Data-Driven Models for Estimating Dust Loading Levels of ERV HEPA Filters

With increasing global concerns regarding indoor air quality (IAQ) and air pollution, concerns about regularly replacing ventilation devices, particularly high-efficiency particulate air (HEPA) filters, have increased. However, users cannot easily determine when to replace filters. This paper proposes models to estimate the dust loading levels of HEPA filters for an energy-recovery ventilation system that performs air purification. The models utilize filter pressure drops, the revolutions per minute (RPM) of supply fans, and rated airflow modes as variables for regression equations. The obtained results demonstrated that the filter dust loading level could be estimated once the filter pressure drops and RPM, and voltage for the rated airflow were input in the models, with a root mean square error of 5.1–12.9%. Despite current methods using fewer experimental datasets than the proposed models, our findings indicate that these models could be efficiently used in the development of filter replacement alarms to help users decide when to replace their filters.

A Hydrometallurgical Process for Cu Recovery from Printed Circuit Boards

The current study presents an effort to develop a sustainable hydrometallurgical process for the recovery of copper from waste printed circuit boards (PCBs) to be applied at local small to medium industrial units. The process aims to separate and recover copper from filter dust produced during the crushing of PCBs using a hammer mill in a recycling facility. Due to the high plastic content in the dust (approximately 30% w/w), the metal fraction was separated gravimetrically, and the material originated consisted mainly of Cu (23.8%), Fe (17.8%), Sn (12.7%), Pb (6.3%), Zn (3.4%), Al (3.3%), Mn (1.6%), and Ni (1.5%). Prior to copper recovery, the dust was leached with HCl as a pretreatment step. During this step, more than 80% of iron, zinc, and tin were leached out. The resulting solid consisted mainly of Cu (37.6%) and Fe (10.7%), leading to a copper enrichment of around 60% in the powder. The leaching of copper was conducted in a two-step process using H2SO4 as a leaching agent with the addition of H2O2 as an oxidizing agent. The experimental conditions had low energy requirements (no heating or agitation needed). The leaching of Cu reached 98%. Despite the pretreatment step, the concentration of other metals (Fe, Zn, Ni) in the pregnant solution was too high to proceed to electrowining. Therefore, the organic solvent ACORGA M5640 was selected for the extraction of copper from the pregnant solution. The extraction was conducted in two stages at pH equilibrium 1.5, and the loaded organic phase was stripped with HCl in two steps. The strip liquor was suitable for electrowinning.

Study of influence of the charge granulometric composition on the quality of burned anodes

Many factors affect the quality of produced anodes: composition and grade of raw materials, recipe, technology, operating parameters, the granulometric composition of charge materials etc. The most significant influence is from the last factor. The article provides research results on the effect of fine fractions on the quality of anodes. The research object is charge of different granulometric composition used to produce anodes at the Kazakhstan Electrolysis plant in Pavlodar. Six types of anode mass with different granulometric composition were prepared for the experiment. The anode mass was made of petroleum coke, pitch, recycled anodes, and dust from filters and grinder produced during coke treatment. Several properties of the specimens were studied. In total, six specimens were made and, specimen № 4 drew particular attention. Its granulometric composition is as following: coarse fractions – 25 %, medium fractions – 20%, fine fractions (grinder dust) – 50 %, and filter dust – 5 %. The results showed that some specifications of anodes, like gas permeability and apparent density that affect anode consumption, are improved as the fineness of dust grinding. For instance, the addition of dust fraction in the charge increases anode density from 1.542 to 1.639 kilogram per cubic decimeters and decreases gas permeability from 1.01 to 0.78 nPm. In addition, the presence of dust fraction minimizes the porosity of the anode block. The results of the investigation help adjust the optimal recipe of anode mass to obtain high-quality anodes.

KARAKTERISASI PHYSICO-THERMAL HYBRID BIOBRIKET LIMBAH BIOMASSA CANGKANG KOPI, TEMPURUNG KELAPA DAN BAKING FILTER DUST

Kebutuhan energi yang semakin meningkat dan ketersedian bahan bakar yang menipis, mendorong perlunya inovasi terbaru untuk mendapatkan sumber energi yang dapat diperbaharui melalui bahan baku yang melimpah dan berkarakteristik sebanding. Tujuan penelitian ini adalah untuk menentukan karakteristik briket yang dibuat dari limbah biomassa Cangkang Kopi (CKP), Tempurung Kelapa (TPK) dan produk samping pabrik Baking Filter Dust (BFD) dengan menggunakan perekat kanji dan oli bekas. Bahan baku limbah biomassa CKP dan TPK dikeringkan dan dikarbonisasi dalam tunggu bertutup yang minim oksigen pada suhu 200-400oC. Kemudian arang CKP dan TPK dicrusher dan diayak dengan ukuran 60/80 mesh. Pencampuran bahan dilakukan dengan penambahan perekat sebanyak 4 gram. Pencetakan biobriket dilakukan dengan menggunakan alat pencetak silinder berdiameter 3,3 cm kemudian ditekan dengan press hidraulik dengan pemberian tekanan 150 kg/cm2. Dari hasil penelitian diperoleh hybrid briket dengan range densitas 0,908-1,141 g/cm3, kadar air 1,81-4,02 %, kadar abu 3,79-7,09 %.Kata kunci : Baking filter dust, cangkang kopi, hybrid briket, oli bekas, perekat kanji, tempurung kelapa.

Organophosphate Flame Retardants in Car Dust from Thailand and Implications for Human Exposure

Organophosphorus flame retardants (PFRs) are a group of compounds frequently detected in indoor dust that pose high health risks to exposure subjects. The present study reports on the investigation of the levels and profiles of seven target PFRs in car dust samples from Thailand. The samples were collected from the discarded air conditioning (AC) filter of 14 private cars (called AC dust samples) and from the bag filter installed in vacuum cleaners of 10 car washing services (called settled dust samples) in 2019. The concentrations of 7PFRs in AC dust samples were approximately 3,800-91,000 ng/g, whereas those from settled dust samples were about 11,000 to 15,000 ng/g. Tris (2-butoxyethyl) phosphate (TBEP) was found to be the most prominent of PFRs detected in both types of car dust with the highest concentration of 39,000 ng/g for AC filter dust and 10,000 ng/g for settled dust. The main PFR contributors in both dust types were TBEP (80%, 75%), followed by Tris (2-ethylhexyl) phosphate (TEHP) (9%, 5%) and tris(1-chloro-2-propyl)phosphate (TCPP) (7%, 4%), respectively. Tris(2-chloroethyl)phosphate (TCEP) and tri cresyl phosphate (TCP) were not detected in both types of car dust and tris(1,3-dichloro-2-propyl) phosphate (TDCPP) was found only in settled dust samples. According to the results of exposure assessment to PFRs in car dust, the human exposures via ingestion for adults and toddlers ranged from 1.69×10-2 to 2.67 and 10.6 to 2,360 ng/kg/day. The human exposures via inhalation for adults and toddlers ranged from 3.27×10-4 to 5.17x10-2 and 2.58×10-1 to 40.9 ng/kg/day. The highest exposure among PFRs corresponded to TBEP for both adults and toddlers and the risk through ingestion was higher than inhalation intake. Toddlers were more exposed to PFR contaminants in comparison to adults. When comparing the estimated average daily intake (ADI) values with the reference doses (RfDs) for PFRs, it was found that exposure to PFRs in car cabins via inhalation and dust ingestion is unlikely to have adverse human health effects.

Exposure to Phthalate and Organophosphate Esters via Indoor Dust and PM10 Is a Cause of Concern for the Exposed Saudi Population

In this study, we measured the occurrence of organophosphate esters (OPEs) and phthalates in the settled dust (floor and air conditioner filter dust) and in suspended particulate matter (PM10) from different microenvironments (households (n = 20), offices (n = 10) and hotels (n = 10)) of Jeddah, Saudi Arabia. Bis (2-Ethylhexyl) phthalate (DEHP) was the major pollutant (contributing >85% of total chemicals burden) in all types of indoor dust with a concentration up to 3,901,500 ng g−1. While dibutyl phthalate (DBP) and DEHP together contributed >70% in PM10 (1900 ng m−3), which indicate PM10 as a significant source of exposure for DBP and DEHP in different Saudi indoor settings. Tris (1-chloro-2-propyl) phosphate (TCPP) was the major OPE in PM10 with a concentration of up to 185 ng m−3 and the occurrence of OPEs in indoor dust varied in studied indoor settings. The estimated daily intake (EDI) of studied chemicals via dust ingestion and inhalation of PM10 was below the reference dose (RfD) of individual chemicals. However, estimated incremental lifetime cancer risk (ILCR) with moderate risk (1.5 × 10−5) for Saudi adults and calculated hazardous index (HI) of >1 for Saudi children from DEHP showed a cause of concern to the local public health.

The Efficiencies of different Dust Collectors and Characteristics of PM2.5 Water-soluble Ions in Industrial Fluidized Bed Boilers

PM2.5 were collected before and after dust collectors of five industrial fluidized bed boilers by PM2.5 sampler. The ELPI was used to monitored the number and mass concentrations of PM2.5 before and after the dust collectors, and the dust removal efficiencies of different dust collectors was analyzed. The efficiencies of electrostatic and bag filter dust collectors are high, and the efficiency of mechanical dust collector is low. NH4+, K+, Mg2+, Ca2+ cations, and F-, Cl-, NO3-, SO42-anions were analyzed by ion chromatography. It was found that the contents of Ca2+ and SO42-were higher in PM2.5 samples, and the contents of Ca2+ and SO42-were different among different boilers, The content of Mg2+ in cations is relatively low, the content of F- in anions is relatively low, and NO3-is not detected in many samples.