E. Kazarian, Professor at State Engineering University of Armenia, Yerevan:
erkazarian@yahoo. com

Nader Ali. PhD candidate at State Engineering University of Armenia, Yerevan

Practical implementation and successful exploitation of alternative energy sources in Armenia closely related to questions of protection of environment and to increase of life level of the population. Disposal of urban and rural wastes becomes an acute problem for cities and villages of the country. Thus, importance of development of effective and low — cost wastes processing technologies becomes obvious. Ways to increase productivity of small biogas installations are reviewed in the paper.

It is well known that one of the principal stages of organic wastes processing is their oxidation and fermentation. For this stage, the use of electric field is proposed along with heating to induce motion of water component of the disperse mass of the organic wastes in the necessary direction, the proposal is based on the phenomenon of electric osmosis.

Organic wastes were approximated as a system of capillaries filled with solution; the biomass was viewed as a disperse system consisting of solid, liquid and gaseous phases. Upon application of electric filed motion of liquid phase was observed. The direction of the motion depended on polarity of the electrodes. The main parameters were intensity of electric field E, shapes dimensions of the electrodes as well as.

Distance between them. Biogas installation consists of tank with biomass, a measuring and controlling system and power source.

The measuring and controlling system switches on and off the power source, measure the gas temperature, humidity and pressure in various spots of the tank, determines average (per volume) temperature in the tank, changes speed and direction of the liquid’s motion. For simulation of the installation, conductivity of interelectrode space was selected as determining criterion for selection of the speed of motion and fermentation of biomass. The conductivity was represented as (Fig.1)

G = 2prL/ln(R /r) (1)

r — Radius of electrode.

R — Radius of electrode from the wall of

reactor. (The distance between electrode ’axes’ and the wall).

One of which was installed on the tank’s axes while the layer of metal covering the walls of the tank represented the other, L is the length of an internal electrodes.

The length of electrodes and the shape of the internal one were selected, so that the speed of motion of the biomass was the same everywhere in the tank. The density of current on the electrodes was selected according to condition:

r/R = JR/Jr (2)

JR, Jr — a current density of electrodes.

The selected values satisfied to principal conditions, namely necessary speed of the electric osmosis and prevention of excessive heat pollution.

Obtained results made it possible to advise using the installation in small farms.

The large volume of organic wastes from agricultural industry has as a reusable source of organic biomass tremendous energy potential. Availability of biomass alone does not, however ensure a solution to the problem of converting the biomass into an energy source.

It is necessary to have methods both for waste handling and salvaging of a biomass to achieve in optimal conditions biogas for consequent usage to supply electrical power as well as high quality fertilizers.

The system to be described aims to produce biogas from a biomass with out waste products while maintaining ecological clean waste handing, producing gaseous combustible biogas to be converted to electrical and thermal energy and ecological clean organic fertilizers.

For the acceleration intensification and heightening of the fermentation process of a biomass in a Bioreactor the phenomenon of electro-osmosis will be utilized as is exhibited during electrolysis, a monitoring system for regulation of the process of stirring and heating of a biomass for this dynamic behavior was especially designed for this purpose (Fig2):

1

(1-bioreactor, 2-worm pipe with ardent water, 3-solar header — water heater, 4-power source — solar photo transducers, 5-automatic management system and regulations, 6 and 7 electrodes).

The electro-osmosis is constructed with of the help electrodes (6 &7), biomass, installed in a reactor.

The stoichiometry of process of gas generation can be depicted by a following equation reaction:

пСбИюОб + n H2O = ЗПСН4 + 3n CO2 (3)

Important factor to consider in monitoring bioconversion are damp. Temperature, pH and composition of a fraction

To prevent biomass adhesion to the walls of a reactor a coating of triazin based stratum dimensional polymer is applied

To maintain steady and stable conditions for producing CH4 it is necessary to provide the following Conditions:

• Applicable mechanical — and physicochemical performances of raw (viscosity, electrical conductivity, temperature);

• Indispensable time of fermenting of a biomass in a reactor depending on composition of a biomass;

In a considered system a driving force of transmembrane carrying is the differential of chemical potentials in subsystems with allowance for of external fields referred to simple thickness of a membrane:

Y = -Dm / L. (4)

Where — Dm — differentials of chemical potentials in subsystems with allowance for of external fields, L-simple thickness of a membrane…

The chemical potential at laying an electrical field depends on stress P, mean concentration C of a biomass, his temperature T and potential difference A^, that is

Ap= f(P, C, T, ) (5)

Generalized thermodynamic forces represent the sum of forces:

Y=Yp + Yd +Yq+Ye (6)

Where Yp = f (A P) — calls a volumetric current (stream) of a pool faction through porous

membranes, YD =f ((A C) — diffusive current (stream), Yq =f (A T) heat flow, Ye = f (A^) — current of charged particles in a system.

For isotropic homogeneous environment the diffusion coefficient can be introduced by the way:

D = g f v0 exp (-DE/kT) (7)

Where g — number of paths, on which one the transferring from one state in other, f — a fraction of successful jumps (correlation factor), v0- frequency of jumps, DE — energy of transferring from one state in other, to — Boltzmann constant, 6 — temperature.

Transport rate of fragments biomass is possible which one on the sizes are much more than a diffusive stratum, is :

(8)

V

Described by an equation: where f — potential of boundary of slip, which one separates a stratum of a dispersed phase from bulk of a biomass, є dielectric constant of environment, є 0 — permittivity of vacuum, 8- an electric field strength the Mean value of an electric field strength for organic wastes was selected, by analogy with limy clay, and is equal (2)

E=J/x (9)

Where J — a current density x — electrical conductivity of organic wastes (biomass).

The resistance of interelectrode room, filled organic wastes is instituted by expression:

R = In (Ro/ro) / 2 L (10)

Where L — altitude of a concentric net-shaped welding rod, R0 and r0 — radiuses of adjacent concentric net-shaped welding rods. (Fig. 1)

For supply of an electric osmosis the indispensable electric energy acts(arrives) from solar photo transducers (5), and the thermal energy indispensable for keeping up of temperature in a bioreactor is ensured through a solar header of water heater (3), the heat carrier which one flows past on the pipe line (2), executed by the way of worm pipe and encompassing bioreactor from its outer side.

For cloudy days and in a winter period the solar water heater is in a condition of idle time. For keeping up the temperature of a bioreactor the padding heater will be utilized, in which one as combustible the biogas, receivable in a system will be utilized. Bioenergetics plant installations are usable both in southern and in northern locales. It opens up an outlook of usage of easily accessible and iterated sources and promotes a heightening of a social level of the population and ecological indexes of the environment.