ES2265766B1 - "PROCEDURE AND INSTALLATION FOR THE ENERGETIC VALUATION OF URBAN SOLIDOS RESIDU". - Google Patents

Abstract

Procedure and installation for the energy recovery of urban solid waste. Procedure for the energy recovery of urban solid waste, which includes the stages of chopping; deposit the chopped waste in a drying pit and dehumidify said waste by drying it with a hot gas, as well as separating the recyclable and inert components of the dry waste and crushing said waste to obtain a combustible material, which is subsequently gasified to obtain of a conditioned synthesis gas which is used as fuel in internal combustion engines, the process also comprising the step of transferring remaining thermal energy available in the exhaust gases of the internal combustion engines for the production of the hot gas used to dry the waste The installation for carrying out the process comprises a device for transferring thermal energy remaining in the exhaust gases of internal combustion engines.

Description

Procedure and installation for recovery energy of urban solid waste.

Technical sector of the invention

The invention relates to a method and to an installation for the energy recovery of solid waste urban, from the reception of waste until its drying and subsequent use for the production of a biogas.

Background of the invention

The management of urban solid waste, in forward RSU, generated by large concentrations of population presents serious difficulties due to the increase in production of MSW, in the absence of adequate space for controlled landfills and at the closure of incinerator plants that do not meet the emission requirements, increasingly demanding, required by current laws.

For some time, the valorization energy of MSW through gasification facilities, aerobic and boiled digestions thereof have replaced gradually the old practices in which the MSW were burned in incinerators to obtain steam or electricity.

In the field of waste management, there is a very pronounced specialization due to the different technologies that intervene for each of the steps that are carried out during the management of such waste, so it is common to installation of independent plants for collection and treatment of the MSW and plants for the gasification of the MSW that are obtained from the collection and treatment plants.

Patent document US 2004/0221778 describes however a procedure and a comprehensive management facility of RSU, which includes since their collection and treatment until the final production of electrical energy, by means of a gasification installation of the waste treated in it plant.

According to said procedure, they first separate from the RSUs the unwanted materials and subsequently crush the remaining waste, so that the size of each piece does not exceed 150 mm The crushed waste is subjected to a stage of dried to eliminate, almost completely, all its water content. Specifically, the water content by weight of the waste after Its drying is approximately 10%.

They are then separated from dry waste crystals and metals and, according to a variant of procedure, the remaining waste is crushed again before its introduction into a gasification reactor for Biogas production. The biogas obtained is used for energy production and, according to a variant of the procedure, part of that energy is in the form of steam and the content The energy of this steam is used for drying MSW.

It is an objective of the present invention to give know a procedure and an installation that improves efficiency and the overall energy balance of known procedures, and especially procedures like the one described above, which are carried out in the same installation.

Explanation of the invention.

The procedure for energy recovery urban solid waste object of the invention comprises the stages of receiving and cutting waste; deposit waste resulting slices in a drying pit under vacuum; dehumidify the chopped waste by drying them through forced circulation of an unsaturated hot gas through the drying pit; separate recyclable and inert components from dry waste and crush the separated waste to the obtaining combustible material (CDR) derived from waste urban solids; and gasify the combustible material obtained in a gasification installation.

In essence, the process according to the invention It is characterized because it also includes the stages of conditioning the synthesis gas obtained in the gasification installation; feed at least one internal combustion engine with gas from conditioning synthesis; and transfer remaining thermal energy available in the exhaust gases of combustion engines internal for the production of hot gas.

According to these characteristics, the hot gas production is not a stolen or deferred energy of procedure, as in similar procedures, but heat is transferred directly from the exhaust gases of the internal combustion engines by mixing said gases of exhaust with air captured from the outside and / or wet gas extracted from the Drying pit, or, is transferred indirectly, by means of A heat exchanger device, the heat of exhaust gases of internal combustion engines to outside air and / or moist air extracted from the drying pit, obtaining essentially hot air. In the process according to the invention, all the synthesis gas or biogas produced is used for the electricity production, unlike procedures known, in which only a fraction of the gas produced is used for this purpose, the remaining fraction burned for steam production whose thermal energy is used in the dehumidification stages.

According to another feature of the invention, the water content in the combustible material obtained represents between 15 to 25% of its weight.

According to another feature of the invention, in the deposition stage of the chopped waste, these are deposited forming independent packages or beds of height included between 1 and 3 meters high, and each package is subjected during a period of 1 to 5 days at an ambient temperature of between 50 and  90 ° C

According to another feature of the invention, in the stage of dehumifying, drying, the hot gas circulation through waste packages chopped, the speed of circulation of said gas being through of packages from 8 to 30 cm / s.

According to another feature of the invention, the hot gas used in the dehumify, dried stage, is a mixture of air captured from the outside and a fraction A of the air wet caught at the exit of the packages, which is heated with the remaining thermal energy available in the exhaust gases of the internal combustion engines before their introduction to the pit of dried

According to another feature of the procedure, the wet gas extracted from the drying pit that is emitted into the atmosphere is previously purified by biofilters

In accordance with another aspect of the invention, discloses an installation for carrying out the procedure also object of the invention. This installation includes media for the scrapping of waste; a pit for drying the chopped waste; an air circulation facility that includes means for injecting hot gas into the drying pit to absorb moisture from chopped waste and media extraction of wet gas from the drying pit; a means for separation of recyclable and inert components from waste dried and for crushing separated waste; and ones means of gasification of the combustible material (CDR) obtained, derived from waste, for the production of a synthesis gas conditioned.

The installation is characterized because in addition It comprises at least one internal combustion engine powered by the conditioning synthesis gas; and a device for transfer of remaining thermal energy available in gases Exhaust of internal combustion engines, for production of the hot gas injected into the drying pit.

According to another feature of the invention, the installation comprises at least one mixer adapted to mix the exhaust gases of internal combustion engines with the air taken from outside and / or the wet gas extracted from the pit of dried

According to another feature of the installation according to the invention, this comprises at least one heat recuperator whereby the thermal energy of the Exhaust gases are transferred to a heating fluid, and at least one heater through which thermal energy is transferred from the fluid air heater captured from the outside and / or moist air extracted from the drying pit, essentially obtaining hot air.

According to another feature of the invention, the installation comprises at least one heat exchanger gas-gas adapted to transfer heat from the air non-recirculated wet collected by the air collection means exterior intended to be mixed with the fraction of moist air recirculated

The installation for the realization of The object of the invention is characterized in that it comprises means for the recirculation to the drying pit of a fraction A of the moist air collected by the means of catchment.

The installation comprises at least one mixer which mixes outside air with fraction A of moist air recirculated before injection to the drying pit.

According to another feature of the installation according to the invention, this comprises at least one gas-gas heat exchanger adapted for transfer heat from the non-recirculated moist air collected by means for collecting outside air, intended to be mixed with fraction A of recirculated moist air.

Brief description of the drawings

The attached drawings illustrate, schematically, a procedure and an installation according to the invention. In these drawings:

Fig. 1 is a block diagram of the method according to the invention;

Figs. 2 and 3, are two representations schematics of a device for thermal transfer of energy remaining in the exhaust gases of combustion engines internal for the production of hot gas that incorporates a installation according to the invention;

Fig. 4, is a schematic representation of an installation for carrying out the procedure of Fig. 1; Y

Fig. 5, is a schematic representation of a drying pit to carry out the drying stage according to the invention.

Detailed description of the drawings

The procedure for energy recovery of solid urban waste, hereinafter RSU, object of the invention has been schematically represented in Fig. 1. Of a known method, the procedure comprises the step of receiving and chop 30 the MSW, contained in garbage bags, where they are chopped said bags with the aim of breaking them to release their content. This chopping, unlike the crushing that takes carried out in similar procedures, does not aim at crushing in small portions of the collected MSW, but which is meant to automatically break the bags or others container containers that can store MSW. Then in the deposit stage 31 as shown in Fig. 1, is deposit the chopped MSW in a drying pit, subjected to empty, forming independent packages or beds with the aim of Separate the MSW received on different days.

The height of the beds formed is between one and three meters high and each package remains inside the drying pit for a period of between one and five days, depending on the characteristics of the RSU received. During this period the RSUs are subjected to a dehumidification stage 32, that is, they are dried. To do this, the ambient temperature inside the pit is maintained between 50 and 90 ° C, approximately, and a flow of hot and dry gas is blown by some nozzles so that it crosses the packages of MSW, absorbing the moisture contained in the packages and so that the water content in them is reduced to 20% of its mass. Preferably, the speed of circulation of the gas through the RSU packages are adjusted between 8 to 30 cm / s, to absorb the greatest amount of water possible in one step.

The short time of permanence of the RSU in the Drying pit and the continuous circulation of hot gas prevents reactions occur in the MSW, such as decompositions anaerobic, which are responsible for odor emissions and of gases like methane. In addition, the atmosphere inside the Drying pit is maintained at a pressure below the pressure atmospheric, preventing bad odors from escaping from the pit and they can be annoying for the personnel in charge of installation or even for the homes or facilities of the surroundings.

As the RSU packages are considered dried, they are extracted from the drying pit and subjected to a preparation process for the final obtaining of a subject 26 fuel derived from waste, hereinafter CDR. This process, indicated with reference 33 in Fig. 1, comprises a separation stage, where the dry MSWs are separated recyclable, ferrous materials, containing aluminum or inert, and a crushing stage, to adapt the size of the waste to the requirements demanded by the process of energy recovery. Next, the CDR 26 obtained is introduced into a gasification installation (step indicated with reference 34 in Fig. 1) of the type of those comprising a fluidized bed reactor and a subsequent installation of conditioning (as indicated in reference 35 of Fig. 1) of the 16 biogas obtained. This biogas 16 is subsequently used as fuel (see reference 36 in Fig. 1) in one or more Internal combustion engines for electricity production. An additional supply of natural gas is optionally provided for increase the power generated by said engines.

The procedure comprises a stage of use of heat energy from exhaust gases 17 of internal combustion engines for gas heating which is blown into the drying pit to dry the MSW, or put another way, for the production of hot and dry gas used in the drying stage of the MSW.

In the scheme of Fig. 1 the gas used to the drying is hot air 5, and a fraction A of the humid air 5 ' captured at the exit of the drying pit and used for drying of the MSW is mixed with outside air 14 before being heated and reintroduced back to the pit. The heating of this mixture of air is carried out with the contribution of direct or indirect heat of the exhaust gases 17 of the internal combustion engines. In the example of Fig. 1, the heat of the exhaust gases 17 is transmitted indirectly, through a first heat exchanger heat 22, to a heating fluid 18 which is conducted to a second heat exchanger 25, in which the heat of the fluid heater 18 is transmitted to the air mixture formed by air outside 14 and fraction A of recirculated air, for warming up before its introduction to the pit. Harnessing of the heat of the internal combustion gases 14, according to the procedure of the diagram of Fig. 1, has been represented schematically, in Fig. 3.

In the same Fig. 1 it is also observed that the heat of fraction B of moist air 5 'not recirculated is exploited, in a gas-gas heat exchanger 29, to preheat the outside air 14 which is subsequently mixing with fraction A of 5 'recirculated moist air, before its Introduction to the pit.

According to the scheme in Fig. 1, the stage separation of MSW is carried out after drying, which which facilitates the handling of MSW and allows automation of the separation facility. On the other hand, short drying at that the RSUs are submitted, as well as the recirculation of a fraction A wet air 5 'to the drying pit for the stage of dehumidification or drying of the MSW, reduces the contribution energy required for heating the air used in said drying stage. According to the procedure of the invention, all the energy required for drying the MSW is obtains from the exhaust gases 17 of combustion engines internal, without the need to provide energy from a source external energy

In another variant of the procedure, the heat of Exhaust gases 17 is transmitted directly for production of a hot gas 50 used for drying the MSW in the drying pit. Indeed, as shown in Fig. 2, the gases Exhaust 17 is mixed in a mixer 7 directly with air exterior 14 obtaining a hot gas 50 resulting from the mixing. In this case, the mixing of air at room temperature with the exhaust gases 17, at an approximate temperature of 400 ° C, results in a hot gas 50 at an optimum temperature for drying the RSU.

Fig. 4, is a schematic representation of an integrated installation to carry out the procedure shown in Fig. 1, in which the drying gas is consisting essentially of hot air. In said Fig. 4, note that the installation comprises a drying pit 3, adapted for the reception and storage of the RSUs that are to be treated. The drying pit 3 is provided with cutting means 2 for release the MSW from the bags or containers that store them. The MSW packages are deposited on the bottom of the drying pit 3 and specifically about air extraction means 6 constituted by a grill, through which the air is sucked wet 5 'that has absorbed moisture from the MSW as it passes through of the MSW packages formed and deposited on said grill. The drying pit 3 is also provided with means for the 4 hot and dry air injection 4 over the MSW packages. In the example of Fig. 4, the drying pit 3 is provided with a series of blowers arranged on the top and / or sides thereof, through which the flow of hot air 5 and Dry is driven in the direction of MSW packages. The Depression on the bottom and / or sides of the drying pit 3, suck the 5 hot and dry air through the RSU bed.

In Fig. 5, a detail of a variant of a drying pit 3 in which the means for 4 injection of hot air 5 are located inside regularly distributed columns along the drying pit 3 and comprise respective side outlet holes, in said columns, for blowing hot air 5, while the means for the extraction 6 of the humid air 5 'are constituted by a lower grill 6a and by collecting holes 6b provided in the bases of the mentioned columns.

The installation of the invention comprises a 5 'wet air ducting circuit 20', sucked through of the grill, which includes a fan installation 16 for the discharge of said moist air 5 'to means for its recirculation 12 inside the drying pit 3. These means for recirculation 12 are constituted by respective three-way valves adapted to derive a fraction A of air wet 5 'to two mixers 13 or to an installation of biofilters 19. The amount of recirculated air is determined by saturation level that this air presents at the exit of the grill. If it is very saturated with water, all the 5 'wet air stream is sent to the biofilters 19. By the on the contrary, if the humid air 5 'contains little water load a important fraction A of said moist air 5 'is recirculated to the Drying pit 3 to optimize the thermal performance of the installation.

The installation comprises a group of secondary fans 15 intended to aspirate outside air 14 and to drive it to the mixers 13, where the outside air 14 it is mixed with the fraction A of moist air 5 'mentioned above. The resulting mixture is heated for the production of hot air 5 and dry, which is introduced in the drying pit 3 for drying the RSU.

The outside air 14 is heated, previously to its introduction in the mixers 13, in the exchangers of gas-gas heat 21 of which the installation of the invention. In the heat exchangers gas-gas 21, fraction B of moist air does not recirculated to the drying pit 3 yields part of its thermal energy to outside air 14, before its emission to the atmosphere through biofilters 19 based on wood and chopped bark.

The installation is provided with some means to separation 8 of the MSWs dried in the drying pit 3, by which recyclable materials are separated from the MSW, ferrous or inert, as well as aluminum mixed between MSW, and also means for crushing the separated waste, with which the final CDR 26 is prepared which is introduced in some gasification means 9, for the production of a synthesis gas conditioned. These gasification means 9 are constituted essentially by a fluidized bed gasifier 9a and by a 9b washing installation or gas conditioning. The biogas 16 obtained is introduced in an internal combustion engines 10 for the production of electricity.

For air heating 5 introduced in The drying pit 3 the installation comprises heaters 25. In the example of Fig. 4, the installation is provided with two heaters 25, inside of which the air 5 intended for being injected or blown to the drying pit 3 is heated by contact with the outer surface of a coil, by whose a heating fluid circulates inside 18. However, unlike of the known installations, the heating fluid 18 absorbs first the remaining thermal energy available in the gases of 17 exhaust from internal combustion engines 10, powered by the biogas 16, to then transfer it to the air in the heaters 25. For this purpose, the installation of the invention comprises a device for transferring thermal energy 11, constituted basically by a closed circuit 24 of heating fluid 18 and by a heat recuperator 22 of the exhaust gases 17 of the engines 10. In the heat recuperator 22, said exhaust gases 17 transfer thermal energy to the heating fluid 18, which is conducted by closed circuit 24 to heaters 25, in where the heating fluid 18 in turn transfers part of its thermal energy into the air 5 that will be injected into the drying pit 3. The device for thermal energy transfer 11 is provided, as seen in Fig. 4, of a pump of drive 23 of the thermal fluid 18, to ensure a pressure and a adequate flow to the closed circuit 24.

Claims (14)

1. Procedure for the energy recovery of urban solid waste, which includes the stages of receiving and cutting (30) the waste; deposit (31) the resulting chopped waste in a drying pit under vacuum; dehumidify (32) the chopped waste by drying it through the forced circulation of an unsaturated hot gas (50) through the drying pit; separate (33) recyclable and inert components from dry waste and crush waste to obtain a combustible material (CDR) derived from urban solid waste; and gasify (34) the combustible material obtained in a gasification installation, characterized in that it also comprises the steps of

-

condition (35) the synthesis gas obtained in the gasification installation;

-

feed (36) at least one motor internal combustion with conditioned synthesis gas; Y

-

transfer remaining thermal energy available in the exhaust gases (17) of combustion engines internal for the production of hot gas.

2. Method according to claim 1, characterized in that heat for the production of the hot gas (50) directly transfers heat from the exhaust gases (17) of the internal combustion engines by mixing said exhaust gases with air taken from outside ( 14) and / or wet gas extracted from the drying pit. 3. Method according to claim 1, characterized in that the heat of exhaust gas (17) of internal combustion engines is indirectly transferred to the production of hot gas (50) by means of a heat exchanger device (11). to air captured from the outside (14) and / or to humid air (5 ') extracted from the drying pit, essentially obtaining hot air (5). 4. Method according to claim 1, characterized in that the water content in the combustible material (CDR) obtained represents between 15 to 25% of its weight. 5. Method according to the preceding claims, characterized in that in the deposition stage (31) of the chopped waste, these are deposited forming independent packages or beds of height between 1 and 3 meters high, and because each package is subjected to a ambient temperature between 50 and 90 ° C for a period of between 1 and 5 days. Method according to the preceding claims, characterized in that in the drying stage (32) the circulation of hot gas (50) is forced through the packages of chopped waste, the speed of circulation of said gas being through the packages from 8 to 30 cm / s. Method according to claims 3 to 6, characterized in that the hot air (5) used in the drying stage (32) is a mixture of air collected from the outside (14) and a fraction (A) of the moist air (5) ') captured at the exit of the packages, which is heated with the remaining thermal energy available in the exhaust gases (17) of the internal combustion engines before their introduction to the drying pit. Method according to claim 3, characterized in that the wet gas (5 ') extracted from the drying pit that is emitted into the atmosphere is previously purified by biofilters. 9. Installation for carrying out the process according to claim 1, comprising means for cutting (2) the waste; a drying pit (3) of the chopped waste; air circulation means including means for the injection (4) of hot gas (50) into the drying pit to absorb moisture from the chopped debris and means for extracting (6) wet gas from the drying pit; means for separating (8) the recyclable and inert components of dried waste and for crushing the waste; and gasification means (9) of the combustible material (CDR) obtained, derived from waste, for the production of a conditioned synthesis gas, characterized in that the installation also comprises

-

to the minus an internal combustion engine (10) fed with the gas from conditioning synthesis; Y

-

a device for transferring thermal energy (11) remaining available in the exhaust gases (17) of combustion engines internal, for the production of hot gas injected into the pit of dried

10. Installation according to claim 9, characterized in that the device for thermal transfer (11) comprises at least one mixer (7) adapted to mix exhaust gases (17) of internal combustion engines (10) with air taken from outside and / or wet gas extracted from the drying pit (3). 11. Installation according to claim 9, characterized in that the device for thermal transfer (11) comprises at least one heat recuperator (22) by means of which the thermal energy of the exhaust gases (17) is transferred to a heating fluid (18) ), and at least one heater (25) whereby heat energy from the heating fluid is transferred to outside air (14) and / or humid air (5 ') extracted from the drying pit (3), essentially obtaining air (5) hot. 12. Installation according to claim 11, characterized in that it comprises means for the recirculation (12) to the drying pit (3) of a fraction (A) of the moist air (5 ') collected by the collection means (6). 13. Installation according to claim 12, characterized in that it comprises at least one mixer (13), which mixes outside air (14) with the fraction (A) of moist air (5 ') recirculated before its injection into the drying pit ( 3). 14. Installation according to claim 11, characterized in that it comprises at least one gas-gas heat exchanger (21) adapted to transfer heat from the non-recirculated moist air (5 ') (B) collected by the collection means (6) to the air exterior (14), intended to be mixed with the fraction (A) of recirculated moist air.