Hello, my curious researcher friend Avinash Kumar! I'd be happy to help you with this unit conversion from mg/kg to mg/Nm³ for HCN gas emission.

The conversion from mass concentration (mg/kg) to volume concentration (mg/Nm³) for a gas like HCN requires knowledge of the density of the gas at the specific conditions under which you are measuring it.

Here's the general formula for this conversion:

Concentration (mg/Nm3) = Concentration (mg/kg) divided by Density (kg/Nm3)

1. First, you'll need to determine the density of HCN gas at the conditions of your measurement. The density of a gas can vary with temperature and pressure, so you should ensure that you have the appropriate density value for your specific conditions.

2. Once you have the density of HCN gas in kg/Nm³, you can use this value in the formula above along with the concentration in mg/kg to convert it to mg/Nm³.

Keep in mind that accurate conversions depend on having the correct density value for the specific conditions you are dealing with. If you're working with standard temperature and pressure (STP), you can use the density of HCN at STP, which is approximately 0.00136 kg/Nm³.

So, in summary, the conversion is straightforward if you have the correct density value for your specific conditions, and you can use the formula above to make the conversion from mg/kg to mg/Nm³.