Waste Gas Treatment Systems Research Articles

Overheating fault traceback of Regenerative thermal oxidizer in Multi-Source waste gas treatment system via dynamic cumulative correlation analysis

Regenerative thermal oxidizers (RTO) are commonly used in the pharmaceutical and chemical industries to treat emissions of volatile organic compounds but are prone to overheating risks stemming from variations in the flow and concentration of exhausted gases from diverse workshops. This paper proposes a dynamic analysis method based on correlation between various sensor-point data to determine the cause of the RTO overheating in such a multi-source waste gas treatment system. This method continuously adjusts the length of the data in the correlation analysis to comprehensively capture the dynamic changing characteristics of the data. And a strategy for the accumulation of association degrees is introduced to reveal long-standing potential causal relationships. The effectiveness of proposed method was validated in an industrial exhaust gas treatment system of a pharmaceutical company with over 1000 sensor points. The fault diagnosis results are consistent with those of the actual on-site investigation in 5 real cases. Our proposed method can provide relatively accurate results within 2–3 h, much faster than the manual investigation of the workers (2 days on average). Moreover, compared to traditional static correlation analysis methods, our method can narrow down the investigation scope by more than 5 times. This study provides a practical and effective method for tracing the source of anomalies in complex dynamic systems, and also contributes to the safe and stable operation of chemical engineering systems.

Bioprocesses for resource recovery from waste gases: Current trends and industrial applications

Air pollution is a topic of important global concern because it has contributed significantly to an increase in the earth's global warming potential and contributed to severe health and environmental impacts. In this review, the different bioreactor configurations commonly used for waste gas treatment, namely the biofilters, the biotrickling filters and the bioscrubbers, and their industrial applications were compared in terms of the type of inoculum, the packing material/media, removal efficiency and elimination capacity. Typically, biofilters are operated under the following range of operating conditions: gas residence time = 15–60 s; gas flow rate = 50–300,000 m3 h−1; temperature = 15–30 °C; pH = 6.0–7.5; filter area = 100–3000 m2; relative humidity >95.0%; and removal efficiencies >75.0% depending on the waste gas composition and concentration. The biotechnological approaches for resource recovery, i.e., the conversion of C1 gaseous compounds (CO, CO2 and CH4) to liquified value-added products or biofuels have been discussed. From this review, it was evident that the performances of different aerobic, anoxic and/or anaerobic lab, pilot and full-scale bioreactors for waste gas treatment and resource recovery depend on the composition, the individual concentration of pollutants present in the waste gas and the gas flow rate. Although most of the research on product recovery from waste gas is rather limited to lab/pilot-scale studies, there are some key commercialized technologies that have proven to be economical at the full-scale. Thus, this review, comprehensively presents a complete overview of the current trends and limitations of conventional waste gas treatment systems, the benefits of novel bioreactor configurations and their potential to be applied for resource recovery from waste gases.

Limestone-Gypsum Wet Flue Gas Desulfurization Wastewater Treatment

In this paper, chemical precipitation process is used for the treatment of the desulfurization wastewater generated by the waste gas treatment system of the limestone-gypsum flue gas desulfurization process of a thermal power plant. After one year of operation, the technology is reliable and stable. The removal rate of suspended matter, COD, fluoride, mercury and sulfate reached 99.5%, 98.3%, 87.5%, 99.8% and 85.6% respectively, and the corresponding effluent concentrations were 54 mg/L, 20 mg/L and 9.6 mg/L, 0.04 mg/L, 980 mg/L. Finally, the effluent quality of the system is better than the discharge requirements of “Discharge standard of wastewater from limestone-gypsum flue gas desulfurization system in fossil fuel power plants” (DL/T997-2006). In addition, the total electricity and chemical charges per ton of wastewater treatment were 6.50 yuan, which is lower than most of the engineering project under the same discharge requirements. Therefore, the process has certain engineering advantages.

A highly dispersed Co–Fe bimetallic catalyst to activate peroxymonosulfate for VOC degradation in a wet scrubber

This work synthesized a highly dispersed Co–Fe bimetallic catalyst with uncalcined SBA-15 as the support, which was very efficient for PMS activation and gaseous toluene degradation in the wet scrubbing waste gas treatment system.

Dynamic adsorption properties of activated carbon for radioactive noble gas treatment in offshore floating nuclear power plant

Offshore floating nuclear power plant (OFNPP) is a significant solution for marine electricity shortage. In this study, the optimized activated carbon for decay technology was studied in the experiment bench and engineering prototype respectively. The results show that ZLCYK001 activated carbon has better properties. The adsorption coefficient for krypton can be improved when the pressure is increased, the temperature and relative humidity are decreased and the flow velocity is controlled between 0.12 and 5 cm/s. The adsorption property has good reliability and stability in engineering prototype which is significant for the design and operation of the waste gas treatment system.

A Novel Stochastic Two-Stage DEA Model for Evaluating Industrial Production and Waste Gas Treatment Systems

In recent decades, the high-speed development in China has caused serious air pollution in China. The present paper proposes a stochastic data envelopment analysis (DEA) model based on a general two-stage structure with comprehensively considering the randomness in both desirable and undesirable outputs to calculate the environmental efficiency of the industry system. The new proposed model is more applicable to practical system, and is applied to evaluate the performance of production and waste gas treatment in the industrial sector for China’s regions along the “One Belt and One Road” in 2015. The results show that about half of the regions along “One Belt and One Road” in China are inefficient, where the performance on waste gas treatment is significantly worse than that of industrial production. Further, the managers should take different strategies for efficiency improvement in different areas because of the obvious differences in efficiency scores, in which the regions in the southeast area should pay more attention to improving waste gas treatment efficiency while that in the northwest area need to focus on industrial production efficiency.

Low-cost process for emission abatement of biogas internal combustion engines

Biogas internal combustion (IC) engines of less than 1 MW are either equipped with an oxidative catalyst or operate at low-emission operation parameters to meet national emission standards of NOx, CO, VOCs, HCl, H2S, SO2, and formaldehyde safely. However, expensive oxidative catalysts have a limited lifetime of less than two years, and electrical efficiency at low-emission conditions is lower than that at optimal conditions, characterized by higher emission levels. While NOx levels increased seven times from 282.2 to 1965.7 mg NOx∙m−3 by changing the operational parameters of the four-stroke gas engine (Pel = 360 kW), emission levels of CO and VOC slightly changed from 540.3 to 452.5 mg CO∙m−3 and 509.6 to 329.9 mg C∙m−3. Furthermore, NOx emission levels could be reduced by a minor air to gas ratio, but levels of VOC, CO, and HCl increased at these conditions as shown for a four-stroke gas engine (Pel = 635 kW). The emissions of the dual-fuel gas compression-ignition engine (Pel = 265 kW) were generally characterized by higher emission levels. A chemical scrubber with an optional subsequent biofilter was installed as a low-cost alternative for oxidative catalysts as a waste gas treatment system. Corresponding performance levels of the chemical scrubber were in the range of 28.3–38.6% (NOx), 19.2–30.8% (CO), 22.6–23.8% (VOCs), and 33.3–70% (odor). Formaldehyde, which occurred at levels of 43.4–59.6 mg m−3, was almost completely eliminated by the scrubber after injection of ambient air, but the system failed in tests without air injection. The performance was further enhanced by addition of H2O2. Further approaches in chemical removal of formaldehyde by addition of NH3 or urea failed. The biofilter showed no treatment performance under thermophilic conditions. The amortization time of the scrubber system was less than three years, caused by economic benefits of higher electrical efficiency and substitution of the catalyst.

Modelling the removal of volatile pollutants under transient conditions in a two-stage bioreactor using artificial neural networks

A two-stage biological waste gas treatment system consisting of a first stage biotrickling filter (BTF) and second stage biofilter (BF) was tested for the removal of a gas-phase methanol (M), hydrogen sulphide (HS) and α-pinene (P) mixture. The bioreactors were tested with two types of shock loads, i.e., long-term (66h) low to medium concentration loads, and short-term (12h) low to high concentration loads. M and HS were removed in the BTF, reaching maximum elimination capacities (ECmax) of 684 and 33 gm−3h−1, respectively. P was removed better in the second stage BF with an ECmax of 130 gm−3h−1. The performance was modelled using two multi-layer perceptrons (MLPs) that employed the error backpropagation with momentum algorithm, in order to predict the removal efficiencies (RE, %) of methanol (REM), hydrogen sulphide (REHS) and α-pinene (REP), respectively. It was observed that, a MLP with the topology 3-4-2 was able to predict REM and REHS in the BTF, while a topology of 3-3-1 was able to approximate REP in the BF. The results show that artificial neural network (ANN) based models can effectively be used to model the transient-state performance of bioprocesses treating gas-phase pollutants.

Neural network models for biological waste-gas treatment systems

This paper outlines the procedure for developing artificial neural network (ANN) based models for three bioreactor configurations used for waste-gas treatment. The three bioreactor configurations chosen for this modelling work were: biofilter (BF), continuous stirred tank bioreactor (CSTB) and monolith bioreactor (MB). Using styrene as the model pollutant, this paper also serves as a general database of information pertaining to the bioreactor operation and important factors affecting gas-phase styrene removal in these biological systems. Biological waste-gas treatment systems are considered to be both advantageous and economically effective in treating a stream of polluted air containing low to moderate concentrations of the target contaminant, over a rather wide range of gas-flow rates. The bioreactors were inoculated with the fungus Sporothrix variecibatus, and their performances were evaluated at different empty bed residence times (EBRT), and at different inlet styrene concentrations (C(i)). The experimental data from these bioreactors were modelled to predict the bioreactors performance in terms of their removal efficiency (RE, %), by adequate training and testing of a three-layered back propagation neural network (input layer-hidden layer-output layer). Two models (BIOF1 and BIOF2) were developed for the BF with different combinations of easily measurable BF parameters as the inputs, that is concentration (gm(-3)), unit flow (h(-1)) and pressure drop (cm of H(2)O). The model developed for the CSTB used two inputs (concentration and unit flow), while the model for the MB had three inputs (concentration, G/L (gas/liquid) ratio, and pressure drop). Sensitivity analysis in the form of absolute average sensitivity (AAS) was performed for all the developed ANN models to ascertain the importance of the different input parameters, and to assess their direct effect on the bioreactors performance. The performance of the models was estimated by the regression coefficient values (R(2)) for the test data set. The results obtained from this modelling work can be useful for obtaining important relationships between different bioreactor parameters and for estimating their safe operating regimes.

Neural network models for biological waste–Gas treatment systems

Neural network models for biological waste–Gas treatment systems

Design, Fabrication, and Testing of Getter-Based Atmosphere Purification and Waste Treatment System for a Nitrogen-Hydrogen-Helium Glovebox

A system containing a combination of getters (Zr-Mn-Fe, SAES St909; and Zr2Fe, SAES St198) was used to process the nitrogen-hydrogen-helium atmosphere in a glovebox used for handling metal tritide samples. During routine operations, the glovebox atmosphere is recirculated and hydrogenous impurities (i.e. CQ4, Q2O, and NQ3, where Q [is equivalent to] H, D, T) are decomposed (cracked) and removed by Zr-Mn-Fe without absorbing elemental hydrogen isotopes. If the tritium content of the glovebox atmosphere becomes unacceptably high, the getter system can rapidly strip the glovebox atmosphere of all hydrogen isotopes by absorption on the Zr2Fe, thus lessening the burden on the facility waste gas treatment system. The getter system was designed for high flowrate (> 100 l/min), which is achieved by using a honeycomb support for the getter pellets and 1.27-cm diameter tubing throughout the system for reduced pressure drop. The novel getter bed design also includes an integral preheater and copper liner to accommodate swelling of the getter pellets, which occurs during loading with oxygen and carbon impurities. Non-tritium functional tests were conducted to determine the gettering efficiencies at different getter bed temperatures and flowrates by recirculating gas through the system from a 6-m3 glovebox containing known concentrations of impurities.

Medical biofilms.

For more than two decades, Biotechnology and Bioengineering has documented research focused on natural and engineered microbial biofilms within aquatic and subterranean ecosystems, wastewater and waste-gas treatment systems, marine vessels and structures, and industrial bioprocesses. Compared to suspended culture systems, intentionally engineered biofilms are heterogeneous reaction systems that can increase reactor productivity, system stability, and provide inherent cell:product separation. Unwanted biofilms can create enormous increases in fluid frictional resistances, unacceptable reductions in heat transfer efficiency, product contamination, enhanced material deterioration, and accelerated corrosion. Missing from B&B has been an equivalent research dialogue regarding the basic molecular microbiology, immunology, and biotechnological aspects of medical biofilms. Presented here are the current problems related to medical biofilms; current concepts of biofilm formation, persistence, and interactions with the host immune system; and emerging technologies for controlling medical biofilms.

Aktuelle Entwicklung der Abluftreinigung in der Tierhaltung

To determine the level of waste gas treatment systems in animal husbandry in Germany, eight manufacturers of these systems were interviewed in 2006 and 2007. These companies have built 494 waste gas treatment systems since 1997, 128 alone in 2006. Waste air treatment systems are applied in pig keeping for all numbers of livestock, but in poultry keeping only for more than 30,000 heads. The market share of tested and approved producers of waste air treatment systems increased from 57 % (2002) to 94 % (2006) in pig keeping. Waste air treatment will continue to grow in importance for the livestock development in coming years.

Sind Abluftwäscher zur Minderung von Staubemissionen geeignet

Technical requirements in Germany may stipulate measures for reducing dust emissions from animal facilities to comply with federal limitations. Tests on a two-stage scrubber showed that particles with a diameter of at least 2 ?m could be separated with at least a 95 % efficiency level. More than 70 % dust reduction can be maintained with various waste gas treatment systems, if they are dimensioned and operated properly.

Recent developments in biological waste gas purification in Europe

Polluted air has become an increasing environmental and health concern. Legislation controlling the emissions of air pollutants (VOC, toxics and odor) has proliferated. In recent years, biological techniques have been applied more frequently to control these emissions, because they eliminate many of the drawbacks of classical physical–chemical techniques. Different waste gases require different strategies for optimal and sustainable purification. Biological treatment provides an expanding variety of opportunities for economical and environmentally friendly solutions for many waste gas emissions. In Europe, a significant body of knowledge and experience has been generated on biological waste gas purification. Examples of some interesting developments and new applications of biological waste gas treatment systems in Europe during the last 5 years are presented in this paper.

Odour control at biowaste composting facilities

There are several options to effectively reduce odorous emissions at composting facilities depending on the type of composting system used. Some of the more relevant measures for open and enclosed composting facilities are presented in this article. Results from different investigations on odour reduction efficiencies of biological waste gas treatment systems at various scales are presented. Biofilter/bioscrubber combinations were used and different biofilter materials were tested. The more relevant odorous substances in the waste gas were identified, and their reduction in the different systems was measured. The biofilter proved to be mainly responsible for efficient odour degradation. The investigations presented in this article revealed that screened compost was very effective, and proved to be a low cost biofilter material for odour degradation purposes. Screened compost showed higher degradation rates than a coke–compost mixture newly developed by the University of Leipzig. Furthermore, it seems that enclosed systems have advantages when compared to conventional open single bed biofilters.

Odour management and treatment technologies: An overview

There is a large variety of options available for the effective treatment of odorous emissions. The most important physical, chemical and biological treatment processes are shortly described and their favourable applications, as well as their limits, are highlighted. But for a sustainable solution of an industrial odour problem, there is more involved than just the installation of a waste gas treatment system. This article focuses on a general and systematic approach towards extensive odour management. First of all, an odour assessment should be worked out where all actual and potential odour emission sources are recorded and characterised. A special focus should be set on fugitive emissions, which may have an enormous impact on the overall odour problem. They need to be captured before they can be supplied to a treatment system. According to the composition and condition of the waste gases, an appropriate treatment system must be selected. For this purpose, test systems have been developed and are presented in this article.

The potential to reduce emissions of airborne microorganisms by means of biological waste gas treatment systems

Investigations regarding the reduction of airborne germs in the waste gas of biowaste composting processes have been carried out at the Hamburg University of Science and Technology and the University of Leipzig. Numerous waste gas treatment plants, ranging from laboratory-scale to technical-scale, have been available at the institutes of these two project partners. All plants consisted of bioscrubber/biofilter combinations. The results showed that these biological systems designed for odour control are able to successfully reduce bioaerosol emissions, even though a reduction to background levels could not be achieved. The bioscrubber, if equipped with a droplet separator, proved to be mainly responsible for the reduction, whereas the biofilter acted as a source for microbial emissions originating from the filter material. It could be observed that the microbial population changed while passing the treatment system, indicating the ability of biological waste gas treatment systems to retain potentially pathogenic microorganisms from waste gases.

Optimalisation of Magnesium Ammonium Phosphate Precipitation and Its Applicability to the Removal of Ammonium

Among the physico-chemical abatement technologies, mainly acid scrubbers have been used to control NH3-emission. The disadvantage of this technique is that it yields waste water, highly concentrated in ammonia. In this report, the applicability of the magnesium ammonium phosphate (MAP) process to regenerate the liquid phase, produced by scrubbing NH3-loaded waste gases, was investigated. In the MAP process, ammonium is precipitated as magnesium ammonium phosphate, which can be used as a slow release fertilizer. The influence of a number of parameters, e.g. pH, kinetics, molar ratio NH(+)4/Mg2+/PO(3-)4 on the efficiency of the formation of MAP and on the ammonium removal efficiency was investigated. In this way, optimal conditions were determined for the precipitation reaction. Next to this, interference caused by other precipitation reactions was studied. At aqueous NH(+)4-concentrations of about 600 mg l(-1), ammonium removal efficiencies of 97% could be obtained at a molar ratio NH(+)4/Mg2+/PO(3-)4 of 1/1.5/1.5. To obtain this result, the pH was continuously adjusted to a value of 9 during the reaction. According to this study, it is obvious that the MAP-precipitation technology offers opportunities for ammonium removal from scrubbing liquids. The practical applicability of the MAP-process in waste gas treatment systems, however, should be the subject for further investigations.

Optimalisation of Magnesium Ammonium Phosphate Precipitation and its Applicability to the Removal of Ammonium

Among the physico-chemical abatement technologies, mainly acid scrubbers have been used to control NH3-emission. The disadvantage of this technique is that it yields waste water, highly concentrated in ammonia. In this report, the applicability of the magnesium ammonium phosphate (MAP) process to regenerate the liquid phase, produced by scrubbing NH3-loaded waste gases, was investigated. In the MAP process, ammonium is precipitated as magnesium ammonium phosphate, which can be used as a slow release fertilizer. The influence of a number of parameters, e.g. pH, kinetics, molar ratio NH4+/Mg2+/PO43- on the efficiency of the formation of MAP and on the ammonium removal efficiency was investigated. In this way, optimal conditions were determined for the precipitation reaction. Next to this, interference caused by other precipitation reactions was studied. At aqueous NH4+-concentrations of about 600 mg 1-1, ammonium removal efficiencies of 97% could be obtained at a molar ratio NH4+ /Mg2+/PO43- of 1/1.5/1.5. To obtain this result, the pH was continuously adjusted to a value of 9 during the reaction. According to this study, it is obvious that the MAP-precipitation technology offers opportunities for ammonium removal from scrubbing liquids. The practical applicability of the MAP-process in waste gas treatment systems, however, should be the subject for further investigations.