Most of the energy measurement is completed by using the flowmeter, which depends on the flowmeter with the corresponding accuracy level that can meet the measurement requirements. There are many kinds of flow meters on the market, but with the support of the corresponding mature technical capacity, the performance is not much different. In this way, although the selectivity is strong, different flow meters cause different pressure losses to the pipeline under the same pipe diameter and flow conditions. Pressure loss is a super energy consumption in energy measurement.
Flow meters are generally installed in the flow pipeline. At this time, the flow meter is actually equivalent to a resistance part in the flow pipeline. When the fluid passes through the flow meter, it will produce pressure loss and cause certain energy consumption. The smaller the pressure loss, the smaller the additional power required to transport fluid in the pipeline, the smaller the energy consumption caused by pressure loss and the lower the energy metering cost; On the contrary, the greater the energy consumption caused by pressure loss, the higher the energy measurement cost. Some people may think that it's too fussy about how much energy consumption this pressure loss can cause. Let's not talk about anything else here. Let's talk about whether this so-called haggling is worth it or not.
For example, there is such a metering point that the orifice meteormeter is used on the pipeline conveying medium pressure steam, the process design medium temperature T = 330 ℃, and the pressure
P = 3Mpa, maximum flow Qmax = 200t / h, common flow QT = 160t / h. According to the calculation, the diameter ratio of the selected orifice plate β= 0.63226, maximum differential pressure △ Pmax = 133.51kpa, density of medium pressure superheated steam P = 11.5143kg/m3.
(1) common differential pressure AP of orifice flowmeter under common flow QT
AP=(Qt/Qmax)2? APmax=(160/200)2? 133.51kpa = 85.4464kpa (2) pressure loss DP of orifice flowmeter under common flow QT
dP=(1-32)? AP=(1-0.632262)? 85.4464kPa=51.29kPa
(3) Calculate the additional energy consumption caused by orifice flowmeter under common flow QT with the following formula: WW = (DP? QT) / (3.6? N? P)
W - energy consumption in the formula; DP -- pressure loss value, kPa; QT -- common mass flow of superheated steam, kg / h; N - efficiency of pump and motor (usually n = 0.8); P -- density of superheated steam under working conditions, kg / m3. be
W=(51.29?160000)/(3.6?0.8?11.5143)=247470W
(4) Additional annual energy consumption cost of orifice flowmeter
If the local industrial electricity price is 0.725 yuan / kW? h. Then
Annual energy consumption fee (yuan / year) = (w / 1000)? (operating hours / year)? (0.725 yuan / kW? H) = (247470 / 1000)? (24?365)? (0.725 yuan / kW? H) = 1571681.97 yuan
I really don't know. I'm scared. This data is amazing. Unknowingly, the pressure loss of an orifice flowmeter can eat more than one million yuan. If the enterprise installs 200 orifice meters, the energy consumption caused by orifice meters will be as high as nearly 300 million yuan a year.
Some people may think that the orifice flowmeter is a special case, because its working principle is equivalent to adding a baffle in the pipeline. Of course, the pressure loss is large. Maybe the flowmeter without changing the flow diameter will not have so much energy consumption. Let's take a look at Coriolis mass flowmeter.
(5) Additional annual energy consumption cost of Coriolis mass flowmeter
There is such a metering point. Coriolis mass flowmeter is used in DN150mm pipeline to measure crude oil. Relevant process parameters are as follows:
Crude oil flow Q = 450t / h, crude oil density p = 878kg / m3, permanent pressure loss DP = 0.35Mpa, then the additional annual energy consumption cost caused by the flowmeter is calculated as follows:
w=(dP?Qt)/(3.6?n?p)
W - energy consumption in the formula; DP -- pressure loss value, kPa; QT -- mass flow of crude oil, kg / h; N - efficiency of pump and motor (usually n = 0.8); P -- density of crude oil under working conditions, kg / m3. be
w=(350?450000)/(3.6?0.8?878)=62286W
If the local industrial electricity price is 0.725 yuan / kW? h. Then
Annual energy consumption fee (yuan / year) = (w / 1000)? (operating hours / year)? (0.725 yuan / kW? H) = (62286 / 1000)? (24?365)? (0.725 yuan / kW? H) = 395578.39 yuan
If the enterprise installs 100 Coriolis mass flowmeters, the additional pump transmission energy consumption due to the operation of the flowmeter can reach more than 40 million yuan every year. This is a huge invisible energy consumption, but it is often ignored.
Then some people will say that since the provision of energy measuring instruments will cause such a large additional energy loss, it is not necessary to provide energy measuring instruments. However, everything should be viewed dialectically, and we should not give up eating because of choking. In order to ensure the normal progress of continuous production, facilitate the real-time grasp of various parameters in the control of technological process, and ensure various indicators of product quality, relevant energy measuring instruments must be equipped. So, how to meet the production needs and minimize the energy consumption? The following suggestions are put forward for reference.
1, we can rely on scientific progress, adopt new technologies and materials, carry out energy-saving technical transformation of equipment with high energy consumption, ask for energy from technical transformation, and eliminate high energy consumption flow meters. Only when the energy-saving technological transformation is carried out well and the additional energy consumption is minimized, can the enterprise achieve significant economic benefits. Of course, the introduction of advanced technology and equipment requires capital investment, which may feel more investment at the beginning, but from a long-term perspective, it is conducive to energy and resource conservation and is also in line with the scientific outlook on development of sustainable development.
2, in the design and selection of flow meter, on the one hand, on the premise of meeting the production needs, we should design elbows, valves, regulating valves and other equipment that may cause pressure loss as little as possible. When the diameter can not be reduced, we should not arbitrarily reduce the diameter and use the flow meter because of some unimportant factors. We should pay attention to the greater pressure loss caused by diameter reduction and the more amazing energy consumption; On the other hand, the flowmeter with small pressure loss should be selected as far as possible on the premise of meeting the measurement accuracy, rather than taking the price of the flowmeter as the selection standard. In the international famous classic monograph on flow measurement In the flow measurement engineering manual compiled by Mr. Miller, there is such a paragraph: "for continuous industrial production process, the additional energy consumption cost caused by permanent pressure loss is an important factor that must be considered in the selection of flowmeter, especially for pipes with large diameter and large flow, which are controlled by pump or compressor (fan) The energy consumption cost of transporting fluid is very large. In this case, a flowmeter with small permanent pressure loss shall be selected. Although this flowmeter may be more expensive, it can prove that it is cost-effective. "
3, during the operation of the installed flowmeter, it is necessary to strengthen the maintenance and constantly monitor whether the data of the flowmeter is abnormal, especially for the flowmeter that is prone to pipeline blockage due to dirt, such as orifice plate, turbine and vortex street. If the inspection is not in place and the maintenance is not timely, greater pressure loss will be caused by pipeline blockage, which will increase a lot of energy consumption in the careless work, Thus causing the loss of economic benefits.
4, when it is possible to obtain the required measurement data through other means, meteor meters cannot be added because of convenience or so-called more accuracy, which is not only a waste of resources, but also a huge energy consumption due to increased pressure loss. For example, with the deepening of cost accounting, some units have added a large number of Energy Star counting instruments in order to clarify or more accurately obtain their own production cost data. Although the data is more accurate to some extent, it is ultimately internal measurement data, Some data can be obtained indirectly through other data (such as tank volume, other flowmeter components, etc.), so there is no need to install additional flowmeter, and this accuracy is unnecessary, sometimes even a waste, because it will increase the production cost of the whole enterprise.
5, we should strengthen management. The enterprise shall organize special personnel to make statistics on the energy consumption of the enterprise, analyze the energy consumption of various equipment causing energy consumption, cancel and dismantle the measuring instruments belonging to repeated measurement, and carry out technical transformation for those with high energy consumption; And improve the corresponding management system to make this work sustainable.
