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Thursday, 7 October 2021

Study of Slope Stability of Tailings Dam Height Expansion from Elevation (RL) 2000m to RL 2035m at Hidden Valley Mine, Papua New Guinea

October 07, 2021Finite Element Analysis, Slope Stability Analysis, Tailings Dam No comments

ABSTRACT

The tailings dam height expansion from the initial RL of 2000 m to 2035 m at Hamata Tailings (Dam) Storage Facility (TSF) at Hidden Valley Mine in Papua New Guinea pose some risks in terms of slope stability conditions. In this study it is proposed to analyse the TSF at four stages. i.e.RL 2000, RL 2015, RL 2025 and RL 2035. Based on the design parameters and material properties, this study utilizes Phase 2 software to analyse the slope stability conditions of the TSF. The embankment construction methodology in stage 1 is downstream whereas the other stages (2-4) are upstream method of construction. Numerical Simulation (Modeling) of the TSF is done in four stages (1-4) with three parameters, (1) Simulation without Reinforcement; (2) Simulation with Reinforcement (s); and (3) Simulation with Seismicity. Simulation result(s) that give Critical Shear Strength Reduction Factor (SRF) of 1.3 or above is/are ideal for consideration in this study. The findings in this study is somewhat useful for the mining company for future height expansion plans for the TSF and also it is helpful to government for assessment purposes for future TSF height expansion proposals. Future Researchers may analyse other safety aspects not covered in this study.

Keywords: Tailings dam, slope stability analysis, Dam Height expansion, embankment, Shear Strength Reduction Factor(SRF), RL-Reduced Level(m), downstream construction method, Upstream Construction Method. Phase 2 Numerical Simulation, Reinforcement, Seismicity.

Google image of Hidden Valley TSF

Note: Full paper for this abstract is ready and can be accessed upon request via contact form in this website.

Monday, 29 March 2021

Prime Minister of Papua New Guinea on First Vaccination for COVID-19 in Papua New Guinea

March 29, 2021COVID-19 Vaccination, PNG No comments

The Prime Minister of Papua New Guinea, Hon.James Marape was the the First to take on the COVID-19 Vaccination in Papua New Guinea. The Vaccines arrived from Australia and there has been much talk and opposition to the vaccination and much fear among many citizens of the country but, overcoming all those critics, the PM was the first to take the vaccination.

This was to clear the atmosphere among the citizens having fear of taking the vaccines. The vaccines are not mandatory for citizens but priority will be given to the front line workers or the nurses and doctors. PNG citizens who are willing to take the vaccines will be allowed to get vaccinated.

PM James Marape is injected with Vaccine

Friday, 22 January 2021

Underground Coal Gasification - Experiment Report (Set-up, Igniting, Recording)

January 22, 2021Earth Resources Engineering, Hokkaido, Japan, Kyushu University, Underground Coal Gasification 6 comments

General information of Coal Gasification

Coal gasification is the process of producing syngas—a mixture consisting primarily of carbon monoxide (CO), hydrogen (H₂), carbon dioxide (CO₂), natural gas (CH₄), and water vapour (H₂O)—from coal and water, air and/or oxygen.

Historically, coal was gasified to produce coal gas, also known as "town gas". Coal gas is combustible and was used for heating and municipal lighting, before the advent of large-scale production of natural gas from oil wells.

In current practice, large-scale coal gasification installations are primarily for electricity generation, or for production of chemical feedstocks. The hydrogen obtained from coal gasification can be used for various purposes such as making ammonia, powering a hydrogen economy, or upgrading fossil fuels.

Alternatively, coal-derived syngas can be converted into transportation fuels such as gasoline and diesel through additional treatment, or into methanol which itself can be used as transportation fuel or fuel additive, or which can be converted into gasoline.

Natural gas from coal gasification can be cooled until it liquifies for use as a fuel in the transport sector.

Underground coal gasification (UCG) is an industrial gasification process, which is carried out in non-mined coal seams. It involves injection of a gaseous oxidizing agent, usually oxygen or air, and bringing the resulting product gas to the surface through production wells drilled from the surface. The product gas can be used as a chemical feedstock or as fuel for power generation. The technique can be applied to resources that are otherwise not economical to extract. It also offers an alternative to conventional coal mining methods. Compared to traditional coal mining and gasification, UCG has less environmental and social impact, though environmental concerns exist, including the potential for aquifer contamination.

Source: https://en.wikipedia.org/wiki/Coal_gasification#:~:text=Coal%20gasification%20is%20the%20process,known%20as%20%22town%20gas%22.

Activities - Daily Account of experiment

In this project of the Underground coal gasification simulation, it was done in a laboratory setting to analyze the potential of underground coal gasification for potential utilization of underground coal resources.

Figure 1 : Schematic diagram of the coal gasification model at laboratory setting

The purpose of this project was to simulate the coal ignition to extract the Hydrogen and Carbon Dioxide gas and other important gases. Other uses of in-situ coal by coal gasification include the production of electricity, coal tar among others but in this case the coal tar is of insignificant and considered as waste with water.

The account of the activities conducted during the experiment are outlined below.

Day 1

Set up the experiment especially connecting the sensor cables from the coal seam model to the sensor measuring equipment. Two (2) drill holes were created and installed cracking sensors and cemented. crack sensor cables were channeled to detect crack location while burning. The closest crack returns the highest reading.

All the sensor cables were connected to the sensor reading equipment and calibrated based on calibration standards and trial/tests done to ensure all good to go. The sensors were to measure temperature, cracking of coal, flow rate of gas emitting under atmospheric pressure.

Oxygen was prepared to connect into the model so that it will aid burning coal under enclosed setting and help in getting out the resultant gas/products from the coal burning face. LP gas was also used with a long copper tube and a ignition coil attached at the end of it for igniting the coal. All other necessary pipes were connected and ready for experiment.

All the set up was done and ready for ignition on the next day.

Figure 2 : Equipment set up completed and ready for measurement during coal burning

Day 2

Ignition of coal started in the morning by burning the ignition coil attached to the copper tube with electricity which is connected to the LP gas. When the ignition coil was red hot, LP gas was opened, and it flowed through the copper tube and flame burst. This set up was inserted into the coal seam and the coal seam was ignited in the model.

As the coal seam was burning in the model and producing smoke, the ignition coil setup removed, and oxygen was supplied into the enclosed area to aid burning and closed the inlet/outlet pipe or the regulator pipe. Oxygen also help in getting the resultant gas and moisture out from the burning face.

Electric buster fan was used to suck smoke away from the working area. At the regulator pipe, the emitted gas during the burning of the coal is collected via metal pipe and monitored and recorded at the laptop inside the laboratory. Excessive gas emitted at two exit pipes above the building was then lighted up by gas burner to continue burning to prevent smoke.

After some time, water is connected into the burning area via pipe to prevent excessive burning and protect non coal components of the model.

The gas produced from burning coal is a mixture of gas and moisture so there was a mixing chamber or collecting tank which was wrapped with clear hose and frozen water pumped through and the moisture content got condense which also contain coal tar and is collected at the bottom/tip of the storage tank and further stored away in storage containers for disposal.

Readings of the temperature, flowrate, cracking are recorded hourly on prepared data sheet. Readings were also recorded continuously on the equipment and data is stored in memory disks. The recording of data is done hourly and 24 hours for 4 days.

Figure 3 : Water and coal tar mixture collected at the condenser tank

Day 3

The hourly recording of temperature, cracking and flowrate under atmospheric condition continued.

The laboratory demonstrated and explained in simple terms the experiments to Junior High School Students. There were three set up on site at the research facility for students to observe:

1. (a)The explanation of coal and demonstration of how coal and rock in terms of their physical properties.

(b) The coal and gravels were burned, and the results showed that gravels cannot burn but coal can burn when ignited.

(c) Another set up was that, coal was placed in a glass tube closed at the opening and a small L tube is connected. Using gas burner, the glass tube containing coal was burned and gas was produced and emitted through the L tube and finally lighted by gas lighter and it was burning and students were amazed with this experiment.

Figure 4 : Burning coal in the glass tube as a demonstration of coal gasification

2. Explanation and demonstration of electricity generation by burning coal. Glass beaker was filled with water and firmly closed, and a tube connected via lid. This tube is then connected to a mini turbine with motor attached at the end and wiring was done to produce electricity and a light was produced. By using gas burner, the beaker with water was heated and high pressure steam produced which is directed via the tube and into the turbine which turns the turbine and as the turbine rotates, it powers the motor which converts the mechanical energy to electrical energy.

Figure 5 : Demonstration of steam turning the turbine to power the motor and a red light given out.

3. The third set up was the explanation of the setting up of the underground coal gasification process and procedures and the explanation of the model being set up.

Figure 6 : Schematic Diagram used to explain the coal gasification set up at laboratory.

Day 4

The hourly recording of temperature, cracking and flowrate under atmospheric condition continued and Hosted the another group of Junior High School Students and conducted the same experiments and explanation on the previous day .

Figure 7 : Junior High School Student and technical team on site after completion of explanations.

Day 5

Continued with hourly recording of temperature, cracking and flowrate under atmospheric condition and removing wastewater from tank and poured into storage containers for treatment before disposal.

Day 6

Recording of readings or measurements stopped at 03:00 on the 6th Day. All the connections dismantled, and experiment was completed and ready for clean up the area. Most of the equipment were disconnected and removed.

Another experiment at a small scale was prepared using small drums. 9 small drums were prepared by drilling the bottom at center and pipe inserted. Then poured mixed cement and let it dry. Then coal seams measured their weights and placed in the drums and packed cement again at top. Then it was left to dry and packed in the laboratory for experiment in September 2020. Sensors will be installed in those drums and follow the same procedure and recording.

Coal Samples

Drums ready for packing coal

Figure 8 & 9: Coal measured and ready for packing in drum as prepared on the next photo

Coal packed in drums

Coal packed and sealed with concrete

Figure 10 & 11 : Coal packed in drums and finally covered with cement and ready for next experiment in a smaller scale.

Day 6

Finally, all sensor cables were removed and from the drill holes where the crack sensors were installed, the team poured white cement mixed with water until it filled up to brim. This was to determine extent or quantity of coal burnt during the experiment. Quantity of cement and water ratio mixed were recorded in the data sheet which also include the quantity of cement wasted.

Discussion and Conclusion

The data collected from this underground coal gasification would be analyzed with suitable software and results made known or published to stakeholders involved and the public once presented on publications.

Underground Coal gasification seems to be the effective way of extracting in-situ coal by way of burning and obtain the various desired products. Of course, there are economic and environmental challenges and consequences involved but needs careful consideration and management from feasibility to development to production to closure and post closure in such a project.

Disclaimer:

Some of the information provided here may not reflect the real intention of the experiment and detail information my not be provided. This article just a reported account of students who attend the experiment on internship purposes to broaden the knowledge and understand the concept of Under Ground coal gasification.

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