SU1237579A1 - Method of removing gas from reservoir - Google Patents

Description

The invention sent to the trapeeport and stored gaseous substances, which form airborne mixtures with a capacity of 1, ear, and can be used to remove residues from () -, and your) gas from containers, used in chemical, petrochemical, refrigeration industry, on automobile, same, 1 railroad transnorge, li aviation, airship, first construction, space technology, during the operation of gas storages, sea and river transport in the absence of liquefied first gases by gas and gas 3 m and m.

In order to ensure safety and improve the efficiency of the process of removing the explosive gas from the tank.

The previous way; the first way; the first time; the first way; the removal of the air from the tank; the filling of the air with 153 interrupting i-ase.

Ihi (|) n | -. 1 image of the process diagram n1) Ggssneni from the ammonia tank with nitrogen; on f | and-. 2i1 B1 1 tc ammonia from

pts; on (1i; g. 3 scheme of the process of substitution by ammonia; in Fig. 4 - ii rinibi:; amms | tsein 1 ") with zodiac amnak; on fng. 5 g |) a (() for the calculation of the height of the H1NTNO Fig. 6 is the capacity diagram — the gas carrier of the gas carrier.

(l: 1; c () o () sunshestv. 1 is followed by the following statement. iOM.

In the tank 1, ammonia gas is removed through the pipe 2 due to the supply of nitrogen to the lower part1 of the pipe and the 4 pipes ((}) ig1) of nitrogen, which has the density of the displaced am.-; . (agility) of supplying nitrogen to the tank does not need to be at) pack | at1 articles 4) and basic elements. Nitrogen pumping was carried out in a quantity in a quantity that provides a layer of 0, () 7--0,15 reservoir heights. These clauses are valid for a capacitor with a narrowing in the upper or lower part {tar, truncated cone or nira-mida), when calculating the thickness of the layer necessary. They must take into account the greatest width in height of the tank Then io to pipeline 3 through pipe 4 into the tank noday dried air with sko) (.yearly, also does not violate the stratum (|) ikatsii. Until the detection of nitrogen at the outlet of the tank 1. In the future, the flow in; 5 A d; 1 capacity of the tank, increase to the limit,) at least 1 with the capacity of the ventilation equipment of the equipment and the pressure response of the tank. Blowing capacity 1: .yy: with a spirit of nodo.lzhatsya to achieve the concentration of ammonia, determined by its compliance with explosion safety or sanitary standards.

(e) standing of the atmosphere: in a container, in the projection of the explosion, the explosive gas varies, as n (.) is shown in FIG. 2. At the nerve attack ((|). 2 a) in the container there is a layer 5 of displaced ammonia and a layer 6 of nitrogen. On ethane {(rig. 2 b), an external air 7 begins to flow into the tank, displacing upward layers 6 and 5 of nitrogen and ammonia.

respectively. At this stage the boundary is

The nitrogen stream is diffused by the diffusion of gases, a thin layer 8 of an ammonia-nitrogen mixture and a layer 9 of a nitrogen-air mixture are formed on the surface of layer 6. In the third stage

 {fig. 2 c) the air supply continues, the upward movement of the nitrogen layer 6, the height of the layer

7 air increases, the height of the 5 am.miak layer decreases. The height of the boundary layers 8 and 9 increases. In the fourth stage (Fig. 2 g), the boundary of the protective layer reaches the upper surface of the tank, ammonia in the tank (layer 5) is virtually absent. Compared to the previous ethane, the height of layers 8 and 9 is increased. However, the contact of an explosive gas (ammonia) with air (c, 1; 7) is still absent, since these gases are separated by layers 6, 8 and 9, each H: J which is not explosive.

The displacement of air with an explosive gas (ammonia) is carried out. It becomes as shown in FIG. 3. The air in the tank 1 is removed through the nozzles 4, which dissolve in the tank and the pipeline 3 by supplying nitrogen to the upper part of the tank through the tube 2. The nitrogen density is somewhat lower than the air density. served in a tank at a rate that ensures the stratification of gases, in an amount sufficient to form a layer with a thickness of 0.07–0.15 in the height of the tank in the widest part of it.

Capacity 1 serves AM.Miak with a speed that also does not violate the gas estration, until the concentration of ammonia is detected at the outlet of tank 1, which is about 85% of the conditions of the operation of the units liquefied ia; ia,) 1% of gas tankers and coastal complexes. Further, the feed rate of the a.m.maia is increased to the extent determined by the technological capabilities of the equipment and the capacity of the vessel.

The state of the atmosphere in its capacity to replace air with explosive gas (ammonia) is changed, as shown in FIG. 4. On the first ethane (Fig. 4a) there is a layer 7 of displaced air and a layer of 6 nitrogen in the tank. At the second stage (Fig. 46), ammonia 5 begins to flow into the chamber, displacing downward from,: 1st 6 of nitrogen and air layer 7, which is iodine. The boundaries c; 1 6 of nitrogen are eroded by diffusion of gases; a thin layer 8 of an ammonia-nitrogen mixture and a layer 9 of a mixture of nitrogen air are formed on the surface of layer 6. In the third ethane (Fig. 4c), the supply of am.miak continues, the alternation downward of the nitrogen layer 6, the reduction of the height of the air layer 7. The height of the boundary layers 8 and 9 increases.

5, the fourth ethane (Fig. 4 g) of the j-paHiiua zanthite layer reaches the inlet openings of the nozzles 4, the air from the tank is almost B1,1 tressed. Compared to the previous stage, the thickness of the boundary layers 8 and 9 has increased, however, the formation of an air-ammonia mixture with an explosive concentration of the latter is excluded.

Example. Consider the process of removing ammonia from a K / 20140 m tank and a height of 5 m.

Nitrogen was taken as inert gas and dry air was taken as purge gas. The volumetric flow rate of nitrogen and dry air is 0.7. The height of the protective layer depends on the coefficients of mutual diffusion of the inert and the removed gas, their densities and the explosive limits of the gas to be removed in the mixture with air.

The values of mutual diffusion coefficients, ammonia - nitrogen 2,18-10; ammonia - air 2.27 nitrogen - oxygen - air 2.19-10

Since the coefficients of mutual diffusion of gases are very close, we take the calculations of one value equal to 2.2 10 m / s.

The scattering of gases in this replacement process is described by a partial differential equation.

 D bc p n

-;-20.

b26zbB

Where

X - current tank;

elevation coordinate

current coordinate is given;

time; dimensionless time;

concentrations of inert height TaiiKa and at its entrance, respectively;

reduced concentration;

inert gas bed speed;

Peclet criterion.

Calculations by the equation are performed by numerical methods for the boundary conditions: at the entrance to the tank with 1, at the output and for the values obtained on the basis of the initial data.

As the protective layer moves towards the exit from the tank (Figs. 2 and 4), ammonia and oxygen of the air are dispersed into and out of the protective layer due to diffusion.

The most dangerous situation will occur at the exit of the tank, the boundary of the protective layer and ammonia, since the greatest dispersion will be observed at this point. The distribution of ammonia vapors for this moment in time 6 1 is represented by curve I (Fig. 5). The oxygen distribution, provided that the height of the protective layer is 10% of the tank volume, or 0.1 N, will correspond to curve II (0 0.9).

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The lower explosive limit of ammonia-air mixture (15%) is marked by point A (curve I), which is located at the level of Z 0.88. All upper layers contain a greater amount of ammonia and, up to point C (30%), are in explosive limits in terms of ammonia content.

At the same time, it is known from the explosive diagram that an explosion is impossible in the presence of oxygen of less than 14% by volume in a mixture of nitrogen - oxygen - ammonia. At the level of point A, the oxygen content is determined by point B (curve II) and is calculated by the formula:

 from 21% -0, 6%, from where

. ,,

where с ,, „is the oxygen concentration in the air; cn is the limiting concentration.

It follows from the above calculations that the amount of oxygen in layers containing ammonia in explosive limits is insufficient for the occurrence of an explosive process and the height of the nitrogen protective layer is 0.1 N, or its volume is 10% of the tank volume. In the widest part of the tank, safe conditions for the removal of ammonia from the tank by air are provided.

The upper limit of the nitrogen layer height of 0.15 N is accepted by technical and economic considerations as sufficient relative to the optimum (0.1 N). A further increase in the nitrogen layer does not contradict the safety requirements of the process, but worsens its cost-effectiveness. The lower limit of the height of the layer of inert gas (nitrogen) 0.07 N was obtained on the basis of the calculation and the graph (see Fig. 5). From the above given concentration, 66, we get a point on curve II with abscissa z. The difference between the abscissa of the curve I and I gives the desired value of 0.07. Shown in FIG. 6, the tank — a gas carrier tank used in the calculations for the proposed method for removing gas from the tank, contains longitudinal and transverse partitions with perforations in the transverse partition to communicate the separated parts. These partitions, together with a non-continuous set, serve to increase the stiffness of the capacitance.

The proposed method in comparison with the known increases the efficiency rabot1 1 gas fleet; safety of navigation due to the exclusion of the possibility of the formation of explosive ammonia-air mixtures; reduces the amount of inert gas (e.g. nitrogen) required to remove an explosion hazard 1 aa nz capacity.

The application of the invention on the sea trap (- sport, for example, in the transport of ammonia by gas carriers, saves up to 90% of nitrogen for a single purge.

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Claims (1)

METHOD FOR REMOVING GAS FROM THE CAPACITY, including the displacement of explosive gas contained in the tank by supplying an inert gas of indifferent and different density and then dried air with a flow rate that ensures gas stratification, characterized in that, in order to increase safety and economical ty the process of removing explosive gas, inert gas is filled with 0.07-0.15 height of the tank, and the dried air is first supplied at a speed not exceeding the feed rate of the inert gas until inert gas gas at the outlet, after which the flow rate of dried air is increased. i h: 1 2 1 Ammonia 1 7/7 /////////// ; (0.07-0 / 5 / Air Fi g / SU, „, 1237579