Editor | On 22, Jul 2002

Case Studies In TRIZ :
FBC(Fluidized Bed Combustion) Boiler’s tube erosion

Jeong-Gil LEE / Project Leader in Utility Plant(LG Chem)
* Seung-Bae LEE / Innovation Support Team(LG Chem)
Jeong-mook OH / TRIZ Consultant in LG-PRC(ojmook@lge.com)

Department of Innovation Support , LG Chemical Ltd. Yeosu plant
70-1, Hwachi-Dong, Yeosu-City, Chunranam-Do, Korea
E-mail: sbleej@lgchem.co.kr
TEL : 82-61-680-1075 FAX : 82-61-680-6005

Abstract

Our Utility Plant at Yeosu Plant have a FBC(Fluidized Bed Combustion)Boiler.

The FBC Boiler, when used in a particular process application, encounters the problem of tube erosion with coal.

By Improving tube erosion and changing its related material, we perfectly solved the problem of FBC Boiler’s tube erosion and achieved the maximum amount of operation days.

Introduction

In 1999, our LG Chem. Yeosu Plant adapted Six Sigma for quality improvement in products, service, and processes which ultimately improved customer satisfaction.

At that time, we also introduced the TRIZ activities (The Theory of Inventive Problem Solving) in order to solve our company’s technological problems.

So far, these innovation activities have consistently been used in our many business fields.

In 2001, we presented our practice in Italy (The 5th IMC User Group Meeting :『 Design a New Foam Separator 』) to demonstrate how we used TRIZ/Tech Optimizer methodology to solve our problem.

Summary of Application of TRIZ

Initial Situation

In the FBC Boiler system, coal is fed into the furnace via the Loop Seal .

Then the coal is combusted and flows into the Hot Cyclone.

Afterwards, this coal called , imperfect combusted coal , is recycled again.

However, erosion is experienced by two factors ;

1. fluidized coal attack upon the surface of the tubes(due to the air feeding)

2. fluidized coal fell down along the surface of tubes

So , we often experience unexpected shut-downs.

<Fig.1 Tube erosion point in FBC Boiler>

Function Modeling

We have done the function modeling to define our real problem by considering various interactions between the tube, coal, and primary air. <Fig. 2>

<Fig.2 Function Modeling>

Problem Definition

We feed the primary air to fluidize into the boiler , but that caused the erosion.

This was the main problem we had to solve according to the project.

Technical Contradiction

The technical contradiction here is ;

If the air speed is increased , this will increase the combustion rate.

However, the erosion of the tube also increases.

When using the contradiction matrix, the following parameters were used ;

<Fig.3 Contradiction Matrix>

The inventive principle can be transformed from contradiction matrix is :

Mechanical Principle replacement : electricity or magnetic field

Intermediary : To induce the medium between tube and fluidized material

Preliminary action : To create preliminary conditions that will prevent the object from harmful factors.

Operation Zone / Time Analysis

Physical Contraction

The physical contraction in this system is ;

<Air speed>has to be fast, because <to increase the combustion rate>

<Air speed>has to be slow, because <to prevent tube erosion>

Separation Rule for space : increase the velocity of the air in Furnace(UZ/T1)

but decrease the velocity of the air (HZ/T2).

Substance-Field Analysis

The Su-F model of the problem ;

The first recommendation by the standard solution set is solved by the introduction of additives(S3) in the existing substance(S1).

And the second recommendation is solved by introducing the foreign third substance or modified substance (S4) between them.

And the third recommendation is solved by introducing a field(F1) which neutralizes the harmful effect.

Concept Generation

We generated several solutions by using TRIZ tool ;

Case 1. It’s proposed to install the protective housing to prevent tube from erosion. <Sub-problem> It’s anticipated secondary problems because of material of housing and installation method.
Case 2. It’s proposed to make the tube surface sticky in order to have coals attached to the surface <Sub-problem> It’s hard to find high temperature(800-950degree)- resistant adhesives.
Case 3. It’s proposed to intake the air to prevent coals falling down the tube surface <Sub-problem> It’s difficult to make air nozzle and the trouble of installation.
Case 4. It’s proposed to install preventive block to prevent coals falling down the tube surface. <Sub-Problem> It’s anticipated the trouble of installation
Case 5. Application It’s proposed to apply the abrasion-resistant coating to prevent the tube erosion, Ex> Mortar

Implementation

We investigated and attempted many cases to apply this concept,

• Choose and Test the coating material which was resistant to erosion
  :Coating material , range , height

• Method (How to spray the coating material onto the tube)

• Other property

As we referred above, we perfectly solved the problem of FBC Boiler’s tube erosion and saved our failure cost.

Conclusion

Since 1999, we solved many problems and gained valuable experience by using TRIZ and Six Sigma activity.

Especially, The creation of a new culture(TRIZ) is indeed very beneficial.

The information collected from the different problem solving tools is later on analyzed and used for other utility plants.

A series of technical concepts resulted from the various results that were produced by the TRIZ application.

As we discussed above, by developing surface processing and its related material, we perfectly solved the problem of FBC Boiler’s tube erosion and developed the maximum amount of the operation days.