Cold reactor
Hot reactor
210˚C
Out industrial heat Input wasted heat
Dimer + water
Phosphoric acid loop
Waste heat
Process heat
endothermic
exothermic
120˚C
Monomer
120˚C
80˚C
Figure 1 Process sketch of the QHT
boiler, fed with grid natural gas and without free allowance on the CO₂ emission. Assuming 90% energy conversion in the burner, 0.2 tons CO₂ emission per MWh natural gas and boiler feed water available at 100°C, then one ton of steam represents a value of approximately €50. This value assumes a natural gas cost of €50/MWh and €100/ton CO₂ EU ETS and is neglecting header losses or the cost of boiler feed water. Translated to an average European refiner with 20% of emissions linked to steam generation and 30 kg emissions per barrel of refined product, the potential goes up to €2/ barrel increase in margin. This represents significant lever - age against other margin pressure factors. Turning cooling load into CO₂-neutral, Opex-free steam The ATP-ADP cycle is an energy distribution system that fuels all living cells on Earth. Adenosine triphosphate (ATP) and its derivative adenosine diphosphate (ADP) are used as an energy carrier to transport energy on a cellular scale. ADP, the base molecule, gets charged with an extra phosphate group and turns into ATP in areas with excess energy. In contrast, the reverse reaction releases energy in energy-poor areas. The liquid ATP and ADP are easily transported throughout the cellular fluids. The Qpinch Heat Transformer (QHT) is an absorption heat pump which uses phosphoric acid (PA) as working medium. Under right conditions, PA forms oligomers and thus absorbs residual energy available in industrial waste heat. The reversible reaction is used to release the absorbed energy at a higher temperature so it can be reused as pro - cess heat. Useful examples of industrial waste heat are hot liquids, condensing column overheads, and excess steam that currently are condensed/cooled using air fans and cool - ing water exchangers. Examples of useful process heat are steam, thermal oil, and hot water. A QHT unit consists of two heat exchangers with a closed loop of PA between them (see Figure 1 ). The cold reactor absorbs industrial waste heat at low temperature, whereas the hot reactor releases new process heat at high temperature. However, in both reactors, heat is transferred indirectly towards the service side, so the internal PA never encounters the waste heat source or process heat sink, respectively. Furthermore, the PA is food-grade. The
system being a closed loop and PA an inorganic chemical, there is no degradation, consumption, or emission of chem - icals. The PA has no other hazardous effect than its acid- linked corrosivity. So the QHT unit does not represent any flammability, toxicity, or explosion risk and, thus, does not need any flare connection. Figure 2 illustrates the operational range and tempera - ture lift a QHT can generate. As a rule of thumb, waste heat at 80°C can be converted to useful heat at 120°C, while waste heat at 120°C can be lifted to a maximum of 210°C. The QHT converts about half the waste heat duty into new process heat, while the other half is released at ambient temperature as the driving force for the chemical reaction, hence preventing the need for electricity. On a commercial scale, this split does not jeopardise the attrac - tivity because, without Qpinch, the complete waste heat duty would be released to ambient temperature, creating even additional costs to cool down the waste heat. Maybe the most attractive characteristic of a PA-based heat trans - former is the fact that all products remain in the liquid state, so only a marginal amount of electricity (centrifugal pumps) is required to operate the QHT in a safe and reliable way. Indeed, it takes ±300 kW of electricity to generate 10 MW of new process heat, while conventional heat pump technology would require at least eight times more elec - tricity. Moreover, the electricity-to-heat ratio of a QHT is not affected by the temperature lift between the low-tem - perature waste heat source and the high-temperature sink. As such, this augmented economical coefficient of performance (eCOP: ratio of electricity input per unit of high-temperature output) is a unique driver for the financial attractivity of the QHT technology. It is assumed that in the near future in Europe, the marginal cost of electricity will be driven by both renewable supplies (wind, PV) and gas turbines. The latter is a flexibility measure towards fluctuating electricity demand, a parameter more difficult to meet with, for example, nuclear energy. Assuming so, the price of electricity will still be affected by natural gas and CO₂ pricing. For truly net zero Scope 1 and Scope 2 emis - sions, it is key to minimise dependency on commodities with Figure 2 Single step temperature lifts achievable with the QHT
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PTQ Q3 2023
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