PTQ Q3 2024 Issue

Carbon cost driving refineries to rethink fired heater specifications

Carbon market scenario can change conventional fired heater economics and usher in a new benchmark in design and operation of air preheaters and fired heaters

Shilpa Singh and Rupam Mukherjee Engineers India Limited

W ith the Paris initiative claiming the spotlight over last few years and India’s commitment to net zero, it has become imperative for the energy-consum- ing sectors to fine-tune their operations to the highest level of efficiency, be it on an equipment level or an overall plant level. With major governments all over the globe adopting legislature in favour of a lower carbon footprint, it is high time that carbon-intensive equipment undergoes a major fresh look into how it is designed and operated. Carbon cost scenarios Conventionally, heat recovery equipment or efficiency improvement initiatives were gauged solely based on payback generated by additional savings from fuel. Unfortunately, there are numerous instances where many good proposals had to be rejected on these criteria. However, the gains post-implementation of these propos- als might have benefited the end-user in the long term. The majority of EU countries have already adopted the EU Emissions Trading Scheme (ETS), whereby the cost of each tonne of carbon emitted is accounted as a penalty, and like- wise, each tonne of carbon dioxide (CO₂) saved is counted as credit. In such a scenario, energy efficiency gains are a priority and can turn the tables in favour of cleaner energy tech- niques, albeit at higher capital investment. With carbon mar - ket scenarios emerging fast in many countries and expected to gain pace over the next few years, carbon credit or carbon cost, when factored in into conventional calculations, reveals very promising results in favour of cleaner technology alter- natives. A suo motu study was conducted to establish this fact, and the same is presented in this article. The studies presented herein may inspire a fresh look into shelved efficiency improvement proposals because carbon footprint has slowly but steadily started gaining importance, even in the case of Environmental Impact Assessment clearances. All three Rs – ‘Reduce, Recover, and Reuse’ – are also applicable in the case of fired heaters, but they come at a price. Nonetheless, they are invariably necessary for the greater good of the environment. This article aims to provide valuable information on how the upcoming carbon market scenario can change conven- tional fired heater economics and usher in a new benchmark

in the design and operation of fired heaters. In the first case study, a scenario demonstrates how accounting carbon cost can alter the economics for selecting air preheat sys- tems, as opposed to the conventional approach of selection solely based on fuel saving. In the second case study, the impact of carbon cost is illustrated while shifting from fuel oil to fuel gas firing. For the third case study, the promising aspect of blending green hydrogen in the fuel gas network was analysed on the backdrop of carbon cost. Finally, in the fourth case study, a comparative analysis was performed to ascertain whether accounting for carbon cost can alter the economics for elec- trically powered furnaces vis-à-vis fuel gas-fired furnaces. Current design and operational practices Efficiency has long been considered in terms of its eco - nomic viability. General finance terms such as simple pay - back, internal rate of return (IRR), and net present value (NPV) come into the picture while evaluating any additional investment. The same is the case with air preheaters (APHs) in fired heater systems, where furnace designers usually have an established set of guidelines defining whether an APH system is economically feasible. In general, APHs are adopted based on furnace duty (see Table 1 ). Exact eco- nomic criteria may vary from country to country and will be based on prevalent fuel and equipment prices. A general trend is that a full-fledged outboard APH system becomes economically feasible only when the absorbed heat duty of the heater is more than 20 Gcal/h. The contrary side of this outcome is that for heaters with

General APH selection criteria

Duty range

Air preheater

Remarks

(furnace)

system provision

Small

Typically less than 10 Gcal/h Typically with 10 to

Medium

Depending on heat

recovery potential on 20 Gcal/h case-to-case basis

Large

Yes

Typically more than 20 Gcal/h

Table 1

PTQ Q3 2024