Revamps 2022 Issue

2.00 1.00 3.00 4.00 5.00 6.00 8.00 7.00 9.00

ABACO-Air burner regulation

Monitoring

Regulation

ABACO-Control expert system

ABACO-Option

Figure 6 General arrangement of ABACO technology at fired heater

sampling probes (one per burner) for characterisation of the combustion process in each individual burner • ABACO-Air for automated regulation of the air dampers of the burners and the furnace stack, for an optimised flame tuning and control of furnace draft, respectively • ABACO-Control for closed-loop control of the overall combustion process. Combustion characterisation Combustion scenarios were characterised through compre- hensive testing using new monitoring capabilities provided by ABACO-Opticom. The testing was designed to cover the original situation before the application of ABACO and study the limitations of the control capabilities of the fired heater. Table 1 summarises the main results during this characterisation: (I) Original situation: The main results of this combustion diagnosis were: • The original monitoring did not accurately represent the overall excess O₂ in this fired heater. The information given by a global O₂ monitoring approach cannot be used for combustion optimisation. • Identification of important imbalances between individual burners. Measured differences typically were above 4% in excess O₂ in the baseline (see Figure 7 ). These imbalances were limiting effective efficiency optimisation. (II) Implementation: Implementation of the ABACO approach enabled the unit to achieve steady optimised com- bustion scenarios. A clear evolution of the excess O₂ levels given by ABACO-Opticom monitoring system resulted in final oxygen average values below 3% (from initial average values of around 6%). Safer, sustainable, homogeneous, and efficient combustion scenarios were reached. In addition, the results included in Figure 7 show a clear reduction in the dispersion O₂ figures after the implementation of ABACO. The reported minimisation of excess O₂ was coupled with a gas temperature reduction of ~20ºC at the furnace outlet, bringing the overall fuel consumption savings from 5.5% to 7% in all operating scenarios. Average savings of 6.3% and equivalent reduction were obtained for CO₂ and SO X overall emissions. ABACO allows the immediate and unequivocal

Baseline ABACO

40 45 50 55 60 65 70 75 80 0 5 1015 202530 35 Burner 0.00

Figure 7 Excess O₂ profile at the burner area before and after applying ABACO technology

identification of burner malfunctions, an essential tool for a cost-effective burner maintenance programme. This sort of malfunction that results in hazardous operating scenar- ios remains undetected if only conventional monitoring is applied, which is a clear limitation for O₂ reduction policies. Overall results The main results obtained from the application of ABACO technology in this unit were: • Annual fuel consumption savings of 6.3% • Safer combustion. Control of furnace draft, dangerous combustible gases atmospheres, and CO emissions • Achievement of negligible CO levels even for the most stringent low excess air scenarios • Avoidance of 6,800 tons/yr of CO₂ emissions • SO X emission reductions above 6% • Simultaneous reductions in NO x emission of 20-30% • Highest profitability, with a payback period of 14 months • Reduced man labour and maintenance over burner system. Conclusions When facing combustion optimisation challenges, such as efficiency improvement and/or emissions reduction, ABACO technology has proved to be a cost-effective alter- native and a valuable complementary tool to large-scale combustion system retrofits, such as burner retrofitting. ABACO technology, which is qualified as the Best Available Technique for NO X control at the European IPPC Directive, has been applied to more than 30 combustion units, including large utility boilers for electricity genera- tion. Typical NO x reductions achieved in process fired heat - ers and boilers (20-50%) are comparable to those obtained by implementing new low NO X burners (LNBs). Moreover, after the installation of LNBs, ABACO has demonstrated to be a powerful optimisation tool by achieving further NOx reductions ranging from 20-30% and excess O 2 reductions over 1.5%. In addition, improvements in unit efficiency ranging from 2.0-7.0% lead to fuel savings and emissions penalty reductions that typically result in an investment payback of around 1-3 years, depending on the baseline, fuel type and heat recovery section performance, among other factors.

Situation

Average O 2 (existing analysers)

Average

Max O2

NOx

O 2

difference

(ppm)

(burners)

between burners

I Baseline II ABACO

4.0-4.5% 1.7-2.1%

5.8% 2.6%

>4.0% <2.0%

25-50 20-25

Table 1 O₂ and NOx emissions at the original situation (I) and after application of ABACO technology (II)

Revamps 2022