Flow measurement of blast furnace gas in the steelworks

Long-term measurement of blast furnace gas, coke oven gas and converter gas in the production process during iron production

Process data

Measuring task:
Volume flow measurement of coke oven gas, blast furnace gas, converter gas

Measuring point:
Coke oven / blast furnace / converter gas line

Measuring range:
up to 10 m/s

Process pressure:

Process environment:
appr. +25°C

Recommended products

Vortex flow probe VA40 ZG8 Ex-d

ProductProduct data sheet


When producing pig iron from iron ore in a blast furnace, temperatures above 1500 °C must be generated. In addition, oxygen in the form of preheated air must be constantly supplied to the blast furnace in order to maintain the combustion process.

The air blown into the blast furnace escapes at the top of the furnace (the blast furnace top) as blast furnace gas. This gas consists mainly of nitrogen, carbon dioxide and the very toxic carbon monoxide, plus a small amount of hydrogen. It contains a lot of dust. The dust in the blast furnace gas must be removed in order to utilise the gas.

Blast furnace gas is mainly used to heat various furnaces and to generate residual pressure electricity. It is added to the furnace supply air and thus recycled. Since it is also combustible (hydrogen content), it serves as an energy source for the combustion process.

Blast furnace gas plays a very important role in the metallurgical industry and is a key element in saving energy and reducing consumption. Only when the blast furnace gas flow rate is accurately determined can the blast furnace gas be used wisely and effectively. Blast furnace gas, converter gas and coke oven gas have different compositions and contain dust and condensate. Measuring them is a major challenge for the flow sensors.

Your advantage

The meter is suitable for rugged outdoor use

Variable composition, dust and condensate
Measurement independent of pressure, temperature, kinematic viscosity and composition of the sample gas. Small amounts of dust and condensate have no influence on the measurement

Höntzsch also offers solutions for long-term measurement in Ex design

Blast furnace process

A blast furnace is used to produce pig iron. Iron ore and additives such as lime are fed into the furnace for this purpose. In an upstream process, in the coking plant, coke with a high carbon content is produced from coal. Among other things, coke oven gas is also produced. On the one hand, the coke serves as a source of energy. On the other hand, carbon monoxide is released when the coke is burnt. This in turn serves as a reducing agent for the process. It is used to generate the heat in the blast furnace to enable the reduction of iron ore to pig iron. Temperatures far above 1500 °C are generated in the process. This reduction also produces blast furnace gas, which is collected at the top of the blast furnace.

Blast furnace gas (blast furnace gas), coke oven gas and converter gas

The blast furnace gas collected at the blast furnace consists of nitrogen, carbon dioxide, carbon monoxide and a small amount of hydrogen. It is also heavily contaminated with dust. Therefore, in the first step it has to be cleaned by a scrubber (for more details see volume flow measurement at gas scrubbers). It is then used to drive the compressors with which the "wind" is blown into the blast furnace. This serves as an oxygen supplier and provides a considerable energy contribution. It can also be used to generate electricity. This is done in steam turbines.


Measurement of blast furnace gas

Due to its varying composition and dust content, it is difficult to measure blast furnace gas continuously over a long period of time. The sensors must measure independently of the gas composition and density and must also be insensitive to exposure to the dust.

The Vortex sensor from Höntzsch has proven its suitability in many applications at different measuring points. And this with permanent operation of the blast furnace around the clock for many years. The vortex sensors can be used up to Ex-Zone 0 / 1. With the Höntzsch vortex sensors, the flow velocity and the volumetric flow of air and gases can be precisely measured from as little as 0.5 m/s. The volumetric flow measurement is largely independent of the blast furnace. The volume flow measurement is largely independent of pressure, temperature, kinematic viscosity and composition of the sample gas. The probe depth can be adjusted according to customer requirements. The accurate measurement of the blast furnace gas flow contributes to the reuse of blast furnace gas in steelworks, to energy saving and to environmental protection.