Chemical Engineering Research Bulletin

Shahjalal Fertilizer Company Limited (SFCL): in Retrospect

AKMA Quader — Wed, 23 Jun 2021 00:00:00 +0000

This is a reflection on the implementation of Shahjalal Fertilizer Project (SFP) what is today Shahjalal Fertilizer Co. Ltd. (SFCL). This deals with a wide range of issues covering technical, contractual, and administrative involving SFP, General Contractor, sub-contractors, Process Licensors and vendors. These arose because of mindset, interpretation of contract clauses, inexperience, expectation and frustration of both Owner and General Contractor. Lessons learned would enable BCIC to undertake such projects in future by avoiding pitfalls and missteps of SFP.

Chemical Engineering Research Bulletin 21(2020) 1-13

Biochar Production from Waste Biomass using Modular Pyrolyzer for Soil Amendment

KM Nazmus Sakib, SM Nafiz Ahmed, Abdullahil Mubdee, Kawnish Kirtania — Wed, 23 Jun 2021 00:00:00 +0000

Nowadays, researchers have found many applications of biochar due to its large surface area, ion and water holding capacity, sheltering possibility for microbes beneficial for the plants’ nutrition intake, carbon sequestration etc. Among several waste biomass feedstock, agricultural waste is a suitable source of biomass for the biochar production. So, in this study, a low cost, modular technology was proposed that can be used at the consumer end to produce biochar of satisfactory quality. In this technology, no separate inert gas feed was required, thereby lowering the cost and complexity of the system. The reactor was designed in a way that most of the oxygen got consumed at the beginning of the process and the residual nitrogen from air maintained a pseudo-inert environment. As potential feedstock for biochar, rice husk and wood chips were considered in this study. Also, to evaluate the quality of produced biochar, proximate analysis and calorific value were measured. The char yields were found to be between 20 to 40%. For rice husk (powdered and granular) and wood chips, the volatile content (%) were 15.88, 19.69 and 25.47 respectively meaning most of the volatiles were released during devolatilization. It was found that biochar can be produced from agricultural waste using this method by farmers in the field without any additional equipment, and the pyrolyzer is modular and portable. Finally, the biochar could be used for soil replenishment. Further work is ongoing on the char characterization to realize the full potential of biochar production from waste biomass.

Chemical Engineering Research Bulletin 21(2020) 14-19

Modeling and Optimizing the Parameters of Condensers in Split Type Room Air Conditioners

Wed, 23 Jun 2021 00:00:00 +0000

Split type room air conditioners (RACs) are very common nowadays. In Bangladesh, RAC manufacturers employ trial-error prototyping techniques in their design to increase the efficiency of RACs and the profitability of the plant. Computer modeling can be a great help to reduce the cost in the R&D stage to find the optimum design of RACs. In this study, modeling of heat transfer in the condenser of split type RACs employing the techniques of Computational Fluid Dynamics (CFD) was performed. To reduce the computational load the geometry was divided into small sections and geometric symmetries were also taken into account. For the simulation, the geometry and other relevant data were set in such a way so that they commensurate closely with real industrial data. An example data set for validation of simulation results were obtained from an AC manufacturer company, Elite Hitech Industries Ltd. The geometry was built using meshing techniques. Copper and aluminum were selected as materials for tubes and fins, respectively. R-22 was chosen as the refrigerant. Heat transfer and fluid flow were modeled using non-isothermal flow in a multi-physics environment. The main assumptions employed are laminar flow, extra coarse mesh size, constant air inlet temperature, perfect insulation between system and surroundings, and thin layer fins. The temperature distribution and heat transfer efficiency in the condenser, the impact of different refrigerant flow arrangements in the tubes have been studied in detail. This study leads to the finding of efficient refrigerant flow arrangements from the viewpoint of maximum heat transfer.

Chemical Engineering Research Bulletin 21(2020) 20-25

Performance Analysis of different Anode Materials of a Double Chambered Microbial Fuel Cell

Abdullah Al Moinee, Nahid Sanzida — Wed, 23 Jun 2021 00:00:00 +0000

Microbial fuel cells (MFCs) are bio-electrochemical systems (BES) that can oxidize and convert biodegradable wastes directly into electricity via microbial metabolism. Since the oxidation half-cell of an MFC consists of the biodegradable electrolyte and anode, the selection of the right anode materials is essential to optimize the performance of MFCs. Anode acts as the governing support for the growth of biofilm to transfer the electrons. In general, anode materials must have a reasonable surface area for bacterial growth, good conduction, excellent biocompatibility, chemical stability, high mechanical strength, and low cost. In this work, graphite bar, aluminum foil, and carbon cloth were tested as an anode. The comparative performances of them were analyzed in a double chambered MFC containing industrial wastewater with respect to the power density and waste removal efficiency of MFCs. The carbon cloth anode provided better output than graphite bar and aluminum foil. The 10 days of batch operation for carbon cloth anode resulted in a maximum of 672.34 mWm^-3 power density and 52.20% removal of chemical oxygen demand (COD).

Chemical Engineering Research Bulletin 21(2020) 26-31

Study of Hibiscus Rosasinensis as a Feedstock for Natural Colorant to Food

Azmain A Akash, Fahim R Choudhury, Iqbal Hossain — Wed, 23 Jun 2021 00:00:00 +0000

The application of coloring to food is widespread around the globe. Some of the artificial food colorants are highly carcinogenic. Exploration of new natural colorants has therefore been under research. The present study was aimed to evaluate Hibiscus rosasinensis flower as a potential feedstock for natural colorant. Crude anthocyanin was first extracted from Hibiscus rosasinensis flower using a Soxhlet apparatus with ethanol as the solvent. Flower to solvent ratio was found to affect the extraction largely. A ratio of 1:20 was found to give the highest fraction of extract. The cytotoxicity of crude anthocyanin extract was subsequently determined by Brine Shrimp Lethality Test. The LC50 value for crude anthocyanin extract was 2332 μg/ml, which is higher than the required minimum threshold value. Hence the findings of present study would be useful towards the application of H. rosasinensis flower as a feedstock for natural colorant to food.

Chemical Engineering Research Bulletin 21(2020) 32-36

Parametric Study on Co-Feeding of Municipal Solid Waste and Coal in an IGCC Power Plant with Pre-Combustion Carbon Capture

Wed, 23 Jun 2021 00:00:00 +0000

Municipal solid waste (MSW) is one of the top contributors in greenhouse gas (i.e. methane) emissions - particularly from landfill disposals. However, it could be a remarkable source of renewable energy. In Bangladesh, generation of municipal solid waste is at least 2.7 million tonne per year in the major cities, implying a heavy environmental burden. On the other hand, there are several coal-based power plants are in the pipeline to meet the increasing energy demand in Bangladesh with the potential of significant CO₂ emission. To find a remedy to the above situation, a power plant using Integrated Gasification and Combustion Cycle (IGCC) technology with pre-combustion carbon capture is considered in this study. IGCC has the advantage of producing high quality syngas from a wide variety of feed and assists in the capture of CO₂ at a lower cost while providing high electric efficiency. The power plant was simulated by commercial simulation packages (Aspen PLUS™ and Aspen HYSYS™) using MSW and bituminous coal (Indonesian) as a combined feed. With a feed rate of 1800 tonne per day, Syngas produced from an entrained flow type gasifier was then treated for CO₂ removal using mono-ethanol amine (MEA) solvent after necessary shift in a high temperature shift reactor. About 91% efficiency was achieved in the shift reactor while the CO₂ capture efficiency was varied for this study from 30% to 85%. Further parametric variation was studied by varying the moisture content of MSW and MSW to coal feed ratio. Through combustion of the H2 rich syngas in a gas turbine and subsequent steam cycle with reheat resulted in 125 MW of electricity at an efficiency of 28.95% while capturing 50% of the CO₂ generated in the process for an MSW to Coal feed ratio of 1:1. With variation in moisture content especially during monsoon season, the plant efficiency could be affected remarkably. On the other hand, it was observed that the energy requirement varied from 6 to 8 MW for every 10% increase in CO₂ capture quantity. Overall, by capturing 50% of the generated CO₂, it is possible to reduce the emission of a same size ultra-supercritical coal-based power plant from about 700 kg CO₂/MWh to about 360 kg of net CO₂/MWh incorporating co-feeding and pre-combustion capture in an IGCC power plant.

Chemical Engineering Research Bulletin 21(2020) 37-42

Preparation and Physico-Chemical Properties Evaluation of Biodiesel from Pithraj (Aphanamixis Polystachya)Seeds available in Bangladesh

Hd. Razu Ahmmed, Md Ikramul Hasan, Md Golam Mortuza, Mohammad Ismail — Wed, 23 Jun 2021 00:00:00 +0000

In this study, Pithraj (Aphanamixis polystachya) seed (PS) oil was used to produce biodiesel via trans-esterification process. The PS oil was extracted from seed using a soxhlet solvent extraction technique and the effect of temperature and heating rate on product distribution was investigated. The PS oil was pretreated (esterified) to combat the saponification reaction and other associated problems e.g., phase separation. The transesterification reactions were carried out and the optimum biodiesel yield was found 93.87%, when the reaction condition was as follows: addition of 50 wt.% methanol, 0.8 wt.% NaOH (both are on the basis of wt.% of PS oil addition), 60 °C reaction temperature and 90 min reaction time. Biodiesel produced from PS oil was characterized by various physico-chemical means and compared with international standards. The use of the produced biodiesel in blend with commercial diesel will bring a remarkable change in fuel economy of the country, will ensure a clean and safe environment and will demonstrate a way for ‘Waste to Energy’.

Chemical Engineering Research Bulletin 21(2020) 43-48

Application and Performance Evaluation of Model Predictive Controllers on Driving Force Based Reactive Distillation Processes

Wed, 23 Jun 2021 00:00:00 +0000

In this work, integrated design and control of Reactive Distillation (RD) column operating under Model Predictive Controller (MPC) is presented. At first, a design target is defined, and the RD column is designed based on the element concept at the maximum driving force. After that, the steady state simulation is carried out in ASPEN PLUS that satisfies the design target. Next, the flow driven dynamic system is linearized in ASPEN PLUS Dynamics and the state space matrices are obtained. Using the matrices, MPC closed-loop simulation is carried out in MATLAB. To quantify both the steady state and dynamic operation, a multi objective function is defined that takes into account both the design (total energy consumption, total carbon footprint), and the control performance (Integral Absolute Error, total variation of input, relative gain array, Niederlinski Index). For further verification, an alternative design based on non-maximal driving force is also obtained, and the corresponding steady state and dynamic simulation is performed. The closed-loop performance of MPC controller under feed disturbance shows that the process that is designed at the maximum driving force exhibit better control performance compared to the design alternative that does not take into account the maximum available driving force.

Chemical Engineering Research Bulletin 21(2020) 49-53

Implementation of Rainwater in Preparatory Processes as well as Dyeing of Knitted Cotton Fabric and Compare the Effects with Ground Water

Md Samiul Alom, Farjana Badhon, Shompa Rani Halder, Tonmoy Saha — Wed, 23 Jun 2021 00:00:00 +0000

Textile industries are very much intensive to water. A large amount of water is consumed every day during various textile processes and one of the main sources of this water is groundwater. This project aimed to work with rainwater which can be an alternative source of groundwater. In this project, the quality of rainwater was evaluated first and matched with the standard. From different tests such as turbidity, water hardness, amount of dissolved solids, and iron content, we found that the rainwater achieved the standard level of dye house water supply. After that, different wet preparatory processes, as well as dyeing of cotton fabric were carried out using rainwater. After completion of each process, evaluation was carried out such as weight loss percentage and absorbency for scouring, whiteness index for bleaching, and colour fastness tests of dyed fabric. The results were excellent compared with conventionally groundwater treated fabric.

Chemical Engineering Research Bulletin 21(2020) 54-59

Safety Performance Assessment of Hazardous Chemical Facilities in Bangladesh Using Indexing Approach

Uddipta Mondal, Nishat Salsabil, Easir A Khan — Wed, 23 Jun 2021 00:00:00 +0000

This paper presents evaluation of safety performance of three hazardous facilities based on current safety practice by measuring their safety weighted hazard indices (SWeHI) of multifarious units of chemical process and what can be done to avoid any potential accidents in context of Bangladesh. Assessing hazard potential over safety procuration is a key indicator of how well a facility is prepared to reduce its vulnerability. The risks associated with hazardous facilities are always greater in a country like Bangladesh as the safety issues are not often been prioritized by its key stakeholders. In recent years, there were number of deadly accidents occurred in the chemical industries and storage warehouses which resulted multiple fatalities and significant property damage. The accident could be avoided using proper safety protocols in those facilities. Here safety performance of three facilities was assessed based on survey data. These facilities deal with flammable, explosive and toxic chemicals. This index is on the basis of fire & explosions properties and toxic release properties as well as the safety precautions against it. It helps professionals to identify the overall hazard potential and distinguish less protected units from other well operated units. The paper features on an approximate yet workable assessment of risks at a low cost and based on the current safety practices.

Chemical Engineering Research Bulletin 21(2020) 60-68

Occupational Risk Assessment in RMG, Textile and Ship Breaking Industries of Bangladesh

Wed, 23 Jun 2021 00:00:00 +0000

In this study occupational risk assessment in Readymade Garments (RMG), Textile and Ship Breaking Industries of Bangladesh was carried out utilizing accident database of Department of Inspection for Factories and Establishments (DIFE), Ministry of Labour and Employment. The study focused on the workplace incidents reported to DIFE from 2016-2018 in RMG, Textile and Ship Breaking industries of Bangladesh. The risk analysis was conducted based on severity and likelihood of events, the latter comprising: frequency of exposure to the hazard, duration of exposure to the hazard, probability of occurrence of a hazardous event, and technical and human possibility of avoiding or limiting the harm. To carry out the assessment, survey data including working time, accident frequency, cause of accident, nature of injury, use of personal protective equipment (PPE), health safety policy, first aid facility etc. were collected from DIFE. The risk scores and economic losses due to accidents in different years for each industry were estimated. The overall risk scores estimated for RMG and Textile industry were found to be higher than that for Ship Breaking industry. However, in Ship Breaking industry 41.3% of total incidents are of very high-risk, which is much higher than the percentage of such incidents in RMG or Textile industry. It was also found that the total compensation provided to the workers as reported to DIFE is 58.5% less of the estimated cost based on the fatality and type of injuries.

Chemical Engineering Research Bulletin 21(2020) 69-76

Effect of Single and Mixed Inoculum on Biogas Yield During Dry Anaerobic Digestion of Organic Municipal Solid Waste

Wed, 23 Jun 2021 00:00:00 +0000

Organic municipal solid waste (OMSW) - a potential energy source - is creating serious environmental hazards across Bangladesh, but it can be digested for biogas production to meet the ever-increasing energy demand of the country. The present study applied the dry anaerobic digestion (DAD) process for biogas production from OMSW with inoculum cow manure (CM) and anaerobic sludge (AS) in single and mixed modes. The performance of the DAD process was evaluated in batch digesters with a multilayer inoculum flow pattern maintained at the constant mesophilic condition of 37 °C. Firstly, CM and AS were studied individually, and later on, both of them were used together in different ratios (AS:CM = 1:1, 1:2, 1:3, and 2:1) to maximize the biogas yield from the DAD process. CM alone produced a total of 2.91 ml biogas/ g of biomass over 35 days of DAD while this yield was increased to 3.19 ml/g for mixed inoculum at the ratio of 1:3. These results imply that mixed-mode inoculums would be a promising option in the DAD process for biogas production which will reduce both the energy scarcity and the burden of municipal solid waste (MSW) management.

Chemical Engineering Research Bulletin 21(2020) 77-81

Heat and Mass Transfer Predictive 3D Model of Mango Kernel During Convection Oven Drying Process

Md Shafiul Islam, Md Sumon Ali, Mohammad Nurur Rahman, Pabitra Chandra Das — Wed, 23 Jun 2021 00:00:00 +0000

A large number of mangoes are utilized in process industries which produce a large amount of mango kernel that can be utilized effectively as a by-product. Processing and utilization of mango kernel flour is getting more scientific interest day by day. Drying is one of the major operations of flour processing where the moisture loss and heat transfer phenomena across the different portions of the products have to be pre-defined for better drying accuracy. The study was conducted to define a compatible predictive model that represents a 3D expression of heat penetration through the mango kernel slice (MKS) and moisture losses during drying with convective oven dryer using COMSOL Multiphysics with originated boundary conditions, excluding the changes of properties due to varying mangoes species. The model was validated using a convective drying process for varying thicknesses 4, 6 and 8 mm of MKSs having temperature elevated to 60oC and 1 ms-1 air velocity up to 5 hr. The developed model was concurred and correlated well with the experimental data and can be used in describing heat and mass transfer phenomena while drying the mango kernel.

Chemical Engineering Research Bulletin 21(2020) 82-87

Life-Cycle Impact Assessment of Fossil Power Plants with and without Co2 Capture Evaluating the Possibility of Co2 Utilization

Nafisa Tarannum, Banhee Shikha Roy Brishti, Sadia Siddika Dima, Kawnish Kirtania — Wed, 23 Jun 2021 00:00:00 +0000

The CO₂ emission is more than 36 billion tons per year in global scale. As carbon dioxide emission raises global temperature by trapping solar energy in the atmosphere, research is ongoing to facilitate the capture of CO₂ with high efficiency. While CO₂ footprint of Bangladesh is relatively low, with upcoming coal-based power plants (>17000 MW) in the next decade, fossil CO₂emission will increase significantly. To understand the underlying benefit of CO₂ capture process, cradle-to-gate life cycle impact assessment (LCIA) of the power plants using fossil sources (e.g. natural gas, coal) can provide an in-depth insight. This paper aims to conduct life cycle impact assessment on natural gas and coal (sub critical and supercritical) fired power plants with and without CO₂ capture facility for comparison of overall impact on the environment. An open source software titled OpenLCA was used to carry out LCIA and study different impact parameters (i.e. green-house gas emission, toxicity and ozone layer depletion). It was found that the CO₂ emission from super-critical pulverized coal (SCPC) and sub-critical pulverized coal (Sub-PC) fired power plants could be brought down by more than 80% using CO₂ capture facility. Along with capture, it is equally important to ensure proper sinks for this captured CO₂. As Bangladesh has no dedicated geological reservoir for CO2 storage, potential sink for captured CO₂ could be immediate utilization after capture. This paper also presents preliminary results on utilizing CO₂ through mineralization during preparation of alternative admixture and construction materials. Due to the ever-growing real-estate sector of Bangladesh, there is great potential in capturing and utilizing CO₂ through construction activities.

Chemical Engineering Research Bulletin 21(2020) 88-93

Effect of Wood Saw Dust and Chopped Jute Fiber on the Tensile Properties of Epoxy Based Polymer Composite

MS Haque, MA Islam — Wed, 23 Jun 2021 00:00:00 +0000

Polymer composites play a good role in various engineering applications because of their good combination of various properties such as unbeatable light weight, relatively high strength, ease of fabrication, corrosion resistance, high impact strength, design flexibility, dimensional stability, non-conductive properties, etc. So, polymer composites have attracted big attention from world-wide researchers. Epoxy based composite are largely used in load bearing application such as aerospace and automobile industries due to their good mechanical properties and corrosion resistance. In this research work, epoxy-based composites were developed by adding 5% wood saw dusts or 2 mm size chopped jute fibers. The jute fibers and saw dusts were added to gain some special property such as biodegradability. The developed composites were then characterized by tensile tests. Experimental results revealed that 5% saw dusts additions have no significant effect on the tensile strength of epoxy-based polymer composites. However, chopped jute fibers have been found to decrease the strength as well as fracture morphology noticeably.

Chemical Engineering Research Bulletin 21(2020) 94-98

Study of Fire Growth Behavior in a Residential Apartment using Fire Dynamic Simulator

Fahim Shahriar Sakib, Riazuddin Ahmed, Easir A Khan — Wed, 23 Jun 2021 00:00:00 +0000

Fire accidents are very frequent and a major issue in Bangladesh in recent times. In this paper fire growth behavior in an apartment building is studied through a numerical analysis using Fire Dynamic Simulator (FDS). A model apartment with fixed combustibles was created using FDS. The fire growth characteristics were studied and heat release rate, the rise of temperature, toxic gas dispersion and human evacuation were assessed. The fire was generated using a burner function. Computational analysis results from those models were analyzed and discussed. The relationship of wind and ventilation effect with time helps to predict the fire growth behavior in different location of the apartment. Evacuation modeling was created to illustrate the effect of evacuation time and fractional effective dose (FED) for different types of agents. FED is the summation of toxic gas consumption which is important for safe evacuation. The results show that the ventilation effect releases the heat and makes the apartment less vulnerable. Elderly people took more time for total evacuation than other groups that related to FED percentage. The idea of critical door length is demonstrated for safe evacuation during fire emergencies.

Chemical Engineering Research Bulletin 21(2020) 99-105

Heavy Metal Contamination and Ecological Risk Assessment in the Soil of Tannery Industry at Savar

Sabiha Momtaz Tisha, Tasnia Rahman Chowdhury, Md Delwar Hossain — Wed, 23 Jun 2021 00:00:00 +0000

Heavy metal contamination in soil is considered a global crisis and its bulk proportion are in developing countries like Bangladesh. Five heavy metals such as Cd, Cr, Pb, Cu and Ni were investigated in the soil of Savar tannery industrial estate. The decreasing trend of metals was observed in soil as Cr>Cu>Ni>Pb>Cd. According to US EPA guideline, Cr was heavily polluted at the selected locations. Cu was highly polluted, whereas Cd and Pb were not polluted and Ni was moderately polluted. On the basis of Pearson’s correlation Cd-Pb, Cd-Cu, Cu-Ni, Ni-Cu, Ni-Pb were significantly correlated. From the pollution index, metal pollution of sediments was found in the order as Cr>Cu>Pb>Cd. Degree of contamination and modified degree of contamination were higher in the dumping zones. The geo-accumulation index for Cr showed moderate to extremely contaminated. Ecological risk arrayed in the order of Cr>Cu>Ni>Pb>Cd in the soil of study area. Geographic information system (GIS) was also used to map the spatial distribution of heavy metal contamination in the soil. This study recommended that continuous monitoring of heavy metal contamination should be directed to assess their risk in the soil of tannery industry at Savar.

Chemical Engineering Research Bulletin 21(2020) 106-113

Impact of Trans-Boundary Pollution (PM-2.5) on the Air Quality of Dhaka City in Bangladesh

Musfekur R Dihan, SM Abu Nayeem, MAA Shoukat Choudhury — Wed, 23 Jun 2021 00:00:00 +0000

Clean air is a basic need of human beings for its existence. In recent years, air pollution in city areas, especially in Dhaka and Chittagong, has become a significant threat to health and well-being. Dhaka is found to suffer a high level of pollution during the dry season, which is from November to April, especially for Particulate Matter, PM2.5, concentration. From December to February this situation is found to be the worst crossing the WHO guidelines and National Ambient Air Quality Standard. Bangladesh is surrounded by countries with the fastest-growing economy like India and China who use coal-burning technologies for different purposes such as producing power and running mills. They release the lion’s share of the air pollutants in South Asia and these pollutants easily get transported to neighboring countries. This is known as transboundary pollution. This study investigates the contribution of transboundary transportation of PM-2.5 in the air quality of Dhaka city. Ninety-Six hours of air mass back trajectories were computed using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT-4) model and those trajectories were grouped into 6 clusters. Probability calculation showed that Dhaka city air has a higher probability of getting pollutants from long-range sources when air masses traveled through North, West, and North-West direction covering the North Eastern and North-Western territories of India, Nepal, and its neighboring areas. Concentration Weighted Trajectory (CWT) analysis also supported that those areas could be potential sources of getting unwanted PM-2.5 on our atmosphere.

Chemical Engineering Research Bulletin 21(2020) 114-120

Surrogate Modeling & Optimization of a Nonlinear Batch Reactor by Polynomial Chaos Expansion

Nishat Tasnim, Mysha Momtaz, Nahid Sanzida — Wed, 23 Jun 2021 00:00:00 +0000

The paper presents a computationally efficient approach to develop a nonlinear data driven input/output model between the finite-time control trajectories and the quality index at the end of the batch. Polynomial chaos expansion (PCE) was applied to produce the approximate representation of the full process model of a nonlinear batch reactor with the reaction scheme .A-->^k1B-->^k2C A surrogate model was developed to estimate the dependence of intermediate product (B) concentration at the end of the batch on the temperature trajectory applied during the reaction. The surrogate model was then validated for its performance. Later, the surrogate model was used to determine the optimal temperature profile needed to maximize the concentration of intermediate product at the end of the batch. The validation and optimization results prove that the experimental data based PCE can provide a very good approximation of the desired outputs, providing a generally applicable approach for rapid design, control and optimization of batch reactor systems.

Chemical Engineering Research Bulletin 21(2020) 121-126

Technical and Economic Aspects of Reusing Textile Effluent as Process Water: A Case Study of Denim Washing Factory

Mesbah Ahmad, Majed Alam Abir, Mohidus Samad Khan — Wed, 23 Jun 2021 00:00:00 +0000

Textile and apparel industries are the major role-players in the fast-growing economy of Bangladesh. However, the textile sector consumes a large amount of water for various wet processing operations. Currently 98% of the water used by local textile factories is groundwater, which is causing depletion of ground water levels at a high rate. Considering the gravity of groundwater crisis in future, Bangladesh Government and international brands and retailers are advocating local textile factories to reuse textile effluents and implement ZLD (zero liquid discharge) option in the upcoming years. However, it is a new concept for Bangladesh textile sector, and there is limited understanding regarding technical and economic issues associated to advanced treatment and reusing textile effluent. In this paper, a case study is presented to analyse the application of advanced membrane treatment of conventional ETP (effluent treatment plant) treated water of a denim washing factory. The corresponding technical and economic issues of water recycling and reusing were also analyzed. The selected denim washing factory runs a conventional biological effluent treatment plant (ETP) which satisfies the basic requirements of national and international standards. For advanced treatment, a mobile setup of ultrafiltration (UF) and reverse osmosis (RO) unit was used at factory premises to further treat ETP treated water. The advanced treatment was carried out for three different permeate to reject ratios to observe changes in the permeate and reject water quality. Capital expenditure and operational costs were also assessed to see the economic feasibility of the approach. This study will help local textile factories with real time data to understand the technical and economic issues associated to reusing textile wastewater as process water.

Chemical Engineering Research Bulletin 21(2020) 127-132

Study of Growth Kinetics of High Lipid Content Algae in Local Environment

Wed, 23 Jun 2021 00:00:00 +0000

In recent years algae has been receiving a lot of interest as an alternate source of biofuel. Fast growth and rich lipid content make algae a great candidate for producing eco-friendly and non-toxic biodiesel. The strain Chlorella vulgaris, has shown great potential as a source of oil. To optimize the mass culture of microalgae Chlorella vulgaris, it is necessary to develop growth kinetic model of Chlorella vulgaris. This work presents a comparative study on growth kinetics of Chlorella vulgaris in batch cultures in four different media, namely- CH, modified CH, Bold’s Basal (BB), and modified Bold’s Basal (BB). Spectroscopic analysis was supported by visual change of color in the algal biomass solution and the microscopic imaging, and was validated with dry cell mass measurement in this study. The data were analyzed to produce growth curves to find exponential phase for each medium. Exponential phases are the best period to harvest the culture. Hence the duration of exponential phase and the final biomass concentration at the end of exponential phase are two important parameters to determine the most suitable medium for mass culture. In this study the overall specific growth, doubling time and biomass productivity of Chlorella vulgaris for CH, modified CH, BB and modified BB media were measured. This study will help to find a suitable media to culture Chlorella vulgaris, a high lipid content algae in the local environment. The information can be used to design a system for mass culture of the strain for biodiesel production.

Chemical Engineering Research Bulletin 21(2020) 133-138