FR2518532A1 - Fertiliser prodn. from sewage sludge - uses continuous proportioning and mixing of sludge with additives to produce crumbs of prod. - Google Patents

Abstract

Prodn. of fertiliser from sewage sludge comprises adding rock wool and lime or other cpd. fertiliser to ground dewatered sludge pref. at about 20% solids content. The constituents are mixed continuously and homogenised by extrusion under pressure through an adjustable orifice before being broken up into crumbs suitable for spreading on the land. Used for prodn. of a compound fertiliser esp. from sludge contg. up to 80% moisture; the process produces material which is much easier to spread than the dewatered sludge on its own.

Description

 The subject of the present invention is a new process for the production of continuous compost, using sludge from the treatment of waste water, coming from treatment plants, in particular urban sludge produced by filtration or centrifugation.

 The subject of the invention is also the new industrial product which constitutes an installation for the implementation of the process, convoy to the invention.

 The generalization of the purification of domestic wastewater leads to the production of significant quantities of sludge, which, depending on the equipment of the treatment plant, is in the form: liqui 5% on average dry matter, pasty, 20% on average of solid matter, 40% on average of dry matter.

 Liquid sludge can easily be spread in c with the equipment used for slurry, the present invention can use: this type of sludge.

The pasty sludge comes from liquid sludge to which a polyelectrolyte has generally been added, to cause flocculation
They are sticky, their handling is difficult, their spreading is sorted irregularly, the manure spreaders clog up quickly, so almost all of this sludge is landfilled, despite a certain agronomic value. The present invention is particularly suitable for using this type of sludge.

 The solid sludge comes from liquid sludge cooked and press or dried on a drying bed. They are easier to handle and spread than pasty sludge, the present invention can also use this type of sludge.

Processes that use pasty sludge, such as the process
Triga and the BAV process, which have been in existence for 4 years as a prototype, could not be generalized.

 The Triga process uses a vertical tower divided into four vertically. A mechanical device allows extraction from the bottom of each quarter independently.

 A carbonaceous product is roughly mixed (sawdust, bark, straw, etc.) 2/3 by volume to around 1/3 of sludge. The product obtained is brought to the top of the tower Every day it is recycled by extraction at the base for homogenization and aeration and brought back to the top.

 This operation is carried out for a minimum of 12 days, the drawback of this installation is its low speed, compared to the investment and operating costs.

The BAV process differs from the previous one. The tower has no
interior divisions, the aeration of the substrate is carried out using
air blowers that pulsate through the mass. This principle does not allow
not homogenization. We find in more important, the disadvantages
of the TRIA process.

This new sludge treatment process, in accordance with the invention
has the advantage of allowing the use of sludge, in particular
pasty sludge, without necessarily having to resort to composting.

This process allows direct rational composting
for a specific agricultural use.

11 installation according to the invention intended to implement
the process includes feeding from a combination of means or
transport, preparation and distribution devices for the product
carbonaceous (sawdust, bark, straw etc ...) to a blender.

A set of means or devices to put, by addition
suitable elements, the carbon support under the required conditions
to obtain the agronomic characteristics determined by use
substrate.

 A set of means or devices for adding the laminated sludge to the carbon support at the chosen doses.

A set of means or devices allowing the mixture obtained
to perfect its homogenization, followed by a device allowing aeration
and crumbling.

The advantages of the invention will appear better on reading
the description that follows.

Figure I shows schematically an installation for
the implementation of the method according to the invention.

According to the intention, we prepare first, If necessary
the carbon product (eg bark). Item I represents a box or
storage hopper, at its base a scraper belt comprising two chains of
traction and scrapers to bring the product to a conveyor device
(post 3), Carpet, screw, chain with buckets or other systems. Station 2
represents a flow control obtained by an adjustable opening, which
with the variation of the progress of the scraper belt of the main box
ensures the regularity of a constant flow.

Item 4 represents a grinder, the latter must be adjusted
so as not to grind too finely, in order to avoid the production of dust
however, the section of the pieces must be a maximum of around 100 = m2.

 The output of the crusher communicates with a control device: supply stations 5 and 6 with identical characteristics, to the diagram described in station I and 2, but its size may be smaller.

 This station is arranged to directly receive supports that do not need grinding, such as sawdust.

 the carbonaceous material is entrained at constant flow rate in the open twin screw mixer Post 7. The diameter and the pitch are advantageously of minimum dimension, the speed of rotation facilitating homogenization.

 Station 8 can optionally incorporate a material intended to modify the physical characteristics of the basic carbonaceous material, for example supply of rock wool, conditioned in small particles to improve the water retention of the substrate.

 Station 9 distributes the mineral elements necessary for chemical co: tions: example N.P.K CaO to name only the most common, either in solid form or in liquid form.

 Then is brought into the mixer, the mud stored in the station IO by means of an endless screw, station II placed about two meters from the outlet of the mixer. The mud is pressed on a perforated grid which divides it and distributes it in the form of a cylinder with a diameter which must not be less than 10 mm, below, the risks of blockage would be significant.

 The double mixing screw moves all the ingredients at a constant speed and pours the mixture obtained into a continuous press station I2 which causes a homogenization of the humidity, essential for the direct use of the substrate.

This press is advantageously of the continuous type, a wine press whose perforated grids have been replaced by flat surfaces.
The homogenization adjustment is obtained by a post plate slowing down the evacuation. At the exit of the press, a device of emietta station I4, constituted by hedgehogs, rotating at a speed of 300 to 500 revolutions per minute.

The substrate obtained is removed by a post conveyor belt
The mixture is left in a heap for 48 hours minimum, to perfect if homogenization, then, depending on its composition, it can either be used directly by common agricultural implements, or put into composting or even dehydrated.

 The advantage of such an installation lies in its continuous operation and the possibility of modifying the composition of the mixture at any time, allowing a trams great flexibility in the possible formulas.

 without going beyond the scope of protection.

Claims (1)

CLAIMSSI) Continuous compost manufacturing process using sludge from wastewater treatment, from sewage treatment plants, especially urban sludge produced by filtration or centrifugation, characterized in that: a) A first station possibly prepares the product carbonaceous and ensures continuous feeding in a mixer. b) A second station ensures the possible addition of additional ingredients.  c) In a third station, addition of possibly lime sludge.  d) In a fourth station, all of the components after mixing are homogenized by pressure.  e) In a fifth station the product mixture is at the outlet of the crumbled press. 2) A method of manufacturing compost according to claim I, characterized in that each element has settings which allow it to feed continuously, at determined doses, the manufacturing plant.  3) A method of manufacturing compost according to claims I and 2 characterized in that the carbon products receive & s solid or liquid supplements to improve their physical and / or chemical characteristics. 4) A method of manufacturing compost according to any one of claims I to 3 characterized in that the carbon support is mixed with physical and / or chemical supplements solid or liquid before receiving the sludge. 5) A method of manufacturing compost according to any one of claims I to 4 characterized in that the pasty or solid mud is introduced after rolling which causes sticks having a section of IOOmm minimum, avoiding the formation of large lumps. 6) A method of manufacturing compost according to any one of claims I to 5 characterized in that the mixture is pressed to homogenize the moisture. 70 A method of manufacturing compost according to claim 6 characterized in that the substrate is crumbled at the outlet of the press. 80 A method of manufacturing compost according to any one of claims I to 7 characterized in that the installation makes it possible to produce a substrate with predetermined characteristics.  9 A method of making compost according to any one of claims I to 8 characterized in that the product obtained is intended to be used as it is or put in composting or even dehydrated.