How to improve the environmental performance of mechanical fossil ash kilns
With the increasingly strict environmental requirements and the deepening of the concept of sustainable development, mechanical fossil ash kilns face a huge challenge in reducing environmental pollution during the production process. Improving the environmental performance of mechanical fossil ash kilns not only helps reduce negative impacts on the surrounding environment, but also enhances the social image and economic benefits of the enterprise. This article will explore various effective ways to improve the environmental performance of mechanical fossil ash kilns.
1、 Optimize the combustion process
（1） Fuel selection
Promote clean energy
Prioritize the use of clean energy sources such as natural gas and biomass as fuel for lime kilns. The pollutants generated during the combustion of natural gas are relatively low, such as sulfur dioxide, nitrogen oxides, and dust emissions, which are much lower than those of traditional coal. Biomass energy, as a renewable energy source, can generate carbon dioxide through plant photosynthesis for cyclic absorption.
Taking a medium-sized mechanical fossil ash kiln as an example, using natural gas instead of coal as fuel can reduce sulfur dioxide emissions by about 80% and nitrogen oxide emissions by about 50%.
Clean coal technology
If coal is still used as fuel, clean coal technologies such as coal washing and shaping should be adopted. Washing coal can remove some sulfur and ash content from coal, reducing the generation of pollutants during combustion. Briquette reduces sulfur dioxide emissions by adding sulfur fixing agents and other methods.
After testing, using washed coal can reduce the sulfur content of coal from around 1.5% to around 0.8%, effectively reducing sulfur dioxide emissions.
（2） Combustion control technology
Accurately control the air-fuel ratio
Install advanced automation control systems to precisely adjust the ratio of air to fuel. When the air-fuel ratio is at its optimal state, the fuel can burn fully, reducing the generation of incomplete combustion products.
For example, by monitoring the oxygen content during the combustion process in real-time and using an intelligent control system to automatically adjust the fan speed, the air-fuel ratio can be maintained within the range of 1.05-1.15, which can improve combustion efficiency and reduce pollutant emissions.
Graded combustion
Adopting staged combustion technology, the combustion process of fuel is divided into multiple stages. Maintain a low air volume in the main combustion zone to promote incomplete combustion of the fuel, creating a reducing atmosphere. Then, gradually replenish air in the reignition and burnout zones to achieve complete combustion of the fuel. This method can reduce the generation of nitrogen oxides.
Practice has proven that staged combustion technology can reduce nitrogen oxide emissions by 30% to 50%.
2、 Strengthen dust control
（1） Application of high-efficiency dust collector
Bag filter
Bag filter is an important equipment for dust control in lime kilns. It filters the dusty gas through a filter bag, trapping the dust on the surface of the filter bag. Choose high-quality filter bag materials, such as polytetrafluoroethylene (PTFE) coated filter bags, which have high filtration accuracy, low resistance, and good dust removal effect.
For a mechanical fossil ash kiln with a daily output of 100 tons, after installing a bag filter, the dust emission concentration can be controlled below 10mg/m ³, meeting national environmental standards.
Electrostatic precipitator
Electrostatic precipitators use an electric field to charge dust particles and collect them onto electrodes under the force of the electric field. It has the advantages of large air volume, low resistance, and low energy consumption.
In large mechanical fossil ash kilns, electrostatic precipitators can effectively process a large amount of dusty gases, resulting in lower levels of dust emissions.
（2） Optimize production process
Sealing and negative pressure operation
Seal the inlet, outlet, and kiln body connections of the lime kiln to prevent dust from escaping. At the same time, establish a negative pressure environment inside the kiln to effectively collect dusty gases into the dust removal system.
By sealing and negative pressure operation, the unorganized emission of dust can be reduced, and the collection efficiency of dust can be improved.
Raw material pretreatment
When crushing and screening raw materials such as limestone, wet operations or installing local dust removal equipment are used to reduce the dust generated during the raw material processing.
For example, adding a water spray device in the raw material crushing process can reduce the amount of dust generated by about 60%.
3、 Waste gas treatment measures
（1） Desulfurization and denitrification process
Desulfurization technology
Using desulfurization processes such as lime gypsum method and ammonia method to treat sulfur dioxide in lime kiln exhaust gas. The lime gypsum method involves spraying lime slurry into an absorption tower, reacting with sulfur dioxide in the exhaust gas to produce calcium sulfite, which is then oxidized to calcium sulfate (gypsum). The ammonia method is to use ammonia to react with sulfur dioxide to produce ammonium sulfite, which is further processed into ammonium sulfate fertilizer.
Taking the lime gypsum method as an example, the desulfurization efficiency can reach over 95%, which can effectively reduce the content of sulfur dioxide in exhaust gas.
Denitrification technology
For the removal of nitrogen oxides, denitrification technologies such as selective catalytic reduction (SCR) and selective non catalytic reduction (SNCR) can be used. SCR technology reduces nitrogen oxides to nitrogen and water using a reducing agent (such as ammonia) under the action of a catalyst; SNCR technology directly sprays reducing agents for denitrification in high-temperature areas.
The denitrification efficiency of SCR technology can reach 80% -90%, while the denitrification efficiency of SNCR technology is about 30% -50%. In practical applications, suitable denitrification technologies can be selected based on factors such as the scale of the lime kiln and the characteristics of the exhaust gas.
（2） Waste gas and heat recovery and utilization
Waste heat boiler
Install a waste heat boiler to generate steam from the waste heat in the lime kiln exhaust gas. The generated steam can be used for power generation, heating, production processes, etc., achieving energy recovery and utilization.
For example, a medium-sized mechanical fossil ash kiln can recover about 5000-8000 tons of steam annually through a waste heat boiler, which not only reduces energy waste but also lowers the exhaust gas emission temperature, which is beneficial for the operation of subsequent exhaust gas treatment equipment.
air preheater
Preheating the air entering the lime kiln using waste heat from exhaust gas. Preheated air can improve combustion efficiency, reduce fuel consumption, and lower exhaust emissions temperature and pollutant concentration.
By using an air preheater, the preheating temperature of the air can be increased by 50-100 ° C, and the combustion efficiency can be improved by about 5% -10%.
4、 Wastewater treatment and recycling
（1） Wastewater treatment system
Precipitation and filtration
Establish a wastewater treatment system to precipitate and filter the wastewater generated during the lime kiln production process, such as equipment cooling wastewater and waste gas treatment wastewater. By adding chemical agents such as coagulants, suspended solids in wastewater are precipitated, and then fine particles are removed through filtration equipment.
After sedimentation and filtration treatment, the suspended solids content in the wastewater can be reduced to below 50mg/L, meeting the wastewater discharge standards or reuse requirements.
Neutrality treatment
Due to the alkaline nature of lime kiln wastewater, neutralization treatment is required. The pH value of wastewater can be adjusted to the range of 6-9 by adding acidic agents such as sulfuric acid, hydrochloric acid, etc.
By neutralization treatment, the acidity and alkalinity of wastewater can meet environmental protection requirements, avoiding pollution to the environment.
（2） Wastewater recycling
Process reuse water
Reuse the treated wastewater in the lime kiln production process, such as for raw material humidification, equipment cooling, and other processes. This can reduce the use of fresh water and lower wastewater discharge.
For example, a mechanical fossil ash kiln can reuse treated wastewater for raw material humidification, reducing fresh water usage by about 10-20 cubic meters per day.
Circulating cooling system
Establish a circulating cooling system to recycle the cooling wastewater. By adding corrosion inhibitors, fungicides, and other chemicals, corrosion of cooling equipment and microbial growth can be prevented.
The circulating cooling system can achieve a reuse rate of over 90% for cooling wastewater, greatly reducing wastewater discharge.
5、 Noise control
（1） Sound source control
Select low-noise equipment
In the construction and equipment renewal process of mechanical fossil ash kilns, low-noise equipment should be prioritized. For example, selecting low-noise equipment such as fans, motors, and crushers can reduce the generation of noise from the sound source.
Compared with traditional equipment, low-noise devices can reduce the noise level by about 5-10 decibels.
Equipment shock absorption and sound insulation
Perform shock-absorbing treatment on high noise equipment, such as installing shock-absorbing pads, shock-absorbing springs, etc. on the equipment base. At the same time, the equipment should be wrapped with soundproof materials (such as soundproof cotton, soundproof felt, etc.) to reduce the spread of noise.
By implementing shock absorption and sound insulation measures, equipment noise can be reduced by approximately 10-15 decibels.
（2） Control of transmission routes
Reasonable layout
Reasonably arrange the location of equipment and production workshops in the factory planning of lime kilns. Keep high noise equipment away from sensitive areas such as office and residential areas, and use buildings, green belts, etc. as noise barriers.
By reasonable layout, the impact of noise on the surrounding environment can be effectively reduced.
Install sound insulation facilities
Install sound insulation facilities on the path of noise transmission, such as soundproof walls, soundproof doors and windows, etc. Soundproofing walls can be made of materials such as bricks, concrete, or metal plates, and their sound insulation effect can reach 20-30 decibels.
For example, installing soundproof walls around the factory building of a mechanical fossil ash kiln can significantly reduce the noise at the factory boundary and meet national noise emission standards.
Improving the environmental performance of mechanical fossil ash kilns requires comprehensive consideration from multiple aspects such as combustion process, dust control, exhaust gas treatment, wastewater treatment, and noise control, and a series of effective measures should be taken. By optimizing production processes and adopting advanced environmental protection equipment and technology, not only can the pollution caused by lime kiln production be reduced, but also the recycling and utilization of resources can be achieved, improving the economic benefits and sustainable development capabilities of enterprises.
