FR2466502A2 - Manure fermentation plant producing methane and deodorised fertiliser - using aerobic pre-fermenter and anaerobic vessels with controlled temps. and agitation - Google Patents

Abstract

Parent patent described a plant installation for deodorising organic waste, partic. pig manure, by a fermentation process which produces methane fuel gas and an agricultural fertiliser. In this addn. one or more aerobic prefermenters are now employed in series with a number of anaerobic fermenting vessels all delivering gas to a common gasometer. A prefermenter is pref. fitted with a heat exchanger. The anaerobic fermenting vessels are pref. provided with independent heat exchangers to maintain a pref. upper substrate temp. of about 35 deg.C. Each anaerobic vessel pref. has facilities for agitation both mechanical and by recycled gas, as well as for recirculation. Greater flexibility of operation and higher over all efficiency are obtd. In particular, the liq. manure can now have additions of chopped and pre-mixed grass, turnip-tops, leaves potato haulm etc. with such mixts. it is possible to treat a given amt. of manure in a reduced vol. of fermentations plant.

Description

 The purpose of this certificate of addition is to supplement the inventvor. The patent application was filed on September 3, 1979 under No. 79.21976 "Deodorization and enhancement plant for orgasmic waste by fermentation".

 The purpose of this diaddition certificate is to optimize the deodorization of fermented substrates and the production of fuel gas.

This goal is achieved by the implementation of P prefermentors and N anaerobic fermenters, resulting in the following advantages
I) at the level of agitation and homogenization increasing the margin of safety, proliferation of microorganisms increased by a better division of organic matter.

 2) make it possible to compose, upstream of the installation, a substrate from not only pig slurry or any other agrifood fluent, with the addition of skulls, grass, tree leaves, straw; and various organic materials previously mixed and dilacerated.

This mixture allows to obtain a better thermogenesis at temperatures was between 40 and <0 C with recovery of calories, to measure the percentage of materials -seches necessary for a good fermentation of 6 to 25%.

 39) to vary the temperatures, according to the needs, plans each of the anaerobic fermenters. This technique can lead to a reduction in the volume of vats, by reducing the hydraulic retention time.

 40) to vary the input volume of the fresh substrate according to the results obtained.

 30) to recycle sludge from the anaerobic fermenter 24 into the anaerobic fermenter I7 to increase gas production and promote organic matter consumption.

 The whole installation works in liquid medium and continuously.

 This goal is also achieved through the operations described and illustrated with reference to the accompanying drawing by way of example.

 The "single figure 1 represents the general principle of an installation.

 Depending on the quality of the substrate we can use P aerobic pre-fermentors and N anaerobic fermenters, take the case of wood products. The prefermenters include a heat exchanger, which can be used for the recovery of calories, but as a heater of the substrate freshly fed by the boiler. The anaerobic fermenters are equipped with stirring system, a device with adjustable mouths recycling the mass in fermentation and a circulation pump. A heating system, connected to a boiler, maintains the temperatures of 35 to 500C. The operating temperatures may be different between the fermenters.

 With regard to the treatment of pig manure and agro-food effluents, the installation described below may be recommended. It consists mainly of a raw slurry storage tank, a dilacerator pump, a pre-fermenter and three anaerobic fermenters, a stirring system, recirculation and heat exchangers.

 The raw slurry stored in the pit 1 is kept homogeneous by hydraulic agitation, a macerator pump ensures a constant ganulometry. By a bypass system, the same pump 2 feeds the aerobic pre-fermentor 3 equipped with a heat exchanger 4 connected to the boiler I2, it can have two functions, either heat recovery or preheating of the raw slurry to facilitate the start of aerobic fermentation. The air necessary for the pre-fermentation is provided by a porous material or a nozzle powered by a booster 5. The heat-insulating preferment can be covered with direct venting to the atmosphere 6.

 After the exothermic fermentation, the material at a temperature between 35 and 650C is directed to the base of the first anaerobic fermenter 7 equipped with a heating system 8 to maintain the fermentation temperature between 35 and 300 C. The invention makes it possible to maintain in this fermenter a different temperature than the second fermenter. The internal circulation of the heating system is provided by the pump 9. The recycling IO of the fermenting liquid is permanent and at a high flow rate, the pump II performs this function. To maintain the totality of the moving mass, the orientation of the recovery mouth is a function of the quality of the substrate. The suction is at the base of the fermenter 7 and then the liquid passes through the heat exchanger 8 to be heated and returns to the top of the fermenter under the blades of the central stirrer I3. Additional agitation can be provided by an Archimedean screw or a bubbling device fed with gas pressurized by the compressor 26. These operations are intended according to the invention, to maintain the homogeneous mass and to avoid the gas pocket formation. The pipe of the heat transfer fluid I4 is connected to the boiler I2, fed with fuel by a relatively small amount of gas produced by the fermentation and stored in the gasometer I9.The base I5 of the fermenter is an inclined plane to facilitate the extraction of the materials. sedimented using pump I6, helicoldal type. Extraction of the fermenting substrate will be done gravitarily at the top of this fermenter 7 to be introduced to the upper part of the second anaerobic fermenter I7. The equilibrium between the volume of the substrate from the aerobic fermenter and introduced into the first anaerobic fermenter g the volume of the substrate discharged to the second anaerobic fermenter I7 is thus ensured. Line I8 of the product gas is connected to the main line I8 supplying the gasometer I9.

 The second anaerobic fermenter 17, insulated, is equipped with a reheating system 8 and a device for recycling IO materials in fermentation, from the first anaerobic fermenter 7. The introduction of recycled materials carried out at the top of the fermenter I7, as before, under the blades of the central stirrer I3.

This fermenter can be equipped with the same additional stirring device as that described for the first anaerobic fermenter 7. These devices avoid the formation of a crust, a gas pocket and reduce the amount of foam. A small flexible gasometer 20 common to the three anaerobic fermenters 7, 17 and 24 is placed on the dome of this second fermenter, to balance pressures within the three anaerobic chambers, and to prevent the introduction of outside air at the time of evacuation. sedimented sludge or any other operation that might alter the level of the fermenting mass. The evacuation of the fermented materials from the second anaerobic fermenter is carried out gravitationally, by a plunging pipe 21 inside the fermenter and whose end is about 7/8 of the height. The evacuated volume is equal to the volume of the substrate from the first anaerobic fermenter 7.

 The residence time of the material in fermentation in the second anaerobic fermenter I7 conditions the volume of the substrate to be introduced into the anaerobic fermenter 7.

 The third anaerobic fermenter 24 is heat insulated.

It receives at its lower part the fermentation substrate from the anaerobic fermenter I7. The transfer takes place gravitationally or with the help of a pump. The maintenance of the temperature, between 35 and 500C is ensured by the passage of the fermenting substrate in a temperature exchanger 8. The operating temperature may be different to that of fermenters 7 or I7. The circulating pump II ensures a fast and constant speed. As in 7 and 17, the return to the fermenter takes place under the blades of the I3 surface stirrer. To promote the homogenization of the mass in fermentation and to prevent the formation of a gas pocket, a device for recycling gas 25, from the pressurized gasometer I9 26 is connected to a nozzle arranged at the base of the fermenter 24 it is the same for 7 and 17. This stirring device can be completed by a stirrer paddle "saber" dipping at in the liquid or by a screw of rchimède, both controlled by an electric motor located outside the enclosure. The base of the fermenter 24 is an inclined plane 15 facilitating the evacuation of the settled materials by means of a screw pump 16. It may be advantageous to recycle a portion of these sludges in 17. The excess is directed towards the storage of the fertilizer.

 As an example here is what can be obtained on a farm of 600 pigs by the treatment of the raw manure.

The dry matter content is 8 to 12%.

 Average weight of a pig: 80 kgs.

Max slurry volume per pig per day: 7 liters
Feeding cereals daily: 2.5 kgs
Dry matter: 20% of material ingested
Organic matter: 80% of 20%
DCO 100 to I20 es
DB0. 40%
N 6 to 736
Hydraulic retention time: 20 days
VOLUME OF FERMENTIERS:
Aerobic prefilter I5 m3
Anaerobic fermenter 7 I8 m3
"" 17 m
"" 24 18 m3
CALCULATION OF ORGANIC MATTER:
Dry matter 20% of ingested material = 500 gr / p
Organic materials 80% of 20% = 400 gr / p
RESULTS:
For 600 pigs 0.400 x 600 = 240 kilograms of organic matter
gas: 60% CH4 and 500 liters per kilogram of material 0.5 mx 240 = I20 m3 per day in kWe I80 kW per day deodorized fertilizer 3 tons per day.

Claims (4)

 I. Process of deodorization and development of organic waste characterized by series use and suc cessfully preform bears and anaerobic fermenters communicating on the same gasometer.  2. A method of deodorizing and developing organic waste according to claim 1 in that the aerobic preferment comprises a heat exchanger.  3. Process for the deodorization and development of organic waste according to claims 1 and 2 characterized in that the fermenters comprise heat exchangers bringing the temperature of the substrate greater than 350C, orientable devices for recirculating the substrate and a device gas recycling.  4. Plant for the deodorization and development of organic waste by fermentation by the process according to claims 1 to 3, characterized in that it comprises aerobic prefermenter and 3 anaerobic fermenters capable of operating at different temperatures and with substrates containing variable percentages of dry matter.