Boosting light ends compressor performance with DPPI
The light ends compressor is a bottleneck for the ethylene recovery unit (ERU).
The light ends compressor sends DCC light ends to the ethylene recovery unit to separate ethylene from less valuable byproducts. The DCC unit cracks heavier hydrocarbon cuts from the crude distillation unit with a deep conversion configuration where olefin production is maximized. By increasing DCC throughput, the crude oil processed by a refinery or petrochemical complex can be further valorized as olefins. When the DCC unit runs at maximum capacity, the margin gain is higher and the carbon footprint is lower with petrochemical production preferred over fuel.
A Smart Operation Flow Diagram (SOFD) digital twin was created for the client. Connected to daily average operating data, the diagram included design data and pertinent tools from our DPPI Digital Tool Box (DTB) including:
- Rotating equipment performance evaluation
- Mass balance and margin
- CO2 emissions, Scope 1, Scope 2 and Scope 3
After analyzing historical and current operating data of the unit and the compressor, our technical experts found that the compressor was not working at the expected capacity or power.
Our technical experts proposed two initiatives to maximize compressor capacity upon various analysis and comparisons involving vendors specifications and design data:
- Option 1 – No CAPEX
Increase the compressor trip set point to corrected maximum consumed power (based on 110A and 6200 V) and boost capacity by 7.5 percent.
The light ends compressor capacity is kept low to avoid its motor trip at 1000 kW of consumed power with a voltage of 6000 V. However, according to compressor motor nameplate specifications, the maximum allowable amperage is 110 A and the actual network voltage is 6200 V, allowing a consumed power of 1075 kW.
- Option 2 – Low CAPEX
Regain the original performance of the compressor with a refurbishment in the next turnaround that would increase capacity by 11 percent and decrease power consumption.
The light ends compressor performance is degraded to a lower polytropic efficiency than the vendor design curve.
The potential margin gain is:
- 2.4 M$/year for Option 1
- 3.5 M$/year for Option 2
The two options also help decrease CO2 emissions with some produced olefins not burned but transformed into petrochemicals. The potential Scope 3 emissions reduction is:
- 32 ktCO2/year for Option 1
- 47 ktCO2/year for Option 2
Our Digital Plant Performance Improvement (DPPI) tool is used to assess its current operation and propose initiatives to increase capacity to maximize deep catalytic cracking (DCC) unit throughput.
By maximizing compressor capacity, olefins production throughput can be increased up to 11 percent.