MCP & DCP

MCP PROCESS DESCRIPTION

Brief Process Description

Introduction:

The Mini-Granular Mono Calcium Phosphate – MCP – is based on the following process and chemistry. It can be demonstrated by the reactions below.  

1.    REACTION 1

MCP: Mono Calcium Phosphate. xHydrate

Limestone + Phosphoric Acid + Water → Mono Calcium Phosphate. xHydrate + Carbon Dioxide + Water

Note: the value of “x” is between 0 and 1.

2.    REACTION 2

DCP: Di Calcium Phosphate. XHydrate

Limestone + Water+ Phosphoric Acid → Di Calcium Phosphate. xHydrate + Carbon Dioxide + Water

Note: the value of “x” is between 0 and 2.

The main side reactions are associated with Magnesium Carbonate, as shown:

3.    REACTION 3

4.    REACTION 4

The other side reactions are not significant.

5.    PRODUCTION PROCESS

The process is divided into the following steps:

·         Preparation of limestone slurry;

·         Reaction of limestone and phosphoric acid;

·         Granulation and aging of the MCP;

·         Drying and classification of the MCP;

·         Environmental control;

·         Recycle system and control;

The plant will normally be supplied with a ground Calcitic CaCO₃, with a minimum fine of 80% passing 75µ. This limestone will be supplied in bulk pneumatic trucks, received in the main storage silos.

The ground limestone is transferred from the main silos to the smaller feed hopper using a pneumatic dense phase transfer system.

The limestone is metered out of this small feed hopper using a rotary valve and belt conveyor to the slurry tank.

The slurry is produced in stirred tank, which is equipped with baffles, agitator and recirculation pump. The limestone is metered into the minimum volume of process water, agitated and recirculated, passing through a strait tube mass flow meter. The solids concentration and, consequently, the calcium flow, are controlled on the slurry density.

This suspension is prepared initially using process water and, as the operations pass from the preparation stages to continuous production, this is substituted by the bleed from the reaction system scrubber.

When the limestone slurry has achieved the correct density and concentration, the feeds are put onto automatic, with the limestone feed controlling the addition of the scrubber liquor/process water.

At the same time as the continuous feeds are started to the preparation tank, the pump is switched from the recirculation loop to the feed to the reaction head. In this reaction head, the limestone slurry is reacted with the defluorinated Phosphoric Acid.

The reacting mass discharges directly into the “Spinden” granulator. The sequence of feeds into the “Spinden” is as follows:

·         First the recycle;

·         Second the reaction mass from the reaction head

This area of the production unit is the only part which has a wet scrubber; the gases are mixture of carbon dioxide, water vapor, air and a small amount of particulate material. Since the phosphoric acid and the limestone are basically without fluorides, there is no problem with using the scrubber liquor to generate the limestone slurry.

Both the speed and the angles of the paddles/pins in the “Spinden” are variable, because of that, it is possible to control the granulation size and efficiency.

The “Spinden” discharges onto the system of “aging” belts before the granulated material is fed into the dryer. These belts serve to harden the granules and complete the reactions.

Note: A MCP or DCP and any phosphatic fertilizer granule strength are directly related to its diameter.

For example the standard granule hardness use granules between 2.36 mm and 2.83 mm – average 2.5 mm. The hardness is directly proportional to the square of the diameter.

If the hardness of a 2,50 mm granule is 3,0 kgf/cm², then a granule of the same product at the same moisture content with a diameter of 1,25 mm will have a hardness of (1.25/2.5)2 x 3.0  = 0,75kgf/cm2

The dryer is a conventional co-current directly heated rotary drum.

The dried product is discharged into a bucket elevator, and from there onto the screens. The oversize is sent to the chain crushers, the fines and some of the small product are also returned to the recycle. The recycle control system is based on the use of different screen meshes on the inlet and outlet sections of the lower screen deck.

The gases ex-dryer are treated first by high efficiency cyclones and then by a bag filter.

The product fraction is cooled in the new fluid bed cooler. The advantage of the fluid bed system is that besides cooling the product it also de-dusts it. The exit gases are treated by cyclones and bag filters.

There must be a de-dusting system installed which controls the emissions from the screens, oversize crusher, elevators and the recycle conveyor.

The particulate materials collected and recovered from the three systems of cyclones and bag filters are returned to the recycle conveyor, and consequently to the “Spinden” granulator.

The cooled screened finished product is transferred from the storage silos by means of pneumatic dense phase transfer units to the appropriate packaging units. These packaging’s units weigh the product into 1000kg “IBC’s” or 25 kg plastic sacks.

DCP PROCESS DESCRIPTION

Brief Process Description

Introduction:

Production of powder Dicalcium Phosphate – DCP – is based on the following process and chemistry. It can be demonstrated by the reactions below.  

1.    REACTION 1

DC”: Mono Calcium Phosphate. xHydrate

Limestone + Phosphoric Acid + Water → Mono Calcium Phosphate. xHydrate + Carbon Dioxide + Water

Note: the value of “x” is between 0 and 2.

2.    REACTION 2

MCP: Mono Calcium Phosphate. xHydrate

Limestone + Phosphoric Acid + Water → Mono Calcium Phosphate. xHydrate + Carbon Dioxide + Water

Note 1: the value of “x” is between 0 and 1.

Note 1: The majority of Animal Feed Phosphates are mixtures of DCP and MCP.

The main side reactions are associated with Magnesium Carbonate, as shown:

3.    REACTION 3

4.    REACTION 4

The other side reactions are not significant.

5.    PRODUCTION PROCESS

The process is divided into the following steps:

·         Intake and dosing of the limestone;

·         Preparation of limestone slurry;

·         Reaction of limestone and phosphoric acid;

·         Solidification and “curing” of green DCP;

·         Drying of DCP;

·         Environmental control;

·         Storage and packaging of finished product.

The plant will normally be supplied with a ground high Calciti” CaCO₃, with a minimum fine of 80% passing 75µ. This limestone will be supplied in bulk pneumatic trucks, received in the main storage silos.

The ground limestone is transferred from the main silos to the smaller feed hopper using a pneumatic dense phase transfer system.

The limestone is metered out of this small feed hopper using a rotary valve and belt conveyor to the slurry tank.

The slurry is produced in stirred tank, which is equipped with baffles, agitator and recirculation pump. The limestone is metered into the minimum volume of process water, agitated and recirculated, passing through a strait tube mass flow meter. The solids concentration and, consequently, the calcium flow, are controlled on the slurry density.

This suspension is prepared initially using process water and, as the operations pass from the preparation stages to continuous production, this is substituted by the bleed from the reaction system scrubber.

When the limestone slurry has achieved the correct density and concentration, the feeds are put onto automatic, with the limestone feed controlling the addition of the scrubber liquor/process water.

At the same time as the continuous feeds are started to the preparation tank, the pump is switched from the recirculation loop to the feed to the reaction head. In this reaction head, the limestone slurry is reacted with the defluorinated Phosphoric Acid.

The reaction products are discharged directly into the vertical turbine mixer. This mixer discharges on the reaction belt den, were it solidifies forming an “apparently dry porous cake”.

This area of the production unit is the only part of the system which has a wet scrubber; the gases are a mixture of carbon dioxide, water vapour, air and a small amount of particulate material. Since both the raw materials are basically without fluorides, there is no problem with using the scrubber liquor to produce the limestone slurry.

The reaction belt den discharges onto the dryer. This dryer have the internal flights designed to this type of solids. At the same time, the furnace has the thermal capacities designed to evaporate all the water.

The gases from the dryer are cleaned as they pass through the cyclones and the new bag filters.

The dry DCP is discharged onto the belt conveyor which in turn, discharges into the screw conveyor. The screw conveyor also receives the solids from the new de-dust system. This system consists of a bag filter and screw conveyors.

The main screw conveyor discharges into the new bucket elevator which in turn, discharges onto a series of belt and screw conveyors. These conveyors feed the storage silos. The packaging units are gravity fed from the product storage silos. These packaging units weigh the product into 1000kg “IBC’s” or 25kg plastic sacks.