What Is Equilibrated Moisture in coal ?
Equilibrium moisture in coal refers to the moisture content that coal attains when it is stored in a specific environment and reaches a state of moisture balance with that environment. This state of moisture balance is achieved when the coal has been exposed to the same temperature and humidity conditions for an extended period of time, allowing the coal to absorb or release moisture until it reaches a steady-state moisture content. Equilibrium moisture content varies depending on the specific conditions of the storage environment, such as temperature, humidity, and air circulation. It is an important parameter to consider when assessing the quality and handling characteristics of coal, as it can affect the heating value, combustion efficiency, and storage stability of the coal. High equilibrium moisture content can lead to increased transportation and handling costs, as well as potential issues with coal storage and combustion.
How equilibrated moisture concept comes in exist?
The concept of equilibrium moisture in coal arises from the physical properties of coal and the surrounding environment. Coal is a naturally hygroscopic material, meaning it can readily absorb and release moisture from the surrounding air. The amount of moisture absorbed by coal depends on the relative humidity and temperature of the surrounding environment, as well as the specific properties of the coal itself.
When coal is stored in a specific environment for an extended period of time, it reaches a state of moisture balance or equilibrium with the surrounding environment. This equilibrium moisture content is the moisture content that the coal will maintain under those specific environmental conditions. The concept of equilibrium moisture in coal is important because it helps to predict the behavior of coal in various applications, such as transportation, storage, and combustion. It also provides a standard reference point for measuring the moisture content of coal, which is important for quality control and determining the economic value of coal.
Procedure for determination of equilibrated moisture in coal
- Take 4 gm. of laboratory sample of coal (212-micron powder coal) in a conical flask.
- Pour about 15 ml of water on the sample and heat it to 80 Deg C on a water bath for 30 minutes.
- Decant the mixture through a filter paper.
- Press the sample with filter paper to remove as much as possible of the free water.
- Mix it thoroughly and spread evenly about 1.5 to 2.0 gm. in each of the two accurately weighed moisture dishes.
- Place the dishes with lids open into the humidity conditioner where the temperature and the humidity are 40 °c and 60 % relative humidity respectively.
- After 72 hrs. Take the sample out and take one gm. of the sample in a pre-weighed Petri dish.
- Put the sample in oven at 108± 2 °C for one half hour.
- Take the final weight.
5.0 Calculation:
Equilibrated Moisture (in %) = (W2 –W3) / (W2-W1) X 100
Where,
W1: Empty weight of the crucible in gm.
W2: Crucible + sample weight in gm.
W3: Final weight of the crucible in gm.
The results for coal samples are converted in to equilibrated basis and reported.