Vol. 12 Suppl 2 J. CENT. SOUTH UNIV. TECHNOL. Oct. 2005

Article ID: 1005 - 9784(2005)$2 - 0162 - 05

Key technologies of layout design of recycling plants of waste refrigerators

L{) Yi(Pa ~ ) , LIU Z h i - f e n g C ~ J ~ ) , WANG Shu-wang(2E~RltJi), QI Y u n - h u i ( ~ l ~ ) (School of Mechanical and Automobile Engineering, Hefei University of Technology,

Hefei 230009, China)

Abstract: The present situations of waste refrigerators recycling and disposing were analyzed. Three key technolo- gies of layout design of recycling plants of waste refrigerators were presented as follows: 1) establishment of recy- cling process of waste refrigerators; 2) the general plane layout of recycling plants; 3) the detailed layout of work- shops of recycling plants. The focus of the three key technologies is to tackle the problem of the detailed layout of workshops of the recycling plants. By adopting Petri net, the model of logistics system of workshops was estab- lished and then optimized, and finally the detailed layout chart of recycling plants was gained. By adopting E-facto- ry, the recycling plants were simulated. The results show that the method mentioned is effective.

Key words: recycling plant; layout; Petri net; logistics system

CLC number: TH181 Document code: A

1 INTRODUCTION

With the fast step into the 21st century, achieving " Harmony with the Global Environ- ment" has become one of the most urgent challen- ges facing humankind. But as a matter of fact, the waste appliances have badly polluted the environ- ment, and have made the global climate more ab- normal than ever, which has attracted attention of many experts of such fields. Especially in China, the problem is even worse, for at present a large number of appliances are facing elimination accord- ing to the average life span of appliances. There- fore, in order to encourage effective use of re- sources and reduce waste, professional recycling plants should be established so that they can con- tribute to the high efficiency of recycling and solve the awkward problem basically [l-a3.

A Petri net model for integrated process and job shop production planning was introduced by Tamas et al E4J. The material flow of recycling processes for aluminium alloys by means of techni- cal recycling quotas was introduced by Hoberg et al cs3. Yim et al E6D presented a Petri net-based simulation tool for the design and analysis of flexi- ble manufacturing systems. The models for recy- cling electronics end-of-life products was intro- duced by Manbir et al ET~. Considering refrigerators as typical mechatronic products, and according to the advantage and disadvantage of the previous study of references, the key technologies of layout design of recycling plants of the waste refrigerators

were presented so that it can encourage effective use of resources and reduce the wastes, and finally realize sustainable development of society.

2 THREE KEY TECHNOLOGIES

2. 1 Establishment of recycling process of waste refrigerators

It is of first importance to establish recycling process of the waste refrigerators in the whole fa- cilities planning of recycling plants. Therefore, in order to establish recycling plants, based on the survey in some famous appliances enterprises and second-hand markets, and the experiment of prac- tical disassembly of waste refrigerators, some im- portant data and information were obtained so that we can set down facilities planning and design framework of recycling plants, and conclude five typical categories of data, which are as follows: waste appliances products (P ) , quantity (Q) , re- cycling processes ( R ) , related services (S) and time planning (T) . Based on the formal research, the recycling model was established and recycling processes were planned. The general recycling process of waste refrigerators is shown in Fig. lea, 93.

2.2 General plane layout of recycling plants The general plane layout design plays an im-

portant role in the facilities planning and design of recycling plants. In some sense, the general plane

O Foundation item: Project(50375044) supported by the National Natural Science Foundation of China

Received date~ 2005- 07- 15; Accepted date~ 205- 08- 16

Correspondence: LU Yi, Master; Tel.. +86-551-2901351; E-mail: oliverlv@hot, mail. corn

LU Yi, et al: Key technologies of layout design of recycling plants of waste refrigerators • 163 •

t . . O

t ~

Pretreatment

I Washing J

I *t actio c ]

- 5

Separation

Wind force ---£-£-- Magnetic

force ..d_ L -

Whirlpool

Shredding First shred

Second shred ---£-£--- Grinding

Disassembly

[ M a n u a l I

I ,oo,saided I [ Automated ]

. . . . . . . . . . . . . . . . . . . . . . . - I

Motors and compressors ]! i

i

PCB i I

W res li Faceplates

I' Remainders i I

Single-material parts ~ - -

Special-recycling parts: ~._ motors, compressors

Remainder compounds ~ "

Fig. 1 General recycling

layout design is also called the general map of recy- cling plants, which serves the function of making each section of recycling plants in its proper place in the limited place. Its task is not only to fix the position of each workshop of recycling plants, but also to fix the position of each service section and different types of routes of pipes. Furthermore, some necessary spaces should be set aside in order to meet the demand of fire protection, virescence and sustainable development. Therefore, in order to recycle each substance economically and effec- tively in the whole process of disassembly, shred- ding, separation and material recycling, all the fa- cilities should be planned comprehensively, ar- ranged rationally so that it can make all the opera- tions of recycling efficiency, recycling processes management, recycling cost and security in an op- timal state and guarantee the smoothness of steam of people, material flow and information flow. The flow chart of the general plane layout design of re- cycling plants is shown in Fig. 2.

2 . 3 Layout of workshops o f recycl ing plants The detailed layout design of workshops is the

basic element of the general plane layout design, and it is also the core of plants design c~°-~zJ. Gener- ally speaking, the detailed layout design of work- shops can have direct impact on the level and effect of the general plane layout design of recycling plants, therefore, in some sense, detailed layout design of workshops is considered as the core of the three technologies. Usually the principles and guidelines of the general layout design can be suit- able for guiding the detailed design of workshops, only that the design of workshops is deeper, more carefully planned with many particularities.

Classification

Single material

Recycling difficulties

process of waste refrigerators

e -

t¢)

o o

II

Set layout goals

I Set key implementation tasks

1

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E

0 ) ¢.1 O

II ,I

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Fix working area +

°i Fix relations of all sections

I

Institute plane layout design plans I

Analysis of design plans I

Optimal design plan

r "

E

r -

E ~o

O

e~

~Yes

C Accomplishment of layout design

No

Fig. 2 Flow chart of general plane layout design of recycling plants

• 164 • Journal CSUT Vol. 12 Suppl 2 2005

According to the common principle of the general layout design of recycling plants, the layout plan- ning of workshops was fixed up based on analyzing the characteristics, state and processes of work- shops, the structure of waste refrigerators and the recycling methods.

The recycling process of waste refrigerators was operated in a certain limited space, therefore, on the precondition of utilizing space adequately and properly, all the elements of recycling process should be integrated as a whole. In workshops, the setting of each recycling section, auxiliary sec- tion and service section should be optimized, and the organization of recycling lines, workshops planning, scene layout, equipment layout should be rationalized so that the process of recycling can be well performed.

MODELING AND ANALYSIS OF LOGISTICS SYSTEM IN WORKSHOPS OF RECYCLING PLANTS

3.1 Petri net Petri net(PN) is a graphical and mathematical

technique useful for modeling concurrent, asyn- chronous, distributed, parallel, non-deterministic and stochastic systems. PN models can be used to determine both qualitative and quantitative pros- perities. PN has recently emerged as a promising approach for modeling manufacturing systems, and has been used for assembly process planning.

PN consists of four primitive elements (to- kens, places, transitions and arcs), and the rules govern their operation. Graphically, PN is based on a vision of tokens moving around an abstract network. Tokens are conceptual entities, they ap- pear as small solid dots and model the objects that move in the real network. Places are shown as cir- cles and represent the locations where objects await processing or the conditions that the objects are in. Transitions are shown as bars or rectangles and re- present processes, events and activities. Arcs re- present the paths through the system. Arcs con- nect places to transitions and transitions to places. An arrowhead indicates the direction of the path. Arcs have a weight or capacity, indicated by the la- bel on the arc~ it is customary to forego the label when the arc weight is 1. Each transition has some numbers of input and output places. From a mod- eling perspective, these input and output places can represent the pre-conditions and post-condi- tions of an event (i. e. transition), or resources re- quired and released by an event. The primitive ele- ments are shown in Fig. 3 E13-16~.

(S) (a) (b)

D (c) (d)

Fig. 3 Primitive elements of Petri net (a)--Tokem (b)--Place; (c)--Transitiom (d)--Arc

3.2 Time Petri net modeling of workshops logistics system of recycling plants Given the importance of workshops planning

of recycling plants, it is first priority to carry out

research on the modeling and analysis of the logis-

tics system in workshops of recycling plants. Ac-

cording to the study, we can conclude that there is

a certain mapping relationship between the recy-

cling process model and the logistics system in

workshops of recycling plants. Based on the deep

research on recycling process of waste refrigera-

tors, the time Petri net was adopted to model the

logistics system in workshops of recycling plants.

Thus, the time Petri net model was applied to ana- lyze and optimize recycling logistics and to guide

the plants construction and facilities planning. Fig. 4 shows the time Petri net model of disassem-

bly and recycling logistics system in workshops.

This model consists of a disassembly line, a gener-

al recycling line and a printed circuit board(PCB)

recycling line. The meanings of the elements in the

model are listed in Table 1.

The logistics system model, which is based on the time Petri net, can depict each state, transi- tions condition among states and sequence relations among the transitions clearly in the recycling logis- tics system. In addition, the recycling logistics system cannot be self-locked. Therefore, the mod- el presented above is favorable for software simula- tion. From the Petri net modeling and analysis of recycling logistics system, minimizing the time of recycling material flow lines is significantly decis- ive for improving the economic performance of waste refrigerators recycling.

LU Yi, et al: Key technologies of layout design of recycling plants of waste refrigerators • 165 •

P < 57P2

T7 T 8

" ~ P l l Pl2

T9

PI3

Tlo

PI4

Tll

Pls

Ti2

PI6

W 3

P7

L

P8

T5

P9

X6 P10

Fig. 4 Time Petri net model of disassembly and

recycling logistics system in workshops

3.3 Analysis and optimization of logistics system in recycling plants of waste refrigerators

For the purpose of maximizing economic benefits, the inside logistics is stressed on and many steps are taken to optimize the inside logis- tics system, and recycling plants have no excep- tion. It is well known that the inside logistics sys- tem has a direct relationship with recycling proce- sses(see Fig. 1). According to the fact that differ- ent materials of waste refrigerators are transferred among different facilities, the logistics in recycling workshops can be divided into two parts: recycling processes logistics and recycling elements logistics, and the latter is discussed in this paper. On the ba- sis of investigation of plants, the amount of logis- tics of recycling processes is represented by the amount of convey of components after disassembly from one recycling element to another, or to ware- houses. The amount of logistics in the process of shredding and separation is not considered because it is piped directly.

According to the Petri net model presented above and ichnography coding of plants layout, the information table of recycling logistics can be

obtained and shown in Table 2.

Table 1 Meanings of places(P) and transitions(T)

P Meaning Time/ min T Meaning

P1 Waiting for disas- sembly T1 Begin disassembly

Pz Disassembly line is Tz Finish disassembly idle

Begin PCBs shred- Pa Being disassembled 9.8 T3 dins

P4 Components waiting T~ Finish PCBs shred- for shredding ding

Ps CFC and compres- Ts Begin PCBs separa- sors tion

P6 Waste PCBs T~ Finish PCBs separa- tion

Pv PCBs shredding 5.2 Tr Classify

P8 Compounds after Ts Begin first and see- shredding ond shredding

P9 PCBs Separation 4.8 T9 Finish first and sec- ond shredding

Tlo Begin separation

Sending to special Tll Finish separation

T~z Classify

Heavy metal and P~o resin separated

Pn recycling plants

First and second Plz shredding 8. 9

PI3 Compounds after shredding

Pt4 Compounds separa- tion 7.2

Pls Substances separa- ted

Materials entering 11.6 P16 warehouse

Table 2 Recycling information of recycling plants Annual Annual

No. Part name Status Mass/kg recycling logistics amount/t amount/t

1 Compres- Complex 5.40 30.80 17.80 sor

Round 2 Evaporator 2. 10 10.40 10.30 part

3 Lubricant Liquid 1.20 0. 21 2. 90

Inner eara- No fixed 4 pace shape 0.80 0.82 1.30

Accesso- No fixed 5 ries shape 1.40 0.56 0.88

6 Wire Rotundity 0.30 0.24 0.41

7 PCB Rectangle 0.40 0.53 0.24

8 CFC Gas 0.05 0. 12 0.09

Only considering the amount of logistics in the process of disassembly, by means of linear pro- gramming, the formula is given as follows:

• 1 6 6 - Journal CSUT Vol. 12 Suppl 2 2005

u v

Q = M i n ~ ~q,(2~oW,~,~uWc,1 + ¢=I t = I

2ct 2 Wet 2 "-[- ACt3 WCt3 ) ( 1 )

where Y~0, ),c,,, 2c,~ and Ac,3 represent the difficul-

ty coefficient of convey; t represents the working

procedure of materials recycling; c represents the

category of material ; w~0, w~e and w¢,3 represent

the distance between different working procedures

respectively, qi represents recycling material c.

The parameters in the recycling information

table can be put into Eqn. ( 1 ) , some concrete val-

ues can be obtained, finally the facilities planning

of recycling plants can be gained after fur ther anal-

ysis and optimization.

THREE-DIMENSION SIMULATION OF

RECYCLING PLANTS OF WASTE REFRIGERATORS BASED ON E-FACTORY

There are several modules in E-factory: Fac-

toryCad, F a c t o r y P L A N , Fac to ryOPT, Factory-

Flow. In this paper , FactoryCad was adopted to simulate recycling plants of waste refrigerators.

The simulation model primarily consists of two

parts: one is process flow model of recycling

plants , including disassembly and recycling facili-

ties model and materiel conveying model; the other

is three-dimension conformation model , including

workplace of disassembly, opera tors , the stack

and conveying facilities of material.

5 CONCLUSIONS

Three key technologies of layout design of re- cycling plants of the waste refr igerators are put forward, including establ ishment of recycling

process of the waste refr igerators , the general plane layout of recycling plants and the detailed

layout of workshops of recycling plants. Finally,

adopting PN, the logistics sys tem in workshops of

recycling plants is modeled and analyzed.

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(Edited by CHEN Wei-ping)