Water Cooled Vibrating Grate Boiler

With growing consciousness on sustainable development and environmental concerns such as climate change focus for energy production world over has shifted towards renewable energy resources. Traditionally, Boilers use fossil fuels to produce steam and electricity to meet industrial requirements, but the need for alternate energy resources was felt. To fulfil this need, the most viable option was renewable energy resources and more specifically bio-mass. In bio-mass, the selected fuel was the paddy straw which is, in essence, a waste by-product of paddy/rice crop that is abundantly grown across India.

CHEEMA BOILERS LIMITED one of India’s Leading Engineering Solutions Company accepted the challenge to design a suitable system to burn this fuel. At first, the following major hurdles were evaluated in using the paddy straw in the Boiler:-

  • Logistics – Paddy straw has a high volume to weight ratio and it is not viable to transport it in actual form.
  • Low ash sintering temperature – It causes slagging and fouling in Boilers and affects Boiler Run Time and life of Boiler parts.
  • High moisture – It affects combustion efficiency. etc.

Paddy straw is, at first, compressed and converted into cubical-shaped blocks/bales at remote locations i.e. in fields for logistics viability and ease of transportation. But, these bales could not be burnt effectively and efficiently in this form. To overcome this challenge, CBL introduced world-class technology and invented a fuel handling system to disintegrate and feed the bales in furnaces and Water Cooled Vibrating Grate (WCVG) for effective burning of fuel.

The WCVG is configured as a fin-type membrane water-wall fitted with air nozzles in the fin area. The primary air is injected through these nozzles with set up of secondary nozzles above the grate to ensure complete combustion. The vibrating grate controlled by an electric motor and eccentric linked driveshaft travel down the fuel crossing four compartments such as feeding zone, heating zone, drying& Burning zone and finally ash zone before falling into a hopper in form of ash.

The boiler is carefully and specifically designed with three pass arrangement and SS 347H grade super-heater to ensure minimum slag deposition and its impact on tubes at higher steam temperature. All other design aspects are widely considered to minimize the fouling of ash in tail auxiliaries without compromising the performance.

Water and air pre-heaters are installed to improve the Boiler efficiency and to minimize the stack losses in terms of heat keeping in consideration the dew point the temperature of gases. At last, ESP/Bag-filters is installed to keep the SPM level within the limit as specified by CPCB.

The heat produces after combustion of fuel can be utilized to generate low, medium or high-pressure steam in Boiler to meet industry goals.

CBL, with prime expertise, overcame all the hurdles during designing, manufacturing and installation and successfully commissioned 1st unit in Punjab and achieved steam to fuel ratio of 3.8with thermal efficiency of 79±1% on 100% Paddy Straw. The composite %LOI/un-burnt is achieved even less than 02% against 05% in other Boilers available in the market.

CBL is leading the way in disruptive energy transition and this innovation is proof of it. It serves the purpose of supplying steam to the industry on required parameters and is environmentally friendly and safe to operate. It has also an outstanding record of availability at the lowest maintenance cost and its power consumption is also low. The anticipated life of grate is more than 10 years.

Scale of operation

Currently this unit has been installed and in commercial use for steam and power production in Punjab and another 02 orders for supply of 100% Paddy Straw & other bio-mass-fired Boilers are under execution in Punjab. Astonishingly, the total paddy straw consumption in all three setups will be 04 Lacs MT annually.

Impact and benefits

  • Paddy straws are in essence waste by-product so it will monetarily be beneficial both for farmers and industry sector.
  • Ash of this fuel contains 50-60 % silica content hence can be utilized in the construction sector and K2O can be used as manure in the fields.
  • Overall reduction in greenhouse gas generation while comparing to fossil fuels. The generation of greenhouse the gas causes an increase in earth temperature and indirectly contributes to ozone layer depletion.
  • The Burning of paddy in the field causes health risk on the local as well as regional-scale due to generation of harmful gases. It has also adverse consequences on the quality of the soil. So, above said practice eliminates the need for burning stubble in the field.

Scalability and adoption of innovation

System can be upgraded and modified up to the capacity of200 TPH, 110 Kg/cm² (g), 540˚Cwith the infrastructure CBL have. Also apart from bales/paddy straws, the furnace is capable of handling all types of biomass fuels (agro-waste and forest waste)having different moisture and ash fusion temperatures.

Shri Davinder Pal Singh Barar, CEO, CHEEMA BOILERS LIMITED

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