Analysis of Zig-Zag Gas Inlet Design Effectiveness to The Reduction of CO2 and H2S Gas at Purifier Equipment using Four Absorber Types

Design of inlet gas in purifier equipment was affected on the reduction of CO2 and H2S.This study has been conducted on the analysis of the effect of zig-zag gas inlet design on the level of CO2 and H2S gas reduction in purifier using 4 types of absorber. Ferrioxide, iron gram, limestone (CaO), and natural zeolite were used as absorber material. The objective of this research is to determine which the most effective type of absorber in reducing CO2 and H2S gas and create an economical and useful purifier equipment for society. The results was found that the natural zeolite absorber was an effective absorber in reducing CO2 gas, CO2 content before purification was 40.98 % and after purification was 25.80 %, decreasing of CO2 was 15.18 %. Meanwhile, ferrioxide absorber, iron gram and CaO was not effective in reducing CO2. Ferrioxide was found to be effective absorber in reducing H2S, average decreasing was 16.95 ppm. Average decreasing of H2S in natural zeolite and iron gram absorber were 2.13 ppm and 0.16 ppm, respectively. CaO was found to be ineffective absorber for H2S due to increasing in H2S levels after purification.


INTRODUCTION
Human dependence on fossil fuels not only influence the decreasing of unrenewable energy but also the environment, such as air pollution. It cause people realize that dependence on fossil fuels should be reduced immediately. Alternative fuel, which is cheap and easy to obtain, is required to solved this problem. Biogas is one of promising alternative fuel that can be used. Biogas is produced through the process of fermentation of organic waste such as garbage, food scraps, animal waste and industrial food waste. Biogas contain methane (CH4), carbon dioxide (CO2) gas, oxygen (O2), hydrogen sulfide (H2S), hydrogen (H2) and carbon monoxide (CO). CH4 and CO2 are the component that determine the quality of biogas. Biogas have high heating value due to high level of CH4. Meanwhile, high levels of CO2 will result in low calorific value of biogas. Therefore, to increase the calorific value of biogas, CO2 should be decreased. The content of CH4 from biogas can be increased by separating CO2 and H2S which is corrosive from biogas (Hamidi, Wardana, & Widhiyanuriyawan, 2011). In the combustion process, gases other than methane (CH4) will decrease the biogas heat value and combustion efficiency. Maximazing the percentage of CH4 to get a greater calorific value from biogas by reducing other gas, especially CO2 due its content is the greatest after CH4 (Sugiarto, Oerbandono, Widhiyanuriyawan, & Putra, 2013).The previous study has been done to solve the problem, several methods of absorbent variation were used to purify gas, they were natural zeolite, iron gram, CaO and peroxide. Absorbent is a substance that can absorb fluid, both liquid and gas so that it will form a thin layer on the surface of the substance. Zeolite, iron gram, CaO and peroxide were chosen due to easy to obtain and the price is also quite cheap. Activation process should be done before zeolite is used to accelerating zeolite adsorption process. The activation process can be done in two ways, ie physically with heat treatment process and chemically by using acid or base solution. One type of chemical substances that can be used for the process of chemical activation is potassium hydroxide (KOH). KOH is one of the strongest stable and water-soluble base compounds that can be used as a zeolite activator (Hamidi et al., 2011).

Literature study and Product Analysis in Marketplace
Learn and seek information as much as possible from books, journals, internet and consult with people who have understood about the purification system in biogas to get information and reference. In addition to literature studies, product analysis that already exist in the market is also very important as a comparison to conduct research that will be done.

Product Concept
Based on literature study and product analysis that has been done, reference products for experiment was obtained. Based on this reference, the concept of both the dimensions and the effectiveness of the product will be produced later.

Calculation of Zig -Zag Flow Purifier Equipment
Data is given below :

Equipment Design
The next step after product concept was the design of purifier equipment. This step was to determined the material for making the effective and economical equipment and prepared all component to produce the equipment.

Absorber and Purifier Equipment Design
After all the needs and materials were prepared then the next step was to make the equipment and design. The purpose of this step was to determined the appropriate layout for gas inlet and absorber material, so the purifier equipment run in accordance with its function.

Trial of Absorber and Purifier Equipment
In the experimental stage of this device, the purifier was filled with 4 types of absorber ie ferrioxide, iron gram, CaO and natural zeolite in different purifier and reactor with 6 m 3 digester capacity. Trial was done for 8 days with data collecting as much as 4 samples every 2 days. Meanwhile, the pure sample was collected on day-0 before the purifier equipment installed. All samples were tested at LPPM-ITS Energy Laboratory.

The
Step of Biogas Sample Analysis: 1. Pure biogas sampling was done before the purifier installed by using the air ball at 4 reactors which have been determined for testing at Energy Laboratory -LPPM ITS and in Environmental Laboratory -LPPM ITS. 2. After 4 purifier equipment installed on every home, then 2 sample was collected in every house using air ball, where sample was taken as much as 4 times in about 8 days. 3. Collecting 2 samples in each house was done 2 days after the purifier installed for the first sample, on the 4 th day for the second sample, on the 5 th day for the third sample and on the 8 th day for the fourth sample. 4. CO2 gas levels was analyzed in the energy laboratory using Gas Chromatography (GC). The gas inside the air ball was taken by using the injector then injected into the GC column.
FIGURE 2. Gas Chromatography 5. H2S gas levels was analyzed in the environment laboratory using PID Detector. It has gas output located on the air ball directly in connect with the inject hose on the equipment. This equipment is a combination of previous tool design, where in the gas cylinder there is a ½ inch pipe designed in the form of zig-zag shaped. The function of zig-zag pipe inside the tube is to drain the gas from the input to be distributed to the absorber in the tube. Production costs of Purifier equipment is described in Table 1:

Testing Procedure
Testing procedure of purifier through two stages, the first stage was the assembly stage of the purifier equipment and the second stage was the testing phase of biogas sample on the purifier.

Head Losses
Determining the value of gas discharge on the stove (m 3 /s) It was assumed that the gas debit inside the gas pipe was the same as the gas discharge was fed.
Determining the velocity value (v): The absorbent permeability value of the purifier was determined by using this equation: . shows that ferrioxide did not reduce CO2; it was proved with increasing in CO2 gas content. The highest CO2 content was obtained on the 6t h day amounted to 1497 %.
Fe2O3 (s) + CO2 (g) (CO2 inert gas) FIGURE 6. H2S Removal at Reactor I It can be seen from Figure 6 that the ferrioxide absorbent was very effective in reducing H2S gas, the highest absorption was obtained at 6 th day, amounted to 98.9 % removal. From Figure 10, it can be seen that the absorbent CaO effectively absorbed CO2 gas until the 2 nd day, decreasing of CO2 was amounted to 95.14 %.

FIGURE 11
. CO2 Removal at Reactor IV Figure 11 represent that natural zeolite absorbent was effective in reducing CO2 gas, it was indicated by the largest decreasing of CO2 content on day 6, amounted to 50.61 %. Decreasing of CO2 was reduced on 8 th day, amounted to 6.368 %.
SiO2(s) + CO2 (g) FIGURE 12. H2S removal at Reactor IV Figure 12 shows that natural zeolite absorbent was effective in reducing H2S gas, it was proved by decreasing of H2S content about to 85.54 % on the 6 th day. The absorption was still effective until the 8 th day, even though the decreasing level of H2S was getting smaller to 49.39 %.

CONCLUSION
Based on data calculation that was obtained during the experiment and analysis, the conclusions of this experiment are mention below: 1. Absorber was effective in reducing CO2 gas is the nature Zeolite absorber because it is able to remove CO2 gas up to 50.61 %. 2. Ferroxide, iron gram, and natural zeolite were effective absorber in reducing H2S. The removal of H2S were amounted to 98.9 %, 98.5 % and 85.54 %, respectively. 3. H2S in biogas was not corrosive for biogas stoves due to very few particles of H2S elements produced.