• International Journal of Technology (IJTech)
  • Vol 12, No 1 (2021)

A Novel Simple Dipping-Nebulizing Water Absorption for Biogas Purification

A Novel Simple Dipping-Nebulizing Water Absorption for Biogas Purification

Title: A Novel Simple Dipping-Nebulizing Water Absorption for Biogas Purification
Totok Soehartanto, Ruri Agung Wahyuono, Putri Yeni Aisyah, Biondhi Ubaidhilah

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Cite this article as:
Soehartanto, T., Wahyuono, R.A., Aisyah, P.Y.Ubaidhilah, B., 2021. A Novel Simple Dipping-Nebulizing Water Absorption for Biogas Purification. International Journal of Technology. Volume 12(1), pp. 186-194

Totok Soehartanto Department of Instrumentation, Faculty of Vocation, Institut Teknologi Sepuluh Nopember (ITS), Jl. Arief Rahman Hakim, ITS campus Keputih, Sukolilo, 60111 Surabaya, Indonesia
Ruri Agung Wahyuono Department of Engineering Physics, Faculty of Industrial Technology and System Engineering, Institut Teknologi Sepuluh Nopember (ITS), Jl. Arief Rahman Hakim, ITS campus Keputih, Sukolilo, 60111 Surab
Putri Yeni Aisyah Department of Instrumentation, Faculty of Vocation, Institut Teknologi Sepuluh Nopember (ITS), Jl. Arief Rahman Hakim, ITS campus Keputih, Sukolilo, 60111 Surabaya, Indonesia
Biondhi Ubaidhilah Department of Instrumentation, Faculty of Vocation, Institut Teknologi Sepuluh Nopember (ITS), Jl. Arief Rahman Hakim, ITS campus Keputih, Sukolilo, 60111 Surabaya, Indonesia
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A Novel Simple Dipping-Nebulizing Water Absorption for Biogas Purification

Biogas impurities CO2 and H2S decrease the quality of biogas, which leads to a reduced caloric value and corrosive behavior, respectively. A vertical/columnar wet scrubber has been widely employed for biogas purification in which the absorption of impurities strongly depends on the contact time and surface area between the biogas and water. The drawback of this method lies in the stability of CH4 production due to the influence of the bioreactor conditions and the fluctuating condition of the surrounding environment. In this work, we present a novel design of simple water absorption columns embedded with an ultrasonic nebulizer for biogas purification. In this designed system, CO2 and H2S become dissolved in the water, as the CH4 characterized by water low solubility is released on the surface of the water by using an ultrasonic diffuser/nebulizer. We optimized the water absorption performance by varying the water pH in the range 6.0–7.3. The results indicate that water pH affects biogas purification in the designed system. The optimum pH condition was 6.78, which yielded CH4 enrichment of 11%, O2 increase of 29%, CO2 reduction of 32%, and H2S reduction of 99.8%. To evaluate the biogas purification process in the upscaled system, a model and SIMULINK-based simulation were developed to predict the biogas purification process.

CH4 enrichment; Impurities removal; Modeling and simulation; Water pH


Biogas is a renewable energy source generated from anaerobic processes of organic substrates, such as animal, plant, or household organic waste (Petersson, 2014; Ghatak and Mahanta, 2017). Typically, biogas contains methane (CH4), carbon dioxide (CO2), and hydrogen sulfide (H2S) (Arutyunov et al., 2020). CH4 can be used as an energy source for electricity generation, vehicle fuel, or as a raw material in the industry ( Wahyuono et al., 2015; Chen et al., 2017). However, the other gases contained in biogas are considered impurities. For example, CO2 which causes ozone depletion and lowers the heating value of biogas, and H2S is so strongly corrosive and can damage industrial equipment that uses biogas. Therefore, the recent development of biogas technology not only focuses on biogas production but also on the biogas purification process, particularly the removal of CO2 and H2S (Baena-Moreno et al., 2019).

There exist various biogas purification methods including physical and chemical absorption, adsorption, gas permeation through the membrane, and cryogenic methods (Horikawa et al., 2004; Abatzoglou and Boivin, 2009; Ofori-Boateng and Kwafie, 2009; Songolzadeh et al., 2014; Belaissaoui et al., 2016; Kusrini et al., 2016; Maile et al., 2017;). Of these, the spray-type wet scrubber is widely utilized in the industry for biogas purification, as the process is relatively simple with strong adaptability. The spraying water scrubber passes the biogas in the vertical vessel, and the water is sprayed from the top of the vessel (Wang et al., 2020). In the spray-type wet scrubber method, the effectiveness of impurities absorption is controlled by the dimension of the wet scrubber, as the absorption is a function of the contact surface area and contact duration (Tahir et al., 2015; Sarono et al., 2016; Kapoor et al., 2017; Noorain et al., 2019). This in turn leads to the high cost of construction and operation of the spray-type wet scrubber. Moreover, the spray-type wet scrubber is known to be merely effective for absorbing CO2, H2S or other impurities in biogas but unable to stabilize or maintain the CH4 concentration in biogas (Islamiyah et al., 2015). Therefore, CH4 gas accumulation process will not occur in the spray-type wet scrubber method as the purified biogas will pass directly through the biogas outlet to be used as an energy source (Wang et al., 2020). It should also be noted that CH4 concentration in biogas varies as the operational condition of the anaerobic bioreactor is altered. Practically, CH4 concentration must be kept to a minimum value (~ 65%) so that the energy source is sufficient to meet the minimum load (Shah et al., 2016).

In this work, we propose a new system of purification that dissolves biogas into a water absorption system that consists of two absorption columns, the so-called dipping-nebulizing water absorption system. This proposed system addresses the abovementioned drawbacks of vertical spray type water scrubber. The purification process in the proposed system mainly combines a dissolution technique by dipping the biogas outlet into water and a nebulizing technique to pull off the dissolved CH4 to the water surface, with its subsequent release in the head space of the main water absorption column. The proposed dipping-nebulizing water absorption system has been proven to work with relatively high purification efficiency. Furthermore, this proposed system does not require many mechanical components; hence, the operational cost of the upscaled system should not be a major concern. Additionally, a SIMULINK simulation based on the mathematical model for biogas purification was performed to offer insights into the proposed process in an upscaled dimension.


A miniaturized dipping-nebulizing water absorption system for biogas purification has been successfully developed, especially for CO2 and H2S reduction. The ultrasonic nebulizer was embedded in one of the bioreactor’s water absorption columns to extract CH4 out from the first water volume for purification. The biogas purification was found to be water-pH dependent, and an optimum pH condition was observed. Of the investigated pH levels, the highest purification of biogas was achieved by using water with a pH of 6.78. At the optimum pH condition, the concentration of CH4 and O2 increased by 11 and 29%, respectively, whereas CO2 and H2S was efficiently suppressed by as much as 32 and 99.8%, respectively. To upscale the system, better operational conditions were simulated using a model. Further research will focus on the optimization of water pH to yield higher CH4.


The author would like to thank Badan Riset dan Inovasi Nasional Republik Indonesia for providing research assistance through the Hibah Rencana Induk Riset Nasional scheme (Grant Contract Number : 132/5P2H/LT/DRPM/2018).

Supplementary Material
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