Báo cáo khoa học nông nghiệp: Improvement of operator skills and technology in small rural sawmills in Vietnam: Kiln Drying in Vietnam

Ministry of Agriculture & Rural Development Collaboration for Agriculture & Rural Development Project Report 027/06VIE Improvement of operator skills and technology in small rural sawmills in Vietnam. Kiln Drying in Vietnam by Gerry Harris, Peter Vinden and Philip Blackwell October 2009 Project Report 027/06VIE Improvement of operator skills and technology in small rural sawmills in Vietnam. INDEX INDEX....................................................................................................................................................2 PART 1- VIETNAM FACTORY VISITS AND KILN ASSESSMENT..........................................5 Introduction............................................................................................................................................5 Background.............................................................................................................................................5 Summary of results.................................................................................................................................6 Temperature Monitoring & Controls..................................................................................................9 Air Flow.............................................................................................................................................12 Baffling..........................................................................................................................................12 Racking Practises...........................................................................................................................17 Findings.........................................................................................................................................18 Wood fired Boilers............................................................................................................................19 APPENDIX - FACTORY VISIT REPORTS ...................................................................................................21 Factory Visits A - CAXE Environmental & Thermal Engineering Co Ltd ............................................21 Director Mr Bui Anh Viet................................................................................................................21 Factory Visits B - Hoang Thanh Company.........................................................................................23 Factory Visits C - Troung Tai Company..............................................................................................28 Factory Visits D - CHANH HUNG DRYING UNIT.................................................................................30 Factory Visits E - Nong Lam University .............................................................................................37 Factory Visits F - Thien Hung Company Technologies (THC) ............................................................42 THC Factory...................................................................................................................................43 THC Kilns .......................................................................................................................................44 Factory Visits G - Forest Science Institute of Vietnam – Sth. Vietnam Co-Op..................................50 Factory Visits H - Truong Thanh Wood Processing...........................................................................57 PART 2 POTENTIAL FOR SOLAR KILNS IN VIETNAM....................................................65 Introduction......................................................................................................................................65 Background.......................................................................................................................................65 The efficiency of solar drying............................................................................................................68 Climatic Data.....................................................................................................................................70 Calculation Method for Fuel Savings ................................................................................................70 Insolation ......................................................................................................................................71 Kiln types...........................................................................................................................................73 Conclusions.......................................................................................................................................78 REFERENCES..........................................................................................................................................79 Kiln Drying in Vietnam Page 2 of 79 Project Report 027/06VIE Improvement of operator skills and technology in small rural sawmills in Vietnam. SUMMARY AND RECOMMENDATIONS This report is in two parts. Part 1 summarises a number of visits to furniture manufacturers and sawmills where audits were undertaken of the operation of the kilns. The kilns varied in sophistication from being state of the art technology to low cost, low tech, locally built plant. However, without exception improvements could be made to the operation of each kiln that was audited. This report summarises where improvements can be made to each of the kilns visited. This forms the basis of a “Wood drying improvement program” that needs to be implemented. This is an urgent need given that most of the kiln dried material is destined for furniture manufacture. As a general comment most kilns in Vietnam operate as ovens. Whilst the primary objective of reducing the moisture content of timber to below fibre saturation point (28%moisture content) is achieved, there is a high variability in final moisture content. This inevitably results in down-stream problems associated with the quality of joinery or furniture that is manufactured from the timber. Part 2 evaluates the potential for solar kiln drying in Vietnam. There is great potential for solar kiln drying technology in Vietnam for furniture manufacturers and small sawmillers particularly in the HCM City region and Dak Lak Province, where air-drying is prevalent and where final drying of timber to equilibrium moisture content is a requirement of further processing. It is recommended that: 1. A “Wood drying improvement program” is established by the Department of Forestry comprising customised advice and generic training on site at each processing facility where drying is undertaken. Some nominal charge should be made for the provision of this service. It is anticipated that the service would take approximately 1week and could involve 2. Further research is needed to develop drying and processing methodologies specifically for plantation grown acacias for use in furniture production in Vietnam. This could involve the training of a Masters research student jointly in Vietnam and Australia, with the objective of training the person for implementing the “Wood drying improvement program”. 3. The development of new drying technology should focus on: Solar kilns using Australian technology in the first instance, to develop demonstration models for solar drying in Vietnam. This could be followed up by local manufacture. Comparative investigations are needed to determine the best locations for solar drying (using the regression analysis models identified in this report) throughout Vietnam. 4. A model should be developed for the creation of modern drying plants for clusters of small-scale sawmills and/or clustering existing sawmills into larger Kiln Drying in Vietnam Page 3 of 79 Project Report 027/06VIE Improvement of operator skills and technology in small rural sawmills in Vietnam. units to improve processing and drying techniques. Funding is needed to support the building of appropriate kilns. Kiln Drying in Vietnam Page 4 of 79 Project Report 027/06VIE Improvement of operator skills and technology in small rural sawmills in Vietnam. PART 1- VIETNAM FACTORY VISITS AND KILN ASSESSMENT Introduction The CARD Team visited a number of furniture factories located in the Central and South Vietnam, with kiln drying facilities. The facilities at these factories ranged from very basic, small capacity, in-house built kilns to very large capacity modern units. The Team also visited a number of kiln manufactures in order to gain an understanding of the expertise in Vietnam. All kilns assessed by the Team utilised wood waste as the main heat source, either as direct fire units, suppling heat to the kiln chamber via flue gasses ducted through the kiln or as a fuel supply to boilers which inturn supply heat to the kiln via heat exchangers in the form of steam. The Team also inspected the drying facilities at Nong Lam University which had research and commercial drying facilities. These facilities were originally established and designed by Prof. Cac in the 1990’s (see CAXE Section in appendix A for further description). This design appeared to be the basis of many of the kilns assessed by the Team throughout Vietnam. Background The process of timber or ‘lumber’ drying, also know as ‘timber seasoning’ and is the process of removing water from the timber to a target moisture content (TMC) suited to the purpose of use. The moisture content (MC) of timber in service is usually in the range of 8-15%. In freshly felled green logs the wood cell walls and the inside the cell (i.e. lumen) are fully saturated with water. When drying starts the water inside the lumen is lost first, then the water from the cell wall starts to is evaporate (Bootle, 2005). This process will continue (over time) until eventually it reaches a moisture content that is in equilibrium with the surrounding environment. The point at which there is only moisture left in the cell walls is referred to as the ‘fibre saturation point’ (fsp) Timber is dried mainly:  To reduce its weight for the purpose of transport,  To increase strength – dry wood is considerably stronger than green wood,  To produce a product that is stable and durable and  That can be painted / stained and glued and  Can be machined and finished to an acceptable standard (ATSM, 1997). From a commercial perspective this needs to be done as cheaply and efficiently as possible and to achieve this goal the timber needs to dried as fast as possible without too much degrade (Walker, 2006). The purpose of drying timber (from a commercial perspective) is to:  Dry the stack of timber as fast as possible – without excessive degrade Kiln Drying in Vietnam Page 5 of 79 ... - tailieumienphi.vn