Updated: July 2002

1. Purpose

Sludge left over sewage treatment facilities is disposed of at landfills in the form of de-watered sludge or incinerator ash. However, with fewer and fewer landfill disposal sites left, it is indispensably necessary to utilize ash as a resource as much as possible.
This innovative process produces colored water-permeable paving bricks by mixing incinerator ash with aggregates such as crushed debris or porcelain scraps and then molding mixed materials into shape and baking then in a kiln.
Product bricks are mainly applied to sidewalks, community squares, swimming pool sides, and anywhere else needed beautiful paving.

2. Features

To mix aggregates with ash has several advantages in terms of facility design:
1) Bricks can be baked at a constant temperature even if there is the fluctuation of ash composition.
2) Bricks are uniform in size, which minimizes production loss.
3) The molding requires the smallest time and pressure. The bricks produced by this process have the following significance in the protection of environments.

(1) Since the bricks are highly porous, the quality of permeability allows rain water to seep through and into soil, resulting in more water supply to the roadside vegetation and to the subterranean water and less rain water flowing into the sewage system.
(2) Since ash is fused and vitrify through high temperature baking process, heavy metals contained in the ash are well confined in the bricks and never exude after application in the pavement.

3. Process Description

Besides the permeability, the bricks have received good reputation for their coloring effect. This process consists of a series of equipment to form the bricks into units with a two-layer structure for greater color variations by coloring the surface layer.

Analysis of Ash
Ash gets classified according to its melting characteristic. The mixture percentages of ash and aggregates are determined, respectively, in order to proceed baking at stable temperature. This results in the constant operating conditions and the stable quality of products.

Weighing
According to the pre-fixed classification patterns, all ingredients are automatically measured by the computer system.

Kneading
Mixed materials are kneaded into granules.

Molding
Granular substances (two kinds; one for base layer and other for colored surface layer) are molded into a two-layer structure under the pressure of less than 20MPa.

Baking
The molded bricks are put into a tunnel furnace, and are baked at around 1,100º Celsius.

Palletizing
The finished water-permeable bricks are loaded onto pallets for shipping.

4. Figure (Flow chart)

Feedstock storage -> Automatic weighing -> Kneading/Granulating -> Molding -> Baking -> Palletizing

5. Typical Specifications

Sewage sludge ash: 300t/month (dry base)
Produced bricks: 6,500m²/month (325,000 pieces)
Operation:
Tunnel kiln Continuous 7d/week
Other equipment 8h/d×5d/week
Brick size: 198mm×98mm×60mm

6. Example of Installation

F tile manufacturer
"Water-Permeable Paving Brick from Sewage Sludge Ash"