In depth: Clean Industrial Heat

In the public and political debate, industrial heat is a typically underestimated part of the total use of energy worldwide. In industrialised countries, industrial heat is responsible for about a quarter of the total energy use, a percentage that differs with the level of industrialisation and the amounts of industrial goods imported or exported. ‘Heat’ is required for a large number of industrial processes. It can be produced and transferred in many ways, and transmitted by a hot heat carrier through heat exchangers or by electrical resistance.

According to a survey, carried out in 2010 by Bredimas and others, The European heat market is large, ranging from 2 529 to 3 091 TWh/y, as compared to the 3 337 TWh/y of electricity production in Europe in 2007; this corresponds to an equivalent 289 to 353 GWth, as compared to an equivalent 381 GWe for electricity production. The heat market can be divided in several temperature ranges. The most significant market volumes can be found at process temperatures below 550°C and above 1 000°C.

The energy source of industrial heat is presently mostly natural gas and, to a lesser extent, coal and oil. Electricity plays a minor role in the production of industrial heat, and hence the application area is hardly serviced by renewable energy sources.

Molten salt reactors are an excellent candidate to deliver clean and carbon free heat, that can be efficiently used for a wide range of industrial applications. MSR’s heat can be transported and delivered in several ways. MSR’s can produce heat of up to 550°C, which appears to be a very relevant temperature range for industrial applications. This is mainly due to the fact that superheated steam is generally used for heat transport in industry, directly generated by fossil fuel burning. 500-550°C is currently the maximum steam temperature range adopted, mainly due to severe component and piping corrosion issues at higher steam temperatures. Using other media media like CO2 or nitrogen for heat transport may allow for higher temperatures and further process optimization.

Using MSR-produced heat does not necessarily imply that process industries install MSR’s in their own plant. This is quite relevant, as installing MSR’s would imply that compliance to nuclear regulations would become mandatory. Several workarounds have been proposed to avoid this. Bredimas envisions the establishment of ‘industrial ecosystems’, consisting of several heat-using industries, built around molten salt reactors, that may or may not produce electricity simultaneously. This heat is transported by a carrier that is outside what is called the ‘nuclear barrier’, meaning that that the receiving party also remains outside the nuclear legislature. Heat transportation can be done with minimized loss, and over quite far distances.

According to Bredimas, the largest part of the heat market is for process temperatures below 550°C (60% to 66% of the heat market) – and these are evidently potential areas for the heat of molten salt reactors. However, even industrial processes with temperatures of 1 000°C or more (28% to 36% of the heat market) may profit from using MSR’s in the form of pre-heating, after which the remaining temperature rise is delivered by other sources, possibly, but not necessarily, the electricity produced by the MSR. This however, will in most cases require redesign of existing processes.

Other options will be much easier to realize: Bredimas calls calls these ‘plug-in’ applications. In these areas, molten salt reactors could in essence replace present technologies, usually gas turbines, that function within an existing infrastructure. An important market area here is co-generation, in which surplus heat is used for other processes. The most well-known example is the production of electricity, of which the heat generated can be used for other applications like district heating. Using existing infrastructures implies large savings on the cost per kWh.

This plug-in market represents about 30% of the total heat market, totalling up to 87 to 89 GWth.

Bredimas points out the following possible application areas. The applications on the left utilize moderate temperatures and are within the reach of MSR heat. The ones on the right require (very) high temperatures – MSR heat would only become relevant if the temperature is boosted by MSR generated electricity.