SE464921B - SAVED TO RECOVER CHEMICALS FROM MASS DEVICES - Google Patents

Abstract

PURPOSE: To provide a method for recovering chemicals from a pulp spent liquor by supplying the pulp spent liquor to the reacting zone of a reactor while also supplying an outer thermal energy independent of the burning, mutually independently controlling the temperature and an oxygen potential at the reacting zone, and binding the whole alkali and sulfur in a molten phase. CONSTITUTION: A pulp spent liquor is supplied to a reacting zone of a reactor while also supplying an outer thermal energy independent of the burning. The temperature and the oxygen potential at the reacting zone are mutually independently controlled, and if necessary, a carbon material and/or an oxygen- containing gas is supplied thereto. The substantially whole alkali and sulfur the separated from the vapor phase and bound to a molten phase taken out from a discharging opening connected to the reactor. An organic part of the spent liquor is simultaneously taken out in a shape of a gas.

Description

464 921 10 15 20 25 30 burning. This means that both alkali and sulfur are to some extent released in the gas phase. A solution to this problem is indicated in the Swedish patent specification 83 02 245-0, which is based on dividing the entire recycling process into three steps. The process begins with a high-temperature step where sulfur is reduced and removed in the form of a melt at the same time as both alkali and organic material are gasified.

In a second step, alkali is condensed and simultaneously transforms into the desired form and finally a third step where the gas from the organic part is burned during simultaneous energy generation. The object of the above invention is thus to eliminate a subsequent work-up of alkali.

Another process for recycling cooking chemicals from pulp effluents is described in SE 72 04 304-5. The method is based on separating melt and gas in a pre-reactor.

In this process, one is completely dependent on the energy developed during the partial combustion in order to obtain a sufficiently high temperature. In practice, this causes great difficulties. If the partial combustion is not driven far enough, the temperature becomes too low to guarantee the flame retention, if the combustion is driven too far, both sulfur and alkali are largely emitted with outgoing gas.

The above-mentioned problems and difficulties are now solved in the manner initially described in that a temperature of 9000 to 1100 ° C is maintained in the reactor and that the oxygen potential is controlled by a regulated supply of the oxygen-containing gas and / or the carbonaceous material, whereby sulfur contained in the pulp effluent is reduced and substantially all of the alkali and sulfur are bound in a melt phase, which melt phase is separated from the gas phase.

According to the present invention, the recycling process 10 464 464 is divided into three separate steps. In the first step, the sulfur is reduced and withdrawn together with the inorganic part of the pulp liquor in a melting phase while simultaneously gasifying the organic part. This step is optimized to obtain an almost total separation of sulfur and alkali. In the second stage, the gas is burned during simultaneous energy generation. This can happen in many ways and for many purposes, but since it is completely separate from recycling, it can easily be sub-optimized. In the third step, a conventional reprocessing of alkali takes place to the desired shape.

Suitably the supplied gas consists of air and constitutes a carrier of extra heat energy supplied to the reactor.

Alternatively, the external energy can be supplied in the form of an energy-rich gas heated in a plasma generator.

Preferably, 95% to 100% of all alkali and sulfur are bound in a melt phase.

By the method according to the invention, similar to the concept instructed by SE 83 02 245-9, by directing the use of an energy additive independent of combustion, it has been possible to completely eliminate the previously mentioned problems which occur in a process. according to SE 72 04 304-5.

In the specific embodiment with plasma generator, it has unexpectedly been found that the reaction rate for the gasification of the thick liquor is very high, so that the reactor can be designed specifically to give maximum separation of the melt phase from the gas. The possibility of accurately regulating the temperature in the manner according to the invention further means that the composition of the cooking chemicals can be optimized with respect to the cooking process without the melting point melting point and flowability having to give rise to problems in the recovery step.

Example In an experimental equipment, a cylindrical reactor supplies 9 kg of thick liquor in front of a plasma generator placed tangentially on the cylinder. The plasma generator conducts 270 m3N of air per hour. An additional 120 m3N of air is added to the process through another tangential inlet.

The thick liquor has the following analysis: Na 20.5% of dry material s 4.52; - "- * H2 3,7% -" - 02 37% - "- C 34% -" - Cl 0,3% - "- 65% dry matter and calorimetric calorific value 13,89 MJ / kg TS.

The temperature in the reactor is regulated to 1000 ° C. To obtain this temperature, an energy addition of 1260 kW of electricity is required, partly to cover losses in the reaction vessel. By keeping the swirt number higher than 0.6, a Reynolds number higher than 18000 and choosing suitable dimensions on the reactor, a nearly 100% separation of the formed melt is obtained. 10 15 464 921 The amount of melt is 147.5 kg per hour, which is continuously lost during the experiments. The melt is analyzed to the following: NaOH Na2CO3 NaCl Na2S In addition saturation: CO 2, 1% 64.7% 0.7% 31.5%, 16.8% l3.0% 23.5% 46.6% a gas was obtained with the following dry gas aggregate Na 0.03% NaOH 0.04% NaCl 0.02% If the amount of air were to be increased in order to reduce the energy addition, Na2S would be largely oxidized, which is to be avoided at all costs.

Claims (4)

464 921 10 15 20 P a t e n t k r a v A method of recovering chemicals from pulp liquids while simultaneously using energy released during the process, wherein the pulp liquids are fed into a reaction zone included in a reactor while simultaneously supplying external, combustion-independent heat energy, whereby temperature and oxygen potential in the zone are controlled independently of each other by controlled supply of said heat energy, as well as supply of oxygen-containing gas and / or carbonaceous material, characterized in that a temperature of 9000 to 110 ° C is maintained in the reactor and that the oxygen potential is controlled by a regulated supply of the the oxygen-containing gas and / or the carbonaceous material, whereby the sulfur contained in the pulp effluent is reduced and substantially all the alkali and sulfur are bound in a melt phase, which melt phase is separated from the gas phase. 2. A method according to claim 1, characterized in that the supplied gas is air and constitutes a carrier of external heat energy supplied to the reactor. 3. A method according to claim 2, characterized in that the external energy is supplied in the form of an energy-rich gas heated in a plasma generator. 4. A method according to any one of claims 1-3, characterized in that 95 to 100% of all alkali and sulfur are bound in a melt phase.