Wood Pellet Processing

เม็ดไม้เป็นเชื้อเพลิงเม็ดที่พบมากที่สุดและทำจากขี้เลื่อยอัดแน่นและของเสียจากอุตสาหกรรมที่เกี่ยวข้องจากการสีของไม้การผลิต ผลิตภัณฑ์ไม้และเฟอร์นิเจอร์และการก่อสร้าง ในช่วงไม่กี่ปีที่ผ่านมาผู้บริโภคหันไปใช้เม็ดไม้และแหล่งเชื้อเพลิงชีวมวลอื่น ๆ แทนน้ำมัน

การควบคุมความชื้นของเม็ดไม้เป็นหนึ่งในความท้าทายหลักที่ผู้ผลิตเม็ดต้องเผชิญ การทำเชิงรุกด้วยการวัดและควบคุมความชื้นสามารถทำให้ประหยัดต้นทุนได้อย่างมากในกระบวนการผลิตและช่วยลดโอกาสในการบรรจุผลิตภัณฑ์ที่เปียกหรือคุณภาพต่ำ Online Moisture Transmitter ให้การวัดความชื้นอย่างต่อเนื่องและไม่สัมผัสตลอดกระบวนการผลิตสำหรับการควบคุมแบบ close loop ตลอดกระบวนการผลิตเม็ดไม้

Stages of Wood Pellet Production
Sawdust preparation

Moisture levels of incoming sawdust are tested at the pellet plant upon receipt to determine the level of drying necessary before pellet production can begin. The moisture content gives the proportion of evaporable water to the total weight of material. Optimal moisture content of the sawdust is 10-15%. Sawdust with high moisture content should be dried since wet sawdust requires more power to be hammered than dry sawdust, and wet sawdust may impede the screening process by clogging or smearing the screen. Sawdust with lower moisture content, such as sawdust from hardwood flooring plants, can skip the initial drying procedure.

Screening, At large commercial plants, sawdust is screened to remove stones, plastics, metals, or other hard materials that may damage the equipment. Stones and stone-like hard materials are removed by a stone trap when the sawdust passes over the screen while metals are picked up by a magnet. Controlling the moisture content of the sawdust prior to the screening process ensures equipment remains unclogged and that maximum debris is removed before hammering. For smaller plants with less capital, this step is not necessary.

Hammering, Hammering is the next step in the wood pellet manufacturing process prior to the formation of the pellets themselves. In this stage, the incoming raw materials are homogenized to an even-size. In the piles of sawdust there might be wood lumps, dead knots, etc. which need to be hammered so that they can pass the die holes of the sawdust pellet machines.
Pelletizingwood pellet moisture measurement

Next, the sawdust goes into the pelletizing chamber of the sawdust pellet machine where it is heated up to 120-130℃ at high pressure. At this temperature, the lignin naturally present within the sawdust is plasticized and acts as a natural “glue” to bind the particles together to help to form the pellets. The pellets are molded by being pressed through the pellet dies of the sawdust pellet machine and then are cut off by the cutter at the desired length. The quality of the finished pellets is determined in large part to achieving consistent and optimal moisture content of the sawdust prior to pelletizing to ensure the lignin bonds effectively.

Cooling & Packaging

After the pelletizer, the pellets are hot, soft and susceptible to deformation and must be cooled to become rigid. The final wood pellet moisture content after the cooler can be as low as 6% and may increase up to 8-10 % by absorbing moisture from the surround air. A moisture sensor mounted at this stage provides real-time data to optimize the cooling process. At large commercial factories, the pellets undergo one final screening before packaging to separate well-formed pellets from other fine content. Once cooled and screened, the wood pellets are packaged and ready for transport.

เราจะติดตั้งเครื่องวัดความชื้นนี้ที่จุดใดได้บ้างในไลน์ผลิต wood pellet

Moisture is a major consideration throughout the wood pellet manufacturing process to meet finished pellet quality goals and increase profits. Below are some of the locations where our customers have used our sensors to monitor and control moisture in wood pellet production

Incoming sawdust prior to the dryer

The main advantage at this measurement location is to aid the loader operator in balancing the input moisture load to the dryer. Incoming sawdust is generally stored outside where it is subject to the environment, meaning some is wet and some is dry. Large amounts of wet material can overload the dryer. The loader operator needs a large readout at the input hopper so he/she can intelligently select wet or dry material to balance the input moisture.

Output of the dryer

This provides quality control on the dryer output and allows the product to be binned by moisture content.

Output of individual bins
Measurement at this location helps with accurate blending.

Blended product as it enters the pellet press
This critical measuring point monitors sawdust entering the pellet press which must be within a tight moisture range to produce a high quality finished pellet. Instantaneous moisture readings from an in-line moisture meter are helpful to the press operator, and 4-20 mA output can be sent to a PLC which in turn can control the Pellet Press drive parameters in real time.

Laboratory or off line measurement
For grab samples, moisture results can be obtained in 10 seconds with a benchtop moisture analyzer.

Incoming hog fuel
Some pellets plants use hog fuel for the boiler feed. An NIR on-line moisture sensor provides real-time data for improved boiler control. An MCT460-WP non-contact moisture sensor is typically mounted within 6 to 16” of the product looking directly at the sawdust. When needed, the sensor can be mounted on the exterior of a vessel and measure product moisture through a glass window or utilize a snorkel sampler to grab samples when the product flow is light or discontinuous. Depending on the environmental conditions at the plant, air purge and cooling systems are available for installations in exceptionally dusty or hot conditions. The MCT460-WP’s analog outputs are normally connected to the control room allowing plant operators and managers to monitor their process and log historical data.

For quick, accurate and reliable samples testing, the QuikCheck benchtop moisture analyzer can be used in the laboratory for precise moisture measurement of grab samples in under 10 seconds.

Value and Qualitywood pellets

Moisture measurement and control is important in all phases of wood pellet manufacturing. Homes and businesses throughout the world are looking at wood pellet fuel as an alternative or supplementary source for heat. Wood pellets yield high BTU’s at an economical price. Cord wood that you might burn in a fireplace or fire pit generally has moisture from 20 to 60% and is relatively inefficient in energy conversion. Wood pellets, on the other hand, offer high BTU energy yields and are easier to burn, store and transport.