PTQ Q3 2023 Issue

ole ns from heavy gasoil, atmospheric residues, and other high-boiling point feedstocks. The FCC unit also produces a vast amount of steam to drive other plant operations. However, several coolers inside the FCC are disposing of low-grade heat at a fairly high temperature (>80°C). Examples are the main fractionator overhead condenser, the light cycle oil (LCO) cooler, the heavy cycle oil (HCO) cooler, and the slurry cooler. Qpinch has already investigated several applications of its QHT technology to turn these waste heat sources into Opex-free and CO₂-neutral low- and medium-pressure steam. Figure 5 shows a battery limit heat and mass bal - ance of a QHT engineered for a European refinery where the condensation heat of the main fractionator overhead is lifted into 4.2 tons/hour of medium-pressure steam at 11 bar gauge. Note that only 85 kW of electrical power is required to drive the process unit. Diesel hydrotreater Hydrotreating can be performed on various streams with the aim of reducing the sulphur content: naphtha, die - sel, and kerosene. The process is based on the use of a metal hydrogenation catalyst and occurs at elevated temperatures and pressures. Feed heaters are used to bring the feedstock to the correct operating tempera - ture. Downstream of the reactor, a feed product heat exchanger is used to cool the product and preheat the feed. Nevertheless, conventional air fan cooling is still required to bring the temperature down to separator temperature. In the stripper section, light fractions are separated from the desulphurised product. The overhead of this stripper and the diesel product are in the business-as-usual case, respectively condensed and cooled against air as well. The Qpinch chemical heat transformer can recover the energy in those streams and create useful low-pressure steam. One centralised QHT unit can cool down the three different

Electricity 85kW

Excess LPS 5.0 t/h at 3 bar G

Steam at 11 bar G 4.2 t/h 2.7 MW

FCC main fractionator overhead 124 t/h at 130˚C

LP condensate 0.8 t/h

Q HT

3.1 MW

50˚C

Existing fan cooler

3.4 MW to cooling

are not limited to the chemical industry. In refining, CO₂ emissions related to steam generation can be saved by val - orising low-temperature heat sources in the vacuum unit, hydrocracker, FCC, hydrotreaters, and coker unit. This not only assures direct savings in energy costs but also indi - rect savings in cooling capacity and utility-related mainte - nance costs. Based on heat integration studies performed by Qpinch for European operators, a ballpark total available roll-out potential of 100 t/h CO₂-neutral quasi-Opex-free steam production was identified per 100,000 bbl/d refining capacity. This represents an absolute and annually recur - rent CO₂ saving of 120,000 t/y for a rather small-scale European refinery. A detailed discussion of three different refinery units is provided in the following sections (FCC unit, diesel hydrotreater, and delayed coker unit). FCC unit The FCC is a very versatile unit in a re nery complex. It offers the possibility to produce high-quality fuels and Figure 5 Example of a QHT (white box) designed for a European refiner’s FCC unit combining absorbing the condensation heat from the main fractionator overhead and the excess LPS and lifting this heat into MPS (LPS = low-pressure steam)

5.7 MW

3.9 MW

35˚C

50˚C

Stripper overhead 20 t/h at 169˚C

Coker main fractionator overhead 82 t/h at 117˚C

Existing fan cooler

Electricity 100 kW

Existing fan cooler

Electricity 120 kW

LPS 5.1 t/h

LPS 5.5 t/h

1.0 MW

1.6 MW

50˚C

Heavy coker gasoil 45 t/h at 137˚C

Reactor euent 240 t/h at 103˚C

3.0 MW

3.5 MW

Existing fan cooler

QHT

0.4 MW

Q HT

BFW 5.1 t/h

2.7 MW

BFW 5.5 t/h

40˚C

50˚C

Light coker gasoil 12 t/h at 160˚C

Diesel to storage 210 t/h at 116˚C

4.0 MW to cooling

4.7 MW to cooling

Existing fan cooler

Figure 6 Example of a centralised QHT (white box) designed for a European refiner’s diesel hydrotreater unit combining residual heat from the stripper overhead, reactor effluent, and desulphurised product coolers (BFW = boiler feed water, LPS = low-pressure steam)

Figure 7 Example of a centralised QHT (white box) designed for a European refiner’s DCU combining residual heat from the main fractionator overhead and the light and heavy gasoil coolers (BFW = boiler feed water, LPS = low-pressure steam)

PTQ Q3 2023