Application of V Cone Flowmeter in Gas Works

I. Overview Kunming coking gas plant coke oven gas metering main measuring points are: coke oven re-melting gas, boiler gas blended, tube furnace gas and gas supply outside the city, in addition, there are furnace gas metering and holidays mixed Petroleum liquefied gas metered into gas. In the past, coke oven gas has been measured using standard orifice plates and constant velocity tubes. There are mainly the following problems in the use process:
(1) The coke oven gas is dirty, the orifice plate is easy to be contaminated, because the continuous production can not remove the orifice plate for cleaning, affecting the system measurement accuracy;
(2) The coke oven gas is dirty, the instrument pressure tube is easy to be blocked, and the instrument pressure tube must be regularly purged with steam, otherwise it will affect the measurement accuracy, or even the system can not run normally;
(3) The steam or water mist entrained in the gas will be condensed into water when the temperature is lowered, which is difficult to eliminate in the pipeline and affect the measurement accuracy of the system.
(4) The length of the straight section is long, and the diameter of the gas pipeline is usually relatively large. It is difficult to ensure that the 20 to 40D straight section of the flow measurement is accurate.
(5) The small range ratio is only 3:1. For example, due to the difference in the amount of gas to be delivered when the city gas usage peaks or falls, the delivery volume of the ex-factory gas meter changes more than 10:1 in a single day, and the orifice plate has a lower range ratio. Small can not reach the use requirements.

1 Measuring principle of gas flowmeter Like other differential pressure flowmeters, gas flowmeters are based on the Bernoulli's theorem for energy conversion in closed pipes. That is, for ideal fluids, the velocity of the medium is proportional to the square root of the differential pressure. When the medium flows at a certain flow rate in the direction of the cone tip, due to the throttling effect of the cone, a low pressure zone will be formed downstream of the cone, and through the throttling effect of the cone, a low pressure zone will be formed downstream of the cone through the cone. The body upstream of the pipe wall to take high pressure P1, the hollow pipe connecting the pipe wall and the cone tail to take the low pressure P2, to the pressure transmitter to measure the pressure difference â–³P, see Figure 1, according to the Bernoulli equation, the volume can be calculated Traffic qvc

In the formula, K is the meter coefficient; ε is the gas expansion coefficient, and ρ is the working density of the fluid.
Because the wall friction reduces the velocity of the fluid flowing through the tube wall, the flow velocity distribution in the tube is as follows: the flow velocity approaches zero at the tube wall, the greater the flow velocity is closer to the center of the tube, and the flow velocity is the largest at the center of the tube. When the fluid flows through the gas flowmeter, the gas flowmeter throttles by suspending a gas body in the center of the pipeline. The cone directly interacts with the high-speed center portion of the fluid to force the high-speed fluid in the center of the pipeline and the low velocity fluid near the wall of the pipeline. Homogenization means that the flow rates of the two tend to be the same.

Compared with the structure of various throttling devices, the standard orifice is a sudden contraction of the fluid in the center of the pipe, which not only has a large resistance loss, but also aggravates the non-uniformity of the flow velocity distribution of the fluid. The edge of the pipe is blocked, and the dirty media gathers in the standard orifice plate. Before and after; Venturi tube (still the same as the standard orifice plate is still a standard throttling device) is gradually shrinking in the pipe center, although the uneven flow of the fluid velocity distribution is still there, but the resistance loss is slightly reduced, dirty media The situation of agglomeration has improved, but it is difficult to make; the annular orifice plate is placed in the center of the pipe, and the edge of the pipe can be circulated, that is, the sudden contraction from the center of the pipe of the standard orifice plate to the sudden shrinkage of the pipe edge, and therefore The uniform flow velocity in the pipeline can make the dirty media not gather around the annular orifice plate; and the gas flow meter sets a cone in the center of the pipeline. Its structure is that the pipeline edge shrinks gradually, the resistance loss is small, and the flow velocity in the pipeline can be made. Homogenization, so that the dirty media will not accumulate before and after the annular orifice. It is concluded that gas flowmeters are the inevitable result of a series of innovations in the development of throttling devices, see Figure 2.

2 Application of Kunming Coking Gas Plant In 2002, the Kunming Coking Gas Plant in the construction of a new project designed to use three Kingways Control gas flowmeters, a coke oven gas (1200mm plug-in), and a furnace The flow rate of gas (400mm pipeline type) and liquefied petroleum gas (270mm pipeline type) was measured. Because of the good use effect, two gas flowmeters (250mm and 400mm) were used in the combustion of boiler gas.
3 characteristics of gas flowmeter Kunming coking gas plant using gas flowmeter has three years of history, the detection system is operating normally, and the daily maintenance workload is almost no, welcomed by the scene of workers and technical staff. The main features are as follows.
(1) Straight pipe section requirements are low. Although all differential pressure flowmeters are measured according to Bernoulli's theorem, Bernoulli's theorem has a basic requirement that the fluid being measured must be an ideal fluid. When orifice plates, nozzles, and other conventional differential pressure flowmeter throttling devices are used, in order to satisfy the requirements of Bernoulli's theorem as much as possible, it is necessary to have very long front and rear straight pipe segments in order to shape the irregularly flowing fluid as much as possible. Ideal fluid. The gas flow meter uses a unique streamlined throttling structure designed at the center of the pipeline. Before detecting the flow rate, the irregularly flowing fluid is rectified at the same time. The fluid rectification problem is subtly solved without increasing the flow rectifier. . The streamlined cone suspended from the center can reshape the flow velocity curve. Immediately in the narrow area upstream and downstream of the cone (0 to 3 D before, 0 to 1 D after), the liquid with irregular flow rate can be directly rectified into an ideal liquid, which can be sufficient. Satisfy the Bernoulli theorem, obtain high measurement accuracy and repeatability. It does not require very long straight section rectification, which is of great significance during the installation of the flow meter. In the installation process of the liquefied petroleum gas flowmeter (diameter of 270mm) used by Kunming Coking Gas Plant, the distances between the front and rear straight pipes of the flowmeter are 1000mm and 600mm, respectively, due to site conditions. However, the flowmeter can still operate normally and stably. .
(2) Resistant to pollution, not easy to block. Kunming Coking Gas Plant gas flow measurement, the original use of orifice flowmeter and average velocity tube flowmeter, because the gas contains tar, naphthalene, sulfur, ammonia and other impurities, orifice plate or constant velocity tube must be cleaned regularly Or use steam purging, otherwise the orifice on the orifice plate, the downstream end face, and the upstream side inlet edge will be contaminated, and the pressure guiding tube of the instrument will not be open or blocked, which will affect the measurement accuracy of the system; the water accumulation in the straight section of the orifice plate will make the pipeline circulate. The area is reduced, the flow rate is increased, the differential pressure is increased, the flow rate display value is high, and the pressure transmitter is blocked due to the clogging of the pressure guiding tube. The transmitter cannot operate normally. In order to ensure the normal and stable operation of the instrument, the maintenance workload of the instrumentation worker is large. The gas flow meter has self-purging structural design features, without dead space. When the medium flows through the cone, it will accelerate, constantly flushing the positive pressure taking hole, the outer wall of the cone and the wall near the cone, and the negative pressure taking hole is isolated by a small non-flowing medium, so that dirty impurities cannot enter. Therefore, the gas flow meter can be used for various contaminated and easily crystallized dirt media, such as coke oven gas and producer gas. The flow rate of five gas flowmeters for coke oven gas, producer gas, and liquefied petroleum gas used in Kunming Coking Gas Plant was measured. Some of them have been used for three years and have not been maintained so far. Flowmeters have not been found with flowmeters. Contamination, plugging of instrumentation pressure pipes, water accumulation in pipelines, abnormal flow display values, etc. greatly reduced the maintenance workload of the instrument and improved the accuracy and reliability of gas flow measurement.

Rice Hulling Combination Rice Machine

The combined rice husker has the advantages of low power, low energy consumption, large output, easy operation and good maintenance. The machine consists of a single-link elevator, a multifunctional cleaning and stone removing machine, a new split rice huller ( the core part of the equipment ), a double-link elevator, a grain rough separating screen, a negative pressure rice refining machine, a broken rice separating screen, a multifunctional crusher and a central centralized controller. The fuselage is made of wear-resistant glass pipes, which are durable and beautiful.

Equipment parameter:

Equipment model Rice output(kg/h) Milled rice rate(%) Weight of equipment(kg) Equipment power(kw) Dimension(L×W×H) Power input(V/Hz)
MLNS 20/15 700-1000 69-75 1650 33 3200×1900×3000 380/50

Main characteristics of rice milling machine:

1. compact construction, beautiful appearance.

2. less broken rice increment.

3. easy to operate.

4. steady performance.

5. national patents.

rice milling machine

MLNS 20/15 Rice Mill Machine

MLNS 20/15 Rice Mill Machine,Automatic Rice Mill Machine,Small Combined Rice Mill Machine,High Efficiency Rice Mill Machine

Sichuan Doujin Technology Co., Ltd. , http://www.doujinmachine.com

Posted on