WO2018185782A1

WO2018185782A1 - Gasifier for gasification of municipal solid waste

Info

Publication number: WO2018185782A1
Application number: PCT/IN2018/050195
Authority: WO
Inventors: Sumitro CHAKRABORTI; Govind Prasad Nagori; Bhag Chand Jain
Original assignee: Ankur Scientific Energy Technologies Pvt. Ltd.
Priority date: 2017-04-07
Filing date: 2018-04-05
Publication date: 2018-10-11

Abstract

The present invention determines gasifier for gasification of MunicipalSolid Waste (MSW). It particularly determines gasification of combustible fraction of MSW to produce fuel gas with high caloric value. The gasifier of the present invention mainly comprises a feed cone (1), a feeder (2), a reactor(3) and a wet discharge unit (4). The present invention determines the gasifier for gasification of MSW for conversion of combustible fraction of MSW into fuel gas by introducing oxidant which are the mixture of oxygen and inert gas that includes nitrogen and argon. The present invention also provides minimal of discharge and the hot gas that can be directly used in all thermal applications both in hot and cold modes including ultra clean applications like cooking and food industries.

Description

GASIFIER FOR GASIFICATION OF MUNICIPAL SOLID WASTE

FIELD OF INVENTION The present invention relates to gasifier for gasification of municipal solid waste (MSW). It particularly relates to gasification of combustible fraction of MSW to produce fuel gas with high caloric value.

BACKGROUND OF INVENTION

With growing economic development, changing habits and patterns of products and consumption as well as constant expansion of city scale, municipal solid waste and organic wastes are increasing exponentially affecting sustainable economic development and restricting urban development. MSW and organic wastes contain many harmful ingredients that, if not handled properly, will pollute environment and threaten human health.

At present state of art, MSW disposal technology mainly includes extensive garbage sorting and a multitude of utilization techniques including sanitary landfill, composting (biochemical) and incineration / combustion based power generation. Among these technologies, garbage sorting has not been implemented in many countries because it requires public participation. Even if garbage is sorted and recycling / re-use comprehensively attempted, there is still an amount of 40-50% of waste requiring incineration / combustion or landfill. In most parts of the world, sanitary landfill is adopted to dispose urban MSW, which occupies a lot of land resource, releases a lot of greenhouse gas, pollutes land and groundwater and destroys living environment of mankind. Composting technology only makes use of about 40% organic substances and the rest 60% still needs the disposal of incineration or landfill which also meets the problem of secondary pollution. Incineration of MSW seemingly reduces the amount and resource of garbage.

However, this method transfers solid pollutant to the atmosphere in the form of flue gas that will return to the earth by cross-ventilation and gravitational force or in the form of acid rain, affecting human health and environment with the carbon dioxide emissions from the greenhouse effect. Incineration also easily generates dioxin which is highly carcinogenic toxic substance to pollute environment and harm human health. Even with flue gas purification system, waste incineration still lacks effective and reliable end purification technology to eliminate dioxin pollution.

Some municipalities have installed plants that separate the combustible materials from metals and other noncombustible materials. The combustible material is commonly called Refuse Derived Fuel (RDF). It contains leather, rubber, plastics, paper, yard waste, etc. RDF made from sorting and palletizing of MSW is also used as boiler fuel in some cities. RDF uses only a small fraction for energy purpose whereas there is hardly any energy recovery in incineration. In summary, the disposal of garbage incineration is not a good way. Sanitary landfill occupies land, releases greenhouse gases and pollutes environment. Waste sorting and composting have to face the problem that a part of garbage cannot be fully used. The most important reason for the growing popularity of thermal processes for the treatment of solid wastes has been the increasing technical, environmental and public dissatisfaction with the performance of conventional incineration processes. MSW is difficult to handle, segregate and feed in a controlled manner to a waste-to-energy facility. MSW has a high tendency to form fused ash deposits on the internal surfaces of furnaces and high temperature reactors and to form bonded fouling deposits on heat exchanger surfaces.

While evaluating gasification or other thermal technologies, the degree of pre-processing required in conversion of MSW into a suitable feed material is a major criterion. Unsorted MSW is not suitable for most thermal technologies because of its varying composition and size of some of its constituent materials. It may also contain undesirable materials which can play havoc with the process or emission control systems.

One such example of down draft is as follow. Down draft gasifiers are well known and have been used for over 100 years. In the arrangement the MSW and oxidant both flow in a downward direction. The use of a downdraft gasifier results in a gas which is very low in tar concentration as the syngas passes through a char zone towards the lower section of the bed where significant tar destruction occurs. As the produced syngas requires minimal further clean up this type of gasifier has been found useful as an on board gasifier for vehicle use during times of fuel shortages. Another disadvantage of the conventional down draft gasifier is non-even distribution of air through the bed and excessive pressure drop across the depth of the bed.

US 7302897 determine municipal solid waste disposal process and apparatus using gasification. It particularly discloses the system for disposing of municipal solid waste which provides commercially available equipment that is modified to initially remove identifiable unwanted components from the waste and then chop the waste into small pieces of a size suitable for handling, separation and combustion. In this process, the unwanted materials were removed as it damage the shredding equipment, after that shredding, dewatering, separation of inert materials, combustion and then power generates. So, the problem associated with this invention is pre-processing of MSW include manual and mechanical separation or sorting, shredding, grinding, blending with other materials, drying and pelletization. It particularly determines gasification by air. It does not disclose the oxidant that controls the production of good quality gas.

Further, the limitation of the gasifier has very stringent feed quality requirements such as homogenous nature of MSW, low moisture content feed, uniform composition, high bulk density and high ash fusion temperature.

Hence, it is desperately needed to invent a suitable gasifier for gasification of municipal solid waste which is not subjected to above mention problems.

OBJECT OF THE INVENTION The principle object of the present invention is to provide gasifier for gasification of municipal solid waste which converts loose combustible fraction of MSW into high caloric producer gas.

Another object of the present invention is to provide gasifier for gasification of municipal solid waste which has unique and optimum design and produces gas having less tar and heavy metals after the gasification.

Yet, another object of the present invention is to provide gasifier for gasification of municipal solid waste which has excellent residue discharge system with inherent capability to handle, to maintain zones inside the reactor and remove clinkers that are likely to form during gasification. Further object of the present invention is to provide gasifier for gasification of municipal solid waste with minimum discharge which is harmless to the environment and economically viable. Another object of the present invention is to provide gasifier for gasification of municipal solid waste with energy recovery technology to convert combustible fraction of MSW into clean energy.

Further object of the present invention is to provide gasifier for gasification of MSW in which the gasifier accept the non-combustible materials like glass, metal construction materials, rock, sand, soil with elimination of much segregation except reasonably large size of non combustible material and soil. Still, another object of the present invention is to provide gasifier for gasification of municipal solid waste which generates a fuel gas integrated with combined cycle turbines, reciprocating engines and potentially with fuel cells that convert fuel energy to electricity. Yet another object of the present invention is to provide gasifier for gasification of municipal solid waste with ability to convert similar high ash, low ash fusion, and low bulk density feedstock like chicken manure, sludge from agro-processing industries, sewage sludge etc. SUMMARY OF THE INVENTION

The present invention discloses gasifier for gasification of municipal solid waste (MSW) comprises a feed cone, a feeder, a reactor and wet discharge unit. Said feed cone is configured to introducing the base fuel (MSW), said feeder is to receiving the base fuel passing out from the feed cone, in said feeder and feeder vibrator is configured to conveying the base fuel to the reactor. The rector having a plurality of zones arranged to define cascading passageway through which the base fuel is passing by gravity downwardly. Said zone comprising a demoisturization zone for converting the base fuel into dried feed by removing the moisture from said base fuel, a devolatization zone where the volatile is released from the dried feed and char is produced, an ignition zone for producing combustible material along with clinker from the char and carbonization zone where gasification reaction takes place, said reactor having an hopper and vibrator to helps in producing proper gas and solid mixing to ensure uniform and rich gas production inside the reactor. The wet discharge unit located below the reactor having an extractor coupled at the end of the wet discharge unit to extracting the gas from the said reactor and to extract the discharge from the reactor and also facilitates to trigger the gasification in the reactor. The reactor of the present invention having an oxidant distributor valve for introducing the oxidant in igniting zone to facilitate the gasification of MSW and said oxidant comprising oxygen and inert gas as argon and/or nitrogen in which the composition of oxygen varies from 35 % to 50 % with balance of the inert gas. BRIESF DESCRIPTION OF DRAWINGS

Figure 1 illustrates the schematic diagram of gasifier for gasification of municipal solid waste.

DETAIL DESCRIPTION OF THE INVENTION

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the construction and arrangement of parts illustrated in the accompany drawings. The invention is capable of other embodiments, as depicted in different figures as described above and of being practiced or carried out in a variety of ways. It is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation.

Before explaining the present invention in detail, it is to be understood that Municipal solid waste (MSW) may contain a very wide variety of waste or discarded material. For instance, the waste may include biodegradable waste, non-biodegradable waste, ferrous materials, non-ferrous metals, paper or card board in a wide variety of forms, a wide range of plastics (some of which may contain traces of toxic metals used as catalysts, stabilizers or other additives), paints, varnishes and solvents, fabrics, wood products, glass, chemicals including medicines, pesticides, solid waste of various types, pulp sludge, food manure, renderings, agricultural waste, forest residue and a wide range of other materials. The waste includes household waste and industrial waste, the latter being so called "safe" industrial waste i.e. low in toxic or hazardous materials. The present invention determines gasifier and gasification of municipal solid waste. In the present invention, the gasifier is a fix bed downdraft gasifier. The term "downdraft" is defined by the fact that the feed stock is feed into the gasifier from the top and progress down through the unit and the gas is exited from the bottom of the gasifier reactor.

As directed in Fig. 1, the present invention particularly determines the gasifier for gasification of MSW mainly comprises a feed cone (1), a feeder (2) a reactor (3) and a wet discharge unit (4) are positioned to vertically inline configuration.

The present invention determines a schematic diagram of the gasifier comprises the feed cone (1), the feeder (2), a feeder top valve (5), a feeder bottom valve (6), feeder vibrator (7), a hopper (8), a vibrator (9), an oxidant distributor (10), the rector (3), a sensor (not shown), the wet discharge unit (4), a conveyor (not shown), an extractor (not shown), a controller (not shown), a demoisturization zone (11), a devolatization zone (12), an ignition zone (13), a carbonization zone (14) and an outlet (15).

As illustrated in Fig. 1, said feed cone (1) is configured at the uppermost position of the gasifier for introducing base fuel. Feeder top valve (5), feeder bottom valve (6) and feeder vibrator (7) together form the feeder (2). Said feeder (2) is located below the feed cone (1) to receive the base fuel passing out from the feed cone (1) and introduces said base fuel into the reactor (3). Said feeder top valve (5) mounted on the top of said feeder (2). The feeder bottom valve (6) is located at the distal end of said feeder (3) for preventing the entry of air into said feeder (2). The feeder vibrator (7) is located at the side frame of the said feeder (3) and configured to convey the base fuel to the reactor (3). The feeder (2) is configured to be controlled by the feeder top valve (5) and the feeder bottom valve (6).

Said reactor (3) is substantially a cavernous structure mounted below said feeder (2) configured to gasify the base fuel coming from the feeder (2) and to generate fuel gas from the base fuel (2). The reactor (3) has a plurality of zones as demoisturizing zone (11), a devolatization zone (12), an ignition zone (13) and a carbonization zone (14) that are arranged to define cascading passageway through which the base fuel is passing by gravity downwardly.

Referring continuous with Fig.l, said zone comprising the demoisturization zone (11) for conversion of the base fuel into dried feed by removing the moisture from said base fuel; said devolatization zone (12) where the volatile is released from the dried feed and char is produced; said ignition zone (13) for producing combustible material along with clinker and char and said carbonization zone (14) where the gasification reaction takes place. As directed in Fig. 1, said reactor having an hopper (8) located in the said demoisturizing zone (11) and a vibrator (9) located at the side frame of the demoisturizing zone (11) to help in producing proper gas and solid mixing that ensures uniform and rich gas production inside the reactor (3). As the reactor (3) comprises the plurality of zones and the temperature of the demoisturization zone (11) is 80°C to 150° C, the temperature of the devolatization zone (12) is 150° C to 550° C, the temperature of the ignition zone (13) is 750 °C to 900° C and the temperature of the carbonization zone (14) is 800° C to 850° C.

The gasifier of the present invention does not introduce any air from the top or side of the reactor (3). Said reactor (3) of the present invention is provides with sensor (not shown) wherein the controller is configured to generate a thermodynamic indicator based on the signal. The reactor (3) of the gasifier is also provided with the outlet (15) which is configured to couple with the carbonization zone (14) of the reactor (3) so that produced fuel gases discharge from the reactor through the outlet (15).

Referring continuous with Figure 1, said reactor (3) having an oxidant distributor (10) configured at the ignition zone (13) in which oxidant mixture of oxygen and inert gas. The inert gas is selected from nitrogen and argon is distributed to facilitate the gasification of MSW. The composition of oxygen varies from 35 % to 50% with the combination of inert gases. The composition of oxidizing agent is disseminated in varying composition to facilitate the gasification and the composition of the oxidant is controlled by the monitoring the flow of the oxygen and nitrogen.

As directed in Fig. 1, extractor (not shown) located below the reactor (3). The extractor (not shown) plays an important role towards gasification. Said extractor is configured at the end of reactor (3) which is shown in Fig. (1) to extracts the gas from the said reactor (3) and facilitates absorbing the oxidant to trigger the gasification in the reactor (3). As directed in Fig. 1, the wet discharge unit (4) is located below the reactor (3). The discharge unit of the present invention plays an important role towards gasification. Said discharge unit maintains various temperature zones important for gasification reaction and maintaining ash char balance. As the presence of the clinker adversely affects process of the gasification, said wet discharge unit (4) breaks the bigger clinkers into smaller clinkers and also removes both clinkers and ash/char to facilitate gasification reaction and maintains zones position. Said discharge is generally refuse or byproduct of the gasifier. The discharge may include but not limited to ashes, char, clinkers, charcoals, tar etc.

The gasification of MSW in conjunction with its elements is further understood by following steps: The base fuel is introduced in to the feed cone (1) wherefrom said base fuel passes to the feeder (2) through the feeder top valve (5).

During this process, when the base fuel enters into the feeder (2) through feed cone (1), the feeder top valve (5) constitutes opens and feeder bottom valve (6) remains close.

The base fuel introduces to reactor (3) through feeder (2) with the assistance of feeder vibrator (7) and at that time the feeder bottom valve (6) constitute opens and the feeder top valve (5) remains close. In this said rector (3) where the arrangement of zones provides for descending the base fuel to flow from one zone to the next lower zone and the base fuel is changed thermodynamically.

The base fuel is enters into the demoisturization zone (11) of the reactor (3) from the feeder (2) where the moisture is removed in this zone at 80° C to 150° C temperature and the base fuel converts into the dried feed.

The dried feed right away introduces into devolatization zone (12) where the volatile releases from the base fuel at temperature range of 150° C to 550° C and char produces. The char further downwardly introduces into ignition zone (13) in which the temperature range of 750° C to 900° C and the oxidant introduces through oxidant distributor (10) into the said zone to facilitate the gasification and due to high temperature clinkers is produce.

The presence of clinkers adversely affect the process of gasification and then all the material along with char, clinkers further moves downwardly into carbonization zone (14) of the reactor (3) wherein the temperature of this zone is maintained between 800 °C to 850 °C so that fuel gases are produced which are discharged from the reactor through the outlet (15).

Above produced clinkers or other secondary or tertiary materials (discharge) collapse and transformed into smaller clinkers in the wet discharge unit (4) and said wet discharge unit removes clinkers, ash and char to facilitate gasification reaction in the carbonization zone.

From the aforementioned description the gasifier according to the present invention provide gasification of municipal solid waste without much segregation.

Further, the feeder top valve (5) and feeder bottom valve (6) are configured such that it prevents the ingress of air into the base fuel during the feeding of base fuel from the feed cone (1) to the feeder (2) and feeder (2) to the reactor (3). In another embodiment said feeder (2) of the present invention includes mesh (not shown) to control the size of feed entering into the reactor (3).

In further embodiment, the feeder (2) includes a dispenser (not shown) for collecting rejected feed that are denied entry into the reactor (3). The dispenser of the present invention does not accept the base fuel above 200 mm of the unit size of non combustible fraction of municipal solid waste like metals, glasses building materials, rock stones.

According to one embodiment, the extractor of the present invention has a variable extracting capacity to extract discharge from the reactor (3). The extracting capacity is adjusted by the controller base on thermodynamic conditions inside the gasifier, feed type and fuel has generation rate.

The present invention also provides minimal of discharge and the hot gas that can be directly used in all thermal applications both in hot and cold modes including ultra clean applications like cooking and food industries.

Although the example as well as the process of preparation and use has been specifically described, it should be understood that variations in the preferred embodiment could be achieved by a person skilled in the art without departing from the spirit of the invention. It is also to be understood that the present invention is given with the understanding that this invention is intended only to be illustrations without serving as a limitation on the scope of the invention as defined in the claims.

Claims

We claim:

1. A gasifier for gasification of municipal solid waste (MSW) comprises:

a feed cone (1) configured at the uppermost position of the gasifier to introducing the base fuel (MSW); a feeder (2) located below the feed cone (1) to receiving the base fuel passing out from the feed cone (1); wherein a feeder top valve (5) mounted on top of the said feeder (2), feeder bottom valve (6) located at the distal end of said feeder (2) for preventing the entry of air into said feeder (2), a feeder vibrator (7) configured at the side frame of the said feeder (2) to conveying the base fuel to the reactor (3); a reactor (3) is cavernous structure mounted below said feeder (2) to introducing the base fuel passing out from the feeder (2); wherein the reactor comprises front most demoisturizing zone (11) for converting the base fuel into dried feed by removing the moisture from said base fuel, a devolatizing zone (12) to release the volatile from the dried feed and to produce char, an igniting zone (13) for producing combustible material along with clinker and char and a carbonizing zone (14) to perform gasification reaction; wherein said zones are arranged to define cascading passageway through which the base fuel passes by gravity downwardly, said reactor (3) having an hopper (8) located in the said demoisturizing zone (11) and a vibrator (9) located at the side frame of the demoisturizing zone (11) to help in producing proper gas and solid mixing to ensure uniform and rich gas production inside the reactor (3); wet discharge unit (4) located below the reactor (3) to extract the discharge from the reactor (3) comprises an extractor (not shown) to extract the gas from the reactor (3) and also facilitates to trigger the gasification in the reactor (3); wherein said reactor (3) having an oxidant distributor (10) configured at ignition zone (13) for introducing the oxidant in igniting zone to facilitate the gasification of MSW;

2. The gasifier for gasification of municipal solid waste as claimed in claim 1, wherein the oxidant comprising oxygen and inert gas.

3. The gasifier for gasification of municipal solid waste as claimed in claim 1, wherein inert gas is selected from argon and nitrogen.

4. The gasifier for gasification of municipal solid waste as claimed in claim 1, wherein the composition of oxygen is 35% to 50 %.

5. The gasifier for gasification of municipal solid waste as claimed in claim 1, wherein the feeder top valve (5) and feeder bottom valve (6) are configured that prevents the ingress of air into the base fuel during the feeding of base fuel from the feed cone (1) to the feeder (2) and feeder (2) to the reactor (3).

6. A method for gasification of municipal solid waste comprising following steps:

(a) introducing a base fuel to a feed cone (1) and opening a feeder top valve (5);

(b) conveying the base fuel into a feeder (2) through the feed cone (1) and closing the feeder top valve (5);

(c) opening a feeder bottom valve (6) and introducing the base fuel to the reactor (3) from the feeder (2) with the assistance of a feeder vibrator (7);

(d) entering the base fuel into a demoisturizing zone (11) of a reactor (3) where the base fuel is converted into the dried feed;

(e) conveying the drying feed to a devolatizing zone (12) from the demoisturizing zone (11) through a hopper (8) with the help of a vibrator (9); (f) releasing the volatile present in the dried feed in a devolatizing zone (12) to production of char;

(g) conveying the volatile materials and char into an igniting zone (13) from the devolatizing zone (12);

(h) introducing the oxidant through oxidant distributing valve (10) in the igniting zone (13) and combusting the volatile materials and char in the igniting zone (13) in presence of oxidant and producing combustible product along with clinker;

(i) passing the combustible products into a carbonizing zone (14) from the igniting zone (13) to facilitating the gasification of combustible product;

(j) releasing the produced gas from the carbonizing zone

(14) through outlet (15);

(k) passing out the combustible fraction along with clinker/char produced in the igniting zone (13) into the wet discharge unit (4);

(1) breaking down the developed big clinkers into small clinkers in the wet discharge unit (4);

(m) removing the discharge along with clinker and ash/char from the gasifier through wet discharge unit (4).

7. The gasifier for gasification of municipal solid waste as claimed in claim 1, wherein the base fuel is introducing into feeder (2) from the feed cone (1) through a feeder top valve (5).

8. The gasifier for gasification of municipal solid waste as claimed in claim 1, wherein the base fuel is introducing into reactor (3) from the feeder (2) through a feeder bottom valve (6).

9. The method for gasification of municipal solid waste as claimed in claim 4, wherein the temperature of the demoisturizing zone (11) is 80 °C to 150 °C

10. The method for gasification of municipal solid waste as claimed in claim 4, wherein the temperature of the devolatizing zone (12) is 150 °C to 550 °C

11. The method for gasification of municipal solid waste as claimed in claim 4, wherein the temperature of the igniting zone (13) is 750°C to 900 °C.

12. The method for gasification of municipal solid waste as claimed in claim 4, wherein the temperature of the carbonizing zone (14) is 800°C to 850 °C.