An apparatus and process to analyze and characterize spalling thermo-mechanical failure of coal during underground coal gas

FIELD OF THE INVENTION

The present invention, in general, is directed to an apparatus and a proc analyzing and characterizing the physical and chemical processes occui underground coal seams during UCG process. More specifically, the pr invention relates to the spalling behavior of coal during underground cc gasification.

BACKGROUND

Underground coal gasification (UCG), is an in-situ conversion proc which is present in deep underground seams, to combustible product j the process of UCG, a cavity is formed inside the coal seam d consumption by chemical reactions. The temperature inside the around700-1000°C and at this temperature, the coal present at the : cavity develops cracks in it, due to its drying and pyrolysis. These c with time until a piece of coal breaks from its parent material and falls ( of the cavity. This phenomenon is called spalling. The extent of sp; particular type of coal is an important input to UCG process model tl the product gas calorific value. Till date, there is no equipment or m available for the analysis, characterization and/or quantification < Spalling is conceptualized as something which occurs in regul However, as yet no apparatus or process is known for the charact spalling behavior of coal. There has been a long-felt need to study process in detail in order to predict and/or estimate the product gas UCG process.

The present inventors have solved this long-felt need by developing a for studying and quantifying the spalling behavior of coal and a proce the apparatus.

DESCRIPTION OF THE INVENTION

The invention relates to an apparatus for analyzing and characterizi behavior of coal during underground coal gasification comprising a having a lid (2) with an opening (3); a heat source(4) located at the bot of the furnace (1); a coal block holder (5) for holding a coal block (6 furnace (l),wherein the coal block holder (5) has an open bottom (7 heat source (4);at least one inlet tube (8), for supplying gas to the 1 placed between the heat source (4) and open bottom (7) of the coal b (5);at least one outlet tube (9), for removing gas from the furnace between the heat source (4) and open bottom (7) of the coal block 1 device (10), for monitoring weight of the coal block (6), placed furnace (1) and comprising a suspension means(l 1) for suspending the (6) with the coal block holder(5) in the furnace (1); wherein the means(l 1) passes through the opening (3) of the furnace lid (2).

Another aspect of the invention relates to a process for ana characterizing the spalling behavior of coal during underground coal j wherein the process comprises the steps of

a) Placing a coal block (6) within a coal block holder (5); b) suspending the coal block holder (5) with the coal block device(l O) for monitoring weight of the coal block (6) ai point of time; wherein the device (10) comprises a suspen (1 1) for suspending the coal block holder (5) with the coal h c) placing the device(l O) for monitoring weight of the coa outside a furnace (1) such that the suspension means i through an opening (3) in lid (2) of the furnace(l ) with the (6) within the coal block holder (5) suspended from the de ¹ monitoring weight of the coal block (6) and being placed furnace (1 );

d) passing a mixture of gases into the furnace (1) through ai

(8);

e) raising the temperature in the furnace to 700 to 900°C b; heat source(4) placed in the furnace (1); and

f) recording weight profile of the coal block (6) with respect tc BRIEF DESCRIPTION OF DRAWING

Fig. 1 illustrates a schematic diagram of the apparatus.

Fig. 2 illustrates the weight profile of coal block versus time on he coal block under air atmosphere and at a temperature of 700°C.

DETAILED DESCRIPTION OF THE INVENTION

The description of the specific embodiments will so fully reveal the gc of the embodiments herein that others can, by applying current knowlc modify and/or adapt for various applications such specific embodim departing from the generic concept, and, therefore, such adap modifications should and are intended to be comprehended within 1 and range of equivalents of the disclosed embodiments. It is to be unc the phraseology or terminology employed herein is for the purpose oJ and not of limitation. Therefore, while the embodiments herein described in terms of preferred embodiments, those skilled in 1 recognize that the embodiments herein can be practiced with modific the spirit and scope of the embodiments as described herein.

An embodiment of the nresent invention relates to an annaratus for ar apparatus comprises a furnace (1) having a lid (2) with an opening (3) source (4) located at the bottom surface ofthe furnace(l). The conditio! furnace (1) is maintained analogous to the condition in underground during UCG process. The furnace (1) can be made up of any material withstand high temperatures of upto 1300°C and withstand highlj and/or reducing atmosphere. The material can be selected from stai super alloys etc.

The walls of the furnace (1) is thermally insulated in order to ensu temperature within the furnace (1) is maintained and to minimize the he

The furnace (1) comprises a heat source (4) placed preferably on i surface thereof. This set-up mimics the underground coal gasificatio: The heat source (4) is in the form of a plate or a disc. The heath electrical heating or heating can be carried out using any fuel. The heat is specifically a disc type heating coil with an Inconnel plate at the I source (4).

The apparatus comprises a coal block holder (5) for holding a coal bloi coal block holder (5) has an open- bottom (7) with the coal block (6) heat source (4). The open bottom (7) of the coal block holder (5) facii source (4) ensures that the coal block (6) gets directly heated from t process. The open bottom (7) of the coal block holder (5) has z projections (14) to help in retaining/holding the coal block (6) witl block holder(5). The projections (14) can be flanges or metal strips strip may be a slidable/rotatable metal strip such that the coal block ( within the coal block holder (5) and the metal strip is slid/rotated inwa each other so that the coal block (6) is held/retained within the coal t (5).

The apparatus further has at least one inlet tube (8) for supplying furnace (l).The inlet tube (8) is preferably placed between the heat so open bottom (7) of coal block holder(5). The gas supplied to the fu selected from air, oxygen, nitrogen, carbon dioxide and/or steam deper reaction in the furnace. For e.g. for an analytical study of the spall during the UCG process, air, steam and/or oxygen is passed throuj tubes (8) into the furnace (1). Alternatively, in a study of the pyrol nitrogen can be passed through the inlet tubes (8).

The apparatus further has at least one outlet tube (9) for removing g furnace (l).The outlet tube (9) is placed between the heat source (4 bottom (7) of the coal block holder(5). The outlet tube (9) is used to ^¬ gas from the furnace (1 ). The gas removed is generally the product g after the reactions in the furnace including, but not limited to, combu varying compositions and inert gases like carbon dioxide and ni analysis of the product gas enables the study of the reactions occui underground coal seams during UCG process. The general reactions or processes taking place or occurring in the mm drying, pyrolysis and other chemical reactions. Drying is the evaj moisture present in the coal at high temperature. Pyrolysis is the bn higher hydrocarbon components present in coal at higher temperature char or carbon in solid form and lighter components in gaseous form chemical reactions are combustion, gasification and water gas shift i given below:

C + 0 ₂ ► C0 ₂ , combustion

C + H2O -«- CO + H2, gasification

C + CC-2 * ► 2CO, Boudouard reaction

CO + H ₂ O ^► C0 ₂ + H ₂ , water gas shift reaction

The apparatus also comprises a device (10) for monitoring weight > block (6) at any given point of time. The device (10) is placed outside (1) and comprises a suspension means (1 1) for suspending the coal bio the coal block holder (5) in the furnace (1); wherein the suspension : passes through the opening (3) of the furnace lid (2). The opening (3) ii is packed around the suspension means (1 1) to ensure complete insulati to minimizing heat loss and eas leakaee. The susoension means ( block (6) can be a load cell. The load cell may be attached to a data lc record the weights at different time intervals.

Another embodiment of the invention relates to a process for an characterizing the spalling behavior of coal during underground coal comprising the steps of

a) Placing a coal block (6) within a coal block holder (5); b) suspending the coal block holder (5) with the coal block device (10) for monitoring weight of the coal block (6) ε point of time; wherein the device (10) comprises a suspei (1 1) for suspending the coal block holder (5) with the coal 1 c) placing the device (10) for monitoring weight of the coi outside a ^" furnace (1) such that the suspension means through an opening (3) in lid (2) of the furnace (1) with tfr (6) within the coal block holder (5) suspended from the d& monitoring weight of the coal block (6) and being placec furnace (1);

d) passing a mixture of gases into the furnace (1) through a (8);

e) raising the temperature in the furnace to 700 to 900°C b heat source (4) placed in the furnace (1); and

f) remrdin T weipVit nrnfile nf the rx>al hlnr.k ( £> with resnect ti The gases passed through the inlet tube (8) are selected from ε nitrogen, carbon dioxide and/or steam. The process is continued till change of the coal block is negligible with respect to time. The produ< furnace (1) is continuously removed from the furnace through an out A graph is plotted for the data obtained with regards to the weight of the time. The sudden drops in weight of coal block (6) observed in th< time data are identified as spalling events. Thus, the occurrence of spa] block can be identified from the sudden drops in weight. One such figu infigure2. On accumulating all these sudden weights, the rate of spa] calculated.

The product gas is collected from the outlet tube and can be analyzi Chromatograph (GC) for studying its components and thereby cal calorific value or understanding the reactions occurring in the underj seams. Other equipments like GC-MS, engine or downstream reactors the product gas into other fuels) can also be integrated with our appai analysis or processing of product gas.

The apparatus and the process as defined hereinabove relate to si spalling behavior of coal in the underground coal gasification process the present apparatus can be modified for the study of other processe the UCG. like kinetics, heat and mass transfer ohenomena and/or anv r The apparatus enables the study of feasibility of a particular coe process. Further, it is also possible to characterize and analyze the 1 thermo-mechanical processes for other carbonaceous solid fuel bi slight modifications to the apparatus and the process for use thereof within the scope of the person skilled in the art.

Examples

The following experimental examples are illustrative of the invent limitative of the scope thereof.

A furnace was selected having a plate type heater at the bottom su heating chamber. The dimension of the heating chamber was 380 x mm. The internal openings of the inlet and outlet tubes were made in chamber just above the heating plate. A box type coal block holder m temperature withstanding stainless steel, with its bottom face opened inside the heating chamber. The dimension of the coal block holder wa x 140 mm. The holder was thermally insulated on all its internal f; thickness of 15mm. The coal block was cut into a dimension suitable tc holder. The thermal insulation between the coal block and holder surf the heating of the coal block to happen from the bottom exposed face block. This scenario is analogous to the condition in underground during UCG process. After placing the coal block within the holder, surface 15 mm inward from all its sides. This prevented the coal falling down through the bottom open face of the holder. Then this coal block assembly was suspended from a load cell which was placed furnace, using a stainless steel rod, to monitor the weight of coal suspending rod was passed through the opening in the lid of the furnac taken to prevent the load getting in contact with any solid object to a^ results.

This apparatus generated the weight profile of coal block with time, the UCG like conditions inside the heating chamber, as shown in figun