Manufacturing process of Lime
1. QUICK LIME PRODUCTION PROCESS
– Coal: The kiln with new ventilation system allows to use coal and coal with impurities (heat: 5400 kcal) instead of using only high quality coal as previously to reduce price. We have stable supply in Ninh Binh.
– Limestone: Trucks will transport limestones from mine to factory’s warehouse. Specs: CaCO3 98%, CaO 54% min, MgO 0.8% max, without impurities.
Production process diagram
Coal will be put into the hopper by excavators after sorting. From hopper, Coal will be brought through quantitative conveyor and put into bucket conveyor and spread on the kiln.
Limestone after screening (size: 40-80mm) will be brought through bucket conveyor to kiln.
According to properties of consecutive kiln, materials move vertically from top to bottom during subsidence. Products go through DRYING – BURNING – COOLING processes. Airflow shall be blown into kiln with natural pressure difference from the bottom up through the slits materials, providing oxygen for burning process in kiln.
Reaction process in kiln:
At 20-30m, coal and limestone are heated from 200 to 300 degrees. Water and impurities are evaporated and burnt. During subsidence, materials keep going down to 10-20m, coal reacts with O2 to create burning at 1000-2000 degrees and Limestone is transformed into calcite lime. At 0-10m from the bottom of the kiln, Coal is burnt but the temperature still around 300 degrees, air is heated to provide oxygen for burning. Time of a cycle is 35 hours.
The chemical reaction during burning:
Beyond reactions above, there are many other chemical reactions during burning as SO2, NOx, MgO…
Output products shall be transported by conveyor belt, unsatisfied ones shall be classified and removed. Lime then will be put into jaw crusher and vibrating filter for classifying into right size as per custom Lastly, lime will be packed directly into bag at filter place or stored in silo as per customer request.
Because we own limestone mine with high quality, so our products reach extremely high quality. Specs: CaO 90% min, MgO max 1.5%, and other criterias meet all requirements of fastidious industry such as steel, environment treatment, metallurgy.
2. PRODUCTION LINE OF QUICK LIME POWDER
The main material is Quick Lime lump with specification: CaO 90% Min and MgO 1.5% Max.
Chart of Production process:
Quick lime lump after burning in the kiln will be trucked to grinding workshop and put directly into material silo. From Silo, quick lime will go on the automatic conveyor and come to grinding machine. After measuring, material is conveyed to crushing machine through two wards and rotary valve system. Feeder conveyor has metal separation system of magnetic and non-magnetic. Grinding mill reflux also goes through metal separation system of magnetic and non-magnetic before returning to grinding table. Materials are put into center of grinding table. Grinding table is driven by motor through gear box. Due to the rotation of grinding table and effect of centrifugal force, materials are spreaded out into crushing zone between reels. Due to friction and pressure of reels on grinding table, materials are broken into small pieces and fine crushing. Hot air flow to dry the materials is taken from conditioner tower or sub-kiln through wind pipe is divided into two branches. We can adjust the air flow in the grinding mill by modify the valve of the fan. After crushing, materials will move toward the gas injection. Drying airflow going through combining air nozzle and material are rolled up to dissociation part. Raw particles bump in wings of dissociation part then lose its kinetic energy, fall in bevel and return grinding chamber. Smaller particles which are appropriate in terms of size and finery are moved to and collected mostly in cyclone by airflow; the remaining are moved to and collected in electrostatic dust filter.
Quick lime powder from Cyclon of grinding mill is taken to silo by screw conveyor. Products are classified and packing up on customer requirement.
3. PRODUCTION PROCESS OF HYDRATED LIME
The main raw material is Quick Lime lump CaO 90% Min and MgO 1.5% Max
Life cycle of Hydrated Lime:
Diagram of production process:
Quick Lime in the 1st tank goes through the grinding maching to get the standard size range about 100-120 micron, is moved to the 1st silo by the conveyor bucket. The Quick lime from the 1st Silo through the weight batcher goes to the reactor. There are 3 floors of the reactor including the agitator shafts. The quick lime goes from the 3rd floor down to the 2nd then 1st floor. On the 3rd floor quick lime slakes with water being sprayed directly from the nozzle at a rate sufficient to be controlled by computer. After quick lime slakes with water on the 3rd floor it moves down to the 1st floor thanks to the driving shafts. The reaction as follows:
CaO + H2O –> Ca(OH)2 + to
This is an exothermic reaction, the slaking process of the water with quick lime is ongoing that results in extremely high temperature in the kiln. The furnace gas aspirator parts are inserted to suck the hot air in the entire 3rd floor, then runs through an air circulation blower of the furnace gas to reduce the temperature (After drying on the 1st floor and 2nd floor, product continues going through the cold tank).
Through the above steps hydrated lime is basically created but in raw form and particle size with some impurities (particle size at this time is 75-120 microns). All of the product goes through 3 reactor floors to the separator machine via the 3rd bucket. The separator filter separates impurities and particles that do not meet size requirements in one side and the pure hydrated lime in the other side.
The pure product after leaving the separator machine goes up the tank of the finished products via the 4th bucket for packing as per customers requirement.
In hydrated lime tank, weight batcher is equipped for packing process (depending on the requirement of customers, there are some different kinds of packing). Hydrated lime is stored/ taken out of store appropriately and in the right order.