Smoke Drying Process of Rubber is one of the most important steps in the procedure of converting rubber latex to Ribbed Smoke Sheets (RSS).Usually this step is time consuming and very costly due to the higher labour,space and fuel requirements. Conventionally smoking is carried out in a smoke house, which takes about 4-5days for rubber sheets to reach completely dry. This conventional method encounters many shortcomings that finally affect the profit negatively. Taking those problems into account, a new invention has been made by Dr.Susantha Siriwardhana (Head, raw rubber development and chemical engineering department), A.K.D.Warnajith and Sarath Siriwardhana (Experimental officer in Rubber Research Institute of Sri Lanka) to overcome those problems occur during the process of conventional smoke drying of rubber. Following article is about the new invention made by Dr.Susantha and his team.

Smoke Drying Process of Rubber

During conversion process of rubber latex to Ribbed Smoke Sheets (RSS), smoking process is the last step prior to storing and grading. Smoke drying has three objectives.

Conventionally smoking is carried out in a smoke house, where sheets are hung on the top of the hot smoke that is passed from the bottom. Firewood is used as the conventional source of fuel. However due to the high price and scarcity of firewood, some people use saw dust and rice husk for same purpose. This system takes 4-5 days to reach completely dry. Therefore the capacity of the smoke house should be sufficient to accommodate 5 days programme in order to have and to make sure trouble free smoking process. During 5 days drying period, drying process is actually interrupted significantly for loading and unloading purposes. This operation unit only makes workers working in an uncomfortable smoky area trends yield, heavy energy losses due to the interruption of drying process daily. In addition to this heat loss, generally furnace rooms or the ground floor of the smoke house as a large area yield in unnecessary heat consumption to waste the temperature of this large area. A simultaneous experiment carried out locally has shown that sheet rubber can be dried at 60 0 C instead of drying at a much lower temperature range of 48-54 0 C.

Single day Smoke Drying Unit

Siriwardhana (Experimental officer) in Rubber Research Institute of Sri Lanka. It carries out the smoking operation without interruption to drying process and minimizes heat losses. The drying temperature is also high of 60 0 C.

The dryer dry the sheets in a single day. Therefore this system is called “Single day Smoke Dryer” (SS Dryer) for sheet rubber. This is a Simple modification carried out to continue the process. However it has a significant impact on the drying efficiency as it reduces the dry time by 60-80%. (It takes 4 hours dipping time and 24 hours smoking time)

It has some other advantages too.

•  Sheets can be made to RSS no: 1 quality.

•  Using sawdust and rice husk instead of firewood reduces fuel cost. (Sawdust consumption- 29Kg; frequency of filling sawdust – once in 8 hours)

•  Cleaner convenient, safe, trouble free operation.

•  Less labor requirement.

•  Easy to handle.

•  Fast production cycle.

•  Low construction cost of the unit.

•  Less space requirement.

•  Movability of unit. (Small units are movable)

•  Ash particles do not go to the sheets; because of the filter.

•  Uniform heat distribution.

•  Internal handling is less.

There are few disadvantages:

•  RRI standard quality sheets have to be 500g weight and thickness.

•  Cannot say about the durability. (It has to be investigated in long-term experiments

Experimental trials are conducted at the Ratmalana laboratory premises for this machine. Lab trials have proved the success of this machine. Operation practices have to be established and now the field trials are going on.

The properties of rubber do not change at this high temperature. The knises layer act as an ash filter and gives a uniform heat distribution. Instructions were given to the farmers to produce smoke houses free of charge by this institute.

Market prices of these dryers: -

The dryers, which have the capacity of 100 Kg, 125 Kg and 200 Kg, have to be established in a permanent building.

There is a possibility to develop this dryer by using biogas and solar power as the energy source. If so a farmer whose having a rubber cultivation and a livestock farm can work this dryer by establishing a biogas unit in his farm without spending any cost for fuel.

Prepared by,
Krishani,KT for Kamatha.com
Chathurangi@kamatha.com