CN101551402A - Pitot tube used for fixing continuous and automatic monitoring system of pollution source fume - Google Patents

Abstract

The invention discloses a pitot tube used for fixing a continuous and automatic monitoring system of pollution source fume, comprising a dynamic pressure tube (1) and a static pressure tube (2). The pitot tube is characterized in that a tube mouth section (3) of the dynamic pressure tube and a tube mouth section (4) of the static pressure tube bend relatively; a dynamic pressure tube mouth (5) and a static pressure tube mouth (6) are relative; a dynamic and static pressure isolating plate (7) is arranged between the dynamic pressure tube mouth and the static pressure tube mouth; and a set gap (8) and an inclined angle (9) of 0 degree to 60 degrees are respectively maintained among the dynamic pressure tube mouth, the static pressure tube mouth and the dynamic and static pressure isolating plate. The pitot tube avoids the dynamic pressure tube mouth from directly facing the flowing direction of fume, can effectively prevent the pitot tube from being plugged and utilizes self-exciting oscillation of fume flow to clean the fume automatically.

Description

A kind of pitot tube that is used for fixing pollution source fume continuous and automatic monitoring system

Technical field

The present invention relates to a kind of pitot tube that is used for fixing pollution source fume continuous and automatic monitoring system, belong to the fume emission monitoring technical field.

Background technology

Fume continuous and automatic monitoring system (CEMS, Continuous Emission MonitoringSystem) from last century the eighties at first since install and use the Chinese large-sized fuel-burning power plant, especially last year, State Environmental Protection Administration was since promoting state's control major polluting sources installation construction pollution source monitoring system, and integral body has driven the technical development of CEMS industry.CEMS generally requires to measure sulphuric dioxide, oxides of nitrogen, particle concentration and the relevant Gas Parameters parameters such as (temperature, pressure, flow velocity, oxygen level, humidity) thereof of flue gas.The on-line monitoring of fixed-contamination emission sources such as present known flue, chimney, gas outlet, the flow velocity of flue gas is an important parameter must measuring, the common method of measurement of flue gas flow rate has three kinds at present, is respectively S type pitot tube method, heat balance method of and supercritical ultrasonics technology.Pitot tube method and heat balance method of are point measurement, and supercritical ultrasonics technology is measured for the line formula, and the three is the wet basis flow velocity.Wherein S type pitot tube method is modal a kind of flue gas flow rate measuring method.

Pitot tube has two pipes of gathering flue gas, and a root canal orifice facings the wind (being called dynamic pressure tube), a root canal orifice leeward (being called static tube), and the kinetic energy of the flue gas stream of being gathered converts the pressure energy to.When in the flue air current flow being arranged, dynamic pressure tube mouth of pipe windward side is subjected to gas shock, thereby dynamic pressure tube pipe internal pressure is higher, and its pressure is called " total head ", the static tube mouth of pipe is leeward, owing to be not subjected to the air-flow punching press, the pressure in its pipe is static pressure, is called " static pressure ", the difference of total head and static pressure is called differential pressure, its size is relevant with flue gas flow rate (amount) (claiming wind speed again) in the pipe, and flue gas flow rate (amount) is big more, and differential pressure is big more; Wind speed (amount) is little, and differential pressure is also little, therefore, only measures the size of differential pressure, finds out the corresponding relation of differential pressure and wind speed (amount) again, just can correctly measure discharging flue gas flow rate (wind speed) in the pipe.

As shown in Figure 1, be the pitot tube synoptic diagram that uses in the prior art, its structure is to be made of side by side two tubes, wherein pipe sample tap over against gas flow direction to be measured, be used to measure the dynamic pressure value; Another root pipe sample tap is used to measure static pressure back to gas flow direction.Owing to contain a large amount of flue dust and tar in the tested gas, in actual measurement, find S type pitot tube in practical process, flue dust and tar are in order to stick on the air intake opening, and its exhaust flow velocity is calculated by following formula:

$\mathrm{Vsi}=\mathrm{Kp}\sqrt{\frac{2\mathrm{Pdi}}{\mathrm{ps}}}$

Vsi----measurement point discharge speed, m/s;

Pdi----measurement point discharging dynamic pressure, Pa;

Kp----pitot tube correction coefficient;

Wet exhaust density in the pipeline under the Ps-----measurement state, Kg/m3;

Learn that by following formula pressure is unimpeded relevant with the gas circuit of pitot tube, the air intake opening chocking-up degree influences the measurement of pressure, and flow velocity is relevant with Kp---pitot tube correction coefficient simultaneously, and the pitot tube correction coefficient is relevant with the sample tap sectional area.There are a large amount of flue dust and tar to stick on the sample tap in the actual measurement, directly influenced the sectional area size of air intake opening.

Find in the actual measurement that existing S type pitot tube sample tap is adhered to by flue dust and tar easily, particularly under the big situation of the low smoke moisture of the flue-gas temperature after the wet desulphurization, because existing moisture dewfall in the flue gas to cause flue dust to cohere results in blockage, thereby changed the sectional area size of pitot tube air intake opening, pressure measurement errors is increased, influence the measurement of other parameters such as flow velocity.

Chinese patent (patent No. 200320115566.6) discloses a kind of anti-blocking standard pitot tube, it belongs to a kind of pressure and measurement of rate of flow instrument of gas, as shown in Figure 2, the synoptic diagram that has the choke preventing function pitot tube in its prior art, special feature is: the bigger air inlet tube chamber 16 of opening that goes pressure head 15 front end axial centre to be provided with to link to each other with total head interface channel pipe 12, be provided with an air chamber 13 that is connected with static pressure interface channel pipe 11 at pressure 15 rear portion, place at close pressure 15 openend in the front of air chamber 13 is provided with a ring cutting groove 14 radially that is used for the static pressure air inlet, and ring cutting groove 14 A/Fs are 1 with pressure 15 diameter ratio: 20-1: 8. UEFA Champions League has more than 1 aperture to communicate with air chamber in the ring cutting groove 14.The logical primary standard pitot tube of its ways of measure pressure is the same, can measure total head, static pressure, dynamic pressure simultaneously, and measuring accuracy is done.Reach anti-stifled purpose by the ring cutting groove of setting up 14.But in fact along with the carrying out of service time, the turning point between ring cutting groove 14 places and air intake opening also is easy to generate obstruction, therefore appoints the structural improvement that needs a kind of pitot tube can overcome the defective that crock stops up fully.

Summary of the invention

Problem to be solved by this invention is to overcome the defective that prior art exists, and a kind of pitot tube that is used for fixing pollution source fume continuous and automatic monitoring system is provided, and can solve flue gas flow rate effectively and measure a ubiquitous above-mentioned difficult problem.

A kind of pitot tube that is used for fixing pollution source fume continuous and automatic monitoring system of the present invention, comprise dynamic pressure tube and static tube, it is characterized in that: the mouth of pipe section of described dynamic pressure tube and the mouth of pipe section of static tube are crooked in opposite directions, the dynamic pressure tube mouth of pipe is relative with the static tube mouth of pipe, between the dynamic pressure tube mouth of pipe and the static tube mouth of pipe dynamic and static pressure division board is set, all keeps the gap of setting between the dynamic pressure tube mouth of pipe, the static tube mouth of pipe and the dynamic and static pressure division board and keep 0 °～60 ° angles.

Pitot tube of the present invention avoids the dynamic pressure tube mouth of pipe directly in the face of the flow of flue gas direction, can prevent effectively that pitot tube from stopping up, and utilize the self-oscillation of flue gas stream to clean flue dust automatically, and the size of pitot tube is little, and layout is convenient, measures stable.In order to overcome ubiquitous wearing and tearing of flue gas measuring process and etching problem, this pitot tube can adopt pottery or multinomial technologies such as PTFE spraying and PFA sheath to form special abrasionproof anticorrosion structure.

Description of drawings

Fig. 1 is existing pitot tube structural representation;

Fig. 2 is existing pitot tube structural representation;

Fig. 3 is a pitot tube structural representation of the present invention.

Embodiment

Below in conjunction with accompanying drawing, invention is described in further detail.

As shown in Figure 3, a kind of pitot tube that is used for fixing pollution source fume continuous and automatic monitoring system comprises dynamic pressure tube 1 and static tube 2.The mouth of pipe section 3 of described dynamic pressure tube and the mouth of pipe section 4 of static tube are crooked in opposite directions, the dynamic pressure tube mouth of pipe 5 is relative with the static tube mouth of pipe 6, between the dynamic pressure tube mouth of pipe and the static tube mouth of pipe dynamic and static pressure division board 7 is set, all keep the distance 8 of 5mm between the dynamic pressure tube mouth of pipe, the static tube mouth of pipe and the dynamic and static pressure division board and keep 0 °～60 ° angles 9, that is, this angle can be the arbitrary value between 0 °～60 °.

Claims (1)

1, a kind of pitot tube that is used for fixing pollution source fume continuous and automatic monitoring system, comprise dynamic pressure tube (1) and static tube (2), it is characterized in that: the mouth of pipe section (3) of described dynamic pressure tube and the mouth of pipe section (4) of static tube are crooked in opposite directions, the dynamic pressure tube mouth of pipe (5) is relative with the static tube mouth of pipe (6), dynamic and static pressure division board (7) is set between the dynamic pressure tube mouth of pipe and the static tube mouth of pipe, all keeps the gap of setting (8) between the dynamic pressure tube mouth of pipe, the static tube mouth of pipe and the dynamic and static pressure division board and keep 0 °～60 ° angles (9).

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