Effective removal of sulphur oxides, nitrogen oxides, carbon and heavy metals from FCC gasoline requires greater separation efficiency and involves an enormous environmental significance. The FCC unit is primarily a reactor and regeneration system which employs cyclone systems for separation. Catalyst losses in FCC cyclones lead to high particulate matter emission on the regenerator side and fines carryover into the product on the reactor side. This paper aims at demonstrating the importance of FCC unit design criteria in terms of technical performance and compliance with environmental legislation. A systematic review of state-of-the-art FCC technology was carried out, identifying its key technical challenges and sources of emissions. Case studies of petroleum refineries in Nigeria were assessed against selected global case studies. The review highlights the need for further modelling investigations to help improve FCC design to more effectively meet product specification requirements while complying with stricter environmental legislation