CN203463940U - Liquid ammonia leakage prevention device for denitration in thermal power plant - Google Patents

Abstract

The utility model discloses a liquid ammonia leakage prevention device for denitrification in a thermal power plant, which comprises a liquid ammonia station for storing liquid ammonia, a fire-fighting spray system is arranged in the liquid ammonia station, and a sunshade is arranged on the top of the liquid ammonia station. A plurality of fire water cannons are evenly arranged on the periphery of the liquid ammonia station, and an annular spray water curtain system is arranged around the sunshade to form a closed space after being joined with the sunshade. The utility model installs a water curtain spray system, and uses the water curtain to absorb ammonia to control the diffusion speed of ammonia gas when liquid ammonia leaks, effectively reducing the concentration of ammonia gas in the air, and ensuring the safety of the production personnel of the enterprise and the surrounding area of the liquid ammonia station. The life and property safety of personnel, the utility model fundamentally improves the controlled measures of the liquid ammonia station equipment, improves the safety management of the liquid ammonia station, and can reduce the risk of fire and explosion prevention and environmental pollution caused by the sudden leakage accident of the liquid ammonia station. down to the limit.

Description

A liquid ammonia leakage prevention device for denitrification in thermal power plants

technical field

The utility model relates to the field of fire safety, in particular to a device for eliminating and preventing leakage of liquid ammonia used for denitrification in a flue gas treatment device of a thermal power plant.

Background technique

In the field of thermal power, many power plants use ammonia as the raw material for denitrification of flue gas. The ammonia used mainly includes liquid ammonia, ammonia obtained after urea pyrolysis, and ammonia water. Among them, the use of liquid ammonia is the best, but liquid ammonia Ammonia is also the most dangerous. According to relevant national laws and regulations, the liquid ammonia station with liquid ammonia storage capacity exceeding 5T (critical value) is designated as a "major hazard source". The reserves are generally 50M ³ liquid ammonia storage tanks, so the safety of the liquid ammonia station must be strictly implemented in accordance with the regulations. However, in the prior art, the prevention plans for the liquid ammonia station are all aimed at prevention in advance. For the leaked ammonia gas, there are only conventional fire sprinklers, which arrange the pipelines on the liquid ammonia tank. When ammonia gas is detected In case of leakage, spray water to the liquid ammonia tank through the sprinkler head of the fire sprinkler device to dissolve the leaked ammonia gas in the water to achieve the purpose of prevention and control, but the control range of the above method is small, and when a large amount of ammonia gas leaks at the same time, It will be too late to react and spread to the surrounding area, causing harm to the surrounding environment.

Utility model content

In order to solve the problem in the prior art that the prevention of liquid ammonia in thermal power plants is only for prevention in advance, the utility model provides a prevention device capable of multi-layer protection and eliminating ammonia leakage after liquid nitrogen leakage. The specific scheme is as follows: a liquid ammonia leakage prevention device for thermal power plant denitrification, including a liquid ammonia station for storing liquid ammonia, a fire sprinkler system is arranged in the liquid ammonia station, and a sunshade is arranged on the top of the liquid ammonia station. That is, a plurality of fire-fighting water cannons are evenly arranged on the periphery of the liquid ammonia station, and an annular sprinkler water curtain system is arranged around the sunshade to form a closed space after joining with the sunshade.

In order to find liquid ammonia leakage in time: the fire sprinkler system includes an annular spray water pipe installed on the upper part of the liquid ammonia tank and the upper part of the evaporation tank area in the liquid ammonia station, and a rain nozzle installed on the spray water pipe. Sensors for ammonia leaks are located in the area of the tank.

In order to reduce the concentration of liquid nitrogen at the leakage point: there are six fire-fighting water monitors, and each fire-fighting water monitor is connected through a fire-fighting pipeline buried in the ground. The fire-fighting pipeline is provided with a valve isolating each fire-fighting water monitor. The fire water monitor is set based on the liquid ammonia station and it is determined that any leak point can be within the working range of two fire water monitors at the same time.

In order to recover the water after spraying: the spraying water curtain system includes the spraying main pipe arranged on the outer edge of the liquid ammonia station sunshade, the open rain nozzle installed on the spraying main pipe and the spout facing the ground, in the A water-retaining cofferdam is arranged outside the spray range of the open rain shower nozzle, and a backwater ditch is arranged on the ground inside the cofferdam, and the backwater ditch is connected with a sump, and the sump is used for spraying water by a water pump. Shower pipe water supply.

In order to improve the sealing effect of the spray water curtain: the spray main pipe is a double-pipe structure, and the two pipes are parallel to each other with a distance of 0.5-1.5 meters. The distance between the open rain shower nozzles on the root canal is 0.5-1.5 meters.

The utility model installs a water curtain spray system, and uses the water curtain to absorb ammonia to control the diffusion speed of ammonia gas when liquid ammonia leaks, effectively reducing the concentration of ammonia gas in the air, and ensuring the safety of the production personnel of the enterprise and the surrounding area of the liquid ammonia station. The life and property safety of personnel, the utility model fundamentally improves the controlled measures of the liquid ammonia station equipment, improves the safety management of the liquid ammonia station, and can reduce the risk of fire and explosion prevention and environmental pollution caused by the sudden leakage accident of the liquid ammonia station. down to the limit. The concentration of liquid ammonia at the leakage point can be reduced by the fire water cannon, and at the same time, the diffusion of liquid ammonia can be more easily absorbed by the spray water curtain. The double-ring arrangement of the spray main pipe can improve the sealing effect of the water curtain, and the use of the sump can improve the utilization efficiency of the spray water.

Description of drawings

The layout structure schematic diagram of Fig. 1 the utility model;

Explanation of the numbers in the attached drawings: 1-liquid ammonia tank, 2-fire sprinkler system, 3-fire water cannon, 4-spray water curtain system, 5-sunshade, 6-water collection tank, 7-fire pipeline, 8 - back gutters.

Detailed ways

As shown in Figure 1, the liquid ammonia leakage prevention device for thermal power plant denitrification of the present invention includes a liquid ammonia station for storing liquid ammonia, and a fire sprinkler system 2 is arranged around the liquid ammonia station. The sprinkler system 2 is a basic preventive device that must be installed according to national regulations. When ammonia gas leaks, the sprinkler head will be activated under the control of the control system to spray water mist on the liquid ammonia tank 1 to dissolve the leaked ammonia gas. In the water, so as to achieve the purpose of preventing ammonia leakage, fire sprinkler system 2 also has the effect of cooling liquid ammonia tank 1. On the basis of the above, this plan further adds two preventive measures to prevent the diffusion of ammonia gas after leakage. There are multiple fire water cannons 3 evenly arranged on the periphery of the liquid nitrogen station. The fire water cannons 3 can spray a large amount of water in a short time. Water passes through the water curtain to spray water point-to-point at the leak point. Through the impact of water, the high-concentration liquid ammonia at the leak point will be washed away and diluted, and also neutralized by water, so that the unneutralized diluted ammonia gas will spread, so that it is easier to be blocked and neutralized by the fire water curtain system 4. The spray water curtain system 4 in this scheme can produce the effect of a fully enclosed liquid ammonia station, and a sunshade 5 is generally arranged on the top of the liquid ammonia station. It can prevent the leaked ammonia gas from escaping from the top, and the spray water curtain system 4 is arranged in a ring around the liquid ammonia station, and uses the water sprayed downward to form a fully enclosed water curtain. The spray water curtain system 4. Together with the sunshade 5, the leaked ammonia gas will be sealed in the liquid ammonia station, and the leaked ammonia gas will be continuously neutralized in the process of contacting the water curtain until it is completely eliminated. All leaked ammonia gas can also be controlled within a certain range, preventing the leakage of ammonia gas from causing greater impact on the surrounding area, and providing sufficient maintenance time for eliminating leak points.

The fire-fighting sprinkler system 2 of the present utility model includes an annular spray water pipe installed on the upper part of the liquid ammonia tank 1 in the liquid ammonia station and the upper part of the evaporation tank area. Sensors to detect ammonia leakage are installed in the formed area. When ammonia gas leaks, the sensors distributed in various places will first detect it. When the ammonia gas concentration reaches a certain level, the control system will open the spray water pipe and spray the liquid ammonia gas through the rain nozzles arranged around each liquid ammonia tank 1. Water spray the tank area to eliminate all or part of the ammonia leak. The sensor also detects the temperature of the liquid ammonia tank while detecting liquid ammonia leakage, and activates the deluge nozzle to cool it down when the temperature of the liquid ammonia tank exceeds a certain value.

For the targeted treatment of leaking ammonia gas, the fire-fighting water cannon 3 of the utility model is provided with six sets, and each fire-fighting water cannon 3 is connected by the fire-fighting pipeline 7 buried in the ground, and the fire-fighting pipeline 7 is provided with Isolate the valves of each fire water monitor 3. Each fire water monitor 3 is evenly distributed around it with the liquid ammonia station as the base point. within the scope of work. The neutralization effect of ammonia gas leaked from the leakage point can be strengthened through the fire water monitor 3, and the high-concentration liquid ammonia can be dispersed at the same time. s efficiency.

In order to ensure the sealing effect of the spray water curtain system and to facilitate the recovery of spray water, the spray water curtain system 4 of the present utility model includes a spray main pipe arranged on the outer edge of the sunshade 5 of the liquid ammonia station, installed in the spray The open deluge nozzle on the main pipe with the spout facing the ground is provided with a water-retaining cofferdam on the outside of the spray range of the open deluge nozzle. The return ditch 8 and the sump 6 supply water to the spray main pipe through the water pump. The spray main pipe is close to the edge of the sunshade 5 to prevent the ammonia gas from escaping from the connection. At the same time, each open deluge nozzle can produce a certain range of spray water curtain, and the water curtain sprayed by each open deluge nozzle They are connected to each other to form a closed water curtain that isolates ammonia gas. The cofferdam can control the sprayed water within a certain range and make it easier for the sprayed water to return to the return ditch 8. The specific height of the cofferdam It is related to the diffusion range of the sprayed water from the open deluge nozzle. The height of the cofferdam in the utility model is about one meter, so that the water sprayed from the open deluge nozzle contacts the cofferdam at the middle and lower parts, forming a closed type. state, the use of cofferdams can also prevent ammonia from escaping from the bottom of the water curtain that is not tightly sealed and facilitate the convergence of spray water. The sump 6 is used to provide water sources for the entire preventive device and fire fighting device. The water neutralized with ammonia gas is returned to the sump by the return ditch 8, and the sump supplies water to the spray main pipe through the water pump, so that the spray water and the return water form a cycle, ensuring the spray water curtain system. full run. When an ammonia leakage accident occurs, the three-layer protection system is activated, and the leaked liquid ammonia is circulated and absorbed by the spray water curtain to form dilute ammonia water and enters the sump 6 through the return ditch 8. Since the dilute ammonia water is alkaline, it is based on the principle of ammonia desulfurization , and use the pump to recover the dilute ammonia water in the sump to the desulfurization absorption tower. The dilute ammonia water formed during each accident should be reused as much as possible, and a sufficient amount of fresh water should be injected into the sump again to keep the water curtain spray system in a good standby state. At this time, the fire sprinkler system and the fire water cannon can also be connected with the fire pipeline of the whole power plant through pipelines.

In order to improve the sealing effect of the water curtain, the spray main pipe of the utility model is a double-pipe structure, and the two pipes are parallel to each other with a distance of 0.5-1.5 meters. On the main pipe, the distance between the open deluge nozzles is 0.5-1.5 meters. Both pipes are equipped with open deluge nozzles, but the positions of the open deluge nozzles on the two pipes are staggered from each other. According to the installation height of the spray main pipe, the utility model adopts the above-mentioned limited values. Under this structure Can achieve the most perfect sealing effect. The spray main pipe of this scheme is supported by a steel structure, and the distance between the centers of the two pipes is 1.0 meters. Open deluge nozzles are evenly installed on each annular main pipe, and the distance between each open deluge nozzle is 1 meter. 193 nozzles.

The utility model is set based on the following theoretical basis:

Assuming that ammonia diffuses in the air in a hemispherical shape, using Graham's gas diffusion law - "the diffusion speed of various gases at the same temperature and pressure is inversely proportional to the square root of the gas density" is determined as follows:

$\frac{u_A}{u_B}=\sqrt{\frac{{\mathrm{\ρ}}_B}{{\mathrm{\ρ}}_A}}$ Depend on $\mathrm{\ρ}=\frac{\mathrm{PM}}{\mathrm{RT}}$ Substitute to get $\frac{u_A}{u_B}=\sqrt{\frac{m_B}{m_A}}$

Among them: M _A - the molecular weight of ammonia, M _B - the molecular weight of air, u _B - the average wind speed of the year, m/s;

Obtain the diffusion velocity u _A of ammonia in the air to be 1.95m/s,

Assume that when a leakage accident occurs in the liquid ammonia storage tank, the diameter of the liquid ammonia leakage opening is 1cm, the pressure of the liquid ammonia storage tank is 1.6MPa, the ambient temperature is 20°C, and the area of the leakage opening is A=7.85×10 ^-5 m ² , according to Bernoulli Profit equation:

${\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}\mathrm{<span\; class="notranslate">\; A\&rho;</span>}\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; P</span>}}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; gh</span>}$

Among them: Q _L - liquid leakage rate, kg/s; C _d - liquid leakage coefficient; A - breach area, P - medium pressure in the container, P ₀ - ambient pressure, g - acceleration of gravity, h - liquid level above the breach Height, substituting the data to obtain the leakage Q=2.35kg/s.

The diffusion speed after liquid ammonia leakage is very fast. Assuming that the space in the middle of the entire water curtain is filled within 1 second after the leakage of liquid ammonia, the size of the water curtain space is calculated based on the orthographic projection of the outer edge of the awning on site and the space height:

V=24.5×15.5×3=1139.25m ³

At this time, the ammonia concentration in the entire water curtain space is:

C ₀ =2.35×10 ⁶ ÷ V=2063.15mg/m ³

During the liquid ammonia diffusion process, the absorption efficiency when passing through the first layer of protection (fire sprinkler system on the liquid ammonia tank) is taken as 30%, and the absorption efficiency when passing through the second layer of protection (fire water cannon) is taken as 25%. The absorption efficiency of the three double-layer water curtains is 38%, then the concentration of ammonia discharged into the atmosphere after being absorbed by the three-layer water curtain is:

C ₁ =C ₀ -C ₀ ×0.3-C ₀ ×(1-0.3)×0.25-2×0.38×C ₀ ×(1-0.3)(1-0.25)=416.36mg/m ³

After simulating by EIAA software (environmental impact assessment software), it is concluded that when the concentration of the escaping water curtain discharged into the atmosphere is 416.36mg/m ³ , the ammonia concentration at 100 meters through natural diffusion is 28mg/m ³ . According to the national safety distance standards for the construction of relevant liquid ammonia stations and the relevant regulations of the "Industrial Enterprise Design Hygienic Standards", the ammonia concentration of 28mg/ ^m3 is lower than the maximum allowable concentration of 30mg/ ^m3 . It can be seen that the three-layer water curtain ammonia absorption process is very effective in preventing ammonia leakage and diffusion.

In addition, when an accident occurs, the influence of temperature and concentration changes also needs to be considered, among which:

Temperature change: when liquid ammonia leaks, the gasification process will absorb heat and cool down rapidly. The heat of vaporization of liquid ammonia is 1166.17KJ/kg, while the dissolution of ammonia gas in water is an exothermic process, and its heat of dissolution is 2046.12KJ/kg. The specific heat capacity is 4.2KJ/kg, and the amount of spray water in the accident state is large, so the heat released during the ammonia dissolution process has little impact on the overall environment.

Concentration change: Since ammonia gas is easily dissolved in water, the concentration of ammonia water formed after ammonia leakage is absorbed by a large amount of spray water will be far lower than the saturation concentration of ammonia water, and the spray water can be collected and recycled for recycling. .

This solution is controlled by a leakage monitoring system, which includes sensors installed around the liquid ammonia station and a control center that receives sensor signals, and the control center activates corresponding preventive equipment according to the leakage status detected by the sensors. In the event of a liquid ammonia leakage accident, when the leakage exceeds a fixed value, the leakage detection device will alarm and trigger the water curtain spray pump to start, and the system valves will be linked. With the water curtain spraying, the ammonia gas will be absorbed by the water curtain cycle. When the ammonia gas concentration When it is lowered to the set value, the preventive device will automatically stop running. The start and stop of the preventive device in this scheme can realize both automatic and manual intervention control of the upper computer. In this scheme, the spraying main pipes with double-ring structure can be started separately or synchronously. The starting conditions are determined according to the concentration of ammonia gas, such as:

When the ammonia gas concentration reaches 80ppm due to the leakage of the liquid ammonia station, the inner ring pipe sprinkler system will be activated; otherwise, it will be shut down.

When the ammonia gas concentration reaches 100ppm due to the leakage of the liquid ammonia station, the sprinkler system of the outer ring pipe will be activated; otherwise, it will be shut down.

The above descriptions are only preferred embodiments of the present utility model, and do not limit the utility model in any form. Although the utility model has been disclosed as above with preferred embodiments, it is not intended to limit the utility model. Without departing from the scope of the technical solution of the utility model, the technicians of this patent may use the technical content of the above prompts to make some changes or modify them into equivalent embodiments with equivalent changes, but all do not depart from the content of the technical solution of the utility model Any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the utility model still belong to the scope of the solution of the utility model.

Claims (5)

1.Yi Zhong thermoelectricity plant denitration A leak of liquefied ammonia crime prevention device, comprise for storing the liquefied ammonia station of liquefied ammonia, in described liquefied ammonia station, be provided with spraying system of fire fighting (2), the top at liquefied ammonia station is provided with sky shade (5), it is characterized in that, the periphery at described liquefied ammonia station is evenly provided with a plurality of Fire water monitors (3), forms the annular spray water curtain system (4) of enclosed space after the surrounding of described sky shade (5) is provided with and engages with sky shade (5).

2. a kind of thermoelectricity plant as claimed in claim 1 denitration A leak of liquefied ammonia crime prevention device, it is characterized in that, described spraying system of fire fighting (2) comprises the ring-type spray header that is arranged on (1) top of ammonia tank in liquefied ammonia station and top, evaporator tank region, and be arranged on the nozzle that drenches with rain on spray header, in the region of ammonia tank (1), be provided with the sensor that detects ammonia leakage.

3. a kind of thermoelectricity plant as claimed in claim 1 denitration A leak of liquefied ammonia crime prevention device, it is characterized in that, described Fire water monitor (3) is provided with six, each Fire water monitor (3) connects by being embedded in underground fire main (7), on described fire main (7), be provided with the valve of each Fire water monitor of isolation (3), each Fire water monitor (3) be take liquefied ammonia station as basic point setting and is determined that any one leakage point is simultaneously in the operating range in two Fire water monitors (3).

4. a kind of thermoelectricity plant as claimed in claim 1 denitration A leak of liquefied ammonia crime prevention device, it is characterized in that, described spray water curtain system (4) comprises the female pipe of spray that is arranged on liquefied ammonia station sky shade (5) outer edge, be arranged on the upper and open type of spout towards ground of the female pipe of the spray nozzle that drenches with rain, in the drench with rain spray field arranged outside of nozzle of open type, there is the cofferdam of dash, on the ground of inner side, described cofferdam, be provided with backwater ditch (8), described backwater ditch (8) is connected with catch basin (6), and described catch basin (6) is that the female pipe of spray supplies water by water pump.

5. a kind of thermoelectricity plant as claimed in claim 1 denitration A leak of liquefied ammonia crime prevention device, it is characterized in that, the female pipe of described spray is double pipe structure, between two pipes, be parallel to each other and span is 0.5-1.5 rice, the nozzle interval setting of staggering that drenches with rain of open type on two pipes, the nozzle span that drenches with rain of each open type on same pipe is 0.5-1.5 rice.

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