I don't want to crawl simultaneously and get blocked. I would like to send one request per second.
Delays Can we set in 2 says:-
We can specify the delay while running the crawler.
Eg. scrapy crawl sample --set DOWNLOAD_DELAY=3 ( which means 3 seconds delay between two requests)
Or else we can specify Globaly in the settings.py 
DOWNLOAD_DELAY = 3
by default scrapy takes 0.25 seconds delay between 2 requests.
How to give delay between each requests in scrapy?