What kind of flowmeter is used for coke oven gas measurement? The instability of the medium in the coke oven gas causes measurement problems for the flowmeter. Please keep reading.
Before this, coke oven gas can be measured with a V cone flowmeter. Today, we compare the characteristics and economic analysis of gas ultrasonic flow meters, thermal flow meters, and target flow meters. Let’s take a look at the application of these flow meters in coke oven gas measurement.
Sino-Inst offers a variety of Ultrasonic gas flow meters for flow measurement. If you have any questions, please contact our sales engineers.
What is coke oven gas?
Coke oven gas is an important product and consumable of metallurgical enterprises. Coke oven gas has high calorific value and is widely used in the heating process of steelmaking, steel rolling, power generation and other production. Its consumption directly reflects the assessment of energy consumption of each unit The completion of indicators.
Therefore, coke oven gas flow measurement has always been the focus of energy measurement.
However, coke oven gas itself has a low flow rate, a low density, and contains impurities such as tar, water, industrial naphthalene, ammonia, and sulfides. Therefore, the flow measurement of coke oven gas is a difficulty in energy measurement.
Featured Flow Meters for Coke Oven Gas Measurement
Coke oven gas measurement challenges
- The dirt of coke oven gas is blocked.
- The instability of the working conditions of the coke oven gas fluid itself.
- Coke oven gas is highly corrosive, causing serious damage to valves and lax closure. Small and low flow gas flows unimpeded in the pipeline, affecting the data balance of the entire system.
- Once the coke oven is in production, it is difficult to stop production, resulting in inconvenient installation and disassembly.
Case: Analysis of Lu’an Group Coke Oven Gas Metering Point
The coke oven metering points are mainly concentrated on the outlet of the fan, the return gas pipeline, the inlet and outlet of the gas tank, and the external gas supply pipeline.
The above-mentioned pipelines have been used for a long time, and there is dust accumulation in the pipelines, especially the dust accumulation in the outlet of the fan and the return furnace pipeline.
Moreover, the flow rate at the above-mentioned metering point is relatively low, and the pressure is relatively low. The gas contains tar and naphthalene. The composition changes due to different coal blending ratios, and also changes with the condensation of water vapor in the pipeline.
Therefore, the requirements for measuring instruments at the measuring point are as follows;
- Measuring instruments are required to be not affected by gas composition (density)
- The measuring instrument can adapt to the measuring characteristics of low flow rate and low pressure of coke oven gas
- Dirt resistant, and the measurement is not affected by tar and naphthalene in the gas
- In the measurement process, the measurement instrument can remove the influence of pipe dust on the measurement
- It can be constructed online and installed without stopping the air.
Comparison of characteristics of ultrasonic flowmeter, smart target flowmeter and thermal flowmeter
|Installation concentricity requirements||general||high||high|
|Pipeline fouling effect||general||Big||Big|
|Highest measurement accuracy||±0.15%||±0.2%||±0.5%|
|Repeatability||it is good||general||general|
|Temperature and pressure compensation||Have||Have||Have|
|Requirements for front and rear straight pipes||10D before, 5D after||10D before 5D||5D before, 3D after|
|Trade measurement||can||Generally not done||can|
|Can measure pulsating flow||can||Can’t||Can’t|
|Eddy current influence||no effect||influential||influential|
|Flow velocity distribution influence||no effect||influential||influential|
|One-time input price||high||low||low|
|Service life||More than 10 years||6 years||6 years|
|Daily maintenance fee||low||high||high|
|Does maintenance need to stop gas||Not needed||Not needed||Not needed|
Analysis of media characteristics of on-site metering points
1.The impact of dirt.
Coke oven gas contains impurities such as tar and naphthalene. These impurities will adhere to the pipes and also to the measuring instruments.
Impurities adhere to the probe of the ultrasonic flowmeter. It does not affect the measurement accuracy. It only reduces the intensity of the ultrasonic wave. According to the experience of using the ultrasonic flowmeter, the ultrasonic probe can still work normally if it is adhered with 1cm thick tar. Therefore, the ultrasonic probe is pulled out and cleaned regularly (usually three months) to ensure the normal operation of the ultrasonic flowmeter.
The adhesion of tar and naphthalene to the temperature measurement element of the thermal flowmeter will directly cause the temperature measurement data to be distorted. Therefore, the measurement performance is an abnormal increase in the flow rate data. The solution is to clean regularly, but the adhesion process is a gradual process, so the data of the flowmeter is gradually increasing.
Tar and naphthalene adhere to the target plate of the target flowmeter. It will cause the indication value to increase abnormally. The solution is to clean it regularly. However, the adhesion process is a gradual process, and the data of the flowmeter is constantly increasing.
From the comparison of the three, only the ultrasonic flowmeter is not affected by the pollution of coke oven gas.
The composition of coke oven gas is not a fixed value. The gas composition changes with the coal blending ratio. At the same time, the content of water vapor in the gas is also not a fixed value. It also changes with the outside temperature and the temperature in the pipeline.
The ultrasonic flowmeter directly measures the flow rate of the gas, and the measurement and calculation formula have nothing to do with the gas composition.
The target flowmeter is a differential pressure flowmeter. The measurement and calculation formulas have a great relationship with the gas composition, and the measurement is affected by the gas composition.
Thermal flow meters are mass flow meters, and the measurement and calculation formulas have a great relationship with the gas composition, and the measurement is affected by the gas composition.
3.Requirements for installation concentricity
Because the flowmeter is installed online, the on-site installation methods and methods put high demands on measuring instruments.
The most important thing in the installation of ultrasonic flowmeter is the centering of the probe, which is installed on the valve stub at the site. The flowmeter has an adjustment screw that can be fine-tuned. Ensure that the site installation is completely centered. At the same time, the ultrasonic flowmeter only needs to be installed on the central axis. There is no need to consider the influence of the dust at the bottom of the pipeline on the central axis of the pipeline.
Due to the product structure and working principle of the target flowmeter, the target plate needs to be installed on the center of the pipe cross-sectional area. Due to the dust accumulation at the bottom of the pipeline, concentric installation in the pipeline is extremely difficult. Therefore, the target flowmeter is not suitable for installation on the pipeline with dust accumulation at the bottom of the pipeline.
Thermal flow meters need to be installed on the center of the pipe cross-sectional area due to the product structure and working principle. Due to the dust accumulation at the bottom of the pipeline, concentric installation in the pipeline is extremely difficult. Therefore, thermal flow meters are not suitable for installation on pipes with dust at the bottom of the pipe.
4.The influence of dust accumulation in pipelines
Sino-Inst has been installing ultrasonic flowmeters on site for a long time. It has accumulated a complete set of calculation methods and measurement methods for the cross-sectional area of pipe dust. The influence of pipe dust on measurement can be reduced to a minimum. It can effectively avoid pipe dust on gas ultrasonic flow.
Use cost and economic benefit analysis
Because it is a transformation project, the characteristics of the wide range ratio of the gas ultrasonic flowmeter cannot be brought into play. In terms of one-time investment, the gas ultrasonic flowmeter is higher than the target flowmeter and the thermal flowmeter.
2.Long-term operating costs
Due to the long-term operation of the flowmeter, there are costs in the following aspects: equipment maintenance costs, calibration costs, replacement parts costs, and operator labor costs.
(1) Equipment maintenance fee
Because the ultrasonic flowmeter is a maintenance-free instrument. The routine maintenance work is only to clean the probe regularly. The maintenance difficulty and frequency of thermal and target flowmeters are greater than that of ultrasonic flowmeters, which require frequent maintenance. Therefore, the maintenance cost of the latter is huge Higher than the former.
(2) Daily maintenance
Because the target plate is deformed and stuck during use, the target plate needs to be replaced frequently, and the target plate needs to be replaced frequently, and the cost is increased. Ultrasonic flowmeter does not require replacement parts. The probe can be replaced and replaced under pressure. Clean, other parts don’t need to be replaced basically.
(3) Pumping costs
Due to the low pressure of coke oven gas, the low flow rate. The target plate of the target flowmeter is required to be large, and the pressure loss of the flowmeter is large, which increases the load of the compressor. After years of practice, it has been proved that the operating cost increases with the increase of pressure loss. Pumping costs are also a considerable expense.
(4) Labor costs
Operator labor costs. The daily maintenance of the target flowmeter is relatively high, and the labor cost is a lot. The ultrasonic flowmeter is unattended and basically does not need maintenance. Therefore, the cost of operation and maintenance for the ultrasonic flowmeter will be much lower than that of the target flowmeter.
Due to the measurement characteristics of the gas ultrasonic flowmeter, it can maintain good measurement accuracy and stability in the medium of coke oven gas for a long time. Therefore, it can provide a basis for the daily production management and scheduling of coke ovens in coking enterprises. Improve the level of comprehensive gas utilization , Reduce gas emissions and combustion. It can greatly help enterprises in energy saving and emission reduction. Significantly improve overall benefits.
Especially in the existing coke oven gas to natural gas project. Accurate measurement can effectively improve the management level of the enterprise. Improve the comprehensive use efficiency of coke oven gas, reduce costs and increase efficiency.
- Jiangsu Shagang Group lists gas ultrasonic flowmeters as the only selection instrument for gas measurement. More than 50 sets of gas ultrasonic flowmeters are used on coal gas. Energy management has been implemented for coke oven gas, converter gas and blast furnace gas since 2013 Since then, it has not only improved the comprehensive utilization efficiency of coal gas, but also increased the production efficiency of coke ovens. The annual gas emission rate control has also been effectively controlled, and the annual direct economic benefit is more than 40 million yuan.
- Shandong Weijiao Xuecheng New Energy is also in its coke oven gas to natural gas project. The gas ultrasonic flowmeter is included in the design selection as the only measuring instrument for coke oven gas.
To sum up, although the gas ultrasonic flowmeter has a large one-time investment, the long-term operating cost is low, and the management benefits are far greater than the equipment investment.
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Sino-Inst offer over 10 Flow Meters for Coke Oven Gas Measurement.
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