A modular, low cost, shallow solar tunnel dryer for grid independent operation has been designed and developed for drying agro and industrial products. The dryer consist of an air-heating unit, drying unit and air diversion unit. The system was designed to operate at a temperature of 50 to 60°C.

After successfully developing and installing solar dryers for drying various Agro products, efforts were extended to study the scope of solar drying for aquatic products like fish. Drying characteristics of fish were studied using the solar tunnel dryer designed and developed at the institute. Thirty Kgs of ‘Bombay Duck’ variety of fish was dried at 45 °C for 11-12 hours. Sample of dried fish was sent to Central Institute of Fisheries Technology, Veraval for chemical, physical and organoleptic analysis.  The quality of the dried fish was much better compared to the open sun dried fish available in the market. With the encouraging results from the initial trials, more experiments are planned to develop a standardized solar drying process for fish drying on commercial scale.

The institute had designed and installed a 100 kg/day rice straw based biomethanation system in the Institute premises during 2003-04. Monitoring of the performance of the system is continuing. The plant consists of six batch type reactors. In each week two reactors were charged with 800 kg of prepared wet rice straw at 35% solids and 400 kg of partially decomposed material removed from a reactor which has completed the process cycle. The partially decomposed material is used as culture.

A batch type biomethanation system to handle 100-kg vegetable market waste (VMW) has been designed and  installed at the institute premises. The plant is charged with mixture consisting of 100 kg VMW, 10 kg rice straw and culture. Water is added to bring solid contents of the mixture at 25%. For initial start up culture from the core of a compost heap was used. Thereafter partially decomposed material removed from the reactor after the termination of a batch was used as culture for the next batch. Under these operating conditions, biogas production in the range of 200-260 l/kg TS was recorded in 40 days of incubation period.

A simple waste management model, which includes waste collection, separation of biodegradables and non-biodegradables and their transport has been developed and used to facilitate data collection. Every day both non-biodegradable and biodegradable waste of 50-60 families is collected in separate containers. Non-biodegradable waste is disposed off through the existing Municipal disposal system. Biodegradable waste (around 20-25 kg) is brought to the Institute and treated in a biogas plant for production of biogas and manure. Biogas production of 230 l/kg TS has been recorded in 30 days of incubation period.

Laboratory models using rice straw & sugarcane trash mixed with digested slurry as substrate with and without FeCl₃ and organic nitrogen supplement were set up and their performance was monitored at 35 ºC. Total solid concentration of the substrates tried in two different sets of experiments was 35% and 25% respectively. Lab scale trials with substrate supplemented with FeCl₃ and organic nitrogen and substrate supplemented with only FeCl₃ at 25% TS produced substantially higher gas (250-300 l/kg TS) in 35 days of incubation period compared to trials without FeCl₃ supplement and higher solid contents. Hence bench scale models were set up using rice straw as substrate supplemented with FeCl₃ and organic nitrogen at 25% TS. Digested slurry was used as culture for the first batch and partially digested material of the batch was used as culture for subsequent batches. Gas production   in the range of 300-385 l/kg TS has been recorded in 35 days of incubation period. Based on the data generated a 40 kg/d pilot plant is being operated using rice straw as substrate supplemented with FeCl₃ and organic nitrogen at 25% TS. Performance of this plant is being monitored.

Laboratory experiments were carried out to develop an efficient thermophilic anaerobic culture for enhancing the thermophilic process of biomethanation of agro-residues at high solid content. The crude culture was enriched with various nutrients to enhance the biogas production.  The enriched culture was incubated at 50 °C for 25 days.  After 25 days of incubation period lab models were set up using rice straw and sugarcane trash as substrate at 50 °C. Total solid content in all the models was maintained at 30 %.  Substrate to culture ratio maintained on dry weight basis was 4:1 was in case of rice straw and 2:1 in case of sugarcane trash. C/N ratio of 28 was maintained in all the models. Biogas produced was in the range of 310-330 litres/kg TS in case of rice straw whereas it was in the range of 250-270 litres/kg TS in case of sugarcane trash. Methane in biogas was 62-65 %.  Performance monitoring of the reactors is in progress.

It is proposed to develop a model for at source segregation, collection, transportation and treatment of domestic waste from a colony, run the model involving a housing colony and evaluate its techno-economic viability.

Four colonies around Vallabh Vidyanagar identified as potential colonies were contacted.   Considering number of houses, income group, present disposal system, willingness of the members and proximity to the Institute Nilkamal Cooperative Housing Colony has been selected. A team of scientists of the Division visited the participating housewives and explained them their responsibilities. Equipment for transportation of waste has been procured. Containers for collection of biodegradable and non- biodegradable have been procured and distributed among the participating members. Bioreactors for treatment of waste have been installed. A simple waste management model, which includes waste collection, separation of biodegradable and non-biodegradable wastes and their transport has been developed and used to facilitate data collection. Every day both non-biodegradable and biodegradable waste of 50-60 families is collected in separate containers. Non-biodegradable waste is disposed off in existing Municipal disposal system. Biodegradable waste (around 20-25 kg) is brought to the Institute and treated in a biogas plant for production of biogas and manure. Biogas production of 230 l/kg TS has been recorded in 30 days of incubation period.

This project was taken up with the objective of developing a reactor, which can gasify loose or powdery biomass directly, without briquetting. In a cyclone reactor, an air + fuel mixture is blown tangentially into the reactor where it is converted in suspension.  It is easy to construct and operate, and has a compact size and a high turndown ratio. A cyclone gasifier of 50 cm. I.D. was designed, fabricated and evaluated at SPRERI. It used a variable rpm rotary valve of capacity up to 100 kg/h  for fuel feeding, and an open vane type blower of 60 m³/h air flow rate. Sawdust and groundnut shell powder upto average feed rates of 26 kg/h were gasified for periods upto four hours continuously. It is planned to test the gasifier at higher feed rates.

In fluidized bed reactors, a bed of an inert material like silica or alumina sand, is kept in a fluid like condition by passing air upwards through it above the minimum fluidisation velocity. Such gasifiers are versatile, and can handle fuels of a wide range of sizes, high ash content and high moisture content. They have a high carbon conversion efficiency and compact volume. A laboratory scale fluidized bed gasifier of 21 cm diameter, for carrying out parametric studies on gasification of sawdust and agro-residues in the range of 10 – 60 kg/h  was designed, fabricated and assembled. It has a screw feeder for injecting the fuel into the bottom of the bed and a regenerative blower for fluidizing the bed and supplying air for gasification of the fuel.

Producer gas from a gasifier has to be cooled to room temperature and cleaned of tar and dust to a level of 150 mg of tar + dust per cu.m. of gas, before it can be used in an I.C. engine. To achieve this, a study of wet packed bed scrubbers was taken up.  The hot, raw gas was fed upward through a bed containing suitable packing material, where it came in contact with tap water, which was fed downwards through a distributor on top.  The water cooled down the gas and also scrubbed the gas free of tar. The dirty water was drained out and removed. After a large number of trials with air and hot producer gas, a configuration was finally arrived at which gave a gas with tar + dust content less than 150 mg/m³ which is the upper limit set by MNES.

A high capacity organic filter  (250Nm³/h capacity)  was designed, developed and evaluated during 2002-2004. A scaled down prototype of this organic filter was designed and developed during 2004-05 to match the gas production rate of a 20 kW gasifier - generator system. Its diameter was 0.65m. The bed depths of coarse and two fine filters were 0.3 m, 0.105m and 0.105m respectively and their packed densities were 165 kg/m³, 209.72 kg/m³ and 209.72 kg/m³ respectively. The filter was designed to clean 50 Nm³/hr producer gas. The unit was tested with  two different types of gasifiers, a 50,000 kcal/h down draft throat type gasifier and a 150,000 kcal/h down draft open core type gasifier. Only a part of the gas from the gasifier was passed through the filter to ensure that the gasflow did not exceed 50 Nm³/h. Three comprehensive tests were conducted on both the gasifiers. During these tests, one coarse bed of wood shavings, two fine beds of saw dust of different grades and a fabric bed were used in the organic filter. In the test set up, the organic filter was put after the spray tower to ensure cold gas to pass through the filter. The organic filter developed at SPRERI has given high gas cleaning efficiency in all trials. The filter waste (wood shavings and saw dust) after some drying can be used as gasifier fuel.

A sand filter was designed and developed at SPRERI for cleaning of 75 Nm³/h of hot producer gas to remove particulate matter from the hot producer gas while retaining tar vapours in the gas and identify the maintenance cycle for the sand filter. The sand filter is of cylindrical shape consisting of two concentric layers of sand columns; the inner column having coarse sand (in the range of 0.5 to 2.0 mm) and the outer one having fine sand (in the range of 0.2 to 0.5 mm) as shown in the figure. The filter was designed for a gas velocity of 0.1 m/s at the coarse sand inlet. As the gas was flowing in the radial direction outwards, the velocity decreased thus improving the cleaning efficiency. To avoid condensation of tar vapours, the sand columns had to be preheated to 250^oC or more. This was done by burning the producer gas from an open core gasifier in a specially designed chamber and passing the hot flue gas through the sand. When the sand temperature was sufficiently high, raw producer gas was directly passed through the filter. The change in colour of fresh coarse and fine sand after 8 hrs of filter operation indicates the deposition of SPM due to filtration.

A naturally aspirated multi cylinder 25 kVA DG set was operated successfully with different fuels and their mixtures. The study revealed that: 

• Blends containing up to 50% de-waxed de-gummed Jatropha oil or Karanj oil with diesel could be used as engine fuel without any adverse effect on engine.

• In general exhaust gas temperature and specific fuel consumption increased with increasing load in all the three fuel modes. However break thermal efficiency decreased. It may be due to lower calorific value of plant oil and producer gas.

• Use of plant oil – diesel mixtures reduced CO, NO and NO₂ and increased HC in the engine exhaust compared to the diesel alone operation. The same trend was observed when producer gas plus diesel or producer gas plus plant oil – diesel blends were used as fuel.

• Maximum replacement of the blend of Jatropha oil and diesel in the   proportion of 1:1 by producer gas was 68%.

Bio-diesel of Jatropha oil was prepared as per the standard procedure and to obtain B25, B50, B75 and B100. These blends were used for studies in  6 kW (7.5 KVA) and 20 kW (25 KVA) Kirloskar diesel engines. The preliminary studies have revealed that the engine output and brake thermal efficiency were reduced with increasing percentage of Bio-diesel, compared to the operation of the same engine on diesel. In general harmful emissions (CO, CO₂, and HC) reduced with increasing percentage of bio-diesel. However NOx emission increased. To reduce the NOx, producer gas was supplied at the air inlet manifold of C I engine. Results were encouraging, NOx percentage reduced drastically, but at the same time CO percentage increased. Detailed studies are in progress.

Regional Test Centre at SPRERI is supported by MNES, New Delhi and approved for testing solar thermal devices by the Bureau of Indian Standards. Standards on flat plate collector were revised in June 2003. The collector test set up has been modified to meet some additional tests of the revised standards.In addition to testing for certification the center offers testing services to the industry to improve the quality of solar thermal devices.

Two biogas plants of modified Janata type developed by Haryana Agricultural University, were installed, one at village Kunjarav and the other at village Bedadha during 2003-04. The socio-economic impact of these plants compared to conventional biogas plant was studied during this year. For the study, a questionnaire was prepared and necessary information was collected from both the beneficiaries.

In both the cases, it is reported that the time required for feeding is around 10 minutes only as cattle dung is to be fed directly. This is much shorter compared to 30 minutes required in case of conventional plant which requires cattle dung to be mixed thoroughly with equal quantity of water to make uniform slurry before feeding the plant. Also, digested slurry handling is simpler as it is less watery. The main advantages of modified plant over conventional are: i) no water requirement, ii) easy feeding, iii) easy handling of digested slurry and iv) time saving.