Accurate Flow and Density Measurement in Petroleum-Fired Generation

Reconciliation achieved between fuel consumed and power generated

Plant Name:   Electric Power Generator
Industry:         Power
Product(s):     ROTAMASS TI Coriolis flowmeter

Application

The most common fuels used to generate electric power for businesses and consumers varies by world region. In regions such as the Middle East, where petroleum is less expensive, there are more oil-fired power plants. However, in other parts of the world where petroleum is high-priced, there are emissions restrictions, or efficiencies are lower, use fuels such as natural gas, coal, or nuclear to drive the turbine. 

Quite often, conditions require less preferred methods to meet high demand. An example would be where petroleum-fired generation is brought online in cold winters due to the high demand for the region’s natural gas supply or when natural gas prices rise. These conditions require petroleum generators to meet load requirements that allow businesses to continue to operate and consumers not be left in the dark. Regardless of the reason, petroleum-fired generation is here to stay for a while.

In this application, the customer’s facility was using petroleum-fired generation and required a reliable and accurate flow measurement technology to measure the fuel flow required to run the turbines. The fuel flow to the turbine was to be measured and compared to the power generated by the turbine in megawatts, which would be the direct indication of the power generation efficiency, known as the plant settlement system application.

Challenges

Two types of fuels were used to run the turbines, crude oil with a density of 900 kg/m3 and a distillate with a density of 850 kg/m3. The two types of fuels flow through the same meter at different times. The user wanted to know the totalized flow for each of the fuel types for any given period. 

Since the existing flowmeters were providing inconsistent and inaccurate readings, the customer was not able to achieve precise reconciliation of the fuel consumed and power generated. Also, high vibration in the pipe resulted in increased noise in the flow measurement. 

Solution

Yokogawa’s ROTAMASS TI (Total Insight) Coriolis flowmeter can measure mass, temperature, and density. By using the density measurement, the meter could identify whether the fuel being fed into the turbine was crude oil or distillate. The density settings were entered into the ROTAMASS TI and the density threshold criteria were set via the status-out, to trigger the respective totalizer for crude and distillate. If not for this function, two flowmeters would have been needed, one for each of the fuel types.

Regarding the vibration noise from the pipeline, the “box-in-box” design of the ROTAMASS TI isolates the flow tubes from the process connection. By absorbing the mechanical noise or any external forces from misalignment from the pipeline, it delivers an excellent zero stability and final flat accuracy. The ROTAMASS TI performance made it possible for the customer to make process improvements, which resulted in higher efficiency between the fuel consumed and the power generated. It was a major improvement over the prior metering system. 

Key Advantages

 
•    A single device with mass, temperature and density measurements simplifies maintenance and reduces costs.
•    “Box-in-box” design eliminates pipe vibration effects.
•    Multi-phase measurement and totalization ensure accurate readings with the precision necessary for reconciliation.