Pyrolysis Based Sanitary Napkin Incinerator

Pyrolysis based sanitary napkins incinerator Version 3.1

Background :

                              Disposal of used sanitary pad & similar kind of medical waste has been a very common problem. In general the used napkins are thrown to dustbins or flush in to t he drain. The open disposal of soiled pads not recommended due to hygiene issues. Disposal problem is difficult due to use of gel forming polymers used in modern day’s pads. It has also a taboo factor attached to further increasing complicity of disposal. Incineration of medical waste is one of the possible ways to dispose sanitary pads.

Incineration Process –

                 Incineration is a thermal waste treatment process that involves the combustion of organic substances contained in waste materials. Incineration of waste materials converts the waste into ash, flue gas and heat.

Problems with Direct Incineration –

                               The pads are wet during disposal, so during incineration the amount of smoke observed from exhaust/ chimney is too much and the flue gases generated are pollutants. So direct incineration of soiled pads is not a good waste disposal method.

To solve this problem we use pyrolysis process for soiled pad disposal;

Pyrolysis Process –

                     Pyrolysis is the thermal decomposition of materials at elevated temperatures in an inert atmosphere. The products of pyrolysis are combustible gases. So, by complete combustion of those gases the problem in direct incineration can solve.

On the principle of pyrolysis Incinerator is deigned and developed in Vigyan Ashram.

Existing Version –

                      An incineration device has been developed that uses pyrolysis to decompose sanitary napkins into hydrocarbon vapours and combustible gases along with some non-combustible gases and char. These vapours and gases are made to pass over high temperature electric coils (>500⁰C) where they auto-ignite in the presence of oxygen. The heat from the flames partially drives the pyrolysis of remaining sanitary pads. Combustion conditions that result in a transparent flue gas exiting from the chimney.

Limitations with Existing Version –

1. Electrical heating coil is given at below the pyrolysis chamber which is used to burn the gases from pyrolysis, and the heat generated is utilized to heat the pyrolysis chamber. During this process the heating coil get fused due to uncontrolled temperature. 
2. Uneven heating of pyrolysis chamber due to improper location of the heating coil.

Proposed Design –

                    This system will be based on drying & pyrolysis process to decompose sanitary napkins into combustible gases and char. This system will firstly prefer for drying of sanitary pad at 100⁰C-120⁰C temperature. Then pyrolysis process will happen to decompose dried sanitary napkins at 450⁰C-500⁰C temperature, hence generates combustible gases & char. These generated combustible gases also utilize for heating reactor through burner. But initial heating would be done by the electrical heaters. In this system we also go for directly pyrolysis to decompose waste plastic into combustible gases & char.

Design Process

1. Ideation –

In brain storming with DIC Fellows and Dr. Arun Dixit following considerations were finalized –  

1. Capacity of the Incinerator – 1 to 20 pads
2. Weight of dry pad – 7 to 10 gm.
3. Weight of wet pad – 90 % to 93 % of weight of dry pad.
4. Basic Dimensions
5. Operating Temperature Range
6. Heaters
7. Chimney and exhaust system
8. Air Supply for Drying phase
9. Apparatus Cleaning and Handling 

By considering the above points 1st 3D model done as following ;

Model A

Model A: 1st 3D CAD Model (Full View of pyrolysis chamber)

Model A: Section View

• Model A is with SS container (220mm height 180mm dia. And asbestos as a gasket material which is used in IC engines. The upper lead and incinerator male reactor will get attached with each other by nut and bolt arrangement similar to autoclave.
• Model A has ceramic heaters on bottom 1/3rd area of periphery with air blowing in order to push out vapours generated. First drying phase will operate in 110130 degrees.
• The real incineration will happen below pyrolysis chamber same as V1 pyrolysis model (subir sir).

Model B

following points raised in further discussions;

• How much heat will generate by incineration of pyrolysis gases. The weight of polymer is close to 140 grams or 20*7 grams. We guessed the heat generation equivalent to incineration of 140 gm of cotton. This heat is negligible not very substantial hence we decided a trap between heat utilization and ease of manufacturing. The second model be hence proposed with incineration of paralytic gases at the end of chimney.
• Will there be a channelization of air and will air flow accelerate or disaccelerate drying. Knowing the structure of substrate chalking was 100% assure which will result in losses of heat without assisting real dry. Hence it was decided to remove the air blower and suction in model B.

With above considerations 3D modls made as following;

Cross Sectional View of Model B

The following topics also raised during discussions and brainstorming with Mr. Dasnurakar ;

• Possible channelization of hot air.
• Knowing the real life practice and random shape and density of soil pad it was thought that channelization of hot air is almost certain. This will result into loss of hot air without effecting drying.
• On the other hand slow heating through insulated material will lead to less consumption of electricity it was hence decided to remove fan to generate air current. As a result new model proposed it got simplified the next point discuss was incineration of pyrolytic gases.
• . If we incinerate pyloric gases beneath the pyrolysis chamber we will be able to use heat generated.

The cal. To get the saving of electricity by burning of pyrolytic gases is as follows:

• We assume that the calorific value of sanitary napkin pad is equivalent to cotton which in reality will be slit lower. 8gms of cotton per pad will generate 12.8 kcal assuming 1600kcal/kg as calculated value of pure cotton. 2kw heater can generate same amount of energy in 26.7sec. Lead into next consumption of 0.14*10-3 units. Which is equivalent to 1.5paise assuming the unit rate to be 10rupees. That means 75paise saving per batch of 50 pads.
• This was thought to be too low advantage for the capital cost investment. This gave us clear answer that we can incinerate the pyrolytic gas at top of chimney.

2. Material Selection (MOC) –

Following are the options of the materials for the pyrolysis chamber; 

1. Ceramic
2. SS 316L
3. MS (CRCA) sheet

• Inside Chamber Dimensions are, 
  Inner Diameter – 18.2 cm 
  Height – 21.7 cm 
  Perimeter is 58 cm

So it requires 58.0*21.7 cm sheet

For bottom blank 18.6 cm dia. Sheet For top flange Inner Dia. 18.2 cm , Outer Dia. 31.4 cm 
Total sheet required = 4*1 ft.

• Outer Shell 
  Inner Diameter – 26.5 cm 
  Height – 26.3 cm 
  Perimeter – 83.8 cm 
  So, Sheet Size will be 83.8 * 26.3 cm 
  For bottom Blank 27 cm dia. Sheet 
  For top flange Inner Dia. 26.5 cm, Outer Dia. 29 cm 
  Total Sheet required = 5 * 1 ft.
• Lid 
  2 Plates of dia.31.4 
  Sheet Required = 2*1 ft 
  # By considering above dimensions Sheet of around 12 sq. ft. is required. 
  # Thickness of material is 2 mm.

Considering various factors related to heat transfer and thermal cycles during operation of incinerator SS 316 sheet was considered as material of incinerator.

By checking availability and costing of SS 316 it was decided to use MS CRCA sheet of 2 mm thickness for the prototype.

3. Detailed Drawings and CAD Models –

As shown in above conceptual CAD model the assembly is made of three main systems, which ar;

1. Inside Chamber (Pyrolysis Chamber)
2. Outer Shell
3. Lid and chimney

• Inside (Pyrolysis) Chamber

This is the main chamber which will be the air tight vessel with the requirement of avoiding air coming into the chamber which will led to disturbance in pyrolysis process.

1. Inner Shell 

It is cylindrical part made of MS CRCA 2mm thick sheet.

2. Inner Shell Bottom Blank

This part is the bottom for enclosing the inner shell and make it air tight from bottom side.

3. Inner Shell Flange –

This flange has to weld with the cylindrical inner shell and will be covered by gasket from top to make air tight joint between lid surface and inner shell. It has also provision of holders to tight the lid using wing nuts.

4. Wing Nut Mount –

This mount will weld to the inner shell top flange to hold the wing nut.

• Outer Chamber –

1. Outer Shell –

This is MS CRCA 2 mm thickness sheet rolled vessel for holding the complete assembly of inner shell by making gap between both and filled with glass wool to prevent heat transfer to outside surface.

2. Outer Shell Bottom Blank –

This is for enclosing the outer shell from bottom side.

3. Outer Chamber Complete Assembly –

• Lid –

Lid will hold complete pressure building inside the pyrolysis chamber. This will made up of two flat plates joined by round plate and by maintaining gap between the plates filled with glass wool. Also provided handle for handling and wing nut fitting gaps required during locking of the vessel.

1. Lid Round Plate –

2. Lid Top Plate –

3. Lid Wing Nut Mount –

4. Lid Assembly –

• Incinerator Complete Assembly –

Following is the complete CAD assembly of the pyrolysis based sanitary napkin incinerator. It is showing inside pyrolysis chamber, lid and outside chamber.

Fabrication

• CRCA Sheet LASER Cutting –

The MS CRCA Sheets cutting using LASER cutting according to the design and .DXF files of the same. The material cutting work outsource from Ms. Kakade LASER Pune, since the CNC plasma cutting machine in Vigyan Ashram is under maintenance.

• Sheet Rolling –

For making inner pyrolysis chamber and outer chamber cylinderical, rolling machine used and rolling done.

• Welding – 

Welding of the joints after rolling done. Chimney pipe also welded to the inner chamber. Flanges at the top of the inner chamber welded and the chamber is tested for leakage checking by filling water. The chmber is found leakproof.Outer Chamber also Welded after checking the sizes of heaters. Heater Mountings welded to the outer surface of inner chamber.  Lid is fabricated by welding the wing nut mountings and handle. Insulation of Glass wool between two chambers is filled. Gasket is installed on top flange.

The chamber is tested for its leak proof welding by filling water inside and kept for 3 hours. No leakage observed during the test.

• Thermocouple Mounting –

The J-Type Thermocouple is mounted at the bottom Side to sense the temperature inside the chambermand also at the outer surface of inner chamber to sense the inner chamber surface temperature;

• Heaters Mounting –

Heater details:

Heater type – Ceramic IR heaters (Curved type)

Specifications – 122mm*60mm*500 Watt * 240 Volts AC

Heaters are mounted on the 1/3 rd surface considering vertical height of the pyrolysis chamber outer surface.

This heaters mounted using clamp made from MS CRCA 1.5 mm thick sheet. The clamp having u type notches to hold the heaters outer mounting part. The gap between two heaters is filled by glass wool.

The front side surface of the IR ceramic heaters is in direct contact with the outside surface of pyrolysis chamber.

For mounting thermocouple sealant used to seal the minor gap which can be sustain up to 1000 degree Celsius.

• Thermocouple – J type industrial

• Temperature Controller – Selec PTC 513

• Thermocouple and LCD display for Inner Chamber surface temperature –

• Final Assembly –

The final assembly of incinerator is demonstrated in following image. Chimney is attached permanently with leak proof welding to the pyrolysis chamber for carrying the combustible pyrolysis gases out for burning.

By considering calculations of calorific value we can get from the combustion of pyrolysis gases done which we found 10 % that of we required for pyrolysis chamber heating if we burn it beneath the pyrolysis chamber, along with this considering design complications it was finalized to burn the pyrolysis gases at the tail of chimney.

Trials

Trials initiated for testing various parameters.

Idle trial of incinerator taken to understand temperature difference between outer surface or pyrolysis chamber wall and cnter point of the pyrolysis chamber.

Average difference of temperature throughout the trial observed in the range of 200° C to 250° C.

• Trial 1 – Trial on wet cotton

Following are the observations from the trial taken on wet cotton. To make the cotton wet water is added and trial taken.

Trial 1                                    Date – 30/11/2018  Trial on Wet Cotton	Total heaters run time = 10 min. 30 sec.	All next 6 trials heaters run time 229 min. = 3 hrs. 49 min.
Inside Temperature (Degree Celsius)	Surface Temperature	Time	Time (Minutes)	Set Temperature	Heaters Status	Heaters Run time	Comment
28	54	16:45	0	90	On		Drying Started
29	81	16:46	1	90	On		Drying
30	88	16:46	1	90	On		Drying
31	101	16.47	2	90	On		Drying
32	114	16:47	2	90	On		Drying
33	127	16:47	2	90	On		Drying
34	138	16:47	2	90	On		Drying
35	148	16:47	2	90	On		Drying
36	159	16:47	2	90	On		Drying
37	166	16:47	2	90	On		Drying
38	178	16:48	3	90	On		Drying
39	187	16:48	3	90	On		Drying
40	191	16:48	3	90	On		Drying
41	198	16:48	3	90	On		Drying
42	207	16:48	3	90	On		Drying
43	215	16:48	3	90	On		Drying
44	222	16:48	3	90	On		Drying
46	233	16:48	3	90	On		Drying
48	242	16:48	3	90	On		Drying
49	253	16:48	3	90	On		Drying
50	263	16:48	3	90	On		Drying
53	274	16:48	3	90	On		Drying
55	284	16:49	4	90	On		Drying
58	297	16:49	4	90	On		Drying
60	306	16:49	4	90	On		Drying
62	316	16:49	4	90	On		Drying
64	325	16:49	4	90	On		Drying
68	338	16:49	4	90	On		Drying
70	348	16:49	4	90	On		Drying
73	359	16:49	4	90	On		Drying
75	368	16:49	4	90	On		Drying
78	378	16:49	4	90	On		Drying
80	385	16:50	5	90	On		Moist Fumes Started
82	396	16:50	5	90	On		Moist Fumes
85	404	16:50	5	90	On		Moist Fumes
88	411	16:50	5	90	On	16:50 -16:45	Moist Fumes
90	418	16:50	5	90	Off		Moist Fumes
94	430	16:50	5	90	Off		Moist Fumes
95	439	16:50	5	90	Off		Moist Fumes
98	446	16:50	5	90	Off		Moist Fumes
101	451	16:50	5	90	Off		Moist Fumes
104	458	16:50	5	90	Off		Moist Fumes
106	463	16:50	5	90	Off		Moist Fumes
108	469	16:50	5	90	Off		Moist Fumes
111	473	16:51	6	90	Off		Moist Fumes
115	480	16:51	6	90	Off		Moist Fumes
120	486	16:51	6	90	Off		Moist Fumes
122	493	16:51	6	90	Off		Moist Fumes
127	497	16:51	6	90	Off		Moist Fumes
131	501	16:51	6	90	Off		Moist Fumes
132	502	16:51	6	90	Off		Moist Fumes
135	504	16:51	6	90	Off		Moist Fumes
137	506	16:51	6	90	Off		Moist Fumes
140	507	16:51	6	90	Off		Moist Fumes
141	508	16:51	6	90	Off		Moist Fumes
142	509	16:52	7	90	Off		Moist Fumes
145	510	16:52	7	90	Off		Moist Fumes
147	510	16:52	7	90	Off		Moist Fumes
152	510	16:52	7	90	Off		Moist Fumes
155	510	16:52	7	90	Off		Moist Fumes
156	509	16:52	7	90	Off		Moist Fumes
158	509	16:52	7	90	Off		Moist Fumes
160	508	16:53	8	90	Off		Moist Fumes
161	506	16:53	8	90	Off		Moist Fumes
164	506	16:53	8	90	Off		Moist Fumes
166	502	16:53	8	90	Off		Moist Fumes
167	502	16:53	8	90	Off		Moist Fumes
168	499	16:53	8	90	Off		Moist Fumes
169	498	16:53	8	90	Off		Moist Fumes
170	497	16:53	8	90	Off		Moist Fumes
171	494	16:53	8	90	Off		Moist Fumes
172	493	16:54	9	90	Off		Moist Fumes
175	483	16:54	9	90	Off		Moist Fumes
175	481	16:54	9	90	Off		Moist Fumes
177	477	16:54	9	90	Off		Moist Fumes
177	477	16:54	9	90	Off		Moist Fumes
178	475	16:54	9	90	Off		Moist Fumes
178	472	16:54	9	90	Off		Moist Fumes
178	469	16:55	10	90	Off		Moist Fumes
179	465	16:55	10	90	Off		Moist Fumes
180	450	16:56	11	200	On		Moist Fumes
182	452	16:56	11	200	On		Moist Fumes
183	458	16:57	12	200	On		Moist Fumes
184	464	16:57	12	200	On		Moist Fumes
187	475	16:57	12	200	On		Moist Fumes
192	496	16:57	12	200	On		Moist Fumes
194	506	16:57	12	200	On		Moist Fumes
196	514.5	16:57	12	200	On	16:57 – 16:56	Moist Fumes
200	523	16:57	12	200	Off		Moist Fumes
202	531	16:57	12	200	Off		Moist Fumes
204	537	16:57	12	200	Off		Moist Fumes
209	547	16:57	12	200	Off		Moist Fumes
212	553	16:57	12	200	Off		Moist Fumes
214	557	16:57	12	200	Off		Moist Fumes
217	561	16:58	13	200	Off		Moist Fumes
223	569	16:58	13	200	Off		Moist Fumes
225	572	16:59	14	200	Off		Moist Fumes
229	575	16:59	14	200	Off		Moist Fumes
231	577	16:59	14	200	Off		Moist Fumes
238	581	16:59	14	200	Off		Moist Fumes
241	583	16:59	14	200	Off		Moist Fumes
243	583	16:59	14	200	Off		Moist Fumes
245	584	16:59	14	200	Off		Moist Fumes
249	584	17:00	15	200	Off		Moist Fumes Stopped
253	583	17:00	15	200	Off		Dry Gases
254	582	17:00	15	200	Off		Dry Gases
255	582	17:00	15	200	Off		Dry Gases
259	580	17:00	15	200	Off		Dry Gases
260	579	17:00	15	200	Off		Breaking Flame Started
265	578	17:01	16	200	Off
267	568	17:01	16	200	Off
268	566	17:01	16	200	Off
268	564	17:01	16	200	Off
270	555	17:02	17	200	Off
272	545	17:02	17	300	On
274	551	17:03	18	300	On
280	571	17:03	18	300	On
282	580	17:04	19	300	On
288	588	17:04	19	300	On
298	622	17:04	19	300	On	17:04 -17:03
301	633	17:05	20	300	Off
313	653	17:05	20	300	Off
345	672	17:06:00	21	300	Off
361	681	17:07	22	300	Off
366	672	17:07:30	22.3	450	On
370	681	17:08	23	450	On
373	687	17:08:30	23.3	450	On
394	735	17:09	24	450	On
418	777	17:10	25	450	On	17:10 – 17:07:03
440	805	17:10	25	450	On
450	826	17:11	26	450	Off
502	853	17:13	28	450	Off
475	773	17:16	31	450	Off
445	708	17:19	34	450	On
448	736	17:20	35	450	On	17:20 – 17:19
409	618	17:32	37	350	Off
385	563	17:37	42	350	Off		Gases Stopped Coming out

Following is the graph showing the Inside temperature and outside surface temperature of pyrolysis chamber with respect to time.

Trial outcomes-

1. In this trial drying and pyrolysis observed also flame generated at the tail of chimney where orifice of 6 mm diameter installed by using candle as external source to start combustion of the pyrolysis gases.
2. This trial was also performed to understand the temperature ranges and heater performance.
3. The pyrolysis chamber also tested with no leakage found. This trial was aimed at testing the prototype system only.

• Trial 2 – Trial on 3 Dry Pads

Following is the result and observations table along with the comments.

Trial 2      Dry Pads                                                                  Date – 15/12/2018   and  16/12/2018                                 Dry Pads                                                               No. of Pads- 3	Weight of Pads      (With Cover)                             ( Before Incineration)                              1. Sample S1 – 6.30 gms                 2. Sample S2 – 6.30 gms                 3. Sample S3 – 6.30 gms	Weight of Pads (After Incineration) 1. S1 – 1.38 gms         2. S2 – 1.44 gms          3. S3 – 1.38 gms	Total Trial Time – 121 min. Total Heater On Time – 20 min. 30 sec.
Inside Chamber	Surface Temperature	Time	Outer chamber Temperature	Set Temperatures	Heaters Status	Comments	Avg
21	25	11:15	27	250	On		23
23	101	11:16	27	250	On		62
28	166	11:17		250	On		97
37	236	11:18		250	On		136.5
56	336	11:19	28.5	250	On	Gas Started	196
149	551	11:21	30.6	250	On		350
183	592	11:22	30.7	250	On		387.5
213	622	11:22:30		250	On		417.5
260	674	11:23	32	250	Off		467
287	689	11:23:15	32.2	250	Off		488
309	700	11:23:30	32.5	250	Off		504.5
330	706	11:24	32.7	250	Off	Yellowish Red Flame started	518
340	718	11:28	42.3	250	Off		529
302	694	11:34	52	250	Off		498
273	418	11:42	54.8	250	Off		345.5
260	390	11:45	63.1	250	Off	Bluish Flame Burning (Breaking)	325
254	375	11:47		250	Off		314.5
251	370	11:48		250	Off	Gases flow and Flame Contnd.	310.5
249	366	11:49		250	On		307.5
248	365	11:49:30		250	On		306.5
247	372	11:50		250	On		309.5
250	404	11:51		250	Off		327
271	460	11:52		250	Off		365.5
277	445	11:56		250	Off	Gases flow and Flame Breaking          Valve Closed	361
270	424	11:58		250	Off	Valve Opened                                              Slow Gas flow	347
261	396	12:01		250	Off	Gray Color gases Coming                                 ( Breaking Flow)	328.5
253	377	12:04		250	Off	Same as above	315
248	368	12:05		250	On	Same as above	308
252	415	12:06		250	Off	Same as above	333.5
264	451	12:07		250	Off	Same as above	357.5
277	469	12:09		250	Off	Same as above	373
285	455	12:11		250	Off	Same as above	370
272	422	12:15		250	Off	Valve Closed	347
265	405	12:17		250	Off	Valve Opened                                              Breaking Gas flow	335
258	387	12:19		250	Off		322.5
253	375	12:21		250	Off		314
249	366	12:22		250	Off	Increased Gases density	307.5
251	408	12:24		250	Off	Continuos Gas flow with high velocity visual Observations	329.5
280	466	12:26		250	Off	Increased Gases density	373
281	454	12:28		250	Off		367.5
277	437	12:30		250	Off		357
265	401	12:34		250	Off	Blackish gray Gases with breaking Flow	333
256	381	12:37		250	Off		318.5
251	370	12:39		250	Off	Reduced gas flow	310.5
249	366	12:39:45		250	On		307.5
248	371	12:40		250	On		309.5
251	411	12:41		250	Off	Very low dense gas flow with high velocity	331
269	458	12:42		250	Off		363.5
282	460	12:44		250	Off	Increased Gases flow rate and medium dense	371
282	458	12:45		250	Off		370
279	448	12:46		350	On		363.5
288	502	12:47		350	On	Increased gas flow and velocity, more continuos	395
331	609	12:49		350	On		470
371	675	12:50		350	Off		523
413	708	12:51		350	Off	Grayeish white flame burning contin.	560.5
410	685	12:53		350	Off	Valve Closed	547.5
395	646	12:55		350	Off	Valve opened, very slow gas coming	520.5
379	603	12:57		350	Off		491
366	571	12:59		350	Off		468.5
363	564	13:00		450	On	Gases stopped	463.5
469	756	13:13		450	On	Continuos Flame and condensed liquid at chimney	612.5
		13:16			Off		#DIV/0!

Following is the graph of temperatures with respect to time.

Trial Outcomes –

1. The average temperature difference observed of 150 degree Celsius during the trial between pyrolysis chamber surface and center.
2. Pyrolysis temperature range testing is started for dry sanitary pads which will be reference for further trials.
3. Burning of gases and flame observed during the trials.
4. It is confirmed that pyrolysis is happening with the 3 dry pads of weight 18.90 gm.
5. The remaining material as ash is 4.2 gm.
6. Next trial required to perform for checking electricity consumption for complete pyrolysis of dry pads.

• Trial 3 – Trial on 3 dry pads

Trial 3      Dry Pads                                                                 Date – 17/12/2018                                                        Pads – whisper ultra dry                                                                      No. of Pads- 3	Weight of Pads      (With Cover)                             ( Before Incineration)                              1. Sample S1 – 5.71 gm.                 2. Sample S2 – 5.75 gm.                 3. Sample S3 – 5.75 gm.                     Total Weight – 17.21 gm.	Weight of Pads         (After Incineration)         1. S1 – 0.85 gm.                  2. S2 – 0.78 gm.                  3. S3 – 0.77 gm.                  Total Weight – 2.41 gm.	Total Heater Run Time – 14 min. 45 sec.
Inside Chamber	Surface Temperature	Time 1	Time	Set Temperatures	Heaters Status	Comments
23	26	0	13:00	450	On	Valve closed
23	39	0.5	13:00:30	450	On
23	51	1	13:01	450	On
24	68	1.5	13:01:30	450	On
25	98	2	13:02	450	On
28	133	2.5	13:02:30	450	On
35	193	3	13:03	450	On
43	242	3.5	13:03:30	450	On
54	301	4	13:04	450	On	Valve Open , Gas Started coming out
106	458	5	13:05	450	On
170	566	6	13:06	450	On
246	660	7	13:07	450	On	Gases coming slowly
300	722	8	13:08	450	On	Flame Started, Bluish Fame
379	803	9	13:09	450	On	Gases and flame contnd. Without condensation
429	861	10	13:10	450	On
451	880	10.5	13:10:30	450	Off
495	905	11	13:11	450	Off
499	896	12	13:12	450	Off	Gases slow down, flame braking
492	873	13	13:13	450	Off
471	817	14	13:14	450	Off	Breaked gas flow
459	785	15	13:15	450	Off
450	755	16	13:16	450	On	Valve closed
475	780	20	13:20	450	Off	Valve open, flame started, Yellowish green flame, Breaking gas flow
448	709	23	13:23	450	Off
451	739	25	13:25	450	Off	Gas flow slightly increased, flame proppogating
477	764	27	13:27	450	Off	Gases coming slowly, breaked flow, flame starting
455	708	30	13:30	450	Off	Gas slow down
449	695	31	13:31	450	On	Gases very much slow down
		32	13:32	450	No Electricity	Flame burning, slow down gases burning flame
		33	13:33	450	No Electricity
		37	13:37	450	No Electricity
		41	13:41	450	No Electricity	Gases coming very slow,too slow, burning by candle
		47	13:47	450	No Electricity	Very slow and negligible gas flow

Following is the graph of temperatures with respect to time.

Trial Outcomes –

1. Heaters run time found 14 min. 45 sec. that is 1 kw
2. Complete pyrolysis observed in this trial since the ash remained is 1/2 by weight as compared with previous trial.
3. Next trial need to perform for increased no. of pads.

• Trial 4 – Trial on 4 dry pads

Trial 4         Dry Pads                                                               Date – 02/01/2019                                            Dry Pads                                                               No. of Pads- 4	Weight of Pads      (With Cover)                             ( Before Incineration)                              1. Sample S1 – 7.70 gms                 2. Sample S2 – 7.82 gms                 3. Sample S3 – 7.60 gms                 4. Sample S4 – 7.47 gms           Total Weight – 30.59 gms	Weight of Pads         (After Incineration)           Total Weight – 3.97 gms  Percentage residues – 12.9781 %	Total heaters run time = 47 min.
Inside Chamber	Surface Temperature	Time 1	Set Temperatures	Heaters Status	Comments	Heatrs Run Time	Time
30	33	0	450	On			15:45
30	115	3	450	On			15:48
40	243	5	450	On			15:50
70	398	7	450	On			15:52
89	460	9	450	On	Gas satrted		15:54
120	540	10	450	On	Valve closed		15:55
146	570	11	450	On	Valve opened, gas coming, No flame		15:56
190	625	13	450	On			15:58
229	671	15	450	On	Low flame starting		16:00
249	686	16	450	On			16:01
277	718	18	450	On	Flame started, non contn. Gases, valve closed		16:03
316	766	20	450	On	Flame contnd. Without external support		16:05
353	804	22	450	On			16:07
388	834	24	450	On			16:09
422	862	26	450	On	Condensed liquid coming		16:11
433	876	27	450	On		16:12 – 15:45	16:12
448	891	29	450	Off	Flam braking		16:14
453	873	30	450	Off	Gases braking, valve closed		16:15
445	861	31	450	On			16:16
449	868	33	450	Off	Flame contnd.		16:18
456	868	34	450	Off			16:19
442	828	36	450	On	Flame cutting		16:21
446	837	38	450	On	Very low flame, gases		16:23
457	851	39	500	On	Flame contnd.	16:24 – 16:21	16:24
497	889	45	500	Off			16:30
504	884	49	500	Off	Flame braking		16:34
493	867	50	500	On			16:35
505	886	52	550	On			16:37
508	889	55	550	On	Flame contd. Braking after long time, Dark smoke after burning	16:40 – 16:35	16:40
553	951	60	550	Off	Gases and condensed liquid both burning		16:45
546	934	61	600	On			16:46
548	941	63	600	On	Flame trying to sustain		16:48
591	997	72	600	On	Flame cutting	16:57 – 16:46	16:57
		74		Off	Trial Over		16:59

Trial Outcomes –

1. Total heaters run time observed 47 min. is very high as compared with previous trials.
2. Ash content is 12.97 %
3. Further trial required to be perform for wet or soiled sanitary pads.

• Trial 5 – Trial on 4 wet pads

Trial Outcomes –

1. In this trial both drying and pyrolysis observed. Pads made wet with same amount of water by weight.(31 gm. for 30.78 gm. weight of pads)
2. Drying time observed 47 min. while pyrolysis and flame observed for 45 min.
3. Heaters running time was 73 min. and energy consumption 5 kw for 4 wet pads disposal.
4. From this trial we can conclude that INR 12.5 required for disposal of 1 soiled pad which is not economical or viable.
5. Next trial required for increasing capacity and reducing cost per pad of disposal.
6. Average temperature difference is 200 to 250 degree Celsius.
7. After completing the drying process of soiled pads inside temperatures need to have in the range of 450 degree Celsius to 600 degree Celsius for complete pyrolysis.

Trial 6 – Trial on 7 wet pads

Trial 6         Wet Pads                                                               Date – 12/01/2019                                             Wet Pads                                                               No. of Pads- 7	Weight of Pads                                   ( Before Incineration)                              1. Sample S1 – 6.80 gm.                 2. Sample S2 – 6.81 gm.                 3. Sample S3 – 6.52 gm.                 4. Sample S4 – 6.65 gm.                 5. Sample S5 – 6.95 gm.                 6. Sample S6 – 6.68 gm.                   7. Sample S7 – 6.73 gm.           Total Weight of Pads – 47.14 gm.	Weight of Water Added (50 % by weight)                                                                                        1. In S1 – 6.80 gm.               2. In S2 – 6.80 gm.               3. In S3 – 6.50 gm.                4. In S4 – 6.93 gm.            5. In S5 – 6.97 gm.             6. In S6 – 6.88 gm.             7. In S7 – 6.97 gm.      Total Weight Of Water added – 47.85 gm.	Weight After Incineration   – 7.6 gm.		Total Heaters run time = 63 min. 35 sec.
Time	Inside Chamber	Surface Temperature	Time 1	Comments	Set Temperatures	Heaters Status	Comments	Heaters run time		Average
9:45	15	18.5	0		60	On				16.75
9:45:30	15		0.5			On				15
9:46	15	42	1			On				28.5
9:46:30	15	49	1.5			On				32
9:47	15	65	2			On				40
9:47:30	15	88	2.5			On				51.5
9:48	16	119	3			On				67.5
9:48:30	17	146	3.5			On				81.5
9:49	18	174	4			On				96
9:49:30	21	213	4.5			On				117
9:50	23	241	5			On				132
9:50:30	24	272	5.5			On				148
9:51	27	310	6			On				168.5
9:51:30	29	328	6.5			On				178.5
9:52	32	355	7			On				193.5
9:52:30	35	381	7.5			On				208
9:53	38	405	8			On				221.5
9:53:30	42	425	8.5	Gas started		On	Gas started			233.5
9:54	47	446	9			On				246.5
9:54:30	51	468	9.5			On				259.5
9:55	56	490	10			On		9:55 – 9:45	10 min.	273
9:55:30	60	504	10.5			off				282
9:56	64	517	11			off				290.5
9:56:30	69	520	11.5			off				294.5
9:57	73	515	12			off				294
9:58:30	80	460	13.5			off				270
9:59	83	471	14			off				277
9:59:30	84	461	14.5	Gases stopped		off	Gases stopped			272.5
10:01	87	453	16		90	on		10:01 – 10:00	01 min.	270
10:02	90	485	17	Gases coming without moisture		off	Gases coming without moisture			287.5
10:04	98	493	19			off				295.5
10:05	100	473	20			off				286.5
10:07	105	434	22			off				269.5
10:08	107	412	23	No gas, no moisture		off	No gas, no moisture			259.5
10:09	109	392	24			off				250.5
10:11	110	348	26			off				229
10:13	110	329	28			off				219.5
10:20	110	256	35		120	off				183
10:22	109	260	37			on				184.5
10:24	109	349	39			on				229
10:25	110	375	40	Gas coming		on	Gas coming			242.5
10:26	113	440	41			on				276.5
10:27	117	488	42	Gases flow increased		on	Gases flow increased	10:27 – 10:21	06 min.	302.5
10:27:30	120	510	42.5			off				315
10:30	132	510	45	Gases fom chimney mid hole and droplets from downside tip		off	Gases fom chimney mid hole and droplets from downside tip			321
10:32:30	135	459	47.5			off				297
10:35	134	411	50	Moisture and gases seperating(low condensation on glass)		off	Moisture and gases seperating(low condensation on glass)			272.5
10:36:30	134	369	51.5			off				251.5
10:41	132	320	56	low gases and vapor condensation observed		off	low gases and vapor condensation observed			226
10:45	129	284	60		150	on				206.5
10:46	128	276	61			on				202
10:47	128	291	62			on				209.5
10:50	136	456	65	more gases started		on	more gases started	10:50 – 10:45	05 min.	296
10:54	150	553	69			off				351.5
10:58	160	510	73	Chimney tip changed		off	Chimney tip changed			335
11:02	156	264	77			off				210
11:05	157	369	80	no gas, no vapors		off	no gas, no vapors			263
11:07	156	367	82			on				261.5
11:10	158	467	85			on				312.5
11:12	162	502	87	condensed drops coming no gas		on	condensed drops coming no gas	11:12 – 11:06	06 min.	332
11:14	175	510	89	gas without moisture		off	gas without moisture			342.5
11:16	182	543	91			off				362.5
11:18	184	495	93			off				339.5
11:21	183	433	96		200	on				308
11:25:35	192	534	100.5			on		11:25:35 – 11:21	04 min. 35 sec.	363
11:27:30	200	590	102.5			off				395
11:30	215	550	105	no gas, no vapors		off	no gas, no vapors			382.5
11:32	215	525	107			on				370
11:36:30	227	617	111.5			on				422
11:41	258	722	116	gases started		on	gases started			490
11:43	269	745	118	gas flow increased		on	gas flow increased			507
11:45	286	769	120	flame starting, condensation happens and drops at 1st hole observed		on	flame starting, condensation happens and drops at 1st hole observed			527.5
11:52:30	348	837	127.5	Flame short breaking		on	Flame short breaking			592.5
11:56	375	877	131			on				626
12:02:30	405	911	137.5	flame sustaining very long but gases breaking		on	flame sustaining very long but gases breaking			658
12:08	424	916	143			on				670
12:14	448	939	149			on				693.5
12:19	463	962	154			on				712.5
12:26	482	974	161			on				728
12:30	494	987	165			on				740.5
12:33	499	995	168	flame breaking		on	flame breaking	12:33 – 11:31	02 min.	747
12:39	500	979	174			off				739.5
12:40	501	973	175	no condensation	550	on	no condensation			737
12:47	514	1000	182			on				757
12:49	518	1008	184			on				763
12:52	524	1015	187			on				769.5
12:54	527	1020	189			on				773.5
12:59	537	1023	194			on		12:59 – 12:40	19 min.	780
13:06	551	1023	201			off				787
13:08	544	1023	203			on				783.5
13:13	549	1023	208			on				786
13:17	556	1023	212	trial end	500	on	trial end	13:17 – 13:07	10 min.	789.5

Trial Outcomes –

1. Trial on 7 wet or soiled pads using water performed.
2. Trial completed in 3 hour 32 minutes.
3. Heaters running time is 63 minutes which consumed 4 kw. electricity.
4. With loading 7 wet pads energy cost per pad was INR 5.5.
5. This trial is an optimization as compared with previous trial.
6. During the trial condensed grease like liquid noticed at the tail of chimney.
7. T joint was placed at the end of chimney with cotton on bottom side for absorbing condensate while other side of the T-joint was exit of gas and starting of flame.
8. The drying time was around 155 minutes out of 312 minutes during trial.

Brainstorming and analysis of trials data done with Dr. Arun Dixit, Mr. Ameya Kulkarni and team.

Suggestions and modifications received during discussion –

• To make hollow space at the center of inside pyrolysis chamber to reduce drying time by shortening the heat transfer length.
• To limit or specify the capacity of the current prototype to 7 pads disposal at maximum per batch.
• To work on reducing energy consumption per pad for disposal.

Trial 7 – Trial on 7 wet pads

Trial 7         Wet Pads                                                               Date – 19/01/2019                                             Wet Pads                                                               No. of Pads- 07	Weight of Pads                                   ( Before Incineration)                              1. Sample S1 – 6.84 gms                 2. Sample S2 – 7.00 gms                 3. Sample S3 – 6.87 gms                 4. Sample S4 – 6.76 gms                 5. Sample S5 – 6.77 gms                 6. Sample S6 – 6.84 gms                 7. Sample S7 – 6.66 gms           Total Weight of Pads – 47.74 gms	Weight of Water Added                                              (approx. 50 % by weight)                                                                                        1. In S1 – 6.78 gms                                     2. In S2 – 7.38 gms                                     3. In S3 – 7.16 gms                                     4. In S4 – 6.76 gms                                     5. In S5 – 6.80 gms                                     6. In S6 – 6.76 gms                                     7. In S7 – 6.89 gms                               Total Weight Of Water added – 48.53 gms
Time	Inside Chamber Temperature	Surface Temperature	Heaters Run time	Set Temperatures	Heaters Status	Comments
15:10	30	34		60	on
15:12	30	99
15:14	33	200
15:15	36	270
15:16	41	350
15:18	54	453	8 min
15:19	65	507			off
15:21	78	496				very few gases andvapors
15:23	89	443
15:28	99	329
15:31	101	295		120
15:32	101	291			on
15:50	139	365
15:52	138	348
15:53	138	332
15:54	138	327		160
16:00	158	620	28 min		off	gases with moisture
16:05	178	593
16:09	180	490
16:15	172	381
16:20	165	329				gases and vapors stopped
16:23	161	309		180
16:24	160	309			on
16:35	163	424				very low gases coming
16:37	167	574	13 min		off
16:40	198	630
16:45	209	576
16:46	209	542		600
16:47	209	492			on
16:50	209	576
16:52	216	627
16:56	260	766				gases increased
17:00	300	836				flame starting
17:03	325	872
17:07	352	905
17:13	393	958
17:22	442	1006
17:31	470	1023
17:38	462	1023
17:41	461	1023
17:44	455	998				flame breaking
17:47	435	868
17:50	413	764	63 min		heaters fused	Gases stopped completely

• As per discussion wet pads loading cage is modified by placing hollow cylinder at the center made up of wire mesh.
• Trial started on 7 wet pads.
• During trial drying observed for around 80 minutes and gases started coming out without moisture.
• Moisture in gases checked by placing transparent glass in gas flow.

During this trial the IR ceramic heaters run at above maximum permissible temperatures due to which all 8 heaters fused. It was required to run the heaters at higher temperatures since, the temperature difference was 350° C during the 7 pads trial and pyrolysis temperature range achieved from was in between 450° C to 600° C.

• The diagnosis of heaters fusing highlights following reasons

1. Running the heaters at above maximum permissible temperature range.
2. The gap between heater surface and pyrolysis chamber surface.
3. Front facing arrangement of heaters with very low distance in small vicinity.
4. The heaters procurement without datasheet or operating manual, etc.

Please click here to understand the operation of current prototype:

https://drive.google.com/file/d/1l6JsWDL50CpMmCwVdjW2BwBX4j7xKGPh/view?usp=sharing

Bill of Material –

Sr. No.	Description	Material/Details	No. of Units	Material Quantity	Vendor
1	Pyrolysis chamber	MS CRCA sheet 2.5 mm thickness	1	4 sq. feet	Local steel trader
2	Pyro. chamber flange	MS CRCA sheet 2.5 mm thickness	1	4 sq. feet	Local steel trader
3	Pyro. chamber bottom	MS CRCA sheet 2.5 mm thickness	1	2 sq. feet	Local steel trader
4	Outer shell	MS CRCA sheet 2.5 mm thickness	1	5 sq. feet	Local steel trader
5	Outer shell bottom	MS CRCA sheet 2.5 mm thickness	1	2 sq. feet	Local steel trader
6	Lid	MS CRCA sheet 2.5 mm thickness	1	5 sq. feet	Local steel trader
7	Gasket	Compressed Asbestos jointing sheet 3 mm thick	1	3 sq. feet	Mfg. by – Samsonite,Shah Rubber products Bhosari
8	Wing nut and bolts	M6* 4 inch	4	4	–
9	IR Ceramic heaters	Ceramic IR curved type 122mm*60mm*500watt* 240 V AC	8	8	BK Electricals Vashi, Navi Mumbai
10	J type industrial thermometers	J type 100 mm probe 1160 degree Celsius with module	2	2	Bombay Electricals and Engineers Pune
11	Temperature controller	Selec TC513	1	1	Bombay Electricals and Engineers Pune
12	Solid state relay	SSR	1	1	Bombay Electricals and Engineers Pune
13	MCB	2 pole 32A	1	1	Bombay Electricals and Engineers Pune
14	Chimney	MS Pipe – 2 inch dia. * 2 mm thick	1	1 feet	Local steel trader

Pyrolysis based sanitary napkins incinerator Version 3.2

Background –

After performing the trials and heaters burnout or fusing in V3.1, it is decided to design a new prototype considering the results of previous experiments data and understandings.

Key learning from experiments with previous prototype (v3.1)

• With available ceramic IR heaters and design it is difficult to achieve and maintain pyrolysis temperature range of above 450 degree Celsius inside the pyrolysis chamber.
• To maintain 450 degree Celsius inside the pyrolysis chamber heaters required to run by adding 250 degree Celsius temperature difference at chamber outer surface and center.
• In previous prototype (V3.1) indirect heating is used. Heat loss occurs in heating and cooling of pyrolysis chamber material.
• Due to indirect heat transfer cycle time for disposal of soiled pads increases which leads to high energy consumption.

Objectives with current prototype v3.2

• To reduce cycle time required for complete disposal of soiled pads using pyrolysis principle.
• To reduce energy consumption for given batch.

By considering above objectives for designing and developing the prototype the cost requirement of disposal per pad will also reduce.

Concept and Assumptions

• The heat required for heating of pyrolysis chamber with indirect heat transfer to soiled pads will be reduce by placing Ceramic IR heaters inside the pyrolysis chamber.
• Direct heating will reduce the heat loss and cycle time of a batch.
• The operating temperature of heaters will not exceed its maximum permissible temperature range.

Following is the concept sketch with modifications including

• Ceramic IR heaters inside the pyrolysis chamber
• Soiled pads inlet arrangement
• Central exhaust/chimney at the top of incinerator
• Ash removal arrangement with independent bottom platform

Detailed Design

Design Considearations

• Capacity of pyrolysis chamber – 5 soiled pads when bundled
• Material – MS CRCA sheet 2.5 mm thickness
• Split design with 3 assemblies
  • Base assembly – Consist of cage and bottom lid as base which is removable for ash removal.
  • Main chamber assembly – Consist of pyrolysis chamber with internally mounted ceramic IR heaters. Removable outer cover with glass fibre insulation and heater mounting arrangements.
  • Chimney – Consist of pyrolysis gases exaust and flame arrangement. Also having pad loading door. Chimney is also removable and a independent assembly.

• Loading cage volume – 1.871 liters

CAD and detailed drawings

• Base Assembly

Base assembly includes-

1. Base plate

Two base plates are required to make complete base.

2. Base Flange

3. Cage

Cage is based on upper base plate for the purpose of loading pads.

• Main Chamber Assembly

Main chamber assembly is the core of complete incinerator model which includes;

1. Pyrolysis chamber

2. Outer chamber

3. Chamber Flange

4. Main chamber top flange

5. Outer chamber support

• Chimney

Chimney assembly consists of loading door, chimney outlet for pyrolysis gas escape and flame purpose. This assembly is independent which is removable and joint is sealed using gasket.

This includes;

1. Chimney bottom flange

2. Chimney middle flange

3. Chimney top flange

4. Chimney outer support

5. Chimney outer chamber

6. Chimney top

7. Loading point

Manufacturing

• Sheet cutting and cylindrical chambers

Using above design details and CAD models manufacturing of the prototype started. CNC plasma cutting machine and sheet metal rolling used mostly for manufacturing. Arc welding used for joining operations.

2 mm thickness MS CRCA sheet is used.

After cutting rolling operation done for making cylindrical parts like outer chamber, pyrolysis chamber, chimney outer chamber.

By using arc welding joining operations done as per CAD drawings.

• Heater mounting and main chamber assembly

Ceramic IR heaters 2 nos. mounted inside the pyrolysis chamber and the mounting surface is made leak proof using thermal sealant.

The heaters are of 500 watt each. Gap between pyrolysis chamber surface and outer chamber is filled by glass wool as an thermal insulation to avoid heat loss. Outer chamber is removable with purpose of heaters handling and maintenance.

Compressed asbestos jointing sheet gasket is used between two joining surfaces for leak proof joint.

• Chimney assembly with inlet door, chimney and loading cage

This assembly includes inlet door with wing nuts for loading of soiled sanitary pads. Central gas exhaust arrangement in top flange given as chimney where flame can be made for disposing the gases from pyrolysis.

The cage is provided with perforation and open at bottom. Following image shows complete chimney assembly.

• Sanitary napkin incinerator prototype v3.2 complete assembly

Testing and Trials

• Trial 1

Trial 1st is performed as a test run without any pads or materials to check functionality of the prototype.

During this trial maximum temperature of 540 degree Celsius achieved inside the pyrolysis chamber in 35 minutes using two heaters 500 watt each.

With the result of temperature range achieved in test trial next trial on two soiled pads using water scheduled and performed.

• Trial 2

This trial is performed for two sanitary napkins soiled in water with same quantity by weight.

Initially drying of pads started and continued for 35 minutes in the temperature range of 100 degree Celsius to 160 degree Celsius. Temperatures set at 500 degree Celsius when dry gases started coming out of the chimney.

Maximum temperatures achieved of 385 degree Celsius after which temperature range started falling down. Temperatures doesn’t increased for next one hour and trial has stopped.

Diagnosis done for not raising temperature during the trial inside the pyrolysis chamber. Heaters found fused in the chamber.

After this trial it is decided to not use electrical heaters directly inside the pyrolysis chamber.

Conclusion

After performing trials on two versions it is understood that electrical heating for pyrolysis based incineration is costly and not reliable with available heaters for the v3.1 prototype design and v3.2 also.

Material of construction study is required considering optimum heat transfer for pyrolysis.

It is also decided to work on design of a prototype of gas based heating system for incinerator and recirculation of gases from pyrolysis of soiled pads.

The gas fired pyrolysis based sanitary pad incinerator concept sketch is given below.

Following is the link for downloading all DXF files for manufacturing –

https://drive.google.com/drive/folders/1Hp-5KEV8ibqz6Beb8Rt7inU6pmY7P-Bm?usp=sharing