Ash pneumatic conveying from existing silo No. 4 to two new silos and ash loading in autocisterns.

Hadziahmetovic, Halima ; Dzaferovic, Ejub

1. INTRODUCTION

This pneumating conveying is consisits of two parts:

* First part is ash pneumatic transport from existing ash silo No.4 in thermal power plant to two new ash silos,

* Second part is ash unloading from two new ash silo and loading into autocisterns.

2. TECHNICAL DATA

* Ash transport capacity is proposed and it is [Q.sub.d] = 160 t/day,

* Required ash transport capacity by one hour is calculated [Q.sub.1] = 160 : 8 (hours) = 20 t/h,

* Equipment capacity for ash transport is Q = 1,15 x [Q.sub.1] = 1,15 x 20 = 23 t/h,

* Pressure vessel conveyor volume is V = 10 [m.sup.3],

* Air compressor capacity for ash transport is [Q.sub.C] = 1720 [m.sup.3] /h, compressor pressure is p = 1,75 bar and electromotor power drive is 90 kW,

* Weighted ratio ash / air [C.sub.m] = 17 [kg.sub.ash] / [kg.sub.air],

* Air compressor set for cleaning bags of silo filters and control air have: Q = 50 [m.sup.3]/h, p = 8 bar, [N.sub.e] = 15 kW,

* Pipeline diameter for pneumatic transport is DN 250 mm,

* Area of filter bags on new silos is A = 35 [m.sup.2],

* Ventilator capacity of filter is Q = 2200 [m.sup.3] /h,

* Ash loading capacity in autocistern is proposed and it's Q= 74 t/h,

* Silo fluidisation blower: Q = 240 [m.sup.3] /h, [DELTA]p = 0,6 bar, [N.sub.e] = 7,5 kW,

* Consumption electricity for ash transport from existing silo No. 4 in thermal power plant to loading in autocistern with heating under new silo is E = 126 kW/h, per 1 ton of ash [E.sub.1]= 126/35 = 3,6 kW/1 ton,

* Total installed power is P = 130 kW.

3. TECHNICAL DESCRIPTION OF ASH PNEUMATIC TRANSPORT

Basic of this technology is from long years of experience and references on similar systems for pneumatic transport with pressure vessel conveyor, like silo similar size.

3.1 System composition

This system consists of:

* Transient element pos. 1,

* Silo manual gate valve pos. 2,

* Transient element pos. 3,

* Compensator pos. 4,

* Inlet ash valve pneumatic operated pos.5,

* Pneumatic dedusting valve pos. 6,

* Pressure vessel conveyor pos. 7,

* Outlet ash valve pneumatic operated pos. 8,

* Ash pipeline pos. 9,

* Two way valve pneumatic operated pos. 10,

* Baffle head pos. 11,

* Steel silo pos. 12,

* Silo filters with ventilators pos. 13,

* Security clopet pos. 14,

* Maximum level indicator pos. 15,

* Continuously silo level measurer type Radar pos. 16,

* Pressure vessel dedusting pipe pos. 17,

* Pneumatic butterfly valves pos. 18,21,24,32,

* Manual butterfly valves pos. 19, 26,

* Manual valves pos. 22, 25,

* Non-return valves pos. 20, 23,

* Steel pipes pos. 27, 28, 29, 34,

* Air cooled low pressure oil--free air compressor pos. 30,

* Pressured air cooler pos. 31,

* Air condensed separator pos. 33.

3.2 System limits

This system of ash pneumatic transport begin under existing manual gate valve at ash outlet from existing silo No. 4 in thermal power plant. The end of this system is two new ash silo in area of thermal power plant, with all silo equipment.

3.3 Work description of pressure vessel conveyor (PVC)

This system of ash pneumatic transport is periodic (Mills et al., 2004).

When is pressure vessel conveyor full of ash his level indicator pos. 7 gives signal for closing inlet of ash valve pos.5. After that valve pos. 6 is closing and valve pos. 21 is opening and waiting to reach requested pressure. After that air valves pos. 18, 19 and 24 are opened and outlet ash valve pos.8 is opened, and ash transport in new silos pos.12 started. When pressure in vessel reached value of 1,1 bar ash conveying is finished, but still about 30 sec. pipeline is washed by air and than closed valves pos. 18, 19, 24 and 8 and cycles is repeated. When PVC is unloaded valve for ash outlet is closed pos. 8 and air valves pos. 18 and 38, and than starts new vessel loading, i.e. starts new cycle of ash conveying (Hadziahmetovic & Sunulahpasic, 2007).

System is shown in Fig.1.

[FIGURE 1 OMITTED]

If pipeline is in blockage than :

* ash outlet valve pos. 8 is closing

* bypass air ventil is opened pos. 38

* transport air ventil is closing pos. 18

* after 60 seconds transport valve pos. 18 and valve pos.38 are opening

* at the end final removal of blockade is doing: closing valves in bypass pos. 38 and 39 and air valves for transport pos. 18 stay opened.

3.4 Compressor pos. 30

Air necessary for pneumatic transport with pressure vessel conveyor gets from compressor pos. 30. At the exit of the compressor air is heated on 270[degrees]C so it's needed to be cooled for pneumatic transport on 100[degrees]C (Mills, 2004).

This air cooling is doing in air or water cooler pos. 31. Cooling air in this cooler does ventilator cooler. Compressor is type: air cooled low presure oil--free air compressor Q = 1720 [m.sup.3]/h; p = 1,75 bar; [N.sub.e] = 90 kW (McGlinchey, 2008).

4. UNLOADING ASH FROM TWO NEW SILOS

Ash from two new silos is unloading in autocisterns, who drives it at storage silos and mixing facilities on Stan Terg mine in Mitrovica (Sasic, 1990).

Ash is going out from silo pos.12 through transient element pos. 44, manual gate valve pos. 45, corner ash discharge valve with pneumatic drive pos.46, ash flow control valve motor operated pos. 47, ash shute pos. 48 and ash loading device for autocistern pos. 49. Ash flow is closing--opening with corner ash discharge valve pos. 46. Ash flow is regulated by ash flow control valve pos. 47. Autocistern is loading with ash by ash loading device pos. 49. Through this device autocistern dedustes and also through dedusting pipe pos. 51.

Fluidisation of cone form bottom is necessary so ash could go out of silo pos. 12. Fluidisation is accomplished with fluidisation of silo bottom panels pos. 35. Air for fluidisation gets from blower pos. 41, Q = 246 [m.sup.3] / h ; Ap = 0,6 bar ; [N.sub.e] = 7,5 kW. Air is brought from blower through pipes pos. 42, 43 and 44 and valves pos. 37, 38, 39 and 40 to fluidisation panels pos. 35 and ash valve pos. 46 and 47. Compressed air for cleaning silo filters pos. 13 and control air for pneumatic valves gets for air compressed agregate pos. 53. This air is condense with filters pos. 54, 55 and 56. Through pipeline pos. 57, valves pos. 58, 59, preparation groups pos. 60, 61, 62, holender coupling pos. 66, 67, 68 and 69, and pipes pos. 70 and 71 air is going to consumer (pneumatic valves and silo filters).

5. CONCLUSION

This pneumatic ash system is reliable. Efficiency of this system is proveded in working of many thermal power plants. This paper contributes to improving the ecological conditions of labor thermal power plants, greater efficiency and less investment in maintenance.

Pneumatic ash system has the following advantages:

* Provide a safe, reliable and efficient system for taking and transport the fly ash.

* Introduction of rationalized and environmentally favorable technology taking, transport and disposal fly ash.

* Introduction of technology and taking the fly ash of transport that do not require constant supervision but casual operators in the course of 24 hours.

* Optimization (decrease) in consumption of electricity.

* Supply of dry fly ash for commercial sale.

This is enabled by applying certain technical achievements to the equipment used for conducting the technological process, and application of modern computer hardware and software solutions, control and governance processes.

6. REFERENCES

Bradley, M.S.A. (1990). Prediction of Pressure Losses in Pneumatic Conveying Pipelines, PhD Thesis, Thames Polytechnic, UK

Hadziahmetovic, H. & Sunulahpasic, R, (2007). Ash pneumatic transport under electrofilters of unit 5 thermal power plant Tuzla, Proceeding of 11th International Research/Expert Conference TMT 2007, ISBN 978-9958617-34-8, pp.1155-1158, Hammamet, Tunisia, September 2007, TMT, Hammamet

Mills, D. (2004). Pneumatic Conveying Design Guide, Second Edition, Butterworth-Heinemann, ISBN: 0750654716, UK

Mills, D.;Jones, M.G., Agarwal, V.K. (2004). Handbook of Pneumatic Conveying Engineering, Crc Press, ISBN: 0824747909, United States

Sasic, M (1990). Calculation of fluid transport and solid material by pipes, pp.199-231, Science book, Belgrade