Experimental investigation of producer gas effects on coated pipelines in biomass downdraft gasifier system

This research examines the performance of epoxy, ceramic, and graphene coatings on stainless steel 316 in a producer gas environment, focusing on corrosion and erosion resistance. This research aimed to identify the most effective coating for applications in harsh gasification environments. In this research, various analyses, including microstructural examination, hardness and weight measurements, FESEM analysis, and EDAX analysis, were conducted to evaluate the performance of the coatings. The producer gas was passed on to all the coated samples for a period of 100 h. The significant findings include the superior corrosion and erosion resistance of ceramic-coated stainless steel, as evidenced by low weight fluctuations, maintained hardness levels, and elemental stability. Graphene coatings exhibit high hardness but increased porosity, raising concerns about durability, while epoxy coatings are vulnerable to gas-induced structural alterations. The inclusion rating analysis underscored the ceramic coatings’ ability to preserve consistent material properties. Overall, ceramic coatings have emerged as the preferred option for gasification environments due to their structural resilience, inclusion integrity, and elemental stability. Considering the inclusion integrity, mechanical strength, weight stability, and elemental stability, ceramic-coated stainless steel 316 samples exhibit better resistance toward producer gas influence. This research contributes valuable insights for material selection in applications exposed to harsh gasification environments, emphasizing the importance of coating selection for long-term durability and performance.


Introduction
Biomass gasification is a promising technology for converting organic materials into usable gaseous fuel, primarily composed of carbon monoxide, hydrogen, and methane [1][2][3].This renewable energy process offers significant potential for sustainable energy production and addresses environmental concerns associated with fossil fuel dependency.Gasification involves the thermal conversion of biomass in the presence of a controlled amount of oxygen or steam, resulting in the production of a combustible gas known as producer gas or syngas.The utilization of biomass resources, including agricultural residues, forestry waste, and energy crops, makes gasification an attractive option for decentralized energy generation, particularly in rural and off-grid areas [2,4].
Gasification encompasses several interconnected stages, including drying, pyrolysis, combustion, and gasification.During the drying phase, moisture in the biomass is removed through heating, which prepares the feedstock for subsequent thermal conversion.Pyrolysis involves the decomposition of biomass in the absence of oxygen, resulting in the formation of volatile compounds and char [5,6].These volatile gases undergo further reactions in the combustion and gasification zones, where they react with oxygen or steam to produce the desired syngas.Gasification can occur in various reactor configurations, such as fixed-bed, fluidized-bed, and entrained-flow reactors, each offering distinct advantages in terms of efficiency and gas quality [7,8].
Despite its potential, biomass gasification faces several challenges that hinder its widespread adoption and commercialization.One of the primary challenges is the formation of tar and other impurities during the gasification process.Tar compounds, comprising complex hydrocarbons and particulate matter, can cause operational issues such as equipment fouling, corrosion, and reduced efficiency [9,10].Ensuring reliable and stable operation of gasification systems, particularly at small and medium scales, remains a significant challenge due to variations in feedstock properties, reactor design, and operating conditions.Additionally, safety concerns, including fire, explosion, and toxic gas emissions, pose risks during the startup, shutdown, and transient operation of gasification plants [11,12].
Numerous studies have focused on developing strategies to mitigate tar formation and improve the quality of producer gas in biomass gasification processes.Md Mashiur Rahman et al innovatively designed and optimized gasifier components such as nozzles and combustors to reduce the tar content in producer gas [5].
The experimental findings demonstrate the potential to produce gas with minimal tar concentrations suitable for diverse applications, including power generation by emphasizing factors such as the recirculating ratio and combustion degree of volatiles [8].New gasifier component designs aim to enhance the mixing between pyrolysis gases and gasifying air, reducing tar formation.The results show promising outcomes in tar reduction, and advancing biomass gasification technologies [4].Safety protocols address critical startup concerns, minimizing fire, explosion, and toxic gas emission risks.This research underscores the multidimensional nature of biomass gasification, integrating technical innovations, optimization strategies, and safety measures.
Research has shown that factors such as temperature, residence time, biomass composition, and gasification agent influence tar formation and composition [13].Various reactor configurations, such as downdraft, updraft, and circulating fluidized bed gasifiers, have been investigated to minimize tar content and enhance gasification efficiency.Furthermore, the integration of tar removal technologies, including catalytic cracking, thermal reforming, and tar filtration, has shown promising results in reducing tar levels and improving gas quality [5,14].
Recent advancements in gasifier design and component optimization have contributed to tar reduction and improved gasification performance.Studies have explored novel approaches, such as nozzle inclination angles, swirl combustors, and recirculation systems, to enhance mixing between pyrolysis gases and gasifying agents [5,6].These optimization strategies aim to increase the residence time, promote a uniform temperature distribution, and enhance the thermal cracking of tar compounds.Additionally, advancements in materials science have led to the development of high-temperature-resistant coatings and refractory materials, which improve the durability and longevity of gasifier components exposed to harsh operating conditions.
Safety during biomass gasification startup is paramount for preventing accidents and ensuring the reliable operation of gasification systems.Previous research has highlighted the importance of following standardized procedures and implementing safety protocols during startup, shutdown, and maintenance activities [15][16][17].Hazard analysis techniques, such as hazard and operability studies (HAZOP) and failure mode and effects analysis (FMEA), have been utilized to identify potential risks and develop preventive measures.Proper personnel training, equipment inspection, and emergency response planning are essential for ensuring the safe and efficient operation of gasification plants [18,19].
Although significant progress has been made in the field of biomass gasification, several research gaps and challenges remain to be addressed.These include the development of cost-effective tar removal technologies, the optimization of gasifier performance under varying feedstock conditions, and the integration of gasification systems with downstream conversion processes [6,20].Additionally, there is a need for further research on safety protocols, hazard mitigation strategies, and risk assessment methodologies to ensure the reliable and sustainable operation of biomass gasification plants.In the recent study reported by our team, the pipelines from the scrubber region are affected due to producer gas, showing significant changes to structural integrity, hardness, and weight fluctuations [21].The present study aimed to address the property change issues that occur in producer gas-influenced coated pipelines from the scrubber region of the system.

Methodology
The proposed research methodology involves coating AISI 316 stainless steels with epoxy, ceramic, and graphene materials to mitigate corrosion and erosion issues in producer gas pipelines.The coating process includes powder gun coating for epoxy, spraying silicon dioxide for ceramic, and a combination of silicon dioxide and graphite for graphene.After coating, the materials undergo a curing process in an oven set at specific temperatures.For this research, a total of three replications were conducted for each experimental condition or coating type to ensure the reliability and consistency of the results.Microstructural analysis, hardness measurement, particulate inclusion analysis, and porosity analysis were conducted on the coated materials before and after exposure to the producer gas.The inclusion rating analysis followed the IS 4163:2004 standards to examine various groups of elements present in the materials.Weight measurements and FESEM analysis were also performed to evaluate mass variations and porosity, respectively.EDAX analysis was conducted to determine the effects of the elemental composition and erosion on the coated materials.

Experimental setup of the producer gas
Gasification operation has been conducted using 2-kW downdraft gasifier.The gasification process begins with the introduction of an external fire source and woody biomass into the gasifier, where air is pumped into the oxidation zone, and the resulting gas is then removed from the gasifier.The pumping process in this research is similar to that in a previous study in which an LPG burner was used [4]; however, in our experiment, an external fire was used, and ignition started in the reactor when the fire source was admitted.Produced gas passes through various stages, from the reactor to the filter, and then through the scrubber, the producer gas passes through.The produced gas usually exhibits high temperatures.Figure 1 shows the schematic representation of the producer gas setup.
As the air passes through the wet scrubber, the particles are effectively removed, reducing the temperature.However, despite proper design, air entering the filter subsequently retains some moisture, which can pose a risk of damage to piping and filter components.To address this concern, all the pipelines and reactors controlling gas production are constructed of AISI 316 stainless steel.Figure 2 shows the producer gas setup.Table 1 shows the composition of the AISI 316 stainless steel used in this research.

The operation of the proposed system
The proposed system is composed of pipelines for gas production and distribution and is broken down into several phases.While each step in this system serves a specific purpose, they all cooperate to maximize the efficiency of producer gas conditioning and extraction.Figure 3 shows the operation of the proposed system at various stages.

Producing gas in the reactor
The reactor, which doubles as the main gasification site, is at the center of the system.After adding the wood biomass, it is ignited, and sufficient gas is admitted for proper combustion.High temperatures cause the biomass to decompose, producing producer gas thermally.The system's subsequent stages are supported by three conversion phases-combustion, reduction, and pyrolysis.

Gas purification scrubber (wet scrubber)
After the gas is produced within the gasifier, it undergoes a crucial treatment process in the form of scrubbing before further utilization.Scrubbing is a pivotal step aimed at the removal of contaminants and pollutants from the generated gas stream.This process involves the use of a scrubber, a device designed to effectively capture and remove various impurities present in the gas.These impurities primarily consist of dust particles, fly ash, and specific gases such as ammonia and sulfur compounds.The scrubber achieves this purification by employing a liquid medium, typically water, which acts as a solvent to absorb and neutralize pollutants.The scrubbing process plays a significant role in environmental protection by substantially reducing the harmful emissions released into the atmosphere.By efficiently removing pollutants, a scrubber aids in mitigating air pollution and promoting cleaner air quality.Additionally, the removal of contaminants enhances the combustion efficiency of gas when utilized as a fuel source, contributing to improved overall performance and reduced environmental impact.

Filtration for improving gas quality
The next step in eliminating contaminants and any leftover particulate matter that might have passed through the scrubber is filtering the gas.Because it removes solid pollutants and fine particles such as ash and dust, this step is crucial for enhancing the overall quality and cleanliness of the producer gas.Because it serves as a barrier    to prevent particulate matter from fouling or harming downstream machinery, including turbines, engines, and valves, the filtration stage is crucial.Furthermore, by reducing particulate matter emissions into the atmosphere, the filter helps ensure compliance with environmental regulations.

Working conditions
Woody biomass is used as the input feed for the downdraft biomass gasifier.During the experiment, the producer gas setup was operated for a 100-h batch operation.The resultant producer gas consists of carbon monoxide (CO), hydrogen (H2), methane (CH4), carbon dioxide (CO2), and nitrogen (N2).The operating temperatures of the various stages in the system ensure the quality of the producer gas.Hence, it is also essential to consider the operating temperatures at various stages of the gasification process.Temperatures above 600 °C, 100 °C, 85 °C, and 50 °C were maintained for the reactor, scrubber pipeline, filter pipeline, and gas-out pipeline, respectively.The 2.47 m s −1 average gas-out velocity at the outlet, which guarantees a directed and regulated flow of the conditioned producer gas, has a significant influence on downstream operations.The percentage ranges for each element are shown in table 2, which provides the elemental composition of the producer gas.The obtained producer gas was identical to that reported in the literature [6].

Coating procedure for each material and property
Epoxy polyesters are coated using the powder gun coating method, which is a commonly used technique to produce consistent and long-lasting coatings.The process parameters are precisely regulated to guarantee the best coating quality.The spray gun has a 15 mm nozzle and runs at 45 PSI pressure.A voltage of 62 kV and a current of 28 amps ensure efficient powder deposition onto the substrate, enabling electrostatic application.The coated samples were put through a curing process in an oven set at 120 °C after the powder was applied.For the first five minutes of the curing process, the temperature was maintained between 95 and 98 °C to allow the coating time to stabilize.The coated samples are then baked for ten minutes at 180 °C to promote the crosslinking and curing reactions that improve the adhesion and durability of the coating.The last step is to finish the curing process by progressively decreasing the oven temperature to room temperature.The coating has a thickness of 112 μm.
One method is to apply a ceramic coating (Coating 2) by spraying silicon dioxide.For four hours, this technique ensures even and comprehensive coverage.The resultant ceramic coating offers a robust and protective layer with a coating thickness of 112 μm.For graphene coating, the combination of silicon dioxide and graphite was applied via, a four-hour spray-coating process with a thickness of 112 μm.The microstructure of the uncoated SS 316 steel exhibits a distinctive austenitic structure with a distinct grain structure.The results of the microstructural examination are shown in figure 4. A closer look reveals a uniform distribution of ferrite and pearlite phases in the material, indicating a typical metallurgical composition.However, following 100 h of exposure to the producer gas, there was a discernible change in the microstructure.A wider grain boundary and the initiation of carbide precipitation are indicators that the gasification environment might impact the structural integrity of the material.

Epoxy-coated stainless steel
Figure 5 shows the uniform and smooth coating, demonstrating the effective application of epoxy.Stainless steel retains its original visible underlying structure and grain boundaries.After 100 h of operation, the material exhibited interesting microstructural changes.A noticeable deterioration is indicated by microcracks and delamination in the epoxy coating, as shown in figure 5. Furthermore, the possibility of weaknesses resulting from prolonged exposure to the gasification process is increased by localized corrosion close to the substratecoating interface.The distinct layered structure of graphene is visible in the microstructure of stainless steel coated with graphene (figure 6).First, the graphene layer adhered uniformly to the stainless-steel substrate, demonstrating a promising reinforcement effect.After being exposed to the producer gas for 100 h, the microstructure showed remarkable stability.The structural integrity of the graphene layer is preserved, indicating that it is more resilient to severe gasification environments.The remarkable ability of graphene to prevent the formation of corrosion-related features highlights the potential use of this material as a protective coating.

Stainless steel ceramic
The microstructure of this material reveals the thick layer of uniformly applied ceramic coating protecting the substrate (figure 7).The fine-grained structure of the ceramic coating in its pure form increases the resistance of the material to external influences.Following a 100-h exposure to producer gas, the microstructure of the ceramic coating demonstrates resilience.The ceramic layer withstands extended gasification conditions, as observed by the lack of signs of deterioration or structural changes.Microstructural analysis indicated that the ceramic coating effectively preserved the material's protective qualities, increasing the material's resilience in the gasification environment.

Inclusion rating
In this work, inclusion rating analysis was performed on each coated steel specimen both before and after exposure to producer gas, following the standard protocols described in IS 4163:2004.Table 3 shows the inclusion rate of each coated material before and after the producer gas was passed.In this study, inclusion analysis was performed to examine the 4 different groups of elements present in the material before and after the producer gas was passed.The four different groups are denoted as groups A, B, C, and D. Group A represents the sulfide type, which is highly malleable, and the grain sizes are larger in length and width.Group B contained aluminate, and group C contained silicate.Group D represents the nondeformable globular oxide type with an angular or circular structure.The epoxy-coated material contains Groups D and B, according to the inclusion analysis.The results of the analysis show that the angular, non-deformable particles in Group B are 555 μm long and have a low aspect ratio.At a particle count of 25, Group D, or inclusions of the globular oxide type, are simultaneously detected.The same result was obtained in all the fields of inspection.The microstructure of the inclusions of epoxy-coated stainless steel before and after gas exposure is shown in figure 8.
The inclusion profile visibly changes as the epoxy-coated material is subjected to the producer gas.Apart from Groups D and B, which are still in existence, Group C is an entirely new category of inclusion.Group C consists of discrete, dark gray or black particles with different aspect ratios that are very malleable.These Group B inclusions have a length of 77 μm, which is observed in field 2. This change in the composition of the inclusions implies that the gasification process had an impact on the coating, which might have changed the structural properties of the material and created a new class of inclusions.
The inclusion analysis of the graphene-coated stainless steel revealed the presence of 4 Group D inclusions and two Group B inclusions with lengths of 555 μm in fields 2 and 3. Additionally, in field 2, along with group B, Group C, with a length of 77 μm, is present.In field 1 of the examination, 77 μm of Group B are present.Following gas exposure, Group B inclusions 555 μm in length were observed.Furthermore, group D inclusions of 4 counts are present.These results demonstrate the dynamic nature of the inclusions in graphene-coated stainless steel and the influence of producer gas exposure on the type, length, and number of inclusions observed.The microstructure of the graphene-coated stainless steel is shown in figure 9.
Ceramic-coated stainless steel inclusion analysis revealed the presence of Group B inclusions in various fields with lengths ranging from 17 to 555 μm (table 3).The microstructure of the inclusions is shown in figure 10.Additionally, group D inclusions are identified; counts of 1, 4, and 9 suggest that the material contains a variety of inclusions.Producer gas exhibits a discernible shift in its inclusion profile upon contact with ceramic-coated stainless steel.After gasification, Group B inclusions are still present in the material, but their length is constant at 555 μm.There are inclusions with counts of 4 and 9 in Group D as well.This shift in the inclusion composition suggested that the producer gas affected the ceramic coating, affecting the distribution and quantity of various inclusion types.

Hardness and weight measurements
The different stainless steel 316 coatings and materials at different distances from the surface were assessed using the hardness test results displayed in figure 11.The materials included as-received stainless steel 316 (A), stainless steel 316 influenced by producer gas (B), epoxy-coated stainless steel 316 (C), producer gas-influenced epoxy-coated stainless steel 316 (D), ceramic-coated stainless steel 316 (E), producer gas-influenced ceramiccoated stainless steel 316 (F), graphene-coated stainless steel 316 (G), and producer gas graphene-influenced stainless steel 316 (H).The hardness values are expressed in HV and vary between samples and distances.The producer gas-influenced stainless steel 316 has a slightly lower hardness (282.8HV) than the as-received stainless steel 316, which has the highest hardness (349.4HV) at a surface distance of 0.05 mm.The producer gasinfluenced epoxy-coated sample (D) has a harder surface than the epoxy-coated variant, which has a harder surface of 329.3 HV.The hardness of ceramic-coated stainless steel 316 (E) is 268.1 HV, with a noteworthy increase to 300.9 HV when influenced by producer gas (F).Graphene-coated stainless steel 316 (G) and producer-gas graphene-influenced stainless steel 316 (H) exhibited hardness values of 292.0 HV and 327.7 HV, respectively.The distance-dependent trend shows how different the coatings' hardnesses are; some materials show altered hardness when exposed to producer gas.The significance of material selection and coating efficacy in applications exposed to harsh environments is highlighted by these results, which demonstrate the potential influence of producer gas on the mechanical properties of stainless steel 316 and its coated variants.The weights of samples A to H were measured, and the following results were obtained: A, 4.11 g; B, 4.19 g; C, 4.19 g; D, 4.24 g; E, 4.09 g; F, 4.15 g; G, 4.10 g; and H, 4.15 g.The results are also shown in figure 12. Weight measurements provide important information about how different coatings affect the overall mass of stainlesssteel specimens.Weight differences between the coated samples may indicate differences in adhesion, coating thickness, or the addition of specific coating materials such as ceramic, epoxy, or graphene.

FESEM analysis
A porosity analysis using field emission scanning electron microscopy (FESEM) was performed on the materials formed after they were exposed to the gasification process.The results are shown in figure 13.The FESEM images showed that the material with the highest degree of porosity was epoxy-coated stainless steel.The percentage of the porosity is 23.32%.The material coated in graphene exhibited a significant porosity compared to that of its epoxy.Graphene-coated stainless steel has a porosity percentage of 18.23%.The FESEM analysis showed the outer structure of the graphene and voids in the graphene layer.These voids represent the degree of structural changes that are due to gas.Additionally, the porosity of graphene suggests that even though it has superior properties, the graphene coating is vulnerable to gas permeability.There was a noticeable trend, and reduced porosity was observed in the material coated with ceramic.The ceramic-coated stainless steel shows a reduced porosity of 9.09%.The FESEM image of the ceramic-coated material revealed a more compact and continuous coating structure, indicating greater resistance to gas-induced porosity.This investigation highlights the potential of ceramic coatings as efficient barriers against structural degradation and gas penetration, and it validates the expected properties of these materials.
Figure 14 shows the corroded areas of three distinct coated stainless-steel samples.It is evident from figure 13 that epoxy-coated stainless steel exhibits a greater degree of corrosion, accompanied by increased porosity.The graphene-coated material displays surface erosion, porosity, and pitting holes.In contrast, the ceramic-coated material exhibited a reduced level of erosion and porosity, with no observed pitting holes.The analysis underscores the superior efficacy of ceramic coatings in resisting corrosion, as evidenced by the lower occurrence of erosion and pitting holes.

EDAX analysis
The results of the energy dispersive x-ray analysis (EDAX) of the gas-passed coated materials are shown in figure 15.The results of the EDAX suggest the elemental composition and features of the erosion caused by the gasification process.The various elements in the epoxy-coated stainless steel were carbon (29.35%), oxygen (11.77%), sulfur (0.15%), calcium (0.20%), iron (6.65%), barium (0.07%), silicon (0.05%), and chlorine (0.11%).Notably, erosion is indicated by carbonaceous deposition.A higher carbon content in epoxy-coated stainless steel indicates surface erosion due to producer gas.On the other hand, less erosion is suggested by the composition of stainless steel coated with graphene.Carbon (48.61%), oxygen (8.39%), silicon (0.58%), sulfur (0.24%), manganese (0.84%), chromium (1.32%), and iron (9.30%) are the main components.The presence of carbon and the relative decrease in the percentage of other elements in the graphene-coated stainless steel shows the protective role of the graphene coating.On the other hand, the ceramic-coated material consists of silicon (0.73%), manganese (3.22%), chromium (4.65%), iron (25.47%), carbon (38.46%), oxygen (4.51%), and copper (0.44%).Because of its inherent hardness and resistance to chemical deterioration, ceramic coatings exhibit less erosion than both epoxy and graphene coatings.The porosity of the materials and the observed erosion highlight how crucial coating durability is in gasification environments.From the analysis, it is concluded that the ceramic coating is a more resilient option, offering improved defense against the caustic effects of the producer gas.

Limitations of the research
Several limitations were encountered in this research, which may have affected the interpretation of the results and future research directions.First, while the coating process was meticulously executed, it may have introduced variability in application techniques, potentially affecting the consistency of the results across samples.To address this limitation, standardized coating procedures and stringent quality control measures were implemented.Second, the use of AISI 316 stainless steel as a substrate material may limit the applicability of the findings to other materials commonly used in industrial settings.To address this limitation, future research could investigate the performance of coatings on a wider range of substrate materials, providing more comprehensive insights.Furthermore, laboratory-scale experiments may not fully replicate the complex conditions encountered in real-world applications, which may affect the extrapolation of findings.To address this limitation, future studies could include field testing to validate laboratory findings in real-world settings.Furthermore, the scope of this study was limited to three types of coatings (epoxy, ceramic, and graphene), which may have overlooked the potential benefits of other emerging coating materials.Future research could explore novel coating formulations with distinct properties to broaden the range of available protective coatings for industrial applications.Finally, no long-term durability testing was performed in this study, which limits our understanding of the coatings' performance over long periods.Future research could include extended exposure testing to determine the durability and resilience of coatings under harsh environmental conditions.

Discussion
A thorough analysis of several variables, such as inclusion rate, microstructure, hardness, weight, EDAX, FESEM, and microstructure, offers insightful information about how various stainless steel coatings function in producer gas environments [22].These findings offer valuable information that enhances the suitability of coatings for gasification environments.Weighing the coated stainless-steel specimens provides a basic understanding of their total mass.Both before and after the samples in this study were exposed to producer gas, and their weights were recorded.Ceramic, graphene, and epoxy coatings were applied to the samples.In contrast to epoxy and graphene coatings, the ceramic coating on stainless steel varied in weight the least, suggesting less material loss or degradation.This demonstrates that ceramic coatings are a good option for applications where weight stability is important because they successfully maintain the integrity of the material [23].
Measurements of hardness offer valuable insights into the mechanical characteristics of coated materials.The results of the hardness test demonstrate that even after being exposed to producer gas, stainless steel with a ceramic coating demonstrates a strong resistance to deformation [24,25].For applications where mechanical strength is crucial, this resilience is vital.Although stainless steel coated with graphene is extremely durable, it becomes softer when exposed to gases.Thus, the hardness results emphasize the mechanical performance of ceramic coatings even more in harsh gasification environments.The elemental composition of the coated materials following their exposure to producer gas was clarified by EDAX analysis [26,27].Erosion and structural alterations are more likely due to the higher carbon content of the gas-passed epoxy coating.Graphene and ceramic-based coating compositions, on the other hand, exhibit greater erosion resistance.While the varied composition of ceramic coatings emphasizes their inherent resistance to erosion, the higher carbon content of graphene coatings suggests their protective qualities.These results validate the utility of ceramic coatings in preserving elemental stability and mitigating erosion caused by gases.
When coated materials are exposed to gas, FESEM analysis measures their porosity, which sheds light on the subsequent structural changes [28,29].The stainless steel coated with graphene exhibited a discernible increase in porosity, indicating potential defects in its gas permeability.On the other hand, the material coated with ceramic shows less porosity, suggesting a stronger resistance to structural alterations caused by gas [30,31].This observation is consistent with the theory that ceramic coatings improve their suitability for gasification environments by acting as effective barriers to gas infiltration.Microstructural analyses provide important details regarding the alterations in the internal structure of the materials.The microstructure of pure stainless steel is significantly altered when it comes into contact with producer gas.On the other hand, stainless steel coated with ceramics maintains its protective properties even after gasification changes its structural makeup.Nevertheless, after being exposed to gas, the epoxy-coated material shows signs of delamination and microcracks, suggesting possible weaknesses.The microstructure analysis of the material indicates that ceramic coatings perform better than other materials in maintaining the internal structure of the material during the difficult gasification process [32,33].
The types and amounts of inclusions present in the coated materials can be understood through inclusion rating analysis.Ceramic-coated stainless steel consistently exhibits very little variation in inclusion profiles when exposed to producer gas.The fact that the Group B inclusion lengths do not change indicates that the ceramic coating is resistant to changes caused by gasification.Nevertheless, dynamic changes in inclusion profiles are observed in both graphene and epoxy coatings, suggesting possible structural effects.These results show that ceramic coatings can preserve the integrity of the material even when gas changes the inclusion characteristics.

Conclusion
The performance of several coatings on stainless steel 316 exposed to producing gas is thoroughly evaluated in this study.Through examination of weight variations, hardness values, elemental composition analysis (EDAX), microstructural changes, and inclusion ratings, the materials' responses to gasification environments were evaluated.Ceramic coatings have emerged as effective in maintaining material integrity and resisting gasinduced alterations, displaying minimal weight fluctuations, retained hardness levels, and elemental stability.The microstructural analysis further confirmed the resilience of the ceramic coatings to structural changes, confirming their reliability and durability in gasification applications.While graphene coatings have shown promising properties, such as high hardness, their increased porosity has raised durability concerns.Epoxycoated stainless steel exhibited vulnerability to gas-induced structural alterations, underscoring the need for robust protective coatings.The inclusion rating analysis highlighted the superior ability of ceramic coatings to preserve consistent material properties, making them preferable for gasification environments.Future investigations may examine innovative coating compositions, carry out extended durability assessments, and confirm results via field trials for pragmatic implementation.Additionally, studies could expand to include a broader range of substrate materials to enhance the understanding of coating performance.

Figure 1 .
Figure 1.Schematic representation of the producer gas setup.

Figure 3 .
Figure 3. Various stages of producer gas production.

Figure 4 .
Figure 4. Microstructure of stainless steel before and after producer gas exposure.

Figure 5 .
Figure 5. Microstructure of epoxy-coated stainless steel before and after producer gas exposure.

Figure 6 .
Figure 6.Microstructure of graphene-coated stainless steel before and after coating producer gas exposure.

Figure 7 .
Figure 7. Microstructure of the ceramic-coated stainless steel before and after production Gas exposure.

Figure 8 .
Figure 8. Microstructure of epoxy-coated inclusions before and after coating producer gas exposure.

Figure 9 .
Figure 9. Microstructure of the inclusions in the graphene coating before and after coating producer gas exposed.

Figure 10 .
Figure 10.Microstructure of the inclusions in the ceramics before and after coating after producer gas exposure.

Figure 11 .
Figure 11.Hardness measurements of the pipeline materials.

Figure 12 .
Figure 12.Weights of the samples before and after coating.

Figure 13 .
Figure 13.FESEM analysis of porosity in coated materials after producer gas exposure.

Figure 14 .
Figure 14.Corrosion analysis of coated stainless-steel samples.

Figure 15 .
Figure 15.EDAX analysis of the elemental composition of the gas-passed coated materials.

Table 2 .
Composition of the produced producer gas.

Table 3 .
Inclusion analysis of different coated metals before and after gas exposure.