RU2761910C1 - Method for lime regeneration in the production of sulfate cellulose - Google Patents

Abstract

FIELD: cellulose industry.

SUBSTANCE: present invention relates to the field of cellulose production and can be used for lime regeneration in the production of sulfate cellulose. The task is achieved by the fact that in the lime regeneration method for the production of sulfate cellulose, which includes cooking cellulose, burning black liquor, dissolving the melt to form green liquor, lime quenching and sludge washing, with a humidity of 50-55%, characterized in that no more than 20% of the black liquor obtained after cooking cellulose is precipitated by flue gases at a pressure of 3-7 atm from a lime-generating furnace to pH 7-8 at a temperature of 20-40°C, the resulting lignin-carbohydrate complex, consisting of a mixture of organic substances of phenolic nature with an ash content of 1-1.5%, mixed with sludge, humidity is 50-55%, at a ratio of 2:1 before feeding into the lime kiln, and the resulting lignin-carbohydrate complex is mixed with crushed sawdust before processing it into wood and charcoal briquettes fed into the lime kiln as fuel to replace fuel oil by 75-80%.

EFFECT: increase in the productivity of lime regeneration due to additional processing of black liquor formed during the pulp cooking process by treating with flue gases of the limekiln to obtain a lignin-carbohydrate complex (LCC) used as biofuel to increase the caloric content of fuel in the limekiln while reducing fuel oil and recycling production waste.

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Description

The present invention relates to the field of cellulose production and can be used for lime regeneration in the production of sulfate cellulose.

A known method of processing black liquor of sulfate cellulose production [Yu.N. Nepenin. Sulphate Pulp Manufacturing Volume II 2nd Edition. - 1990 - S. 511].

Black liquor is a solution obtained after pulping, which is a mixture of 60-70% organic and 30-40% mineral substances.

The essence of the method lies in the fact that wood waste with a moisture content of about 55% is used as a fuel for burning sludge in a lime regeneration kiln (LCR), which is directly mixed with limestone sludge.

The method makes it possible to use wood waste generated at pulp and paper mills. In addition, there is a partial, 75-80% replacement of fuel oil with environmentally friendly fuel. At the same time, the productivity of the furnace does not decrease and the quality of the burnt lime does not deteriorate.

The disadvantages of the described method include:

- the use of raw wood waste, which has a low calorie content, high humidity and the presence, including solid waste;

- the need for additional sorting and preparation for the use of wood waste.

The technical task is to eliminate these disadvantages, namely, to increase the productivity of lime regeneration due to additional processing of black liquor formed during pulping by processing with flue gases IRP to obtain a ligno-carbohydrate complex (LCC) used as biofuel to increase the calorific value of the fuel in IRP while reducing fuel oil and utilizing production waste.

The task is achieved by the fact that in the method of lime regeneration when obtaining sulphate cellulose, including pulping, burning black liquor, dissolving melt with the formation of green liquor, slaking lime, and no more than 20% of black liquor obtained after cooking cellulose is precipitated with flue gases under pressure of 3-7 atm from a lime recovery furnace to pH 7-8 at a temperature of 20-40 ° C, the resulting ligno-carbohydrate complex, consisting of a mixture of organic substances of phenolic nature with an ash content of 1-1.5%, is mixed with sludge, humidity 50-55% , at a ratio of 2: 1, before feeding to the lime regeneration furnace, and also mix the resulting ligno-carbohydrate complex with crushed sawdust before processing them into wood and charcoal briquettes, which are fed to the lime regeneration furnace as fuel to replace fuel oil by 75-80%.

A significant difference of the claimed method is an inextricable set of actions set forth in the claims, which allows to achieve the technical result, which consists in additional processing of black liquor formed in the process of pulping by processing with flue gases IRP to obtain onions used as biofuel to increase the calorific value of the fuel in IRP while reducing fuel oil and utilizing production waste.

Examples of implementation of the method:

Example 1

After cooking 1 ton of cellulose, the resulting black liquor, 1.085 tons, partially, 90%, is burned, a dissolved melt is obtained with the formation of green liquor, and it is sent for lime slaking, and partially, 10%, the ligno-carbohydrate complex is precipitated with flue gases from the IRP at a pressure of 3- 7 atm, which are sucked off by a smoke exhauster from the loading end at a temperature of 100 ° C, followed by compression and cooling to 20-40 ° C. The obtained onion, consisting of a mixture of organic substances of phenolic nature with an ash content of 1-1.5%, with a pH of 7-8 is mixed with sludge, at a ratio of 2: 1 (4 tons of onions: 2 tons of sludge), before being fed to the IRP, for dehydration and flushing. The resulting sludge with a moisture content of 50-55% is fed by a screw conveyor. As the resulting sludge moves in the IRP, it heats up and ignites at a temperature of 200 ° C, and the regenerated lime in the form of pellets comes out after the IRP from the discharge end and is fed into the cooling drum by the feeder. From the cold end of the furnace through a nozzle, fuel oil is supplied for combustion and charcoal briquettes crushed to a pulverized state.

The achieved effect is high efficiency of the process, transition to renewable energy sources, improvement of environmental safety of production. Providing the IRP with well-dewatered sludge with a sodium oxide content of less than 1%, due to the use of onions, which are precipitated by flue gases from the IRP to pH 7-8. This, in turn, reduces the formation of rings on the walls of the IRP. This results in a well-granulated sludge, which contributes to a uniform firing with a low dust content. The use of onions and crushed charcoal briquettes makes it possible to replace fuel oil by 75-80%.

Example 2

After cooking 1 ton of cellulose, 1.085 ton of the obtained black liquor is partially, 85%, burned, a dissolved melt is obtained with the formation of green liquor, and it is sent for lime slaking, and partially, partially, 15%, the ligno-carbohydrate complex is precipitated with flue gases from the IRP, at a pressure of 3-7 atm, which are sucked off by a smoke exhauster from the loading end at a temperature of 100 ° C, followed by compression and cooling to 20-40 ° C. The obtained onion, consisting of a mixture of organic substances of phenolic nature with an ash content of 1-1.5%, with a pH of 7-8, is mixed with sludge, at a ratio of 2: 1 (4 tons of onions: 2 tons of sludge), before being fed to the IRP, for dehydration and flushing. The resulting sludge with a moisture content of 50-55% is fed by a screw conveyor. As the obtained sludge moves in the IRP, it heats up and ignites at a temperature of 200 ° C, and the reclaimed lime in the form of pellets comes out after the IRP from the discharge end and is dosed into the cooling drum by the feeder. From the opposite end of the furnace through a nozzle, fuel oil is supplied for combustion and charcoal briquettes crushed to a pulverized state.

The achieved effect is a high efficiency of the process, a transition to renewable energy sources, the ability to reduce the amount of fuel oil supplied to the IRP, since the LUK supplied with the sludge is capable of heating the sludge to 1200 ° C, which leads to an improvement in the environmental safety of production. The use of onions and crushed charcoal briquettes makes it possible to replace fuel oil by 75-80%.

Example 3

After cooking 1 ton of cellulose, 1.085 ton of the obtained black liquor is partially, 80%, burned, a dissolved melt is obtained with the formation of green liquor, and it is sent for lime slaking, and partially, 20%, the ligno-carbohydrate complex is precipitated with flue gases from the IRP, under pressure 3-7 atm, which are sucked off by a smoke exhauster from the loading end at a temperature of 100 ° C, followed by compression and cooling to 20-40 ° C. The obtained onion, consisting of a mixture of organic substances of phenolic nature with an ash content of 1-1.5%, with a pH of 7-8, is mixed with sludge, at a ratio of 2: 1 (4 tons of onions: 2 tons of sludge), before being fed to the IRP, for dehydration and flushing. The resulting sludge with a moisture content of 50-55% is fed by a screw conveyor. As the obtained sludge moves in the IRP, it heats up and ignites at a temperature of 200 ° C, and the reclaimed lime in the form of pellets comes out after the IRP from the discharge end and is dosed into the cooling drum by the feeder. From the opposite end of the furnace through a nozzle, fuel oil is supplied for combustion and charcoal briquettes crushed to a pulverized state.

The achieved effect is high efficiency of the process, transition to renewable energy sources, improvement of environmental safety of production. Providing the IRP with well-dewatered sludge with a sodium oxide content of less than 1%, due to the use of onions, which are precipitated by flue gases from the IRP to pH 7-8. This, in turn, reduces the formation of rings on the walls of the IRP. This results in a well-granulated slurry, which contributes to an even firing with a low dust content.

Thus, the combination of actions allows you to increase the effect of lime regeneration by increasing the calorific value of the process, the use of excess black liquor as a replacement for fossil fuels. Mixing onions with sludge in a ratio of 2: 1 makes it possible to replace fuel oil with crushed charcoal briquettes, the heat of combustion of which is 34-35 MJ / kg. In this case, the heat of combustion does not decrease, it is 40 MJ / kg, while the heat of combustion of LUK is 25-27 MJ / kg, and that of fuel oil is 39-41 MJ / kg.

The implementation of the proposed method allows:

- to reduce production waste through the use of LUK as a biofuel and simplification of the instrumental and technological scheme, during the precipitation of LUK by flue gases from the IRP;

- to reduce the "carbon footprint" from production by partially replacing fossil fuels with biofuels;

- to make a closed production, since the exhaust gases can be used for the deposition of onions.

Claims (1)

A method of lime regeneration in the production of sulphate cellulose, including pulping, burning black liquor, dissolving melt with the formation of green liquor, slaking lime, characterized in that no more than 20% of black liquor obtained after pulping is precipitated with flue gases at a pressure of 3-7 atm from a lime recovery furnace to pH 7-8 at a temperature of 20-40 ° C, the resulting ligno-carbohydrate complex, consisting of a mixture of organic substances of phenolic nature with an ash content of 1-1.5%, is mixed with sludge, humidity 50-55%, at a ratio of 2 : 1 before feeding to the lime regeneration kiln, and also mix the resulting ligno-carbohydrate complex with crushed sawdust before processing them into wood and charcoal briquettes, fed to the lime regeneration kiln as fuel to replace fuel oil by 75-80%.