Gold Mining: What gas detection do I need? 

How is gold mined?

Gold is a rare substance equating to 3 parts per billion of the earth’s outer layer, with most of the world’s available gold coming from Australia. Gold, like iron, copper and lead, is a metal. There are two primary forms of gold mining, including open-cut and underground mining. Open mining involves earth-moving equipment to remove waste rock from the ore body above, and then mining is conducted from the remaining substance. This process requires waste and ore to be struck at high volumes to break the waste and ore into sizes suitable for handling and transportation to both waste dumps and ore crushers. The other form of gold mining is the more traditional underground mining method. This is where vertical shafts and spiral tunnels transport workers and equipment into and out of the mine, providing ventilation and hauling the waste rock and ore to the surface.

Gas detection in mining

When relating to gas detection, the process of health and safety within mines has developed considerably over the past century, from morphing from the crude usage of methane wick wall testing, singing canaries and flame safety to modern-day gas detection technologies and processes as we know them. Ensuring the correct type of detection equipment is utilised, whether fixed or portable, before entering these spaces. Proper equipment utilisation will ensure gas levels are accurately monitored, and workers are alerted to dangerous concentrations within the atmosphere at the earliest opportunity.

What are the gas hazards and what are the dangers?

The dangers those working within the mining industry face several potential occupational hazards and diseases, and the possibility of fatal injury. Therefore, understanding the environments and hazards, they may be exposed to is important.

Oxygen (O2)

Oxygen (O2), usually present in the air at 20.9%, is essential to human life. There are three main reasons why oxygen poses a threat to workers within the mining industry. These include oxygen deficiencies or enrichment, as too little oxygen can prevent the human body from functioning leading to the worker losing consciousness. Unless the oxygen level can be restored to an average level, the worker is at risk of potential death. An atmosphere is deficient when the concentration of O2 is less than 19.5%. Consequently, an environment with too much oxygen is equally dangerous as this constitutes a greatly increased risk of fire and explosion. This is considered when the concentration level of O2 is over 23.5%

Carbon Monoxide (CO)

In some cases, high concentrations of Carbon Monoxide (CO) may be present. Environments that this may occur include a house fire, therefore the fire service are at risk of CO poisoning. In this environment there can be as much as 12.5% CO in the air which when the carbon monoxide rises to the ceiling with other combustion products and when the concentration hits 12.5% by volume this will only lead to one thing, called a flashover. This is when the whole lot ignites as a fuel. Apart from items falling on the fire service, this is one of the most extreme dangers they face when working inside a burning building. Due to the characteristics of CO being so hard to identify, I.e., colourless, odourless, tasteless, poisonous gas, it may take time for you to realise that you have CO poisoning. The effects of CO can be dangerous, this is because CO prevents the blood system from effectively carrying oxygen around the body, specifically to vital organs such as the heart and brain. High doses of CO, therefore, can cause death from asphyxiation or lack of oxygen to the brain. According to statistics from the Department of Health, the most common indication of CO poisoning is that of a headache with 90% of patients reporting this as a symptom, with 50% reporting nausea and vomiting, as well as vertigo. With confusion/changes in consciousness, and weakness accounting for 30% and 20% of reports.

Hydrogen sulphide (H2S)

Hydrogen sulphide (H2S) is a colourless, flammable gas with a characteristic odour of rotten eggs. Skin and eye contact may occur. However, the nervous system and cardiovascular system are most affected by hydrogen sulphide, which can lead to a range of symptoms. Single exposures to high concentrations may rapidly cause breathing difficulties and death.

Sulphur dioxide (SO2)

Sulphur dioxide (SO2) can cause several harmful effects on the respiratory systems, in particular the lung. It can also cause skin irritation. Skin contact with (SO2) causes stinging pain, redness of the skin and blisters. Skin contact with compressed gas or liquid can cause frostbite. Eye contact causes watering eyes and, in severe cases, blindness can occur.

Methane (CH4)

Methane (CH4) is a colourless, highly flammable gas with a primary component being that of natural gas. High levels of (CH4) can reduce the amount of oxygen breathed from the air, which can result in mood changes, slurred speech, vision problems, memory loss, nausea, vomiting, facial flushing and headache. In severe cases, there may be changes in breathing and heart rate, balance problems, numbness, and unconsciousness. Although, if exposure is for a longer period, it can result in fatality.

Hydrogen (H2)

Hydrogen Gas is a colourless, odourless, and tasteless gas which is lighter than air. As it is lighter than air this means it float higher than our atmosphere, meaning it is not naturally found, but instead must be created. Hydrogen poses a fire or explosion risk as well as an inhalation risk. High concentrations of this gas can cause an oxygen-deficient environment. Individuals breathing such an atmosphere may experience symptoms which include headaches, ringing in ears, dizziness, drowsiness, unconsciousness, nausea, vomiting and depression of all the senses

Ammonia (NH3)

Ammonia (NH3) is one of the most widely used chemicals globally that is produced both in the human body and in nature. Although it is naturally created (NH3) is corrosive which poses a serve concern for health. High exposure within the air can result in immediate burning to the eyes, nose, throat and respiratory tract. Serve cases can result in blindness.

Other gas risks

Whilst Hydrogen Cyanide (HCN) doesn’t persist within the environment, improper storage, handling and waste management can pose severe risk to human health as well as effects on the environment. Cyanide interferes with human respiration at cellular levels that can cause serve and acute effects, including rapid breathing, tremors, asphyxiation.

Diesel particulate exposure can occur in underground mines as a result of diesel-powered mobile equipment used for drilling and haulage. Although control measures include the use of low sulphur diesel fuel, engine maintenance and ventilation, health implication includes excess risk of lung cancer.

Products that can help to protect yourself

Crowcon provide a range of gas detection including both portable and fixed products all of which are suitable for gas detection within the mining industry.

To find out more visit our industry page here.

Hydrogen Electrolysis

At present the most commercially developed technology available to produce hydrogen is from electrolysis. Electrolysis is an optimistic course of action for carbon-free hydrogen production from renewable and nuclear resources. Water electrolysis is the decomposition of water (H2O) into its basic components, hydrogen (H2) and oxygen (O2), through passing electric current. Water is a complete source for producing hydrogen and the only by-product released during process is oxygen. This process uses electrical energy that can then be stored as a chemical energy in the form of hydrogen.

What is the Process?

To produce Hydrogen, Electrolysis converts electrical energy into chemical energy by storing electrons in stable chemical bonds. Like fuel cells, electrolysers are composed of an anode and a cathode separated by an aqueous electrolyte according to the type of electrolyte material involved and the ionic species it conducts. The electrolyte is an obligatory part as pure water does not have the ability to carry enough charge as it lacks ions. At the anode, water is oxidised into oxygen gas and hydrogen ions. While the cathode, water is reduced to hydrogen gas and hydroxide ions. At present there are three leading electrolysis technologies.

Alkaline Electrolysers (AEL)

This technology has been used on an industrial scale for over 100 years. Alkaline electrolysers operate via transport of hydroxide ions (OH-) through the electrolyte from the cathode to the anode with hydrogen being generated on the cathode side. Operating at 100°–150°C, Electrolysers use a liquid alkaline solution of sodium or potassium hydroxide (KOH) as the electrolyte. In this process the anode and cathode are separated using a diaphragm that prevents remixing. At the cathode, water is split to form H2 and releases hydroxide anions that pass through the diaphragm to recombine at the anode where oxygen is produced. As this is a well-established technology it is relatively low in cost of production as well as it provides a long-time stability. However, it does have a crossover in gases possibly compromising its degree of purity and requires the use of a corrosive liquid electrolyte.

Polymer Electrolyte Membrane Electrolysers (PEM)

Polymer Electrolyte Membrane is the latest technology to be commercially used to produce hydrogen. In a PEM electrolyser, the electrolyte is a solid specialty plastic material. PEM electrolysers operate at 70°–90°C. In this the process the water reacts at the anode to form oxygen and positively charged hydrogen ions (protons). The electrons flow through an external circuit and the hydrogen ions selectively move across the PEM to the cathode. At the cathode, the hydrogen ions combine with electrons from the external circuit to form hydrogen gas. Compared to AEL there are several advantages: the product gas purity is high in a partial load operation, the system design is compact and has a rapid system response. However, component cost is high and durability is low.

Solid Oxide Electrolysers (SOE)

AEL and PEM electrolysers are known as Low-Temperature Electrolysers (LTE). However, Solid oxide Electrolyser (SOE) is known as High-Temperature Electrolyser (HTE). This technology is still at development stage. In SOE, solid ceramic material is used as the electrolyte which conducts negatively charged oxygen ions (O2-) at elevated temperatures, generates hydrogen in a slightly different way. At a temperature about 700°–800°C steam at the cathode combines with electrons from the external circuit to form hydrogen gas and negatively charged oxygen ions. The oxygen ions pass through the solid ceramic membrane and react at the anode to form oxygen gas and generate electrons for the external circuit. Advantages of this technology is that it combines high heat and power efficiency as well as it producing low emissions at a relatively low cost. Although, due to the high heat and power required, start-up time takes longer.

Why is Hydrogen being considered as an alternative fuel?

Hydrogen is considered an alternative fuel under the Energy Policy Act of 1992. Hydrogen produced via electrolysis can contribute zero greenhouse gas emissions, depending on the source of the electricity used. This technology is being pursued to work with renewable (wind, solar, hydro, geothermal) and nuclear energy options to allow virtually zero greenhouse gas and other pollutant emissions. Although, this type of production will require the cost to be decreased significantly to be competitive with more mature carbon-based pathways such as natural gas reforming. There is potential for synergy with renewable energy power generation. Hydrogen fuel and electric power generation could be distributed and sited at wind farms, thereby allowing flexibility to shift production to best match resource availability with system operational needs and market factors.

Sapphire hunters saved!

The Mine Hunters are on the search for sapphires. In this episode they head to South Western Madagascar, to one of the few places in the world where a single mine can produce sapphires of every color of the rainbow.

After a wall collapse, oxygen depletion is the biggest danger they face in these dangerous environments – tunnels which have been sealed off for some time, are long, narrow, and go deep under ground.

Unfortunately miner Fred runs out of Oxygen whilst inspecting the first muddy pit mine. His Tetra 3 gas detector goes in to alarm, allowing his friends to pull him out quickly and safely. Although the team here is on a budget, the one piece of kit they can not go without is clear – a life saving gas detector!

View the video here

Read more about the Mine Hunters series and watch other episodes.

Find out more about the Tetra 3 Gas Detector and other interesting applications such as Volcano research

Oxygen factoids – what you need to know

As part of our commitment to sharing our knowledge and expertise of gas detection safety around the world, we have created a series of short and to-the-point “factoid” videos, covering a variety of gas-related hazards. As with all our videos, they are intended to be watched, downloaded and/or shared however helps you. Please use them to spread the word and improve gas detection safety.

This first video focuses on risks associated with either too little or too much oxygen (O2).

Continue reading “Oxygen factoids – what you need to know”