Sophisticated process of maintenance in temperature of engines.

i-the invention relates to maintaining temperature re - j-j-actors where an exothermic reaction occurs. More partieu -! ! as particularly, it applies to large reactors, the j ' whose Tubulo example is the reactor for 1 * attaque I-phosphate (natural in the manufacture of wet process phosphoric acid. ;

Since it is known that in this technique a rigorous holding; the temperature is required. This is provided in the existing er technij, either by a circulation of a portion of the

! reaction slurry, in a cooler vacuum: this is what is described in French patents 1,543 753, or

1,323 087 and 1,534 672, or by evacuating the reactor, this is what is described in French patents 1,506 968 and 1,506 969, or 1,550 127 and 2,059 670.

The BN because of technical problems, of for energy conservation, has been selected third solution which provides cooling of such reactors by air circulation ATs; mospheric to the surface of the reaction medium.

>A definition of this solution in the work_| of NV bandy "Phosphoric acid is also" DE. 1968 e. 227 to 231 v. 1

|hand. THE I.

|this avoids the disadvantages of first

¹ solution of RO above, such as: scalings, need periodic washing, creating a temperature gradient unfavorable to good crystallization; those of the second solution above, such as: need for a tight sealing which

|causes problems of building, or importance of

Y plus in larger installations due to the content of condensable gaseous compounds.

But on the contrary, the cooling air, which is

! water vapor laden, carbon dioxide, fluorine andc... as described w 745 of the spillway NV bandy above specific, is; treated before it is discharged to the atmosphere. The processing requests; investments in DS to large flows and also to the necessity; of a thorough purification, which may impose more appliances,, cause of energy expenditure, by rejecting gas even

: hot, loss of potency.

The present invention permits the treatment the JDE cooling air.

the I

It was found that a substantial portion of the air used to drive steam, could be reused.

Thus decreased significantly, the volume of gas processed before it is discharged to the atmosphere, and hence investment and energy expenditures.

The method of the invention allows continual, a reactor through air circulation to the surface of the reaction medium for the practice and vapor removal.

According to the invention, a loop is formed of reciculation comprising passing air over the engine, whereby the air reaches a temperature near the temperature of the reaction and becomes saturated with steam, then, treated air laden with vapor in a system for removing the vapor out of circulation and is returned to at least a portion of the treated air to the surface of the reactor, where it is charged again steam, and rejects the remainder air portion to the atmosphere.

More introduced treated air to the surface of the reactor in the adjoining to a fresh air supply, generally fed in from the atmosphere, to complete the required delivery rate.

Treating the remainder air portion by means of a scrubbing and cooling before it is discharged to the atmosphere.

Carried out removing the vapor out of circulation by any method known per se.

In a preferred embodiment of the invention, carried out removing the vapor by means of a condenser. The condenser has the second function of cooling the exhaust air. The air leaving the condenser is saturated but at a temperature significantly lower than the temperature of the gas leaving the reactor; it thus contains much less steam and is capable of charging steam pass over the reactor, the amount of steam which it can load is fixed by the saturation temperature of the reactor, is in will see further from an example.

Divide the air exiting the condenser. The quality removed for recycling is higher that the condenser is more efficient. The respective flow rates adjusted by any means known per se.

It is normally preferred to implement, especially in the manufacture phosphoric, a condenser to mixture sprayed water, of any known type, cocurrent or countercurrent. Used is preferably a counter-current apparatus.

Is selected with advantage a column cyclonic vacuum without reciculation liquid.

Removed together the water sprinkler and the condensed vapor.

The condenser is fed selected by water. The flow rate of irrigation water and its temperature are factors that affect the efficiency of the condenser, with the explicit understanding that the temperature low and high flow rates are favorable to condensation.

The air exiting the reactor contains condensable compounds; this is how gasses produced by the decomposition of phosphate ores often contain carbon dioxide from the gangue, in variable amount according to the origin of the phosphate. This prevents the accumulation of these compounds by the rejection to the atmosphere a portion of the cooling air.

The majority of gaseous impurities from phosphate ores are those which are fluorinated compounds. In a condenser the compounds are contacted ccntact water, and therefore, are largely solubilized and set apart in the wash solution. The condenser thus has a third function which is a cleaning function.

The rate of recycling air thus also depends on the content of condensable compounds and fluorinated compounds present in the gas mixture emitted by the etch reactor phosphoric. It also depends on the efficiency of the condenser as has been said, and also of the possibility to have enough cold water.

As appropriate available water is provided by: water spreading (about various NV Sipione, already cited, gives a specification P 727 to 731)" river water, or in general, any water that may be cooled to hand and returned

1' facility.

In all cases, removing the vapor by condensation and/or elbow, is accompanied by a gas purification, the soluble compounds being partially removed with the condensed water.

The gas leaving the condenser and non-racirculés are rejected into the atmosphere after washing to by a further purification, meet prevailing standards.

The washing is carried out in any apparatus known per se, as a packed column, or a cyclonic vacuum column supplied to water with or without recycling. The gas out of the final washing take advantage with further cooling.

The water exiting the condenser end of the scrubber and are used in another part of the plant with benefits described below. The impurities solubilized or driven do not produce any disadvantages.

A phosphoric acid plant comprises, in a conventional manner, a reactor or reaction system driver and filtration and washing system " generally under vacuum.

In such an installation the water required is constituted by:

- water called "process", used washing methodical cake calcium sulfate; it is known that it " should preferably, using hot water,

- by water repulp gypsum,

- by the water from the condenser to the vacuum pump of the filter,

- by water cooling apparatuses (fan, vacuum pump of the filter).

The trial this water required in three parts:

a) recirculating hot water "process".

h) recirculated water for the repulping the condenser and the vacuum pump of the filter.

c) clean water for cooling apparatuses.

the method of the invention provides especially water from the condenser is heated by heat exchange with hot gas from the pickle tank. It is advantageous to use the water as "process" a washing of the cake.

Fig. 1 is shown schematically, the method

of the invention.

A system is cooled. reaction 1, 2 by air circulation, which to the outlet of the reactor, is loaded with steam. The stream 2, set in motion by an apparatus not shown, such as for example a fan, 3 passes through an apparatus for separating a portion of the vapor, which exits 4 and may optionally be used in another part not shown of the installation. A portion of the flow leaving the apparatus 2 3, containing a small amount of steam, is returned to the reactor 1. The remaining part 5 passes through a scrubbing system 6 before release to the atmosphere 7.

The complement of air cooling is achieved 8 or 8 ', the settings of the respective flow rates are via any known means, and schematized here in 9, 9', 10 and 11.

Carried out removing the vapor out of circulation by any means known per se, such as the contacting air laden with vapor with concentrated sulfuric acid.

fine particular, when implementing the process of the invention to an etching system phosphoric, sulfuric acid is used for by the etchant 3 in an apparatus such as a column dryer followed by refrigerant. The refrigerant discharges the calories dilution and may serve as a heat source. Introduced in known manner, outgoing sulfuric acid diluted, leading to the reaction medium.

In the preferred embodiment where the removed steam condensation, the apparatus 3 is a countercurrent condenser. One advantage is that the calories formerly lost are recovered as hot process, without additional expenditure of calories.

The method of the invention can enable an additional advantage: when the need of hot water, is carried out alternatively the installation shown in Figure 2. Is added to the installation schematized in Figure 1, to the outlet of the reactor 1, and before the condenser 3" a preliminary processing apparatus 12, with an outlet 13.

This increases the heat exchanges and/or materials by an improvement of the surface and the gas-liquid contact time. The processing apparatus 12 is supplied with water by 14. The water collected in 13 is very hot, it is advantageously usable as process water. In addition, the advantage that, in this variant, avoid driving BMPs ^ vesicular form; these are returned to the reactor via the washing methodical countercurrently over the filter.

It is advantageous to select as preliminary processing apparatus the device described in the French patent application no. 79/22082, as it will be in the examples hereinafter. The advantage that for a small investment increases the efficiency of the assembly.

In the general embodiment of the invention, was measured the effectiveness of different types of condensers countercurrent and cocurrent.

A gas mixture is treated to 68®C. surmounting a reactor, due to flow of 1,000 meters ^ / hr water 32°!

Temperature air exiting gas volume output to 68 °c rejected

a) countercurrent 44° 0,363 000 rNs ^ / hr 27,700

b) 47 °c 390,000 current against the m³ 30,500 HAS

c) cocurrent 56^Ô The m ^ has 48,000 557,000 C.

Is selected advantageously a countercurrent wash through the apparatus of the type described in French Patent no. 75/33,658, (publish no. 2,330 435) in which does not liquid recycled watering. This gives the advantages of contact countercurrent, low load loss, contamination limited, by the empty column, sprayers to large diameter, to the area of dévésiculage.

Is selected to perform second washing or absorption, any apparatus known per se, with or without liquid recirculation and for a number of transfer units adequate.

It can use a packed column, or column cyclonic vacuum associated with a venturi, such as the French Patent no. 77/20097, (publish no. 2,395 771).

The investment of this second washing is significantly decreased compared to known technology; thus, for example that to fulfill the same effluent standards, utilizing a set of known apparatuses having a number of transfer units of 5.22, whereas according to the invention, the same result is a significantly lower rate, (which it will be farther from one example) and with a single apparatus having a number of transfer units of 3.14. This second apparatus, further, just the industrial water and not reactive.

1 fiXfiLPLfi

An etching system is cooled phosphoric

fig. 3 schematically type represented " by circulating a flow 31 of 363,000 KVM to the surface of a reaction vessel provided with means for agitating 5, 32, 33 in the incoming air is to 32 °c, at the outlet of the reaction vessel 32 it is to 68 °c. Washing the plant. by water at 32 °c from surface spreading introduced in 34 in a condenser 35. Air exiting the condenser 36 is to 44 °c. 37 Is tapped a rate corresponding to 90# in

10 mass and in dry air, of the total, and joining the air flow

33 entering the facility. The remaining flow 38" is about 10# 39 is washed by water from in this case the surface of the spreading, exits the tunnel in 40 to 32 °c at a rate of 30,000 M.^ / hr about. Adjusting the respective flow rates 33, 37, and ' 5, 38 is accomplished through the use of registers 41, 12 and 43 ·

The energy required for the two washes of 363,000 mVh

150 mm to 30,000 fi and C. the m ^ / hr 400 mm to c-fi is of about 250 kw, joining the waters of 44 and 45 2 washes, connecting back by 46 at filter not shown, they are about to 60 °c.

20 the bis 1 fiXfiMPLfi

To evaluate energy expended compared the example 1 with a facility known comprising in series two scrubbers^; the venturi that process the total flow of the gas cooler, first: to the water and then soda.

29 Gas exiting to the atmosphere is at 40 and 50 degrees Celsius. Must be investment needed treatment of 300,000 rNs ^ / hr to 560 mm C. IF, and energy 63o CA.

In addition, web air volume exhausted is 10 times higher than that of the example 1; its temperature is higher

30 for the same effluent standards to 10 g of fluorine per ton of BMPs ^ manufactured.

Compares the absorption of between the two preceding installations, it is considered that in both cases, the first washing is carried out in a column cyclonic without crafted 35i; clage having a number of transfer unit 1.5 taken for the second washing n U-I of 5.22, in the case of the example 1 of bis; however, in the method of the invention it is sufficient, in I the second washing of an n Û 3.14 T, the investments are the j. less, and there is not consuming soda.

2 SIÆFLS

By measuring the amount of steam entrained in the exem - ^ IEP 1 according to the invention; recirculated air flow to 44 °c

OOO>* saturated 249 still supports the m 15,400 kg water uncondensed, is the full flow of the atmospheric air to 32 °c and 90 $humidity rate of 25,000 KVM carrying 760 kg of water: to the vessel outlet, air door 58,950 kg of water it is to 68 °c, to 90fô moisture and a rate/hr>363,000 w ^ and served to evaporate 42,790 kg of water from the tank,

3 JMSPLÆ

Carrying out the variant of the method of the invention comprising a pre-treatment. The treated gas overcoming a pickle tank phosphoric, a rate of 170,000 ^ the m/hr.

These gasses are to 65 °c saturated. They are sent by a fan in a sanitizer consisting of a colonist_I two-stage washing spray.

To have a water "process" very hot and yield by a washing device according to the French request 79/22082, with a flow rate of 150 KVM to 30 °c for watering.

Collected wash water to about 60 °c, the gas exiting the column are to 40 and 45 °C., the gas exiting the column 40 and 45° are to, they contain less than 40 kg/j of fluorine for Me producing 650 t/j of PgOç.

The method of the invention is applied advantageously in the manufacture phosphoric. Carried out particularly cost effective production by the method at calcium sulfate dihydrate or gypsum, with repulp waste gypsum, which is fed to a spreading where it settles and wherein chilled water is reused.

The invention has other applications industri_I natural in any system in response to air cooling.