Terephthalic Acid Manufacturing Research Articles

Biodegradation of purified terephthalic acid manufacturing effluent from a petrochemical industry

Biodegradation of purified terephthalic acid manufacturing effluent from a petrochemical industry

Biodegradation of purified terephthalic acid manufacturing effluent from a petrochemical industry

Purified terephthalic acid (PTA) is the raw material for polyester fibres, plastics, coating and adhesives. Its manufacture generates large volumes of effluent with high concentration of terephthalic acid (500-600 ppm), a critical pollutant. In this study a mixed culture made up of five types of bacteria, derived from the effluent treatment plant (ETP) sludge was used to aerobically treat the PTA effluent, removing all the benzoates [4-carboxybenzyl alcohol, isophthalic acid, terephthalic acid, 4-carboxy benzaldehyde (4-CBA), benzoic acid, p-toluic acid and trimellitic acid] which contribute to its chemical oxygen demand (COD). The study included optimisation of pH (6-9), pH neutralisers and biomass concentration (≥2,000 ppm Mixed liquor suspended solids) for achieving 94–95% COD removal in 72–96 h, the results being supported by HPLC analysis. Metals (Co, Mn and Mg) reduced significantly (88%, ~100% and 83%, respectively), being utilised for growth or getting sequestered in the biomass. Characterisation of the five pure cultures was carried out.

Characteristics of Dust Explosion in Dioctyl Terephthalic Acid Manufacturing Process

디옥틸테레프탈산(DOTP) 제조공정은 분말형태의 테레프탈산(PTA) 주원료와 옥탄올(Octanol)의 에스테르화 반응을 통해 플라스틱 가소제를 생산하는 공정이다. 본 연구에서는 이 공정의 반응기 내에 가연성 용제나 유증기가 존재하고 있는 상태에서 분말형태로 맨홀에 직접 투입하는 테레프탈산의 분진폭발 특성에 관하여 고찰하였다. 분진의 입경과 입도분포 분진특성 실험을 하였고, 화재·폭발특성과 발화온도를 추정하기 위한 분진의 열분해 특성을 조사하였다. 또한 폭발민감도를 평가하기 위한 최소점화에너지 실험을 실시하였다. 실험결과 테레프탈산의 분체 특성은 평균입경이 143.433 μm으로 나타났다. 이러한 입경과 입도분포 조건에서 실시한 열분석으로부터 분진의 발화온도는 약 253℃로 나타났다. 테레프탈산의 폭발민감도를 알기 위해 조사한 폭발하한 농도(LEL)는 50 g/m3으로 측정되었다. 폭발민감도를 나타내는 최소점화에너지(MIE)는 (10 < MIE < 300) mJ로 나타났으며, 점화 확률에 기반하여 추산한 최소점화에너지 추정값(Es)은 210 mJ로서 충분한 점화원이 있는 경우 폭발할 수 있음을 알 수 있었다. 또한 폭발피해 예측에 필요한 폭발강도 특성을 조사한 결과, 테레프탈산 분진의 최대폭발압력(Pmax), 최대폭발압력상승속도[□max]는 각각 7.1bar, 511 bar/s로 나타났다. 분진폭발지수(Kst)는 139 mbar/s로 분진폭발등급 St 1에 해당되는 것으로 나타났다.

NARX modeling for real-time optimization of air and gas compression systems in chemical processes

This study considers the Nonlinear Autoregressive eXogenous Neural Net model (NARX NN) based real-time optimization (RTO) for industrial-scale air & gas compression system in a commercial terephthalic acid manufacturing plant. NARX model is constructed to consider time-dependent system characteristics using actual plant operation data. The prediction performance is improved by extracting the thermodynamic characteristics of the chemical process as a feature of this model. And a systematic RTO method is suggested for calculating an optimal operating condition of compression system by recursively updating the NARX model. The performance of the proposed NARX model and RTO methodology is exemplified with a virtual plant that simulates the onsite commercial plant with 99.6% accuracy. NARX with feature extraction model reduces mean squared prediction error with the actual plant data 43.5% compared to that of the simple feed-forward multi-perceptron neural networks. The proposed RTO method suggests optimal operating conditions that reduce power consumption 4%.

Genomic expression profiles in liver of mice exposed to purified terephthalic acid manufacturing wastewater

DNA micorarray was used to analyze hepatic transcriptional profile of male mice ( Mus musculus) after 35-d intragastric perfusion treatment with purified terephthalic acid (PTA) manufacturing wastewater. Haematological analysis demonstrated that the levels of glutamyl transferase and lactate dehydrogenase in serum were significantly decreased, and DNA microarray showed that a total of 306 genes were differentially expressed in PTA wastewater-treated mice. According to Kyoto encyclopedia of genes and genomes pathway database, the differentially expressed genes were mainly grouped to metabolic pathways (58 genes) and biological processes (101 genes). PTA wastewater had significant impacts upon metabolisms of lipid, carbohydrate, amino acid, vitamin and nucleotide. Several signal transduction pathways are most susceptible to PTA wastewater, including mitogen-activated protein kinases, Janus kinase/signal transducers and activators of transcription and calcium signaling pathways. Potential public health problems may arise from the discharge of PTA wastewater into the environment.

Toxicity of purified terephthalic acid manufacturing wastewater on reproductive system of male mice ( Mus musculus)

Reproductive toxicity of purified terephthalic acid (PTA) manufacturing wastewater on the male mice ( Mus musculus) was investigated after 35-day intragastric perfusion treatment with the wastewater. Fluorescein diacetate and propidium iodide staining, and flow cytometry were used to assess the toxicity of PTA wastewater on spermatogenic cells. PTA wastewater induced significant variations in the relative percentages of immature haploid, diploid, tetraploid and S-phase spermatogonia. Percentage of viable spermatogenic cells was reduced from 93.1 ± 2.3 in control group to 90.4 ± 1.9 in the wastewater-treated group. Testicular histopathology revealed expansion of interstitial space and reduction in the number and size of Leydig cells induced by the wastewater, which was further certified by the decrease (10.6%) in relative testes weight and the increase (101.3%) in sperm shape abnormality in the wastewater-treated group. In this study, PTA wastewater was found to have reproductive toxicity on male mice, and public health problems may potentially arise from the discharge of the wastewater into the environment.

Degradation of wastewater from terephthalic acid manufacturing process by ozonation catalyzed with Fe2+, H2O2 and UV light: Direct versus indirect ozonation reactions

In this work, terephthalic acid wastewater containing a very high chemical oxygen demand (COD=(35.0±1.8)gL−1) and possessing a dark reddish brown color (platinum cobalt unit=1400) with a pH 8.5 discharged from a terephthalic acid manufacturing plant was treated by ozonation catalyzed with Fe2+, H2O2 and UV light. To arrive at an efficient Fe2+, H2O2 and UV catalyzed ozone system (O3/H2O2/Fe2+/UV), the individual methods, viz., ozone alone (O3), UV assisted ozonation (O3/UV), H2O2 and UV assisted ozonation (O3/H2O2/UV), and Fe2+ catalyzed ozonation (O3/Fe2+) were studied to evaluate their effectiveness in decomposing the COD concentration and the three major toxic organic components, namely, terephthalic acid (TPA), isophthalic acid (IPA) and benzoic acid (BA) present in the wastewater. The first-order kinetic rate constant for the COD removal process was evaluated for comparison. The O3/H2O2/Fe2+/UV combined catalytic system showed highest oxidizing power amongst the tested methods with better COD degradation degree as high as 90% at 240min, and TPA, IPA and BA present in TPA wastewater completely destroyed within 150min. In order to assess the contribution to the overall COD elimination by the direct molecular oxidation and the indirect free radical oxidation, degradation studies were carried out for all the five optimized systems with tert-butyl alcohol as the OH scavenger. Individual contributions of the two pathways to the overall global oxidation were quantified in terms of the process rate constant; and the performance evaluation of the different ozonation systems was analyzed. Finally, the potentiality of the O3/H2O2/Fe2+/UV process as a promising pre-treatment stage to obtain more easily biodegradable molecules with lower toxicity for the subsequent anaerobic digestion of the TPA wastewater was demonstrated.

Degradability of five aromatic compounds in a pilot wastewater treatment system

Abstract Purified terephthalic acid-manufacturing wastewater was treated aerobically with the microbial fusant Fhhh in the carrier activated sludge process at a pilot wastewater treatment plant. Biodegradability of p-toluic acid (p-Tol), benzoic acid (BA), 4-carboxybenzaldehyde (4-CBA), phthalic acid (PA) and terephthalic acid (TA) was monitored. The TOC and COD loading rate of suspended solids (SS) in the sludge were 0.53 g TOC g SS−1 d−1 and 1.79 g COD g SS−1 d−1, respectively. There was significant positive correlation (P PA>4-CBA>TA>p-Tol. The prospect of using MnP-SA to predict the removal rate for the five aromatics is discussed.

Application of a Moving-Window-Adaptive Neural Network to the Modeling of a Full-Scale Anaerobic Filter Process

To explore the complex dynamics of a full-scale anaerobic filter process treating the wastewater from a purified terephthalic acid manufacturing industry, a new modeling approach based on a moving-window-adaptive neural network is proposed. The essential feature of this modeling approach is that the neural network model is automatically updated whenever a new data block is available so that it can effectively capture the slowly changing process dynamics. To elucidate the advances of the proposed method, four different modeling approaches combined with the concepts of autoregressive with exogenous (ARX) input and a finite impulse response model were evaluated and compared. During each model identification process, a modified cross-validation technique was used to avoid the overfitting problem of a neural network. Among the tested models, a moving-window-adaptive ARX neural network model showed the best prediction ability with the smallest validation error. To investigate the feasibility of this model, vari...

Optimization of the Air- and Gas-supply Network of a Chemical Plant

This paper presents a novel optimization method for the air- and gas-supply network comprising several air compression systems and air and gas streams in an industrial chemical plant. The optimization is based on the hybrid model developed by Han and Han for predicting the power consumption of a compression system. A constrained optimization problem was formulated to minimize the total electric power consumption of all the compression systems in the air- and gas-supply network under various operating constraints, and was solved using a successive quadratic optimization algorithm. The optimization approach was applied to an industrial terephthalic acid manufacturing plant to achieve about 10% reduction in the total electric power consumption under varying ambient conditions.

Application of partial least squares methods to a terephthalic acid manufacturing process for product quality control

This paper deals with an application of partial least squares (PLS) methods to an industrial terephthalic acid (TPA) manufacturing process to identify and remove the major causes of variability in the product quality. Multivariate statistical analyses were performed to find the major causes of variability in the product quality, using the PLS models built from historical data measured on the process and quality variables. It was found from the PLS analyses that the variations in the catalyst concentrations and the process throughput significantly affect the product quality, and that the quality variations are propagated from the oxidation unit to the digestion units of the TPA process. A simulation-based approach was addressed to roughly estimate the effects of eliminating the major causes on the product quality using the PLS models. Based on the results that considerable amounts of the variations in the product quality could be reduced, we have proposed practical approaches for removing the major causes of product quality variations in the TPA manufacturing process.

Modeling of Multistage Air-Compression Systems in Chemical Processes

A systematic modeling method is proposed to predict the overall efficiency and power requirement of a multistage air-compression system consisting of a multistage compressor, a multistage expander, and an electric motor/generator. First, under a lack of measurements at the interstages of the multistage compression system, a calculation method of the overall efficiency is developed based on thermodynamic compression and expansion equations. Then, the prediction structure of the overall efficiency and actual power consumption/generation rate of the compression system is presented, where either partial least-squares models or artificial neural network models can be employed to predict unknown state variables and the overall efficiency, which are, in turn, used to predict the actual power consumption/generation rate based on compression and expansion equations. Finally, to verify the proposed modeling method, it is applied to two industrial compression systems of a terephthalic acid manufacturing process, and the comparisons with measurements show excellent prediction performances both in the overall efficiency and in the actual power consumption rate. The proposed modeling method can be applied to find better operating conditions of compression systems in various chemical processes.

Catalytic supercritical water oxidation of wastewater from terephthalic acid manufacturing process

Catalytic oxidation of wastewater from terephthalic acid manufacturing plant has been accomplished in supercritical water. All experiments were performed in an isothermal tubular reactor at pressures from 220 to 300 bar, and temperatures from 418 to 513 °C. A commercial bulk γ-Al 2O 3 was used as a catalyst in a tubular reactor. At reactor entrance, the initial chemical oxygen demand (COD) concentrations of the wastewater were between 3.99×10 −3 and 2.81×10 −2 M; the COD concentrations of wastewater in feed tank were between 2400 and 14917 ppm. The oxygen concentrations at reaction conditions were between 1.4×10 −3 and 7.4×10 −3 M, which were the stoichiometric amount needed to oxidize wastewater completely to carbon dioxide. As a result of experiment, the conversion of wastewater was increased with higher wastewater feed concentration, the oxygen concentrations and contact times, and the power-law rate expression that best correlates the experimental results for the conversion of COD to CO 2 is rate=−2.67×10 2 exp(−55.456/RT)[COD] 0.81[O 2] 0.49.