ITFG20080004A1 - TREATMENT FOR ANAEROBIC DIGESTION OF VEGETATION WATERS BY FRANTOIO OLEARIO AND SANSE DA MOLITURA OF OLIVES AFTER EXTRACTION FROM THE SAME AS THE POLYPHENOLIC FRACTION, MILK SERUM WITH BIOGAS PRODUCTION AND COMPLE FERTILIZERS - Google Patents

Description

DESCRIPTION

1. GENERAL

The agro-industrial processing industry generates a series of by-products that still have residues of valuable substances: current technologies do not always allow their recovery and use.

These by-products are therefore treated as highly polluting waste that generate high costs for their disposal with high risks of environmental degradation.

Some extraction technologies allow a partial recovery of substances used for example in the food sector (whey from whey, antioxidants from vegetation waters, etc.): this lowers the polluting load of the starting matrices, but does not eliminate the cost of disposal final residue and environmental risk.

The present work presents an integrated technology (ie made of a process line within which various unitary operations are implemented) which determines a total reuse of the residual fractions from the processing of milk and olives as described below.

The pressing of the olives and the processing of milk generate food oil, dairy products and two matrices;

-waters of leaves pomace vegetation

- whey

These two fractions are well identified in industrial practice due to their microbiological and chemical-physical and chemical characteristics.

INTERVENTION ON THE WASTE OF OIL PROCESSING

The waters of vegetation, pomace and leaves are subjected to the extraction of some valuable components

-sanse extraction in aqueous phase and separation of organic components:

polyphenols (oleoeuropein), dyes

-waters of vegetation membrane filtration and separation of polyphenols including redroxytyrosol and other components of commercial interest -leaves extraction of oleoeuropcin and antioxidants

These two fractions (vegetation waters, sanse, leaves) derived from the processes described above are now devoid of valuable components; however they retain a very high organic and mineral load such as to determine very high costs of reducing the polluting load to make them eligible for unloading; the alternative of the transfer to treatment centers also gives rise to high transfer costs.

The use of pomace as a fuel appears uneconomical as the high humidity rate (greater than 50%) drastically lowers the available thermal energy of combustion (lower calorific value).

In recent years, two-phase centrifuges have been developed for the separation of oil from pomace and vegetation water: with this technology, the two fractions are obtained as a single substrate with a humidity ranging from 60 to 80%.

The advent of two-phase centrifuges makes it even less convenient (due to the high level of humidity).

The extraction of polyphenols and dyes no longer takes place from individual substrates (vegetation waters and pomace) but on the single substrate.

In the two-phase centrifugal process, therefore, after the gramming, two fractions are obtained;

-oil

-mix of vegetation waters and pomace.

From the extraction of olcoeuropein from the leaves there is also a solid and therefore scarcely usable fuel.

INTERVENTION ON WASTE FROM DAIRY PROCESSING

The whey, a by-product of milk coagulation and the manufacture of cottage cheese, is subjected to separation of the protein fraction (WPC).

The residue can be subjected to concentration and crystallization of lactose for various industrial and pharmaceutical uses.

The final residue still contains a high polluting load and a high saline content which requires a high purification cost for discharge according to law.

FINAL INTERVENTION

The wastewater deriving from the recovery operations described above or alternatively used as it is without recovery operation are used for:

- “anaerobic digestion” for the production of biogas

- separation and concentration for the production of liquid and solid fertilizers

2. DESCRIPTION OF THE PRODUCTION TECHNOLOGY

BIOGAS (mixture of methane, carbon dioxide and minor gases) The process refers to a standard composition of vegetative waters, leaves and whey (substrate); pomace and vegetal waters can be obtained separately or (as in the case of two-phase process) in mixture.

The composition of the various fractions vary according to:

- oil extraction technique

- variety of olives

- collection period

-degree of treatment for the extraction of hydroxytyrosol, polyphenols, dyes, etc.

-typology of milk (sheep no. cow, goats no.,}

-technology of milk processing (production of filata pasta, grana, production of ricotta ccc ..)

-technologies for recovering protein and sugar fractions from serums

However, the variability of composition does not change the treatment technology and the peculiarities of the technological solutions; it only modifies the mass and energy balances of the system:

- biogas produced per treated weight unit

-energy spent on mass transfer

- times of hydraulic and biomass retention

The process refers to a standard composition referred to average values as defined by the scientific literature and to the substrates actually used for the tests.

The parameters taken into consideration are those significant for the anaerobic digestion process and for the production of fertilizers

2. composition

Note: in the case of a two-phase extraction process, the substrate will have a weight average composition of the two separate substrates; the variations concern only the water content

2, There is anaerabic digestion

Anaerobic digestion is a process involving liquid or semi-solid fractions (substrate) on which anaerobic microorganisms grow (they live in the absence of oxygen): as a result of this microbial activity, the organic substance is degraded and methane and other gases are produced. minor (carbon dioxide, hydrogen sulphide, hydrogen sulphide.

These microbial reactions take place in reacors of various sizes, single-stage or multi-stage, in the absence of air and in a range of very fluid dynamic conditions;

-temperature from 30 to 60 ° c.

-pH from 5.0 to 8.5

- Agitation: energy dissipated by 0 - 0.6 kwh / mc reactor / hr

The process in question was carried out on a two-stage reactor.

The first stage is characterized by biochemical reactions that lead to the reduction of molecular masses through enzymatic hydrolysis of complex substances (cellulosic and polymeric and organic molecules with high molecular weight) and acidophilic reactions with the formation of simple substances; this stage is characterized by the formation of low molecular weight organic acids (acetic, sueemieo, proptonico, etc.).

The second stage is defined as "methanes" as a microbial flora is established using the low molecular weight organic acids formed in the previous stage, to:

"Biogas".

The relationship between the first and second reaction stage is of fundamental importance for the running stability of the process * in the second stage in fact the biochemical reactions of methanization are characterized by the transformation of short-chain acids into methane: this reaction is disadvantaged from the point of thermodynamic view as in "standard" conditions <5> it has a variation of POSITIVE FREE ENERGY "(AG); therefore the reaction does not occur spontaneously; to make it happen, the level of acids must be kept low; this means that the production speeds of the acids in the first acid stage must be compatible with the utilization rates of the acids themselves in the second stage (methanization).

A great importance is therefore assumed to the bacterial activity of the two stages and to the inhibition factors that exist in the substrate.

For what has been said, the process technology resulted from in-depth research on a laboratory scale and on a pilot plant aimed at:

- isolate and characterize "pool" of microorganisms adapted to the conditions of inhibition of the substrate (eg: presence of polyphenols)

- identify the organic load factors per unit of time and reactor volume - identify the pH and especially the temperature conditions of the reactors

- identify the hydraulic retention and biomass retention times

2.d-results

The biological process determines two substantial variations to the L system

■ 'Reduction of the organic load

-production of biogas

2. e- reduction of organic load

The reduction of the organic load represents the amount of substrate used for the production of BIOGAS,

The abatement is usually measured through two parameters;

-variation of volatile solids (SSV)

- change in COD

Since the substrate is a suspension of water, vegetation / pomace, it was considered appropriate to measure Γ abatement in terms of the variation of volatile solids.

This value was around 60% of the initial value.

2.f-biogas production

The biogas produced is a mixture which on average is expressed by the following composition:

The above values can have a wide variability.

Mc Carty's theoretical model

For each substrate object of the various tests a theoretical yield was calculated by applying the McCarty equation starting from the following data:

- elementary composition of the substrate: C, H, Q, N

-volatile solids (SSV)

to. model based on elementary composition

the! McCarty model which correlates biogas production to the elemental composition of the substrate;

s <~> fraction of COD used for bacterial synthesis, expressed as molar ratio e = theoretical conversion fraction between COD and methane expressed as molar ratio (0.5) d - 4n + a-2b-3c

b.modelio based on the COD

the conversion factor is:

V (/ oi>, CTM * 0.25 kg CH ^ kg COD degraded

c. model based on volatile solids

A COD-SSV conversion value equal to 1.2-1.5 is assumed:

1 kg of SSV = 1.2-1.5 kg of COD

This allows to develop the calculations of the productivity in biogas in terms of COD It is accepted that 60% of the SSV loaded in the digester will be transformed into biogas By applying the forecast models above and the experimental data obtained on the pilot plant, the following conversion yields have been assumed :

1 kg of SSV eliminated = 0.57 - 0.80 CHU rhymes

For biogas with 65% methane we have:

lkg of SSV eliminated = 0,87-1,23 runes of biogas

Starting from the McCarty equation, the theoretical productivity of methane are much higher:

vegetation water productivity nmc / methane / kg SSV shot down - 0.70 (max value) pomace productivity nmc / methane / kg SSV shot down - 0.80 (max value)

In reality, in plant engineering practice we have approached these theoretical values, and in certain experiences we have gone below the average values

We can therefore identify a real productivity rank for each substrate.

If we indicate

At SSV concentration of water vegetation% unitary

B quantity of vegetation water kg

a ~ 0.57 specific productivity AV frogs biogas / kg SSV culled C SSV pomace concentration% unit

D pomace quantity kg

β = 0,65 specific productivity pomace rune biogas / kg SSV killed (A + B) total substrate

Biogas produced runes = (A x B x 0,6 χ α) (C x D x 0,6 x β)

The 65% methane BJOCAS produced will fluctuate by a value of / - 50% with respect to the average values

vegetation water nmc / methane / kg SSV shot down = 0.285-0.855

pomace ume / melano / kg SSV shot down - 0.325-0.975

In the case of substrate obtained from a two-phase process and therefore a mixture of (pomace vegelation water) the results do not change in terms of Biogas productivity; only the amount of aqueous residue at the exit of the digester is changed.

2 g4! «Nversifme chemical energy - electricity

The biogas produced with 65% methane powers an internal combustion engine for the production of electricity.

We collect the following data:

Electricity is fed into the network.

Thermal energy is used for:

- keep the digester at the temperature

-for drying processes of fluids leaving the digester and destined for subsequent treatment for the production of fertilizers.

Therefore the fluids involved in the combustion and produced by it have been characterized as elements that enter into the projects of downstream exchangers.

Vbi rnne / hr biogas volume

Cii% v / v unitary other gases

CU ll2 + 02 + NHj + I i2S = 0.05 (PMra = 7

CCCGL% v / v unit initial carbon dioxide

Crmju.n% v / v initial methane unit

A fraction of oxygen required referred to methane

B fraction of nitrogen required referred to methane

C fraction of carbon dioxide formed referring to the initial methane D fraction of water formed referring to the initial methane

Calculation of the percentage position cones

Calculation of specific heats

The specific heats are calculated from the weighted average of the specific heats of the individual components (valid for ideal gases) -In first apprns.sima7.ione the average specific heats are considered in a temperature range between 50 and 300 3⁄4

Specific heat WET COMBUSTION GAS * 0.273 cal / gr ° c

Specific heat DRY COMBUSTION GAS <»> 0,251 cal / gr ° c

Calculation of masses

Kg of gas / burnt biogas frogs

Mass before combustion kg / rnne biogas 9,950

Wet burnt mass kg / nmc biogas 9,950

Dry burnt mass kg / nmc biogas 8,895

Kg of water / nmc of burned biogas kg / nmc of biogas 1, 055

The fermented substrate coming from the anacrobial digestion is filtered on a belt press or on a filter press; then the two fractions are separated:

-liquid

-solid

Liquid fraction

The liquid fraction contains essential elements for soil fertility and in particular contains in soluble form carbon and nitrogen largely of biological origin: this greatly increases the fertilizing value of the product.

The liquid fraction contains the basic elements of fertility:

-soluble phosphorus

- soluble potassium

-soluble microelements

The liquid fraction is concentrated with a reverse osmosis process made with tubular membranes. Subsequently, in order to reach the concentration envisaged by the Legislative Decree of 26 April 2006 N ° 217 of the Italian Republic, a final thermal concentration on the evaporator is carried out. The final product is:

NPK organic mineral fertilizer

Title 12% (N + P205 K20) 3.0% organic carbon

Additions of substances based on Ν, Ρ, Κ are possibly to be foreseen to reach the title.

Reference Legislative Decree N <e> 2l7 / 2D06 Section 6.4.1: at least 2% mineral and 0.3% organic.

Solid fraction

A partial reduction of humidity is carried out by heat treatment on the evaporator. The final product is:

NPK organic mineral fertilizer

Title 15% (N + P205 K2Q) 7.5% organic carbon

Possible additions of substances based on Ν, Ρ, Κ to reach the titol are foreseeable. Reference Legislative Decree N ° 217 / 2QQò Comma 6.4: Nitrogen must be at least 3% mineral and 1% biological.

Table 1 shows a flow diagram of the process with a heat exchange system for maintaining the process temperature.

Formulations with different fertilizer unit concentration can be envisaged: this is achieved by varying the concentration process of the liquid or solid matrix.

COINCLUSIONS

The proposed treatment finds an effective placement in the wastewater of the oil industry after the extraction from the latter of the polyphenol fraction. This extraction, although now not very widespread, promises to achieve significant results over time, thus generating a type of highly polluting wastewater. With the treatment for anacrobial digestion and the transformation of digested products into fertilizers of high agronomic value, each liquid and solid phase of the waste originating from the oil mills is effectively recovered, with a further added value: the biogas produced by the process is also recovered, for the production of electricity from renewable sources.

The value of fertilizers is described by various agronomy scholars who above all highlight:

-the soluble or solubilizable form of the fertilizing principles

- the presence of carbon and nitrogen of biological origin

-the presence of organic substance useful for the conservation of Humus in the soil

- the presence of growth factors (ÌJG1 = unkaow growt factor) which derive from bioactive peptides, amino acids, vitamins, etc. typical of the starting substrate or which are formed during the fermentation process of anaerobic digestion

-Tel evala conditions of health safety as the substrates derive from thermophilic fermentation

Many authors who study natural systems and the global impact of industrial activity on the ecosystem highlight:

- the production of natural fertilizers cause a slowdown in the use of chemical fertilizers: the synthesis of the latter lead to extremely high pollution conditions

- The use of chemical fertilizers (nitrates, phosphates ..) has led over the years to pollution phenomena of groundwater, waterways and the sea (eutrophication phenomena)

- the use of chemical fertilizers has determined a decrease in the fertility of the land as they unbalance the chemical / biochemical composition of the soil (humus impoverishment) with a decrease in production yields so that you are forced to increase the fertilization doses during the course Some years. The fertilizer production system proposed in this paper opens up a new production scenario, also extended to other wastewater from the industry; the quantities involved can be significant, such as to replace a substantial percentage of the Firn

chemical fertilizers.

Claims (1)

CLAIMS 1 (Substrate to be used for anaerobic digestion, in which they are present at various percentages (from 0 to J 00%}: - residual from water extraction treatment of vegetation and pomace coming from oil mills of polyphenolic fractions, with any technology these extractions are carried out - residual from the whey and lactose extraction treatment of whey 2} Composition of the substrate referred to in the previous point 1}; 0-100% vegetable water-Q-100% pomace - 0- 100% whey 3) Digestion reactor of any shape and size. 4) Reactor d! single or multi-stage digestion including Plug Flow 5) Operating temperature of the digester from 30 to 60 ° c 6) Production of liquid fertilizers from the substrate deriving from the filtration or separation in any way performed of the fluid leaving the anacrobial digester; subsequent concentration with thermal evaporation c / o membrane process and integration of the fertilizing principles (organic N.PJC.C) to standardize the title to the prefixed values. 7) Production of solid fertilizers from the substrate deriving from the filtration or separation in any way performed of the solid leaving the anaerobic digester: thermal concentration (evaporation) and integration of the fertilizing principles (N, PJ £, C organic) to standardize the title a prefi ssatL values 8) use of reactor formed by osmosis separation elements, combined with final stage of thermal evaporation of any shape and size for the production of liquid fertilizers. 9) Use of a reactor formed by elements for heat exchange for the dehydration of the solid fertilizer; the heat exchange takes place by direct gas / fertilizer contact (evaporation by humidification of the gas) and / or with indirect heat exchange between fertilizer and an energy carrier in any way (eg: creation of a heat exchange wall between a fluid heat and fertilizer).