FR2530488A1 - PROCESS FOR TREATING COMBUSTIBLE GAS AND INSTALLATION FOR CARRYING OUT SAID METHOD - Google Patents

Abstract

PRODUCTION AND USE WITHOUT HIGH PRESSURE STORAGE OF BIOGAS OBTAINED BY ANAEROBIC FERMENTATION OF ORGANIC WASTE. ACCORDING TO THE INVENTION, THE INTERCONNECTED INSTALLATION BETWEEN THE FERMENTATION TANK 11 AND A USER BOILER 13 INCLUDES AT LEAST ONE SUPERPRESSOR S1, S2 INTENDED TO BRING THE BIOGAS TO A PRESSURE JUST NECESSARY FOR SUPPLYING THE BOILER AND THE MEANS OF RECIRCULATION OF A FRACTION OF COMPRESSED GAS 18 INCLUDING IN PARTICULAR A VALVE 21 TO MAINTAIN CONSTANT DEPRESSION UPSTREAM OF THE BOOSTER (S). APPLICATION TO THE TREATMENT OF ORGANIC WASTE, ESPECIALLY IN THE TREATMENT OF POTATOES.

Description

AT'

  PROCESS FOR TREATING COMBUSTIBLE GAS AND

  INSTALLATION FOR IMPLEMENTING THIS METHOD

  The invention relates to a method for treating combustion gases

  It is produced or extracted in a variable quantity, the main purpose of said process being the immediate combustion of at least most of the gas in a boiler for use while avoiding expensive intermediate storage carried out at high pressure. also a fuel gas installation for the

of this process.

  The need for energy savings has led to

  to deal with the treatment of certain organic wastes, mainly

  in the agro-food industries, with a view to producing a poor gas called "biogas"

  sufficient to constitute a source of back-up energy

  For example, a field of application of

  the invention may be that of a pump packaging plant.

  of land (for the production of frozen food) o processing

  This results in the formation of large quantities of effluents with a high content of organic matter. Anaerobic fermentation results in both a very efficient purification (of the order of 90%) and in the production of biogas. It is recovered can cover a significant part of the energy needs of the plant.

  steam production normally operating on natural gas.

  In such a context, the invention can make it possible to reduce

  consumption of natural gas.

  Up to now, a similar installation required

  large investments due to the fact that the biogas produced

  intermediate storage under high pressure, which necessitates

  cumbersome and expensive equipment This intermediate storage

  was, however, considered inevitable because of the irregularity

even of biogas production.

  -2 - The invention goes against this concept by proposing a rational use of the biogas produced, as and when

  formation, without high pressure intermediate storage.

  With this in mind, the invention therefore relates to a process for treating a combustible gas produced in variable quantity, for the immediate combustion of at least the greater part of said gas in a boiler, characterized in that it consists in carrying said

  gas at a relatively low pressure just needed to

  putting the supply of said boiler, possibly recirculating a portion of said compressed gas to the production zone of said gas to maintain a relatively

constant in this area.

  The invention also relates to a fuel gas treatment plant produced in variable quantity, for example gas coming from an anaerobic fermentation tank containing organic materials, said treatment being mainly intended for the immediate combustion of at least the major part gas in a boiler, characterized in that it comprises at least one booster connected upstream of said boiler, said booster being adjusted to bring said gas to a low pressure just necessary to allow the supply of said boiler and

  means for recirculating a portion of said compressed gas comprising

  in particular a controlled opening valve, driven by a

  pressure sensor upstream of said booster.

  The booster is of the constant flow type and the variable recirculation of the gas thus makes it possible to regulate the value of the depression which

  reigns above the fermentation tank.

  In the event of an overproduction of biogas, a torch connected to the output of the booster is provided via a controlled valve, of the progressive opening type, said valve being in particular controlled by a pressure sensor connected to the booster. the

  output of the booster One can also provide several surprises-

  parallel-mounted and respectively put into service for predetermined flow rates, for example by means of

  measuring the pressure upstream of said boosters.

  The invention will be better understood and other advantages of

  it will appear better in the light of the description that will

  follow of a fuel gas treatment plant according to the principle of the invention, given solely by way of example and with reference to the accompanying drawing in which: the single figure is a schemabloc simplified installation

according to the invention.

  The fuel gas treatment plant is intended to be inserted between an anaerobic fermentation tank 11 and auxiliary burners 12 of a boiler 13. The gas is sucked as it is formed in the tank 11 by a conduit 14 and passes through a water level regulating type drainage liner 15 in which the gas cooling condensates are recovered. The outlet of the drainage liner is connected via an on-off type valve 16 at the inputs of two boosters SI and 52 connected in parallel The outputs of these boosters feed the auxiliary burners 12, through a discharge duct 17 The boosters are set to bring the gas to a low pressure just necessary to allow the supply of the Boiler Gas recirculation means comprising a serial branch 18 of several components are connected between the outputs and the inputs of the booster pumps. The series includes a pressure reducer 19, a cooling exchanger 20 and especially a controlled valve 21, of the progressive acting type, controlled by a pressure sensor 22 connected upstream of the booster pumps between the drainage liner 15 and the valve 16. by the sensor 22 are processed in a control unit 23 to, firstly actuate the opening of the valve 21 and, secondly, to selectively activate one or two boosters according to predetermined flow rates In fact, the production flow is linked to the pressure in the fermentation tank and the start-up or shutdown of the boosters will be done from different pressure thresholds.

measured by the sensor 22.

-4 -

  A flare 25 is connected to the common outlet of the overheads

  ss via a modulating electromneumatic valve 26 controlled by a pressure sensor 27 connected to the outlet of the boosters The admission of the gas to the flare makes it possible to regulate to a certain extent the supply pressure of the boiler .

  An oxygen analyzer 28 of the parametric susceptibility type

  gnétique is connected (dashed lines 29, 30, 31) at several points of the gas circulation circuit between the tank 11 and the boiler 13 This analyzer controls a security system 32 may stop the installation as soon as the content In oxygen this exceeds a predetermined value. This pilot-safety system, in particular the valve 16, and another valve 33, of the all-or-nothing type, connected between the connection: tank-booster on the one hand and a

  gas vent stack 34 on the other hand.

  The operation of the installation which has just been described is

  very simple and evidently follows from the foregoing description.

  As it is formed, the biogas is drawn into the tank 11 by the SI booster or boosters, 52, the valve 16 being normally open and the valve 33 normally closed. The biogas gives up some of its moisture in the air. drainage A recirculation of the supercharged gas, modulated by the valve 21, is carried out when the production of biogas in the tank II is lower than the constant flow rate of the booster (s) put into service, which thus makes it possible to maintain a substantially constant low pressure in the Since the gas has been compressed and it has warmed up through the booster, the expander 19 and the temperature exchanger 20 allow to bring back the fraction reinjected in the initial conditions of temperature and pressure When the production is greater than the capacity of the burners 12 or when the boiler is stopped, biogas is burned by the flare 25 The gas supply to the flare is modulated by the valve 26, which makes it possible to maintain a substantially constant pressure at the feed inlet of the

  boiler According to the operating conditions of this

  niere, a variable number of burners 12 can be put into service, each burner is controlled by a solenoid-type electromagnetic valve, not shown The pressure sensor 27 can control the commissioning of the burners 12, through a system additional regulation defining high and low limits of the pressure range allowed to have a correct and safe combustion The number of burners to be put into operation is thus established according to the level of production of biogas, the additional heating power necessary for operation of the boiler 13 is provided by natural gas supplying other

burners not shown.

  If the analyzer 28 detects a rate of oxygen capable of forming a detonating mixture, the valve 16 is closed while the valve 33 opens putting the tank II in communication with the

  vent stack 34; the boosters are taken out of service.

  Of course, the invention is not limited to the embodiment of

  the facility just described but includes all the equi-

  valents techniques means involved if they are in the

  framework of the following claims.

-6-

Claims (8)

  A method for treating a combustible gas produced in a variable quantity, for the immediate combustion of at least the greater part of said gas in a boiler (13), characterized in that it consists in bringing said gas to a relatively low pressure , just necessary to allow the supply of said boiler by recirculating (18) optionally a portion of said compressed gas to the production zone of said gas to maintain a   relatively constant pressure in this area.   Process according to Claim 1, characterized in that   comprises burning (25) at least a portion of said gas in the atmosphere.   when the production exceeds the needs of the moment.   3 Fuel gas treatment plant produced in a variable quantity, for example gas from an anaerobic fermentation tank (11) containing organic material,   said treatment being primarily intended for immediate combustion   diate at least the largest part of said gas in a boiler (13) characterized in that it comprises at least one booster (SI, 52) connected upstream of said boiler, said booster being adjusted to bring said gas to a low pressure just necessary to allow the supply of said boiler and means for recirculation (18) of a portion of said compressed gas comprising in particular a valve (21) controlled driven by a sensor of   pressure (22) upstream of said booster.   4 Installation according to claim 3, characterized in that   said booster is of the constant flow type.   Installation according to Claim 3 or 4, characterized in that the said recirculation means comprise a series branch (18) including the said valve (21) and an expansion valve (19), a branch   between the outlet and the inlet of said booster.   6 Installation according to claim 5, characterized in that   said series connection further comprises a cooling exchanger deformation (20). -7-   Installation according to one of claims 3 to 6, characterized   characterized in that it comprises a plurality of constant flow rate inpressors (SI, 52) connected in parallel and respectively put into service for predetermined flow rate ranges, for example by means of measuring the pressure upstream of said booster pumps (22, 23).   8 Installation according to one of claims 3 to 7, characterized   in that a flare (25) is connected to the output of the   blowers via a controlled valve (26), said valve being in particular controlled by a pressure sensor (27)   O 10 connected to the output of the blower (s).   9 Installation according to one of claims 3 to 8, characterized   characterized in that it comprises an oxygen analyzer (28), for example of the paramagnetic susceptibility type, connected at one or more points of the gas circulation circuit upstream of said boiler (13) and a system of security (32) controlled by said analyzer to stop the installation of that said oxygen content   exceeds a predetermined value.   Installation according to one of claims 3 to 9, characterized   characterized in that it comprises a chimney evacuation of said gas (34) connected upstream of the blower (s) (SI 1, 52) via a controlled valve (33), all or nothing type,   driven by a security system (28, 32).