Energy conservation by installation of Advanced Process Control (APC) Technology

Advanced Process Control (APC) is an IT system (software) incorporating statistical analysis,
decision theory, engineering, signal processing and artificial intelligence. APC analyzes
individual process data obtained through Distributed Control System (DCS), and provides
instructions which optimize the overall production process, resulting in less energy to meet aproduction target.

1. Application of APC in hydrocracking units (HCU)

A. Reduction in heater fuelIn hydrocracking units (HCU), hydrogen is reacted with feed (heavy gas oil) to producevarious petrochemical products. Amount of hydrogen required to mee t the demand fluctuates
due to factors such as chemical composition of feed and component. Since it is not possible
to maintain the hydrogen supply exactly at the required values due to such fluctuation,hydrogen is fed at excessive levels to minimize the risk of not meeting the required level ,resulting in increased fuel consumption at the heater. APC reduces the fluctuation byinferring feed component, which results in reduction of total hydrogen demand. Reduction ofhydrogen demand results in increased temperature of the reactor column, which can be used
to preheat the feed, thereby reducing the fuel consumption at the heater.

Figure 1. Schematic diagram of reactor in HCU.
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B. Reduction of debutanizer reboiler fuelIn debutanizer in hydrocracking units (HCU), the temperature and pressure of debutanizer
column must be maintained at or above a certain level. Since it is not possible to maintain thetemperature and pressure exactly at the required values due to fluctuation in feed component,
fuel is fed at excessive levels to the reboiler in order to minimize the risk of column top
pressure dropping below the required values. Introduction of APC reduces the fluctuation ofcolumn top pressure and lowers the pressure by inferring (*)feed component, which reduces
the need to consume excessive fuel to the reboiler. (*:Estimate calculation by the relatingprocess data available on DCS)

Figure 2. Schematic diagram of HCU debutanizer in HCU.

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C. Emission reduction in HPU due to reduction in hydrogen demand in HCU
When APC is introduced in HCU, hydrogen demand is decreased, leading to energy
conservation in HCU, as shown above. In addition, such reduction of hydrogen demand
results in reduced hydrogen production in the hydrogen production unit (HPU) wherehydrogen is produced by reforming methane with steam under high temperature. Therefore,
application of APC in HCU results in reduction of energy consumption in HPU.

Figure 3. Schematic diagram of reformer in HPU.

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2. Application of APC in hydrogen production units (HPU)
D. Efficiency improvement in hydrogen production
APC can help energy consumption in hydrogen production units (HPU) in the following twoways:
APC installed in HCU results in lower hydrogen demand.

APC installed in HPU results in lower energy demand per hydrogen produced.

The former is explained in the preceding paragraph. The latter is realized by inferring CH 4
slip (*) and calculation of its trend, which improves fuel efficiency of the heater in HPU.
(*: CH4 slip is a phenomenon of unreacted CH 4 is carried out to the produced hydrogen.)

Figure 4. Schematic diagram of reformer in HPU and CH 4 slip.

43. Ensuring net emission reduction
The methodology assures net reduction by not taking into account for reduction inconsumption of electricity and steam from outside the process (on -site generators andboilers) which occurs as a result of process optimization due to implementation of the project.
Furthermore, CO 2 emission from chemical reaction in HPU is also reduced due to reduction
in hydrogen demand in HCU, but this is not taken into account, leading to additional
conservativeness.

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