A process for water washing of a recovery boiler

Abstract

The present application relates to a kind of alkali recovery furnace water washing process, the process includes the following steps: step one: after alkali recovery furnace shutdown, open disc valve, plug valve and hearth furnace door, carry out hearth cooling;Step two: after cold furnace, washing water is pumped to alkali recovery furnace soot blower by feed water pump, by soot blower flushes the surface of heat exchange element, and the slagging and coking material therein is cleaned up completely;Washing waste water is recycled by dissolving tank and venting tank;Step three: after washing furnace, by hot air into air supply system, air draft system exhaust, dry hearth and heat exchange element;Step four: after drying furnace, in chute pouring castable, repair the part that is washed away by combustion melt and washing water, a kind of alkali recovery furnace water washing process designed by the present application can conveniently clean ash and remove coke with high efficiency, good effect, can effectively guarantee the cleanliness of heat exchange element, improve alkali recovery furnace operating efficiency.

Description

Technical Field

[0001] This invention relates to the field of ash removal and coking in alkali recovery furnaces, and particularly to a water washing process for alkali recovery furnaces. Background Technology

[0002] Black liquor is waste liquid produced by the alkaline pulping process in the papermaking industry. Currently, the mature technology for treating black liquor is combustion. The main principle is that the black liquor extracted after pulping is concentrated to a solids concentration of over 70% through evaporation before being sent to the alkali recovery furnace for combustion. During combustion, fly ash is produced. Fly ash consists of tiny combustion particles or droplets carried by the combustion flue gas as it leaves the furnace, primarily composed of sodium carbonate and sodium sulfide. When fly ash particles come into contact with cooler heat transfer surfaces, they solidify and adhere to the surface, accumulating in the windward direction of the heat transfer tubes and depositing near the furnace to form ash accumulation. Ash accumulation often causes blockage of the flue gas passages, forcing the recovery boiler to reduce its combustion rate or even shut down for cleaning. Therefore, after the alkali recovery furnace has been running for a period of time, it needs to be shut down for ash removal and descaling to ensure its efficiency and safety. Shutdown ash removal and descaling is usually done manually by manually inserting the furnace, which results in poor cleaning efficiency, significant safety hazards, damage to heat exchange elements, and long cleaning times.

[0003] The main components of fly ash are sodium carbonate and sodium sulfide. It has large particles and is easily soluble in water. Taking advantage of this property, hot water can be used to dissolve and clean the ash accumulated on heat exchange elements such as economizers, superheaters and water-cooled walls. Summary of the Invention

[0004] To address the problems of poor cleaning effect, significant safety hazards, damage to heat exchange elements, and long cleaning time associated with existing manual ash and coke removal processes, this invention provides a water washing process for alkali recovery furnaces, which offers high ash and coke removal efficiency and excellent results.

[0005] The technical solution of the present invention is as follows:

[0006] A water washing process for an alkali recovery furnace, wherein the alkali recovery furnace comprises a water-cooled wall, a superheater, an evaporator tube panel, an economizer, a chute, a dissolving tank, an alkali ash tank, a venting tank, and a soot blower, etc. The soot blower of the alkali recovery furnace can be connected to a water supply pipeline, and the furnace washing water is pumped to the soot blower by a water supply pump. The furnace chamber of the alkali recovery furnace is connected to an electrostatic precipitator, which is connected to a chimney through a flue. A disc valve, an induced draft fan, and a gate valve are installed on the flue. The furnace bottom of the alkali recovery furnace is connected to the dissolving tank through a chute. The ash hopper of the economizer and the dust outlet of the electrostatic precipitator are connected to the alkali ash tank, and the alkali ash tank is connected to the venting tank. The process includes the following steps:

[0007] Step 1: After the alkali recovery furnace is shut down, open the disc valve, the slide valve, and the furnace door to cool the furnace.

[0008] Step 2: After Step 1 is completed, the boiler washing water is pumped by the feed water pump to the soot blower of the alkali recovery furnace. The soot blower washes the surface of the heat exchange elements, cleaning the slag and coking material on the surface of the heat exchange elements. The boiler washing wastewater is recycled through the dissolution tank and the venting tank.

[0009] Step 3: After step 2 is completed, hot air is introduced through the air supply system and exhaust air through the induced draft system to dry the furnace and heat exchange elements;

[0010] Step 4: After step 3 is completed, pour castable into the chute to repair the parts that have been washed away by the combustion molten material and the furnace washing water.

[0011] Preferably, in step one, the furnace cooling is achieved by natural draft from the chimney, reducing the furnace temperature to 80°C, and the furnace cooling time is 36 hours under the condition that the furnace temperature is 80°C.

[0012] Preferably, in step two, the furnace washing water is demineralized water with a temperature of 80°C, a flow rate of 100 t / h, a washing pressure of 1.6 MPa, a washing time of 5 min for each sootblower, and a washing sequence from the tail of the furnace to the head of the furnace, from bottom to top.

[0013] Preferably, in step two, the heat exchange elements include an economizer, a superheater, and a water-cooled wall.

[0014] Preferably, in step three, the hot air comes from the air supply system of the alkali recovery furnace, the hot air temperature is 120℃, the exhaust air is provided by the induced draft system, the furnace negative pressure is controlled at 20Pa, and the furnace drying time is 16 hours.

[0015] Preferably, in step three, the air supply system is a multi-layer air supply system consisting of primary air, secondary air and tertiary air, and the induced draft system consists of two induced draft fans.

[0016] Preferably, in step four, the main component of the castable is chromite sand, and the curing time is 2 days.

[0017] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0018] (1) The present invention provides a water washing process for alkali recovery furnace, which has high ash removal and coke removal efficiency and good effect, can effectively ensure the cleanliness of heat exchange elements, improve the operating efficiency of alkali recovery furnace, and increase the steam production of alkali recovery furnace and the power generation of steam turbine;

[0019] (2) In this embodiment of the invention, no personnel are required to enter the furnace, there are no personnel safety hazards, and the cleaning time is short, which can effectively reduce downtime;

[0020] (3) In the embodiments of the present invention, the furnace washing pressure is designed to be lower than the steam blowing pressure by the water washing process, which minimizes the damage to the heat exchange elements;

[0021] (4) The alkali recovery furnace water washing process provided by the present invention utilizes existing feed water pumps and soot blowers, etc., without the need to add too many new equipment, with low investment and simple operation. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the process in an embodiment of the present invention; Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0024] See Figure 1 A water washing process for an alkali recovery furnace, wherein the alkali recovery furnace comprises a water-cooled wall, a superheater, an evaporator tube panel, an economizer, a chute, a dissolving tank, an alkali ash tank, a venting tank, and a soot blower, etc. The soot blower of the alkali recovery furnace can be connected to a water supply pipeline, and the furnace washing water is pumped to the soot blower by a water supply pump. The furnace chamber of the alkali recovery furnace is connected to an electrostatic precipitator, which is connected to a chimney through a flue. A disc valve, an induced draft fan, and a gate valve are installed on the flue. The furnace bottom of the alkali recovery furnace is connected to the dissolving tank through a chute. The ash hopper of the economizer and the dust outlet of the electrostatic precipitator are connected to the alkali ash tank, which is connected to the venting tank. The process includes the following steps:

[0025] Step 1: After the alkali recovery furnace is shut down, open the disc valve, the slide valve, and the furnace door to cool the furnace.

[0026] Step 2: After Step 1 is completed, the boiler washing water is pumped by the feed water pump to the soot blower of the alkali recovery furnace. The soot blower washes the surface of the heat exchange elements, cleaning the slag and coking material on the surface of the heat exchange elements. The boiler washing wastewater is recycled through the dissolution tank and the venting tank.

[0027] Step 3: After step 2 is completed, hot air is introduced through the air supply system and exhaust air through the induced draft system to dry the furnace and heat exchange elements;

[0028] Step 4: After step 3 is completed, pour castable into the chute to repair the parts that have been washed away by the combustion molten material and the furnace washing water.

[0029] In one embodiment of the present invention, in step one, the furnace cooling is carried out by natural draft from the chimney, and the furnace temperature is reduced to 80°C. The furnace is cooled for 36 hours under the condition that the furnace temperature is 80°C.

[0030] In one embodiment of the present invention, in step two, the furnace washing water is demineralized water with a temperature of 80°C, a flow rate of 100t / h, a washing pressure of 1.6MPa, a washing time of 5min for each sootblower, and a washing sequence from the tail of the furnace to the head of the furnace, from bottom to top. By designing the washing process, the furnace washing pressure is lower than the steam sootblowing pressure, which minimizes damage to the heat exchange elements.

[0031] In one embodiment of the present invention, in step two, the heat exchange element includes an economizer, a superheater, and a water-cooled wall.

[0032] In one embodiment of the present invention, in step three, the hot air comes from the air supply system of the alkali recovery furnace, the hot air temperature is 120°C, and the air is exhausted through the induced draft system to control the negative pressure in the furnace to 20Pa and the furnace drying time is 16 hours.

[0033] In one embodiment of the present invention, in step three, the air supply system is a multi-layer air supply system consisting of primary air, secondary air and tertiary air, and the induced draft system consists of two induced draft fans.

[0034] In one embodiment of the present invention, in step four, the main component of the castable is chromite sand, and the curing time is 2 days.

[0035] During operation, after the alkali recovery furnace is shut down according to the procedure, the disc valve, the slide valve and the furnace door are opened. The furnace is cooled by the natural draft of the chimney, and the furnace temperature is reduced to 80°C. The cooling time is 36 hours.

[0036] After step one, the boiler washing water is pumped by the feedwater pump to the soot blower of the alkali recovery furnace. The soot blower washes the surfaces of heat exchange elements such as the economizer, superheater, and water-cooled walls, cleaning away any slag and coking deposits. The boiler washing wastewater is recovered through a dissolution tank and a venting tank, and then pumped to the evaporation section or a wastewater treatment plant for further treatment. The boiler washing water is demineralized water at a temperature of 80℃, a flow rate of 100 t / h, and a washing pressure of 1.6 MPa. Each soot blower wash lasts for 5 minutes, and the washing sequence is from the tail of the furnace to the head, from bottom to top.

[0037] After step two is completed, hot air is introduced through the air supply system and exhausted through the exhaust system to dry the furnace and heat exchange elements. The hot air is the primary and secondary air from the air supply system, the hot air temperature is 120℃, and the exhaust is carried out through the exhaust system. The negative pressure in the furnace is controlled at 20Pa, and the furnace drying time is 16 hours.

[0038] After step three is completed, castable refractory is poured into the chute to repair the parts washed away by the combustion molten material and furnace washing water. The main component of the castable refractory is chromite sand, and the curing time is 2 days.

[0039] In summary, the water washing process for alkali recovery furnace provided by this invention has high ash removal and coke removal efficiency and good effect, which can effectively ensure the cleanliness of heat exchange elements, improve the operating efficiency of alkali recovery furnace, increase the steam production of alkali recovery furnace and the power generation of steam turbine; no personnel need to enter the furnace, there are no personnel safety hazards, and the cleaning time is short, which can effectively reduce downtime.

[0040] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A water washing process for an alkali recovery furnace, wherein the alkali recovery furnace comprises a water-cooled wall, a superheater, an evaporator tube panel, an economizer, a chute, a dissolving tank, an alkali ash tank, a venting tank, and a soot blower; the soot blower of the alkali recovery furnace is connected to a water supply pipeline, and a water pump delivers furnace washing water to the soot blower; the furnace chamber of the alkali recovery furnace is connected to an electrostatic precipitator, which is connected to a chimney via a flue; a disc valve, an induced draft fan, and a gate valve are installed on the flue; the furnace bottom of the alkali recovery furnace is connected to the dissolving tank via a chute; the economizer ash hopper and the dust outlet of the electrostatic precipitator are connected to the alkali ash tank; and the alkali ash tank is connected to the venting tank. The process is characterized in that... The process includes the following steps: Step 1: After the alkali recovery furnace is shut down, open the disc valve, the slide valve, and the furnace door to cool the furnace. Step 2: After Step 1 is completed, the boiler washing water is pumped by the feed water pump to the soot blower of the alkali recovery furnace. The soot blower washes the surface of the heat exchange elements, cleaning the slag and coking material on the surface of the heat exchange elements. The boiler washing wastewater is recycled through the dissolution tank and the venting tank. Step 3: After step 2 is completed, hot air is introduced through the air supply system and exhaust air through the induced draft system to dry the furnace and heat exchange elements; Step 4: After step 3 is completed, pour castable into the chute to repair the parts that have been washed away by the combustion molten material and the furnace washing water.

2. The alkali recovery furnace water washing process according to claim 1, characterized in that, In step one, the furnace cooling is achieved by natural draft from the chimney, reducing the furnace temperature to 80°C. The furnace is then cooled for 36 hours at a furnace temperature of 80°C.

3. The alkali recovery furnace water washing process according to claim 1, characterized in that, In step two, the furnace washing water is demineralized water with a temperature of 80℃, a flow rate of 100t / h, a washing pressure of 1.6MPa, a washing time of 5min for each sootblower, and a washing sequence from the tail of the furnace to the head of the furnace, from bottom to top.

4. The alkali recovery furnace water washing process according to claim 1, characterized in that, In step two, the heat exchange elements include an economizer, a superheater, and a water-cooled wall.

5. The alkali recovery furnace water washing process according to claim 1, characterized in that, In step three, the hot air comes from the air supply system of the alkali recovery furnace, the hot air temperature is 120℃, the exhaust air is provided by the induced draft system, the furnace negative pressure is controlled at 20Pa, and the furnace drying time is 16 hours.

6. The alkali recovery furnace water washing process according to claim 5, characterized in that, The air supply system is a multi-layer air supply system consisting of primary, secondary and tertiary air, and the exhaust system consists of two exhaust fans.

7. The alkali recovery furnace water washing process according to claim 1, characterized in that, In step four, the main component of the castable is chromite sand, and the curing time is 2 days.

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