Standards Development

Scope

This Document specifies a method for the determination of the gross calorific value of sludge at constant volume and at the reference temperature 25 °C in a bomb calorimeter calibrated by combustion of certified benzoic acid.

The result obtained is the gross calorific value of the sample at constant volume with both the water of the combustion products and the moisture of the sludge as liquid water. In practice, sludge are burned at constant (atmospheric) pressure and the water is not condensed but is removed as vapour with the flue gases. Under these conditions, the operative heat of combustion to be used is the net calorific value of the fuel at constant pressure. In this European Standard the net calorific value at constant volume is described as it requires less additional determinations.

This method is applicable to all kinds of sludge.

Purpose

This document is a draft proposition based on EN 15170:2008, published by Technical Committee CEN/TC 308 “Characterization of sludge”, the secretariat of which is held by AFNOR.

This method is a simple way to evaluate the amenability of sludge and sludge products to be treated by thermal processes. In this document, some thermo-chemical corrections are not considered. For detailed descriptions of analytical procedures and theoretical background see ISO 1928.

The result obtained is the gross calorific value of the sample at constant volume with both the water of the combustion products and the moisture of the sludge as liquid water. The net calorific value can be derived from the gross calorific value. For this either the hydrogen content of the sludge or the amount of water found in the combustion test hall be determined.

Sludge usually contain much water and (un-burnable) solids. Therefore, their calorific value – especially on the “as received” basis – is quite low. For many purposes it may be nough to determine the gross calorific value only, and not the net calorific value for which additional determinations are necessary. The calculation of the net calorific value at constant volume only is described here, for calculation at constant pressure refer to either ISO 1928.