Portfolio

PFR Kilns for soft-burnt lime


THE PFR KILNS FROM MAERZ. EFFICIENT PRODUCTION OF LARGE QUANTITIES OF BURNT LIME.

The Maerz PFR-Kiln

A PFR kiln (parallel flow regenerative shaft kiln) consists of two vertical shafts and a connecting crossover channel. Both shafts work with each other. While one calcines the product, the other preheats the stone. In the burning shaft the lime is calcined in parallel flow. The hot combustion gases are then transferred through the crossover channel to the non-burning shaft where they preheat the limestone in counter flow in the upper area of the shaft. The flow direction of the gases is reversed at regular intervals. This allows the regenerative preheating of the stone to take place (the stone in the preheating zone of the kiln acts as heat exchanger) and thus for the maximum use of the heat contained in the kiln gases.
The principle of calcination in parallel flow is ideal for the production of high-reactive quicklime. A PFR kiln from Maerz processes up to 800 tons of burnt lime per day. Gaseous, liquid or pulverised solid fuels as well as different combinations of these may be used. Depending on the required output and grain size of the limestone to be processed, Maerz designs rectangular, circular or Finelime® PFR kilns.


PFR KILNS – TECHNICAL DATA.
KILN TYPES RECTANGULAR
PFR KILN
CIRCULAR
PFR KILN
FINELIME® KILN
KILN TYPE E1 – E6 R1 – R5 F1 – F3
CAPACITY
(tons per day)
100 – 400 300 – 800 200 – 400
RAW MATERIAL
GRAIN SIZE

(mm)
30 – 120 30 – 160 15 – 40
HEAT CONSUMPTION
(kJ/kg)
(kcal/kg)
3390 – 3650
810 – 870
3390 – 3650
810 – 870
3310 – 3560
790 – 850
MAIN PRODUCT High-reactive
quicklime
High-reactive
quicklime
High-reactive
quicklime

THE RECTANGULAR PFR KILN FROM MAERZ. FOR UP TO 400 TONS OF BURNT LIME PER DAY.

The Rectangular Maerz PFR KilnThe most cost-efficient and simple design of a PFR kiln: two burning shafts with a rectangular or hexagonal cross section are placed next to each other. Through a direct crossover channel the combustion gases flow from one shaft to the other. The rectangular cross section simplifies the fabrication of the kiln by imposing fewer challenges on the steel construction and the refractory material. This simple and cost-efficient PFR kiln is usually used for outputs of up to 400 tons of burnt lime per day.
Since 1966, Maerz has installed more than 200 rectangular PFR kilns worldwide.

 

 


THE CIRCULAR PFR KILN FROM MAERZ. FOR UP TO 800 TONS OF BURNT LIME PER DAY.

The Circular Maerz PFR KilnFor the production of larger capacities of burnt lime per day (300 to 800 tons) Maerz recommends PFR kilns with a circular design. These kilns have a circular shaft cross section and circular ring channels for gas flow. In these channels the combustion gases of the burning shaft are collected before flowing through the crossover channel to the non-burning shaft. In the non-burning shaft the hot gases in turn flow through the circular ring channels along the whole circumference of the shaft. The circular shaft cross section and the gas distribution along the whole circumference of the shafts ensure an even heat distribution in large kilns – indispensable for high lime quality.
Since 1966, Maerz has installed more than 300 circular PFR kilns worldwide.


THE FINELIME® KILN FROM MAERZ. SO YOU CAN MAKE BETTER USE OF YOUR LIMESTONE DEPOSITS.

The Maerz Finelime® KilnLimestone that is calcined in conventional shaft kilns usually has a grain size of more than 40 millimetres. Smaller-grained stones, not more than 6 to 50 millimetres in size, are often calcined in rotary kilns – which, however, feature very high heat consumption. To solve this problem, Maerz developed a highly specialised PFR kiln: the Finelime® kiln.
How does it work? The special geometry of this kiln and the special charging of the feed material guarantee ideal heat distribution, even when processing small-grained stone.
The principle of the PFR kiln, i.e., the calcination of lime in one shaft and the preheating of the stone with the hot kiln gases in the other shaft, is also used in the Finelime® kiln. Thus its heat consumption is significantly lower compared to rotary kilns.
Since 1989, when it was first introduced onto the market, Maerz has installed approximately 60 Finelime® kilns worldwide.