DE1692827C - Process for obtaining heat from a mixture of air and water vapor from a dissolving device for chemical melts in soda plants - Google Patents

Description

For the extraction of chemicals and heat from wastewater in the chemical production of Pulp are mostly used with injection devices that are associated with a melting furnace include a boiler. After the liquid by evaporation to a suitable concentration it is injected into the furnace, where it is finally completely evaporated when it is brought into contact with the hot flame gases, the residue settles ignite and burn. The chemicals are usually obtained in the form of a melt, which is withdrawn from the lower part of the device. The heat from the flame gases is absorbed by the water-cooled walls of the melting furnace, the pipe system and the superheater of the boiler recorded.

From the extraction plant, the hot melt from the boiler is passed into the dissolving device, into which an aqueous, weak solution for the production of the so-called "green liquid" is introduced. The weak solution is usually introduced into the ventilator at a temperature of about 65 ° C and, while the melt is dissolved in water, a certain amount of water evaporates, which is the difference between the amount of heat required to dissolve the melt and that required to cool the i / climelze corresponds to the amount of heat released at the solution temperature on the one hand and the amount of heat required to heat the weak solution to the temperature in the solution device on the other hand.

Devices have already been designed to extract some of the heat from the air-water vapor mixture that escaped from the dissolving device, in which device the air-water vapor mixture is passed through a condenser or a washing device for the production of hot water.

* r is directed and then the non -condensed part escapes into the atmosphere.

The present invention is intended to utilize the entire heat, in that the air-steam mixture, which is used for the production of hot

»5 'vnssct serving capacitor or the dk - .. ~ ..j. w-u -.- (.!., no leaves, is fed back into the dissolving device instead of being vented into the atmosphere as described above

Low-water vapor air-vapor mixture, after it has passed the water heater, fed back into the dissolving device, in which it is again enriched with water vapor, which is condensed during the subsequent Durohleitens by the part that heats the water. In this way, practically 10O ¹ O of all the heat that has developed in the solution can be used to produce hot water. This fact is of enormous economic importance, since the wet temperature of the air-steam mixture from the dissolving device can be maintained up to 85 ° C. without difficulties arising due to the loss of steam. Due to the high wet temperature, it is possible to produce hot water with a temperature of 75 C. As a result, this heat can be used not only in factories for the production of bleached pulp, in which hot water at this temperature is required for bleaching, but also in factories for the manufacture of unbleached pulp, since the heat from the melt in this case is used to heat the Make-up water can be used in the production of hot water in the factory's hot water system.

The method according to the invention also provides further advantages. In conventional devices, relatively large amounts of air penetrate into the system, especially into the openings in the channels for the melt. This air causes oxidation of the melt to a certain extent, as a result of which part of the sodium sulphide is converted into sodium thiosulphate; the oxidation can even proceed to the formation of sodium sulphate. Sodium thiosulfate is undesirable in the melt connection because this connection is reinforced in the prepared from the melt "white liquid" corrosion in the steam and washing device at present. The sodium sulfate is also undesirable because it is an unnecessary fiber which increases the chemical losses as it passes through the soda and caustic plant and the washer and evaporator of the chemical pulp mill.

According to the invention, the air-vapor mixture is made the hot water heater fed back into the dissolving device, whereby the oxygen in the air in the gas mixture is gradually consumed and

an inert, circulating gas is produced so that the sulfide cannot be oxidized. With the ... new facility _? A small part of the air vapor can also be removed from the system after it has passed the water-regulating part of the W, and when it is blown into the exercise device, it can be replaced by flame gas, which already has a very low oxygen pressure .ut, so that the oxidation conditions are improved especially at the beginning. The gas supplied in this way is preferably withdrawn after it has passed through the precipitator or other gas cleaning system. so that the gas is as free of dust as possible to »avoid clogging.

Further details of the invention emerge

-,., «The following description of the

example shown in the illustration. U.e drawing

tion shows a device for the extraction of

Heat from an air-vapor mixture in the lo-

solution device. From the extraction system 1

an outflow or a channel 2 extends through

«■ elche the melt after the incineration of the

"Black liquid" in a dissolving device 3

is fed through special hoods 4. If

it is necessary, several grooves 2

be provided. The extractor hoods are intended to

flow to the solution device 3 to a minimum

reduce. The air-water vapor mixture from the

Solution device is through a channel 5 to

a hot water heater 6, which in this case as

a surface capacitor is constructed,

leave. Cold water is introduced through a pipe 7

and after it has been heated, it is drained through a pipe 8

sen. The amount of water is adjusted to the desired temperature

Temperature controlled accordingly by a valve 9. the

uncondensed part of the air-vapor mixture

is removed from the hot water heater 6 and

flows through a duct 10 to a fan 11.

The performance of the fan is controlled by a

tion area 12 adapted to a ^^ 13 d, e their impulses ^ rature in the channel 5 received in the eme supply 14 e.ngebaut .st Ausdem. wi rd the Lui «^ P ^f according to the back through which flows into the hood 4 at aer tion. _Men "s from

If exceptionally large quantities

Melt * ™ * ™haben% f £ ^ £ 2 * ^ would result from the lower part ^ "J ^ toSdensalioo in greater se.n than d, e amount ^d * * ^u '* ° ™ ^{C of} _{the from} the hot water heater 6 b ^ umm ^ ^ t α . ^ w.tschafthchen point of view from sent ?

Dimensions hai ^ J «J? F ™" *, " _on one . ₅ dungskanal! 16 with a shut-off valve I

Channel ^ 5 connected du _r ch ^ hes ^ ven ^^^ ^

aes ^LUll - ^ ¹ "^""^'; - _{restriction of} the required

small room in the an ^ w d em)

*, Applies to at Erwa; _{to D} ^ ⁿ ^ f _{tei ng}

ae

cause

hch less ^^^^ _{the oxidation of} the man hold it for: extremely wicnuss <* _der

_a5 Melt to be inhibited and inhibited; g

Soda plant for the bronze "little" crs ^ llung p_

nut emem WWj ^ * ™haben ^ S _euerventiI 20 position through the channel W with the _{corresponding} end

zugetuhrt we ^{would recommend} _"D J ^{O d} _f" ^ _S ^ che "from the plant

Amount of the Luf -D ^a mpfgem ^ c "es _a

by _f den Karia 21 ab £ s «.r '^. _one

Steam ejector 18 and the «gekt _kan ^.

common ^ AuslaO ^ ^a ^^ ^k ™ ^ _{extends towards} .

up: ta ^ derr ^ ^Dac ^ ™ _n f _standing con-

The m the warm ^w asMrcrh «r ^ em ^

densat will ^ ^f J ^e . _n ^ _e ^a S _UI ^ orrilhtung 3 through a drain pipe into the solution s _air

1 sheet of drawings

Claims (4)

1 692 7 3 claims: 1. Process for the extraction of heat from an air-water vapor mixture from a solution device for chemical melts in soda: systems for the chemical production of pulp, which have a hot water heater, e.g. B. a condenser or a washing device to summarizes, characterized in that the air-vapor mixture is completely or partially returned to the dissolving device after passing through the hot water heater. 2. The method according to claim t, characterized in that part of the air-Dampfge mixture after the uurcnieuen uwtu ucu w ^, ... water heated, is removed from the system, while a gas with a low oxygen content, z. B. Flame gases, from the Sodaanla ^ c / ur chemical production of pulp, along with the rest of the air-vapor mixture from the Hot water heater is fed into the solution \ orrichtunu. 3. The method according to claim 1 and 2, characterized in that part of the air-steam mixture after passing through the hot water heater, if necessary, out of the system is removed by means of an ejector. 4. Procedure, according to /.nspru* a I and 2, thereby characterized that eiij part of the air-vapor mixture if necessary, before passing through the hot water heater from the system is removed by means of an ejector.