Method for drying sludge by using low-temperature waste heat of lime kiln

Abstract

The present application relates to the technical fields of lime kiln waste heat disposal sludge, and discloses a method for disposing sludge by low-temperature drying using lime kiln waste heat, comprising the following steps: S1, sludge storage and conveying: wet sludge is transported into a sludge storage bin for storage, and after metering, the sludge is conveyed by a screw conveyor; S2, sludge pretreatment; S3, sludge drying treatment; S4, secondary leveling treatment; S5, dry material conveying. The method for disposing sludge by low-temperature drying using lime kiln waste heat can dispose sludge without increasing additional heat consumption, avoid high cost, effectively prevent environmental pollution, has high energy utilization rate, does not need to add coal, and can use odor as combustion-supporting material for secondary high-temperature disposal without adding a waste gas treatment system, thereby realizing the function of low-temperature drying treatment of sludge using lime kiln waste heat.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sludge disposal by lime kiln waste heat, in particular to a method for low-temperature drying and disposal of sludge by using lime kiln waste heat. BACKGROUND

[0002] Calcined lime has a long history in China. Now, the amount of lime used in the metallurgical, chemical and building material industries is increasing, and the pressure of energy saving and emission reduction is also increasing. At present, rotary kiln is widely used in lime production in China. The waste heat in the exhaust gas at the tail of the rotary kiln is used for lime kiln cooperation. The low-temperature drying is carried out at the same time, and the dried sludge is used as a substitute fuel to enter the rotary kiln for final disposal. This is a new attempt and development in the field of environmental protection and solid waste disposal.

[0003] In the prior art, the sludge is dried by the way of entering the field after drying, building a coal-fired and gas-fired boiler, and extracting high-temperature flue gas. However, in actual use, the heat of the sludge entering the field is solved by the sewage treatment plant, which is costly. The dried sludge can bring part of the heat to the lime kiln, but the sewage treatment plant cannot bear the disposal fee required by the cement plant. The way of building a coal-fired and gas-fired boiler uses a separate coal-fired or gas-fired boiler to generate heat for sludge drying. Although it has no effect on the calcination of the lime kiln, the sludge can be used as a substitute fuel to replace coal, and the drying cost is relatively low, but it has a greater impact on the environment. The way of extracting high-temperature flue gas can extract high-temperature flue gas for direct or indirect drying, but excessive extraction will affect the production system, and a large amount of high-temperature heat will be extracted, which requires the production system to supplement coal, and the energy utilization rate is not high, and the overall economy is poor. Therefore, a method for low-temperature drying and disposal of sludge by using lime kiln waste heat is needed. SUMMARY

[0004] (I) Technical solution

[0005] To achieve the above-mentioned disposal of sludge by lime kiln waste heat, the present application provides the following technical solution: a method for low-temperature drying and disposal of sludge by using lime kiln waste heat, comprising the following steps:

[0006] S1, sludge storage and conveying

[0007] The wet sludge is transported into the sludge storage bin for storage. After metering, the sludge is conveyed by a screw conveyor.

[0008] S2, sludge pretreatment

[0009] The sludge is cut by a slitting machine, and the sludge strips are evenly laid on the conveying belt by the slitting machine.

[0010] S3, sludge drying treatment

[0011] The low-temperature belt dryer uses several independent drying chambers. Each independent drying chamber uses two sets of large-volume, low-speed axial flow fans to allow the drying hot air to be exchanged in both the upper and lower directions, blowing and agitating the sludge for drying. The mesh belt in the drying chamber adopts a two-layer stacked design.

[0012] S4. Secondary leveling treatment

[0013] By installing a rake device above the conveyor belt, the sludge strips are leveled a second time, and the material is tumbled a second time, increasing the drying efficiency.

[0014] S5, Drying Material Conveying

[0015] The dried sludge is transported to the tail of the lime kiln via a zipper, and then enters the rotary kiln through a chute to complete the final decomposition and combustion.

[0016] Preferably, in step S1, the capacity and shape of the sludge storage silo are specially designed to prevent material sticking. A mechanical vibrating device is installed on the silo wall. The feeding conveyor end adopts a shaftless spiral cutter, and the discharge adopts a chain conveyor. An airlock device and an odor adsorption pipe are designed for the conveying end or the discharge end. The sludge is introduced into the cooler in the lime kiln by an induced draft fan, and then enters the lime kiln.

[0017] A weighing conveyor belt is installed at the bottom of the silo. The sludge that has been weighed and measured enters the closed inclined chain conveyor and then enters the small silo of the drying machine.

[0018] Preferably, in step S2, a material spreading device is provided at the bottom of the dryer compartment to ensure that the material is spread out in the horizontal direction of feeding and then enters the roller noodle machine for cutting into strips. The cut material then enters the upper belt.

[0019] A material straightening device is installed at the end of the upper belt to reshape the sludge, ensuring that the sludge is spread evenly on the belt to further achieve the drying effect, preventing localized material accumulation that could lead to excessively high drying moisture content, and at the same time ensuring that the material resistance on the belt is consistent to avoid air short circuits.

[0020] Preferably, in step S2, the fabric adopts a double helix structure, and the speed and direction are adjustable.

[0021] The twin-helix system uses two motors, which can ensure synchronous operation as well as asynchronous operation. It can perform preliminary pretreatment of materials, crush large pieces of materials, and at the same time maximize the flatness of the material curtain.

[0022] Preferably, in step S3, the heat source required for drying is provided by a heat recovery device installed in the exhaust gas pipeline of the lime kiln. Soft water is introduced into the heat recovery device. The soft water entering the heat recovery device exchanges heat with the flue gas and finally provides 100°C hot water or hot steam. It is connected to the heat exchanger of the dryer through a pipeline. The heat exchanger of the dryer provides the heat source for sludge drying in the low-temperature dryer. After exchanging heat with the circulating air in the heat exchanger of the dryer, the temperature drops to 50°C and the cold water re-enters the heat recovery device, thus forming a closed-loop system.

[0023] After passing through the heat exchanger of the dryer, the circulating air temperature is about 70°C. It then enters the low-temperature dryer to dry the sludge. The high-humidity circulating air after the sludge is dried enters the cooler to cool and dehumidify. Then it continues to enter the heat exchanger of the dryer to exchange heat and repeat the drying process.

[0024] Preferably, the heat recovery unit heats the water to a maximum of 100°C, and then the hot water and hot air are introduced into the heat exchanger of the dryer through water pipes to exchange heat with the circulating air of the dryer.

[0025] The heat recovery unit replaces the quenching device at the tail of the lime kiln, with a flue gas inlet temperature of 200℃ and an outlet temperature of 100℃.

[0026] A heat recovery unit is a heat exchanger that uses waste heat from flue gas to heat water. The heat exchanger absorbs the waste heat from the flue gas, reducing the flue gas temperature. The water is heated to above 100°C in the heat exchanger, and at the same time, some of the hot water can be converted into steam at above 100°C. The heat exchanger contains a mixture of hot water and steam.

[0027] Preferably, the cold water replenishment in the heat recovery unit is softened water, a dosing device is installed at the cold water replenishment end, a filtration device is used to ensure that the boiler water is qualified, and the temperature of the hot water after heat exchange in the heat recovery unit is controlled within 95-100℃.

[0028] The water is pumped into the heat exchanger inside the dryer, and the return water at 75°C is pumped into the flue gas heat exchanger. The heat recovery unit consists of a series of parallel serpentine tubes made of stainless steel to prevent dust accumulation and corrosion. Appropriate spacing is selected, and compressed air is used to periodically blow away the dust.

[0029] Preferably, the cooling device is retained, and a flue gas branch pipe is set to lead to the heat recovery unit. A louvered valve is installed on the pipe before entering the heat recovery unit and controlled by an electric actuator. When the sludge drying equipment stops, the valve can be closed, and the flue gas from the kiln tail continues to return to the original pipe and enter the quenching device to quench the flue gas, without affecting the normal operation of the lime kiln.

[0030] The hot air from the heat recovery unit returns to the original pipeline and then enters the kiln tail bag filter. The lower part of the heat recovery unit is designed as an ash hopper to collect the dust that settles down from the flue gas in the heat recovery unit. The dust is then conveyed into the kiln tail bag filter through a conveyor.

[0031] The heat recovery unit adopts a periodic high-pressure jet cleaning method, with three rows of tubes (top, middle, and bottom) for cleaning the boiler tubes and preventing ash accumulation.

[0032] Preferably, in step S4, the raking device is set at the upper feed end of the first conveyor belt of the low-temperature belt dryer, arranged in two rows, to rake down the locally piled material.

[0033] Preferably, in step S5, an airlock device is also provided at the material chute to prevent air leakage and backfire, and an air blockage remover is also provided to clean it regularly to prevent sludge from accumulating there.

[0034] The odor generated from sludge drying and the odor collected in the environment are piped to the vertical cooler at the kiln head of the lime kiln. After cooling the lime together with the air, the odor enters the rotary kiln as combustion air.

[0035] The dried sludge is fed into the bottom of the preheater, where the organic components in the sludge are removed at high temperature within this temperature range, and the heat is released to replace fuel.

[0036] The inorganic components in the sludge enter the rotary kiln and are ultimately incorporated into the lime product. Alternatively, they can be mixed with coal powder in the lime kiln as fuel and fed into the lime kiln to replace fossil fuels. They can also be transported to cement plants for use as fuel in cement production.

[0037] (II) Beneficial Effects

[0038] Compared with the prior art, the present invention provides a method for low-temperature drying and treatment of sludge using waste heat from a lime kiln, which has the following beneficial effects:

[0039] 1. This method of using waste heat from lime kilns for low-temperature drying and treatment of sludge can dry sludge without increasing excess heat consumption, avoiding high costs, effectively preventing environmental pollution, and achieving high energy utilization. It does not require additional coal supply, and the odorous gas is used as a combustion aid for secondary high-temperature treatment, eliminating the need for an additional waste gas treatment system. This method realizes the function of using waste heat from lime kilns for low-temperature drying and treatment of sludge.

[0040] 2. This method of using waste heat from lime kilns to dry sludge at low temperatures can make reasonable use of waste heat through the installation of a heat recovery device. Compared with low-temperature belt drying in a single airflow direction, it can complete the drying process from two different processes, namely upwind and downwind, drying from the top and bottom of the sludge particles respectively. At the same time, a material distribution device and a material cloth device are installed at the bottom of the strip cutter to ensure uniform material distribution and improve drying efficiency. Attached Figure Description

[0041] Figure 1 This is a flow chart of the sludge treatment process of the present invention. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Please see Figure 1 This invention provides a technical solution: a method for low-temperature drying and treatment of sludge using waste heat from a lime kiln, comprising the following steps:

[0044] S1. Sludge storage and transportation

[0045] The wet sludge is transported to the site and stored in the sludge storage silo. After being metered, the sludge is transported by a screw conveyor.

[0046] S2, sludge pretreatment

[0047] The sludge is cut into strips using a strip cutter, and the strips are then evenly spread onto the conveyor belt.

[0048] S3, sludge drying treatment

[0049] The low-temperature belt dryer uses several independent drying chambers. Each independent drying chamber uses two sets of large-volume, low-speed axial flow fans to allow the drying hot air to be exchanged in both the upper and lower directions, blowing and agitating the sludge for drying. The mesh belt in the drying chamber adopts a two-layer stacked design.

[0050] S4. Secondary leveling treatment

[0051] By installing a rake device above the conveyor belt, the sludge strips are leveled a second time, and the material is tumbled a second time, increasing the drying efficiency.

[0052] S5, Drying Material Conveying

[0053] The dried sludge is transported to the tail of the lime kiln via a zipper, and then enters the rotary kiln through a chute to complete the final decomposition and combustion.

[0054] Furthermore, in step S1, the capacity and shape of the sludge storage silo are specially designed to prevent material sticking. A mechanical vibrating device is installed on the silo wall. The feeding conveyor end adopts a shaftless spiral cutter, and the discharge adopts a chain conveyor. An airlock device and an odor adsorption pipe are designed for the conveying end or discharge end. The sludge is introduced into the cooler in the lime kiln by an induced draft fan, and then enters the lime kiln.

[0055] A weighing conveyor belt is installed at the bottom of the silo. The sludge that has been weighed and measured enters the closed inclined chain conveyor and then enters the small silo of the drying machine.

[0056] Furthermore, in step S2, a material spreading device is installed at the bottom of the dryer compartment to ensure that the material is spread out in the horizontal direction of feeding and then enters the roller noodle machine for cutting into strips. The cut material then enters the upper belt.

[0057] A material straightening device is installed at the end of the upper belt to reshape the sludge, ensuring that the sludge is spread evenly on the belt to further achieve the drying effect, preventing localized material accumulation that could lead to excessively high drying moisture content, and at the same time ensuring that the material resistance on the belt is consistent to avoid air short circuits.

[0058] Furthermore, in step S2, the fabric adopts a double helix structure, and the speed and direction are adjustable.

[0059] The twin-helix system uses two motors, which can ensure synchronous operation as well as asynchronous operation. It can perform preliminary pretreatment of materials, crush large pieces of materials, and at the same time maximize the flatness of the material curtain.

[0060] Furthermore, in step S3, the heat source required for drying is provided by a heat recovery device installed in the exhaust gas pipeline of the lime kiln. Soft water is introduced into the heat recovery device. The soft water entering the heat recovery device exchanges heat with the flue gas and finally provides 100°C hot water or hot steam. It is connected to the heat exchanger of the dryer through a pipeline. The heat exchanger of the dryer provides the heat source for sludge drying in the low-temperature dryer. After exchanging heat with the circulating air in the heat exchanger inside the dryer, the temperature drops to 50°C and the cold water re-enters the heat recovery device, thus forming a closed-loop system.

[0061] After passing through the heat exchanger of the dryer, the circulating air temperature is about 70°C. It then enters the low-temperature dryer to dry the sludge. The high-humidity circulating air after the sludge is dried enters the cooler to cool and dehumidify. Then it continues to enter the heat exchanger of the dryer to exchange heat and repeat the drying process.

[0062] Furthermore, the heat recovery unit heats the water to a maximum of 100°C, and then the hot water and hot air are introduced into the heat exchanger of the dryer through water pipes to exchange heat with the circulating air of the dryer.

[0063] The heat recovery unit replaces the quenching device at the tail of the lime kiln, with a flue gas inlet temperature of 200℃ and an outlet temperature of 100℃.

[0064] A heat recovery unit is a heat exchanger that uses waste heat from flue gas to heat water. The heat exchanger absorbs the waste heat from the flue gas, reducing the flue gas temperature. The water is heated to above 100°C in the heat exchanger, and at the same time, some of the hot water can be converted into steam at above 100°C. The heat exchanger contains a mixture of hot water and steam.

[0065] Furthermore, the cold water replenishment in the heat recovery unit uses softened water, a dosing device is installed at the cold water replenishment end, and a filtration device is used to ensure that the boiler water is qualified. The temperature of the hot water after heat exchange in the heat recovery unit is controlled within 95-100℃.

[0066] The water is pumped into the heat exchanger inside the dryer, and the return water at 75°C is pumped into the flue gas heat exchanger. The heat recovery unit consists of a series of parallel serpentine tubes made of stainless steel to prevent dust accumulation and corrosion. Appropriate spacing is selected, and compressed air is used to periodically blow away the dust.

[0067] Furthermore, the cooling device is retained, and a branch pipe for flue gas is installed leading to the heat recovery unit. A louvered valve is installed on the pipe before entering the heat recovery unit, which is controlled by an electric actuator. When the sludge drying equipment is shut down, the valve can be closed, and the flue gas from the kiln tail continues to return to the original pipe and enter the quenching device to quench the flue gas, without affecting the normal operation of the lime kiln.

[0068] The hot air from the heat recovery unit returns to the original pipeline and then enters the kiln tail bag filter. The lower part of the heat recovery unit is designed as an ash hopper to collect the dust that settles down from the flue gas in the heat recovery unit. The dust is then conveyed into the kiln tail bag filter through a conveyor.

[0069] The heat recovery unit adopts a periodic high-pressure jet cleaning method, with three rows of tubes (top, middle, and bottom) for cleaning the boiler tubes and preventing ash accumulation.

[0070] Furthermore, in step S4, the material raking device is set at the upper feed end of the first conveyor belt of the low-temperature belt dryer, arranged in two rows, to rake down the locally piled material.

[0071] Furthermore, in step S5, an airlock device is also installed at the material discharge chute to prevent air leakage and backfire. An air blockage remover is also installed to clean the chute regularly and prevent sludge from accumulating there.

[0072] The odor generated from sludge drying and the odor collected in the environment are piped to the vertical cooler at the kiln head of the lime kiln. After cooling the lime together with the air, the odor enters the rotary kiln as combustion air.

[0073] The dried sludge is fed into the bottom of the preheater, where the organic components in the sludge are removed at high temperature within this temperature range, and the heat is released to replace fuel.

[0074] The inorganic components in the sludge enter the rotary kiln and are ultimately incorporated into the lime product. Alternatively, they can be mixed with coal powder in the lime kiln as fuel and fed into the lime kiln to replace fossil fuels. They can also be transported to cement plants for use as fuel in cement production.

[0075] This method of using waste heat from lime kilns for low-temperature drying of sludge can dry sludge without increasing heat consumption, avoiding high costs, effectively preventing environmental pollution, and achieving high energy utilization. It eliminates the need for coal replenishment, and the odorous gases are used as combustion aids for secondary high-temperature treatment, eliminating the need for additional waste gas treatment systems. This method utilizes the waste heat of lime kilns for low-temperature drying of sludge. Through the installation of a heat recovery unit, the waste heat can be rationally utilized. Compared with single-direction low-temperature belt drying, it can complete the drying process from two different stages: upwind and downwind, drying from the top and bottom of the sludge particles respectively. Simultaneously, a material distribution device and a material cloth device are installed below the slitting machine to ensure uniform material distribution and improve drying efficiency.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for low-temperature drying and treatment of sludge using waste heat from a lime kiln, characterized in that, Includes the following steps: S1. Sludge storage and transportation The wet sludge is transported to the site and stored in the sludge storage silo. After being metered, the sludge is transported by a screw conveyor. S2, sludge pretreatment The sludge is cut into strips using a strip cutter, and the strips are then evenly spread onto the conveyor belt. S3, sludge drying treatment The low-temperature belt dryer uses several independent drying chambers. Each independent drying chamber uses two sets of large-volume, low-speed axial flow fans to allow the drying hot air to be exchanged in both the upper and lower directions, blowing and agitating the sludge for drying. The mesh belt in the drying chamber adopts a two-layer stacked design. S4. Secondary leveling treatment By installing a rake device above the conveyor belt, the sludge strips are leveled a second time, and the material is tumbled a second time, increasing the drying efficiency. S5, Drying Material Conveying The dried sludge is transported to the tail of the lime kiln via a zipper, and then enters the rotary kiln through a chute to complete the final decomposition and combustion. In step S1, the capacity and shape of the sludge storage silo are specially designed to prevent material sticking. A mechanical vibration device is installed on the silo wall. The feeding conveyor end adopts a shaftless spiral cutter, and the discharge adopts a chain conveyor. An air lock device and an odor adsorption pipe are designed for the conveying end or the discharge end. The sludge is introduced into the lime kiln cooler by an induced draft fan and then enters the lime kiln. A weighing conveyor belt is installed at the bottom of the silo. The sludge that has been weighed and measured enters the closed inclined chain conveyor and then enters the small silo of the dryer. In step S2, a material feeding device is provided at the bottom of the dryer compartment to ensure that the material is spread out in the horizontal direction of feeding and then enters the roller noodle machine for cutting into strips. The cut material then enters the upper belt. A material straightening device is installed at the end of the upper belt to reshape the sludge, ensuring that the sludge is spread evenly on the belt to further achieve the drying effect, preventing localized material accumulation that could lead to excessively high drying moisture content, and at the same time ensuring that the material resistance on the belt is consistent to avoid air short circuits. In step S3, the heat source required for drying is provided by a heat recovery device installed in the exhaust gas pipeline of the lime kiln. Soft water is introduced into the heat recovery device. The soft water entering the heat recovery device exchanges heat with the flue gas and finally provides 100°C hot water or hot steam. It is connected to the heat exchanger of the dryer through a pipeline. The heat exchanger of the dryer provides the heat source for sludge drying to the low-temperature belt dryer. After exchanging heat with the circulating air in the heat exchanger of the dryer, the temperature drops to 50°C and the cold water re-enters the heat recovery device, thus forming a closed-loop system. After passing through the heat exchanger of the dryer, the circulating air temperature is about 70°C. It then enters the low-temperature belt dryer to dry the sludge. The high-humidity circulating air after the sludge is dried enters the cooler to cool down and dehumidify. Then it continues to enter the heat exchanger of the dryer to exchange heat and repeat the drying process. The cooling device is retained, and a branch pipe for flue gas is set up to lead to the heat recovery unit. A louvered valve is installed on the pipe before entering the heat recovery unit and controlled by an electric actuator. When the sludge drying equipment is stopped, the valve is closed, and the flue gas from the kiln tail continues to return to the original pipe and enters the quenching device to quench the flue gas, which does not affect the normal operation of the lime kiln. The hot air from the heat recovery unit returns to the original pipeline and then enters the kiln tail bag filter dust collector. The lower part of the heat recovery unit is designed as an ash hopper to collect the dust that settles down from the flue gas in the heat recovery unit. Then, it is fed into the kiln tail bag filter dust collector through a conveying cutter. The heat recovery unit adopts a periodic high-pressure jet cleaning method, with three rows of tubes (top, middle, and bottom) for cleaning the boiler tubes and preventing ash accumulation.

2. The method for low-temperature drying and treatment of sludge using waste heat from a lime kiln according to claim 1, characterized in that, In step S2, the fabric adopts a double helix structure, and the speed and direction are adjustable. The twin-helix system uses two motors, which can ensure synchronous operation as well as asynchronous operation. It can perform preliminary pretreatment of materials, crush large pieces of materials, and at the same time maximize the flatness of the material curtain.

3. The method for low-temperature drying and treatment of sludge using waste heat from a lime kiln according to claim 1, characterized in that, The heat recovery unit heats water to a maximum of 100°C, and then the hot water and hot air are introduced into the heat exchanger of the dryer through water pipes to exchange heat with the circulating air of the dryer. The heat recovery unit replaces the quenching device at the tail of the lime kiln, with a flue gas inlet temperature of 200℃ and an outlet temperature of 100℃. The heat recovery unit uses the waste heat of flue gas to heat water. The heat exchanger absorbs the waste heat of the exhaust gas and reduces the exhaust gas temperature. The water is heated to above 100°C in the heat exchanger, and at the same time, some of the hot water can be converted into steam above 100°C. The heat exchanger contains a mixture of hot water and steam.

4. The method for low-temperature drying and treatment of sludge using waste heat from a lime kiln according to claim 1, characterized in that, The cold water supply in the heat recovery unit is softened water. A dosing device is installed at the cold water supply end, and a filtration device is used to ensure that the boiler water is qualified. The temperature of the hot water after heat exchange in the heat recovery unit is controlled within 95-100℃. The water is pumped into the heat exchanger of the dryer, and the return water at 75°C is pumped into the flue gas heat exchanger. The heat recovery unit consists of a series of parallel serpentine tubes made of stainless steel to prevent dust accumulation and corrosion. Appropriate spacing is selected, and compressed air is used to periodically blow away the dust.

5. The method for low-temperature drying and disposal of sludge using waste heat from a lime kiln according to claim 1, characterized in that, In step S4, the material raking device is set at the upper feed end of the first conveyor belt of the low-temperature belt dryer, arranged in two rows, to rake down the locally piled material.

6. The method for low-temperature drying and disposal of sludge using waste heat from a lime kiln according to claim 1, characterized in that, In step S5, an airlock device is also installed at the material chute to prevent air leakage and backfire. An air blockage remover is also installed to clean the chute regularly and prevent sludge from accumulating there. The odor generated from sludge drying and the odor collected in the environment are piped to the vertical cooler at the kiln head of the lime kiln. After cooling the lime together with the air, the odor enters the rotary kiln as combustion air. The dried sludge is fed into the bottom of the preheater, where the organic components in the sludge are removed at high temperature within this temperature range, and heat is released to replace fuel. The inorganic components in the sludge enter the rotary kiln and are ultimately incorporated into the lime product. Alternatively, they can be mixed with coal powder in the lime kiln as fuel and fed into the lime kiln to replace fossil fuels. They can also be transported to cement plants for use as fuel in cement production.

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