Daqing Refinery Reduces Annual Energy Consumption by 41%

Background

As one of the top 10 oil refineries in China, the Daqing Refinery Plant, located in Daqing city, Heilongjiang Province, has a gross-annual revenue of over $10 million.

Established in 1963, the refinery is a part of the Daqing Petrochemical Corporation, a subsidiary of the biggest petroleum production provider in China; PetroChina Group, with a substantial market share of 50%.

In terms of volume, the Daqing Refinery produces 600,000 tons per year in gasoline, diesel oil, kerosene, paraffin, and other petroleum products sold throughout China.

Challenge

Since China entered the World Trade Organization in 2001, the drive to compete with less expensive imported products has propelled the country's industrial sector to meet new challenges in cost-effectiveness and production efficiency. More than ever, reduced cost production is a critical factor in offering a low selling price to keep a healthy market share.

At the Daqing Petrochemical Refinery plant, the crude oil pump from a 3,500-ton pressure reduction process line maintains a steady flow rate of 8,000 to 10,600 tons per day of crude oil. The crude oil pump, however, consumed a large amount of electrical energy in the process.

Finding a more efficient pump control method to reduce wasteful energy consumption was a key value driver at the plant in order to stay competitive and to lower prices.

Other issues facing the Daqing plant were maintenance costs and downtime. The existing pump required regular maintenance every 8,000 hours, which led to 2 days of downtime per year with an average economic loss of $16,438 for each lost day. Such continuous maintenance was largely due to the fact that the pump motor ran at full speed regardless of production output levels.

Previously, engineers at Daqing employed a valve throttle control method to manage the nonstop high speed of the pump motor. With this method, a throttling valve, located at the output of the pump, would be adjusted periodically to meet changing load demands in oil flow rate.

This system, however, proved to be inefficient as problems of high energy consumption, even at low load demand, as well as wear and tear from the high running speed of the pump, persisted. In addition, the throttling control method created increased pipe pressure, which caused oil to leak and the need to frequently replace seals.

Solution

To cut back on excessive electric power consumption, a reliable true Medium Voltage (MV) drive solution was essential for the oil pump motor application at the Daqing Refinery.

Using an Allen-Bradley® PowerFlex® 7000 MV drive with a 6 kV rectifier and a 6 kV inverter that can be easily fabricated with fewer 6.5 kV power devices without output transformer, the Daqing plant had found a simple and reliable solution.

The PowerFlex 7000 uses Current Source Inverter-Pulse Width Modulation (CSI-PWM) technology to provide a simplified power structure with a lower power device count. The PowerFlex 7000 drive makes this efficiency possible with strong overcurrent protection capabilities that do not require fuses and electronic fusing circuits to protect the power devices, thus, simplifying the complexity of the drives.

Results

Depending on the market requirements, the Daqing Refinery production output varies between three levels (9,000 tons per day, 9,600 tons per day, and 10,500 tons per day). With the Rockwell Automation solution place, the plant has gone a long way to maintain such significant production numbers while saving money with more efficient energy consumption.

For a 9,000 ton production output, 426 KW/h were required for oil pump motor operation compared to after the PowerFlex 7000 retrofit power consumption at 250 KW/h. The Daqing Refinery saves 1,533,312 KW/h per year, which reduces their annual energy consumption by 41%.

For a 9,600 ton production output, 527 KW/h were required for oil pump motor operation compared to after the Powerflex 7000 retrofit power consumption at 370 KW/h, the Daqing Refinery saves 1,370,397 Kwh per year, which reduces their annual energy consumption by 30%.

For a 10,500 ton production output, 584.8 KW/h were required for oil pump motor operation compared to after the PowerFlex 7000 retrofit power consumption at 400 KW/h, the Daqing Refinery saves 1,609,977 Kwh per year, which reduces their annual energy consumption by 32%.

In addition, the new solution safeguards the pump motors against over-currents and simplifies the drive systems by eliminating fuses and electronic fusing circuits. $15,000 per year is saved in reduced maintenance costs and decreased downtime.

The total savings at the Daqing Refinery have resulted in a project return on investment ROI) of 2.5 years. The project was so successful at the Daqing Refinery that after one year of operation, a meeting was held at the site to introduce the PowerFlex 7000 retrofit to all sister plants in Daqing Petrochemical.

Hangying Wu, the plant's chief engineer, notes that his faith in the Rockwell Automation solution was right on the money.

“System reliability is the main criteria for us when selecting products,” says Wu, “Allen-Bradley CSIPWM has a wonderful power structure design, which uses module structure, few device components, and strong overcurrent protection capability.”

“After careful technical comparison and analysis, we decided to select the Rockwell Automation solution. The good performance of the drive has proven that our decision was correct.”