Compatibility Investigation of Soaked Biomass in Vacuum Gasification using FMEA

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Investigation of The Compatibility of Soaked Biomass in Vacuum Gasification

Journal: Clean Energy Manuscript ID Draft

Manuscript Type: Research article

Keywords: Vacuum gasification, Soaked biomass, Temperature profile, Failure mode and effect analysis, Compatibility

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Investigation of the compatibility of soaked biomass in vacuum gasification Abstract

An alternative development of safe and easy gasification to overcome the fossil energy crisis and environmental damage is the vacuum gasification of soaked biomass. This process reduces the risk of explosion, has a simpler biomass input feed, and reduces drying time and costs. This research is compatibility testing for 10 types of biomass in a biomass vacuum gasification system using the Failure Mode and Effect Analysis (FMEA) method approach. The FMEA method is used to predict gasification failure by analyzing 3-dimensional thermal data of the reactor for its temperature stability, the position of the oxidation temperature, and the length of the gasification temperature region. The results obtained were:

2 types of biomass that were very suitable, bamboo and coconut shells (RPN < 100), and 5 types of biomass that were moderately suitable, rambutan 1, rambutan 2, rubber wood, albizia, and gmelina (100 < RPN <

500). Three types of biomass that have a risk of failure or are not suitable are rice husks, corn cobs, and palmyra shells (RPN > 500). It is clear that the water retention properties, shape, and size of the biomass play an important role in determining its suitability for this gasification.

Graphical Abstract

Keywords: Vacuum gasification; Soaked biomass; Temperature profile; Failure mode and effect analysis; and Compatibility.

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1. Introduction

The transition to renewable energy sources is essential to mitigate the impacts of global warming and reduce our dependence on limited amounts of fossil fuels [1]. By investing in sustainable energy solutions, we can work towards a more environmentally conscious future and combat the threat of further natural disasters caused by climate change [2]. Biomass gasification is considered a more environmentally friendly option compared to traditional fossil fuels, as it produces lower levels of greenhouse gas emissions. In addition, biomass is a renewable energy source that can be managed and harvested sustainably [3]. Indonesia, as an agricultural country, has an agricultural waste biomass energy potential of 31,694 MW, and only 4.9% has been utilized [4]. This makes it a promising alternative to meet energy needs while reducing dependence on limited fossil fuel resources [5]. Therefore, the development of biomass gasification technology is very important in moving towards a more sustainable and environmentally conscious energy future.

Biomass gasification is the conversion of material from living biomass into solid form into syngas (CO and H2) through a thermochemical process at a temperature of 800–1200 °C [6].

Syngas are flammable, so this gas can be used as a substitute for fossil fuels. In general, gasification technology uses a compressed or pushed air flow so that the system is at high pressure and is vulnerable to explosion. High-pressure reactors require a closed mechanism, making it difficult to supply biomass fuel to the reactor [7]. Therefore, this research focuses on developing a biomass gasification process that can operate at lower pressures to increase safety and efficiency [8], [9].

By optimizing the gasification reactor design and implementing advanced control systems, stable and reliable operation at lower pressures can be achieved. This will not only reduce the risk of explosion but also make it easier to distribute biomass fuel into the system, which ultimately increases the feasibility and scalability of biomass gasification technology as a sustainable energy solution [9], [10].

In addition, the use of soaked biomass will facilitate the biomass gasification process.

Soaked biomass will save drying costs, especially in cold or rainy seasons, compared to traditional gasification methods. Soaked biomass increases the carbon dioxide and hydrogen content in the syngas, thereby increasing system efficiency. The cost savings and increased system efficiency associated with the use of soaked biomass make this technology more economical and attractive

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for carbon-reducing industries. Overall, the use of soaked biomass in the vacuum gasification process provides a promising opportunity to increase energy efficiency, reduce environmental impact, minimize waste, and create more sustainable energy production [11].

In this regard, it is necessary to carry out experimental studies of soaked biomass in vacuum gasification due to the lack of research reports. The more biomass experiments with many types of mass studied will further complement the development of economical and efficient gasification technology. This information will be invaluable to researchers and engineers looking to optimize systems for a variety of biomass feedstocks. Additionally, this reference list will serve as a guide for industry and policymakers interested in transitioning to more sustainable and renewable energy sources. Overall, this study highlights the potential of soaked biomass vacuum gasification as a promising technology for biomass utilization and energy production.

The focus of this research is to test the compatibility of several types of biomass with soaking wet treatment in a vacuum gasification system. This compatibility assessment is made simple by analyzing the gasification process that occurs in the reactor, thereby facilitating the initial analysis of gasification process failures. This gasification process can be displayed in the form of a reactor temperature profile as a function of temperature, reactor depth, and testing time [12]. The temperature profile of this reactor can be used to determine whether the gasification process will run well or fail. This gasification failure analysis method is approached using failure mode and effect analysis (FMEA), and the FMEA method has been widely used to analyze failures in the industrial, health, automotive, and aerospace sectors [13]. By applying FMEA to the gasification process, engineers can identify potential failure modes, assess their severity, and prioritize them for corrective action [14]. This proactive approach allows for the prevention of process failures, improving safety and efficiency in gasification plants. Additionally, the data collected from the FMEA analysis can be used to continuously improve the design and operation of gasification reactors, leading to more reliable and sustainable energy production. and other processes. The Introduction of your paper should state the nature of the project or problem you are addressing and why you are studying it. It should provide background information about the work and its significance, while highlighting other relevant literature and specifying how it relates or differs from your work. You should also discuss the scope and limitations of your study or project in the Introduction.

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2. Literature Review

Vacuum gasification of submerged biomass is the process of converting biomass at temperatures above 800 °C in very wet or soaked conditions into syngas, which takes place at pressures below atmospheric or vacuum. This process is advantageous because it allows the use of wet biomass, thereby reducing the need for pre-gasification drying, which can consume a lot of energy and increase syngas levels. The biomass feed is fed into the reactor, where the biomass is first soaked in water until it becomes very wet. Air and biomass can easily enter the reactor because the reactor is open and air flows as a result of being sucked in by the air pump at the end of the system. An open gasifier system will make it easier for biomass feed to enter the reactor continuously without pause. The vacuum pressure system also helps eliminate high pressure so that this gasification system is safe and does not explode easily. With further research and development, vacuum gasification of soaked biomass could play an important role in creating a more sustainable future for future generations. Additionally, the use of wet biomass eliminates the need for expensive drying processes, making this technology cost-effective and environmentally friendly [11], [15].

Biomass is burned in the reactor to produce the heat needed in the gasification process, and when oxygen from the air enters the reactor, a combustion reaction will be triggered [16]. Research on adding water content by spraying it into the gasification process will be more effective and efficient. Biomass gasification with sprayed water increases the hydrogen content but requires a more complicated mechanism [17], [18], and [19]. Soaked biomass can also increase the calorific value of syngas, which is easier than the spraying mechanism [11]. In addition, the gasification process will be influenced by several factors, such as biomass type, biomass size, water content, air flow, biomass flow, and reactor type [2], [20], [21], [22], [23], [24]. By understanding and manipulating these factors, the goal is to develop more sustainable and efficient gasification technologies for biomass conversion. This research will continue to focus on optimizing these main parameters to maximize the potential of biomass gasification as a renewable energy source.

The thermochemical process in biomass gasification goes through four stages: drying, pyrolysis, oxidation, and reduction. While it is true that the biomass gasification process typically involves these four stages, the specific details and sequence of these stages can vary depending on

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the type of biomass used and the operating conditions of the gasifier [25], [26], [27]. The process of biomass gasification stages in the downdraft gasifier type is shown in Fig. 1.

The drying process is the evaporation of the water content in biomass into steam through a heat transfer mechanism by conduction from the surface to the center of the biomass particles. The heat required at this stage is proportional to the water content contained in the biomass, and the temperature of the biomass drying process occurs at 150–250 °C [28]. If the water content is too high, it will cause the drying process to take up a lot of energy, so the gasification temperature will drop. In addition, smaller biomass particles have a higher surface area-to-volume ratio, thereby increasing the evaporation rate and reducing overall drying time; conversely, larger biomass sizes will reduce the evaporation rate and result in longer drying times. [18], [29]. Overall, the use of wet and large biomass particles will increase failure in the gasification process.

Fig. 1. Stages of the thermochemical process in the biomass gasification downdraft gasifier.

The pyrolysis process, also known as devolatilization, relates to the thermochemical decomposition of biomass, specifically the breaking of chemical bonds between heavy molecules into lighter molecules. The pyrolysis process will produce gases in the form of CO, CO2, water vapor, methane, and light hydrocarbons; liquids in the form of tar; and solids in the form of

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charcoal and ash. The pyrolysis reaction is endothermic (absorbs heat), and the temperature occurs in the range of 200–700 °C [30]. The phenomena involved in this step include heat transfer and the breakdown of products from biomass pore solids into gas and liquid phases, and the reaction is complex and complicated [31]. Pyrolysis reactions can be classified into primary and secondary processes. The primary process occurs in the temperature range of 200–600 °C and is associated with the initial decomposition of biomass into tar, char, and volatiles. The secondary process takes place at temperatures above 600°C and consists of the cracking of tar into hydrocarbons [32]. The secondary process consists of cracking tar into hydrocarbons at temperatures above 600°C and complete breakdown at temperatures above 1000°C [12], [33]. The complete breakdown of tar into hydrocarbons at temperatures above 1000°C is crucial for producing cleaner syngas that can be effectively utilized in the next power system. Without reaching this high temperature, the syngas may still contain tar particles, making it less desirable for further use. Therefore, maintaining the appropriate temperature during the secondary process is essential for maximizing the efficiency and cleanliness of the syngas produced from biomass decomposition [34].

The oxidation process, or combustion process, is the only gasification process that produces an exothermic reaction (a reaction that produces heat). Apart from providing heat energy for various processes, oxidation reactions also play an important role in controlling the temperature in the reactor [35]. There are three important elements for this oxidation reaction to occur: heat, fuel, and air (oxygen). The combustion reaction will only occur if these three elements are available in equal amounts. By ensuring the presence of oxygen in equilibrium conditions, only part of the fuel (charcoal) is oxidized, thereby allowing a controlled increase in temperature. This controlled oxidation process is important to achieve the desired temperature range of 800–1600

°C for efficient reactor operation [36], [37]. Overall, oxidation reactions are a key component of the successful implementation of various processes in gasification systems [38].

The reduction process is the final process in biomass gasification in a downdraft gasifier and is often called the gasification zone, as seen in Fig. 1. Hot charcoal produced from the oxidation process will react with the reactants resulting from pyrolysis at a temperature range of 700–1200 °C. During this stage, the remaining carbon in the biomass is converted into carbon monoxide and hydrogen gas. This reaction is highly endothermic, requiring a significant amount of heat energy. The gasification zone is crucial in producing clean and high-quality syngas that

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can be utilized for various applications, such as electricity generation or biofuel production. The ideal temperature for this process is above 1000 °C because the resulting syngas product will be clean (tar-free), and if the temperature drops below 1000 °C, then syngas will be produced that contains tar levels. Tar levels will be higher if the temperature continues to fall to 700 °C and the gasification process stops below 700 °C. At the end of the reduction process, the final gas composition will be produced in the form of syngas (H2 and CO). When leaving the gasifier, the resulting gas carries a certain amount of dust, tar, and water vapor. Overall, maintaining temperatures above the 700–1200 °C range is critical for a cleaner syngas product with minimal tar content [20], [22], [24], [28], [30], [31].

The gasification process described above involves complex gas-solid reactions (heterogeneous reactions) and gas-phase reactions (homogeneous reactions). The reaction pathways of these reactions still require full understanding. The four-stage gasification process is strongly influenced by the type, shape, size, and moisture content of the biomass [39], [40], [41].

Certain types of biomass, such as corn cobs, are hydroscopic and can absorb more water [42]. This can cause an increase in water content, resulting in a decrease in maximum temperature and flame speed [26], [41], [43]. In addition, biomass size can also influence gasification temperature and flame speed [41]. The density, or porosity, of biomass can affect the gasification process. If the biomass is less dense or porous, the reaction can occur at a more uniform temperature. On the other hand, dense or non-porous biomass in the form of lumps results in non-uniform gasification temperatures [44]. Variations in gasification temperature can affect the overall efficiency and effectiveness of the process. Therefore, it is necessary to continue studying and analyzing the influence of biomass characteristics on gasification in order to increase the sustainability of this renewable energy technology.

Table 1. Types, sizes, and properties of biomass

Size (mm) Calorific Ref.

No Biomass

type Thick Wide Long Dia.

Shape Hard

ness

Hygro

scopic (MJ/kg)

1. Bamboo 2-4 30-50 100 flat hard No 18.4 [45][46]

2. Rambutan 1 100 20-40 Branches wood hard No 16.7 [47]

3. Rambutan 1 150 20-40 Branches wood hard No 16.7 [47]

4. Coconut shell 2-4 20-40 Pieces hard No 19.54 [48]

5. Corncob 100 30-50 Corn cob Soft Yes 23.33 [49]

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6. Palmyra shell 2-4 50-

100

Bowl hard No 19.50 [50]

7. Gmelina 100 20-40 Branches wood hard No 17.95 [51]

8. Rubber wood 150 10-30 Branches wood hard No 17.03 [33]

9. Rice husk 5 1.5-

2.5

husk granules ^soft ^Yes ^11.03 ^[52]

10. Albazia 100 20-40 Branches wood hard No 19.73 [53]

3. Materials And Methods

3.1. Biomass Properties

In this study, 10 biomass samples were used. The biomass samples were collected from a variety of sources, including agricultural residues, plantation waste, and forestry waste around the study site (Subang, West Java, Indonesia). Each biomass type was carefully prepared for size, shape, and type to determine its suitability for use as an experimental material for soaked biomass in vacuum gasification. Table 1 shows the type, size, and characteristics of the 10 biomass samples.

3.2. Experiment Facility

The Manufacturing Laboratory of the Mechanical Engineering Department, Faculty of Engineering, Subang University, is a place where research and testing are carried out. The system is designed to convert soaked biomass into gas through a vacuum pressure process, thereby enabling the extraction of valuable gas for further analysis. Laboratory technicians carefully monitor the gasification process, and record temperatures throughout the experiment. Fig. 2 depicts a schematic diagram of the soaked biomass vacuum pressure gasification system used in this experiment. The experimental facility is equipped with a gas and ash separation cyclone, a heat exchanger to cool the syngas, a cooling tower, a ¼ HP cooling water pump, a 1 HP suction pump, and a syngas burner.

Reactor temperature measurements during the process were carried out using five temperature sensors, consisting of one type K thermocouple and four type S thermocouples. The iron-coated type K thermocouple was placed at the top of the reactor with the code T0. The ceramic-coated S-type thermocouples placed underneath are T1, T2, T3, and T4, and the distance between the thermocouples is 20 cm. The data collected by this thermocouple is very important

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for monitoring the gasification process in the reactor. By having sensors at different heights, the data can accurately track temperature variations throughout the reactor. The real-time data logging provided by the Lutron TM-9747Sd and Lutron BTM-420SD data loggers allows for rapid analysis and adjustment of gasification parameters to ensure optimal performance Fig. 3.

Fig. 2. Schematic of a soaked biomass vacuum gasification system.

The experimental procedure is as follows: First, fill the reactor with charcoal; switch on the suction pump and cooling system; burn the charcoal as preheating until the gasification temperature (800–1200 °C) is obtained; and the syngas is burned with a lighter, mainly CO gas; if it does not burn, it will become toxic. The data logger began recording reactor temperature data;

the reactor had reached the gasification temperature; the soaked biomass was put into the reactor;

the syngas burner flame was kept lit; then the researcher looked at the gasification temperature indicator on the reactor. The experiment was carried out for 30 minutes, and each biomass replacement was given a transition time of 30 minutes by refilling the reactor with new charcoal.

The experiment was successful, with the gasification temperature and position stabilizing and remaining stable.

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Fig. 3. a) schematic of the temperature sensor position, and b) the reactor.

3.2. Compatibility Assessment of Failure Mode and Effect Analysis

Measuring the compatibility value of the soaked biomass vacuum gasification process using the Failure Mode and Effect Analysis (FMEA) approach. The FMEA (Failure Mode and Effect Analysis) method is a systematic method that has been widely used to determine, identify, and validate the risk of system function failure during operation [54], [55]. This method involves analyzing potential failure modes, their causes, and the effects they may have on the system. By applying the FMEA approach to the soaked biomass vacuum gasification process, researchers can assess the risks involved and identify ways to mitigate them. This systematic approach can help ensure the successful implementation of the gasification process and improve its overall efficiency and reliability.

Furthermore, this analysis also ensures the determination of the Risk Priority Number (RPN) method. Risk Priority Number (RPN) is a relationship between three parameters, namely severity (S), occurrence (O), and detection (D), which shows the level of risk of failure [13]. The higher the RPN number, the higher the risk of failure in a system, and conversely, the lower the RPN value, the smaller the occurrence of system failure [13], [14]. RPN calculation uses the equation :

𝑅𝑃𝑁=𝑆×𝑂×𝐷 ( 1 )

The determination of RPN criteria is based on the parameters of severity (S), occurrence (O), and detection (D) by providing a scale range of 1–10 points. Obtaining the highest RPN value

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usually has a greater risk of failure than a lower RPN value [55]. The severity parameter assesses the potential impact of a failure on the system or process, with a score of 1 indicating minimal impact and a score of 10 indicating a failure impact. Occurrence evaluates how often a failure is likely to occur, with 1 representing a rare occurrence and 10 representing a frequent occurrence.

Detection measures how easily a failure can be detected before it causes harm, with 1 being easily detectable and 10 being difficult to detect. By considering these factors, a comprehensive risk assessment can be conducted to prioritize and address potential failures. The scale system parameters for severity (S), occurrence (O), and detection (D) parameters are shown in Table 2.

Table 2. FMEA scale for the probability of severity (S), occurrence (O), and detectability (D) [55], [13].

Severity (S) Rating Occurrence (O) Rating Detectability (D) Rating

Almost never 1 No 1 Almost certain 1

Remote 2 Very slight 2 Very high 2

Very slight 3 Slight 3 High 3

Slight 4 Minor 4 Moderately high 4

Low 5 Moderate 5 Medium 5

Medium 6 Significant 6 Low 6

Moderately high 7 Major 7 Slight 7

High 8 Extreme 8 Very slight 8

Very high 9 Serious 9 Remote 9

Almost certain 10 Hazardous 10 Almost impossible 10

A failure mode is the way in which a failure can be observed in a system function, subsystem, or component. In determining the effects of failure of the gasification process, the basis for consideration is the thermochemical process that occurs in the gasifier related to the gasification temperature, the position of the oxidation zone, and the extent of the gasification zone. The ease and flexibility of the FMEA method provide an assessment of the compatibility and risk of failure of the gasification process. The main content of the FMEA method is the analysis of failure modes and the potential effects they cause. The combined process between the failure mode and the potential effects produced produces an output, which is then used as a recommendation for whether the gasification process is compatible or failed. The values for determining the FMEA method in

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the form of severity, occurrence, and detection are shown in Table 3 and can be described as follows:

1. Gasification temperature

The gasification temperature produces a clean and tar-free syngas product at temperatures above 1000 °C. The higher the temperature above 1000 °C, the lower the Risk Priority Number value. If the gasification temperature is below 1000 °C, the syngas product contains tar, and the lower the gasification temperature, the higher the tar content, so the risk priority number becomes greater until the temperature limit is 700 °C, where the gasification process stops [56].

This assessment method uses a decrease in temperature every 50 °C.

Table 3. The risk priority number assessment criteria for the gasification process use the FMEA method (severity (S), occurrence (O), and detection (D)).

Score Score Score

No The highest temperature aspect

S O D

Aspects of the position of the

oxidation zone S O D

Aspects of the Extent of the

Gasification Zone S O D 1 Temperature above 1050 °C 1 1 1 Position at the top and

hold on until the end 1 1 1 Full gasification zone 1 1 1 2 The temperature is 1000 °C 2 2 2 Lower and then return to

the original position 2 2 2 90% gasification

zone 2 2 2

3 The temperature drops to 950 °C 3 3 3 Position down 5 cm 3 3 3 80% gasification

zone 3 3 3

zone 4 4 4

zone 5 5 5

zone 6 6 6

zone 7 7 7

zone 8 8 8

zone 9 9 9

zone 10 10 10

2. Position of the oxidation zone

The gasification process requires a sufficient time span so that the production of syngas is abundant and rich, so the position of the oxidation zone must be above that for downdraft gasifiers. The risk priority number assessment is given by the fact that the position of the gasification zone is at the top with a small value, and as it goes down, the risk priority number gets bigger. The boundary position of the oxidation zone is at the bottom of the reactor because

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the gasification process will fail or stop [11], [57]. This assessment method uses a decrease in position every 10 cm.

3. Length of gasification zone.

Another important factor so that the gasification process can take place well is the length of the gasification zone, where the temperature below the oxidation zone is above 800 °C for use in the reduction process [30]. If the gasification zone is full from the position of the oxidation zone to the bottom of the reactor, you get a small Risk Priority Number value, and vice versa, if the gasification zone is 10%, you get a large Risk Priority Number value [11], [57]. This assessment method uses a decrease in the percentage area of the gasification zone every 10%.

4. Results and Discussion

4.1. Bamboo Biomass

The experimental results of the bamboo biomass vacuum gasification test are shown in Fig.

4. The reactor temperature profile is plotted as a function of temperature, experimental time of 30 minutes, and reactor depth from the top of 0 (T0), 20 cm (T1), 40 cm (T2), 60 cm (T3), and 80 cm (T₄). Temperatures are color-coded; red represents the highest temperature (1000 °C), purple represents the lowest temperature (ambient temperature), and other colors descend from red to purple. The color coding helps visualize the temperature distribution within the reactor, with a clear gradient from red to purple.

Fig. 4 shows the reactor temperature, which is capable of producing a temperature range of 963–1277 °C with a dominant temperature of 1083 °C. The initial temperature of the experiment was 1122 °C with a position of 30 cm, then the position of the oxidation zone dropped to 40 cm at the end of the experiment. The operator's lack of control over the wetness level of the biomass caused the position of the oxidation zone to fall in the 25th minute. At the last minute, the position of the oxidation zone rose slightly because the wettability level of the biomass was more controlled. The gasification zone in the bamboo biomass experiment was full with temperatures above 800 °C, which indicates that the gasification process will run well with the production of rich and tar-free syngas. This bamboo biomass is classified as solid biomass, is not hydroscopic, and has a flat shape so that it can produce high temperatures consistently and evenly at the bottom of the reactor. Temperatures decrease as biomass supply slows. In general, the gasification zone is

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full from top to bottom of the reactor, so the risk of failure is very small. Overall, the experiments show that bamboo biomass can maintain a high and consistent temperature during the gasification process. The size of the biomass plays an important role in this, as its small size allows for even distribution and high gasification temperatures. This results in a full gasification zone from top to bottom, minimizing the risk of failure and ensuring efficient conversion of biomass to energy. The area of the gasification zone in this experiment produced 100% ideal conditions because the temperature of the gasification zone reached the bottom of the reactor (above 800 °C). This experiment does not pose a risk of failure; even the syngas are tar-free. The weakness is that there is a decrease in the position of the oxidation zone at the end of the experiment. Improving temperature control in the gasification zone will be critical to achieving optimal conditions for experiments.

Fig. 4. Bamboo biomass gasification temperature

FMEA calculations for bamboo biomass are shown in Table 4. The severity, occurrence, and detection ratings for each failure mode were carefully assessed to determine an overall risk priority number (RPN) of 29.

Table 4. FMEA calculations for bamboo biomass FMEA Analysis No Assessment Aspects

Severity Occurrence Detectability RPN

1 The average temperature is 1083 C 1 1 1 1

2 The position drops 10 cm 3 3 3 27

3 Full gasification zone 1 1 1 1

Total RPN 29

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4.2. Rambutan 1 Wood Biomass

The experimental results of the soaked biomass vacuum gasification test for Rambutan wood 1 biomass are shown in Fig. 5. The number and color notation symbols displayed in Fig. 5 are the same as in Fig. 4

Fig. 5 shows the reactor temperature, which is capable of producing a temperature range of 839–1071 °C with a dominant temperature of 956 °C. The initial temperature of the experiment was 859 °C with a position of 20 cm, then the temperature decreased to 800 °C with a position of 40 cm. The operator's lack of control over the wetness level of the biomass causes the temperature and position of the oxidation zone to drop. In the 5th minute, the temperature of the oxidation zone rises to a position of 30 cm because the wetness level of the biomass is more controlled. The more controlled condition of one water-soaked rambutan can increase the temperature and position of the oxidation zone. Rambutan biomass 1 is a type of hardwood biomass, not hydroscopic, and of medium size (length 10 and diameter 2-3 cm), capable of producing and maintaining temperatures that do not drop below 800 °C. The area of the gasification zone in this experiment produced 66,47% of ideal conditions due to the temperature of the gasification zone not reaching the bottom of the reactor (temperature above 800 °C). This experiment does not result in a risk that the gasification process will fail or stop because the temperature does not drop below 800 °C and the position of the oxidation zone remains in the upper position. The weaknesses are temperatures below 1000 °C, and the gasification zone area is not yet full, so the syngas are not tar-free.

Improving the temperature control in the gasification zone will be crucial to achieving optimal conditions for the experiment.

Fig. 5. Rambutan 1 gasification temperature.

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FMEA calculations for rambutan 1 biomass are shown in Table 5. The severity, occurrence, and detection ratings for each failure mode were carefully assessed to determine an overall risk priority number (RPN) of 118.

Table 5. FMEA calculations for rambutan 1 biomass FMEA Analysis No Assessment Aspects

1 The average temperature is 956°C 3 3 3 27

3 66,47 % gasification zone 4 4 4 64

Total RPN 118

4.3. Rambutan 2 Wood Biomass

The experimental results of the soaked biomass vacuum gasification test for Rambutan wood 2 biomass are shown in Fig. 6. The number and color notation symbols displayed in Fig. 6 are the same as in Fig. 4.

Fig. 6. Rambutan 2 gasification temperature

Fig. 6 shows the reactor temperature, which is capable of producing a temperature range of 809–1065 °C with a dominant temperature of 916 °C. The initial temperature of the experiment was 920 °C at the 20 cm position, then the oxidation zone position decreased to 7 minutes at the 40 cm position. Furthermore, the relative temperature position of the oxidation zone remained at a depth of 40 cm until the end of the experiment. Rambutan biomass 2 is a type of hardwood biomass that is not hydroscopic, large (15 cm long and 2-3 cm in diameter), and capable of producing and maintaining temperatures not below 800 °C. The area of the gasification zone in this experiment produced 56% ideal conditions because the temperature of the gasification zone did not reach the bottom of the reactor (temperature above 800 °C). This experiment does not pose

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a risk of failure or stopping the gasification process because the temperature does not drop below 800 °C and the position of the oxidation zone remains in the upper position. The weakness is that syngas is not tar-free because the temperature is below 1000°C and the gasification zone area is not full because the biomass is large and the gasification temperature is not evenly distributed.

Apart from that, there was also a decrease in the position of the oxidation zone from 20 cm to 40 cm, which was a weakness of this experiment. Improving temperature control in the gasification zone is essential to achieving optimal conditions for experiments with smaller biomass sizes.

Implementing a temperature control system with a smaller biomass size can help ensure that the gasification temperature is distributed evenly, resulting in more efficient production of tar-free syngas. Maintaining the position of the oxidation zone is also beneficial for producing richer syngas. By addressing these shortcomings, future experiments with smaller biomass sizes may provide more successful results.

FMEA calculations for rambutan 1 biomass are shown in Table 6. The severity, occurrence, and detection ratings for each failure mode were carefully assessed to determine an overall risk priority number (RPN) of 405.

Table 6. FMEA calculations for rambutan 2 biomass FMEA Analysis No Assessment Aspects

1 The average temperature is 916 °C 4 4 4 64

Total RPN 405

4.4. Coconut Shell Biomass

The experimental results of the soaked biomass vacuum gasification test for coconut shell biomass are shown in Fig. 7. The number and color notation symbols displayed in Fig. 7 are the same as in Fig. 4.

Fig. 7 shows the reactor temperature, which is capable of producing a temperature range of 900–1098 °C with a dominant temperature of 1001 °C. The initial temperature of the experiment was 900 °C with a position of 40 cm, and the position remained until the end of the experiment at 930 °C. Coconut shells are a type of hardwood biomass that is not hydroscopic, is small, flat (3 mm thick and 2-4 cm in diameter), and is capable of producing and maintaining a temperature of

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around 1000 °C. The area of the gasification zone in this experiment produced ideal conditions of 65.63% because the temperature of the gasification zone did not reach the bottom of the reactor (temperature above 800 °C). This experiment does not pose a risk of failure or stopping the gasification process because the temperature does not drop below 800 °C and the position of the oxidation zone remains in the upper position. The weakness is that syngas are not tar-free because the temperature is not above 1000°C and the gasification zone area is not yet full. Increase the position of the upper gasification zone to achieve optimal conditions for this experiment.

Maintaining the position of the oxidation zone is also beneficial for producing richer syngas. By overcoming these shortcomings, future experiments with even higher oxidation zone positions will probably provide more successful results.

Fig. 7. Coconut shell gasification temperature.

FMEA calculations for coconut shell biomass are shown in Table 7. The severity, occurrence, and detection ratings for each failure mode were carefully assessed to determine an overall risk priority number (RPN) of 80.

Table 7. FMEA calculations for coconut shell biomass FMEA Analysis No Assessment Aspects

Severity Occurrence Detectability RPN 1 The average temperature is 1001

°C

2 2 2 8

2 Its position is relatively stable 2 2 2 8

Total RPN 80

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4.4. Corn Cob Biomass

The experimental results of the soaked biomass vacuum gasification test for corn cob biomass are shown in Fig. 8. The number and color notation symbols displayed in Fig. 8 are the same as in Fig. 4.

Fig. 8. Corncob gasification temperature.

Fig. 8 shows the reactor temperature, capable of producing a temperature range of 773–

1006 °C with a dominant temperature of 836 °C. The initial temperature of the experiment was 938 °C at a position of 20 cm, then the position of the oxidation zone decreased to 35 cm at the 7th minute. Furthermore, the relative temperature position of the oxidation zone remained at a depth of 40 cm until the end of the experiment. Corncob biomass is a type of softwood biomass that is hydroscopic, medium-sized (10 cm long and 3-5 cm in diameter), and unable to produce and maintain temperatures above 800 °C. The percentage of gasification zone area to the total ideal gasification zone area is 39.18% (temperature above 800 °C). This experiment has a risk of failure or stopping the gasification process because the temperature is below 800 °C and the position of the oxidation zone drops by 20 cm. Corn cobs are hydroscopic and, if soaked, will absorb more water than hard biomass [41]. Biomass with a high water content will absorb a lot of heat during the drying process. The heat absorbed in the drying process will cause the gasification temperature to drop to 730 °C [10], [47], and [50]. Maintaining a gasification temperature of at least 800 °C is critical for the success of the process, as a lower temperature can hinder biomass conversion into syngas. Additionally, the absorption of excess heat by high-moisture biomass during the drying stage can further contribute to a drop in temperature within the reactor. Reducing the gasification temperature will cause other processes to be less than optimal, and the risk of failure will be high.

Maintaining a temperature above 800 °C and the position of the oxidation zone are also beneficial

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for producing richer syngas. By overcoming these shortcomings, corncob trials not suited to water- soaked conditions with smaller biomass sizes may provide more successful results.

FMEA calculations for corn cob biomass are shown in Table 8. The severity, occurrence, and detection ratings for each failure mode were carefully assessed to determine an overall risk priority number (RPN) of 593.

Table 8. FMEA analysis calculations for corn con biomass FMEA Analysis No Assessment Aspects

Total risk priority number (RPN) 593 4.6. Palmyra Shell Biomass

The experimental results of the soaked biomass vacuum gasification test for corn cob biomass are shown in Fig. 9. The number and color notation symbols displayed in Fig. 9 are the same as in Fig. 4.

Fig. 9. Palmyra shell gasifikasi temperature

1079 °C with a dominant temperature of 956 °C. The initial temperature of the experiment was 1079 °C at a position of 15 cm, then the position of the oxidation zone decreased to a position of 30 cm at the 3rd minute, dropping back to 60 cm at the 20th minute until the experiment was finished. Palmyra shell biomass is a type of hardwood biomass in the shape of a large bowl or hemisphere (2-4 mm thick and 5–10 cm in diameter) and is unable to maintain the position of the oxidation zone at the top of the reactor. The area of the gasification zone in this experiment

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produced ideal conditions of 48.52% because the temperature of the gasification zone did not reach the bottom of the reactor (temperature above 800 °C). This experiment has a risk of failure or cessation of the gasification process because the position of the oxidation zone drops to 60 cm.

Palmyra shells are bowl-shaped so that the reactor space becomes smaller and the position of the oxidation zone decreases. Biomass used as material for the oxidation reaction process in small quantities will quickly run out and shift to the bottom, where there is still biomass, and so on [7].

This could result in an incomplete gasification process and a decrease in gasification efficiency. It is crucial to carefully monitor and adjust the position of the oxidation zone to ensure optimal conditions for the gasification reaction to take place. Insufficient biomass filling the reactor space will cause the biomass as fuel to run out quickly, and the combustion rate will continue to decrease to the bottom of the reactor. Decreasing the position of the oxidation zone will cause other processes to be less than optimal, and the risk of failure will be high. Finally, the position of the oxidation reaction that produces heat is at the bottom, where the charcoal has been used up, so the temperature drops to below 700 °C [50]. The reduction reaction process requires sufficient temperature and time to be optimal [9]. If this experiment is continued for a longer time, it will cause the gasification process to stop. Additionally, further research and experimentation may be necessary to find the ideal reactor design and operating parameters for maximum gasification efficiency when using Palmyra shells as a biomass feedstock.

FMEA calculations for palmyra shell biomass are shown in Table 9. The severity, occurrence, and detection ratings for each failure mode were carefully assessed to determine an overall risk priority number (RPN) of 1243.

Table 9. FMEA calculations for palmyra shell biomass FMEA Analysis No Assessment Aspects

Total RPN 1243

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4.7. Gmelina Wood Biomassa

The experimental results of the soaked biomass vacuum gasification test for gmelina wood biomass are shown in Fig. 10. The number and color notation symbols displayed in Fig. 10 are the same as in Fig. 4.

Fig. 10. Gmelina gasification temperature

1024 °C with a dominant temperature of 932 °C. The initial temperature of the experiment was 932°C at the 20 cm position, then the oxidation zone position was reduced to 7 minutes at the 40 cm position. Furthermore, the relative temperature position of the oxidation zone remained at a depth of 40 cm until the end of the experiment. Gmelina wood biomass is a type of hardwood biomass that is not hydroscopic, medium-sized (15 cm long and 2-3 cm in diameter), and capable of producing and maintaining temperatures not below 800 °C. The area of the gasification zone in this experiment produced ideal conditions of 52.81% because the temperature of the gasification zone did not reach the bottom of the reactor (temperature above 800 °C). This experiment does not pose a risk of failure or stopping the gasification process because the temperature does not drop below 800 °C and the position of the oxidation zone remains in the upper position. The weakness is that syngas is not tar-free because the temperature is below 1000 °C, and the gasification zone area is not yet full because the biomass is relatively large and the gasification temperature is uneven. Apart from that, there was also a decrease in the position of the oxidation zone from 20 cm to 40 cm, which was a weakness of this experiment. Improving temperature control in the gasification zone is essential to achieving optimal conditions for experiments with smaller biomass sizes. Implementing a temperature control system with smaller biomass sizes can help ensure that gasification temperatures are evenly distributed, resulting in more efficient production of tar-free

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syngas. Maintaining the position of the oxidation zone is also beneficial for producing richer syngas. By addressing these shortcomings, future experiments with smaller biomass sizes may provide more successful results.

FMEA calculations for gmelina wood biomass are shown in Table 10. The severity, occurrence, and detection ratings for each failure mode were carefully assessed to determine an overall risk priority number (RPN) of 459.

Table 10. FMEA analysis calculations for gmelina wood biomass FMEA Analysis No Assessment Aspects

Total RPN 459

4.8. Rubber Wood Biomass

The experimental results of the soaked biomass vacuum gasification t